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Preamp Tubes For Fender Blues Deluxe Reissue

bluesky636
January 19th, 2011, 02:22 AM
The Blues Deluxe Reissue comes standard with 12AX7s in V1, V2, and V3. I currently have the "Blues" retube kit from Eurotubes which uses a 12AX7 and V1 and V3 and a 12AT7 in V2. It sounds great. I have also heard of people using a 12AX7 in V1 and V2 with a 12AT7 in V3. Then there is the 12AY7 in V1 and 12AX7 in V2 and V3.

I prefer lower gain in the BDRI while getting my overdrive sound from my modded Boss BD-2 and OD-3.

I tried swapping the 12AT7 in V2 with the 12AX7 in V1 in my BDRI and did not like the sound. Although the S/N ratio was better, it sounded too clean to the point of being sterile and brittle so I swapped back.

I have read several recommendations for a 12AT7 for the PI in Hot Rod amps on this and other forums. I believe that is what the BF amps use?

The 12AY7 I was curious about as I believe that was what was used in V1 in the original 57 Twin/59 Bassman.

The tinkerer that I am is interested in trying other tube combinations, but before I drop the bucks on tubes, has anyone else tried different combinations? If so, I am curious about your results. Please share.

BTW: I used the 12Axx designators instead of the proper ECCxx designators that JJ uses because I can never remember which is which. :lol:

marshman
January 19th, 2011, 09:56 AM
12AT7s (and 12AU7s) were not designed as audio amplification tubes, but as drivers, which is what the PI does, so I recommend trying that out. Bear in mind that a couple years ago when I was tube swapping in an Epi Valve Junior, I tried 7 or 8 'preamp' tubes, including RCA and Mullard 12AX7s from the 60s, some current production Sovtek/EHs, as well as other designations (AU/AT7) and liked a used TungSol AU7 the best...UNTIL I got my hands on real NOS 12AY7s, and that was all she wrote.

12AY7 have a bit less than half the gain of a 12AX7, which allows us to turn the amp up louder before the distortion sets in. Mind you, it will still be making the same amount of power, in your case 40ish watts with the MV all the way up, when that happens, but you'll be able to turn the amp up to something like 5 or 6 instead of 2 or 3. Use a pair of them (V1 & V2), and you'll really be able to open things up regarding the knobs...still 40 watts, but what I find is better control over the edge of distortion tones that I like.

Combine all that with variations in bias (not sure if the BDRI has adjustable bias, pretty sure the originals did not) and there are tons of tonal possibilities available.

Yes, most BF amps, to the best of my knowledge, came with 12AT7s as PIs, and usually as reverb drivers, as well.

I also suspect you're right that many of the tweeds came with 12AY7s in V1. I think Leo was processing on the assumption that the lower gain would mean a) lower signal to noise ratio and b) that no one would want to drive the amps into distortion on purpose. Oops.

Good Luck

bluesky636
January 19th, 2011, 09:03 PM
12AT7s (and 12AU7s) were not designed as audio amplification tubes, but as drivers, which is what the PI does, so I recommend trying that out. Bear in mind that a couple years ago when I was tube swapping in an Epi Valve Junior, I tried 7 or 8 'preamp' tubes, including RCA and Mullard 12AX7s from the 60s, some current production Sovtek/EHs, as well as other designations (AU/AT7) and liked a used TungSol AU7 the best...UNTIL I got my hands on real NOS 12AY7s, and that was all she wrote.

12AY7 have a bit less than half the gain of a 12AX7, which allows us to turn the amp up louder before the distortion sets in. Mind you, it will still be making the same amount of power, in your case 40ish watts with the MV all the way up, when that happens, but you'll be able to turn the amp up to something like 5 or 6 instead of 2 or 3. Use a pair of them (V1 & V2), and you'll really be able to open things up regarding the knobs...still 40 watts, but what I find is better control over the edge of distortion tones that I like.

Combine all that with variations in bias (not sure if the BDRI has adjustable bias, pretty sure the originals did not) and there are tons of tonal possibilities available.

Yes, most BF amps, to the best of my knowledge, came with 12AT7s as PIs, and usually as reverb drivers, as well.

I also suspect you're right that many of the tweeds came with 12AY7s in V1. I think Leo was processing on the assumption that the lower gain would mean a) lower signal to noise ratio and b) that no one would want to drive the amps into distortion on purpose. Oops.

Good Luck

Excellent information. Thanks. I might try the AT7 in the PI and an AY7 in V1.

Yes, the BDRI has adjustable bias. I have that dialed in just where I like it. :grin:

MickJaggersTele
April 24th, 2011, 09:56 PM
For my experimentation of preamp tubes in my Blues Deluxe Reissue, I have chiefly relied on the recommendations of Derek Rocco, who is apparently the main guy at Watford Valves, a respected tube outlet in England. He has written about tube rolling using his Hot Rod style, Blues Deluxe Reissue.

Since I would assume, given his position, that he has the ability to widely experiment with tubes in all of the preamp tube positions in these types of amps. I think his recommendations sound great.

Specifically, Derick has written:

I have been using a Blues Deluxe Reissue to evaluate amp and the speaker combinations. The reasons for this is that in November 2007 we will be bringing out an extension cab for this. This I feel is a great amp.

I used a 5751 in V1 and V2 with a balanced harma 7025 in V3. The 6l6 i liked the best was the Philips 6L6WGB, BUT FOR CLEANER SOUND I WOULD USE THE WINGED C SVETLANA 6L6GC."
http://www.watfordvalves.com/cgi-bin/forum/cutecast.pl?session=ZTBX4XBpm0Mp7dwrsPDt6vulMK&forum=2&thread=364

The 7025 that Derick is using in the V3 phase inverter slot is essentially a high quality, high gain 12AX7, similar to a Tung-Sol 12AX7. Derick is also using JAN Philips 5751's in V1 and V2.

I recommend trying two 5751's in V1 and V2 and a 12AX7 in V3, as I find this combination, quiets the amp, provides greater headroom (Bass control moves from 4 to 12, the other control settings may remain the same) and sounds great once you adjust to the change. The 12AX7 in the V3 phase inverter, still gives you some balls.

Maxwell Street
April 24th, 2011, 10:22 PM
MickJaggersTele...Brian says hey...

Davo17
April 24th, 2011, 10:48 PM
Just an idea-it came to me from Bill M the guy who mods the blues junior and it was about the hot rod deluxe-however it may work on your amp as well-a 12DW7 in V2.

The 12DWY is actually half 12u7, and half 12ax7. Makes for some interesting variations. Safe for most amps too.

Colt W. Knight
April 24th, 2011, 10:53 PM
12AT7s (and 12AU7s) were not designed as audio amplification tubes, but as drivers, which is what the PI does, so I recommend trying that out. Bear in mind that a couple years ago when I was tube swapping in an Epi Valve Junior, I tried 7 or 8 'preamp' tubes, including RCA and Mullard 12AX7s from the 60s, some current production Sovtek/EHs, as well as other designations (AU/AT7) and liked a used TungSol AU7 the best...UNTIL I got my hands on real NOS 12AY7s, and that was all she wrote.

12AY7 have a bit less than half the gain of a 12AX7, which allows us to turn the amp up louder before the distortion sets in. Mind you, it will still be making the same amount of power, in your case 40ish watts with the MV all the way up, when that happens, but you'll be able to turn the amp up to something like 5 or 6 instead of 2 or 3. Use a pair of them (V1 & V2), and you'll really be able to open things up regarding the knobs...still 40 watts, but what I find is better control over the edge of distortion tones that I like.

Combine all that with variations in bias (not sure if the BDRI has adjustable bias, pretty sure the originals did not) and there are tons of tonal possibilities available.

Yes, most BF amps, to the best of my knowledge, came with 12AT7s as PIs, and usually as reverb drivers, as well.

I also suspect you're right that many of the tweeds came with 12AY7s in V1. I think Leo was processing on the assumption that the lower gain would mean a) lower signal to noise ratio and b) that no one would want to drive the amps into distortion on purpose. Oops.

Good Luck

I put a set of Tung Sols in my BDRI, and it made that amp come to life!

DOGMA Dunn
April 24th, 2011, 11:55 PM
IMO the best preamp tubes for the reissue are tubes that came with the original blues deluxe when they came out in the mid 90s. Great sounding amp stock back then and even 10 years later. Bias the amp to run hot and it will sound it's best.

MickJaggersTele
April 25th, 2011, 12:15 AM
Just an idea-it came to me from Bill M the guy who mods the blues junior and it was about the hot rod deluxe-however it may work on your amp as well-a 12DW7 in V2.

The 12DWY is actually half 12u7, and half 12ax7. Makes for some interesting variations. Safe for most amps too.

As a word of caution, I would question the use of a 12DW7. As you know, the 12DW7 is an unbalanced tube, as it is half 12AX7 and half 12AU7.

The 12AU7 is 19% of a 12AX7, and is generally not considered interchangeable with an 12AX7. While this tube may not harm your amp, I can't imagine it doing it any good either.

I have never seen any authority on amplifiers, including Hot Rod style amplifiers, recommend the use of a 12DW7 in V1 or V2, and it is absolutely unsuitable as a phase inverter.

Preamp Tube Gain Factors
12AX7=100.......Interchangeable with 12AY7, 12AT7, 5751
5751=70...........Interchangeable with 12AY7, 12AT7, 12AX7
12AT7=60.........Interchangeable with 12AY7, 5751
12AY7=45.........Interchangeable with 12AV7, 12AT7, 5751
12AV7=41.........Interchangeable with 12AY7
12AU7=19.........Interchangeable with 12AV7

While these tubes all have the same 9 pin design, they are not considered to be all completely interchangeable.

I just discussed this on another thread where a guy had a 12DW7 in V2, which would be the gain channel preamp tube in these amps.

He reported that "the bass and mid knobs are pretty interactive - turn up the bass, you add mids, turn up the mids you add bass."

http://www.tdpri.com/forum/amp-central-station/194601-i-never-realized-how-bad-my-blues-deluxe-reissue-sounded.html#post3259247

Gee, I wonder why???

MickJaggersTele
April 25th, 2011, 12:20 AM
MickJaggersTele...Brian says hey...

What's up Brian?
How are those swimming lessons going??

Davo17
April 25th, 2011, 12:28 AM
As a word of caution, I would question the use of a 12DW7. As you know, the 12DW7 is unbalanced tube, as it is half 12AX7 and half 12AU7.

The 12AU7 is 19% of a 12AX7, and is generally not considered interchangeable with an 12AX7. While this tube may not harm your amp, I can't imagine it doing it any good either.

I have never seen any authority on amplifiers, including Hot Rod style amplifiers, recommend the use of a 12DW7 in V1 or V2, and it is absolutely unsuitable as a phase inverter.

Preamp Tube Gain Factors
12AX7=100.......Interchangeable with 12AY7, 12AT7, 5751
5751=70...........Interchangeable with 12AY7, 12AT7, 12AX7
12AT7=60.........Interchangeable with 12AY7, 5751
12AY7=45.........Interchangeable with 12AV7, 12AT7, 5751
12AV7=41.........Interchangeable with 12AY7
12AU7=19.........Interchangeable with 12AV7

I just discussed this on another thread where a guy had a 12DW7 in V2, which would be the gain channel preamp tube in these amps.

He reported that "the bass and mid knobs are pretty interactive - turn up the bass, you add mids, turn up the mids you add bass."

http://www.tdpri.com/forum/amp-central-station/194601-i-never-realized-how-bad-my-blues-deluxe-reissue-sounded.html#post3259247

Gee, I wonder why???

Theres nothing to be cautious of here...the tube is simply a combination of other tubes which are also safe in this amp. I contacted Bill M and he advised me of this "trick"-which I tried and am thrilled that I did.

In the HRD the drive channel is influenced by V1 and the second half of V2 and it makes for an improved drive channel, without a change to the great cleans of the amp. It makes the drive into a great bluesy drive on the HRD. The Blues deluxe is a similar design and may also benefit-I believe the preamp is quite similar, and NOS 12 dw7s are pretty affordable. This amp is an exception to the "in general" qualifier you used.

Your quote on the mids and bass in HR amps are true in any stock amp-its the way the HRD tonestack comes stock, not because of a preamp tube.

And in the phase splitter slot there you are right-its quite unbalanced but that may be a good thing to some-in fact many harp players run a 12dw7 because it gives a very raw sound to the amps they crank.

The op asked for interesting preamp tube ideas-this is certainly one.

MickJaggersTele
April 25th, 2011, 01:29 AM
Theres nothing to be cautious of here...the tube is simply a combination of other tubes which are also safe in this amp. I contacted Bill M and he advised me of this "trick"-which I tried and am thrilled that I did.

In the HRD the drive channel is influenced by V1 and the second half of V2 and it makes for an improved drive channel, without a change to the great cleans of the amp. It makes the drive into a great bluesy drive on the HRD. The Blues deluxe is a similar design and may also benefit-I believe the preamp is quite similar, and NOS 12 dw7s are pretty affordable. This amp is an exception to the "in general" qualifier you used.

Your quote on the mids and bass in HR amps are true in any stock amp-its the way the HRD tonestack comes stock, not because of a preamp tube.

And in the phase splitter slot there you are right-its quite unbalanced but that may be a good thing to some-in fact many harp players run a 12dw7 because it gives a very raw sound to the amps they crank.

The op asked for interesting preamp tube ideas-this is certainly one.
To each is own.

I don't know who Bill M. is, but I've never seen anyone that I would consider an expert on amps recommend the use of a 12DW7 in any preamp slot, in any amp, but apparently the idea is for some unknown reason, generating a buzz on these threads.

With all of the other choices for preamp tubes, I don't understand why anyone would want to use a completely unbalanced preamp tube.

Go on the Tubestore page for the 12DW7 and you will not find any recommendation that these tubes are a substitute for a 12AX7. And I've never seen any authoritative source that suggests that either.

If you can direct me to any authoritative source which states that the 12DW7 is an acceptable substitute for a 12AX7, I would love to take a look at it.

MickJaggersTele
April 25th, 2011, 02:03 AM
Here's what the Tubedepot says about the 12DW7:

This is a suitable replacement for any 12DW7 / ECC832. One side has a gain factor of 100 - the other side has a gain factor of 20. You can think of it as 1/2 a 12AU7 and 1/2 a 12AX7. Try this tube for some interesting gain reduction effects on certain amps.
http://www.tubedepot.com/jj-ecc832.html

Like the TubeStore, the TubeDepot offers no recommendation that a 12DW7 is a 12AX7 substitute.

Davo17
April 25th, 2011, 10:48 AM
There are legit reasons for wanting to tinker with this amp. Im simply making the op aware of a cheap, reversible mod that may take his drive side from something hes not happy with to something that he may like-even if tubestore didnt mention it.:grin:
Here's what the Tubedepot says about the 12DW7:


http://www.tubedepot.com/jj-ecc832.html

Like the TubeStore, the TubeDepot offers no recommendation that a 12DW7 is a 12AX7 substitute.

Maxwell Street
April 25th, 2011, 03:42 PM
What's up Brian?
How are those swimming lessons going??

Don't swim here...rest assured I've been watching over everything for years...keeping everthing in tune. 5751...?

MickJaggersTele
April 26th, 2011, 02:21 AM
Don't swim here...rest assured I've been watching over everything for years...keeping everthing in tune. 5751...?

5751's in V1 and V2!!!

bluesky636
April 26th, 2011, 01:36 PM
Wow! Just realized I haven't been back to this thread since January. Here is the final tube configuration I settled on:

V1 - Phillips/JAN 5751
V2 - JJ 12AX7
V3 - JJ 12AT7
V4/5 - JJ 6L6GC

Bias is set to 38 mA cathode current/approx 36 mA plate current with a plate voltage of 413 VDC. Well broken in stock Fender/Eminence speaker.

I plug my SCN equipped Strat into input #1 and use the clean channel. I plug my two humbucker equipped guitars into input #2 and use the drive channel as a second clean channel with the levels matched to the clean channel. The amp sounds sweet as honey and the signal to noise ratio is greatly improved. I use a Fulltone Full Drive 2 MOSFET for dirt with all three guitars. The FD2M is my only pedal (besides a Boss TU-3) and is all I need to play the Blues. :grin:

MickJaggersTele
April 26th, 2011, 04:02 PM
Wow! Just realized I haven't been back to this thread since January. Here is the final tube configuration I settled on:

V1 - Phillips/JAN 5751
V2 - JJ 12AX7
V3 - JJ 12AT7
V4/5 - JJ 6L6GC

Bias is set to 38 mA cathode current/approx 36 mA plate current with a plate voltage of 413 VDC. Well broken in stock Fender/Eminence speaker.

I plug my SCN equipped Strat into input #1 and use the clean channel. I plug my two humbucker equipped guitars into input #2 and use the drive channel as a second clean channel with the levels matched to the clean channel. The amp sounds sweet as honey and the signal to noise ratio is greatly improved. I use a Fulltone Full Drive 2 MOSFET for dirt with all three guitars. The FD2M is my only pedal (besides a Boss TU-3) and is all I need to play the Blues. :grin:
That should work!!

I'm very happy with my sound with Jan Phillips 5751s in V1 and V2 and a Tung-Sol 12AX7 in V3.
I also use Fender SCN pickups in my 3 Teles and a Strat (I like the Tele pickups even better than the Strat).
The amp is so completely quiet, with no hiss or hum, that you don't know that the amp is even on if you are not playing.

I recently ordered a 12AT7 to try in V3, after posting in some of these BDRI threads on preamp tubes, just to experiment.
I have the feeling that this might be too much of a gain reduction without going to a 12AX7 in V2, as you have done.

Either one of these preamp combos are probably the ticket for this amp!!:mrgreen:
Glad to see that you stayed away from that 12DW7 nonsense.

bluesky636
April 26th, 2011, 06:17 PM
That should work!!

Should work? Hell, it works great :!::!::!: :grin:

Davo17
April 26th, 2011, 09:24 PM
Glad to see that you stayed away from that 12DW7 nonsense.

Glad to see that even with an explaination of this particular pre-amp that you couldnt grasp how a 12dw7 would work. Perhaps one day tubestore will write an article about it.:roll:

MickJaggersTele
April 26th, 2011, 11:25 PM
Glad to see that even with an explaination of this particular pre-amp that you couldn't grasp how a 12dw7 would work. Perhaps one day tubestore will write an article about it.:roll:
The only source that I have found that suggests the use of 12DW7 tubes to lower the gain in Fender amps is Eurotubes, who probably bought a ton of these "junk tubes" for a dime a dozen and are trying to sell them for a healthy profit to non-Ampeg amp owners.

The BDRI, like the Blues Junior, according to Bill M: "...has five tubes, V1 through V5, numbered right to left as you look at the back of the amp. V1 is the preamplifier. It has the most effect on tone. V2 re-amplifies or recovers the signal lost in the tone stack. Only half of V2 is used unless you have the cathode follower mod (as advocated by Bill Machrone). It has a relatively minor effect on tone. V3 is the phase inverter. It makes mirror images of the signal and drives the output tubes, V4 and V5. It too is an amplification stage, and has a minor effect on tone. V4 and V5 are the output tubes."

http://billmaudio.com/wp/?page_id=131

In using a 12DW7 in V2, only the 100mu side of the tube is basically used, unless you have Bill M's cathode follower mod. So what is the point? Any gain reduction that you are getting is basically because the 100mu side of this tube isn't actually putting out 100mu. The 20mu side of the tube isn't used, absent the cathode follower mod. There are much better ways to lower gain in this amp than using a 12DW7, such as using the type of "balanced" preamp tubes that this amp was designed to use, which provide a basic reference to the amount of gain that you can expect.

Even in his article on preamp tubes linked above, Bill M never suggests the use of the 12DW7 in V2, and only mentions that: "Harp (harmonica) players may get a kick out of using a 12DW7, also known as an ECC832, in V3. This is a hybrid tube that has the gain of a 12AX7 on one side and the gain of a 12AU7 on the other.

(In V3) It drives the output tubes unequally, which causes distortion pretty much all the time. This can be good for harp, because you generally want to drive the amp into distortion to get your blues tone, but donít want to play loud enough to cause feedback into the microphone."

http://billmaudio.com/wp/?page_id=131

Now that I have explained how this particular preamp works, maybe you can grasp how a 12DW7 would work in these amps and why these are "Junk Tubes" that no one should want in V2.

Now there is no need for the tubestore to write an article about these "Junk Tubes.":rolleyes:

bluesky636
April 26th, 2011, 11:52 PM
I wouldn't waste my time with a 12DW7. :wink:

MickJaggersTele
April 27th, 2011, 12:31 AM
I wouldn't waste my time with a 12DW7. :wink:

http://www.comicbookmovie.com/images/users/uploads/10959/applauseb.gif

BobbyZ
April 27th, 2011, 12:49 AM
The 12DW7 debate !
Now I'm thinking it may have some use in an amp that splits the first tube (one side for each channel). Would give you a low and high gain channel.
If I have a 12DW7 maybe I'll try it tomorow. If I don't have one I'm not buying one.

Davo17
April 28th, 2011, 11:45 AM
The only source that I have found that suggests the use of 12DW7 tubes to lower the gain in Fender amps is Eurotubes, who probably bought a ton of these "junk tubes" for a dime a dozen and are trying to sell them for a healthy profit to non-Ampeg amp owners.
First off the 12DW7 was/is made by several manufacturers, ranging from nos to new production. Im not trying to sell tubes.:roll:
The BDRI, like the Blues Junior, according to Bill M:

http://billmaudio.com/wp/?page_id=131

In using a 12DW7 in V2, only the 100mu side of the tube is basically used, unless you have Bill M's cathode follower mod. So what is the point? Any gain reduction that you are getting is basically because the 100mu side of this tube isn't actually putting out 100mu. The 20mu side of the tube isn't used, absent the cathode follower mod. There are much better ways to lower gain in this amp than using a 12DW7, such as using the type of "balanced" preamp tubes that this amp was designed to use, which provide a basic reference to the amount of gain that you can expect.

Even in his article on preamp tubes linked above, Bill M never suggests the use of the 12DW7 in V2, and only mentions that:

http://billmaudio.com/wp/?page_id=131
Pssst....hes talking about A DIFFERENT AMP, with a different preamp design. Getting back to the blues deluxe(which shares much of the preamp of the hot rod deluxe) The way the preamp is designed the one half of V2's dual triode ONLY works on the gain side, the other works on the clean side. Its because of this feature that a 12DW7 becomes useful. Many people find the stock OD to be buzzy and thin. The 12AU7 allows you to lower the drives gain, and darken the tone up while retaining the great cleans this amp has.
Now that I have explained how this particular preamp works, maybe you can grasp how a 12DW7 would work in these amps and why these are "Junk Tubes" that no one should want in V2.

Now there is no need for the tubestore to write an article about these "Junk Tubes.":rolleyes:
See my above explaination. I didnt make the 12DW7 or the blues deluxe-but I did get clued into the benefits of that tube in these amps and from a respected fender amp tech/modder no less.
Its interesting that you are capable of distinguishing between a 12ax7 and a 12au7, but dont see the value of pre tube that takes one triode from each type. Its also interesting that you dont know how the tone stack works on these amps-where mids are dependant on bass settings etc. The 12DW7 allows those who like the drive tones of lower gain tubes, but want to retain the great stock cleans of 12ax7s to have both. Thats an awesome option, and it works with this series due to the preamp design.

So here we have a fairly cheap and non-permanent mod that MAY make the biggest downside of Fenders new amps (the drive channel) into something thats usable and you poo poo it. Way cool man.:roll:

Davo17
April 28th, 2011, 11:51 AM
The 12DW7 debate !
Now I'm thinking it may have some use in an amp that splits the first tube (one side for each channel). Would give you a low and high gain channel.
If I have a 12DW7 maybe I'll try it tomorow. If I don't have one I'm not buying one.

Sounds like an interesting experiment. Let us know what you find.

BobbyZ
April 28th, 2011, 12:30 PM
Sounds like an interesting experiment. Let us know what you find.

Yes it would have been. But turns out I had a 12av7 and not 12aw7. So the experiment didn't take place.
Would be fun to try though.
EDIT 12DW7

bluesky636
April 28th, 2011, 03:31 PM
Pssst....hes talking about A DIFFERENT AMP, with a different preamp design. Getting back to the blues deluxe(which shares much of the preamp of the hot rod deluxe) The way the preamp is designed the one half of V2's dual triode ONLY works on the gain side, the other works on the clean side. Its because of this feature that a 12DW7 becomes useful. Many people find the stock OD to be buzzy and thin. The 12AU7 allows you to lower the drives gain, and darken the tone up while retaining the great cleans this amp has.

You're dead wrong on this. In the Blues Deluxe/Deville (original and Reissue), only 1/2 of V2 is used. Period. And that is for tone stack gain recovery. The second half of V2 is not used at all. Only the Hot Rod Deluxe/Deville use the second half of V2. And the preamps of the Blues series are very different from the Hot Rods. Take a look at the schematics:

http://www.blueguitar.org/new/schem/fender/blues_deluxe-deville_reissue.pdf

http://support.fender.com/schematics/guitar_amplifiers/Blues_Deluxe_schematic.pdf

http://support.fender.com/schematics/guitar_amplifiers/Blues_DeVille_schematic.pdf

http://support.fender.com/schematics/guitar_amplifiers/Hot_Rod_Deluxe_schematic.pdf

http://support.fender.com/schematics/guitar_amplifiers/Hot_Rod_DeVille_schematic.pdf

Davo17
April 28th, 2011, 05:09 PM
You're dead wrong on this. In the Blues Deluxe/Deville (original and Reissue), only 1/2 of V2 is used. Period. And that is for tone stack gain recovery. The second half of V2 is not used at all. Only the Hot Rod Deluxe/Deville use the second half of V2. And the preamps of the Blues series are very different from the Hot Rods. Take a look at the schematics:


Bluesky you are correct- only one side of V2 is used in the blues deluxe series, its the hot rod series that uses both halves. I knew the hot rod series was very similar but not identical.

http://www.justinholton.com/hotrod/faq.html#otheramps

bluesky636
April 28th, 2011, 05:20 PM
Bluesky you are correct- only one side of V2 is used in the blues deluxe series, its the hot rod series that uses both halves. I knew the hot rod series was very similar but not identical.

http://www.justinholton.com/hotrod/faq.html#otheramps

Its Ok. I've put a lot of time studying the BDRI and how to improve its sound. I noted my final tube selection earlier and it sounds great. :grin:

Davo17
April 28th, 2011, 10:39 PM
Its Ok. I've put a lot of time studying the BDRI and how to improve its sound. I noted my final tube selection earlier and it sounds great. :grin:

Cool I do the same with the HRD. Its been quite a journey.

Do you have any experience with the saratov 6l6GCs? The el84s by saratov are aweseome and my HRD needs some new tubes.

bluesky636
April 28th, 2011, 11:44 PM
Delete

bluesky636
April 28th, 2011, 11:45 PM
Cool I do the same with the HRD. Its been quite a journey.

Do you have any experience with the saratov 6l6GCs? The el84s by saratov are aweseome and my HRD needs some new tubes.

I'm a Eurotubes/JJ fan. :grin:

MickJaggersTele
April 30th, 2011, 04:09 AM
That should work!!

I'm very happy with my sound with Jan Phillips 5751s in V1 and V2 and a Tung-Sol 12AX7 in V3.
I also use Fender SCN pickups in my 3 Teles and a Strat (I like the Tele pickups even better than the Strat).
The amp is so completely quiet, with no hiss or hum, that you don't know that the amp is even on if you are not playing.

I recently ordered a 12AT7 to try in V3, after posting in some of these BDRI threads on preamp tubes, just to experiment.
I have the feeling that this might be too much of a gain reduction without going to a 12AX7 in V2, as you have done.

Either one of these preamp combos are probably the ticket for this amp!!:mrgreen:
Well BlueSky636, my tubes arrived from the TubeDepot and I tested the following tubes in my Blues Deluxe Reissue:

(A) V1 Jan Philips 5751 -- V2 Jan Philips 5751 -- V3 Tung-Sol 12AX7

VS.

(B) V1 Jan Philips 5751 -- V2 Tung-Sol 12AX7 -- V3 Jan Philips 12AT7

The comparison test was performed with Winged "C" (=C=) Svetlana SED 6L6GC in V4 and V5 biased at 68mv.

Both tube lineup (A) and (B) were pretty close.
Different Amp settings were tried, but remained the same for both with Bass 12, Mid 3, Treble 10, Presence 10, Volume 4, Master 3, Gain 12, Reverb 4, Brightness off. Guitar input 2 was used for this test. A "BBE Sonic Stomp" sound conditioner was also used, hooked up to the effects loop with patch cords, with both dials set to 12 o'clock. This sound conditioner produces a subtle increase in the presence and clarity of the amp.

Both (A) and (B) Tube lineups were an improvement over the original three 12AX7 lineup.
The amp no longer farts out and has additional headroom with both tube lineups.
Both tube lineups also eliminated nearly all amp hiss, and all hum was eliminated by the use of noiseless pickups with these lower gain tube lineups.

The (B) Tube lineup produced a very nice high end "sparkle" that wasn't quite there with the (A) Tube line-up.
The (B) Tube lineup was was also slightly louder in the second gain channel than the (A) Tube lineup, prompting the raising of the Master to closer to 4 for the (A) Tube Lineup to create an equivalent gain channel volume.

But the (B) Tube line-up sounded somewhat thinner and was not quite as full sounding as the (A) Tube line-up.
As Bass is maxed at 12, increasing the Mid to 5 or 6 did not produce an improved fullness of sound of the (B) Tube lineup, nor did reducing Treble. Neither setting change corrected the somewhat thinner sound of the (B) Tube lineup. It merely produced a somewhat more muddy sound.

My final analysis regarding the test of these preamp tubes in my amp is that there is a slight trade off, which ever way you go, but I have to stay with the (A) tube lineup, as recommended for the BDRI by Derek Rocco, from Watford Valves.

For me, the slightly fuller sound of the (A) Tube lineup, edges out the nicer "sparkle" of the (B) Tube lineup in importance.

http://www.watfordvalves.com/cgi-bin/forum/cutecast.pl?session=ZTBX4XBpm0Mp7dwrsPDt6vulMK&forum=2&thread=364

There would be one BDRI preamp tube combination left to try:

V1 Jan Philips 5751 -- V2 Tung-Sol 12AX7 -- V3 Jan Philips 5751

Somewhere, I believe that I have read that for some unknown reason, 5751's are not recommended in the V3 phase inverter position.
I don't know of any 5751 "spec." that would cause this to be the case.
I will try to test this combination soon.

bluesky636
April 30th, 2011, 08:14 AM
Well BlueSky636, my tubes arrived from the TubeDepot and I tested the following tubes in my Blues Deluxe Reissue:

(A) V1 Jan Philips 5751 -- V2 Jan Philips 5751 -- V3 Tung-Sol 12AX7

VS.

(B) V1 Jan Philips 5751 -- V2 Tung-Sol 12AX7 -- V3 Jan Philips 12AT7

The comparison test was performed with Winged "C" (=C=) Svetlana SED 6L6GC in V4 and V5 biased at 68mv.

Both tube lineup (A) and (B) were pretty close.
Different Amp settings were tried, but remained the same for both with Bass 12, Mid 3, Treble 10, Presence 10, Volume 4, Master 3, Gain 12, Reverb 4, Brightness off. Guitar input 2 was used for this test. A "BBE Sonic Stomp" sound conditioner was also used, hooked up to the effects loop with patch cords, with both dials set to 12 o'clock. This sound conditioner produces a subtle increase in the presence and clarity of the amp.

Both (A) and (B) Tube lineups were an improvement over the original three 12AX7 lineup.
The amp no longer farts out and has additional headroom with both tube lineups.
Both tube lineups also eliminated nearly all amp hiss, and all hum was eliminated by the use of noiseless pickups with these lower gain tube lineups.

The (B) Tube lineup produced a very nice high end "sparkle" that wasn't quite there with the (A) Tube line-up.
The (B) Tube lineup was was also slightly louder in the second gain channel than the (A) Tube lineup, prompting the raising of the Master to closer to 4 for the (A) Tube Lineup to create an equivalent gain channel volume.

But the (B) Tube line-up sounded somewhat thinner and was not quite as full sounding as the (A) Tube line-up.
As Bass is maxed at 12, increasing the Mid to 5 or 6 did not produce an improved fullness of sound of the (B) Tube lineup, nor did reducing Treble. Neither setting change corrected the somewhat thinner sound of the (B) Tube lineup. It merely produced a somewhat more muddy sound.

My final analysis regarding the test of these preamp tubes in my amp is that there is a slight trade off, which ever way you go, but I have to stay with the (A) tube lineup, as recommended for the BDRI by Derek Rocco, from Watford Valves.

For me, the slightly fuller sound of the (A) Tube lineup, edges out the nicer "sparkle" of the (B) Tube lineup in importance.

http://www.watfordvalves.com/cgi-bin/forum/cutecast.pl?session=ZTBX4XBpm0Mp7dwrsPDt6vulMK&forum=2&thread=364

There would be one BDRI preamp tube combination left to try:

V1 Jan Philips 5751 -- V2 Tung-Sol 12AX7 -- V3 Jan Philips 5751

Somewhere, I believe that I have read that for some unknown reason, 5751's are not recommended in the V3 phase inverter position.
I don't know of any 5751 "spec." that would cause this to be the case.
I will try to test this combination soon.

Interesting but not unsuprising results. One general comment I would make would be to ditch the BBE box and rerun your tests without it. You are testing tube combinations and really want to minimize any external influences to keep them from mucking up the comparison. I would also try upping the bias somewhat. My BDRI (using JJ 6L6GCs) is biased at 38 mA cathode current (approximately 36 mA plate current) at a plate voltage of 413 VDC (about 85 mV at the Fender test point) and sounds much warmer and smoother than when biased at lower settings.

Keep in mind that the BDRI does not really have a "drive" channel in the same context that the Hot Rod Deluxe does. In the BDRI, drive is achieved by removing the volume control between the two halves of V1 so that the gain of V1 is now maxed out. The gain control for drive then appears between V1 and V2 allowing the maxed out gain of V1 to drive V2 at whatever level the gain control is set at.

As the gain factors of a 5751 and 12AT7 are very close (70 for the 5751 and 60 for the 12AT7), I would expect that the overall amp gain would be very close for combinations A & B, and it appears that they are. Also, V1 has the greatest affect on signal to noise ratio and since you have a 5751 in V1 of both combinations, I would also expect the S/N ratio of both combinations to be similar. V2 is primarily for tone stack gain recovery so a 12AX7 may be a better choice to make up for the lost gain. Also V2 does not have as much of an effect on tone as V1 does (neither does V3 have much effect on tone). Since the 12AT7 is designed primarily as a driver, I think it would be a better choice in V3 than a 5751. I believe that the 12AT7 has higher current drive capability than either a 12AX7 or 5751 which makes it better suited than either of those two in V3.

I can't comment too much on your oveall tone observations as that is also greatly influenced by room acoustics. I have my tone setting at Treble = 6, Bass = 4, Middle = 2, and Presence = 8 which sounds fantastic with my SCN equipped Strat. I switch to the drive channel (which reduces bass response slightly) when using my two humbucker equipped guitars which smooths things out and eliminates the overbearing bass that would occur otherwise with a humbucker guitar plugged into this amp. I also plug the Strat into input #1 and the humbucker guitars into input #2. I set both the clean volume and drive volume to 8 and use the master volume to balance the levels of the clean and drive channels. My amp also sits fairly close to the wall behind it which boosts the bass somewhat and may account for the differences in our prefered bass settings.

I think the key to getting a great sound out of the BDRI is easily accomplished by:

a. Reducing the overall gain of the amp which makes the volume and gain controls much more useable. Both of your combinations and my prefered combination appear to do that.

b. Using a "sweeter" sounding tube in V1. The choice of a 5751 in V1 appears to be an excellent one. A 12AY7 may also be a good choice (and would refuce the overall amp gain even further).

I have found that my choice of tubes has smoothed out the amp considerably and eliminated all harshness in the upper mids and treble and fartiness in the bass. Your choices appear to do the same. It has even reduced my desire to replace the stock speaker in my BDRI. After a thorough break-in, I find the stock speaker sounds really nice.

Finally, instead of the third combination that you proposed trying out, I would recommend trying the following:

V1 = 12AY7, V2 = 12AX7, V3 = 12AX7 or 12AT7. I think that would be a more tonefull and usefull combination.

Have fun! :grin:

MickJaggersTele
April 30th, 2011, 04:00 PM
Interesting but not unsuprising results. One general comment I would make would be to ditch the BBE box and rerun your tests without it. You are testing tube combinations and really want to minimize any external influences to keep them from mucking up the comparison. I would also try upping the bias somewhat. My BDRI (using JJ 6L6GCs) is biased at 38 mA cathode current (approximately 36 mA plate current) at a plate voltage of 413 VDC (about 85 mV at the Fender test point) and sounds much warmer and smoother than when biased at lower settings.

Keep in mind that the BDRI does not really have a "drive" channel in the same context that the Hot Rod Deluxe does. In the BDRI, drive is achieved by removing the volume control between the two halves of V1 so that the gain of V1 is now maxed out. The gain control for drive then appears between V1 and V2 allowing the maxed out gain of V1 to drive V2 at whatever level the gain control is set at.

As the gain factors of a 5751 and 12AT7 are very close (70 for the 5751 and 60 for the 12AT7), I would expect that the overall amp gain would be very close for combinations A & B, and it appears that they are. Also, V1 has the greatest affect on signal to noise ratio and since you have a 5751 in V1 of both combinations, I would also expect the S/N ratio of both combinations to be similar. V2 is primarily for tone stack gain recovery so a 12AX7 may be a better choice to make up for the lost gain. Also V2 does not have as much of an effect on tone as V1 does (neither does V3 have much effect on tone). Since the 12AT7 is designed primarily as a driver, I think it would be a better choice in V3 than a 5751. I believe that the 12AT7 has higher current drive capability than either a 12AX7 or 5751 which makes it better suited than either of those two in V3.

I can't comment too much on your oveall tone observations as that is also greatly influenced by room acoustics. I have my tone setting at Treble = 6, Bass = 4, Middle = 2, and Presence = 8 which sounds fantastic with my SCN equipped Strat. I switch to the drive channel (which reduces bass response slightly) when using my two humbucker equipped guitars which smooths things out and eliminates the overbearing bass that would occur otherwise with a humbucker guitar plugged into this amp. I also plug the Strat into input #1 and the humbucker guitars into input #2. I set both the clean volume and drive volume to 8 and use the master volume to balance the levels of the clean and drive channels. My amp also sits fairly close to the wall behind it which boosts the bass somewhat and may account for the differences in our prefered bass settings.

I think the key to getting a great sound out of the BDRI is easily accomplished by:

a. Reducing the overall gain of the amp which makes the volume and gain controls much more useable. Both of your combinations and my prefered combination appear to do that.

b. Using a "sweeter" sounding tube in V1. The choice of a 5751 in V1 appears to be an excellent one. A 12AY7 may also be a good choice (and would refuce the overall amp gain even further).

I have found that my choice of tubes has smoothed out the amp considerably and eliminated all harshness in the upper mids and treble and fartiness in the bass. Your choices appear to do the same. It has even reduced my desire to replace the stock speaker in my BDRI. After a thorough break-in, I find the stock speaker sounds really nice.

Finally, instead of the third combination that you proposed trying out, I would recommend trying the following:

V1 = 12AY7, V2 = 12AX7, V3 = 12AX7 or 12AT7. I think that would be a more tonefull and usefull combination.

Have fun! :grin:
Hi Bill,
That's a great suggestion: V1 = 12AY7, V2 = 12AX7, V3 = 12AX7

I think your analysis is pretty much right on the money. Running your JJ 6L6GC biased at 85 mV at the Fender test point might resolve the slight thinness of the sound that I associated with the (B) Tube combination. Some day I'll try that combination again with a higher bias setting, and see if I can get both the "sparkle" and the fullness of sound that I want.

If I'm not mistaken, JJ 6L6GC require a higher bias than most other 6L6GC's. I'm not sure that I would want to set my bias above 80mv at the test point, even though I realize that 80mv is still less than 70% of 6L6GCs rated plate dissipation at a plate voltage of 413 - 435 VDC.

I think that V1 = 12AY7, V2 = 12AX7, V3 = 12AT7 would probably have a little too low of a gain structure.
This was certainly the case when I tried a V1 = 5751, V2 = 5751, V3 = 12AT7 combination.

As for the BBE Sonic Stomp, I left it connected with what would be neutral settings, as it really doesn't affect the sound in any way except to maximize presence and clarity. I really swear by this little box which I hook up with patch cables into the effects loop, and run all other effects pedals into the front of the amp with the guitar cable.

I do this, do to the fact that when the Sonic Stomp is connected by a 12' Monster Cable, and inputted into the amp in any manner, there is a high frequency "whistle." It seems that the Sonic Stomp doesn't like long cables with these amps. BBE claims to have no knowledge of this problem. In any event, patch cords into the effects loop resolves this problem. Since there is never a need to turn the box off, sitting the box on top of the amp doesn't matter.

The Sonic Stomp produces amazing, yet very subtle sound conditioning results. Since in my opinion, this box can do nothing but improve the sound, I left it on during the test.

Mike

Davo17
April 30th, 2011, 04:26 PM
Interesting but not unsuprising results. One general comment I would make would be to ditch the BBE box and rerun your tests without it. You are testing tube combinations and really want to minimize any external influences to keep them from mucking up the comparison. I would also try upping the bias somewhat. My BDRI (using JJ 6L6GCs) is biased at 38 mA cathode current (approximately 36 mA plate current) at a plate voltage of 413 VDC (about 85 mV at the Fender test point) and sounds much warmer and smoother than when biased at lower settings.

Keep in mind that the BDRI does not really have a "drive" channel in the same context that the Hot Rod Deluxe does. In the BDRI, drive is achieved by removing the volume control between the two halves of V1 so that the gain of V1 is now maxed out. The gain control for drive then appears between V1 and V2 allowing the maxed out gain of V1 to drive V2 at whatever level the gain control is set at.

As the gain factors of a 5751 and 12AT7 are very close (70 for the 5751 and 60 for the 12AT7), I would expect that the overall amp gain would be very close for combinations A & B, and it appears that they are. Also, V1 has the greatest affect on signal to noise ratio and since you have a 5751 in V1 of both combinations, I would also expect the S/N ratio of both combinations to be similar. V2 is primarily for tone stack gain recovery so a 12AX7 may be a better choice to make up for the lost gain. Also V2 does not have as much of an effect on tone as V1 does (neither does V3 have much effect on tone). Since the 12AT7 is designed primarily as a driver, I think it would be a better choice in V3 than a 5751. I believe that the 12AT7 has higher current drive capability than either a 12AX7 or 5751 which makes it better suited than either of those two in V3.

I can't comment too much on your oveall tone observations as that is also greatly influenced by room acoustics. I have my tone setting at Treble = 6, Bass = 4, Middle = 2, and Presence = 8 which sounds fantastic with my SCN equipped Strat. I switch to the drive channel (which reduces bass response slightly) when using my two humbucker equipped guitars which smooths things out and eliminates the overbearing bass that would occur otherwise with a humbucker guitar plugged into this amp. I also plug the Strat into input #1 and the humbucker guitars into input #2. I set both the clean volume and drive volume to 8 and use the master volume to balance the levels of the clean and drive channels. My amp also sits fairly close to the wall behind it which boosts the bass somewhat and may account for the differences in our prefered bass settings.

I think the key to getting a great sound out of the BDRI is easily accomplished by:

a. Reducing the overall gain of the amp which makes the volume and gain controls much more useable. Both of your combinations and my prefered combination appear to do that.

b. Using a "sweeter" sounding tube in V1. The choice of a 5751 in V1 appears to be an excellent one. A 12AY7 may also be a good choice (and would refuce the overall amp gain even further).

I have found that my choice of tubes has smoothed out the amp considerably and eliminated all harshness in the upper mids and treble and fartiness in the bass. Your choices appear to do the same. It has even reduced my desire to replace the stock speaker in my BDRI. After a thorough break-in, I find the stock speaker sounds really nice.

Finally, instead of the third combination that you proposed trying out, I would recommend trying the following:

V1 = 12AY7, V2 = 12AX7, V3 = 12AX7 or 12AT7. I think that would be a more tonefull and usefull combination.

Have fun! :grin:

Any thoughts on how long-plate preamp tubes would compare vs shortplate in the HR and BD amps?

bluesky636
April 30th, 2011, 06:04 PM
Hi Bill,
That's a great suggestion: V1 = 12AY7, V2 = 12AX7, V3 = 12AX7

I think your analysis is pretty much right on the money. Running your JJ 6L6GC biased at 85 mV at the Fender test point might resolve the slight thinness of the sound that I associated with the (B) Tube combination. Some day I'll try that combination again with a higher bias setting, and see if I can get both the "sparkle" and the fullness of sound that I want.

If I'm not mistaken, JJ 6L6GC require a higher bias than most other 6L6GC's. I'm not sure that I would want to set my bias above 80mv at the test point, even though I realize that 80mv is still less than 70% of 6L6GCs rated plate dissipation at a plate voltage of 413 - 435 VDC.

I think that V1 = 12AY7, V2 = 12AX7, V3 = 12AT7 would probably have a little too low of a gain structure.
This was certainly the case when I tried a V1 = 5751, V2 = 5751, V3 = 12AT7 combination.

As for the BBE Sonic Stomp, I left it connected with what would be neutral settings, as it really doesn't affect the sound in any way except to maximize presence and clarity. I really swear by this little box which I hook up with patch cables into the effects loop, and run all other effects pedals into the front of the amp with the guitar cable.

I do this, do to the fact that when the Sonic Stomp is connected by a 12' Monster Cable, and inputted into the amp in any manner, there is a high frequency "whistle." It seems that the Sonic Stomp doesn't like long cables with these amps. BBE claims to have no knowledge of this problem. In any event, patch cords into the effects loop resolves this problem. Since there is never a need to turn the box off, sitting the box on top of the amp doesn't matter.

The Sonic Stomp produces amazing, yet very subtle sound conditioning results. Since in my opinion, this box can do nothing but improve the sound, I left it on during the test.

Mike

Yes, I think V1 = 12AY7, V2 and V3 = 12AX7 would be an interesting combo. A 12AT7 in V3 with a 12AY7 in V1 might be too low in gain.

It's not that the JJ 6L6GCs "require" a higher bias setting, but that they can handle a higher bias setting than some tubes, particularly the Groove Tubes that typically come in Fenders. My BDRI came equipped with Groove Tube/SOVTEK 5881/6L6R tubes which are not true 6L6GCs and have a max plate dissipation of 25 watts vice the JJ tube's 30 watts. The 5881s are not recommended for use above 70 mV as measured at the Fender test point.

Let us know if you do any other comparisons. :grin:

bluesky636
April 30th, 2011, 06:07 PM
Any thoughts on how long-plate preamp tubes would compare vs shortplate in the HR and BD amps?

It is my understanding that long plate peramp tubes are not recommended for use in combo amps due to their higher susceptability to vibration induced microphonics from the co-located speaker compared to short plate tubes.

gypsyseven
August 3rd, 2012, 03:32 AM
I know, maybe a little late to get into this thread, but i was searching for some tube rec ommendation to get the best "clean" sound out of my Blues Deluxe...
Right now i'm using a 5751 in V1, 12ax in V2 and a 12AT in V3.
Sounds much better than the stock configuration, but i thought maybe there's some other variation to get the best "clean" tones out of this amp...

Thanks so far for this thread.

bluesky636
August 3rd, 2012, 09:59 AM
Pretty much all workable combinations have been discussed in this thread. My current configuration is:

V1 = NOS JAN GE 12AY7
V2 = JJ 12AX7
V3 = JJ 12AX7
V4/5 = JJ 6L6GC

Drewsome007
August 3rd, 2012, 10:40 PM
I would think the Winged "C" 6l6's would have more effect on the overall clean sound. Right now I'm running V1-5751, V2-5751, v3-Ecc83s. With 2 JJ 6l6's and I noticed the JJ's warmed it up a bit.

bluesky636
August 4th, 2012, 12:49 AM
I would think the Winged "C" 6l6's would have more effect on the overall clean sound. Right now I'm running V1-5751, V2-5751, v3-Ecc83s. With 2 JJ 6l6's and I noticed the JJ's warmed it up a bit.

Depends a lot on how the tubes are biased.

Toto'sDad
August 4th, 2012, 01:30 AM
Not long before I sold my Blues Deluxe ( a mistake ) I put a 12AT7 in V3 and was amazed at the immediate improvement in the depth of tone. It was less bright, fuller, and just more of everything I liked about it, both clean and in the drive channel, which is admittedly not much drive, but it sounds so good with a Strat.

Drewsome007
August 5th, 2012, 12:04 PM
Depends a lot on how the tubes are biased.

I have mine biased at 60 mv at the test port.

bluesky636
August 5th, 2012, 12:23 PM
I have mine biased at 60 mv at the test port.

Way too cold, especially for JJs. That corresponds to about 30 mA per tube cathode current and about 28 mA plate current. You need to know what the plate voltage is also to calculate the % of maximum plate dissipation. I run my JJ 6L6GCs at 40 mA cathode current/38 mA plate current at 410 VDC plate voltage. That corresponds to 53% maximum plate dissipation (which is still cold but sounds good) and measures as 88 mV at the Fender test point.

Drewsome007
August 16th, 2012, 09:50 PM
Way too cold, especially for JJs. That corresponds to about 30 mA per tube cathode current and about 28 mA plate current. You need to know what the plate voltage is also to calculate the % of maximum plate dissipation. I run my JJ 6L6GCs at 40 mA cathode current/38 mA plate current at 410 VDC plate voltage. That corresponds to 53% maximum plate dissipation (which is still cold but sounds good) and measures as 88 mV at the Fender test point.

Took your advise and bumped it up to 80mV at the test point, and I'm really loving the sound. I did however notice after about an hour of playing, the tubes have small burn marks on the interior of the glass, I never noticed it before so I'm wondering if this is just normal now that I've got more "juice" running through.

bluesky636
August 16th, 2012, 10:10 PM
Took your advise and bumped it up to 80mV at the test point, and I'm really loving the sound. I did however notice after about an hour of playing, the tubes have small burn marks on the interior of the glass, I never noticed it before so I'm wondering if this is just normal now that I've got more "juice" running through.

I don't know what you mean by "burn marks".

You need to reread my post. 80 mV by itself means nothing. You need to measure the plate voltage also to calculate the % of maximum plate dissipation at idle.

musicmatty
August 16th, 2012, 10:50 PM
I don't know what you mean by "burn marks".


You need to reread my post. 80 mV by itself means nothing. You need to measure the plate voltage also to calculate the % of maximum plate dissipation at idle.


Over my head..but burn marks on the Tubes can't be a good thing :shock:

bluesky636
August 16th, 2012, 10:57 PM
Over my head..but burn marks on the Tubes can't be a good thing :shock:

Which is why you need to measure the plate voltage as well as cathode/plate current to determine the tube power dissipation at idle to be sure that tubes aren't biased too hot. :wink: