Help! Preamp tube questions??

[boneyguy]

I've had a Traynor YSR-1 Custom Reverb for about a year now. I built a 1x12 cab for it and for most of that year I've been using an Emi Cannabis Rex. Great speaker btw.

About a week ago I built a new baffle for the cab and put a 15" Emi Legend 1518 in. Wow!! What a beautiful sound I'm getting. It's dramatically changed everything for the better. And it only cost me a total of $89 including taxes!!! I can't remeber the last time I was this happy.

The amp has 6 preamp tubes that are a cheap generic looking tube that has no brand name stamped on them, only a 'Made In China' sticker!!

I found some EH preamp tubes that I'd forgotten I had and put a 12AY7 in what I thought was the V1 slot and it made a slight difference. But then I removed it and put it in the socket nearest the power tubes and wow!!....the amp has once again improved very dramatically. Between the speaker change and the preamp tube change I'm absolutely in love with my old amp. For a while now the tone was leaving me cold. It didn't have any real depth or character to it but now it's complex, singing and rich in harmonics and I'm absolutley loving it.

Anyway I'd like to know more about the preamp tubes. Can you tell me from the schematic I've provided...

1) which preamp tubes do what according to their designation ie. V1, V2 etc.

2) which are the most important tubes in terms of how they will affect the tone of the amp and

3) are there slots where it doesn't really matter that much whether the preamp tubes are high quality.

4) can you tell me how the tube slots are oriented. In otherwords is V1 closest or the farthest slot from the power tubes?

[marshman]

Well, in virtually ALL guitar amps, V1 is located furthest from the power tubes. The becomes problematic, as in opposition to typical tube labelling practices, your power tubes are labelled V4 & V5. In terms of signal path, though, V1 is furthest from the power tubes, eg, the first tube with which your guitar signal interacts.


V1 & V2 handle "input duties"
V3 is your Phase inverter
V4 &V5 are your power tubes
V6 & V8 look like the reverb tubes--V6 looks like driver, V8 like recovery
V7 looks like your tremolo tube.

V1 should have a significant impact on your tone, as it's the first one in the path.
V3 & V6 (if I've read it right) would probably both benefit from being swapped with 12AT7s--my opinion only, of course.

Of course, very little of this actually answers the question of 'which tube is which?' You'll need what's generally referred to as a 'layout'. Some amps have had the tube designators stamped in the chassis, but you'd probably have noticed that. Perhaps an online manual?

Does anyone see a Reverb tranny in that schematic anywhere?

Hope this helps.

[boneyguy]

Originally Posted by marshman

Well, in virtually ALL guitar amps, V1 is located furthest from the power tubes. The becomes problematic, as in opposition to typical tube labelling practices, your power tubes are labelled V4 & V5. In terms of signal path, though, V1 is furthest from the power tubes, eg, the first tube with which your guitar signal interacts.


V1 & V2 handle "input duties"
V3 is your Phase inverter
V4 &V5 are your power tubes
V6 & V8 look like the reverb tubes--V6 looks like driver, V8 like recovery
V7 looks like your tremolo tube.

V1 should have a significant impact on your tone, as it's the first one in the path.
V3 & V6 (if I've read it right) would probably both benefit from being swapped with 12AT7s--my opinion only, of course.

Of course, very little of this actually answers the question of 'which tube is which?' You'll need what's generally referred to as a 'layout'. Some amps have had the tube designators stamped in the chassis, but you'd probably have noticed that. Perhaps an online manual?

Does anyone see a Reverb tranny in that schematic anywhere?

Hope this helps.

Thanks, this does help.

I initially replaced what you are saying is V1 with the EH 12AY7 and I didn't hear a huge difference. Then when I put the EH in what is likely the V8 slot, which you are saying is probably the reverb, I heard a major difference and that's where it stays at this moment. I'll have to grab some more preamp tubes and start.

I'm very unknowledgeable about these things so I'm on a steep learning curve at the moment. Thanks for your help.

[marshman]

Good strong 'vintage' 12AT7s are still quite affordable, often less than New Production. Keep your eye out. 12AY7s are a little trickier to get, but still out there. In terms of tone, the V1 is 'most influential'...a good V2 would also be a good idea. The driver tubes are the PI & 'verb driver, and 12AT7s are designed for that job. Most vintage Fenders used good, strong 12AX7s for the trem, though I'm not sure if there's other thoughts on the matter.

Mind, 12AY7s are just lower-gain variants of the 12AX7, so they're not always BETTER, just different...if you're inclined to hard, modern music, 12AX7s would probably be preferable.

Again, the trickiest part is still determining which tubes are which. With that many pre-amp tubes, I'm guessin' they're not all in a straight line, which complicates matters. I would be willing to go out on a limb and still guess that the tube closest to the power tubes is your PI, but beyond that, I'd be guessin' just like you.

[boneyguy]

Originally Posted by marshman

Good strong 'vintage' 12AT7s are still quite affordable, often less than New Production. Keep your eye out. 12AY7s are a little trickier to get, but still out there. In terms of tone, the V1 is 'most influential'...a good V2 would also be a good idea. The driver tubes are the PI & 'verb driver, and 12AT7s are designed for that job. Most vintage Fenders used good, strong 12AX7s for the trem, though I'm not sure if there's other thoughts on the matter.

Originally Posted by marshman

Mind, 12AY7s are just lower-gain variants of the 12AX7, so they're not always BETTER, just different...if you're inclined to hard, modern music, 12AX7s would probably be preferable.

Does this mean that a 12AT7 is a different type of tube than either the AX7 or the AY7? The 12AT7 is not just a lower gain version of an AX7?

Originally Posted by marshman

Again, the trickiest part is still determining which tubes are which. With that many pre-amp tubes, I'm guessin' they're not all in a straight line, which complicates matters. I would be willing to go out on a limb and still guess that the tube closest to the power tubes is your PI, but beyond that, I'd be guessin' just like you.

The preamp tubes and the power tubes are all in a straight line in my amp. I don't know if that helps you determine with more certainty which tube is which? I can tell you that putting the 12AY7 in the socket closest the power tubes made much more difference in sound than putting it in the slot farthest from the power tubes. Perhaps I should swap it out again and have another listen with the 12AY7 in both spots and see if in fact I still feel the same way.

[Raybob]

All 6 pre-amp tubes there should be a 12AX7 if you want the amp to sound like it's designed to sound like.

[Blue Whale]

Howdy boneyguy

Is there not a a tube layout chart inside the cabinet, as well as the schematic under the top inside? Anyway;

v1 -- first gain stage
v2 -- second gain stage
v6 -- reverb driver
v8 --reverb recovery
v7 -- tremolo
v3 -- phase inverter
v4 -- output EL34
v5 -- output EL34

These valves are all basically interchangeable have differing gains in this sort of range;

12AX7 ECC83 7025 100%
5751 70%
12AT7 ECC81 60-70%
12AY7 40-45%
12AU7 ECC82 20%

V1 - If you want to change the ratio of preamp tube distortion to output tube distortion then change V1 going from a 12AX7 to a 5751, this will reduce front end gain, a 12AY7 will reduce the front end gain further and generally give one more clean headroom.

V3 - The phase inverter works pretty hard and could well have been past it's best. You'll find a 12AT7 or an ECC81 makes a good phase inverter, party because of its much higher output current compared to a 12AX7.

The bottom line is whatever sounds best is best #:o)

[boneyguy]

Thanks Blue Whale. That's really great information.

The order of tubes that you show are the order they are actually arranged in the amp, correct?



I had to build a new enclosure for the amp head because the original was in very bad shape. The original enclosure is in storage with the diagrams. I guess I could have gone and had a look but it seemed easier just to ask on the forum. Also I get alot more information this way than I would just looking at a diagram I may not understand clearly.




Thanks again

[Blue Whale]

Originally Posted by boneyguy

The order of tubes that you show are the order they are actually arranged in the amp, correct?

That's correct, I have listed the physical layout of the tubes/valves as they are on the chassis.

All the best with it and your music.

[boneyguy]

Originally Posted by Blue Whale

That's correct, I have listed the physical layout of the tubes/valves as they are on the chassis.

All the best with it and your music.

Thank you sir. You've been a great help.

And thanks also to marshman who has given me great and accurate info as well.

I've come across a local electronics place that has a few NOS JAN Philips 12AT7WC tubes so I'm probably going to grab a couple of them to put in the driver slots as you've suggested marshman.

Thanks again guys.