Hot Rod Deluxe - 6v6's instead of 6L6's

Discussion in 'Amp Tech Center' started by BigDaddy23, Apr 2, 2019.

  1. BigDaddy23

    BigDaddy23 Tele-Meister

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    Hey all,

    A mate of mine has one of these monsters and he wants to look at taming it down some. It is stupid loud at 3! Is it feasible to run 6v6 tubes in lieu if the 6L6's? He doesn't have the cash to buy a new amp so wants to look at potential mod options which I am happy to do for him.

    It runs an 8ohm speaker but has a 4ohm tap on the OP tranny for ext speaker use. I was thinking about disconnecting the 8 and using the 4ohm tap only to deal with the impedance mismatch from the tube change. It is bridge rectified with 430v B+ according to the schematic. It has bias adjustment so I can hopefully rebias to a suitable PD.....if not perhaps look at the tough JJ 6v6S tubes. I guess the other option is to build an attenuator? What do u guys think?

    I have the schematic in pdf but can't find a decent hi-res pic to post for reference. You can see the pdf here http://blueguitar.org/schems.htm under fender/hot rod deluxe

    Thanks for your thoughts/opinions!
     
  2. ReverendRevolver

    ReverendRevolver Tele-Meister

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    When my father bought his he had loudness problems and built a little attenuater type box that runs in the effects loop to keep it in check.

    I feel like he googled up a schematic and spent $12 at radio shack.

    Simpler than 6v6s.

    Also, HR volume pot isn't as linear as other pots. IIRC, for marketing reasons, the realized people weren't diming the volume when shopping, so made 12 o clock as loud as other amps 3 o clock, and everything past that isn't much increase.
     
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  3. galaxiex

    galaxiex Tele-Holic Silver Supporter

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    Put a lower gain tube in V1.
    Try a 12AT7 and see how that works.
     
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  4. Mark the Moose

    Mark the Moose Tele-Meister

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    Years ago I modded a blues deluxe, including a swap to 6v6. I can't recall if I had to change the transformer tap, but the tech who's video I worked from was adamant that you had to use JJ power tubes as they handle a higher plate voltage than other manufacturers.

    Honestly, it wasn't noticeably quieter. Your best bet is an attenuator and an inefficient speaker. It's also worth a lower gain preamp tube in V1.
     
  5. BigDaddy23

    BigDaddy23 Tele-Meister

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    Thanks fellas. I have some other tubes I can try in the preamp. I knew others would have had similar issues. What is the difference between running an attenuator via the FX loop vs in series with the speaker? are they the same devices? I need to do a bit more reading on tgem and would prefer to build it rather than buy it if practical.
     
  6. RetroTeleRod

    RetroTeleRod Poster Extraordinaire

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    Regarding what ReverendRevolver mentioned, Brian Wampler builds and demos an effects loop volume box here. Sweet!
     
    Last edited: Apr 2, 2019
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  7. Mark the Moose

    Mark the Moose Tele-Meister

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    The FX loop is a line level signal where you could put a simple volume control. As the amp already has a master volume, this would be redundant but would give you finer control with the master volume at low levels. The attenuator, or an l-pad, or something similar would take the powered signal from the amp and convert some of that signal to heat while passing the rest on to the speaker. This system allows you to drive all stages of the amp at levels where the tubes are really working and sounding good, then drop the volume after the power stage.
     
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  8. Bob M

    Bob M Tele-Afflicted Ad Free Member

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    I had a tech install a more "linear" volume pot in a late '90s HRD I had. It made the amp much more useable IMHO. Cheap mod, better alternative to the tube swap idea.
     
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  9. Fearnot

    Fearnot Friend of Leo's

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    The problem with that 'loop volume box' is that you're getting all your drive from the preamp, and none from the power amp, which is where the good stuff happens. Still, it seems like a good-enough workaround to make a 40-watt amp useable at home.

    Did Wampler say you could do the same thing with an EQ pedal? Seems like that would work fine too.
     
  10. clintj

    clintj Friend of Leo's

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    To the OP: You're cutting potential volume by about 3dB by swapping to 6V6 tubes. Not much difference. If anything, it may be more sensitive to minor volume adjustments, as the 6V6 is an easier tube to overdrive.

    +1 on the suggestions for a loop mounted volume control and a 12AY7 in V1. The loop gives you control over both clean and drive channels together.

    Sent from my Pixel 2 using Tapatalk
     
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  11. BigDaddy23

    BigDaddy23 Tele-Meister

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    This is what he wants - power tube OD but at a lower volume. It seems that a mixed approach may be required. Are there any attenuator plans that people would recommend?
     
  12. Rick330man

    Rick330man Tele-Holic

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    I really like these amps. I had two, but sold one to a life-long friend who wanted an HRD but couldn't afford a new one. In 18 years with HRDs, a bit of experimenting has been had on my part.

    Like others, I tried the 6V6 option in my Hot Rod Deluxes. In one word: unimpressive! It castrates the amp's beautiful clean Fender chime. Stick to 6L6 power tubes.

    A 1980s production JAN GE 5751 in the phase inverter is the best thing you can do for these amps. Next, play around with a good 12AY7 or 5751 in V1.

    Good luck.
     
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  13. BigDaddy23

    BigDaddy23 Tele-Meister

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    Thanks mate. Can you describe what the PI tube change did? It looks to be a cathodyne PI which don’t usually add gain as opposed to the long tail pair PI (I think).
     
  14. Dacious

    Dacious Poster Extraordinaire

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    It's just a conventional long tail phase inverter.

    This preamp is kinda like a big old Tweed like a Bassman. In those amps V1 split for the two channels was a 12AY7 - possibly to optimise for microphones as well as bass. The PI was usually a 12AT7.

    When Fender released this line the only current production tubes were 12AX7s so they used them in all positions.

    We put a lower input V1 tube in my bandmates HRDx and it's massively improved it - clean, reverb, drive leading me to suspect the amp would be much improved with a retubing.

    It won't make the amp break up at a lower volume but the volume goes from being nothing at 1.8 and too freakin loud at 2.1 to having a nice, usable range from about 2-6. And the eqs and reverb become much more usable.

    You can get a lovely Fender clean with reverb from it - not muddy yet harsh like it is standard.

    Allegedly the newer versions since 2010 are better but it seems still.a useful mod.

    Plus the horrible, honky, nasally overdrive becomes more Mesa-ish in a good way both in drive or more drive.
     
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  15. anthrotony

    anthrotony Tele-Meister

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    I have a HotRod Deville 410. I use the volume pot in the effects loop, but obviously that doesn't get any power tube OD, but it helps a lot. I have a 12AY7 in v1 and that really smoothes out the volume taper, and provides a much nicer general OD, and drops volume a bit. Input 2 drops 6db and is a big help. The only solution is a good attenuator. I'm building this one:

    http://www.marshallforum.com/threads/simple-attenuators-design-and-testing.98285/page-11

    FANTASTIC thread and superb attenuator. The only solution I think.
     
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  16. Rick330man

    Rick330man Tele-Holic

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    G'day, BigDaddy23:

    Dacious, your colleague down under did a pretty good job of explaining it, but using a 12AT7 in the PI. I'll cover both the 5751 and the 12AT7 options.

    The 1980s era GE 5751 does a wonderful job of really cleaning up the signal in every single amp in which I have used it for a PI. In the HRD, I hear it deliver better note definition and a fuller, more 3 dimensional tone out of every note or chord played. I've got a small room full of different tubes: 12AX7s, 5751s, 12AY7s, 12AZ7s, 12AU7s. There are plenty of NOS and new production versions of many of these. Nothing sounds as good in V3 of your HRD as a 1980s era JAN GE 5751.

    I have tried various 12AT7s as well. In fact, the HRD I sold to my friend got an EH 12AY7 in V1, a JJ ECC83S in V2 and a JAN Philips 12AT7 in V3. See Dacious' first sentence. This selection was not coincidental. This tube array gives you a lot of sweep on the clean volume. My friend usually plays with the volume around 7 and absolutely loves the tones he gets out of this tube array with his Hagstrom ES 335 copy. To my ears, the results with the 12AT7 are good, but the 12AT7 does not clean up the signal the way the GE 5751 does.

    Note: do not to cut too much of the pre-amp gain or the amp will sound anemic.

    My HRD has a 1980's JAN GE 5751 in V1, a JJ ECC83S in V2 and another 1980s JAN GE 5751 in V3. My power tubes are JAN Philips 6L6WGBs. I've also used old Sylvania 5751s in V1. I found those to be the best sounding tubes I ever used in V1, but they do not tolerate the amp's vibration (caused by the boomy bass) very well.

    Power tubes are another discussion I could write volumes on, but I'll limit this response (already too wordy) to the issue presented.

    Good luck, mate! I hope this information helps you and your band mate find the tone you all are looking for.
     
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  17. BigDaddy23

    BigDaddy23 Tele-Meister

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    Thanks for your replies fellas - I’ll test these options with him and will also look at the attenuator.
     
  18. Wally

    Wally Telefied Ad Free Member

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    I have found that a 12AY7 in V1 makes these amps much more usable. The 12AY7 changes the sweep of that volume pot. The gain structure resembles the 5F6A, and Leo used a 12AY7 there as well. I recently a couple of high dollar boutique amps based on the same topology around that both had very harsh raspy distortion until I put 12AY7’s V1 of both,.....they became much more musical with better distortion...to my ear. I don’t use a 12AX7’s in V1 of my Pro Sonic for the same reason.
     
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  19. BigDaddy23

    BigDaddy23 Tele-Meister

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    I've built a volume control for the effects loop which works well. You can crank the normal volume right up and get some grit and OD happening with much better control. The expected thinner sound at lower levels applied so the bass needed a boost. The Drive channel sounded fairly anaemic though. I reckon the attenuator may be a good option to try as well

    I had a good look through this thread - on the last page is the most up to date schematic. I agree it is a great read! I'd like to get this 40w amp down in the 15W range I reckon. From what I can gather, this attenuator can be built with Stage 1 plus any combination of stages 2-4 thereafter to attain the maximum desired power soak (ie perhaps only 2 or 3 stages all up). What do you guys think would be practical in the case of this HRD?
     
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  20. anthrotony

    anthrotony Tele-Meister

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    Hey BigDaddy23, As I was reading that thread, I initially had the same sort of feeling, to make something minimalist with fewer options, while offering just the levels of attenuation I thought I'd need. You probably saw the few posts around this question, somewhere around page 13 or 14 if I recall correctly. But the more I thought about it, I figured that for the cost of the components (most of those power resistors are available for just over £1 each if you're okay with Chinese produced components), I might as well simply build in the flexibility, so I ordered all resistors and several switches (package deal that cost almost nothing but means I'll have a good stock to choose from), I don't think I'll build the attenuator such that the final -3.5db stage can be used by itself, in front of the then disengaged inductor stage, as I really can't imagine that such a small amount of attenuation would ever be useful on its own. that would be a very small reduction in output SPL, and could probably be managed more easily by volume controls, or even just plugging into the second input.

    Now my amp is 60W, of course, so breakup is at a significantly louder volume than the standard 40W HRDx, so in my case I can definitely imagine using the full attenuation of 31.5db, which seemed absurd knowing how horrible most attenuators sound even at -12db attenuation. But this design really seems to deliver the goods without tone sucking.

    So realising that the theoretical difference of of -3db would equate to halving the amp's output watts, then a 20W output would deliver a volume level almost as loud as the 40W HRDv, so a 15W equivalence would be very similar. That's really loud (I can assure you as I also use a 15W Fender BassBreaker). So in face, that first stage already provides -7db of attenuation, so give or take the equivalent of perhaps a 10W output. This phenomenon was what eventually guided me to simply build to the maximum possible attenuation! Good luck with your own search :)
     
    Last edited: Apr 6, 2019
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