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Help With Planning a Super Reverb Build

Discussion in 'Shock Brother's DIY Amps' started by MasonHN, Apr 12, 2021.

  1. MasonHN

    MasonHN NEW MEMBER!

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    Hey y’all, first post here.

    I’m planning my next build and I’m thinking about doing a blackface super reverb. But I wanted to see how possible it would be to convert the normal channel into something more tweed-voiced. Obviously, there’s a lot of differences besides just the preamp from a blackface amp and a tweed amp, but I’d still like to see what’s possible.

    I’m open to adding another tube for the normal channel to accomplish this. It seems like I just need one more triode and I could make a bassman style preamp out of the normal channel (if using just one channel from the bassman that is). How would this sound running into the super reverb power amp? I’d like to keep a stock super reverb vibrato channel, so the compromises are going to have to come from the tweed side.

    The other options I’ve come across would be something simple like a tone stack lift for the normal channel to get a rawer sound, not sure how that would sound but maybe it’d get close to what I want. And I think I saw some mods on robrobinette's site to voice the normal channel as a lead channel. Though I’m not sure that's really what I'm after.

    So, any ideas? Or is this just a sign that I need to build two more amps instead of one?
     
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  2. telemnemonics

    telemnemonics Telefied Ad Free Member

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    Maybe rather than looking at combining Tweed Bassman preamp with the SR, take a look at Dumble?

    Hunt for some Bonamassa recordings of same material but alternate his HPTT and his Dumble ODS sounds.
    Really similar I think, and the HPTT is my favorite Tweed sound.
    Bassman too of course but that's a whole amp, not just a preamp sound, where Dumble got similar stuff from the BF Fender topography and also included your question of tone stack lift, called PAB in the Dumble circuit, which is just a modded BF Fender circuit.
     
  3. telemnemonics

    telemnemonics Telefied Ad Free Member

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    BTW, welcome to the TDPRI!

    I'm not a Bonamassa fan or particularly a Dumble fan, but Howard arguably mastered in the '80s what you're starting now.

    And Bonamassa used those two circuits to do the same basic thing, making it an easy comparison sine the same player is used for testing.
     
  4. telemnemonics

    telemnemonics Telefied Ad Free Member

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    I used to add rawness to my SR's by utting the neg feedback on a pot or disconnecting it, pulling V1, and swapping the 12at7pi for a 12ax7.

    Not a huge jump but the neg feedback is pretty big.
     
  5. dougsta

    dougsta Tele-Meister

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    I'm going to keep an eye on what you do, I'm in the middle of prepping an empty chassis (2 3/4" x 6" x 24 1/2") and a 2 x 12" twin reverb size combo (all parts from solid state Frontman 212R as a donor). Will be my summer project.
    So far I'm thinking 2 channels, clean and crunch with a foot switch/relay for channel switching.
     
  6. Wally

    Wally Telefied Ad Free Member

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    Mason, welcome to the forum. You can revoice that Normal channel to decrease the tendency for that BF preamp to scoop the mids. You can then boost the mids to whatever level you want. Since it is a build, you could put a switching pot in to have two levels of midrange effect....or use an on/on/on in the second input hole position. Or...you could use a concentric pot to adjust the mids...IF you can find the right pot for that application vis-a-vis the vale’s for the two functi9ns.If wanted, you can apply the effects to that channel as well which will add a bit of gain there. Ime, one trick to all of this is to separate that common cathode circuit on pins8 of V1&V2. You can then maintain; the .Vib channel gain structure by using a 1.5K resistor on V2P8. You can apply a lower value resistor on V1P8 to acquire the gain you want there.
    I put a pot in series with the top resistor in the NFB loop so as to go from stock value to at least a 5,820ohm resistance there.
    Rob Robinette has a site that touches on some of these points. Ime, if you have been building, you should already have understanding of what I have outlined above.
     
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  7. J. Bonkosky

    J. Bonkosky Tele-Meister Silver Supporter

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    How about using the normal channel 12AX7 as two extra gain stages that cascade into the vibrato channel. Plug into the normal Channel side and you have a four gain stage amp with preamp gain control. The vibrato channel volume acts as the master volume and the tone controls act as they normally do. Plug into Vibrato channel and get standard super reverb sounds. Kind of like the high and low inputs on a JCM800.
     
  8. sds1

    sds1 Tele-Afflicted

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    @MasonHN welcome!

    What amp(s) are you thinking of when you say Tweed? I wasn't sure how to respond here. If 5E3 comes to mind, you can get a lot of Tweed Deluxe with the raw Tone control... but using the Tweed Bassman tone stack for example wouldn't get you anywhere. Nothing really Tweedy about that, on it's own...

    Here are a couple quick ideas for the power amp side: a 2 or 3-way NFB switch will help get you some Tweed. Also, maybe this is too radical, but I'd even suggest "dual rectifier!!111" and you use a solid state rectifier for the "blackface" mode and sub in a 5U4GB tube rectifier for when you want to get more Tweedy. And the reason I think this is an OK mod for the Super is because IMO the difference between GZ34 and SS rectifier is negligible.

    Fun build man!!! good luck.
     
  9. MasonHN

    MasonHN NEW MEMBER!

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    Thanks for all the suggestions so far! Lots of great ideas already.

    I'm gonna study some dumble amps and see what I can come away with. Cascading the normal channel into the vibrato channel is interesting but may end up being too much gain than what I want.

    As far as the tweed sound I would most want, I love the sound of a high-powered twin. I mentioned bassman in the OP because its power amp seemed the most similar to the super reverb vs the other tweed amps, given the LTP PI and that its fixed bias. But if I can get away with developing a cool preamp-focused sound for this "tweed" channel, maybe that won't matter so much.
     
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  10. Wally

    Wally Telefied Ad Free Member

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    There are a lot of different tweed sounds...with the 5F6A and 5F8A being the biggest and cleanest tweed sounds. Leo was forever moving toward that...bigger and cleaner. It is interesting to move the BF preamp toward what those big tweeds do. Is it exact? No...if that is what one wants, then one should build that circuit...as did Marshall and countless others have done and continue to do. However, ime, it is surprising to some what can be done to one of those BF/SF circuits to provide the versatility of two very different voices. There have been people who have asked what amp a player is using when it was obviously a BF or SF amp. When told that it was say a Bandmaster(non reverb), the response was..’it doesn’t sound like any Bandmaster I have ever heard!’....and an attempt to purchase was put forth.
    Good luck with the build. You are going to get a lot of suggestions. Some will be within your skill level, some may not. Build a Dumble clone if you are comfortable with that, but that is not what you asked for. There can be a very different Normal channel in a preamp based on the AB763 preamp.
     
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