SIR #34 and #36 Frank Levi Mods in one Amp

Discussion in 'The Workbench' started by Eddylenz, Sep 8, 2019.

  1. Eddylenz

    Eddylenz Active Member

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    Hey Guys,

    I've been trying to get the real #34 and #36 specs for a long time. After trying the mods several times, I thought I just couldn't make #36 sound right. #34 always sounded great, as there's also a "correct" schematic that Santiago drew up after looking at Slash's real #34 amp, but there's lots of conflicting info on the #36 mod. After trying many different schematics and hours of tweaking, I think I finally got it.

    What do you think?

    The amp still has EL34 in it, as I can't afford a quad of 6550s right now, but I think the sound is still pretty much spot on. (For some of the AFD stuff, I should have maybe turned down the gain a bit more haha) I'm gonna make more videos trying to recreate that sound though.

    Watch it in 1080p for the best sound.



     
    Last edited: Sep 10, 2019
  2. Emtbreid

    Emtbreid Well-Known Member

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    Sounds pretty damn good to me!
     
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  3. john hammond

    john hammond Well-Known Member

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    sounds good.

    remember #36, #34 mods wont take into account any iron differences ( or glass differences) , even though iron may look the same, transformers vary because they're wound slightly differently, a few more turns here, a different winding pattern there, these things matter a lot more than you may think in an output transformer
    you may get ( most of ) the gain you want from replicating circuitry, but not necessarily frequency response.
    george metro says when he gets output transformers wound to his specs from heyboer, some are inferior, some are just like the favorite c1998's he picks out to get cloned by them out of his vintage amps that he owns...theres inconsistency within the same batches of transformers made.
    also consider that guitar slash used, that thing had harmonics like a rainbow.
     
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  4. john hammond

    john hammond Well-Known Member

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    if you cant get the same era dagnall or drake output transformer, whatever it was, then you need to find a suitable substitute, if one exists.. to even be in the same ballpark, tonally, as #34 and #36. If the iron you have there is a suitable substitute, then i'd say youre damn lucky.
     
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  5. LPMarshall hack

    LPMarshall hack Well-Known Member

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    Wow great tone and great playing!
     
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  6. Eddylenz

    Eddylenz Active Member

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    Thank you!
     
  7. Eddylenz

    Eddylenz Active Member

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    Yeah, I wanted to get a different OT for this amp, because it's a Marshall Clone and I have no idea what transformers are in there, but I can't spend that much money now. The same goes for a quad of 6550s, I still have EL34s in there. I'm still really happy with how the amp turned out though, never liked it more.
     
  8. RickyLee

    RickyLee Well-Known Member VIP Member

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    Dam, that sounds freakin' badass dude.

    I am envious for sure, as I messed with those 34/36/39 circuits and never could get them to sound like I was expecting. Did not have the clarity and chewiness your clips have, that is for sure.

    I am still not remembering which circuit is which? Is your 34 circuit like a standard 2203/4 topology - 3 stages then cathode follower? Then when you are switching it for more gain, you are going to a 36 circuit that adds in one more gain stage - 4 stages then cathode follower? Power amp is standard 2203/4 specs?

    I never did see any schematics showing the power amp or the preamp B+ voltages. I am still messing and tweaking with my white PlexiRod. But I am still considering trying that SIR circuit to get it right.


    I did build a project that is basically the Ceriatone AFD 35. But that amp is just not sounding right to me either . . . .
     
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  9. santiall

    santiall Well-Known Member

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    the 34 mod sounds good when the amp is very loud and in the mix but when played alone and at lower volumes it can be quite harsh
     
  10. RickyLee

    RickyLee Well-Known Member VIP Member

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    That is good info coming from you. Maybe I was closer than I had thought lol. I never tried my circuits within a band or any jams.

    I am going to pull my AFD 35 out here soon and go though it and check every aspect of what I did in there. Mine was what I was considering 36 as it has that extra gain stage. But I know my AFD 35 is nowhere near the clarity of Eddylenz clip above.

    Is the true 34 circuit the one with one less stage, like the 2203 layout/topology?
     
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  11. RickyLee

    RickyLee Well-Known Member VIP Member

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    Wait . . . . this thread is about Frank Levi circuits. Is that different than the SIR ones I am going on about? My memory is bad on what I read about this stuff a few years ago.
     
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  12. herbvis

    herbvis Active Member

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    Frank levi worked at sir and was the one behind the #34 mod. The #34 was the amp on the illusion albums. its the one without the added gain stage.
    Tim caswell did the #39 mod which was "cloned" in the #36 amp by Frank levi. Levi claimed to have removed caswells mod and put his own in #39. But we will probably never know for sure.
     
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  13. Eddylenz

    Eddylenz Active Member

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    Thanks!
    That's right, #34 basically a tweaked 800, and #36 adds another gain stage and some other stuff.
    I basically left my poweramp stock. Filtering has JCM800 values and there's more filtering for the extra stage that comes in when you activate #36.
    Frank Levi said in an interview, that he did that on the #36.
    The Ceriatone #35 Layout isn't quite right... at least for me. It's a good starting point though :D
     
  14. Eddylenz

    Eddylenz Active Member

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    Awesome to have you in this thread!
    Yeah, you really need to crank it.
    I've put a PPIMV in mine, which still needs to be turned up to about 2, for it to sound good.
    The pre PI Master has to be at around 8 to give you enough gain and make it sound right.
    That's why I'm also using an attenuator.
     
  15. Eddylenz

    Eddylenz Active Member

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    Just uploaded another video of the amp. This time, trying to get that Sweet Child O' Mine Tone.
     
  16. santiall

    santiall Well-Known Member

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    The PPIMV at low volumes can sound even harsher than a pre-inverter master. They tend to sound good only when set high which perhaps defeats the reason of having a master volume to begin with...

    Anyway, if you are happy with the results and the amp works for you then that's what matters!
     
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  17. Eddylenz

    Eddylenz Active Member

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    I agree. If the PPIMV is below 1,5 , you have to turn the presence and treble way down, but it's still better than without it because you can at least get that PI distortion, that's part of the sound, without an attenuator. To get the most out of the amp at low volumes, you still need one though.
     
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  18. itsneverloudenough

    itsneverloudenough New Member

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    Sorry about the necropost, Santiago is there an address I could contact you on, maybe PM? I would like to ask something if you don't mind
     
  19. South Park

    South Park Well-Known Member

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    The key to the three plus one preamp . Is by the time you get to the phase splitter things better be back to normal. That fourth tube really throws thinks out of wack gain and tone shaping.
     
  20. santiall

    santiall Well-Known Member

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    sure, you can send me a PM over here
     

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