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

Antônio S

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sure, you can send me a PM over here
Sorry about the necropost, Santiago could you take a look at my post? I would like to ask something if you don't mind.


Thanks!!
 

santiall

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Sorry about the necropost, Santiago could you take a look at my post? I would like to ask something if you don't mind.


Thanks!!
Hi, apologies for the late reply, please feel free to ask anything.
Regarding your post, the AFD mode is with the extra tube stage engaged, the switch on the 2nd stage OFF. IF you have seen the original schematics, those are drawn in AFD mode.
 

Antônio S

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Hi, apologies for the late reply, please feel free to ask anything.
Regarding your post, the AFD mode is with the extra tube stage engaged, the switch on the 2nd stage OFF. IF you have seen the original schematics, those are drawn in AFD mode.
Thanks for the reply, Santiago! Nothing like you to take the doubts.

So on my amp, the #34 switch must be off? Because just turning on the #36/AFD switch doesn't seem to get the real sound, just turning on the #34 switch together.

Here is the schematic that was used for construction.
 

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David Rivers

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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.





wow!! that amp sounds amazing,..i actually bought his afd amp,..and sadly it didnt perform well and i sold it and got the marshall yjm sig amp instead...keep rockin dude it sounds great!!
 

David Rivers

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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!
interesting info..good to know thanks
 

curt miller

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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.




Sounds good.
Wasn't the #36 used by George Lynch to get his dokken tones?
 

Ivan H

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Sounds good.
Wasn't the #36 used by George Lynch to get his dokken tones?
No, he used Tim Caswell's #39 amp. The #36 amp was created as Slash, who had used the #39 amp during rehearsals, specified that amp for the AFD sessions. When time came for Gunners to record, Lynch had already rented the #39 amp out for the first leg of Dokken's Under Lock & Key tour, so the #39 mod was replicated into the SIR stock #36 amp (from memory of being inside #39). There were a couple of capacitor value differences & whereas the mod was toggle switchable on #39, on #36 it was always on.
George Lynch was so impressed with #39 that he eventually tracked Tim Caswell down & had him modify an amp for him (eventually had Mr Caswell mod about 6 amps for him). Over the course of getting these amp modified, George requested higher gain, resulting in development of first the #39+ circuit, then later the #39++ (aka #39 GL) circuit. Cheers
 
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santiall

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Thanks for the reply, Santiago! Nothing like you to take the doubts.

So on my amp, the #34 switch must be off? Because just turning on the #36/AFD switch doesn't seem to get the real sound, just turning on the #34 switch together.

Here is the schematic that was used for construction.
for the AFD sound the switch has to be in position B and the switch between the 150k and the 100n open (on the second gain stage)
For the 34 sound you need the switch in position A and the switch between the 150k and the 100n closed.

The switch with under the 47ohm resistor is for muting the unused gain stage when in 34 mode so there isn't too much bleeding between channels. Depending on the layout it may not be necessary.

cheers
 

Gblev

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No, he used Tim Caswell's #39 amp. The #36 amp was created as Slash, who had used the #39 amp during rehearsals, specified that amp for the AFD sessions. When time came for Gunners to record, Lynch had already rented the #39 amp out for the first leg of Dokken's Under Lock & Key tour, so the #39 mod was replicated into the SIR stock #36 amp (from memory of being inside #39). There were a couple of capacitor value differences & whereas the mod was toggle switchable on #39, on #36 it was always on.
George Lynch was so impressed with #39 that he eventually tracked Tim Caswell down & had him modify an amp for him (eventually had Mr Caswell mod about 6 amps for him). Over the course of getting these amp modified, George requested higher gain, resulting in development of first the #39+ circuit, then later the #39++ (aka #39 GL) circuit. Cheers
George Lynch's #39 was done by Frank Levi. This is from George's main amp:

Lynch 50 watt main amp.jpg
 

Antônio S

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for the AFD sound the switch has to be in position B and the switch between the 150k and the 100n open (on the second gain stage)
For the 34 sound you need the switch in position A and the switch between the 150k and the 100n closed.

The switch with under the 47ohm resistor is for muting the unused gain stage when in 34 mode so there isn't too much bleeding between channels. Depending on the layout it may not be necessary.

cheers
Thanks for the replies, Santiago! I'm starting to understand my amplifier.

I believe that the switches that are on the amplifier's front panel control the relays in the internal circuit. Because when switch #34 is in the on position and switch #36 too, we have the afd sound, otherwise it looks like a JCM800 with 1 more gain stage.

I made some sound samples showing the different combinations of switches. It's nothing professional, just the iPhone's microphone right in the center of the speaker.

Switch #34 on and #36 off


Switch #34 off and #36 on


Switch #34 on and #36 on


I have attached some pictures showing the position of the switches and the amplifier's internal circuit.
 

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Ivan H

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George Lynch's #39 was done by Frank Levi. This is from George's main amp:

View attachment 107122
Lynch has had amps modded by many people, so it's not at all surprising that he has one done by Frank Levi. That doesn't change the fact that after one of the S.I.R staff told him who it was that had done the #39 mod, he (Lynch) was the first person to track Tim Caswell down in order to get him to perform the mod on an amp for him, eventually getting 6 of them done. Tim Caswell has posted on several forums under the name TimCas & has spoken of this, & how until speaking with George Lynch & then later with people on forums, he was unaware of the general publics interest in the amp or the GnR/AFD/#36 connection to his #39 modded super-trem amp, or that people were trying to figure the modifications out.
Whereas Mr Levi wasn't really forthcoming to the general public regarding the #39 & #36 modification specifics, Mr Caswell was, speaking with people & answering questions on forums, pointing people to a Mr P D Burnette's Photobucket layout of a 2204 Extra Stage Mod, 16518021058291557054137286106382.jpg
saying that it (the added stage part of the layout) was VERY CLOSE to what he had done to the #39 amp.
The (motorised controls) amp now sold by Caswell Amplification incorporates the original #39 mod, as well as the #39+ & #39++ mods (aka #39 GL), both of which Mr Caswell developed at the request of George Lynch while modifying amps for him. Cheers
 
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ibmorjamn

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Nice , yeah . It is interesting to read but it’s been a while since I read anything about all that.
Very nice info you put up.
 

santiall

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Thanks for the replies, Santiago! I'm starting to understand my amplifier.

I believe that the switches that are on the amplifier's front panel control the relays in the internal circuit. Because when switch #34 is in the on position and switch #36 too, we have the afd sound, otherwise it looks like a JCM800 with 1 more gain stage.
If you look at the original circuit you'll see that there are two relays that are switched simultaneously. One mode is the 34 mode, which is a JCM800 2203 with modified gain, the other mode is the AFD which is a 2203 with an added gain stage. There are 3 relay circuits but 2 physical relays in total
 

Gblev

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Thanks for the replies, Santiago! I'm starting to understand my amplifier.

I believe that the switches that are on the amplifier's front panel control the relays in the internal circuit. Because when switch #34 is in the on position and switch #36 too, we have the afd sound, otherwise it looks like a JCM800 with 1 more gain stage.

I made some sound samples showing the different combinations of switches. It's nothing professional, just the iPhone's microphone right in the center of the speaker.

Switch #34 on and #36 off


Switch #34 off and #36 on


Switch #34 on and #36 on


I have attached some pictures showing the position of the switches and the amplifier's internal circuit.

Your sample with both #34 and #36 on has the #36 sound the best to my ears, and it sounds pretty darn good. Congrats!
 

Gblev

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Lynch has had amps modded by many people, so it's not at all surprising that he has one done by Frank Levi. That doesn't change the fact that after one of the S.I.R staff told him who it was that had done the #39 mod, he (Lynch) was the first person to track Tim Caswell down in order to get him to perform the mod on an amp for him, eventually getting 6 of them done. Tim Caswell has posted on several forums under the name TimCas & has spoken of this, & how until speaking with George Lynch & then later with people on forums, he was unaware of the general publics interest in the amp or the GnR/AFD/#36 connection to his #39 modded super-trem amp, or that people were trying to figure the modifications out.
Whereas Mr Levi wasn't really forthcoming to the general public regarding the #39 & #36 modification specifics, Mr Caswell was, speaking with people & answering questions on forums, pointing people to a Mr P D Burnette's Photobucket layout of a 2204 Extra Stage Mod, View attachment 107135
saying that it (the added stage part of the layout) was VERY CLOSE to what he had done to the #39 amp.
The (motorised controls) amp now sold by Caswell Amplification incorporates the original #39 mod, as well as the #39+ & #39++ mods (aka #39 GL), both of which Mr Caswell developed at the request of George Lynch while modifying amps for him. Cheers
True, Lynch had a lot of amps modded by various people. There's a good story somewhere about when he found out that the #39 he loved and toured with was modded by Levi. I don't recall where it is now, but it's out there. You just need to do a search to find it. Frank was very forth coming about his mods as well, but he didn't post in forums. He talked to a lot of people and many have reposted his emails and letters around in various places. Frank didn't want the attention, neither did he want to debate things in forums. He would talk to anyone who messaged him, but he would not talk about #39 or #36 in detail. He would talk openly about #34 and help people with that mod, but not his Super Kill mod, or his Squirefire mod.

As far as Caswell goes, I've read some of his postings and it seems he is a nice guy who is willing to give people tips with their modding, and with his #39 mod. That was great of him to do. In the early 80's his #39 was the most rented S.I.R. amp, and that speaks for itself. But even Tim admits in another forum that the AFD sound does not sound like his #39 amp.

I'll say the same about Santiago, I've read a lot of his post over the years where he's willing to help people with their Slash mods, even here in this thread today! I think that is just awesome that he still answers people questions about these mods today more than 10 years later. I know he was a huge help to me in the past. Thanks Santiago!

I think we can thank Marshall, Santiago, and Slash for bringing these mods more out in the open when they did the AFD100. While these mods have been talked about in forums for a very long time, but nothing like they were once the AFD100 project started. While not everyone was able to get an AFD100, I believe it inspired a lot Slash fans to go out and start modding their amps in hopes of achieving those sounds. Whether someone went with a Caswell #39, a Levi #36 or #34, or they tried to copy the AFD100, in the end they all end up being flavors of a similar sound. Heck, I think a lot of people might have even discovered a few new mods in the same vein along the way.
 

Antônio S

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Your sample with both #34 and #36 on has the #36 sound the best to my ears, and it sounds pretty darn good. Congrats!
I agree with you. To my ears, the AFD sound is achieved with both switches (#34 and #36) in the on position. Turning just switch #36 seems to be missing something in the sound. Because it doesn't make much sense for the circuit to allow connecting 2 mods at once, the audio paths are different.
 

Antônio S

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If you look at the original circuit you'll see that there are two relays that are switched simultaneously. One mode is the 34 mode, which is a JCM800 2203 with modified gain, the other mode is the AFD which is a 2203 with an added gain stage. There are 3 relay circuits but 2 physical relays in total
Thanks again for the replies, Santiago! You're a really nice guy and you know a lot about amplifiers. Sorry for so many questions, but there is no one better than you to answer them.

I agree with all your statements, but it seems that the AFD sound comes when both switches (#34 and #36) are in the on position. I don't know if the builder, when distributing the relay functions, considered that mod #34 would need to be "on" to have the AFD sound. Because to my ears, just turning on switch #36 the sound is from a JCM800 2203/2204 with a gain boost, it doesn't have that characteristic tone. I think on second thought, there is no way to connect the 2 mods at the same time, they walk through different points of the circuit.
 

santiall

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Hi, there are 3 internal switches but two sound options 34 and AFD. It may be possible that you have too many options available externally but if wired properly you should have only one switch: 34 or AFD, the rest are combinations that shouldn't be accessible.
 

Gblev

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I agree with you. To my ears, the AFD sound is achieved with both switches (#34 and #36) in the on position. Turning just switch #36 seems to be missing something in the sound. Because it doesn't make much sense for the circuit to allow connecting 2 mods at once, the audio paths are different.
I think you're in a unique situation with your amp having the ability to switch between the modes the way you can. If you want the #36 sound, use the option that sounds best to you, like your #34 and #36 together. If that's what think gets you there the best. Then you have the other options to play around with to get many different sounds. You might be surprised at what all you can do just by tweaking a few knobs.

I know a lot of people try to set their amp to the settings seen marked on #34 with a magic marker in pics, or as Slash did in the AFD100 vlog, where everything was set on all 7's. But you have to remember, these should all be starting points. The pickups you use and the way you set them, the tubes you use, your bias setting, all of these are just a few of the things to consider that will affect your over all sound. The chances are slim that you will have all of this the same as him. So for you to get the sounds he does/did, you will need to spend a lot of time tweaking knobs, and maybe your pickups. If you have the basics down, the #36 or #34 modded amp, a Les Paul with APH-1's, you have the foundation for that sound to get close. The rest is up to you to find them.
 

lespaul6

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Does anyone know if Caswell is still doing this mod these days? also, I've never seen a PPIMV used with a real 36 or 39. If it is done like slash's 2203 there is no post phase master in that amp
 

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