Question about similarity between Bassman-based preamp circuits

D

Diego

New member
Hi everyone,

I’ve read that both the Marshall JTM/Plexi family and the Laney Supergroup are based on the Fender Bassman circuit. I'm unfortunately not very good at reading schematics, so as a Black Sabbath fan I was wondering:
Is it possible to recreate the Laney Supergroup sound using a Bassman- or JTM-style pedal, such as the PedalPCB Tweed Man OD or Covert OD?

If so, which component values would need to be changed to get closer to a Supergroup-style tone?



Thanks a lot for your help!
Diego
 
Laney made a 30 watt supergroup semi-recently, the LA30BL. They deliberately used an underpowered output transformer to produce subharmonic 'ghost' tones, which is part of the sound

I have one of these amps and can confirm that it weighs far less than a typical 30 watt tube head and that it produces subharmonics

If that's the effect you mean then it might be necessary to saturate a mini transformer and see what happens?

I know Thorpy uses a transformer in his Scarlett Tunic pedal, which is an emulation of a Selmer Treble & Bass front end, so that could be a good place to start in terms of topology

The Iommi sound is a modified rangemaster pushing the supergroup, you can probably get close by pushing a JTM style pedal with a treble booster. There might even be a circuit that combines these two things already
 
Thanks for the reply, really appreciate it!


Checked out the Laney LA30BL – that thing's definitely on my wishlist once the budget allows. Hope your enjoy yours!

I read that with older Laneys and Oranges, the power section – including the transformers – had a noticeable influence on the tone, which helped set them apart from Marshalls. Orange had a different preamp design too, if I’m not mistaken.
For now, I’m focusing on the preamp side, since I’d like to build one anyway. While researching, I read that the Bassman, JTM, and Supergroup circuits are all pretty similar. Since I’d ideally like a Supergroup-style preamp, I thought it might be easiest to take a Bassman- or JTM-based pedal and tweak a few component values to get closer. I’m not even sure how close they really are, or if it’s even necessary to mod a Bassman- or JTM-style pedal to get into Supergroup territory. Maybe they’re already close enough?
I’ve got a Naga Viper clone that I absolutely love, so the Rangemaster part of the Iommi setup is covered.
Also gonna check out the Scarlett Tunic – sounds like a really interesting circuit. Thanks again for the helpful tips!
 
The Catalinbread Sabbra Caddabra was designed specifically to ape the Supergroup + Rangemaster thing.
Otherwise, you can tweak the EAE Model Fet to Supergroup specs.
IIRC the Iommi setup on the early albums was:
Modified Rangemaster (almost full freq boost as opposed to treble) -> Bass channel of Laney Supergroup fully open -> Mid, Treble fully open and Bass completely off.
It should be fairly easy to remove the Bright channel, remove the source cap on the 2nd jfet stage and implement a fixed tonestack on the EAE 😜Personally, I'd change a few things on the phase inverter emulation and have it clip a bit harder, to match the Supergroup (The Model T has a different kind of power stage), but that's probably splitting hairs...
 
T

Thread 'The amazingly versatile Mofeta board'

After building my first Mofeta board and playing around with it and letting my bass player use it (and ultimately keep it), I decided to make a second one. I made provisions for a few tweaks but ended up using the stock components for that build as well. I have really enjoyed the different sounds that I can get from that pedal that are not the typical "Marshally/Fendery" type sounds. Still, I wanted to see how much further I could take it. I wanted MORE!

So I kept thinking about the schematic of the Mofeta board and realized that a 1987 Plexi has a simliar architecture. So I present to...
  • Like
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  • This ROCKS!
 
Diego said:
Hi everyone,

I’ve read that both the Marshall JTM/Plexi family and the Laney Supergroup are based on the Fender Bassman circuit. I'm unfortunately not very good at reading schematics, so as a Black Sabbath fan I was wondering:
Is it possible to recreate the Laney Supergroup sound using a Bassman- or JTM-style pedal, such as the PedalPCB Tweed Man OD or Covert OD?

If so, which component values would need to be changed to get closer to a Supergroup-style tone?



Thanks a lot for your help!
Diego
Click to expand...

Laney "Toney" Iommi Treblemaster IC-Boost:
www.pedalpcb.com

Dark Esbat Boost - PedalPCB.com

Compare to Black Country Customs TI-Boost
www.pedalpcb.com www.pedalpcb.com

Iommi's signature Black Sabbath tone — Rangemaster-style treble booster with a Laney Supergroup amp — was the goal of Catalinbread when designing the Sabbra Cadabra:
www.pedalpcb.com

Sabbath Distortion - PedalPCB.com

Compare to Catalinbread Sabbra Cadabra
www.pedalpcb.com www.pedalpcb.com

There are a few other vendors for the Sabbra circuit that you may wish to explore, see if they are better suited to your needs: Aion, ELS, GPCB... maybe a few more.



There are similarities, from what I've read, with the Sunn T circuit, with PCBs such as ELS' enabling either circuit to be build (Supergroup or Sunn T). ELS no longer offers the Super Trouper PCB, but the SUPER TROUPER BUILD DOC PDF gives you the schematic to adapt to another PCB or produce a vero/perf/PCB layout of your own.


Since you're interested specifically in copping Tony Iommi tones and the SuperGroup, I would suggest including that in the thread title, you might get better more-targeted hits from people in the know.
 
the tweed bassman was based on an example amplifier circuit in RCA's tube manuals. the jtm was copied from that bassman then the superlead plexi added the treble peaker to the "bright" channel and the supergroup and model t are based off of that.

oversimplified history aside, I wasn't aware the super trooper pcb was discontinued but I do happen to have a spare pcb.
 
Last edited:
Einzeln said:
[EMBED content="threa
Blackboarcult said:
The Catalinbread Sabbra Caddabra was designed specifically to ape the Supergroup + Rangemaster thing.
Otherwise, you can tweak the EAE Model Fet to Supergroup specs.
IIRC the Iommi setup on the early albums was:
Modified Rangemaster (almost full freq boost as opposed to treble) -> Bass channel of Laney Supergroup fully open -> Mid, Treble fully open and Bass completely off.
It should be fairly easy to remove the Bright channel, remove the source cap on the 2nd jfet stage and implement a fixed tonestack on the EAE 😜Personally, I'd change a few things on the phase inverter emulation and have it clip a bit harder, to match the Supergroup (The Model T has a different kind of power stage), but that's probably splitting hairs...
Click to expand...
Click to expand...
Thank you, that’s interesting!
I do know about the Catalinbread Sabbra Cadabra – cool pedal, but I always felt the control layout was a bit limited in terms of flexibility. Also, I thought it wasn’t an actual Supergroup preamp circuit, but more of a soundalike design – kind of like how the Acapulco Gold isn’t a true Sunn Model T preamp either, just inspired by it.
To be honest, thinking about the phase inverter and transformer stuff is a bit too much for me – I’m really just scratching the surface when it comes to building pedals. For now, I’m mostly trying to get close using preamp-style circuits and see where that gets me.
 
Einzeln said:
T

Thread 'The amazingly versatile Mofeta board'

After building my first Mofeta board and playing around with it and letting my bass player use it (and ultimately keep it), I decided to make a second one. I made provisions for a few tweaks but ended up using the stock components for that build as well. I have really enjoyed the different sounds that I can get from that pedal that are not the typical "Marshally/Fendery" type sounds. Still, I wanted to see how much further I could take it. I wanted MORE!

So I kept thinking about the schematic of the Mofeta board and realized that a 1987 Plexi has a simliar architecture. So I present to...
  • Like
  • Love
  • This ROCKS!
Click to expand...
Alright, that’s kind of what I want to do – identify the component values in a pedal that differ from the Supergroup and change them. Not looking to recreate the whole amp, just get in the ballpark with a preamp-style circuit.
Thanks for the example! I actually saw it before but stopped reading when I saw “Sunn T” mentioned – stupidly, I guess…
 
Feral Feline said:
Laney "Toney" Iommi Treblemaster IC-Boost:
www.pedalpcb.com

Dark Esbat Boost - PedalPCB.com

Compare to Black Country Customs TI-Boost
www.pedalpcb.com www.pedalpcb.com

Iommi's signature Black Sabbath tone — Rangemaster-style treble booster with a Laney Supergroup amp — was the goal of Catalinbread when designing the Sabbra Cadabra:
www.pedalpcb.com

Sabbath Distortion - PedalPCB.com

Compare to Catalinbread Sabbra Cadabra
www.pedalpcb.com www.pedalpcb.com

There are a few other vendors for the Sabbra circuit that you may wish to explore, see if they are better suited to your needs: Aion, ELS, GPCB... maybe a few more.



There are similarities, from what I've read, with the Sunn T circuit, with PCBs such as ELS' enabling either circuit to be build (Supergroup or Sunn T). ELS no longer offers the Super Trouper PCB, but the SUPER TROUPER BUILD DOC PDF gives you the schematic to adapt to another PCB or produce a vero/perf/PCB layout of your own.


Since you're interested specifically in copping Tony Iommi tones and the SuperGroup, I would suggest including that in the thread title, you might get better more-targeted hits from people in the know.
Click to expand...
Thanks for that resource!
You are right, that would be catchier, but actually I want to built a preamp in the ballpark of those vintage amps and since I found out the Supergroup is very very close and i am a Sabbath fan I want to build the Laney ;)
 
Diego said:
Thanks for that resource!
You are right, that would be catchier, but actually I want to built a preamp in the ballpark of those vintage amps and since I found out the Supergroup is very very close and i am a Sabbath fan I want to build the Laney ;)
Click to expand...

Maybe re-read all of my post, follow the links, ELS in particular.
 
ICTRock said:
the tweed bassman was based on an example amplifier circuit in RCA's tube manuals. the jtm was copied from that bassman then the superlead plexi added the treble peaker to the "bright" channel and the supergroup and model t are based off of that.

oversimplified history aside, I wasn't aware the super trooper pcb was discontinued but I do happen to have a space pcb.
Click to expand...
That is some nice insight!
 
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