TSL60 Signal Flow

[Dylpickle]

Hey Guys,

I'm currently looking at getting my amp (Marshall TSL60) modded and I am trying to understand the gain stages and how they flow through the amp. I have some basic experience with reading schematics and how they work (Mainly pedals and other simple circuits) but this birds nest is a bit out of my league.

As i understand it (Correctly or incorrectly) the channels have a flow like this.

Clean: V1(a) -> V3(a&b) - V4(a&b) -> EL34s
Crunch: V1(a&b) -> V3(a&b) - V4(a&b) -> EL34s
Lead: V1(a&b) -> V2(a&b) -> V3(a&b) - V4(a&b) -> EL34s

As I understand it both V1 & V2 are used as gain stages.

I promise I wont go digging through and play with HV as I'm not confident enough to do so. This is just really for my curiosity on how the amp creates it tones and how changes in preamp tubes can change different channels.

I have linked a copy of the schematic HERE is anyone is able to help.

Is anyone able to confirm or correct my thoughts?

Thanks,

Dylan

[g1]

Seeing as this is your first post, I'll tell you this so you don't think you are being ignored.
No one wants to look at schematics for those types of marshall circuits because of the way the connectors are drawn. It's very hard to follow the signal unless you have a lot of time to spare. If you get lucky, you might find someone who is very familiar with this model that could help you.
Meanwhile, here is what someone said about which part of which tubes do what:
http://www.marshallforum.com/threads.../#post-1693422

[Dylpickle]

Hi mate,

Thanks for the reply. I glad its not just me who finds these connectors an absolute bugger to navigate through. Thanks for the link. I'll have a look deeper into it and see what i can decipher.

Cheers

[DrGonz78]

Totally agree with G1's post. Nobody wants to look at these convoluted schematics that Marshall drew up for the JCM 2000 line of amps. That said... there is still something that has not been done, I think. You could try to draw up a preamp arrangement that ignores board arrangement. Might be a challenge but I for one would like to see a drawing that keeps things on one page.

Also, I sort of lumped all the JCM2000 line together in my statement above. Actually the JCM2000 DSL 401 schematic was okay. It's the models in the JCM2000 line up with 6+ different circuit boards that really made the schematics suck.

[Pedro Vecino]

According to what I interpret it would be:

V1a - Common all channels
V1b - Ch2/3
V2a - Ch2/3
V2b - Common all channels
v3ab - Cathode follower. Common all channels
v4ab - Phase splitter

[Dylpickle]

Thanks Guys,

I'm going through the circuit one by one right now to see what else pops up.

Cheers,

[Pedro Vecino]

Itīs very possible that channels 2 and 3 are identical except for two details:

- the assignment of C73 for channel 3.
- different value in the gain potentiometers: 1M for channel 3 and 200K for channel 2.

It also seems to match with particularities and balance between these two channels (guitar in hand).

[Dylpickle]

yeah it's interesting you say that because thats the conclusion i was coming to.

I assume the larger pot value just allows more gain to be dialed in with the preamp? (So a lower value pot might decrease the gain on tap)