Help with Engl screamer schematic.

[Rod]

Hi everyone!

I need some help with the attached schematic.

This amp has two channels and two modes for each channel low and high gain(lo-Hi), so in channel one i have clean, and if i press the lo-hi button, the crunch is activated.
In channel 2 i have a lead channel, and if i press the lo-hi button in this channel i have even more gain.


my first question is, what is the gain stage activated and deactivated, when i hit the lo-hi button, in the clean channel and in the lead channel?

Well i'm also trying to see what is the signal path for each channel. so correct me if i'm wrong.

clean, lo gain - V1A ->V2B -> tone stack -> effets loop -> poweramp
Clean, hi gain - V1A->V1B??? -> tone stack -> effets loop -> poweramp, this path could be wrong here right?
Lead, lo gain - V1A->V1B->V2B??->tone stack->effets loop -> poweramp, is this correct?
Lead, hi gain - V1A->V1B->V2A->V2B->tone stack->effets loop -> poweramp, is this also correct?

Thanks.

[mozwell]

clean, lo gain V1A - V2B - tone stack etc
clean, hi gain V1A - V2A (through R20, R6, R17, R58) - V2B - tone stack etc
lead, lo gain V1A - V1B - V2B - tone stack etc
lead, hi gain V1A - V1B - V2A - V2B - tone stack etc

The resistor R20 threw me for a minute, i guess its easy to miss that one

The lo - hi switch selects the input to V2B, and also switches in a resitor divider R22 / R28

Quite a neat arrangement of switches to get the 4 modes, but it would be good to be able to switch clean & lead with & without hi / low gain separately, ie have a 4 switch footswitch, guess you could do that through the 9 pin connector X1, but you would need a custom footswitch, should be easy enough to work out though

Hope this helps

[Rod]

Hi mozwell!

Thanks, i also did miss that R20, resistor.

Yes with this amp, all that 4 modes are switchable trough the footswitch.

[Rod]

I'm going try to mod this amp because it has some harsh highs, and it lack some low mids.

To do this i was thinking to put a capacitor in parallel with r7 or r14 to filter some highs, or maybe remove CE1 or CE2.
But i dont know how to add some low mids.

What would you recommend me to do?

[Amp Kat]

I'm going try to mod this amp because it has some harsh highs, and it lack some low mids.

To do this i was thinking to put a capacitor in parallel with r7 or r14 to filter some highs, or maybe remove CE1 or CE2.
But i dont know how to add some low mids.

What would you recommend me to do?

The mids on the tone stack are already pretty low at .047 uf but there is also a lot of frequency shaping in this amp causing lots of highs. The 1st thing I would do is see if those 5881 power tubes are Sovtek WXT 5881 and if so I would get them outta there because that is a very harsh military grade tube. If 6L6's will fit I would use them instead as you will get a much more defined low end and midrange with them. You could try changing the tone stack cap to 250pf and maybe C14 to .1uf but imo doing changes to midband components will cause other ill effects later down the signal chain.

[soundguruman]

I recommend you download and install this:
Download
No it's not a virus, it's the tone stack calculator.