Mesa Boogie BlueAngel Preamp - What is doing V1b ???

[kagliostro]

May be this evening I'm tired, I'm not able to read correctly the schematic of Mesa Boogie BlueAngel preamp

What is doing there V1b  

is the schematic missing something or my brain at the moment is out of service ??

I can see the signal coming from V1a entering in V1b, but from where the signal go out from V1b ??

Many Thanks for any explanation about

K

[jim]

That is a cathode follower.  It doesn't pass signal --as I understand it offers current amplification and lowers impedance for driving a tone stack and other stages.  Look at the huge size of the cathode resistor, and the plate is connected directly to the power supply.  I've never experimented with one.

Jim

[sluckey]

Yes, it's a cathode follower. But the cathode output is not used. I suspect V1B is there because the engineers thought it would be nice to have the option of using a cathode driven tonestack or a plate driven tonestack. Looks like they decided to use the plate driven tonestack and just left the cathode follower wired up. It's doing nothing, but it ain't hurting anything either. That's the second wasted tube I've seen in a Messy. I'll bet it's part of the charm. 

[kagliostro]

I just noticed that on the faceplate of that amp there is a Bright/Fat switch that I didn't see on the schematic

is possible that is connected or to the plate of V1a or to the cathode of V1b (than to the next stage) ?

K

[tubenit]

Perhaps the schematic is not drawn correctly?

Tubenit

[sluckey]

I just noticed that on the faceplate of that amp there is a Bright/Fat switch that I didn't see on the schematic

I see it.

[kagliostro]

As suggested in one other forum, may be there is a mistake on the schematic

see the MB Maverick preamp

K

[sluckey]

Ahhh, that bright/fat switch.

Switch between plate driven or cathode driven TS.

[kagliostro]

Switch between plate driven or cathode driven TS

Yes, as in the faceplate there is only one switch, may be that it acts at the same time the switch between plate or cathode and the switch on the Tonestack (see Blue Angel TS)

K