Crate V5 mods... anyone?

[goonrick]

Hello all, new to the board. Great discussion here on this little amp.

My question is, what could we expect if we simply did away with the opamp section and made it all-tube. There's still tons to change out in the tube sectioin (moving the volume after the tone control, tweaking the cathode bias resistor, et al).

Since I normally get my drive from a stompbox, what could I expect were I to simply mod R1 and R2 values and jumper over from where R10 used to be?...

[jim p]

The idea of just jumpering past the op amp in basic form just remove R2 and C25 jumper from R 11 to R1 would still need a volume pot. Without adding a volume control the input level will be the volume not sure you will like that. If you want to throw away the volume pot or use it as gain pot you can convert the tone pot to a volume pot then have no tone control.

[jim p]

If you convert the B+ supply to a choke input filter by removing C14 this will drop the supply voltage down to approx 275 volts. I would not mess with R24 it is just in the amp to pull the supply down with power off to help prevent death due to shock. So the change would be to cut the positive of C14 out and connect it to the positive side of C15.

[goonrick]

If you convert the B+ supply to a choke input filter by removing C14 this will drop the supply voltage down to approx 275 volts. I would not mess with R24 it is just in the amp to pull the supply down with power off to help prevent death due to shock. So the change would be to cut the positive of C14 out and connect it to the positive side of C15.

Effectively placing C14 in parallel with C15 after the choke, right? I just want to be perfectly clear before I start hacking on this little amp.

[jim p]

Yes you will be paralleling C15 with C14 a switch instead might be neat you would get two power output levels.

[goonrick]

Thanks, Jim. You're a wealth of information.

[jim p]

The screen grid resistor is attached to the wrong location on the PCB it should be on the other side of R25 (junction R25 R26 and C16). This will lower the screen grid voltage closer to (right at) its maximum rating of 300 volts. Best if you have the pcb out is to also replace R25 with a 7.5 to 10 k ohm resistor (approx 4ma across R25).

[goonrick]

The idea of just jumpering past the op amp in basic form just remove R2 and C25 jumper from R 11 to R1 would still need a volume pot. Without adding a volume control the input level will be the volume not sure you will like that. If you want to throw away the volume pot or use it as gain pot you can convert the tone pot to a volume pot then have no tone control.

Yeah, I would still put the volume pot in place of R15 and R27. What would you imagine the tone control being like if left alone, spare swapping C28 out for a smaller cap?