Solo boost

[tsl602000]

Hi all,
I'm building an amp for a friend of mine and he wants an internal boost in his amp for solo's. So, not a volume boost, but a gain boost. pretty much like what you'd get if you put a tubescreamer or any other drive pedal in front of your amp.
Can anyone point me to a schematic I could use? I'd prefer to make it a tube boost. I got a 12AX7 slot open....

thanks,
Coen

[ic-racer]

Hi all,
I'm building an amp for a friend of mine and he wants an internal boost in his amp for solo's. So, not a volume boost, but a gain boost. pretty much like what you'd get if you put a tubescreamer or any other drive pedal in front of your amp.
Can anyone point me to a schematic I could use? I'd prefer to make it a tube boost. I got a 12AX7 slot open....

thanks,
Coen

Dumble Overdrive will fit one tube.

My Fender Super Twin Reverb project started as just that: add a distortion/gain from a single free 12AX7 slot. It sounded good, so I went ahead and did the 'full course' Dumble conversion with relays and tone stack changes etc.

http://ampgarage.com/forum/viewtopic.ph ... highlight=

[tsl602000]

thanks for your reply, but I'm definately not looking for a PAB. I just want a switchable booster right in front of the pre-amp.

[Andy Le Blanc]

old mesa\boogie studio .22 caliber and studio .50 caliber took that general
approach..... but they also switched values back thru the rest of the pre to
smooth out transitions using the same stages for both modes.... but if all
your after really is a simple boost...... a simplified circuit based on that example
might bear fruit....

[skyboltone]

thanks for your reply, but I'm definately not looking for a PAB. I just want a switchable booster right in front of the pre-amp.

That's not what he described.

[ampgeek]

You may also want to check out a Marshall JCM 800 type approach. If I remember correctly, the 2204 "HI" input throws another 1/2 of a 12AX7 into the front of the pre-amp.

You could make it foot switchable with a relay voltage source (e.g., 5 V recto heater winding or off of the 6 V winding) and enough real estate.

Good luck,
Dave O.

[ic-racer]

thanks for your reply, but I'm definately not looking for a PAB. I just want a switchable booster right in front of the pre-amp.

Here is the basic Dumble Overdrive circuit (as pointed out, the PAB is something different). It is pretty simple and effective. True, it goes AFTER the preamp. Perhaps the best thing for IN FRONT of the preamp might be a pedal!

[Abstract]

You say he wants a gain boost, not a volume boost. Then you say you want it in front of the preamp.

ic-racer's right. That's a pedal.

[lastwinj]

halve the bottom resistors of the voltage dividers between the gain stages. should allow a gain boost, when switched back to stock. or beef up the amount of gain, then do the same thing.

i did this for one preamp, 3 stage, only on the 2nd gain stage voltage divider. worked pretty good.

you could also wire in a pot to adjust the amount of attenuation when in/out, however you want to switch it, NO or NC. a vactrol can work well here, too. just adjust the current limit resistor for desired resistance, with the vactrol across another resistor.

germ

[tsl602000]

Thanks for your suggestions. I found a schemo at Hoffmanamps.com that looks promising.

What would be the best way to have a footswitchable volume boost?
The guy now wants a gain and a volume boost...

[Funkalicousgroove]

with a relay and another volume pot

[tsl602000]

with a relay and another volume pot

Yeah, I kinda figured that out, but what would be the best location? after the FX loop or a 2nd MV? I have a PPIMV with a dual ganged pot.

[tsl602000]

I decided I want two master volumes. I'm using the "rich mod" PPIMV. How do I make two dual ganged pots switchable with a relais?

edit: I realize I'd need a 5PDT relais for that. This amp has an FX loop, so wouldn't it be easier to add a switchable pot in the loop?

[rfgordon]

A truly simple boost is to lift the ground side of one of gain stage's cathode bypass cap and connect it (on the back panel is where I do it) to a 1k linear pot to ground via a footswitch jack. This allows the user to dial in exactly how big the boost is when the cap is switched back into the circuit.

This is a great trick with old Fender amps whose users just leave the reverb on full time--use the tip lead of the jack for the boost instead of the reverb.

[Vince]

Hi all,
I'm building an amp for a friend of mine and he wants an internal boost in his amp for solo's. So, not a volume boost, but a gain boost. [..]

For something I call "solo boost" you can try
bypass tone stack by cap beetween 2000-5000pF.
I did it many times, footswitchable and it work nice.
Gain boost - not so big and fatter tone.

regards
V.