Help ! My 18 watt needs more preamp gain! Calling all Gurus

[crunchman]

I have a 18 watt that really sounds quite good but really needs to be cranked to get "in the zone" I was wondering if I could mellow out the poweramp and increase the preamp gain by substituting some cap/resistor values.Its a pcb amp so I realise my options may be limited, Heres the link to the schem, its at the bottom of the pdf.

http://mysite.verizon.net/resqaaya/t...v_2_N_v1.6.pdf

I'd like to get it into a tiny terror type tone if possible, much thanks !!

[Jazz P Bass]

First off. How do you know where the "zone" is?
The preamp?
The power section?
Maybe it is a synergy thing & it is both.
Anyway.
It looks like the first preamp tube is dedicated to either input.
Input #1, side A.
Input #2, side B.
Maybe you can try to work up a "Y" cord & jumper the two jacks.
And/ or you could try a lower gain tube in the phase inverter

[olddawg]

Have you tried simply using a OD pedal like a Tube Screamer or a Bad Monkey? I use an 18 watt Marshall clone quite a bit myself. They take pedals well. I use a Bad Monkey and a Rat on top of that to go really over the top. You could parallel or cascade the inputs. But why? Seriously, try an OD pedal first. It will push the amp into saturation just as well.

[crunchman]

First off. How do you know where the "zone" is?
The preamp?
The power section?
Maybe it is a synergy thing & it is both.
Anyway.
It looks like the first preamp tube is dedicated to either input.
Input #1, side A.
Input #2, side B.
Maybe you can try to work up a "Y" cord & jumper the two jacks.
And/ or you could try a lower gain tube in the phase inverter

jazzy, I agree with the synergy statement, these 18's are predom. power tube which is good, but loud to get there.I thought about the y-cord and will try it!!.....Thanks

O.D. - I have a Barber DD I run into it with some luck, still not what I'm looking for, I'm a P.I.A. tonewise, gonna try a y-cord and 5751/12aT7 in the P.I. and see....Thanks !!

[Chuck H]

Check out the simple attenuator I suggested here:

http://music-electronics-forum.com/t16468/

It's a simple resistive load but it works very well and could even be mounted on an aluminum plate in the back of the amp.

Chuck

[mooreamps]

I have a 18 watt that really sounds quite good but really needs to be cranked to get "in the zone" I was wondering if I could mellow out the poweramp and increase the preamp gain by substituting some cap/resistor values.Its a pcb amp so I realise my options may be limited, Heres the link to the schem, its at the bottom of the pdf.

http://mysite.verizon.net/resqaaya/t...v_2_N_v1.6.pdf

I'd like to get it into a tiny terror type tone if possible, much thanks !!

They only give you 2 tubes for the pre-amp ; and one of them is the phase splitter. It would take more than just a cap or resistor trick to pull any more out of it.
I have a friend who likes the Mesa V-Twin to drive his Fender amp. That would be my first thought.

-g

[pdf64]

Put a simple L Pad attenuator between the OT and speaker, a 50 watt type is good for 5E3 / 18 watt type power levels.
See
L-Pad Attenuator 50 Watt 8 Ohm Wirewound on eBay (end time 08-Nov-10 11:24:05 GMT)
When turned very low, the tone loses definition etc, but for making these amps a bit more domestic friendly, shaving 6 to 12 dB off the ear splitting sound level that they're are capable of, L Pads are a great solution for getting power tube overdrive at home.
For this application, the L Pad should be rated for at least twice the amps power.
The great thing about them is that when turned up full, they're out of the circuit, so they can be a permanent fixture. Give them plenty of ventilation for heat dissipation though - probably best out of the main amp chassis.

Edit - sorry, check schematic first! It already has a power scaling circuit. For more gain, then a pedal will be the simplest solution. The 2 sections of the pre-amp could be cascaded, but mods are a bit awkward to do on a PCB amp.

[Chuck H]

Ah yes, It does. I didn't look at the schem in the first post either. The need to crank the amp to "get it in the zone" threw me. So I have to assume it's a volume thing and not a distortion thing then. So what the OP wants is more volume but at a lower volume. Er, hmmm.