Adding compression / sustain

[islandamp]

I built a small amp years ago and have played it daily over all the high priced boutique amps that have come and gone. My only complaint is that the od is ratty if turned up to high and I would love to have more sustain and comp. without changing the clean tone. I have a 2nd preamp tube socket on the chassis and could wire in another tube, but I don't want to hurt my clean sound any. It's basically an original champ circuit with 2 stroke mods here and there. Any advice on wiring the 2nd tube to sweeten things up. Thanks..

[sliberty]

What circuit did you use? A schematic would be helpful. Otherwise none of us will know where to begin making suggestions.

[Reeltarded]

And pictures even better. It could be a simple lead dress issue if it's a common circuit with unexpected results.

Ratty might also be expectation based on prior experience. Happens to me lots of times.

[73GTV]

I built a small amp years ago and have played it daily over all the high priced boutique amps that have come and gone. My only complaint is that the od is ratty if turned up to high and I would love to have more sustain and comp. without changing the clean tone. I have a 2nd preamp tube socket on the chassis and could wire in another tube, but I don't want to hurt my clean sound any. It's basically an original champ circuit with 2 stroke mods here and there. Any advice on wiring the 2nd tube to sweeten things up. Thanks..

Man, I'm about half way through Merlin Blencowe's book: Designing Tube Preamps for Guitar and Bass and would suggest it for any modifications on any amplifier. Well worth the funds investment....Oh, forgive me, this isn't the book review section, sorry for my creative post. (But it will explain how to get more from your present amp circuit, and even how to keep that clean tone you like so much!)

[islandamp]

It's an early Fender Champ schematic, not sure what the 1st year Champ was called, but this is it. Sounds great, but could use a little more compression and sustain to make it perfect. Just looking to add a 2nd preamp tube, with maybe high plate resistances, 220k, and no real added gain, just sustain.

[sliberty]

5C1?

6SJ7, 6V6, 5Y3?

[islandamp]

Well, maybe not a 5c1,,,Its an early Champ with a 12ax7. Really just need a 2nd 12ax7 stage that produces sustain with minimal tone coloration..

[sliberty]

Help us help you. Show us the schematic you used.

[brewdude]

It seems that you want pre amp distortion on an amp that's all about power tube overdrive. It can be a challenge to get what you are hoping for in a small single ended format without the tone getting muddied.

I built a SE amp in a Valve Junior that uses a parallelled 12AX7 front end into a 6SJ7 pentode with a 6V6. The screen voltage on the 6SJ7 has a huge effect on the compression. Perhaps you could use a pentode second stage in similar manner.

[islandamp]

I might try a pentode, but I thought maybe a 2nd 12ax7 tube could be used as a cathode follower and a gain stage with very little extra gain, using a high plate voltage resistor. I don't want to change the tone, just add more sustain. Playing it at 5 or so on the volume is next to perfect. Anything beyond that does the usual Champ thing and gets a little hairy. It's a Champ schematic. Might have a few r and c changes over the 6-7 times I've rebuilt it, but still, just a Champ. Started as a 5a2f, went to a 5f1, then a 2 stroke, then back to an early style Champ. Just really sings with the transformers and Weber alnico 2x10 cab. I wouldn't mind a little more preamp distortion, but mainly, a little more sustain. I may add a dropping resistor, to ground, before the power tube and actually dump some of that p.t. distortion. Last night I actually ran a split cable to the Champ, with bass turned down, and to a 50watt higain amp that I built, with the treble and mids turned down. Damn, that little Champ screamed when it only had the treble to deal with.

[brewdude]

Is seems that you already have a plan. Give it a try and let us know how it turns out.

[cbass]

A guitar with hotter pickups

[dobbhill]

Local feedback loop on first gain stage like Dumble ODS might add just enough "squash" for you.
My personal issue with Champs is the output transformer: no assitol....
D

[Phil_S]

A guitar with hotter pickups

Yeah, P90's or a pedal!

[islandamp]

I might try the local feedback, just use a jumper and a resistor to test it, this weekend. I,ve owned Carrs, Velocette, and about every other amp made over the past 15 years and this amp sends em all to Ebay. It doesn't do well with pedals or equalizers. They all seem to dull it's natural chime and bloom. I,ve put it beside 2 or 3 vintage Champs, and a 70's Vibrochamp, and it smoked em. Just the right combination of cheap transformers and luck, I guess. It sounds best with an El34, and the volume at 4-5. Just a bit of compression, and preamp distortion, natural, because my compression pedal sounds horrible, and it can nail Vintage Zep. classics.