Re: changing values on traynor - help
Alright, I'll see what I can do to help, actually if you can post some rather close up pics of the guts of the amp I could be more specific based on what I see, like I said they changed the circuit quite a bit over the years.
1. I would change the tone stack to use a 33k slope resistor and a 500pf treble cap, the 33k should help to make the tone controls a bit more responsive as it will let some more signal through. My amp had a 1000pf treble cap stock, that is waaay too much imo, 500pf is just about right, anything close should work, I think I used a 510pf because it's what I had on hand. I would use a silver mica cap for the the treble cap, the ceramics can sound too gritty but that's all a matter of taste. If you have access to a carbon comp resistor for the slope resistor that can be a good place for one, if they're used in the right places in the circuit they have some nice vintage mojo, any resistor of the right value will be fine though, I wouldn't get too hung up on those details, you can always try different brands and types of resistors and caps later after you find the values you like.
2. The one meg pots for the volumes make a big difference, the 4meg pots that are stock are too spongy for my taste, you can change one at a time to see which you like better. I didn't play with bright caps because I didn't feel the need for them but kevlar3000's advice was good, that should get you where you want to go. Also if you decide that you want a master volume the simple "one wire" master worked great for me, it's really easy and all it takes is a 1meg pot and 1 piece of wire. The post phase inverter master that everyone hypes up didn't do too much for me on the traynor plus it will really screw with the way your presence works because of it's effect on the feedback loop.
3. For the negative feedback resistor I would just try piggy backing another 100k across the 100k thats in place, this will give you 50k and that will be just about the same as a 47k, resistors have a tolerance and there's plenty of 47k's out there that will measure 50k plus. Lowering the negative feedback resistor will make the presence much more responsive, there's simply more negative feedback for it to work with. With the nfb resistor change and the tonestack changes your controls should do alot more. Also if you increase the value of the cap on the presence pot it will make it effect more frequencies, increasing the value will make it start boosting upper mids along with the highs. I like using another .1 piggybacked across the stock one, this makes it boost a liitle more than just the very top end but still keeps it in the treble range, you can really fine tune your top end by using the right cap here.
I would try those things first, it wouldn't hurt to change the electrolitic caps in the amp, especially the ones in the bias supply they should be two 8uf caps, that value can be hard to find but 10uf is easier and they'll be just fine as long as they're high enough voltage. The two big filter caps sticking up from the chassis could probably use changing too(if your amp has them mounted there, they may be inside) if they're the big metal 40uf/40uf mallory cans they can be a major pain to change as they're soldered directly to the chassis, I couldn't get the 30+ year old solder holding them to melt, I had to cut them out. I used f&t 50/50uf to replace them and it really helped quiet alot of the background hum but if your amp doesn't hum much now I'd leave em in place, they're good caps and like I said alot of work to replace. I would change the bias caps for reliability though. Mine was identical on both channels aside from the bright cap but who knows what yours has, it's quite easy to change the cathode resistor and cathode bypass caps though, using the 820ohm/330uf and 2.7k/.68uf like an old marshall will give you a darker and meatier sound on one channel input and a brighter crunchier sound on the other, or you can jumper them and blend both to taste with the volume controls. I actually liked a 220uf or smaller cap for the 820ohm cathode though, 330uf is kinda overkill but it may suit you fine. You may just leave one channel as is and try the 2.7k/.68uf lead channel on the other, the stock would be closer sounding to the lower gain channel on a plexi.
See where that stuff gets you, I'll be happy to help you more if you need it, good luck and make sure you know how to drain those caps or you could get a shock that could kill you or make you wish it had. And pictures of the insides woud be great too, all I can do is kinda speculate as hardly any two from that era are the same.
