Tweaking an amp

[wicker]

I heaven't, for some time I had 4k7/470ohm but VacuumVoodoo sugested me to use 4k7 instead of 470ohm, so I've changed 4k7 to 47k (also tried 100k but prefered 47k).

[wicker]

Ok, changed mid cap to 47n (Fenderish tonestack), PI resistor to 100k/82k (1W enough ?) and 220k from bias, now there's 20M i local NF and the sound is damn good, but the problem that I found is that the buzz increased really much.

[Structo]

What kind of buzz?

60Hz or 120Hz?

[wicker]

Well, with Reverb level on max there's a small 50Hz, but increasing volume makes more higher freq hiss when volume is nearly max 8.5-9 very high hiss occurs, hard to describe for me, I'll post some pictures tommorow, maybe that's because of using straight wire in preamp heaters like in soldano, but I have a feeling that's not this.
Btw. I've changed V1B Rk to 81k and 1k cathode (ain't no 1.2k), added 220p cap beetween V1A anode-cathode, and chagned mid cap in eq to 47n so it's standard Fender eq, the amp sound really great. If it weren't for this buzz and hiss issue, I would probably say it finished.

[wicker]

The amp is probably not very beautiful, but I think it's not that bad. All brown wires are grounds, PS i connected with preamp a the place where 4.7k PI res is connected to the ground, then the preamp is grunded at input jack, the same are pots, 6L6 cathodes are connected to ground at 4ohm output jack, and the 3rd ground connection is near power switch - shield of PT, + od bias and PT bias tap.

[Structo]

Looks like a pretty cramped chassis.

My guess is a lead dress problem due to the close proximity of everything.

For instance, what is that bundle of yellow wires that are tied together that go from the board to the tone stack?

Also the heater wiring unless done very well will most likely hum with the straight wiring like that.

Twisting the heater wires cancels out hum.
That amp would be a good candidate for overhead heater wiring.

[wicker]

Well, it's quite small chassis as for this kind of build, but in fact not really smaller than regular D amp, it's 450x200x60 mm (~17.5x7.9x2.4 inch).
This yellow wires connects pots to their caps on eq, those wires between 3rd i 4th preamp tubes comes from Treble and Reverb pots and goes to 220k mix resistors, there's also wire that goes from PI coupling res to presence pot.
I did used traight wire, cos I've seen this in Soldano, and I'm sure that if it works there, it should in low gain amp (or am I wrong ?). I think that problem is in 1st stage mainly, maybe I'll try to cut heaters wire and use twisted one only for 1st stage (yeah, I'm lazy to rewire all heaters).

[Structo]

I think if you want to do the Soldano method the flying leads from the board should go over the heater wires.

So over then straight down to the pins.

You 60Hz wires there so you don't want any grid wires near those.

[wicker]

I'll try to mod the wiring, btw. here's a photo how does it look 'outside'

[Structo]

Nice faceplate!

[wicker]

Thanks, it is really nice, one of the best thing in this amp
I must say that I'm not really happy how does the amp look inside, I did my best, but it's still behind many amps that are shown here, I can only say, that when I'll finish amp, I'll probably strat thinking of another build, this time ~20W (2x6V6) combo to have more handy practise/small gigs amp.

[wicker]

Well, I have changed heaters wiring to twisted wire, shorted some other wires, leads from board goes over heater wires, soldered grounding of power supply to bias pot and now it's better, but still some problem, it's quiet untill 12 oclock or so, when volume is set max, you can hear a small hiss.

[Structo]

That is pretty normal.

[wicker]

My intention is to make is quiet when volume is set max.

[mlp-mx6]

My intention is to make is quiet when volume is set max.

Then you might not want a tube guitar amp.