Supro 1624

[gary sanders]

Just built one of these and it sounds great.Only issue is it breaks up way to soon,like around 2 or 3.Ive never played a real one,is this how these amps work or could I do something to keep it cleaner till I get to around 50% volume.Ive also heard the gain is higher without the tremolo,I havent done the tremolo circuit yet

[electrochimp]

is that supposed to be a 250R on the cathode power tubes?

[xtian]

Haven't played one. But by the looks of the Ra and Rk values of the preamps, it's a crunch machine.

If you have an 12AT7 or 12AY7 you could try that in V1.

Or you could change values of V1 to fender style, 100K/1K5.

[tubeswell]

Just built one of these and it sounds great.Only issue is it breaks up way to soon,like around 2 or 3.Ive never played a real one,is this how these amps work or could I do something to keep it cleaner till I get to around 50% volume.Ive also heard the gain is higher without the tremolo,I havent done the tremolo circuit yet

Bypass one or both of the 100k supply resistors that are in the power rail for the pre-amp (after the 15k supply resistor). That will get the pre-amp HT voltages up and make for more headroom.

Either that or decrease the resistance for those supply resistors (e.g.; by putting another 100k (or 47k) in parallel with each/either of the 100k). Over to you to experiment a little.

Note that if you bypass the 100k completely, you will effectively have 10.1uF at the pre-amp filter supply node (because each of the 0.05uF will be in parallel with the 10uF). But if you're merely going to lower the resistances of each/either of the 100k, you may want to consider replacing the respective 0.05uF with beefier (say 10uF) filter caps to get better filtering - which will also help with the headroom. Over to you.

[rock_mumbles]

I built an SE EL84 variation ... it was really dark and really dirty

Without the tremolo circuit, the tremolo channel input cathode is messed up.

The 1.5k cathode resistor bypassed with the 35uf cap is supposed to be shared by two triodes ... for a single triode the resistor should be twice the value and the cap 1/2 the value

Try replacing the 1.5k resistor with a 2.7k (or 3.3k) resistor ... once I did that to my SE amp it was really nice.