buzzy little guitar amp(18 watt clone)

[nyazzip]

my first shot at point to point. i began the power section pretty nice and neat, and as i progressed, craftsmanship just totally went out the window. it buzzes horribly at the moment. component leads were left long before "do you want to finalize disc?"

edit: i should add that the central tube socket is not in use, just used as a tag strip!

[dcgillespie]

One thing that would cause the buzz that I'm not "obviously" seeing is some kind of reference for the heater supplies to ground.

It looks like you are using two windings for the audio tubes, but I don't see any center taps offered on the power transformer for these windings, nor do I see any hum balance control or balancing resistors for either winding. If you simply grounded one side of these heater systems, that will certainly provide the reference, but usually cause a hum or buzz as well when sensitive circuits are present.

Just a thought. Good luck with it!

Dave

[nyazzip]

when i stripped this amp i left the heaters wired as they were done in the factory, 55 years ago, and i never even gave them a thought. now that i look at them they are pretty wacky....probably at risk of overloading the 1.6amp winding too....
its a bummer to have to reassign the wires at this juncture, but it needs to be done. and yes, i guess they have no ground reference.
but were talking a serious, angry buzz here(sharp and trebley sounding, not muffled/muted) so i suspect bad input section grounding as well.
but under all that nois it really sounds great and responsive, so i am encouraged to press on. thanks for looking

[Gingertube]

Heater balance resistors to ground (or to an elevated DC potential but AC ground) should be fitted routinely on all builds. If you don't the most common symptom is a "seriously angry buzz". I had this in my last HIFI Power Amp build - 100 Ohms from each heater wire to 0V cured it.
Cheers,
Ian

[nyazzip]

i tweaked around and got it considerably quieter. i consolidated ground points, discovered one ground loop, referenced the power tube heaters to their cathodes via 100R resistors, and lastly i DC rectified the preamp heaters using 1N 4004 diodes into a 1000uF cap. still not quiet but there are more things i can do yet, such as enclose the circuitry a bit. problem is the DC filaments are nearly a volt lower than the power filaments now...so i will probably do the whole thing DC. i never even looked up the 1N 4004 for spec but i will now...just using mostly salvaged parts on hand

[nyazzip]

another Lafayette carcass, with a Voice of Music OPT: