need help, tube amp problem

[km-r]

hey
i built my first tube amp, a clone of the valve junior. i used NOS tubes, tirgon 12ax7 and philips/mullard el84. no new tubes here.
and a SE OPT salvaged from an old radio that i presumed to have been used with an el84 because when i fed 4vac to the secondary, around 100~120vac was seen in the primary. like a 5k to 8ohm tranny, iirc.

when i powered it up, i used a low-ish voltage of 120vac [160v-ish rectified].
problem was the sound was gated with lots of farting sound when chords are hit. totally useless.
it sounded like an overly misbiased fet circuit.

i tried isolating the problem so i tried feeding music to to the input of the el84 [12ax7 removed].
the volume was very low since my mp3 player didnt have enough voltage drive. the music was sounding OK just that the volume was not high enough.

the 12ax7 preamp stage was also fine, i plugged my guitar in front of it and tapped the signal at the input of the el84 [el84 removed] then attenuated by a 500k pot then going to my SS amp. the sound was very OK with improvements on the sound. the output signal was very high, i have to dim the pot to prevent my SS amp from overdriving.

im sorry if this thread is such a boring one, i just wanted to get it to work properly...

[d95err]

It sounds like the problem is with the poweramp. The problem may not show up at low volume. Perhaps the EL84 is misbiased. My guess is a bad solder joint or the wrong component value somewhere near the poweramp.

If you post the schematic and the voltages, I'm sure someone can help solve the problem. Otherwise, try an all-tube amp forum, e.g www.ax84.com