3W Tube Guitar Amp

History

I was building amps regularly from around 2002-2006. I didn't stop because I meant to stop, just other things took my attention and I was pretty happy with my main amp. That said, the main amp went through a fairly large revision in about 2012, going from ECL86 power valves (which were expensive) to 6F4P (which are unknown Russian tubes that I think sound amazing!).

I used to frequent AX84, and nearly everything I built and learnt is from there.

The Amp

The amp has been modded too many times to be neat, the controls are confusing, and there is clearly an error in the circuit somewhere but I quite like it how it is.

It's very roughly based on a Melissa amp (Thread here, schematic here), but various things have been modified and I can't remember all of them.. Some of them are:

• 6F4P phase inverter/power valves (they're triode-pentodes, hence the dual use)
• Bass control replaced with a simple high pass filter with a pot setting the position
• Gain knob made switched to have a totally off position
• Most tone control caps tweaked by ear
• Bias of the phase inverter set by ear; I think it's biased warm, but not as warm as ideal for best PI distortion; however it gets maximum clean headroom so we can attack the power tubes even more.
• Character control miswired/faulty component. The original version changed the character, but the gain was about the same all the way through. This version has loads more gain at the Marshall end of things, and I have no idea why... However I kind of like it, so am not in a hurry to change it.

How does it sound?

Like this: (plus all the guitar related videos on here are recorded with this amp).

I love the Character control; it changes the amp from Fender scoop to Voxy to cranked mids Marshall; it's probably the one control I adjust regularly. The others are more setup for the guitar and song then left.

It's pretty touch responsive which I love; it goes from cleanish to cranked with just the guitar volume.

The powertubes provide nearly all the distortion in this setup; at higher gains there is a bit of PI distortion as well, but long after the power tubes are saturated. It's a good sound, but comparing to say Glen Kukendall's Trainwreck videos it's less attached to the tone of the guitar.