I wrecked my Valve Junior! (chassis at least). Here is another in my long (and growing) line of amps built in a Valve Junior chassis. This one is pretty much a full Trainwreck circuit made possible, in part, by the 6BM8/ECL82 power tubes. I’m using some Russian ones, labeled 6F3P, I got on ebay. These tubes have a triode section so I could use them as the power tubes and the phase inverter.
The preamp uses a pair of 6N2P tubes, also Russian (hmmm…Vodka Gimlet?). These are a 12AX7 equivalent. The heaters are wired differently but other than that they are very close as far as I can tell. The nice thing about them is that they are cheap! woohoo!
For iron I’m using a WRVBPT and an Edcor XPP15. The PT doesn’t even seem to get warm so I like that. However, the voltage is still a bit high so I might be making some changes at some point. The Edcor OT sounds good in this application too.
So the circuit is pretty much taken from the Express. The PI is sort of leaning towards the Liverpool a bit though to cut down on fizz and firm up the low end.. I also leaned heavily on a design from the Hoffman forum called the “Little Wing” by Da Geezer.
The amp is very responsive and does not cover up your playing with a bunch of overdrive. It has gain but at the same time it’s very articulate. It’s also very loud! A pair of 6BM8s should be about 7 or 8 watts but this amp seems as loud as my 6V6 amps.
After playing it a while through my 1×12 with a Vintage 30 I think it might be the best sounding amp I have built so far. However, the components I used, especially the transformers, are not really… um…”high end” so it makes me wonder how it would sound built with better stuff. As it is though I think my total amp investment is just a little over 100 bucks. Not bad…
Here is the current schematic.
You said you really liked the sound of this amp. Do you think or have you tried 6f4p tubes in this circuit??
I’m interested because I have a bunch of 6f4p tubes!! Thanks!
I did try a Trainwreck type amp with 6F4Ps. It was a challenge because 6F4Ps are some of the easiest tubes to drive and a Trainwreck circuit drives power tubes harder than just about any other circuit.
To be honest I think the 6F3Ps work better for a Trainwreck.
I’ve just buit this amp.
May I ask you for plate voltages on 6F3P?
So far the amp is mute, but I’ll find the reason of.
For now,I need to compare my plate voltages with yours.
So,thank you for the assistance in advance.
Sorry, I didn’t see this. I think this had around 320v on the plates which, I think is a bit high for these tubes, but it worked. I don’t remember the screen voltages. This amp got rebuilt.
…and sec.grid voltages, as well. I forgot them;)
Congratulations, I like this site to get ideas, thanks for sharing.
I did something with a push-pull 6F3P power amp and concertina P.I., based on the GibsonGA8T (https://www.youtube.com/watch?v=AjXSSSWlpUs).
It sounds quite nice but I would advise about the plate voltages, they should not go beyond 275V if you want them to last longer, 6BM8 can cope with higher B+.