Awesome! Thinking of doing a couple of mods myselg, probably not quite the same. Ideally, I'd like to put a PPIMV on just the clean channel (is that possible?), maybe try to add some kind of tone control to the clean channel to control the bass frequencies when i use humbucker guitars. I'm pretty naieve about how to approach these ideas, so any thoughts or advice would be appreciated!

Thanks again Wyatt. Really appreciate that you are around to help. The hum is not so loud, definitely not noticeable compared to instrument volume when playing anywhere near rehearsal levels. I've realized that there is a little bit of it in full power mode with the tube rec. So low that it is really only noticeable as a subtle change of ambiance when you switch between the tube and SS recto. In triode mode, it is noticeable but not loud compared to instrument volume. I noticed that triode mode disconnected the screen from the filter network and was wondering if that was the cause of the hum...

RE: increasing the resistor value between plate and screen, are there any potential negative effects of doing this?

I have found the triode mode useful for one song when recording with my band. A bit more of a compressed and jangly sound to the clean channel.

So to sum up a different way, there is some kind of hum related to the tube rectifier that only becomes audible when the power tubes are run as triodes. It is not affected by the master volume, so the issue must be somewhere after the phase inverter.

As the cab I ordered to house this amp finally came, I put on a finishing touch of making the bright cap on the clean channel switchable and was about to install the amp in the cab... However, I noticed that there was a (fairly quiet) low frequency hum when using the tube rectifier in half power mode. I've been emailing back and forth with Nik about this and so far I'm not sure what could be the issue. Here's what's going on:

Amp in full power mode, tube or ss rectifier: no hum, everything seems to work fine

Amp in half power mode, ss rectifier: no hum, everything seems to work fine

Amp in half power mode, tube rectifier: low level low freq hum, is not affected at all by any of the tone, gain, or volume controls

Measure the voltages and things seem to be running at appropriate voltages...

Any ideas on what to look for?

Actually went back and messed around with it some more after I posted that. It isn't so bad, just sounds nothing like the orange amps do with the pedals I have. I got some tones I was pretty happy with, though. Still thinking I might want to darken the clean channel a bit as that bright cap is way bitey. Then again, I was playing a jazzmaster through it, so spikey guitar + spikey amp could get out of hand!

Hey all
   

   I finally finished my build and everything seems to be working correctly. The amp sounds great with just the guitar plugged directly in to either channel, but my dirt pedals (purchased based on interactions with Orange amps, so not too much of a surprise) don't seem to come across so well, especially on the clean channel. I've got a Diamond J Drive, Zvex fuzz factory, and Dr. Scientist The Elements (worst sounding for the SC30). What are your experiences with dirt pedals and this amp? Any mods that change the interaction?

So the filaments were fine. Had a couple of wiring errors in the power amp, but now thanks largely to Nik and wyatt, I have a fine, handwired, working clone of an amp I could never afford!

Whoops, I mean 0 ohms to ground

There seems to be a problem in the power amp section. Not sure what it is yet, checked wiring and for stray copper strands. Should the filament pins measure 0 volts to ground? Because they seem to be doing that...

Just figured out the problem. Turned out to be really simple! Just a few nearly invisible strands of copper wire were sticking out and shorting pin 3 of the rectifier to pin 2. Now to see if the rest of the circuit seems to work ok.

So I made a current limiter and an audio probe. Things seem fine with no tubes. When I put in just the rectifier tube, the light dims dramatically for about 30 seconds, then comes back full brightness. It seems like something is shorting as more current is being drawn by the tube?

Thanks! I'll get one of those current limiters.

An update: Got a bunch more fuses from Home Depot. Tried only the rectifier and the power tubes. There is arcing inside the rectifier tube (which I know to work fine in an Orange AD15) for a minute or so before the fuse blows. Clearly there is something wrong with the tube rectifier wiring...

Switching to solid state rectifier, the fuse does not blow. However, the amp produces a loud hum regardless of the positions of the controls and the channel plugged into. The hum is louder and bassier on the hi power setting. Must be a grounding issue somewhere...?

I'll be struggling to sort out these issues, so if anybody more experienced has any suggestions, I'd love to hear them!

Oh, one question... Are the control pots supposed to be grounded to the chassis?

An update: Got a bunch more fuses from Home Depot. Tried only the rectifier and the power tubes. There is arcing inside the rectifier tube (which I know to work fine in an Orange AD15) for a minute or so before the fuse blows. Clearly there is something wrong with the tube rectifier wiring...

Switching to solid state rectifier, the fuse does not blow. However, the amp produces a loud hum regardless of the positions of the controls and the channel plugged into. The hum is louder and bassier on the hi power setting. Must be a grounding issue somewhere...?

I'll be struggling to sort out these issues, so if anybody more experienced has any suggestions, I'd love to hear them!

Oh, one question... Are the control pots supposed to be grounded to the chassis?

Hey everybody. I recently purchased a Stray Cat 30 kit from ceriatone.net (American distributor, right?) and spent about 40 hours over the past week building it. This was my first amp build so it was a long process and maybe not the best build ever done... Anyway, finally finished the wiring about an hour ago, stuck in some tubes, plugged in to a cab and started to check to see if everything would work. First, the indicator light comes on. Heart starts pounding. 'That's a good sign!'. However, as I'm moving to plug in a guitar and then flip the standby switch, the rectifier tube starts to glow, a crackling sound starts coming out of the speakers, and about 10 seconds later the main fuse blows. I was wondering if anybody here could give any thoughts on where to start looking for trouble, based on that sequence of events...

   Thanks!