The Amp Garage

I omitted to say that my amp in question uses cathode bias, not fixed. I "borrowed" the HT switching of the PT CT from a Top Hat schematic I ran across on Schematicheaven, which was also a cathode biased design. I had not thought about the consequences of its use in a fixed bias scenario, though, so...

I omitted to say that my amp in question uses cathode bias, not fixed. I "borrowed" the HT switching of the PT CT from a Top Hat schematic I ran across on Schematicheaven, which was also a cathode biased design. I had not thought about the consequences of its use in a fixed bias scenario, though, so...

That is one hell of a good price. Plitron would be a lot more! Your experience is everything I have been told to expect, so I think I'll be trying some too. Does this guy do PTs as well?

"Mr. Fuchs" is right about that use of a cathode switch; I have considered using it as a tone stack defeat switch, in effect a gain boost switch, which I think is a safe use of it. On my last amp, I used an interesting switch from Westlabs, a DPTT Carling, as an off/(on/standby)/play, all in one swi...

I was just using 50V as an example, nothing more. I have done it myself with a 50V Zener, back when I didn't know enough to match my PT more closely to my application! The whole point of using a Zener instead of a resistor is that the Zener clamps the voltage, i.e. it is acting as a one-way device, ...

Kevin O'Connor's TUT books (The Ultimate Tone) could help you. In the first 3 volumes there are sections on solid state including MOSFETS. He has lists of contents on his website www.londonpower.com. I have soldered in reverb footswitch relays which have pretty flimsy connecting pins. I stick the re...

Kevin O'Connor's TUT books (The Ultimate Tone) could help you. In the first 3 volumes there are sections on solid state including MOSFETS. He has lists of contents on his website www.londonpower.com. I have soldered in reverb footswitch relays which have pretty flimsy connecting pins. I stick the re...

A resistor does cause "sag", just like a rectifier tube, when inserted in a SS generated DC supply. When you crank up the amp, it draws much more current (in an AB1/AB2 design), which causes the voltage drop across the tube or resistor to increase, lowering output power, and, depending on the VA cap...

These usually come in a 220, 247 or similar case size so as long as you have the space to bolt them to the chassis they will work fine. Don't forget the thermal grease.

I am also a "NO SS in signal chain guy" but this doesn't violate that principle!

Just a cautionary note here: lowering B+ with a resistor in line is fine for lower powered amps that run Class A or heavy AB, like the AC 30 does. This is because the current draw doesn't vary much from idle to full output in these classes of operation. Even so, the lower the B+ voltage drop the bet...

I've used both unibit and greenlee punch. Greenlee is better in steel and aluminum unless chassis is real thick ( I have done one aluminum chassis in 0.125" T5). Unibit always needs cleanup, Greenlee doesn't. Hammond 20 ga steel chassis are a pita with the unibit, 20 ga is NOT thick enough for a gui...

Only downside I can see is lower plate/screen voltage compared with capacitor feed. Smoooth is good! Where did you get that thing? It must be a monster at 225 mA unless it's very high DCR.

I second the comments about heater current on 6SL/N7s. My current amp uses 4-6SL7s and one 6SN7. My PT is copper strapped and has the internal grounded screen between pri/sec windings, but I still had to go to DC heaters because of massive hum & buzz. I took the 6.3 VAC supply through a 25A 50V brid...

Check out the schematic on this one, at schematicheaven.com; it's a tweed Champ circuit with no feedback & tons of filter capacity. I'm thinking of doing something similar with a single KT66/EL34 for about 10W, but maybe using choke feed on the plates and screens, which will probably sound better th...

It's August now, but I see no-one else has addressed your question. "Conventional wisdom" (i.e. those old dudes that designed the 5AR4 back when dirt was rocks) is that you should not hit a 5AR4 with more than about 60 mF from the first filter cap it sees, so 32+32 should be OK. After the choke/resi...