The Amp Garage

martin manning wrote:

Smokebreak wrote:My question concerns the Va (b) and Vg2 (b) @ 450V . What is that?

No idea.

You see that in a lot of British sheets, sometimes opposite Vb(o) (zero signal). It might be supply voltage, but that doesn't make much sense.

I'm sure Martin is right about the Bassman 135 schematic being in error. All of the other UL schematics show the 47K/68K flipped. Interestingly, it's only the UL versions have that 21K difference: in roughly the same period with 2x6L6, the grid returns are both 100K; with 4x6L6, they're both 68K; wi...

Grilled meat, too.

There are some chemistry secrets that may have died with the last real tube engineers, but a major difference between the old stuff and the new was when old manufacture didn't come up to standards, it got binned. New manufacture rejects get sold.

Gerald likes stiff power supplies, hence the 110uF for the main filter. But there iconic amps that are seriously underfiltered. Yes, they tend to produce ghost notes when pushed, but that's part of the "charm."

I can't help but think that without George Martin, the Beatles might actually have been the Rutles.

I'd be thinking more than one bench (I have three, plus totally separate places for table saw and router table). Keep one space for amp and pedal building, something with drawers for some tools, wire, solder, miscellany. Put a peg board behind it for screwdrivers and pliers and cutters/strippers. Pu...

If we're speaking of vintage tubes, the 7025 had spiral filaments to reduce hum. When the 12AX7A was introduced, it did too. You'd be hard pressed to find a modern tube without a spiral heater (except maybe Sovtek 12AX7WA/B/C, but I'm not certain.

Looks like mica to me.

The first Pro Reverb is AA165. It uses a GZ34 rectifier. If you go that route, you'll want a good one: Mullard, GE or Matsushita. You can also go solid state like a Twin, maybe with a small sag resistor.

SS works great for electric bass (even though I'm "religiously" opposed to SS). But if you're looking for a sort of SVT sound or amplifying an acoustic bass with a piezo pickup, tubes are pretty cool. The last tube bass head I built used 4xKT88. Depending on B+, you'll want a PT North of 400mA. The ...

Triode? Wouldn't sound the same either. Maybe big power resistors on the output to suck up half the power.

Maybe a Pro Reverb. One speaker or two. With a robust enough PT and high enough B+, it could certainly do 50W.

In my SEs, I put the tone stack in the middle, Fender style. Added gain in tone recovery.

https://en.m.wikipedia.org/wiki/Tetrode gives a different version: "The first true screen-grid valve, with a screen grid designed for this purpose [reducing Cg-a], was patented by Hiroshi Ando in 1919, and the first practical versions were built by N. H. Williams and Albert Hull at General Electric...