Tube Amp Archive

It will, once I focus on it -- thanks -- I basically learned most of what I know from Merlin's site. Joe [quote="tubeswell"]FWIW the following diagram from Merlin's site shows respective 'A' and the 'B' load lines for one half of an EL84 PP stage. The purple line (4k) is the 'A' load line, and the b...

Yeah, my problem is every time I come to that long dissertation on Class, I have more immediate issues to deal with, and just skim over it -- may be time to bite the bullet and get it under my belt . . . [quote="Structo"]I think that class types of amplifiers is probably one of the most misunderstoo...

I'm pretty certain the AC-30 is class AB

[quote="Structo"]I think that class types of amplifiers is probably one of the most misunderstood part of amp theory.

I still don't get most of it other than with a single ended power amp.

Now, is a Vox AC30 a class A or a AB push/pull circuit? [/quote]

Oh, right -- my mistake . . . Those values are an artifact. When I simplified the circuit I failed to account for the fact that I was originally thinking in terms of having an appropriately rated, 10-turn, 100R pot between the two fixed resistors for fine-tuning the balance, and then another 100R po...

Yes, I understand that. The single ended amp MUST be Class A, whereas the cathode-biased (and I supposed, fixed bias) can be, but isn't necessarily so, correct? Example being the much (mis) quoted Vox, which is cathode-biased push-pull, but NOT class A. What I was mainly trying to achieve with the s...

Okay, class of operation notwithstanding, am I correct in assuming that the switch arrangement I have in mind will at least allow me to compare the difference between an unbypassed shared cathode resistor and individual bypassed resistors, and (assuming, of course, that I'm not going to throw it whi...

Anyway . . . what got me thinking about the proposed circuit was a statement I found in another forum that stated "a cathode-biased push-pull circuit with a shared cathode resistor and no bypass capacitor necessarily operates in class A ...") I did not delve deeply into it, other than to note that i...

Hmm - The old Dennis Kager designed Sundown amps featured an 'RMS' control that basically introduced a variable amount of cathode resistance to an otherwise fixed-biased circuit (I have schematics here: http://befumo.com/music/gear/instruments/amps/sundown-sd1012c/) Reading your explanation, it occu...

First -- I apologize for failing to follow up on prior posts -- I just now realized that I was registered with a defunct email address -- which would explain why I never received notifications when folks kindly responded . . . mea culpa! I have corrected the situation. So, here's a question: I've bu...

[quote="martin manning"]Do you know what the seven-legged thing on the back of the pot is? Some kind of pre-packaged filter network?[/quote] If you examine it closely, you'll see that it's the Baxandall tone control for the 'green' channel - it's in the schematic. I've copped this layout in my own a...

[quote="Phil_S"]Using the CT to ground will either blow the fuse, let the smoke out, or both. Don't ask me how I know this. Good luck.[/quote] Yeah, so, I did precisely this to a nice Hammond power transformer. Question: any possibility of repairing it? Where would I look, and what would I be lookin...

[quote="Phil_S"]Using the CT to ground will either blow the fuse, let the smoke out, or both. Don't ask me how I know this. Good luck.[/quote]

DRAT!

Wish I had read this FIRST!

[quote="VacuumVoodoo"]Yes, the name is ITROD (Ivan The Terrible Out Drunk) [/quote]

Ahh - by my second bottle of Stolichnaya it all started making sense!

So ... is there a NAME for that circuit topology?

[quote="VacuumVoodoo"]This amp schematic is nothing more then Sovtek MIG-50 preamp into a SE output. As for that 3rd and 4th stage duo. Clue: some people say those MIgs have cool overdrive and distortion.[/quote]

I never checked those out - thanks.

I wired this up with a 3PDT switch to defeat that loop, and really like the result. Engaging it cleans things up, reduces gain, and makes the whole thing more articulate.