The Amp Garage

Wow indeed! Seems like I should give this sucker a proper chance then. I actually replaced the caps a while back but I haven't had a chance to try it through a speakercab yet. Did you/your tech check the schematics?

Dingleberry wrote: The first schem was straight from the Mark Huss Hiwatt page. Wonder why he didn't draw any series resistor in the schem between the -vdc and pots?
-T

That schem is for a 100W amp isn't it?

Of course it's not the source of the problem, the source of the problem is too high neg voltage. :shock: Yes you could just add resistance in series with the pot. Anywho as I said that's how I would do it. 25k pots should get him to a range of about -50V to -100V. Add a little resistance in series a...

Yes you're on the right track. I'd switch to 25k pots first, for bigger sweep, and see where that leaves you as you'll be able to bias them hotter if you do. And in case your friend wants to try KT88's next you might need more negative voltage. Then add resistance where your arrow is pointing. 10k i...

The first link is my thread on a swedish forum. That schematic I found on a polish forum. I later redrew the schematic reverse engineering my amp and it differs a little if my memory serves me correctly. I'll have to take a closer look at my amp and the schematics when I have time. Too much to do, n...

Welcome! That's cool you found two of these. I wish I could tell you anything about the soundquality but mine needs new caps before I comment on that. It's still under my bed waiting for some love. I actually have the caps I need at home so maybe I'll have to dig it out. I just briefly compared it t...

Ok, did some reading on oscillators and tremolo and i sortof understand the circuit now. I will scale it and see how i like it. Thank you all.

Tjena Erik!

So should I leave the trem fixed voltage? Damn I have no idea how the tremolo works, need to study some.

d95err wrote:My guess is that since tremolo oscillators are rather sensitive, the ocillation would stop once the voltage reduction is significant (e.g at around half the normal voltage).

a_e_a wrote: I had the bias pot right at the minimum if that makes a difference?

Adam

By 'at the minimum' you mean max negative voltage at the grids right? Did you measure plate, grid and screen voltages?

Thanks for the heads up on the trem, hadn't thought about that. A PS-kit would be the easiest probably, but I was going to DIY this. Haven't found any schematics of the newer PS-kits so I don't know how they work... but if I was to use a VVR type of circuit, I'd need some additional filtering on eit...

Hi, Would you scale the whole amp, PI+power tubes or just the power tubes? I'm thinking just the power tubes as it has a post PI MV. But I would need another choke for that right? Or leave either screens or preamp without choke and maybe up the filtering instead. So how would/did you do it? Schemati...

Is there a layout for this somewhere? It would be interesting to check it out.

Hey, if that's what the internet says, we all know it must be true....lol. It's possible; Again, I was speculating. It sounded low imho. It could not hurt to rig one up on a bread board, or build it and try to drive a 600 ohm balanced input with it. It just strikes me as unusually low to expect fro...

not sure if the AU7 would be that low. I'm guessing a few k (maybe 5 or 10-K ) but not 600 ohms. Maybe follow with an FET or an IC buffer. When equally loaded, the output impedance from anode and cathode is roughly 1/gm, the same as a cathode follower. http://www.freewebs.com/valvewizard/cathodyne....

Thank you all! I did a bass line out using a little DI transformer sourced after a CF simple, cheap, didn't take up chassis space and had a predictable balance I'm building this as a stomp box with no extra space at all. So a tranformer that takes NO space would be nice! ;) Yes, you can use a cathod...