Tube Amp Archive

Thanks, I'm using a battery. I'll have a look at the wiring. I used a metal plastic input socket (eg not isolated from the chassis) could this create a problem? Cheers

HEy there, I built a derailment, sounds great but when I put a fuzz(high gain) pedal in front of it I get a really loud hum is this normal or does it sound like a ground loop?

I have three combinations from three wires. black green (14.9:1), black yellow (20.7:1) and yellow green (35.2:1). THe two with black could share the same ground. I figured I could put in a switch so I could use the green as a ground on 4 ohm setting (disconnecting black) and getting that higher vol...

Thanks again.

Thanks it's a little smaller. Core 1", size 3 x 2.5". Secondary has three wires coming out of it. I figure the
primary voltage
35.2:1
impedance ratio
1239.04:1
is between the between the two taps, but maybe I can wire it with a switch to utilize this output also. Any harm in this? Thanks again.

Hey there I worked out these calculations using info at the aikens website 1v ac on three secondary wire combinations primary voltage 35.2:1 impedance ratio 1239.04:1 1239.04x4= 4956k to 4ohm primary voltage 20.7:1 impedance ratio 428.49:1 428.49x8= 3427.9 primary voltage 14.9:1 impedance ratio 222....

Thanks, yep, got the screech out. I had isolated the output socket and not grounded it anyway. A wire to the chassis from the the socket and the screech vanished. I've added a master volume in between preamp and poweramp stage. I've run a shielded wire from the master vol to a preamp output socket. ...

Well things are coming along fine, finishing off the cabinet. Is there any reason I couldn't add a preamp output socket after the final triode preamp stage? Thanks

'Do you have a shorting jack on the input?'
Not as yet but I plan to put one in. Thanks for the reply, grounding the sleeve on the output seems to have been the problem. This has been my first trainwreak build. I wanted to hear how the preamp sounds before building a bigger version. Nice sounding amp

Well after checking the grounds (which were ok) I found the solution, not sure why but the when the output speaker socket (common) is attached to the chassis the whine/oscillations disappear. I thought I was supposed to isolate this socket? Can anyone explain this? Thanks.

Thanks, there is no feedback loop in this circuit, so I'll have a look at the grounds. I attempted to star ground the amp so maybe this is the problem. Really whines if the input is left open (eg cable not plugged into guitar)
Thanks again

Hey there, I've just built a derailment. I seem to have a grounding problem. Even when using a 12au7 as the first preamp tube I'm getting a high pitch oscillation when I remove my fingers from the guitar.......all the eq pots work though the treble controls the frequency of the squeal. Not sure wher...

Hi there, is there any reason why I couldn't made a preamp using the derailment preamp schematic eg will it be ok in terms of the impedance of the output signal? Thanks

I'm throwing together a derailment from bits and pieces. What difference would using 8uf decoupling caps rather than 22uf for the first two preamp stages. (eg small amp-would 8uf be big enough?) Thanks

Thanks for that. Research time. It's been a year since my last build and it seems I haven't retained too much...last time I opted for the cathode bias due to simplicity.Thats cleared things up and yep I'll head back to some reading before going further. Thanks again