Tube Amp Archive

Hey Rooster. You're so absolutely right. I have Merlin's book - required reading! I'm playing my 'Wreck homage thru one 12", so I'm not going to get the wall of oomph that Glen K does. Another mod I've made is the one Jackie Treehorn suggests: changing the PI resistors to 39K/1K. This gives it a maj...

Greetings all! There are a lot of posts about decreasing brightness/increasing bass in the 'Wreck. My own 'Wreck homage is not overly bright, but the biggest bother I had was with the bass pot. All the action seems to come between 0 - 3, and not much happens after that, and it doesn't really seem to...

PlinytheWelder wrote:Which circuit it it?

Pretty much taken from the 12/4/08 schematic. (Not being in the USA I'm not sure if that's April 12 or December 4!)

Greetings all,

My Trainwreck homage always pops and farts, with a loud hum, for two or three seconds after I flick the standby on (i.e. so the amp is operating).

The bad noises always go away so it's not a real biggie, but I wonder what could be causing it?

Thanks!

Oops! Nearly fixed it. This really has got me stumped. I have a switch which removes the cathode bypass cap from the 2nd stage (I call it Hi/Lo Gain). When I'm in the Lo Gain mode I get buzz if the Bright switch is not enabled. Once the bright switch is enabled everything is fine. The Hi Gain mode i...

Well, I fixed it but I feel I've subverted the laws of physics. I accidentally pushed the brass ground rod hard against the chassis and the buzz and howling stopped. I connected a wire between rod and chassis but that was no good - the rod had to be physically up against the chassis. I drilled a hol...

Another clue: when the volume is on zero there's a terrible howl from the speakers!

Hello all, My 'Wreck homage has developed a weird issue with what sounds to me like a grounding buzz BUT: if I switch the bright switch on in either position the buzz disappears OR: if I turn the treble up full it disappears BUT: if the bright switch is on and the treble is up full the buzz comes ba...

Thanks for these replies. So when a company advertises an amp as having a certain amount of power, how do they ascertain that? For example, the AC30 is said to be a "30 watt" amp; or the classic Marshal "18 watter".

Thanks!

(Can't really call her a clone!) Greetings! I have 2 x KT77s, plate voltage is 386V and the KT77s are drawing 42mA each, giving a static dissipation of 16.2W per tube. How does this relate to the real-life, turn-it-up power output of the amp? Is she a 32.4W amp, or will she be putting out more power...

Had the exact same thing on a DC-30 clone. It was the 180pf cap in the tone switch that had gone. I just removed it, as it's in parallel with a .01uf.

Thanks all. Incredibly useful information.

Resistance *in* the valve? Do you mean plate resistance or minimum source resistance? I don't know! I want to calculate how much more voltage would be available using a solid state rectifier rather than a GZ34. My understanding is that the resistance inherent in the tube drops some voltage, whereas...

Greetings all!

How do I calculate (or is it printed on the data sheet?) the resistance in a GZ34 rectifier?

The transformer is single-ended, 4 Ohms-5K, 8 Ohms-8K, 16 Ohms-10K.