The Amp Garage

Geoff, don't get too caught up in the high-end hi-fi myths of components having some mysterious unmeasurable secret quality that is responsible for the particular sound of an amp. A-B tests that are double blind are rare but mostly reveal that a $20 resistor is no different from a $0.10 resistor if ...

This post is quite surprising to me. Building an amp well is a lot of work. Repairing an amp is usually very simple and fast. If a tech can't diagnose and have the mechanism of fault determined in 30 minutes, he is not much of a tech. He might be a great constructor or musician but he is not a tech....

uot;] The poster who supplied the link obviously believes that it was, without questioning the statements made, nor apparently understanding them. Out of hand, he claimed biasing using instruments has been discredited and is harmful. No, ignorance is harmful, not instruments. Wow. A bit harsh. Well...

Every library in the country is full of unread books that would be of great value to aspiring techs so there is no lack of availability of information about electronic theory and engineering. What apparently is desired is a quick answer even if it is just opinion, instead of an understanding, or els...

I might be confused by the different sockets so to clarify, the plate lead on pin 3 of the socket where the excess current is being drawn through the tube is suspect. At idle, the DC resistance of the the primary is the only resistance limiting current, both the good side and the hot side wil be pul...

Now there is more to go on. So you now know that the circuit is at fault, and now possibly the tube that gets plugged into that socket. AC on pin 3, the plate? Is that with signal applied or idling? If with signal, , the voltages you gave in the first post would indicate a shorted output transformer...

Deleted: double post

I suppose I should write about this topic. Reading the article gives the impression that the power disappation of a tube in a circuit is all that is needed to balance the compromises in different operating environments of tubes. He was using different plate voltages to show his point but he ignores ...

The article assumes only time domain waveform information is used, which it is not, by anyone who knows anything about amplifier operational characteristics. I am not sure what he is trying to sell but his analogy would be close to "avoid driving a car using a map because it doesn't tell you enough"...

Don't change anything, mods should only be done to functioning amps. Find out the problem, resolve that, then measure the characteristics of the amp so you have a baseline set of measurements to refer to when modding. Pull the power tubes and measure the values at socket, if all is right, install 2 ...

Maybe I am missing something but why on earth would an expensive biasing tool be needed? If you have a scope, DMM, low distortion oscillator and dummy load you can do better in less time. Better, add a spectrum analyzer and be sure. A computer sound card is all that is needed and free spectrum displ...

My first amp client bought a dual 6V6 amp from me. My amp builder (at that time) rated it at 10.8 watts RMS at 2 on the volume knob. 15 watts at 5, and around 19 on 8, although the volume dial went to 10.. First things first, fire the amp builder. ANY builder/designer of an amplifier that would spe...

On a *nearly* related note, if a smart bunch of folks (like us, ferinstance) looked hard enough at the specs of our favorite tubes vs today's rebranded offerings from the East, I wonder if we couldn't make some subtle changes in our circuit designs that would produce results more like the results o...

When I was in the seventh grade, we used to have sock hops every Friday afternoon but it was announced one afternoon that they would come to an end because an Adult Education class was starting in the room next door after hours when the sock hop was held. I was sort of interested in thr dances becau...

km6xz, You are obviously quite knowledgeable, so let me ask you. Is having a loop with a 22k R and a .0033 cap in place of the normal 100k R right after the tap in any way dangerous to the speaker or OT's health? Someone elsewhere seemed to suggest this and i now would like to know for peace of min...