The Amp Garage

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The plate dissipation (Pmax), which is measured in Watts, is the critical variable. Do not exceed the tube's maximum rated dissipation. Consult the relevant data sheet. (Pmax = 42W for a KT88) Plate dissipation (Pmax) = plate voltage (Vp) x plate current (Ip). (You have one measurement (Ip). Now you...

The voltage dropped at each HT supply node is the product of the current drawn through the DC-resistance leading to each PS node. (current x resistance = voltage) E.g. take the last pre-amp dropper in the PS rail in the diagram below: there is 2mA through 4k7. 0.002 x 4700 = 9.4V. (352 - 343 = 9). ...

Zout = Vp/(Pmax/Vp) Where: Zout = desired load impedance for centre-bias Class A Vp = the plate-to-cathode voltage Pmax = the maximum plate dissipation (This equation will also be affected by the screen voltage (Vg2) and bias point*, so you want to have some idea about what you are aiming for in tha...

Agree with your response, Phil, except this bit: as the higher capacitance filters less bass out of the amp We're talking about the filter caps for the HT supply, and this part of the circuit is not in the signal path. It cannot directly affect the tone of the amp...EXCEPT when the amp draws so muc...

Thank you guys! I do have a mains power meter, but those things are slow acting. I can do the calculation when the amp is in idle. But how far is it away if I play a hard E chord? Idle vs max? Best regards, Stephan One way of doing it would be to use a dummy load and a signal jenny, inject a variet...

I vote for iterative band pass filtering to accentuate mids, and hot>cold>hot>cold biasing through 4 or more stages (to clip top and bottom peaks etc) with heaps of inter-stage attenuation and local feedback, and plate bypass caps, and the occasional DC-coupled pair (or DC-coupled CF for added compr...

Many thanks for that Phil

How would I measure the "max mA" in my amp? Put a mains power meter in series with the mains socket and your amp and switch the amp on and measure the current. https://www.amazon.com/TS-836A-Energy-Voltage-Electricity-Monitor/dp/B00E945SJG/ref=lp_5011670011_1_3?s=industrial&ie=UTF8&qid=1562317629&s...

How would I measure the "max mA" in my amp? Put a mains power meter in series with the mains socket and your amp and switch the amp on and measure the current. https://www.amazon.com/TS-836A-Energy-Voltage-Electricity-Monitor/dp/B00E945SJG/ref=lp_5011670011_1_3?s=industrial&ie=UTF8&qid=1562317629&s...

13 years for me. I've come to the conclusion that in order to get over the suckiness of sobriety, one must transplant it with the suckiness of everything else. I'm still working on this, but playing guitar is much more satisfying this way methinks. YMMV

Very nice job!

There are other benefits to using the AU triode for the PI. You can decrease the load resistors to something like 10k* or 22k each (instead of 56k) and get more tube current and much better impedance bridging to drive the 6V6 grids. The lower you go, the more you will want to think about changing th...

The gassed out tube could have happened for any number of reasons. But, the standard checklist for these is check for open Rg2s, and getting the bias right. So yank the output tube board out and replace any open Rg2s. While you're in there, do yourself and your client a favour and remove the spade t...