The Amp Garage

So exactly what are we hearing in the clip? Given the assumed purpose of these resistors would the distinctive ripping sound be a breaking into and out of a parasitic oscillation that is triggered when the signal amplitude is high? And, why did it not occur previously? Do the inter-electrode capacit...

Great, thanks! Where does the test point connect to?

MPM

ic, I doubt that it's because nobody looked... I made copies and (virtually) populated them with parts to figure them out. It all made perfect sense to me. It would be great to see the HRM board annotated if you don't mind posting it. I'm not focused on HRM amps just now, but I'm interested in the e...

Bypassing the cathode resistor increases the stage gain, typically about 5-6 dB. It creates a shelving effect where a transition from the un-bypassed gain to the higher bypassed gain occurs over about a decade (a factor of 10 in frequency). The value chosen determines the frequency range over which ...

A kit is also nice but, you'd miss on the smell... Tell me about it! I love the smell when I open up my 67 Deluxe Reverb. Glad I'm not the only one. :D Not by a long shot, I'm sure. A while ago I was at the local Guitar store with my son and pointed out a '59 5E3, saying that it was probably a grea...

Also, the cap looks like it is sitting between the two heater lines, whereas in my head I was thinking that the + from the cap would go to the heaters, and the - would head to ground. This is different than what I've seen... The cap is across the 6.3V on the heaters because you need a store of char...

Here's another incarnation; this one is from the Marshall 4001 Studio 15. I have an '88 4001, so I can say that it works fine and has held up well.

MPM

Info here: http://thetubestore.com/earfenam.html I just Googled 6SC7 substitute. The chance of finding something with the same pin-out looks slim, but since it's a homebrew, you could rewire it to use another type. 6SL7 is a replacement (with rewiring) but you are looking for more than that... check...

You only have to provide the anode characteristics data table (plate curves), by digitizing the plot from the data sheet for the tube you want to add. You will want to put this data into one of the blank “cust” (custom) areas on the device library sheet so that it will be accessible by clicking the ...

This is the graph, with the three cases plotted. I picked a cathode resistor of 1.7K because that matched the Va (plate voltage) of the first case, then held it constant. The intersection of the cathode load line (purple) with the anode load lines defines the idle points. Note that the plate voltage...

That's fine for the example case where the voltage drop across the plate resistor and the resistance are both known. The second part of the question was: what happens if you change the value of the resistor? You know the current for the example case, but with a different value for the plate load res...

Try

http://www.freewebs.com/valvewizard/

MPM

Thanks for the explanation, Wayne. I don't know much about it, but I think with only 4 characters in his call sign, this cat has been around a while.

MPM

Naw, the idea is a good one but the d-pre is not a great bit of engineering. I really like what adding 10 to 15dB of gain on the front end does for single pickups. The second sucky side of it is a phase inversion, but that is fixable as well. What is the disadvantage of the phase inversion? Seems l...

that guys got to much time on his hands..is the flame just taking the place of the heater then? and no vacuum obviously Cute. The cathode is heated by the flame, so the flame is doing the job of the heater, and since a visible flame is ionized gas, that must be allowing electron flow and substituti...