The Amp Garage

So it is likely that the PI tubes I’ve been using in this build aren’t that well balanced then? I didn’t really put a lot of thought into selecting the PI tube out of my box of tubes. I’ll dig a little more and see what might be hiding on me and give it a whirl. Is higher plate voltage desirable in ...

I think about it a lot - I just get overwhelmed with the choices and which specifications are important and which brands are reliable. Two channels and a built in function generator are about all I think I need as far as features go. Any suggestions are certainly welcome. Regarding your suggestion M...

Hey that’s a simple and effective solution that I didn’t even think of Dan!

Thanks, I just might try that

The JJs (which I put back in) were about the same variance and within a sixteenth of an inch in bias pot wiper travel compared to the EHs. When I observed all that I figured the PI would be close too. Nope :!: I don’t understand why, but the bottom line for me is the JJs sound decent and everything ...

Well you generously help so many people it would be difficult to remember everyone’s specific builds Martin, lol.

The tubes are within 2.5 mvdc of each other at idle - which gets closer to 2 mvdc once it’s warm.

Yes, measured mV DC across cathodes of power tubes with 12v AC measured across load resistor. Mine is a 50(ish) watt build and I tried swapping the two power tubes around and got similar results - so no improvement with that. The JJ/Ruby HG 12AX7 I originally was using had 290/272/40.7 (plates a, b,...

Hi All, Just put a brand new set (from a reputable dealer) of matched EH 6L6GC in my BM and went through the static bias process. Everything is good; they biased close to where the JJs I started with were. Then, I went to re-balance the PI and found that I couldn’t get anywhere close. The trim pot c...

Looking good Dan!

Thanks Martin!
I’m glad I’m not driving you guys nuts with my questions and happy to “help” in my own special way, lol.

Random update: tested the amp a few different times today and none of the strange behaviors have returned. Pilot light is bright and consistent; no cutting out with the sound, voltages are all good.

Great lesson for starting with the simple things first.

Ok folks, I think this post will close-out this build thread. Here’s some final observations: - After playing with the HRM quite a bit - I seem to have settled on these settings (for now): —bass: 185k, mid: 8.7k, treble: 115k - The EVM-12S is back in the cab. The “grunt” of the G12K-85 wasn’t enough...

Looks good jer-vic!
Always liked the idea of this design due to its simplicity and versatility. I’ll have to build one some day. Eager to hear your impressions of how it sounds when you are done.

Thanks pullshocks, but it turns out that wasn’t the end of it. The next day I went to play it and got absolutely no sound (but the pilot light was consistently bright). Out of the cab again, bring it up, check voltages, inspect important connections, everything normal. Plug in a guitar and get faint...

Understood Drew and Max, thanks for the replies! After posting this, I unscrewed the jewel and immediately noticed that the bulb was loose in the socket. Took it out and then saw that its contact surface was sort of lop-sided - which I thought would make it prone to poor seating. So I cleaned the co...

So I’m playing my 2nd gen ODS clone today and I hit an E flat at the 11th fret of the high E string and the note rings, then fizzes. At the same time - I notice the pilot light (regular socket type, not an LED) dimming. It’s like that note on that string is vibrating something and causing this behav...