The Amp Garage

I've just taken a big detour revisiting the global Negative Feedback and presence circuit... because they seem to have a big impact on potentially creating some harsh frequencies in the 5kHz ish? region... especially on the pick attack. I've changed the circuit before in this area when I first wante...

I was just checking out your schematic and layout today for inspiration on altering my presence and GNFB values on my MHartman layout #004? inspired build. Anyways, I tried wiring mine like your schematic, but it seems like something is a little wrong. When I use the presence circuit in your schemat...

I also see that it should not accompany a bypass cap. It might be true when the idle point is shifted so far towards cutoff but you can try a mildly asymmetric bias and see how that works, even small changes in value have an effect on the headroom. In my case I used a 2k7 resistor with an unremarka...

I believe the Mhartman version of the SSS has the mixer tube that mixes the clean and reverb signals like the JM Signature clone. I wonder if changing this can get you what you want. The #005 SSS does not use that method of mixing the clean with the reverb and it has lots of gain on tap. You can li...

Do you have a schematic you can share? Ya, that's been my struggle. Every time I want to look at a schematic, I start searching around the forum until I find one. (never found a #4 yet that actually should go with my amp). Here is the #002 I more recently found this morning. Sorry, I don't remember...

I see a schematic of #002 with added 100R resisters. Can anyone explain what those are going for? Those cathodes have a connection to the LNFB loops. Otherwise the LNFB loops would be shunted to ground. Thanks! That makes sense. Mine Doesn't have that because its LNFB plays between plates and grids...

Well, I did the PI balance trim adjustment. It made me feel like a bit of a mad scientist, HAHA. I Used a USB-C to headphone jack dongle from my phone using a frequency generator at just over 400Hz. I had to go into my Full-Drive 3 pedal with just the boost turned on and I turned it up until I measu...

Do you have a known good set of tubes in this? Those voltages came from my LTspice simulation, so they are "perfect" specimens. OK, I rolled a number (5 or 6) of tubes through V1 (5 or 6) and they were all about the same. I left in the one that seemed to sound the best to me and that also gave me t...

If you have tried V1 without the LNFB and you still can't get it to bite I don't think restoring is going to help and yes, closed loop gain (with LNFB engaged) is going to be lower. But not from perspective of the signal entering the stage which instead sees more headroom and more swing on the grid...

It's all very subtle. I feel like I need a bit more something. Maybe I need to record a demo and see if I'm chasing something that doesn't actually exist. It's not like it sounds bad, but I feel like some people claim these things want to sustain almost into feedback with a clean tone, and I'm not g...

A part of the compression is coming from the LNFB loops. Especially when you drive the first volume pot a little more. Not all SSS are the same as are the LNFB loops. Which one do you have? Erwin My build is adapted slightly from MHarman's Layout which I believe is based on #004. So I see that I di...

The 2A rating on the NTC limiter is probably for continuous operation so exceeding that by a bit on startup is probably ok. OK Thanks. I'll leave them for now and work on the other stuff. I put another tube (Tung-sol 12ax7) in the PI and it balances a lot better plate voltage-wise. They're currentl...

A part of the compression is coming from the LNFB loops. Especially when you drive the first volume pot a little more. Not all SSS are the same as are the LNFB loops. Which one do you have? Erwin Thanks for that idea. I think I changed it a little a couple years ago. I'll take another look. I used ...

The same current flows through both, so you are still limited to 2A. OK, thanks! This is the first time I could seem to find a clear answer on this. That actually makes sense I guess I could have measured across one of them to test. When measuring across the pair of them, I do see that the current ...

So, I finally got around to installing a couple CL-90A Thermisters in series on a terminal strip after the power switch. They are each supposedly rated for 2A, so I was hoping that having them in series next to each other they are good for about 4 amps. They seem to be working fine. They brought the...