The Amp Garage

The cut control on the Express was really sucking. The pot was scratchy and I didn't feel like it could tame the potential harsh high-end enough even all the way down. I swapped for a simple linear taper PEC 250K pot and doubled the cap value to 0.01uF. This seems to be working better so far and has...

I've been pretty happy so far with both the amps using a Cut control, and just the NFB with no specific presence control. I do have a question though. By having the 4.7K resister to ground off the PI tail with no Presence capacitor... does this mean I am simulating the presence being turned all the ...

Hello Matt -- Tinkering with perfection. An excellent collegial process. .. Ya, these have been my favourite couple amps for many years now... So it's worth it to try little tweaks that can make them more optimal. I'm curious how others find in regard to whether the presence is needed for the equal...

OK, so now both my Liverpool and my Express are pretty similar. They both have the stock 100k feedback resistor. Then I forgo the presence control and just have a 4.7K to ground off the PI tail resistor. Then they are both using a Cut control with a 250K pot and a 0.0047uF cap. I actually put a 180K...

So, my first reactions are pretty good. For the Liverpool, I also switched back to the 6k6 OT primaries. I think the clean and mean volumes are closer now. I switched from my 12ay7 in V1 back to a 12ax7... then switched back. I think I need something more in between like my 5751. As far as the expre...

Neither of my Trainwreck amps currently have the stock presence circuits. My Liverpool currently has no Presence or NFB and just has a cut control. My Express has the Naylor Presence circuit. I was making a few clips of both amps a few days ago. I was pretty happy with my Express, except there is no...

At this point, I'm not finding the bass level to be a problem. I pulled out the MV put I had added before the PI and put it back to a more stock 6G3 bright channel. The simple Volume and Tone controls seem pretty good, so I went ahead and made a Leather Faceplate with the simpler controls. 20250507_...

Hi Matt, Yes, same layout as the Songwriter. I've been doing some SPICE modeling of the SW bass control but in the context of a Hot Cat-like build, meaning, trying to create a sweep that is not too trebley or bassy and with a bit better response. Your work has confirmed that 1n5 is a comfortable sp...

Hi Matt, Ok, thanks, that is helpful! If I use the Songwriter bass circuit, I would probably choose 1n for the base value and 47n in series with a 500kA pot. I found that with a 3M-RA pot, most of the useful travel and bass was from 12pm to 3pm on the pot anyway. Yes, that bass control and the 330k...

Ya, it is funny that Bad Cat didn't call it a cut control.... Maybe because it's wired in the more intuitive way where it gets brighter as you go clockwise. I find that this amp definately needs it... I'm always running it noticeably below noon.

This is an interesting discussion on the PPIMV for this circuit. I have been thinking about it as well since it might be nice to scale only my power tubes with the VVR and that would require one. Right now it is easy to dial in great tones for either channel at any volume, but if I want the two chan...

OK, now I am confused... and it's because of that Blumlein picture I posted. I don't know what that other side of the grid part of the diagram represents where there are caps. I have the suppressor grid (pin 1) tied to the Cathode on my EL34s. My Screens still have just their 1K power resistors. It'...

I think the discussion around parallels to various undergarments and especially the illustration in the TCJ post https://www.tubecad.com/2009/04/blog0163.htm came up short. The essential feature of this circuit is that it ties the output tubes together, more like this: Haha! Nice picture. Those rea...

Matt, what is the garter circuit in the EL34 amp discussed in this thread? That is it, Martin. There are also a couple 220uF Cathode Bypass caps from Cathode to ground as well (only one per cathode). The grid leak (I think that's what they are called) values are 220K instead of 300K. I've settled o...

Yes, definitely EL34s. I will parallel the input stage, like the Songwriter. Do you find that the single 1n5 coupling cap is enough and balance with regards to low end? I am debating adding either a bass control like the Songwriter, or maybe a 3- or 6-pos switch to change coupling cap values. I am ...