The Amp Garage

The suitcase handle is a nice touch.

Is the center transformer sharing one 6bq5 from each side?

https://www.diyaudio.com/community/threads/origin-of-the-so-called-blumlein-garter.313318/ Here is some info on that circuit's history, not a Blumlein invention. I get the sense that this is a well-known thing in the hifi world. Might be a useful trick if you need to lower the voltage in a cathode b...

Looks to be in pretty good shape inside. Does it work? Yes! Only issue is a sticky/scratchy volume pot, but everything else works. Haven't fully tested the tubes or measured the output transformer, but everything functions and sounds surprisingly good, in a plugging into a "hifi" sorta way. Not bad...

The weber drawing is correct. You want to fuse then switch the Hot wire (usually black in the USA). Ideally, you would switch both hot and neutral if you are using a captive power cord, but I wouldn't worry too much about that.

I'm planing to rebuild this thrift store console amp and try out a few bits of circuitry. Does this schematic look reasonable? Has anyone tried a garter bias setup before?
Any thoughts or opinions are appreciated. Thanks!

It’s common knowledge that valve were better made in the past and I wondered if the lifespan of caps was now short as most consumers devices are in waste disposal in five to ten years? I think It is a trap to generalize like this. I carefully select high quality caps that are run well below their r...

Not sure if cooler bias has anything to do with stability, I think you're just supposed to know not to put those wires together. Here's a pic of a vibrasonic I worked on a few years ago, notice how the grid and plate wires are routed. It had been worked on previously (not my mods), so maybe someone ...

Not sure if that was the OT or choke, though. Field coil often doubled as the choke. I'm guessing safety regulations are a part of why no one does this anymore. Cloth-covered wires without extra sheathing in the back of a cabinet probably didn't seem so crazy in the field coil days when you expect ...

I have changed countless "good" (but old) caps in amps where other techs in the area didn't. The difference was audibly surprising. Tighter low end, more headroom, less ripple on the B+ when the amp is tested with tones into a load. There is both a sonic and measurable reason to change them IMHO. T...

I think this was partly real partly in my head. After looking at the scope, I found some ringing on the lfo signal. I vaguely remember having some sort of noise problem with the lfo/inverter tube which went away after swapping tubes/moving wires. JJ ecc83s ring, just about everything else doesn't. P...

Since the 5 triode version with the lfo buffer should have a slightly deeper tremolo, I would assume it would also have more tremolo on lower settings if everything is working correctly.

really bizarre how the mixer tube could impact the trem speed in your revibe. I almost wonder if it's a speed of onset thing in terms of the phasing effect, i.e., an EQ difference that makes it seem faster? Yes, my money is on a perception thing opposed to reality. Was just jumpering in the resisto...

- I'm struggling to get my head around the operating point of the splitter/mixer stage from the Brown harmonic tremolo circuit. If I re-conceptualize that stage's shared 4.7k/2uF shared cathode as a split cathode arrangement, I think it'd have 9.4k cathode resistance with a 1uF bypass capacitor. Th...

It's also possible you got a pot with an odd taper. I've only messed with one original 6g7 and my revibe, so not a great sample size of harmonic trems, but both had noticeable tremolo on 1 or 2. Might be worth checking out Sluckey's revibe project if you are planning to build another. He has nicely ...