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Check post 28, the link to Sluckey's schematic is there. Other than tube rectification, I don't know specific differences between the Sluckey and Hoffman design. I am very happy with my Hoffman build.
I forgot about rectification, mine is SS and I think Sluckey's is tube. I have not compared the two schematics in depth, but I think they are very similar.
Sounds like you have almost the exact same amp I have! I built a Hoffman Plexi 6v6, which is based on Sluckey's 6v6 Plexi. It has a standard pre-phase inverter master, but I made a couple of small mods recommended by George Metropolous - I added a 220K resistor in series prior to the MV pot...
Was your 20 watt Plexi build based on EL34s or 6v6s? Curious how you were able to reduce the wattage. At low volume settings with a PPIMV, do you hear a difference?
I know George Metropolous prefers a pre-phase inverter master because of the change in NFB with a PPIMV.
Is there a tonal difference at lower volumes with a Type 2 PPIMV due to the lack of negative feedback? I have always wanted to try a PPIMV on a Plexi. I have a 20 watt 6v6 Plexi with a regular pre-phase inverter master, it works well and if I need more grit, I just use a boost pedal.
Success! I got everything to work, all switches work well. I am contemplating adding the -28 db option as well.
This unit sounds great and it was a really fun project. Thanks to Gene and all the contributors for a great design, this thing sounds awesome!
Okay, I rewired the attenuator as shown above, and both the first switch and second switch work perfectly. However, the -3.5 db switch makes no difference. I am thinking that the DPDT switches I ordered off Amazon might be very fragile with soldering. Does anyone have a source for...
The wiring diagram on page 123 with the 28 db reduction, is that the way everything should be wired on the M2? I just saw that wiring diagram, it is slightly different than I have it wired up. Might be what is causing the problem.
Ok, I have run into some problems. I finished all the soldering, ran through the schematic and it looks like I had everything wired correctly. The problem is with the first 7 db switch, it doesn't do anything when I flip the switch. The 14 db and 3.5 db switches seem to work fine.
When...
I have all of the components set in my box, about to begin the wiring. Maybe a silly question, but the air core inductor has a lead that is on the outside of the ring of wire, and a lead that goes to the middle of the ring of wire. Does it make any difference which lead is wired to the input...
In terms of switches, what amp and voltage ratings are fine for the DPDT switches? I have some rather large switches on hand but they are harder to throw, I'd like to get some mini toggles instead.