What’s on *YOUR* workbench?

Hafler T-2 rack guitar preamp, LTspice model of stock presence control frequency response curves:

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Remove three caps, add one new one, change one cap value, and voila, a new midrange control:

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There's also a pull boost switch that currently adds mostly treble boost, I may revamp that as well once I see what the new EQ scheme wants. Stock overall voicing is way more scooped than I really want, so I think the boost will probably end up being OK now with the modded mid control in play. But I may want to take it more broadband, which would only entail bumping up one cap value. There's bass/treble EQ to play with too, if needed. Haven't modeled that section yet, but it's a pretty standard Baxandall format that I'm very used to tweaking as needed.

I also put in some of the magic WE germanium diodes, but it looks like the diode clipper section isn't really doing much in this thing at the moment anyway. I had knocked down input gain for bass usage eons ago, but bumped it back up a little recently, and will probably want to revisit that as well. It's a pretty easy to unit to work on once you get the board out of the chassis, which only takes about 5 minutes once you've done it a few times.
 
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I took a small break from completing pedals due to all the music stuff I've been doing, but felt like throwing the Quantum Black Silver Mystic together. And while I don't actually own any DOD 250 pedals, I think writing this one off as "just a DOD 250 clone with an useless EQ thrown after it" is not smart.

I suspect the sound is heavily influenced by what I've read of the pedal, where the active EQ section can overdrive the later op amp stages. In fact, the mid band seems to change the nature of the gain structure more than just a naive mid control normally would, and increasing the mids also increases perceived gain by a substantial amount. Also one side of the clip switch has lower gain than middle (off) position or the other side, which I assume might be the germanium diode side which has a lower level and thus overdrives the op amps less?

All in all, it's good for a very stonery, doomy to a grungy tone on the lower end. Not very bright or articulated, more of a sea of gain type thing. But it's quite fun to play with, surprisingly quiet for how much gain you can pull off (although the QC now has a sidechain gate so it could be that I just don't hear all of the noise) and just pretty fun to play with if you want a wall of distortion type sound.

Edit: Also the knobs are pretty great IMO, they stand up a little off the pedal, but they were very easy to put on, and come out to ~67eurocents per knob to Finland. That's a great price for small metal knobs that fit into 6.35mm smooth shaft pots. Link here https://www.aliexpress.com/item/1005006577901004.html if anyone else is interested, price might even be cheaper to the US since it includes taxes to EU at least, I don't know.
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Another late night bending session! This time I went for revision 2 of the MKI tone bender I had made previously. It’s slightly different in design to the first, the most obvious is the added battery door but I also raised the top portion to sit above the bottoms side walls for a better aesthetic!


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Populated the Parasit Theremin Fuzz board from a Musikding kit, nice and quick job. I realized afterwards that it would have been easier to measure the pot locations before soldering everything, but it shouldn't be too bad on the reverse side even now. I like it when the pot outlines are printed on the reverse side, makes measuring much easier.
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Recapping a 15-year old RME Micstasy power supply. The -5V rail went rogue to almost -8 and seemingly blew all 8 mic pre chips in the Micstasy, which seem to be the only components in the unit that use -5V (with an absolute max spec of -5.5V). Overvoltage protection anyone? Hello?

Not even RME designs their own damn power supplies anymore, no matter how much they charge for their stuff :confused:

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Got around to fixing one of the broken Dwarf amplifiers. Fired right up after repair. Wasn’t expecting that as it was a mess when I got it.
Here is a before pic. The circuit board is supposed to mount to the front panel by the jacks. They’d ran wires to all the jacks and had rerouted the power layout.
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Here is the board after rebuilding
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And finally back home! Dwarf #1443 back in service!
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Also on the bench, a Hoffman Blues Jr build with 6V6s!
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Found nothing on this forum about the Tortenmann TA-100 germanium overdrive so wanted to share this great circuit! Breadboarded it this week and it’s going to be my next build now. It thickens up my Boogie Mark V90 3rd channel into Rectifier territory! But also has really nice lower gain drive sounds on tap if that’s your thing.

Uses 3 PNP germanium transistors in a negative ground format. Sounds excellent, good amount of crunchy gain on tap and adds nice girth to already overdriven channels.

Tested some different diode combinations (not extensively yet, just what was on my little diode DIP switch board) and my favorite was asymmetric clipping with MOSFET (2N7000) + Ge (1N34) on one side and 1N4148 on the other.

Used Toshiba 2SA478 with hfe in the 70-100 range with low leakage <120. But also didn’t mess around with leakage very much.

Give this one a go if you have some spare PNP Germs!
Some sound demos below:
1. Clean channel: bypassed then engaged with 75% gain
2. Dirty channel: bypassed then engaged, adds girth to the chugs

 

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