Passive preamp built with John's remote shallco attenuator kit

0 Members and 1 Guest are viewing this topic. Read 4166 times.

Ed Sawyer

  • Jr. Member
  • Posts: 22
hi Folks -

I recently built an autoformer preamp using the remote-controlled shallco attenuator switch kit from Bent Audio, and with Dave Slagle's 28-step autoformers. It was a build I did as a commission from my friend Tim Dean. I am quite happy with how it worked out, and sonically it's super clean and clear. I didnt' regap the autoformers so they are at the stock gap, which seems to make *plenty* of bass in my listening experiences so far. I ended up using silver wire in teflon tube, rather than the supplied magnet wire, since that is what Tim wanted and also I didn't have a solder pot. Wiring them was a bit tedious but not too bad.

I compared it with the Tribute nanocrystalline amorphous toroid autoformer preamp I also built a while back, and they both sound terrific. So close in sonics that I couldn't pick a favorite. The Slagle *seemed* to have a bit more bass, but it's hard to do direct immediate back-to-back comparisons. Both were excellent.

The remote attenuator is a great kit! Superbly engineered, and a breeze to build and use. Worked great right out of the box. The shallco switch has plenty of strength in it's build and design. I hung the whole thing off the front mounting holes w/o any additional support for the motor, and it worked fine. (I was a bit worried about that, but it was a non-issue). Also, I put a long/large knob (about 4-5" long piece of 1.125" solid billet 6061-T6 aluminum) on the shaft, and even that was a non-issue, the motor still had plenty of power to turn the switch.

( I would have built this with some TX-102s but Tim wanted to try the Slagle autoformers, he has an active pre already with tx-102s.)

pics here:

(FWIW, I put about 40 hrs labor into this project.)

Thanks again John for making such great products and well-engineered designs!



Love it! Excellent work.  :thumb:  I need to get off my ass and finish my Slagleformer preamp.