Akais, Ampexes, and Magnecords

This is the first draft of the donor amps that I have and what I intend their purposes to be at xfmr. I'll also note what my intentions for modification are for each.

Akai/Roberts Tube Reel to Reel Monoblock Amplifiers:

I have modified over a hundred of these now and have worked out about a dozen different designs that I have installed in the various similar chassis. However half of those were oneoffs that I don't intend to make again. Items that will for sure be included at the station made from these donors will be two each of the 2xPre, Pre+Amp, and Plexi8 units that I have been selling online for a few years now. The 2xPre has, you guess it, two preamps per monoblock. The Pre+Amp units have a mic preamp and simple low-watt instrument amp in one box. The Plexi8 is a modern twist on the Bassman/Plexi preamp and tone stack combined with a single-ended, class A power section with about 8 watts full bore! They will be presented in as a pair of the original wood tape machine cases, with one of each of the three different module per case.

I also plan on installing some synth and fx modules in some of these donor amps, plus some of the pulled output transformers not used in the modified 2xPre units will see use in other studio amps.

Ampex 601 and 602 Reel to Reel Monoblock Amplifiers:


I have made a dozen or so of these and while they all turned out great. I do slightly different things with the 601 and 602 because of the different power transformers and the donor tubes. The 601 has a 5Y3 tube-rectified high voltage supply, AC heaters with EF86 and 12AU7 audio tubes while the 602 has a solid-state, voltage doubler high voltage supply, DC heaters with 5879 and 12AU7 audio tubes. I like the original Ampex input transformers on the 601, if they are included, but I actually prefer the Altec/Peerless 4722 as they are easier to find and sound better to me. On the 602, the original 'peanut' transformers are pretty neat. Though they don't have the bass response of the Altecs they do have a great sound of their own. I plan on a single 601 and a single 602 together in a portable case. They have two preamps per monoblock for a total of 4 preamp/DI channels.

Magnecord PT-6 and M33 Tape Machine Amplifier Monoblocks:


These Magnecords have amazing iron in them. They are all well made and have tons of potential. The PT-6 is perfect for either a guitar/bass amp or a mic preamp/limiter. I plan on making one of each. The amp will have all octal tubes and will be loosely based on an early Bassman. The mic preamp/limiter unit will have a one-bottle style mic preamp made out of a single 6SN7 feeding a tweaked Federal AM-864/U style limiter. The M33 unit will have a tweaked REDD47 style preamp (with a working Magic-eye tube!). The M33 REDD47 and the PT6-J Pre+Limiter units will be put together in the portable case. The guitar/bass amp will come in it's own portable head case.