Just finished building and testing

[W5FH]

Here is a one-of-a-kind amplifier -
     Just finished a build using these circuits:
1. Preamp circuit of the Soldano Astroverb, except for reverb tank driver. Used the old standard Fender parallelled 12AT7A into a nice quality transformer with dwell pot feeding the grids. (spent a lot of time verifying out the Astroverb schematic as the ones that turn up are incorrect).
2. I used the fixed bias HiWatt phase inverter circuit with triode cathode follower/bias regulator.
3. Push-pull pair of Tungsol 5881's with bias adjust and balance.
4. Sluckey Tremonator vibrato circuit.
    This build started from a blank Fender Deluxe Reverb steel chassis and goes into the matching Deluxe Reverb cabinet with single 12" Celestion speaker. Will try to upload some pictures. The only thing I did not like the looks of were running the output transformer leads across top of chassis. The guitarist that is going to use this one wanted a weight-balanced cabinet. Saw no other way to do it and did not want transformer leads near preamp circuitry.

[W5FH]

Here is a view of the chassis underside with all parts mounted and ready to start wiring.

[W5FH]

Here is a view of completed amplifier being tested, measuring plate current of one tube. From examination of wiring my radio building background is probably telling on me. I can't get away from point-to-point wiring! But I will say the amplifier is very quiet. I used old stock Mallory polyester films (1 uFD) for the cathode bypasses.

[W5FH]

An error - I meant Sprague 431P film caps, not Mallory. If you notice some black goop near tube bases on chassis underside I made a huge mistake that nearly cost me the chassis. I punched out 9 pin socket holes for some imported sockets that I did not thoroughly check out, I thought they were of good quality. They needed a 7/8" base hole and had same mounting screw pattern as my old stock US stock. Since I am getting low on old US stock 9 pin sockets I thought I would try out these imported ones. After mounting the sockets, ahead of wiring, I install old no good tubes in sockets to get and keep pins in position. I noticed some of the sockets separating at bases; the bases were a two-piece design held together by the center grounding post pressed in. I had to remove all of them and install US sockets, however the US ones only require a 3/4" base hole. When installing tubes I noticed some slop and movement of bases so I applied some epoxy in gaps. A hard lesson learned.

[tdvt]

Looks very nice!
Wondering what pot value you ended up with for the dwell control? 1M pot for the 1M resistor?

[W5FH]

Hello TDVT -
    Yes, used a 1 meg linear pot as seen in Fender dwell circuits with bottom end to ground, top end to coupling capacitor (.001 uFD) and wiper going to grid. I had read quite a few comments about the Astroverb having a weak reverb so I thought I would drive the tank a little harder. I sure like that transformer from MPS, it is a 3 watt unit with quite a bit more core than most reverb driver transformers. 25K single ended primary to 8 ohm secondary. I try to use the best iron that I can get reasonably; the APD-8025H output transformer (by Heyboer) has worked out well in other 5881 push-pull builds. My B+ is running about 390 VDC to output transformer center tap, a little on low side for 5881's but in studying the Soldano preamp voltage readings before build observed it runs at lower voltages so I used the Hammond transformer with 550 VCT secondary. Choke is a Magnetic Components 10 Hy at 100 mA. I used the JFX coupling/tone capacitors.