I wanted to share the results of my recent revision of the Ultrapath linestage. The driving force for this work was to incorporate the S&B TX-102 with the Seiden dual deck switch for the volume control. To accomplish this, a new chassis was necessary to accomodate these new parts. I found a great deal on some African Mahogany so I went with that along with an 1/8" steel plate for the bottom and an 1/8" copper for the top. The original intention was to do a mirror finish on the copper, but because of surface flaws from the original manufacture of the plate which resulted in pinhead pitting, I had to abandon the idea. Not without a great deal of effort on my part to try to make it happen. If you want a mirror finish on copper, hire a pro to supply the material and do the work. Without the tooling and experience, it can become a very frustrating experience. Consequently I went with a powder coat finish on both plates.
In addition to the TX-102's, I added another choke plus a Cerefine 220uf to each channel in the power supply for additional filtering. I used a 4ga solid core copper wire as a ground buss in the center of the chassis. It grounds at one point and is attached with ground clamps to the plate.
The inside of the chassis had to be milled and countersunk in places to accomodate the switches and input jacks. These parts are intended to mount on sheet metal, not 7/8" wood. The input jacks mount through a piece of .065" copper and then the wood on the back panel. By doing this, I only had to solder one ground wire to the ground buss.
The output transformers are mounted on the opposite side of the chassis from the power transformer and all of them are potted. I wanted everything mounted on one chassis for the simplicity and hum is not an issue with this arrangement.
The wire used for the power supply was 21ga continuous cast copper and 24ga fine silver wire for the signal path. I use my own homebrewed power cord with this using fine silver wire. I haven't raced it against many commercial power cords, but it has been on top so far with some costing $600.
The previous volume control was a DACT 10K stereo attenuator that was a very good performer... until the S&B that is. I originally had a TKD 50K plastic pot in this circuit when it was first built three years ago. I then tried a Goldpoint 50K and followed that with the DACT.
Well after all this wind, how does the S&B perform in this circuit? In a word, fabulous! Soundstage height , width, and depth have all increased. Placement of the performers within that soundstage has improved with more body and sense of space. In terms of clarity, what was once a mesh of different sounds has become individuals interacting as part of a whole. A noticable increase in dynamics has also been noted.
My only real problem in wiring up the TX-102's was trying to run a ground wire from the trannies to the Seiden switch tap that goes to ground. Volume was greatly reduced with an annoying hum to go with it. Running the transformer ground directly to the ground buss eliminated the problem. Thanks to John Chapman for helping me solve that problem.
To those with active linestages that have considered the TX-102's. if you can accomodate the space that they need, do it ! A very worthy upgrade and cost efficient for everything that improves with it's use.
http://www.audioasylum.com/forums/tubediy/messages/25964.html there is a link in there going to pictures of this project
