VSP LABS Trans Mos Amplifier

[dkbb12]

I own one of these, bought it new in 1981. It was gradually deteriorating for years, finally blew last year (taking 2 woofers with it...). Are there any CURRENT schematics available? Would love to find someone who can bring it back to life. It was a great amp, though it did run hot. ~ Dan

[jbol]

considering that there was some damage to one channel including the pcb's, AND the parts were expensive, AND the FETs were subject to degradation, I decided that I got a good deal on a big power supply and massive heat sinks and am looking to use some diy circuitry instead of repairing it. The only circuit diagrams I am aware of are those listed in the thread but you can always google. Yes, the one channel did sound nice.

[bear]

the links to the pdf schematics no longer function...fyi.

[jbol]

If I can find my downloaded files I will email them to you

[gmann44]

I met the owner back in 81 through a friend of mine that worked there. At that time the company was based in Ann Arbor MI.

I was very impressed with which the equipment produced such a clean and warm sound. However at the time, after being on for a while under a rather lite load, I felt the heatsinks and thought, man them are hot!

In theory I thought that this thing was overheating but still sounded good. So then began to think that this was normal.

But now 28 years later I have come to think my theory was indeed correct. After seeing the posted .jpegs, I feel these Amps were 1. Being driven too hard even at low volume. 2. Were designed in a way to produce clean sound that a tube amp would deliver.

I remember talking with Juan, and his comment was to design with the power and feel of a tube amp.

Don't get me wrong, I thought they were a decent amp but poorly designed in regards to lasting. Semiconductors can only last so long under that type of driven load!

[djk]

6550s in an Audio Research D75 that is run hard last about 3~6 months, years from these FET amps seems OK to me.

Maybe after 10 years you should invest in new outputs (I know I do whenever there is a failure in one channel after a unit has been in the field over a few months. I repair the damged channel, and replace outputs and drivers on the un-damaged channel. If it is over 10 years old I replace all the small electrolytics too).

[gmann44]

I do know that these amps, and others like it do run hot. However after looking at the posted pics earlier, I did notice that a connector and one circuit board did have serious heating problems. Not saying that the circuits are of poor design, but more so in dealing with the heat! It's been a long time since I have seen these units. I now seem to think that if the cabinet had a different design, and a cooling fan, that the problem could have been eliminated.

[Bhu108]

I am interested in what you found out about your VSP Labs Trans Mos amplifier

[DARCOMP]

Originally Posted by TomWaits

Here is a PDF containing a working production version of the VSP Labs Transmos 150.

Lots more work to do but I see a full restoration coming my way and if I'm lucky there will be tweaks. Any thoughts from the DIY folks here? I'd love to hear your impressions of this circuit!

Hello Tom
this link unfortunately NO LONGER WORK as it seems the website is defunct....I'm also the proud owner of the pristine TRANS MOS but not the gold version and am affraid to power her up before checking the voltages biases etc without the loads...As you can tell i dont have much confidence in the FUSES (if any) and i do not want to burn any speaker drivers...FYI previous owner drove very unstable and demanding THIELs 3600 with it and only sold it because he purchased a monster AMPZILLA dirt cheap...any info would be appreciated--primarily working schemat in PDF no longer avail...BTW did you get your unit going yet,,,THNX for posting all other stuff re. this dinasourus...Best of luck 2 y'a