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Old 24th June 2008, 01:22 AM   #1
jkeny is offline jkeny  Ireland
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Default Solid State Tabor Amp

Has anybody built this & can give their impressions?

What changes are needed to the schematic on GP's webpage for the 25W version which uses FQAF5N90 900V 90W MOSFETs running in parallel.
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Old 24th June 2008, 06:22 PM   #2
jkeny is offline jkeny  Ireland
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Uh! So nobody has built one of these?

What's putting people off - the large heatsinks needed for the Class A dissipation? Or the 6 CCS circuits needed? Or something else?

I believe the sound as described by Gary Pimm himself is cleaner than the tube based Tabor amp which is saying a lot!
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Old 24th June 2008, 06:35 PM   #3
chrisb is offline chrisb  Canada
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Default Re: Solid State Tabor Amp

Quote:
Originally posted by jkeny
Has anybody built this & can give their impressions?

What changes are needed to the schematic on GP's webpage for the 25W version which uses FQAF5N90 900V 90W MOSFETs running in parallel.

Quote:
Originally posted by jkeny
Uh! So nobody has built one of these?

What's putting people off - the large heatsinks needed for the Class A dissipation? Or the 6 CCS circuits needed? Or something else?

I believe the sound as described by Gary Pimm himself is cleaner than the tube based Tabor amp which is saying a lot!

If this is the amp that I heard in Portland during the week of VSAC08 , "clean" wouldn't begin to describe it. There was opportunity to hear some very interesting gear at the show, but this is quite simply the most visceral and concurrently invisible amp I've heard in 45yrs of listening.

With that special CD of live broadcast feed of "Carmina Burana", I have no words to describe the experience, other than transcendental and paradigm shifting. Of course there was a lot more of Gary's soul and brilliance in the system than just this single piece.

Yup, it's a toaster alright, and probably not appropriate for any less than a very accomplished builder.
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Old 24th June 2008, 07:14 PM   #4
jkeny is offline jkeny  Ireland
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I didn't know GP was at VSAC08. Did he have a room or was he in with somebody? I know John Swenson was there with his BDT preamp (which uses some of GP's CCS circuits).

Did the amp look like the attached - this is the "Big" amp version (25W) & here's his description:

Quote:
Since this project I have built the "Big Brother" to this amp. The larger version runs B+ at 350 volts and the output stages are idling at 180ma. The output transistors have been upgraded to pairs of FQAF5N90 900V 90W MOSFETs running in parallel. The "big" amp puts out 25 watts per channel and measures very similar to the 10 watt version. It was used to power the Bastanis Apollo speakers at RMAF a few years ago. Here is a photo of the "big amp". Down side to class A solid state is the heat sinking needed. This amp dissapates 250W idling and stabilizes at about 60 deg C. Need more heat sinking...
I may just go with the "little brother" version which outputs a clean 7W. I wouldn't consider myself a very accomplished builder but i can handle the high voltages and have successfully built a couple of his CCS on veroboard. This amp is just 6 of these modded as pentode emulators.

Chris, tell us more about the GP equipment you heard, please
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Old 24th June 2008, 07:37 PM   #5
chrisb is offline chrisb  Canada
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Gary attended the show, but didn't display product.

Thanks to Bud Purvine, it was a too-short visit to Gary's secret lab in the heart of urban Portland that resulted in this epiphany. Due to Gary's rally-class driving and the crazy traffic, I doubt I could find my way back even with a GPS - but then my brain was still trying to process what I'd experienced, so I'd probably have been a traffic hazard in my own neighborhood.

As for the system, I don't recall too much discussion regarding the transport ( IIRC, a generic CD or DVD player) and DAC. The "pre-amp" was a passive transformer volume control unit, with dual outputs to the Tabor running the dual mids and ribbon tweeter with passive XO, and Behringer XO, the latter driving another generic SS amp (Parasound?) to the subs.

Needless to say the name plates on any of the equipment not handbuilt by Gary were probably meaningless anyway, as they were all highly modified, including more than a few pieces of O'Netic iron.

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Old 24th June 2008, 07:45 PM   #6
jkeny is offline jkeny  Ireland
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Tell us what you heard though!!! Edit: Cross posts - so it doesn't seem like this amp was featured in what you heard? Sorry, I reread your post & see the Tabor mentioned!

Also, I was thinking of combining John Swenson's BDT preamp with interstge trafo with GP's SS Tabor output stage.

Does anybody think this is a runner?
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Old 24th June 2008, 08:05 PM   #7
chrisb is offline chrisb  Canada
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Quote:
Originally posted by jkeny
Tell us what you heard though!!!
The amp I heard definitely looks like the one pictured, but I'm far too experienced to suggest it would be a magic panacea to an otherwise poorly implemented system - which I don't think Gary could assemble on a bet.


Soundstage that easily expanded beyond the boundaries of the room, and effortlessly real dynamics, without the major colorations of large horn based systems that were available to hear at VSAC.
Depth and layering of voices in that absolutely stunning recording of the Carmina Burana that bordered on hyper-realism.


Since I've never availed myself of the opportunity Live performance of a large choral work as this, and had only heard some of what I thought were "decent" commercial recording of this piece, I had no idea the mass and visceral impact it could achieve.

On a couple of recordings I thought I was familiar with (for example Rodrigo y Gabriela "Stairway to Heaven" and "Orion") there were subtleties of texture, timing and space between the notes that just made more emotional sense.
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Old 24th June 2008, 08:18 PM   #8
jkeny is offline jkeny  Ireland
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BTW, which recording of Carmina Burana are you talking about?
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Old 24th June 2008, 09:11 PM   #9
chrisb is offline chrisb  Canada
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Quote:
Originally posted by jkeny
BTW, which recording of Carmina Burana are you talking about?

This is not an official commercial release. If I have my story straight, it was a performance of the San Francisco Symphony and local choirs, broadcast live over FM, as well as recorded for rebroadcast through associated classical music FM stations. The version that I heard was apparently recorded from one of these FM transmissions.

That this degree of astounding fidelity and musicality was available over the air is nothing short of amazing. I love my local NPR FM station (KPLU), who broadcast some wonderful live jazz performances, but nothing I've heard yet approaches this particular performance.
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Old 24th June 2008, 09:25 PM   #10
jkeny is offline jkeny  Ireland
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That's very interesting - I've herad people say to me that some FM broadcasts are stunningly realistic but never experienced it myself!

Is this recording available through any, ahem, "unofficial" channels?

So, still no builders of this amp? - I'm sure there are some tube Tabor builders! - I know Shoog has done his interesting version of Tabor clone, which I'm hoping to hear soon.
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