, Trans-Nova Twin-200

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Darryl Chagi2006-10-22 04:56

I am looking for a transistor for my TNT 200. Toshiba is no longer making the 2SK146, the one I need. Does anyone have a few they could sell, or let me know where I could buy some. Or know of another FET that could takes its place. Thanks. Darryl


Andy Szabo2007-01-20 22:18

Try contacting Roy Esposito at \'Sounds Like New\' at soundslikenew@prodigy.net. SLN does good Acoustat repairs. Roy may have the parts you need, or may be able to suggest an available substitute.

Bob Rolle2011-06-23 20:10

Acoustat model 1 +1 and Trans nova twin 200 amp for sale with monster speaker cables. Will not ship. MA resident.

Roy A. Esposito2011-07-17 19:59

July 17, 2011

I am very much alive.

I am No-Where near retiring .... and over many years have
come up with astounding improvements, variations and restorations
for the Acoustat MK and Spectra Interfaces
and even more so the Trans-Nova amplifiers (TNT-200 and TNT-120)
and Trans-Nova Preamplifier (TNP).
I also renew the earlier and more rare, Acoustat MRP and RP-2 preamps.

To my chagrin ----
Folks don't realize I was many years younger than the
other principals at Acoustat, back in 70's and 80's Fort Lauderdale.
About half their age at that time.

I am happy to continue lovingly working with Acoustat products.
I do this with a fully functional laboratory and stockroom
of original .........and improvement parts.

But please realize that... in 2011....
this is part-time work.... in addition
to my regular full-time engineering/consulting work.

So it can take a few weeks in total, for me to work my
Acoustat "magic"...... as my client's have often
described the results.

I hope the above will help explain why I don't
provide a phone number, except to established clients,
and I prefer email contact instead. I also prefer my work
and "word-of-mouth" to speak for itself
....instead of having and spending time maintaining a website.

There are others that offer work on Acoustat products.
Fancy words .... Fancy websites.
But NONE of them worked for the Company.
And to correct the mess.....
Folks usually end up with me despite the glowing website tetimonials.
That's just sad.

I very much appreciate all of you, who continue to revere...
and enjoy...
the magnificent design works of Dr. Strickland,
and our original Acoustat Engineering Team.

May we all enjoy the Music,

Roy A. Esposito / soundslikenew@prodigy.net

Alfredo M. Claussen2011-08-22 21:57

Since I live in Mexico City, I've only listened to Acoustat electrostatics twice: in a Showroom in Houston TX in 1982 and at a local dealer here in Mexico. I perfectly remember the truly amazing character of the soung from those old Acoustats: the most accurate and clear bass drum of all! My neighbor and me assembled and built many dynamic multiway speakers back in 1972 to 1985, and because he was an accomplished drummer, I was acustomed to the REAL sound of a drum set. I've never heard another speaker that reproduces the exact color and tonality, attack and the "membranaceous" quality of the bass drum like the Acoustats; even when the acoustats could never reach the true volume and intensity of the real bass drum of a recorded drum set. But anyway it was by far, the closest sound to the real one. amclaussen, Mexico City.

P.D.: Mr. Esposito; could you please tell us what was the relationship of Acoustat with Mr. David Hafler, please?

Andy Szabo, Acoustat Answer Man2011-08-22 23:52

In regards to David Hafler's relationship with Acoustat: Acoustat suffered a bankruptcy in '84, and the company was subsequently purchased by the David Hafler Co of Pennsauken New Jersey. I was transferred from Hafler to Ft Lauderdale Florida to run the operation, with Jim Strickland continuing as Chief Engineer. In 87-88, Rockford Corp purchased both Hafler and Acoustat divisions, and eventually moved both to Tempe Arizona. Despite Rockford's good investments in both brands, Acoustat was sold to an Italian distributor in '91, then to China, but I'm not sure about the status of the trademark now. Hafler Home electronics were discontinued not long after Acoustat's sale,(along with my job!) and the seemingly successful line of Hafler Pro electronics followed a few years later. I believe the trademark is no longer in use. Please note the dates are approximate, subject to my fuzzy memory!

Despite being out of production for 20+ years, Acoustat electrostatic elements have shown very few signs of degradation, and with a little attention to aging electronic components, the speaker systems continue to deliver their original performance. Check the used market - it's not too late for you to relive that experience from 1982! I'm still listening to my Acoustats and have no plans to change as long as I can keep them working (and you can bet I have a cache of spare parts!)

Alfredo M. Claussen2011-08-23 16:21

During my university years (Chemical Engineering), I paid part of my expenses by assembling, building and installing audio equipment, both home high quality and a few professional ones, like a couple of "Discotheques" and Auditoriums. Free trade then was non existent, and the import rules were outrageosly restrictive, so I had to use some components made in Mexico in my speaker design and in some cases (rich clients), I imported professional units from JBL and built the cabinets and crossovers in Mexico, better built ones BTW (hand selected caps and carefully measured inductances). At that time I worked for a couple of years for a Brazilian company called "Gradiente" that made good quality amplifiers with circuits adapted from JVC and some original ones. After some years, I discovered the DYNACO brand and started to import their Solid State and a few Tube amps, all in kit form (to be able to import them as "electronic components" instead of "HiFi components". Later on, the first Hafler DH-101 Preamp and DH-200 Mosfet amplifier appeared, and I rushed into assembling many of them to provide my customers with truly clear and powerful audio. After a couple of years I started modifying those designs slightly (to replace some cheap parts), still using my designs on speakers, now with Philips soft dome tweeters and midranges, and from time to time MB and Peerless, Seas and Vifa too. Then "The Audio Amateur" and Speaker "Builder" magazines brought many more mods and my sets were very well received, but I never went above the "artisan, hand-made level". With the advent of the personal computer, interest in Audio (High quality) almost vanished, and it stopped to be a business at all. I still have my Hafler DH-101 Preamp and XL-280 Amplifier much modified and sounding perfectly, after all these years (1979 the Preamp, 1989 the Power amp). We all owe the late David Hafler for his magnificent philosophy about honest, no frills, inexpensive but elegant designs; absolutely no non-sense approach. By the way, the slightly modified mosfet XL-280 can easily drive the Acoustats almost as well as the later Trans-Nova (TNT) designs. I remember a memorable session at the Hafler dealer in Mexico City in 1990, when we rigged the famous Hafler null-test, and made a well calibrated XL-280 sound even cleaner than a much over hyped amp which price was more than NINE times the modest cost of the Hafler, and the ultra expensive one was more prone to ultrasonic oscillation and cable sensitive!... the owner of the ultra expensive amp sold it and we sold him a triple set of Haflers in a Tri-Amped system that sounded much cleaner than his set. I only wish we could still find the Hitachi Mosfets to continue using them in the old Haflers.

Andy Szabo2011-08-23 18:38

I see the Hitachi MOSFETS occassionally on eBay, both in the original TO-3 metal cases and the later plastic flat-packs. Set-up an eBay email notification for "Hitachi MOSFET" and you might find some!

Roy A. Esposito2013-09-06 12:32

Hello Friends --

This is just to let you know that my email contact
has recently changed. It seems AT&T/Yahoo could no
longer support my very old prodigy.net email address.
For those of you requiring fantastic restorations
and upgrading of Acoustat MK and Spectra Interfaces
and Acoustat Power Amplifiers and Preamplifiers
my new email address is


(please notice the dots/periods between the words)

Email is the preferred method for initial contact with me
for Acoustat Service and questions.

Thank you for your continued friendship, kind comments and reviews,
and support of my work.

All the Best,
Roy A. Esposito

Vince Maida2014-01-20 15:40

There are a couple of potential reasons for the blown output FETS:
1. Since the amplifier does not use a source resistor in series with the output FETS to circuit ground it is essential when replacing the FETS that you match the VGS of the FETS to within about 20 millivolts or less. The reason is, for devices in parallel, with unbalanced VGS, the device with the lowest VGS will be delivering the most current. In the extreme case you can have a condition where it is delivering almost all of the current to the load and eventually fail. The best way to do the matching is to purchase 2X as many FETS as you will need from the same date code (manufacturing lot)since the VGS spread in the same manufacturing lot will track quite closely or failing that add about 0.27 ohms in series with the source to ground for all of the FETS. I am currently trying the SEMELAB BUZ900 (N channel) and BUZ905 (P channel)FETS which I have been able to match VGS to within better than 10 millivolts at 700 ma. They are available in the US from MOUSER Electronics for $10.57 ea in 10 QTY and Farnell in Europe.
I will post the results for these devices shortly.

2. Amplifier instability i.e. High frequency oscillations. Mosfets have a tendency when connected in parallel to oscillate at RF frequencies. This can occur when the amplifier is driving some types of reactive loads.
The fix is usually to add a lossy element (resistor) in series with the gate as was done in the TNT-200. The resistor fix does not always work by itself and the addition of a 47 pf silver mica capacitor from gate to drain for the P channel FETs and 22pf across the N channel FETS becomes necessary to avoid the mysterious oscillations/failures. Adding High permeability ferrite beads to the gate resistor leads will also help to discourage the oscillations.

Vince Maida2014-01-21 12:27

Mysterious Output Mosfet Failures
There is another failure mode that I forgot to mention. When handing any MOS device always discharge your human body voltage to ground before handling them. The gate breakdown voltage of a Mosfet is on the order of 16-30 volts and electrostatic discharges can be in the thousands of volts which can cause an immediate failure of the Mosfet or a degradation of the gate insulation which will eventually result in a failure. When you buy the Mosfets make sure you receive them in ESD safe packaging and not in a standard plastic bag or else the damage will have already been done. Although the gates have significant capacitance on the order of 1000-2000 pf this still may not save them from ESD damage, so always use caution when handling the devices.

Amclaussen2014-01-23 02:02

You are absolutely right, Vince. Obviously, all the other cautions apply, like grounding oneself, using a static safe soldering iron, working on a static dissipative surface, avoiding synthetic fiber carpeting etc. Fortunately, my old "David Hafler XL-280" amplifier kit with the Hitachi Mosfets output stage arrived with the output trnasistors already connected ans therefore, there was much less risk; but a person handling the Mosfets by hand, your consideratiosn are a must.

Roy A. Esposito2014-04-08 12:52

I remain available for Restorations / Upgrades /Improvements
of the Acoustat MK Series Interfaces with the optional "Air Mod"
that I developed in 2008. Vast improvements of the Spectra Series Interfaces,
the Trans-Nova Series of Power Amplifiers for which I offer the incredible
switchable Monoblock and Balanced Input circuit Conversions
and restoration of the three models of Acoustat Preamplifiers.
I welcome your inquiries at
(please notice the dots between the words)

Joseph Fabricatore2019-02-22 08:10

Happy to learn that Ray Esposito is available. He did updates on my Spectra 33s and I could not be happier with the sound or the workmanship. Many thanks, Ray.

Roy A. Esposito2019-04-20 17:41

Hello Again fellow Acoustat Devotees :

I have always had....and continue to have
for exclusive use in my Acoustat service work
... all parts needed....originals and verified subs....
including the long obsolete MosFET's and J-FET's
for my repairs/upgrades/improvement "package".
of the Acoustat TransNova series 200 and 120 amplifiers.
Same applies to the "packages " for the Acoustat Spectra
and MK series Interfaces and the three models of
Acoustat Preamplifiers. All contact with me is exclusively by email :


Enjoy the Music !

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