Go to www.audiocircuit.com, Acoustat section, and you will find more information on Acoustat's direct-drive tube amplifier, called the Servocharge Amplifier, as used on Acoustat's original Model X and some of the Monitor Series. You should be able to locate schematics there. If I remember correctly (which I might not) the tubes used were 6HB5's.
If you are looking for two identical amplifiers with the intention of bridging them, I would strongly recommend against that. Each half of a bridged amp 'sees' only half the load impedance. Since the Acoustat is low impedance to begin with, presenting the amplifier with only half of that impedance is asking for trouble. A 250-watt amplifier of sufficient current output should be all that you need to get the most out of your Acoustats.
Oh yeah - I remember we talked bfore about your idea, which was NOT bridging amps. Ignore my previous comment (still good advice, but not applicable to your situation).
How is the Acoustat a "low impedance"??
The impedance curves published for the mk-121 interface on model 3s (iirc) showed a minima of ~6 ohms. The idea that they do not have super low Z dips like some (ML for example) is because of the Strickland double transformer/dual match design.
If you've got other information, I'm interested.
_-_-bear
The impedance curves published for the mk-121 interface on model 3s (iirc) showed a minima of ~6 ohms. The idea that they do not have super low Z dips like some (ML for example) is because of the Strickland double transformer/dual match design.
If you've got other information, I'm interested.
_-_-bear
I think one has to actually measure the impedance.
I don't see how "pushing them" changes the impedance.
The published curves, from Acoustat showed an impedance above 6 ohms, iirc.
It's easy enough to do an impedance measurement vs. freq, I'd do it myself but my Acoustats and myself are separated by some miles and my time is limited in audio to making a few posts - that is expected to change in a few months.
Any volunteers?
_-_-bear
I don't see how "pushing them" changes the impedance.
The published curves, from Acoustat showed an impedance above 6 ohms, iirc.
It's easy enough to do an impedance measurement vs. freq, I'd do it myself but my Acoustats and myself are separated by some miles and my time is limited in audio to making a few posts - that is expected to change in a few months.
Any volunteers?
_-_-bear
Technilly i'm a big 0 i tought that you ad to drive your speakers pretty hard for the impedance to go lower so i'm wrong guess i'll do what i do best KEEP LISTENING and leave the technical stuff to the savy people.
I've had a McIntosh MC-2500 that was no match for my Acoustats 2 + 2.
The meters were always on the right edge and the lights dimming.
Restek Exponent mono's no succes either, burned them up.
Cute Tube amps....
Anything with a low impedence switch on the back like these Resteks or Accuphase are suspects to fail.
Good matches electrically from that era:
1. Big Thresholds (not the bridged versions);
2. Krells in general of course;
3. Levinson ML-3, No.23, No.20
4. Jeff Rowland model 5, 7, 8 and 9
A few weeks ago I have been driven a Sumo Nine Plus that did a pretty credible job against a Krell FPB-600. Really amazing how powerful and musical that tiny amp sounded.
Btw Andy is really a great asset to have on this forum.
He always gave me great advice on Acoustat.
Best I heard on mine:
Threshold SA/1 optical bias, Jeff Rowland model 7 Transimpedance version and Levinson ML-2 (sadly these amps do not have enough max. outputvoltage (17 Volts) do drive them at loud levels but I found them magical sounding on my Acoustats.
Friend drives his with a ML 20.6 and they do sound wonderful also.
These speakers, I have them now for 20 years, need a really high quality frontend to drive them to their full potential.
The meters were always on the right edge and the lights dimming.
Restek Exponent mono's no succes either, burned them up.
Cute Tube amps....
Anything with a low impedence switch on the back like these Resteks or Accuphase are suspects to fail.
Good matches electrically from that era:
1. Big Thresholds (not the bridged versions);
2. Krells in general of course;
3. Levinson ML-3, No.23, No.20
4. Jeff Rowland model 5, 7, 8 and 9
A few weeks ago I have been driven a Sumo Nine Plus that did a pretty credible job against a Krell FPB-600. Really amazing how powerful and musical that tiny amp sounded.
Btw Andy is really a great asset to have on this forum.
He always gave me great advice on Acoustat.
Best I heard on mine:
Threshold SA/1 optical bias, Jeff Rowland model 7 Transimpedance version and Levinson ML-2 (sadly these amps do not have enough max. outputvoltage (17 Volts) do drive them at loud levels but I found them magical sounding on my Acoustats.
Friend drives his with a ML 20.6 and they do sound wonderful also.
These speakers, I have them now for 20 years, need a really high quality frontend to drive them to their full potential.
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The simple answer is yes, but not without a lot of work. Because the servocharge was designed to drive a full-range/full area speaker, its equalization would be wrong for a Spectra design that drives only a small portion of the speaker full range. I imagine this could be done, but it would require a thorough understanding of how the low level equalization works in the amplifier, and no doubt a lot of listening-n'-tweaking before you got the values correct.
Secondly, an external high-voltage resistor network would be required to drive the less-than-full range sectors, as is done in the normal Spectra transformer interface.
Personally, I'm thinking that such an arrangement, even if you got it to work reasonably well, would be inferior to using the Spectra transformer interfaces. But don't let that stop you from having fun if that's what it's all about! Just be careful - the servocharge amp contains LETHAL voltages with sufficient current available to knock you on your butt (and maybe not get up).
The pin-plug you are looking for is an Abbatron HH Smith #108. Here's one possible source, but I'm sure there are other distributors as well:
ABBATRON HH SMITH|108|Connector | Newark.com Products
Yes it is possible the best guy to tell you how would be Mr, Andy Szabo on this site ( Acoustat ) he is one of the original members of Acoustat U.S.A. i hope this can help you.
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I currently have a pair of Monitor 4's using the ServoCharge amps fully rebuilt/modded by Mike Savuto of Analog Associates. Due to space constraints in a new arrangement, I'm looking to convert them to 1+1's or maybe 2+2's.
What if anything is required electrically if I would go with 1+1's and having only 2 panels as opposed to 4?
Thanks in advance.
Bryan
What if anything is required electrically if I would go with 1+1's and having only 2 panels as opposed to 4?
Thanks in advance.
Bryan
Hi, Andy.
The pin connector is missing from the end of the bundle of wires that plug into the center jack of the high voltage board on one of my MK-121C interfaces. These are the wires that come from the diaphragm of an Acoustat 1+1. Would this Abbatron 108 pin be a good replacement for the missing connector?
Noel
Yes that is the pin connector that you need that pin is like an ice cream cone the wires go inside one end with solder and the other goes in the center jack. André