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I think you are looking for a Threshold SA-12E
They pop up here sometimes and on Ebay too
Good luck
Peter |
Threshold didn't make a 1 horsepower Class AB amplifier in the 80s. They did make one in the late 80s/early 90s. It was called the S/1600e. It used the same chassis as the top of the line Class A SA/12e but was biased to operate in AB.
From my book...
Rated output: 1 horsepower @ 8ohms @ <0.15% distortion
Bandwidth: flat @ DC to -3dB @ 100KHz
Slews rate: 100 volts/uS
Output current capability: 35 continuous/200 peak amperes
Power: Two 1.2KWatt transformers & 216,000uF capacitance
Input Impedance: 50K ohms RCA/600 ohms XLR
Output Impedance: 0.1 ohm
Gain: +32.6dB
Weight: 130 lbs each
Personally, I prefer the higher biased class A designs at lower wattages. YMMV.
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You might have more luck finding a pair of SA 12e's and sending them to some one like Jon Soderberg of vintage amp repair to have them re-biased to the S 1600e's specs. The SA 12e's pop up from time to time, but the S 1600e's not so much. |
Unsound - I don't know for sure about the Thresholds - but it may not be that easy as the higher wattage requires a higher rail voltage which would require a different transformer not to mention that the components (Capacitors/Transistors) in the circuit may not be rated for the higher voltage required. Just adjusting the bias current does not "make' more watts.
Its all a matter of how much heat one is willing to accept or how much heat the sinks can dissipate. Rail voltage x bias current = heat (W) so if you turn down the bias current you can "turn" up the voltage (not that easy, requires changing the transformer) and your amp would have more watts, but less of them in class A because of the reduced bias current,
I have found that most output devices have a "sweet spot" as far as voltage/bias current where they sound the best - running them at a higher voltage to my ears makes the sound "harsher"
Thanks
Peter |
I've been told that the two different amps are based upon the same chasis etc.. Threshold was very conservative about their use of transistors, with only about 20% of total capability actually used. As was mentioned above, each unit had two very large trannies. Nelson Pass has written a paper which would agree with the "sweet spot" concern. Either asking Nelson Pass on his section of the DIYaudio.com site or speaking with ex Threshold tech Jon Soderberg at vintageamprepair.net would probably give the most difintive answers. |
You could call Threshold Audio and see if they can help you. please see
http://www.threshold-audio.com/ |
Have the manual right here. Same # of per channel output transistors 64, same uF size power supply = huge .25 Fahrad (key is cap voltage rating), bias current almost identical 1.1-1.2 amps with the lower the 12e, same peak current output 200 amps (35 for the 1600e versus 70 for the 12e class A). This suggests to me that you can tap the transformer to change the voltage & I believe NP told me once it was possible for my S/550e. Ask him at diyaudio or ask Jon. If I saw one I'd buy a 12e but I think they're very rare and I've never seen a S1600e here. |
Component wise, the SA12e and the S1600e are identical. |
Pbnaudio, study the STASIS design and you'll see. |
Higher bias into class A results in a more sweeter sound also. That is why Nelson preferred the 60 Watt stereo SA3.9e. Relative to the other SA series Thresholds, it was biased higher into class A per watt.
Main issue is heat. |
I've seen a few SA12e amps for sale over the past 5 years. Never a S1600e. But if you found the SA/12e amps, I think you'd be hard pressed to give up their class A sound just to convert them to 1 hp under class A/AB bias. I would think it more likely for an owner to go the other way. Perhaps that's why there aren't that many S/1600e amps out there. |
Considering the other option the OP mentioned, I suspect the OP might have a unique application for these amps. |
Why don't you just get a horse? |
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thank you edyun.yes i am aware there is no mechanical power amps but there is a conversion math,watts to horsepower and in reverse.your book reads 1 horse power at 8 ohms.how many watts makes one horsepower and some years ago i called pass labs and talked to mr pass.he did not tell the model i seek.so thank you for itell. |
1 horsepower is about 750 watts. |
A little late to the party here. The SA12/e is a parallel amp design and the S1600e is bridged design. You would need to add a second FEB to the 12/e to convert to the 1600e. Both the SA12/e and the S1600e have 2 amps inside each monoblock. Parallel set up in the 12/e and bridged in the 1600e. Thus you need a second FEB for the inverted bridged connection to the second amp in the 12e to make it a 1600e. But, if you have a 1600e, you should be able to convert it to a 12/e with whats in there. I got this from the service manual of the 12/e which I have posted on DIYAudio. I have not read enough into it to know how you'd set bias, but I'm sure that could be figured out.
Disclaimer .... I may not really know what I'm talking about. If you have a 12/e or 1600e, better run this by Mr. Pass before you dive in with wire cutters and soldering iron!
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