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Old 16th August 2009, 10:53 PM   #11
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Quote:
Originally posted by oPossum


Both amps say:
"Class A Circuit Manufactured Under Licence of Threshold"
"U.S. Patent No. 3995228"

"Made in USA" (by Zed???)

Thanks for the info, oPossum! I'd love to have a first year A-2125.

Hmmm, maybe for all these years I've been extrapolating that ALL of Alphasonik's Class A amps in that era were under the same license as the A-2125... AND maybe assuming since the MA series used 555's as a supply vibrator, the earlier amps did as well. Just looking for excuses for my error.

The A-2125 was Alphasonik's first offering into the high-power amp market, 1984 indeed. It seemed a bit of a different animal with binding posts, and being US made. There was a lot of excitement upon it's introduction, and when the first one to come through the shop. All the shop regulars came by to see it in person.

It's not a typical early 80's Alphasonik amp. Looking at the pics, the PCB (2-sided epoxy?) and 1-piece rectifier are unlike the other Alphasonik amp's phenolic PCB's at the time. The transistors are mounted flat, PPI/Orion style, waaaay easier to service than the other models. The logo on the PCB insinuates they were very proud of this model. It's also wider overall and lower profile, indicative of the upcoming MA line's look.

I never heard any mention of who built this amp, I always assumed Alphasonik built it in Berkeley.

Inside the A-2125's typical sibling (A-265) was not pretty:

Click the image to open in full size.

The siblings for 1984 were the 'Class A' A-265 (their flagship amp until the A-2125), the A-255, A-240B, and A-225. All of these amps were made in Korea, as well as the upcoming MA and PMA series as I recall.

Here's a label the from the A-265, circa 1983:

Click the image to open in full size.

Looking again inside the A-265, indeed it doesn't use a timer-based supply, either. The control circuit is entirely discrete, no IC's whatsoever in the supply.

The 'Class A' MA-2035 and MA-2055 (same label as 2035), from 1986:

Click the image to open in full size.

And the 2055/2035's timer-based supply control:

Click the image to open in full size.

Thanks again oPossum, you've brought back some very old fun memories and renewed my interest in the A-2125...

Wanna trade something for one of them?

lumanauw:
Quote:
What's the bias for output stage?
Is it only using Papa's bias circuit?

125W@4oms in Class A with 37V rails sounds very generous.

They came with test certificates verifying power output at advertised distortion, but how far it would go in Class A mode may be best left to your imagination.

It's also a fairly simple, and elegant on paper. Perhaps a good candidate for DIY. At 8 ohms, lower output currents may allow extended Class A operation.
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Old 16th August 2009, 11:36 PM   #12
oPossum is offline oPossum  United States
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Quote:
Originally posted by tsmith1315
Wanna trade something for one of them?
I am looking for MA-2100s in good or better physical condition. Would consider trade of two MA-2100 for one A-2125. I have both the Mk I and Mk II.


The Alphasonik amps of 65 WPC or less used single sided boards and had unregulated power supplies. The A series where biploar supplies with a two transistor astable multivibrator. The MA series where MOSFET supplies with a 555 (usually).

The 100 WPC and higher amps used double sided boards. The A series bipolar supplies where volatage mode PWM. The MA series MOSFET supplies where current mode PWM (usually - some exceptions).

I don't know what was in the MA-2075. It was a short lived model that I never had access to.

The A-265 is the only "Class A" amp that does not use the Threshold/Pass bias circuit.
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Old 17th August 2009, 12:00 AM   #13
oPossum is offline oPossum  United States
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Large pictures of the A-265

1
2
3
4
5
6
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Old 17th August 2009, 12:20 AM   #14
oPossum is offline oPossum  United States
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Quote:
Originally posted by tsmith1315
There was a lot of excitement upon it's introduction, and when the first one to come through the shop. All the shop regulars came by to see it in person.
The local shop here had one on prominent display and the tech had one is his car. They switched from Linear Power to Alphasonik.

I had a BRS-1 rack with A-255 and A-240 at the time. A pair of "PYLE Driver" 10s IB on the rear deck. No rear full range speakers - just "front stage". Kenwood head unit. Not too bad for the era.

A few years later the MA-2100, MA-2150 and MA-2300 where introduced. Time for a new system.....

Sony CDX-R7
Four MA-2100 biamped front and rear.
MA-2150 driving two MTX RFL-8
MA-2300 driving two MTX RFL-12

Very clear and very loud (for 1987).

In '89 I switched to Alpine (7909/7390), A/D/S (PH15), PPI (2300), and Nak (SP-1010,SP-50,SP-5).

Retired from car audio since '92.
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Old 17th August 2009, 01:20 AM   #15
a.wayne is offline a.wayne  United States
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I still have a bunch of the original Soundstream amps which were sold as pass designs , Class A 50 , D100, D200 ..

The Class A amplifier kicked **** ..
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Old 17th August 2009, 12:47 PM   #16
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Quote:
Originally posted by oPossum


I am looking for MA-2100s in good or better physical condition.

I don't know what was in the MA-2075. It was a short lived model that I never had access to.


Yeah, I've been looking for an MA-2100, too. My favorite of all the Alphasoniks that I used in my own car.

Had it on a pair of 17W75's, with a... 2070? on D6200's up front with a TD-500 and Sony 1/2-DIN slave CD.

Before that (1986-ish), I had a MA-2075 and two MA-2035's on a pair 10" Vifa M25's with the D6200's and rear speakers that escape memory. Noisy little PEQ-7A, and an EX-3 with a Proton 203, then went to a TD-400.
Never looked into the 2075, and only kept the setup for about a year as I changed cars.

Anything non-Alphasonik you're looking for?


Quote:
I had a BRS-1 rack with A-255 and A-240 at the time. A pair of "PYLE Driver" 10s IB on the rear deck. No rear full range speakers - just "front stage". Kenwood head unit. Not too bad for the era.
I'm sure it impressed plenty of folks, that was a strong system for the time. That A-255 packed a good punch for ~50WPC. I loved my 10" Pyle's in IB.

Quote:
Sony CDX-R7
Four MA-2100 biamped front and rear.
MA-2150 driving two MTX RFL-8
MA-2300 driving two MTX RFL-12
Made a little change, huh? 1.7kW was enormous for 1987.

RFL's, man I had heard that in years. We called them the "Real F 'n Loud's".
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Old 19th September 2009, 03:32 AM   #17
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Quote:
Originally Posted by oPossum View Post
I don't know what was in the MA-2075. It was a short lived model that I never had access to.

The A-265 is the only "Class A" amp that does not use the Threshold/Pass bias circuit.
I don't know about an MA-2075, but here are some shots of my A-2075 I'm about ready to restore.
Attached Images
File Type: jpg A2075 001.jpg (156.3 KB, 921 views)
File Type: jpg A2075 002.jpg (137.8 KB, 313 views)
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Old 19th September 2009, 10:59 PM   #18
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Arrow No need for new car audio, but ...

I don't need car amplifiers, and I don't think that a car is a good place for listening music. Usually radio programs are poor quality (compressed) and investing money to a car amp would be futile. That is my opinion only. I don't mean to suppress anyone's project. Anyway audiophilia is much better compared to many other philias you can do in a car.

I have efficient 3 ohm loudspeakers (Goodmans Axiette) at home and 5W...10W amplifier is fairly enough power for driving them. The specified power limit of the speakers is only 5W, so over 10W maximum power would be useless. That means a small Class A amplifier is very interesting anyway.

I think that in the coming age of electric cars efficient speakers will be appreciated again. How about amplifiers... Class D?
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Old 9th April 2011, 07:12 PM   #19
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Default schematics for ancient Alphasoniks?

Hi ... realizing this thread is rather stale by now, but this forum thread is the best I could find today on these old amps (apologies if a faux-pas to ask this here) ...

Does anyone have at-the-least a schematic for A-225 (or perhaps A-240B since they shared the same instruction manual).
Same question for MA-2070 (while I'm asking).

In case anyone has encountered something like this before ...
My A-225 has been faithfully working since I bought it in early '80s.
Recently, I am getting abrupt-crackling/popping noise from both sides when hitting peaks (at about a volume needed when there is a lot of highway noise).
These are very momentary with no lingering recovery-time, and disappear at a slightly lower volume.
When balance is all-the-way to one side only, *both* sides do this still.
When balance is set to the opposite side, neither side does this.
So it appears that one channel is doing something that affects both.
I notice it also outputs a short noise/squeak sound when powered-on now that this issue occurs (from both channels).
(BTW, this amp is after the hi-pass side of an x-over - not used as a full-range amp; an MA-2070 handles the lows.)
My initial guess is that something might be going-out with the protection circuit, and I'm assuming this will affect both sides when tripped (an old Yamaha car-amp I once fixed worked that way).
Opening it up reveals no obvious problems or cracked/dried-out solder joints (and I'm hesitant to go and re-wet all joints in desperation).
Moving the main-gain-pot and the small trim-pots on the PCB did not help.
Hoping it's not a fatigued PCB, but would prefer to get a schematic before drawing one out myself and probing voltages.

Thanx in advance for any leads/help ...
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Old 13th April 2011, 06:13 PM   #20
a.wayne is offline a.wayne  United States
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The original soundstream "Class-a" amps ( circa 1986) supposedly designed by NP, run as hot as an F5 at idle, same power 2..... hmm .
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