Car Audio Amps by Nelson Pass

[markmelheim]

Can someone shed some light, or if Mr Pass would be so kind to chime in. Does any body have a list of mfg's such as the adcom 4702, Or just list what we know of............... CAR AUDIO ONLY KIDS

Thanks mm

[tsmith1315]

When the Soundstream amps first came out, rumor was Papa designed them. I have no confirmation, but at least the D200 was a simple, elegant design. I wouldn't be surprised. These models were D60, D100, D200, A50, SF90, and MC500. The A50 was marketed as "power transistors fully energized by power supply regardless of signal level", Class A.

Alphasonik's early "Class A" amps were manufactured under license by Threshold as early as 1984, possibly before. You can look at idle current and see they must use a sliding bias, and IIRC, is what Threshold was doing with some of their own products at that time. That's a secret I prefer to keep, as these amps can be picked up cheap.

[Nelson Pass]

Adcom and Soundstream very early production was based on
prototypes I provided. I don't recall Alphasonic in there.

[markmelheim]

Thanks for the info,

[tsmith1315]

Alphasonik was a part of Visonik back then, and the wording I remember in the manual was something like "Class A circuit manufactured under license from Threshold."

Current limited TIP35/36 amps using a 555 timer-based SMPS.

Now I'll have to tear the shop apart looking for an old manual to convince myself I'm not crazy!

[1moreamp]

Originally posted by Nelson Pass
Adcom and Soundstream very early production was based on
prototypes I provided. I don't recall Alphasonic in there.

Love my Adcom's, thank you for your influence... I knew it was your design handy work the minute I looked inside the first one back in 93.
The Rep said it was indestructible, so I short circuit tested a bridged 40 watter, with a 50 amp HP Harrison supply, and no damage occurred... I was simply amazed, and so was everyone else in the building. Especially as the amp went right back playing just like nothing ever happened to it. Simply amazing, and sonically very listenable, even for long periods of time. < unlike many other car amps back then that caused listening fatigue within 20 minutes or so. I still own 4 of them mint and NIB.

I also remember the early D series SS amps. I remember that they were also a hit the minute they came to market. They made SoundStream's name as I recall...Nice work, and Thanks again...

[oPossum]

Originally posted by tsmith1315
Alphasonik was a part of Visonik back then, and the wording I remember in the manual was something like "Class A circuit manufactured under license from Threshold."

Current limited TIP35/36 amps using a 555 timer-based SMPS.

Now I'll have to tear the shop apart looking for an old manual to convince myself I'm not crazy!

The A-2125 (circa 1984) was TIP142 x 3 + TIP147 x 3 per channel.
Regulated power supply is SG3524 with 8 x TIP35.
Has banana jacks for power and speakers.

The A-2125 Mk II (circa 1985) was TIP35 x 3 + TIP36 x 3 per channel.
Regulated power supply is TL494 with 10 x TIP35
Fixed power wire and molex for speakers.

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

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

The MA-2150 and later where make in Korea and have regulated MOSFET power supplies and 2SB/2SD series outputs.

Alphasonik A-2125 Schematic

A-2125 Pictures (large files!)

Amp section
Power supply
Heatsink

[oPossum]

.

[marko]

i'm a big fan of the early soundstream amps, i currently have a d200II but i reckon my old d100 sounded better for some reason or another

what happened on the series II amps?

[lumanauw]

That Alphasonic, indeed using NP's patent. What's the bias for output stage?