Theshold S500II

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Mods? How crazy do you want to get? Add caps to the power supply? Swap transistors in the front end? Rebuild it as an X? (Don't take me up on that last one. I've got too many projects on my plate already.)
The amp can be bridged by inverting the input to one channel and using the positive outputs <i>only</i>. Leave the negative outputs alone. The power will be x4 until you exceed the available current; it's a good idea to stick with 8 ohm loads so that this dosn't happen too quickly.
I've got two of the original S-500s. They make good low frequency amps. The mids and highs are a little cloudy, but still match or exceed a number of the units on the market today. Ditto for imaging and detail retrieval.

Grey
 
The one and only
Joined 2001
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I have a nice fix for that: new front end and higher bias.
I believe I've already posted the last (never to be produced)
front end for the Stasis series, delivered as I walked out
the door.

If you can't find the reference, let me know and I'll repost it.
It was remarkable for being totally DC coupled with almost no
drift at all and was improved in every respect over its
predecessors.
 
frugal-phile™
Joined 2001
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The one and only
Joined 2001
Paid Member
Yep, I was walking out the door about then, and this would
be the last piece of schematic I left, along with my white
paper "IGBT's: Threat or Menace"

Yeah, I know, I really amuse myself with that kind of humor.

I believe this schematic made it into some updates, but not
production. Its primary virtue was that there was almost
no thermal drift, as all the temperature coefficients of each
component were carefully measured and calculated and the
circuit was designed to null the PN junction drift throughout.
 
The one and only
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The paper discussed the difficulties of matching the
devices due to their dual device nature and the
inability to bias the mosfet part of the part at a
greater current than the Base current of the Bipolar
part. In an ordinary circuit, the driver is biased at
higher than the draw of the following part, which
improves the linearity and speed.
 
GRollins said:
Mods? How crazy do you want to get? Add caps to the power supply? Swap transistors in the front end? Rebuild it as an X? (Don't take me up on that last one. I've got too many projects on my plate already.)
The amp can be bridged by inverting the input to one channel and using the positive outputs <i>only</i>. Leave the negative outputs alone. The power will be x4 until you exceed the available current; it's a good idea to stick with 8 ohm loads so that this dosn't happen too quickly.
I've got two of the original S-500s. They make good low frequency amps. The mids and highs are a little cloudy, but still match or exceed a number of the units on the market today. Ditto for imaging and detail retrieval.

Grey
How would I do it. Reverse the inut of channel 2 and add to channel 1? Illenema@yahoo.com
 
Mr. Pass,

Speaking of which I just found the schematic of the Nakamichi PA-7, which I believe you designed a few years ago........:radar:

Jam

P.S. Nice use of transistors strapped to provide a voltage reference. Do they have lower noise than a zener?
 
The one and only
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You are assuming I have a schematic of this amp, as if
Nakamichi sent me one. Keep in mind that this was
primarily a licensing deal, and Nak was/is free to do what
they like, particularly as Threshold doesn't appear to
exist any longer and the patent is expired.

pass/ - he's listening to Rasa Exotica, which Jam would
probably like.
 
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