Car Audio Amps by Nelson Pass

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#85
tiefbassuebertr said:
in the pdf attachement you will find a audio power amplifier topology, that I have only find in this German amplifier models for car audio:
1) AMA Stereo 50
2) Protovision 264/Protovision 284
3) Smart Devices Stereo MkII
4) Alphasonik David 265
All this amps sounds very fine if the temperature is approximately 50 degrees but it seems to be very sensitive against variuos unwanted parasitic effects, because a lot of damage devices there are, as to read in various German audio/hifi forums.
Is this topology a slightly modified version based on a certainly topology from Threshold/Nelson Pass?

What I miss is the requirement for bias adjust and bias stability or bias servo unit like
Bias control for power amplifiers
Click to expand...
Nelson Pass said:
That's interesting. I developed a minimum peak hold detection circuit
for biasing output stages right about the same time. It comes from the
observation that in a push-pull follower the bias figure will be the minimum
voltage value from emitter to emitter. I recall that a prototype went to
CES, but by then I was on my way out the door. 😛

There are a couple of other very cute circuits for this sort of thing, but
modesty and greed prevent me from disclosure at this time.

😎
Click to expand...
The patent 5055797 was realized in an old TAA project (William T. Chater) - go to post 40 under
Only N-Channel MOSFETs (NMOS); better Audio from non complements by Audio Power?
Are there also commercial available amplifiers, where this approach was realized (both for home audio and car hifi components) ?
 
#87
TIP142/147

Jeff we have hundreds of thousands of parts in stock.

Many TIP142/147s, thousands of TIP35C/36C.

MOSFETs of all types, TO220 and TO247 packages.

When repairing older Soundstream amplifiers, I always replace the TIP142/147 with TIP35C/36C and add in the extra drivers.

Darlingtons are thermally unstable unless you use 1 ohm emitter resistors bypassed with 3A Schottky diodes.

This was the downfall of Soundstream as their output stages blew all the time as they used 0.1 or 0.22R emitter resistors with their Darlingtons.

Steve Mantz

Zed Audio

Zed Audio
 
#88
Good to know. So, no preference in manufacturer?

This is not for a SS amp repair.

However, in the early 90s, we sold hundreds of SS amps, but I never remember replacing/repairing one. In the late 80s, I worked at a different shop that sold HiFonics, and we seemed to always be pulling one for repair.

As well built as HFs were purported to be, I just chalked it up the application and clientele. We never used SS amps to drive subs for the most part, and the few times we did it was not for a boom wagon.
 
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