Converting soundstream D100ll into Class A50?

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#2
The Class A50 is NOT a class A amplifier. It uses TIP142/147 output transistors with 1 ohm emitter resistors bypassed with diodes.

A class A amplifier is defined that the idle current be equal or greater than the maximum load current and NO car amplifier can do this - period!

The D100 series uses TIP142/147 with 0.1 ohm emitter resistors and owing to the use of these terrible darlington output devices whose thermal characteristics are so poor one must be carefull to set the idle current so that the crossover notch at 20KHz 1 watt into 4 ohm loads just just dissapears. Anything more and the trannies blow.

We repair lots of these poorly designed amplifiers and when we have output stages with 0.1 ohm emitter resistors we change them to the 1 ohm//diode deal to improve reliability.

Steve Mantz
Zed Audio Corporation
 
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#3
After doing the 1ohm/diode deal, what would be the ideal setting for the bias? 10ma per device, or say you mentioned 20khz 1watt into 4ohm load just so the crossover notch barely disappears. I ask because I did this to my 405S (the front and rear channels) and set the bias at 11ma per device and had no issues with thermal runaway or current draw drift.
 
#4
For car amplifiers I always set bias at 1 watt 4 ohm at 20KHz unless it is one of the Chinese/Korean designs where the bias transistor is somewhere in the middle of the PCB so no thermal tracking is available. I set these so some notch is visible as the consumer who buys this junk is not interested in SQ.
 
#8
Pjager said:
Aloha, someone had schematic to convert Soundstream D100ll into Soundstream Class A50? If Zener_Diode is still around if i can get him to give me a copy or anyone else has one? Thanks
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Maybe wadest can help you.
But D100II maybe can to convert into Class A50II.
Class A50 is the first series.
If possible i suggest to buy Class A50II, and keep original the D100II.
My 2 cent.
 
#9
Wade Stewart passed away from what i hear. He had been helping me repair my SoundStream Reference 1000 by answering questions via PM towards the end of 2021 and out of nowhere stopped getting replies. I recently started working on the amp again and did a google search and found this:

o7

Wade Anthony Stewart​

June 29, 1950 - March 19, 2022

Wade Stewart, engineer, business owner, employer and all around generous person died earlySaturday morningMarch 19, 2022 at the Mercy San Juan hospital in Carmichael, CA with his wife Kelly Belmont-Stewart by his side.Wade battled diabetes for years and it finally took his life
Wade Anthony Stewart was born June 29, 1950 in Alhambra, CA to Wendell and Elizabeth Stewart.He was raised in Alhambra and graduated Mark Keppel High School.He was always a very bright and curious boy and you could find him tearing many things, toys etc. apart just to see how they worked.He was a genius in disguise.Wade was very interested in electronics and music and he excelled at both.He had a beautiful voice, played many instruments just by picking them up and tooting or strumthem until he figured out how to make them play great music.He repaired amplifiers and more as a young man and began designing; Rock Amps was his first really cool item.As time and experience moved on he began designing and building many things that went along with bands and music and founded Stewart Electronics and developed it into a business in the Sacramento area where he employed hundreds people over the years. He was also the VP of Engineering for Soundstream Technologies where he designed and manufactured many of their products at Stewart Electronics. Wade was told more than once “you can’t do it that way” to which he would say “sure you can”.He won awards for his innovative designs; and developed ever easier manufacturing processes as well.

Wade demonstrated his generosity and pay-it-forward many times to complete strangers, family and friends alike often with a smile and a giggle.

Wade Stewart is survived by his wife Kelly Belmont-Stewart, ahalf-brother Craig, three sisters Susan, Cindy and Diane as well as a number of nieces and nephews. To many he was just known as Ace.

There is a GoFundMe account set up to assist Kelly atGoFundMe.comand donations can be made in his honor to the American Diabetes Society.

There is no service planned at this time.
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#11
Sympathy to his surviving family.
I dealt with him via email a few years ago.
He seemed really nice and more than happy to help even though he was suffering his ailments badly.
I'd also like to thank his Wife for helping him by posting out orders etc.
 
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