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Old 20th March 2012, 08:44 PM   #1
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Default Old transistor amp design - opinions please!

Hello all,

I have found an old amp design in a book published in 1974* and was wondering if anyone had any ideas or opinions what this would sound like if I made it. I am not sure I would be able to make it though, as I tried to find some of the transistors online and they seem to be obsolete.

Any input welcomed!

Thanks in advance,

David.

* "Set Up Your Own Hi-Fi: A Beginner's Guide" by R.H. Warring; Lutterworth Press, Guilford and London;1974. ISBN 0718819845.
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Old 20th March 2012, 08:51 PM   #2
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Be aware that it is a dodgy sliding-bias job.

Shun it as you would shun a rabid dog.
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Old 20th March 2012, 08:51 PM   #3
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Hi,
Search this forum.There is a thread about this amp,and how to modify it.
Regards
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Old 20th March 2012, 08:54 PM   #4
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Be aware that it is a dodgy sliding-bias job.

Shun it as you would shun a rabid dog.
Ha! OK, well maybe I will shun it. What is the draw-back of the sliding-bias bit? What do you think this amp would sound like?
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Old 20th March 2012, 08:55 PM   #5
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Hi,
Search this forum.There is a thread about this amp,and how to modify it.
Regards
OK, thanks, I will. Does it have a 'proper' name, or is it just a Mallard circuit?
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Old 21st March 2012, 03:38 AM   #6
gannaji is offline gannaji  India
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Mullard SS power amplifier
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Old 21st March 2012, 10:04 AM   #7
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often people dig out circuits like that and treat them as a hidden or forgotten treasure ...sorry to say they are not ... bias problems slow not enough power stability issues

even if made properly don't expect a "nice nostalgic" sound to come out of it .... do your shelf a favor and built a P3A will kick the hell out of the geriatric amplifier from every aspect

kind regards
sakis
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Old 21st March 2012, 03:17 PM   #8
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Thanks for that.
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Old 21st March 2012, 03:18 PM   #9
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often people dig out circuits like that and treat them as a hidden or forgotten treasure ...sorry to say they are not ... bias problems slow not enough power stability issues

even if made properly don't expect a "nice nostalgic" sound to come out of it .... do your shelf a favor and built a P3A will kick the hell out of the geriatric amplifier from every aspect

kind regards
sakis

Ha, well I can imagine there are plenty of people who will think like that! I had / have no pre-conceptions about the circuit though, hence my original question. I shall have a search for this P3A - thanks for the advice!
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Old 21st March 2012, 09:49 PM   #10
AKSA is offline AKSA  Australia
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This circuit has one startling feature; the way in which the reverse phase drive to the quasi is set up. It differs fundamentally from the JLH in this area, and that makes it interesting, as the approach used - a common base drive off the VAS - is novel.

However, it has a downside in that it then becomes bound up with setting the quiescent, and some wag has given it a sliding bias arrangement which actually works the wrong way. If the sliding bias mechanism were removed somehow, it might actually sound very, very good.

Hugh
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