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Old 18th September 2001, 09:57 PM   #1
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It is usefull to put a caps in parralel with Zener Z103 ?
if yes do you know a good value of it ( ?F) ?

And with each diodes of the power bridge (Greatz) ?
Can you give me some reference for diodes and caps in order to make a good bridge ?
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Old 19th September 2001, 07:12 PM   #2
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Quote:
Originally posted by Miles Teg
It is usefull to put a caps in parralel with Zener Z103 ?
if yes do you know a good value of it ( ?F) ?
The service manual says that Z103, along with R105/6/7 and Q103 are used as a constant current source. I think that a capacitor in parallel with Z103 will do little to improve the circuit, and may degrade it. On the other hand, a capacitor in parallel with R105 should help to remove some zener induced noise from the current source. Since the current in this section of the circuit is quite small, I'd use a capacitor in the range of 1-10uF. Also, I'd use a polypropylene film capacitor.

Good luck.
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Old 19th September 2001, 09:54 PM   #3
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Thanks alot. really
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Old 20th September 2001, 09:39 AM   #4
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In my Aleph amp I by-passed the zener diode with a small plastic capacitor, it seems to work well, reducing noise: this value should not to be too big, in order to avoid any transient during the power-on.
As Thoth said, few uF are a perfect choice, in my opinion.
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Old 20th September 2001, 10:57 AM   #5
Koy is offline Koy  Czech Republic
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I did the same. Only the value is different to the previous one - i bought more electrolyts - 200M.
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Old 20th September 2001, 02:55 PM   #6
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What really mattes is does it improve sound or degrade it. Can you really hear a difference with or without it? Let your ears be the judge. I really doubt that it matters as it would have beem built in in the first place.
Mark Gubrandsen
Salt Lake City, UT
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Old 20th September 2001, 07:06 PM   #7
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Hello Mark,
in my experience, in other contexts, I appreciated zener bypass, both through instruments, both ears, that is more important.
In this case actually I've not yet tried without bypassing this diode, but this should not be an exception, since a noisy Vgs produces a noisy drain current.
The nfb probably deaden this, but maybe it's better to soften it previously, at a very low cost.
However, as soon as possible, I'll try to alternate the two layouts, to make me sure of this.
On this forum, many diy proposed other ways just to avoid zener noise in this position, and they had been around a lot.
Thirty bilions flies eat ****, they can't be wrong? I don't think, really.
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