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Old 3rd October 2006, 09:38 AM   #1
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Default Simple regulator upgrade

I'm in process of upgrading a preamp PS of an old integrated amplifier (attached)
Searching several service manual on hand, I noted this scheme has many variations, and mostly of the caps values.

I found several variations as follows:
1. C1=4700/bypass 0,47, C2=100/50, after the emmiter 470/50/bypass 10000pF
2. C1= 4700/bypass 0,47, C2= 220/50, after the emiter 220/50, bypass 10000pF
3. C1=1000/no bypass, C2=100/50, after emitera 470/50, and
4. C1= 1000, C2=100/50, after emiter 1000/50

I'm lost...
All the caps exept the C1 are of very standard quality (Elna standrad), and I tried to upgrade with Pana FC, with on-hand values (680 and 470uF/50), and that sound horrible
I changed back the old ones after one week.

Can anybody explain how to clean and "to fasten" the sound, and what's the catch with those simple regulators?
Can be here applied the "rules" of small caps of highest quality at the end (after the emiter) as is the case with chip-regulators?
Why the C2 is very variable, and what's the pourpose of that cap?

I'm really not expert in electronic, but I can modify up to the some level myself.
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Old 3rd October 2006, 09:44 AM   #2
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That's what Lady Eva often talks about. Better electrolytic caps have lower ESR and shouldn't be bypassed, because high quality resonans may happen. General purpose industry standard electrolytic caps should be bypassed without problem. Ask Eva if you want to know more.
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Old 3rd October 2006, 10:08 AM   #3
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I appreciate your comment, but...
It is true that good quality caps frequently does not need bypass, still, all -even the best big electrolytics on the main power supply- will benefit from bypass.
On the other hand, why are the values of the putput and zener caps in this scheme so variable? What the pourpose of that?
If we need just to bypass the zener diode and to lower/eliminate the zenner's nose, than 100 or 220uF are not good for that reason - it is better to stick som poly- capas, or even ceramic. So, I guess something more is lying here...
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Old 3rd October 2006, 10:18 AM   #4
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No, bypass cap can create ESL with capacitance resonance and worsen things. Some ESR from cheap cap is sometimes helpful.
You could also use a snubber.
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