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Old 14th August 2003, 03:48 PM   #1
hacknet is offline hacknet  Singapore
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Default Silver Mica de-coupling caps

i`m build a gain clone.

to be specific, i`m building the inverting GC design originally done by Thorsten.

IGC


i`m going to build a dual mono design with 2 nuvotem-talema toroidals. they are 225va. since i`m running a 5R load. i intend to run it off 18-0-18vac. i don`t need lotsa raw power since i`m running 96dB/w drivers.

the main power supply caps would be Elna`s that were made for Onkyo Systems. they are labeled Onkyo Integra. its 10,000uf @ 50v. i intend to bypass with 100uF Elna Silmics.

do i need to dump in two more 0.1uF caps alongside the power rails?

if so,

i intend to use Silver Mica. is this a good choice?

Thank You in advance

REGARDS
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Old 14th August 2003, 05:15 PM   #2
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Don't waste 0.1 silver micas in a PSU, send them to me instead.
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Old 14th August 2003, 08:54 PM   #3
Previously: Kuei Yang Wang
 
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Default Re: Silver Mica de-coupling caps

Konnichiwa,

Quote:
Originally posted by hacknet

to be specific, i`m building the inverting GC design originally done by Thorsten.

IGC
Ahhm, please note later redactions. After much tooing and frooing I now suggest the following:

Feedback Resistor 330k in all version.

Input resistor 10k & 100k Linear Law Pot for "Integrated Amp".

Preferred Pot types are Cermet from Vishay/Sfernice or ANY Carbon track ones, but preferably old hotmolded AB, Copal etc. - choose to taste, Cermet "precise" and "clean" and "neutral" while Carbon "musical" and "warm" and "romantic" (read a little fuzzy in a nice way).

Input resistor 15k, 18k from input to ground (across the RCA).

Either versions will normally be stable under all (most) conditions (integrated Amp not with open input and volume near max!!!!) of normal use. Also, it should not be subject to the audible problems remarked upon with the "brutal force stability" 22k resistor from the inverting input to ground.

The Resistor in the output and the RC on the non-inverting input are "optional" and where originally added to make the circuit more tolerant of "out of spec" IC's and (highly) capacitive Speaker Cables.

Quote:
Originally posted by hacknet

the main power supply caps would be Elna`s that were made for Onkyo Systems. they are labeled Onkyo Integra. its 10,000uf @ 50v. i intend to bypass with 100uF Elna Silmics.
Too much capacitance or not enough VA in the transformer!!!!

Leave the 10,000uF Cap's out in the initial wireup.

You can add them later (IF you must) with added leads paralleled to 1,000uF Silmics. For bypassing it is ABSOLUTELY ESSENTIAL to place the physically and electrically smallest capacitor in the shortest current loop anyway. Whenever I see a HUGE pysical side cap bridged with smaller caps having very long leads in positions other than coupling capacitors (high impedance circuits) I despair!!!!

Quote:
Originally posted by hacknet

do i need to dump in two more 0.1uF caps alongside the power rails?
One connecting +V & -V is not a bad idea.

Quote:
Originally posted by hacknet

if so, i intend to use Silver Mica. is this a good choice?
Excellent choice, if a little wasted. BTW, WHERE ON EARTH do you find affordable 0.1uF Silver Mica's?

Sayonara
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Old 15th August 2003, 04:30 AM   #4
JoeBob is offline JoeBob  Canada
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I'm with Thorsten, 100nF Silver Micas cost quite a penny and if you know of a source for them, do tell us.
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Old 15th August 2003, 06:13 AM   #5
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Quote:
Originally posted by JoeBob
I'm with Thorsten, 100nF Silver Micas cost quite a penny and if you know of a source for them, do tell us.
Cornell-Dubilier makes a 91nF 100V and a 68nF 300 V silver mica. No idea as to price. Mouser sells their 10nF silver mica for $9.16 so it's likely to be more than many would be willing to pay.

se
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Old 15th August 2003, 09:17 AM   #6
hacknet is offline hacknet  Singapore
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the 10% 0.1uf @ 100vdc is going for SGD$0.51 per piece.

the xchange rate from SGD to USD is 1.74...

it isn`t to bad wad... couple of cents
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Old 15th August 2003, 09:41 AM   #7
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Default Re: Re: Silver Mica de-coupling caps

Quote:
Originally posted by Kuei Yang Wang
Konnichiwa,



Ahhm, please note later redactions. After much tooing and frooing I now suggest the following:

Feedback Resistor 330k in all version.

Input resistor 10k & 100k Linear Law Pot for "Integrated Amp".

Preferred Pot types are Cermet from Vishay/Sfernice or ANY Carbon track ones, but preferably old hotmolded AB, Copal etc. - choose to taste, Cermet "precise" and "clean" and "neutral" while Carbon "musical" and "warm" and "romantic" (read a little fuzzy in a nice way).

I have been very pleased with the modern Xicon log tapers from Mouser. By using a 250K stereo and connecting the two tracks together the result is a 125K mono pots that is quieter and much better tracking than stock. I think in quantities of 10 they run 1.89 each.



Excellent choice, if a little wasted. BTW, WHERE ON EARTH do you find affordable 0.1uF Silver Mica's?

Locally, they have 100v, 100,000 pfd Silver Mica's for 2.00. With the exchange rate, that should be around 1.25 GBP. But the lead material is steel. Here in the US most of the silver mica use magnetic leads. I take a magnet with me for all parts hunts.

George

Sayonara
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Old 15th August 2003, 11:03 AM   #8
Previously: Kuei Yang Wang
 
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Konnichiwa,

Quote:
Originally posted by hacknet
the 10% 0.1uf @ 100vdc is going for SGD$0.51 per piece.

the xchange rate from SGD to USD is 1.74...

it isn`t to bad wad... couple of cents
Are you sure that these are SILVER MICA? The price, tolerance and voltage rating sounds a lot more like ceramic. And ceramic is NOT recommended.

I still recommend the Epcos (formerly Siemens) naked chip, stacked film MKT/MKC Capacitors as they offer a very "ideal" capacitor with only around 9nH Parasitic Inductance (ESL) and << 0.1 Ohm ESR in the larger values. They go up to around 4u7/63V and are physically small.

For reference, the 9nH Inductance translate to around 1 Ohm impedance @ 20MHz, which is often good enough for digital decoupling on their own, no added bypass needed.

Sayonara
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Old 15th August 2003, 03:59 PM   #9
hacknet is offline hacknet  Singapore
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its silvered mica.

is silvered mica and silver mica the same?

if it is, i think we are talking about the same thing....

i found even cheaper ones. its 50vdc... its going for $0.28

the dielectric is X7 R. there is a word Kemet labed nearby, i remeber kemet having something to do with ceramic....
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Old 15th August 2003, 04:41 PM   #10
moamps is offline moamps  Croatia
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Quote:
Originally posted by hacknet
the dielectric is X7 R. there is a word Kemet labed nearby, i remeber kemet having something to do with ceramic....
Hi,

X7 R is ceramic, EIA code -55 to 125degC, 15% tolerance.

regards
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