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Old 13th June 2003, 09:19 AM   #1
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Default Highly application specific Resistor question

Koinichiwa,

I am just interested if anyone has done some studies which resistors sound best to their ears when used in the Feedback loop of an OPA627 used as I/V converter.

The I/V converter will be followed by a Cathode Follower operating as "Jennifer Lowpass", is anyone is interested.

Sayonara
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Old 13th June 2003, 11:13 AM   #2
HpW is offline HpW  Switzerland
diyAudio Member
 
Join Date: Mar 2002
Location: Switzerland (Bern)
Hi,

I used first with my PCM63 and OPA627 some smd's.

Then I changed to Alpha electronic's (Japan) with overall better
natural sound improvment. Also the feedback compensation
could also be lowered (overshut compensation).

May look at www.alpha-amer.com

The types I used http://www.alpha-amer.com/images/pdf/resistor-m/ema.pdf

Cheers

HpW
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Old 13th June 2003, 11:35 AM   #3
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Koinichiwa,

Quote:
Originally posted by HpW
I used first with my PCM63 and OPA627 some smd's.

Then I changed to Alpha electronic's (Japan) with overall better
natural sound improvment. Also the feedback compensation
could also be lowered (overshut compensation).

Arigato gozaimasu

Sayonara
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Old 14th June 2003, 04:22 PM   #4
MBK is offline MBK  Singapore
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Join Date: Apr 2002
Location: Singapore
Hmmm, I used an OPA2134 with a biased BSS170 follower, I/V is through garden variety metal film.

What I noticed worth mentioning:

- tried OPA627, couldn't get it stable (my poor veroboard layout I guess). OPA 2134 was less picky.

- even so I needed a small R (47R) between the transistor and the actual I(out) of the 1541 for stability

- on the AD797 data sheet they show some I/V applications. I used one of their tricks, an RF shunt cap between (+)in and (-)in, value 1000 pF. That configuration ended up working best, with more punch (dynamics) than straight I/V via feedback loop.

- gate resistor 100R

- FWIW I used a 3 pole Bessel 20 kHz post-I/V (it's NOS), 1st pole is a primary filter by a cap parallel with the I/V resistor



MBK
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