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Old 14th December 2004, 12:37 AM   #11
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Quote:
Originally posted by moving_electron
Are you saying to take off the 47uF and just use the 100nf caps?
No!
I was telling you to try because it will sound very bad!
The word was C R A P, but it was censured.

Quote:
Originally posted by moving_electron
My experience with the OPA2604 was that things got better as I added capacitance on the power pins although at that point I only had 10uF on them.

The OPA2132 sounded better to me than the OPA2604 when I tried them at 47uF. I made a number of changes to the system as I went from 10uF to 47uF.
The OPA2132 is better than the OPA2604, and as I said lots of times here, I recommend between 22 and 100uf capacitance on each supply pin to ground.
You can also bypass the electrolythics with small 100nf multi-layer ceramics, but this is not so critical. Note: the LM6171/2 needs them.
Also a 100~330nf poly cap directly from V+ to V- PSU pins on the op-amp. Usually you can do that under the circuit.
This gives me very good results everywhere, not only with the OPA2132.
For me, it's a rule.
After so many tests I made years ago, this is what works best.
Always.

Also, if you don't do it this way, forget the OPA627, it will NOT sound good.
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Old 14th December 2004, 01:10 AM   #12
digi01 is offline digi01  China
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another way is BP caps,a couple of small bp caps will do.
I use 2X6.8uf BP caps(Solen,WIMA-MKP10 film caps)at the regulator power supply part and 0.1uf close to each chips.

the sound of opa2604 is sweet,but I like 2134 more.
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Old 14th December 2004, 03:08 AM   #13
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Quote:
Originally posted by carlosfm


No!
I was telling you to try because it will sound very bad!

Ah, makes sense now. I would have been shocked if it sounded better without the 47uF caps. I have two nearly identical phono preamps, one without much capacitance on the power supply pins and one with. I definitely liked the one with the capacitance more. Same for my preamp.

Quote:
Originally posted by carlosfm


The OPA2132 is better than the OPA2604, and as I said lots of times here, I recommend between 22 and 100uf capacitance on each supply pin to ground.
You can also bypass the electrolythics with small 100nf multi-layer ceramics, but this is not so critical. Note: the LM6171/2 needs them.
Also a 100~330nf poly cap directly from V+ to V- PSU pins on the op-amp. Usually you can do that under the circuit.
This gives me very good results everywhere, not only with the OPA2132.
For me, it's a rule.
After so many tests I made years ago, this is what works best.
Always.

I am a pretty enthusiastic believer in this and have been using it since your original comments way back when with good results.

Quote:
Originally posted by carlosfm


Also, if you don't do it this way, forget the OPA627, it will NOT sound good.
One of these days I will be listening to the OPA627 in the Regulated BIGC. Slow but steady progress...
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Old 19th December 2004, 05:34 PM   #14
KBK is offline KBK  Canada
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OK, carlos...why do you wnat to modulate the the PS rails against each other? I'm confused about the logic of the small poly cap between the two power rails, right at the op-amp. After all, these ARE global fedback devices, and the speed of that feedback IS Finite....

Maybe to control PS micro-modulation under an AC audio signal load? (feedback micro-timing delay issues?) Please supply an explaination, if you so desire. I'm very curious.
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Old 20th February 2005, 11:25 PM   #15
Stabist is offline Stabist  Slovenia
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Quote:
Originally posted by carlosfm

The OPA2132 is better than the OPA2604, and as I said lots of times here, I recommend between 22 and 100uf capacitance on each supply pin to ground.
You can also bypass the electrolythics with small 100nf multi-layer ceramics, but this is not so critical. Note: the LM6171/2 needs them.
Also a 100~330nf poly cap directly from V+ to V- PSU pins on the op-amp. Usually you can do that under the circuit.
This gives me very good results everywhere, not only with the OPA2132.
For me, it's a rule.
After so many tests I made years ago, this is what works best.
Always.
So if I understand correctly - (btw: I'm trying to make a pretty decent MC chipbased preamp - so I'm opened for many good ideas) - those "between 22-100uF" capacitors are soldered as close as possible to the chip +/-legs and gnd and that 100-330nF poly cap are positioned between +/- legs ...

Btw - in my test phase I'm trying the circuitry with NE5532 and OPA2604 (because I had those at home) - but which chips are recomended for low noise MC preamp? Is opa2132 good choice? Or is it better to look elsewhere - eg LT1028.

Thanks
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Old 22nd February 2005, 04:09 AM   #16
Gaucho is offline Gaucho  Canada
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Quote:
Originally posted by carlosfm
Also a 100~330nf poly cap directly from V+ to V- PSU pins on the op-amp. Usually you can do that under the circuit.


I'd like to mention the fact that I've achieved very good sonic results trying electrolytics (usually a 10uF with a 0.1uF film) in this position. The results very with the op-amp being used.
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Old 22nd February 2005, 07:23 AM   #17
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Quote:
Originally posted by carlosfm
The way you are "advicing" this member to use them they sound very bad.

This is also one of the major flaws of your "SMD Gainclone".
Quote:
Originally posted by carlosfm
Oh, and please use the AD8620, a much inferior op-amp than the OPA2132, but sounds better the incorrect way you use it in audio applications, of course.

Quote:
Originally posted by moving_electron
IOPA2132 sounds rather good to me
Carlos, don't forget that your opinion is not facts and certainly not in others ears, so if you change your statements to more like "I think", or "my opinion is.." I think we will have a better discussion climate. Besides even though my Gainclone has design flaws you have never heard it I'll suppose. We know one who was very unsatisfied. We have also heard that everyone else are _very_ satisfied. So what does this mean?

This means maybe that there are some exaggerations. "Really bad" isn't maybe so bad. If you say "sounds really bad", how bad is that?
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Old 22nd February 2005, 07:54 AM   #18
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Bypassing depend on concrete connection, design of PCB, type of opamps and several other conditions, but Carlos maybe like " end solutions" as " Holy Inkvisitor " - " No doubt, no problems " .
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Old 22nd February 2005, 01:06 PM   #19
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Quote:
Originally posted by peranders
Carlos, don't forget that your opinion is not facts and certainly not in others ears, so if you change your statements to more like "I think", or "my opinion is.."
Take it always as my oppinion, try it and listen.
If I say "I think it sounds better" is because I'm not sure.
As I'm sure it sounds better, I say so.
The negative "climate" may be generated by others, not me, as I'm just reporting my experiences.
Everyone is free to take it or leave it, try it or not, but please discuss with reasons.
Curiously, those who discuss are always those who don't bother to try what I'm suggesting...
Sometimes I ask myself why do I bother to post on audio forums...
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Old 22nd February 2005, 02:37 PM   #20
NealG is offline NealG  United Kingdom
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Because we like you Carlos!

I have tried the 100nF between + and – supplies in a DAC with the OPA2134 and can’t say I liked it. It pushed the midband forward highlighting detail at the expense of the treble which lost air and ambience.

Also regarding recommendations for opamps in phono preamps I always understood it was better to use a bipolar design as they generally have a much lower voltage noise than FET. I understood FET’s are better suited to MM due to a lower current noise.
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