Hi,
I put this post in the chip amp forum because Carlos and some others mentioned using this OpAmp.
Please ignore any wrong grammar and spelling, this is my second language.
I have a very limited understanding of electronics, so forgive me if my questions seem to be silly.
I want to upgade my Marchand XM1 active crossover with the OPA2132.
As Carlos mentioned a wile back this is one of his favorite OpAms if it is bypassed with 47-100uf cap and a smal ceramic cap.
As I understant, this bypass is to be done on the negative and the positive rails of the OpAmp.
Each crossover bord uses three OpAms: one for the buffer and two for filtering. This makes all together 12 OpAmps for a three way stereo unit.
Since all the OpAmps are fed by one psu, do I need to use a cap after the psu with 12 times the requierd capacitence for one chip, or is it better to still have 12 induvidual caps close to the chips. The other question would be, if I already used plenty of capacitence for filtering at the psu, does that spoil the induvitual bypassing.
I appreciate any help,
Klaus
I put this post in the chip amp forum because Carlos and some others mentioned using this OpAmp.
Please ignore any wrong grammar and spelling, this is my second language.
I have a very limited understanding of electronics, so forgive me if my questions seem to be silly.
I want to upgade my Marchand XM1 active crossover with the OPA2132.
As Carlos mentioned a wile back this is one of his favorite OpAms if it is bypassed with 47-100uf cap and a smal ceramic cap.
As I understant, this bypass is to be done on the negative and the positive rails of the OpAmp.
Each crossover bord uses three OpAms: one for the buffer and two for filtering. This makes all together 12 OpAmps for a three way stereo unit.
Since all the OpAmps are fed by one psu, do I need to use a cap after the psu with 12 times the requierd capacitence for one chip, or is it better to still have 12 induvidual caps close to the chips. The other question would be, if I already used plenty of capacitence for filtering at the psu, does that spoil the induvitual bypassing.
I appreciate any help,
Klaus
No worries about your english. It's good!
Good engineering pratice is to have 100 nF/63 V polyester or ceramic close to each supply pin of the opamps and down to ground. You can also have for instance 10 nF + 10 uF electrolytic capacitors but this OPA2132 or OPA2134 aren't so sensitive. It becomes more sensitive the faster the opamp gets.
Your last question: Strive alsways to have decouplings caps as close as possible to the "current consumer".
Doesn't your filter already have sufficient decoupling?
Good engineering pratice is to have 100 nF/63 V polyester or ceramic close to each supply pin of the opamps and down to ground. You can also have for instance 10 nF + 10 uF electrolytic capacitors but this OPA2132 or OPA2134 aren't so sensitive. It becomes more sensitive the faster the opamp gets.
Your last question: Strive alsways to have decouplings caps as close as possible to the "current consumer".
Doesn't your filter already have sufficient decoupling?
peranders said:
Who told you so?
Just by looking at the datasheet?
Since I've registered here that I've been insisting on how these op-amps must be used.
The way you are "advicing" this member to use them they sound very bad.
Thanks for that.
This is also one of the major flaws of your "SMD Gainclone".
The way you use op-amps I should advice that the best results you can have is with the NE5532, they are very happy this way and when used this way they sound much better than modern and much superior op-amps.
Keep up the good work.
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.
Carlosfm,
Your post could have been more constructive. Instead of just telling others that you think they are doing something wrong, you could tell them how you think they are doing it wrong. That is, tell them what you think is the right way. You could have saved yourself a lot of typing by just saying, "In my experience, the OPA2132 sounds better to me when I used 100 uF bypass caps instead of much smaller ones.". That would be a constructive addition to the thread.
I'm trying some different op amps but keeping the same bypass caps before changing the cap values again.
OPA2132 sounds rather good to me and is the current winner with 47uF bypass caps per power pin. Has 22uf between rails though at a single point on the board and 22uF from each power rail to ground where power comes on board. Each has a 100nF ceramic as well. 100nf ceramic between each op-amp supply pin.
I may leave this bypassing alone for a while though as I am quite happy with it for now. Sounds good in the preamp and the phono preamp. Crisp, clean but not harsh or "clinical".
Other opamps to try though.
OPA2132 sounds rather good to me and is the current winner with 47uF bypass caps per power pin. Has 22uf between rails though at a single point on the board and 22uF from each power rail to ground where power comes on board. Each has a 100nF ceramic as well. 100nf ceramic between each op-amp supply pin.
I may leave this bypassing alone for a while though as I am quite happy with it for now. Sounds good in the preamp and the phono preamp. Crisp, clean but not harsh or "clinical".
Other opamps to try though.
What to do now?
Hello Carlos,
Please tell me how you would go about in my case.
Since I have 12 OpAmps on one power supply do I still need to put 47uf close to each pin of the OpAmps or can I use 12X 47uf at the PSU and just 100nf close to the chips?
I actually don't have the 2132 but the 2134.
Cheers,
Klaus
Hello Carlos,
Please tell me how you would go about in my case.
Since I have 12 OpAmps on one power supply do I still need to put 47uf close to each pin of the OpAmps or can I use 12X 47uf at the PSU and just 100nf close to the chips?
I actually don't have the 2132 but the 2134.
Cheers,
Klaus
carlosfm said:
Take those 47uf caps and put just 100nf caps.
You will be shocked.
You will say: **** op-amp!
Are you saying to take off the 47uF and just use the 100nf caps?
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.
Looking forward to being shocked! Mentally, not physically.
moving_electron said:
No!
I was telling you to try because it will sound very bad!
The word was C R A P, but it was censured.
moving_electron said:
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.
carlosfm said:
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.
carlosfm said:
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.
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.
carlosfm said:
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...
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.
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.
carlosfm said:
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.
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
carlosfm said:
carlosfm said:
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?moving_electron said:
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?
peranders said:
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...
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.
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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