Parallel connecting of big capacitors with smaller capacitors for optimising the sound??

[thor.zmt]

Yes, use only (quality) bipolar electrolytics in the signal path

That is not commercially viable. There are just not enough sources.

Measurements are clear that a bipolar beats a polar cap, usually by big margins, when it comes to distortion.

And a generic polar cap inside the feedback loop of an Op-Amp beats the non-polar cap outside the feedback loop, usually by big margins. And it can use commodity parts, available in volume.

BTW, it's usually OK for audio decoupling of common (not high speed) op amps to use normal (not low-ESR) electrolytic bypass caps at the regulator and the smaller x7r ceramics at or near the op amp.

Yes, this is usually acceptable, however I always recommend around 10nF from +V to -V for which 0402 C0G is useful.

These are these days my "standard" items in capacitors for commercial design

0402 10pF/100pF/330pF/1nF/50V C0G for EMI hardening circuits

0402 10nF/25V C0G decoupling and where needed. They often make sense on clock oscillators and similar stuff where their resonance is near oscillator frequency or in analogue circuits for RFI hardening

0402/0603/0805/1206 various values 5% C0G with multiple capacitor in parallel for EQ/Timing etc.

1210 100nF/25V C0G or Panasonic Film for low voltage, low value coupling capacitors

Nichicon Muse ES Series Bipolar Electrolytic Capacitors for coupling - where feasible (budget), otherwise polar within feedback loop

Panasonic Os-Con for special cases where low ESR, microphonics are important or we have budget to spare and go for extreme performance (they make rails a lot quieter)

0402/0603 1uF/25V X8S or X7R for decoupling up to 10's of MHz

1210 22uF/25V X8S or X7R for switching DC-DC converters as main filter/reservoir capacitors

Others as required/recommend by App-Notes. I also like to place 22uF/0.1R snubbers (~60kHz turnover) on rails if there is a lot going on, like when using Os-Con and Ceramic on the same rail, all with their sub 10mOhm ESR and varieties of ESL.

Thor

 

[Brian Roth]

Yes, use only (quality) bipolar electrolytics in the signal path, even (or especially) in places with significant DC bias present. Measurements are clear that a bipolar beats a polar cap, usually by big margins, when it comes to distortion.

What are quality brand(s)/series you recommend for bipolars?

Bri

 

[Script]

Maybe Nichicon Muse, the green ones. It's what use -- but just a habit of sort.

 

[living sounds]

That is not commercially viable. There are just not enough sources.

Well, this is a DIY forum. A German pro audio manufacturer I know had the signal path bipolars made to spec in China...

And a generic polar cap inside the feedback loop of an Op-Amp beats the non-polar cap outside the feedback loop, usually by big margins. And it can use commodity parts, available in volume.

I'm struggling to think of pro audio circuits with electrolytics in the feedback path of op amps.

 

[living sounds]

Maybe Nichicon Muse, the green ones. It's what use -- but just a habit of sort.

Yes, these are the best and readily availible. But I was told by an engineer that they stopped using them in commercial design because they dried out too fast.

 

[thor.zmt]

Well, this is a DIY forum. A German pro audio manufacturer I know had the signal path bipolars made to spec in China...

DIY, still not that easy to get. Nichicon Muse are limited in values and voltages and not cheap. But yes, for DIY they make a decent option, if you are in a country where you can find genuine ones in small QTY (or you are willing to pony up the MOQ at Mouser)..

I'm struggling to think of pro audio circuits with electrolytics in the feedback path of op amps.

Why? It's a trivial rearranging.

Essentially everywhere you see an Electrolytic cap, polar, or not, it is likely trivial to rearrange the circuit to either eliminate them or enclose them in a feedback loop.

Even in tube circuits, as long as looped feedback is employed at all, we can enclose the coupling capacitors in a feedback loop.

View attachment IMG_20240129_195715.jpg

Thor

 

[Tubetec]

So it might be beneficial to replace say an old style axial electrolytic coupling cap with two radials wired in series ,back to back ?
Its awkward to wire in radial caps in places that axials once were due to the spacings involved .

 

[thor.zmt]

So it might be beneficial to replace say an old style axial electrolytic coupling cap with two radials wired in series ,back to back ?

DEPENDS. Using a non-polar electrolytic or film is preferred.

Its awkward to wire in radial caps in places that axials once were due to the spacings involved .

Bend one wire over and extend it using isolated solid core wire, (I usually do the HV end, so +), put several layers of tape on the metal end and then fold over the wire and use clear shrink wrap tubing and you have an axial capacitor. Fit so the wire is below and doesn't show.

Thor

 

[living sounds]

Why? It's a trivial rearranging.

I was thinking of existing designs. Recapping and optimizing decoupling in my LFC alone was an extremely time consuming task.

Essentially everywhere you see an Electrolytic cap, polar, or not, it is likely trivial to rearrange the circuit to either eliminate them or enclose them in a feedback loop.

How would you go about it, say with a voltage follower?

 

[Script]

Bend one wire over and extend it using isolated solid core wire, (I usually do the HV end, so +), put several layers of tape on the metal end and then fold over the wire and use clear shrink wrap tubing and you have an axial capacitor. Fit so the wire is below and doesn't show.

I do that but without the cosmetics of tape and clear shrink wrap. Units don't get moved much around over here. And sometimes it even fits without extending a lead.

 

[thor.zmt]

I was thinking of existing designs.

Yes, if we make modifications I agree in part.

To me the first stop is to kill off all bipolar Op-Amp's and replace the with modern, low offset, low noise FET types. Basically NE5532/NE5534/TL07X/TL08X have no place in 2024.

The OPA16XX series has enough choice, with the OPA1678/1679 being the VFM sweet spot IMNSO.

With feck all input Bias current many coupling cap's can be deleted and replaced with a piece of wire. Both cheaper and better than bipolar capacitors. And zero aging issues.

How would you go about it, say with a voltage follower?

View attachment IMG_20240129_230131.jpg

Thor

 

[living sounds]

View attachment 121423

Thor

Interesting, but that's 6 parts instead of 1.

And I have to say that I like the 5532/5534 and have yet to find an op amp of which I prefer the sound to those old trusted dinosaurs.

 

[john12ax7]

And I have to say that I like the 5532/5534 and have yet to find an op amp of which I prefer the sound to those old trusted dinosaurs.

What have you compared them to? I was surprised at how much I liked the 5532/5534. Wonder if it's a familiarity thing? If you grow up listening to so many records mixed on SSLs it becomes somewhat of an ingrained preference

 

[JohnRoberts]

[veer alert ]

It is difficult to characterize op amps as having their own unique sounds. Op amps can have unique open loop transfer functions but any such open loop behaviors get reduced by loop gain margin (ratio of open loop gain to closed loop gain). Properly done very little of the open loop behavior gets expressed.

JR

 

[Ike Zimbel]

What are quality brand(s)/series you recommend for bipolars?

Bri

I have been using Panasonic SU series for 25 years and I (and my clients) have been very happy with them, both for sonics, and for longevity.

 

[john12ax7]

Are there any 105 degree bi-polars?

 

[Newmarket]

Yes, if we make modifications I agree in part.

To me the first stop is to kill off all bipolar Op-Amp's and replace the with modern, low offset, low noise FET types. Basically NE5532/NE5534/TL07X/TL08X have no place in 2024.

The OPA16XX series has enough choice, with the OPA1678/1679 being the VFM sweet spot IMNSO.

With feck all input Bias current many coupling cap's can be deleted and replaced with a piece of wire. Both cheaper and better than bipolar capacitors. And zero aging issues.



View attachment 121423

Thor

Bias/Offset issues and advantages understood. But anything OPA16xx wise matching NE55xx (or alternative Bipolar input opamps) on voltage noise ?

 

[Brian Roth]

I have been using Panasonic SU series for 25 years and I (and my clients) have been very happy with them, both for sonics, and for longevity.

I need to check the specs on those....are they 105C/multi-thousand hour life parts?

Bri

 

[thor.zmt]

Bias/Offset issues and advantages understood. But anything OPA16xx wise matching NE55xx (or alternative Bipolar input opamps) on voltage noise ?

OPA1678 which is dirt cheap is 4.5nV|/Hz, drives 600 ohm, has < 0.0001% (-120dB) THD & N into 2k, 9 V/uS slew rate, 2mV max offset and is FET input, folded cascade internal structure with rail to rail output.

Supply range is +/-2.25V to +/-18V, the main limitation compared to NE553X +/-22V not that you see +/-22V used that often.

However, if the rails are lowered to +/-18V and OPA167X are used, the loss of headroom is rather modest, as the OPA167X output swings to 0.2V from the rail into 2kOhm loads.

It's actually a resymbolised OPA1652/54, which won a blind Op-Amp shootout we did, 5532 came in the very bottom.

Hence my quip 553X no longer have a place. Not having to deal with the input bias current and having minimal offset can simplify circuits a lot.

If you need noise lower that the 4.5nV|/Hz (mic), add a discrete pair or better a Sziklai frontend with multiple parallel 2N4403 and a small signal N-MOS plus cascode (for high supply voltages) and make a 'flying' frontend to eliminate the coupling capacitors on the Mic in with phantom power.

If you need more drive, look the simple headphone amp thread for a simple buffer.

Thor

 

[Khron]

I need to check the specs on those....are they 105C/multi-thousand hour life parts?

Bri

SU are "general purpose" 85C parts, that also come in a non-polarized flavour.