Phantom Power Capacitors

[thor.zmt]

I don't know where this comes from, but it seems to show a singularity at about 4.5V, where THD is minimal.

Find out what the formation voltage of the capacitor is. The centre point of the THD minimum is a fraction, roughly the same.

For a given signal level, applying a bias that places this level across the capacitor in a certain window determined by the formation voltage will minimise H2 and thus THD.

Note that there is not one optimum bias for all signal levels and frequencies, but a specific bias for any given combination of level and frequency.

Electrolytic capacitors are replete with mechanisms that cause nonlinear signal transmission. Like for other types, the higher the C/V product for a given mechanical size, the worse the problems.

I'm not sure all electrolytic caps show the same behaviour.

Polarised, yes.

Thor

 

[thor.zmt]

Here is your arrogant and dismissive attitude against any view that may not agree with yours.

All posts expressing views removed.

Let's stick to facts.

Thor

 

[rh001]

So fake sound is better?

Sounds like you're a grad of Trump University.

Actually yes, fake is better if it sounds better. Do you want to eat a "real" brussel sprout right off the plant or "faked" up with roasting and some seasoning? And in fact any brussel sprout you can buy today is the result of 11 years or more of breeding the bitterness out of it....so even if you say you would prefer to eat one picked right off the plant in the field still it is fake. All fruits and vegetables sold for some time now are fakes of the originals (thankfully) and Wagyu beef is a diabetic cow. Foi gras is a goose with fatty liver disease. Fake it 'till you make it!

 

[rh001]

i originally commented on this thread becasue it seemed like others I see....seemed like a newbie that really wanted to know a fine detail of audio electronic design but the newbie did not realize that he was likely to get too many aspergerish answers when in fact he should buy a few different makes and models of caps and listen for him(her)self. Newbies can be vulnerable to audiophile elitism and the immature thinking that the "best"is the goal, when in fact the "best" is going to vary according to market segment and other concerns. To make the point,a bit obliquely to be sure, I'm going to post this vid of an anime song vocal recording using a stupidiy expensive 'ultimate" sort of mic...and for sure that mic is overkill. I've seen vids of this studio before...they have an SSL console, probably from the early 90s. This is a recording for what was a hit anime movie. All the creators (songwriter, producer, band (Radwimps) are high net worth Japanese and probably drive Lexus cars, wear limited edition Citizen watches, send their kids to private schools and have Filipino housekeepers 5 days a week. That mic just fits their overall lifelstyle. By some chance it might also have just the right sound for that 12th grader's anime voice. A Shure SM58 might have been just as good for that anime maybe better.

 

[Matt Syson]

All electrolytics are on a downward journey from the day they were produced as they use an elecrochemical process so depending on circuit characteristics, temperature and TIME all will be a little different. Original 24 Volt Neve designs used the components of the day and the ones the accountnts let them use and certainly ALL electrolytic capacitors from that time are 'dead' now even if they still 'function' they are not what they were so the choice becomes to use new replacements which will be a little different or look at a dead museum article.
Music recorded in that era is also impossible to hear as it sounded 'then' because all the gear has degraded somewhat and speakers are now significantly different or themselves 'degraded' like our hearing. Yes we can like what we hear but 'authenticity' for it's ownsake is a myth. Lack of nicotine in the atmosphere and gear could possibly be as much a 'difference' as capacitors , particularly as nicotine changed mood and other bodily functions. (Says he wrestling with a 35 year old mixing desk that is so dirty internally that signals come and go 'at will' which is driving me and the desk owner 'bonkers'). There is far more going on than can be covered by choice of capacitor.
How can you determine the quality of sound if it is buried under RF interference many times the nominal signal level? It used to be hum and powerline noises but switchmode supplies are radiating everywhere these days. oLD gear that had decent RF protection tends to fare better and having preamps that are happy up to 200Khz or so are doing you no favours.

 

[Cqwet Dbdfte]

Note that there is not one optimum bias for all signal levels and frequencies, but a specific bias for any given combination of level and frequency.

Would you have a reference for that?

I would think nobody picks an electrolytic signal cap other than for size or economic reasons. In 30 years those caps have low chance of original performance or even survival. Bypassing said cap with a PP cap is also an option.
DC servo would be another option if a bipolar power supply is used.

 

[abbey road d enfer]

Find out what the formation voltage of the capacitor is.

Once again, you misunderstood.
First, this message was not addressed to you, but you couldn't resist the opportunity to rub my nose.
Second, when I wrote "I don't know where this comes from", it was in reference to the document, not the non-linear behaviour.

 

[abbey road d enfer]

A Shure SM58 might have been just as good for that anime maybe better.

Using this mic is a way of making sure that if the take is not good, the singer cannot blame it on the mic.

 

[thor.zmt]

Would you have a reference for that?

No, it is obvious, based on the operating principle of electrochemical capacitors.

It happens only at very high signal levels across the Capacitors, more than realistic. You need to be just exceeding the reverse voltage on one side, causing rectification effects to show up and at a specific fraction of the formation voltage.

If so, the two separate H2 dominant distortion mechanisms cause cancellation, that is an H2 and THD minimum.

As said, it is not something to be used in practical circuits to lower polar capacitors HD in audio circuits.

If DC coupling (and servo) idls not practical, if foil & film construction capacitors are not practical, if metalised film capacitors are not practical, the best choice are bipolar electrochemical capacitors, preferred two in series for line level DC bias or not.

Finally, if polar electrochemical capacitors must be used, use two in anti-series or anti-parallel and consider the biasing situation in the presence of large DC voltages to be blocked.

The circuit probably will have to be tested in the real world using an AP2 and priority should give to avoiding or minimising audible fidelity impairments, as opposed to signal fidelity (e.g. for HD do not use THD [signal fidelity] but psychoacoustic weighting of harmonics [audible fidelity].

I would think nobody picks an electrolytic signal cap other than for size or economic reasons.

Funny, this thread is full of posts asserting that these capacitors are the best ever, nothing is better and that there is never a need to use something better and somehow DC magically makes them better, instead of worse. Aging is never mentioned, so clearly it's "perfect sound forever (TM)".

Nobody said:

"I would have figured out a DC coupled scheme, or used film capacitors, but the beastly accountants didn't let me! It's all the accountants fault!"

It is, btw the accountants fault. I'm part qualified accountant, Assistant Director Financial Control in series Enterprises and CFO in a startup that now makes middle double digit turnover after a decade were my highest positions in that line of work. Sh!t work, excellent pay, better than most Merc's make (don't ask how I know).

So, if not blaming "the accountants", it is obvious that the global believe is that there is nothing better.

Bypassing said cap with a PP cap is also an option.

That is mainly another old wives tale.

I say mainly, because there are narrow cases where bypassing with a smaller value capacitor of different quality improves the situation, but usually the result is that the much larger capacitor dominates in the audio range and multiple resonant LC tanks at higher frequencies.

Again, I am absolutely guilty of having fallen for this old wives tale myself, for years if not decades. I eventually got to a point where I could do a lot of tests, with really horrorshow gear and large scale listening tests and rejected this as "BS".

Proof, imagine a (typical) 47uF polar elcap with 1R ESR. And an 0.1uF PP bypass. The frequency where the bypass capacitor carries ~ 30% of any signal current is ~ 1.6MHz. that's higher than my Heavy Metal Loving Cats can hear while playing 192k masters of Rush.



It also holds for RF bypassing, 3 x 1uF 0402 SMD is preferred to 1uF, 0.1uF and 0.01uF (classic old wives tale bypassing).

Even 3 x 1uF 0603 is preferred to 1uf 0603, 0.01uF 0402 and 0.01uF 0201. That surprised me, incidentally, I didn't expect that.

DC servo would be another option if a bipolar power supply is used.

This is kind of what I suggested, but to handle 48V phantom power with DC coupling the positive rail should be > 48V and the common mode range for the circuit's input must include 0V to + 48V.

But yes, in 2024 it is the the solution that falls under BFBFOTO.

In a post I nixed as it made the natives restless, I suggested that taking the folded cascode "enhanced Cohen" circuit from the THAT presentation on microphone preamplifiers could be used.

It would need to be flipped in polarity for a PNP input pair but would be trivial to be made to include -0.5V to 48.5V common mode range as long as we have at least 50V DC available or allow +46V phantom power (it is within IEC spec).

But there is no problem anyway and talking about polar electrolytic capacitors being a "potential trouble source" and in need of is very obviously a Red Cloth to many.

So PLEASE use the cheapest, physically smallest and cheapest Scheena made garbage 22uF...47uF polar caps in phantom powered microphone input coupling.

Follow the advise of all these big famous people who build the best consoles in the world and know everything and have nothing left to learn

I have nothing to add.

Back to "constuctrive threads" (pun intended) about making tube microphones, Tube and J-Fet preamplifier intentionally designed as "electronic crayons".

Over and out.

Thor

 

[MicUlli]

So PLEASE use the cheapest, physically smallest and cheapest Scheena made garbage 22uF...47uF polar caps in phantom powered microphone input coupling.

Yes I will
Probably you haven't read my post #28, THD < 0,002% regardless of using 22u or wire in the signal path. I am sure the difference is inaudible. If aging is a problem then more by using polar caps in power supplies at high temperature..
And of course i use Panasonic FC, NHG or HD. By the way: I measured leakage current at 48V and room temp. (waiting 10min) smaller than 120nA. Satisfactory.
BR, i am out too,
MicUlli

 

[thor.zmt]

Yes I will
Probably you haven't read my post #28

I did. And?

Thor(sten)

PS, Ulli, wir koennen Deutsch und kennen uns in der realen szene vor Y2K gut aus.

Danke

 

[user 133392]

thor I probably agree with you more than I disagree.

It's not what you say it's how you say it.
You come off as being incredibly toxic and many of us simply don't want to be in the room with you.
This is not The Brewery.

 

[Newmarket]

I was actually in the console business back then. SSL was successful "despite" their sound. The convenience of their full automation was compelling to users back then.

From the UK there was definitely a view that their earlier consoles - 4000 ? - weren't sonically great. But yes - Total Recall aspect had huge appeal even if the manual resetting of pots seems very tedious now in the time of DAW on a PC and plug ins. Whilst acknowledging that SSL "got there" in the end.
Hence the popularity of tracking with a Neve / Raindirk / Trident etc. then mixing on an SSL. Apart from circuit details - minimising VCA involvement.

 

[Mr. Moscode]

Telling someone they're wrong is not a ad hominem.

Depends on how it's done.

Does your idea of being civil consists in agreeing with someone who's evidently wrong?

Absolutely not.

We may have a different notion of civility...

Clearly.

 

[Mr. Moscode]

thor I probably agree with you more than I disagree.

It's not what you say it's how you say it.
You come off as being incredibly toxic and many of us simply don't want to be in the room with you.
This is not The Brewery.

I don't see Thor that way. If he's had the success he claims as a designer he must know something. I see his posts as opinions, not gospel and he doesn't, to my ears, present personal attacks. Besides, he smiles when he drinks beer.

 

[Mr. Moscode]

Actually yes, fake is better if it sounds better. Do you want to eat a "real" brussel sprout right off the plant or "faked" up with roasting and some seasoning? And in fact any brussel sprout you can buy today is the result of 11 years or more of breeding the bitterness out of it....so even if you say you would prefer to eat one picked right off the plant in the field still it is fake.

Well, that's a different domain. I don't like brussel sprouts and foi gras.
I've never listened to a brussel sprouts. Do I need 5.1 sprouts for surround flavor? It's as different as audio and brussel sprouts. Thanks for trying.

All fruits and vegetables sold for some time now are fakes of the originals (thankfully) and Wagyu beef is a diabetic cow. Foi gras is a goose with fatty liver disease. Fake it 'till you make it!

That's why I became a professional jazz bassist. I grow my own music.

 

[kags]

From the UK there was definitely a view that their earlier consoles - 4000 ? - weren't sonically great. But yes - Total Recall aspect had huge appeal even if the manual resetting of pots seems very tedious now in the time of DAW on a PC and plug ins. Whilst acknowledging that SSL "got there" in the end.
Hence the popularity of tracking with a Neve / Raindirk / Trident etc. then mixing on an SSL. Apart from circuit details - minimising VCA involvement.

SSL recall, automation, signal processing, and routing options began taking over in the early 1980s. Amazing features, for sure! Plugins and DAW automation didn’t begin to compete in a professional way until the late 90s. I grew up with the Neve/API tracking and SSL mixing, though I always wrestled with the sonics of SSLs until the J.

Eventually, in the mid 90s, Ultimation provided the option to avoid some of the VCA coloration for those who preferred that route.

Today, we get bookings on our G+, though the automation computer hasn’t been turned on in almost a decade. They want the famous SSL sound, but still cut vocals with 1073—TubeTech—interface and only monitor through the board. Bands use our outboard Neve 88R and 1073/1081/1084 and API pres. only occasionally do people use the board for processing tracks or stems. I have given up on that years ago.

 

[Mr. Moscode]

Would you have a reference for that?

I would think nobody picks an electrolytic signal cap other than for size or economic reasons.

You wrong there. Sound is everything AFAIC. Either get one that doesn't make you wince or design it out of circuit.

In 30 years those caps have low chance of original performance or even survival. Bypassing said cap with a PP cap is also an option.
DC servo would be another option if a bipolar power supply is used.

Sounds good to me.

 

[JohnRoberts]

Depends on how it's done.

Ad hominem is attacking an individual to discredit arguments, instead of attacking the arguments. Abbey is not guilty of ad hominem.

Absolutely not.

Clearly.

Abbey is one of the moderators here tasked with maintaining civility. As far as I can tell he is one of the nice ones.

JR

PS: I may regret responding to this but such is life. It probably needs to be locked.