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Recommended capacitors for AF circuits

I've been lurking here for a long time, in the hopes that some of the wisdom of the learned ones here would manage to stick in the cobwebs upstairs.

Googling for an almost an hour failed to answer my question to my satisfaction. So, I'm asking here: what capacitor types do the audio gurus here recommend for simple audio circuits? I'm playing around with a circuit, but I am getting a lot of squeal I believe to from my choice of polarized electrolytic caps (220n and 470n) where polarized caps are not indicated (application circuit in the LM1036 data sheet). (Seemed like they would work, given that most have one end grounded.)

The electrolytics are the only ones I have at the moment, and before I buy a different type, I would like some recommendations on the type(s) to get.

TIA, and thanks to all for sharing their wisdom over the years.

Thomas

--

A thoughtful pause, then resumes the prince, "We must Learn from 
Yesterday, Live for Today, and look Forward to Tomorrow, for The Past be 
The Present, and No Less The Future."
Reply to
RoyalHeart
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have a look at Walt Jung's articles

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martin

Reply to
martin griffith

'Squeal' sounds like a feedback problem. 220n is 0.22 uF, you aren't using 220 uF capacitors, are you? 220n capacitors are not available as electrolytics.

Leon

Reply to
Leon

"Leon" <

** Tantalum bead caps are readily available in standard values from 0.1 uF upwards.

eg:

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These *are* classed as being electrolytic types.

......... Phil

Reply to
Phil Allison

Most of the large (47uF, 10uF) capacitors shown on the LM1036 app circuit are electrolytics, used for bypass, etc., where they have little AC voltage across them and therefore don't disturb circuit performance. This includes the output capacitor if you choose a large enough value. According to the datasheet, you may want to increase the value of the 10uF caps to reduce any low-frequency effects on the bass control, you could use three 47uF for the IC.

Some of the smaller ones shown may be electrolytic types, if you wish (and can find them). These are the 0.22uF caps, which just bypass the DC control voltages. They may also be smaller ceramic types, say 0.1 or even 0.01uF, because they're simply present to insure no signal couples into these lines from your wiring to the panel, etc. One of the beauties of the LM1036 is the way it lets you implement front-panel analog gain and tone control, without routing any actual signals to the panel.

But be careful of Ct and Cb. These are the critical capacitors used for treble and bass tone-control. They have significant AC voltages at the tone-control frequencies, so if you use types with high dielectric absorption, etc., such as ceramic caps, they can introduce serious distortion into your audio signal. Follow Martin Griffin's suggestion and read Walt Jung's classic capacitor articles,

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DigiKey has high-quality polypropylene film capacitors that should work well.

--
 Thanks,
    - Win
Reply to
Winfield Hill

"Winfield Hill"

** So " Win the Expert " has actually swallowed all that erroneous and long ago discredited audiophool rot about "capacitor sound" ???

And now he proselytises the worthless bunk to gullible fools like Thomas?

Any credibility Mr Jung once enjoyed as a technical writer was destroyed when those piles of pseudo- science appeared in print.

The real crime is that it is still being cited as if it is "fact" 26 years later.

....... Phil

Reply to
Phil Allison

The input capacitors are possibly the cuase of the problem if you have used polarised devices, as depending on the input signal these may have a reversing polarity signal acros them.

2 electrolytics in series will make a non polarised capacitor but you need twice the value, and connect like ends together. but for values less than 1uf polyester would probably be the best choice to start with.

Also electrolytics have a leakage current wich could cuase a problem in the other parts of the circuit.

Colin =^.^=

Reply to
colin

Thanks. Will do.

Thomas

--

A thoughtful pause, then resumes the prince, "We must Learn from Yesterday, Live for Today, and look Forward to Tomorrow, for The Past be The Present, and No Less The Future."

Reply to
RoyalHeart

No. I'm currently using 0.22uF aluminum electrolytics. (Using what I have have in my parts stock until I can get the proper cap type. The circuit is currently breadboarded.)

As to the possible feedback, this is likely, I even investigated possible ground problems, rearraging the ground jumpers, star grounding, etc.

I forgot to add that the "squeal" occurs only when the tone control is at or very near maximum boost.

Ct is 0.01Uf, Cb is 0.22Uf (I don't have any 0.33 nor 0.39 handy).

Thomas

--

A thoughtful pause, then resumes the prince, "We must Learn from 
Yesterday, Live for Today, and look Forward to Tomorrow, for The Past be 
The Present, and No Less The Future."
Reply to
RoyalHeart

Thanks, Winfield, for the insight. It is greatly appreciated.

I don't dabble in audio circuits very much, being more of a digital hobbyist than an analog one.

Thomas

--

A thoughtful pause, then resumes the prince, "We must Learn from 
Yesterday, Live for Today, and look Forward to Tomorrow, for The Past be 
The Present, and No Less The Future."
Reply to
RoyalHeart

That's it, blather on, frog.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Reply to
Michael A. Terrell

Hi Win Just found a bit of Peasology about caps, (you have probably seen it)

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Also I wonder what happened to Tom Bruhns (sp?) capacitor self leakage test from a few years back

martin

Reply to
martin griffith

Yep. 0.47uF Al. Occurred to me from the start I would quite likely have problems starting with these input caps. But, again, using what I could find in my cap bins. Time to renew the stock.

(Why is it that everytime you get a new "toy" and are ultra-anxious to play with it, you can't find the proper supporting parts to go with it??? Sigh.)

Read about this trick so many years ago I all but forgot about it. Thanks for reminding me of it.

Curious: Polyester is what crossed my mind first (followed my mylar and metal film; ceramics I have read here on s.e.d, and elswhere, are big gotchas in AF circuits).

Another reason I need to replace them with different type caps.

Thanks again for the endorsement of good Ol' Poly caps.

Thomas

--

A thoughtful pause, then resumes the prince, "We must Learn from 
Yesterday, Live for Today, and look Forward to Tomorrow, for The Past be 
The Present, and No Less The Future."
Reply to
RoyalHeart

One of the reasons why I chose the LM1036. Less chance of picking up noise, and not having to worry about managing all the shield grounds and being careful not to inadvertently introducing ground loops.

Thanks for the heads up, Win. "Aej taanquuaetiiei uurtae naaliijeqq." [Old Tongue for "I thank Thee for Thy knowledge." I am also writing a novel, working on it now and then, that is set in a Medieval-like period, and from which my tag line is taken from. One theme of the novel is the evolution of a language, and I have a character who just coincidentally happens to be a paleographer and historiographer. Hmmm... Hey, Win: Can I model a character after you???]

Follow

"Maeaanuqae taanquuae" ["Many thanks"], and will do.

And thanks also for the cap recommendation.

Thomas

--

A thoughtful pause, then resumes the prince, "We must Learn from 
Yesterday, Live for Today, and look Forward to Tomorrow, for The Past be 
The Present, and No Less The Future."
Reply to
RoyalHeart

"RoyalHeart"

** Another gullible sucker bites the dusts.

Courtesy of Win - who now joins the ranks of audiophools and charlatans.

......... Phil

Reply to
Phil Allison

Okay, after perusing "Picking Capacitors" parts 1 and 2 (and which I'll thoroughly read a bit later, when I'll have more time), and per your suggestion, Win, polypropylene it is. Again, thanks for the suggestion, and yet another order to DigiKey is in the works.

"Teiqiiuu qaaraeei." [Take care.]

Thomas

--

A thoughtful pause, then resumes the prince, "We must Learn from 
Yesterday, Live for Today, and look Forward to Tomorrow, for The Past be 
The Present, and No Less The Future."
Reply to
RoyalHeart

Yawn. What a loser. :(

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Reply to
Michael A. Terrell

Elektor Electronics described a project using the LM1036, "Single Chip Tone Control" in April 2003 issue. I am currently in the process of making the boards (tone control and psu) for this unit.

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Select Construction Projects then from the drop down AUdio/Video Photography. Then type 'tone control' as the search criteria in the bottom window and the resulting list will contain 'Single-Chip Tone Control'. Clicking on this link will take you to the project where you can download the article for UKP1.00.

The schematic Elektor uses is almost identical to the NatSemi data sheet and electrolytic caps are indicated on pins 1, 5 & 16. All the rest are MKT.

Reply to
Ross Herbert

"Ross Herbert" :

** MKT = metallised polyester ( aka Mylar ) capacitor.

The most widely used type of plastic film cap.

........ Phil

Reply to
Phil Allison

I learned early on to completely ignore Phil. MHO is he has a "I am GOD" mentality, and is therefore ALWAYS right, and everyone else is ALWAYS wrong.

Thomas

--

A thoughtful pause, then resumes the prince, "We must Learn from 
Yesterday, Live for Today, and look Forward to Tomorrow, for The Past be 
The Present, and No Less The Future."
Reply to
RoyalHeart

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