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AR-9 / AR-90 Crossover Re-capping Adventure


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5 hours ago, DavidR said:

Carl (and others),

What do you think of Tony's descriptions of the different caps he's auditioned? Even Michael Jantzen has said this to me in an email:

"For series connected caps  on the mid-range section and especially for the tweeter section, Super caps (like our Superior, Silver & SilverGold) makes a hearable difference, but even here, we are talking about small nuances and it will also depend on the other equipment in your setup, the media you play, type of music etc.

As with all things audio, it is always a personal preference in sound and also a question of investment versus gained performance."

 

I'm sure that with my age, lots of loud music when younger and 40 years spent mostly in manufacturing I wouldn't hear much difference.

I agree with completely with Michael Jantzen's comments. I wrote about those small nuances previously as being at the crux of the capacitor cost vs benefit law of diminishing returns. 

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9 hours ago, Aadams said:

I am not trying to influence opinions with this post but I do have 2 questions.  If today's caps had been available when the AR9 was designed which caps would, in your opinion, have been specified by the designers?  Also, which of todays caps most closely conform to what was originally specified?

Adams

I think Roy and Carl have stated this.

Q1: Electrolytics and maybe mylar for the tweeter and UMR.

Q2: See answer to Q1

As far as I know no one really knows, or has stated, what the black caps with red ends are in the tweeter and UMR section.

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45 minutes ago, DavidR said:

As far as I know no one really knows, or has stated, what the black caps with red ends are in the tweeter and UMR section.

They are electrolytic caps, David...These caps have been shown to have the highest ESR of any capacitor used in an AR speaker. This suggests that replacing them with any capacitor arrangement providing significantly lower series resistance will take the sound into "brighter", possibly harsh territory, regardless of the price or the quality of the replacement cap(s) used.

Roy

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12 hours ago, RoyC said:

They are electrolytic caps, David...These caps have been shown to have the highest ESR of any capacitor used in an AR speaker. This suggests that replacing them with any capacitor arrangement providing significantly lower series resistance will take the sound into "brighter", possibly harsh territory, regardless of the price or the quality of the replacement cap(s) used.

Roy

Wow

I opened one up and its full of what appeared to be polyethylene (plastic) film. My limited experience in this area led me to believe they were some early type of film cap.

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6 hours ago, DavidR said:

Wow

I opened one up and its full of what appeared to be polyethylene (plastic) film. My limited experience in this area led me to believe they were some early type of film cap.

Interesting...Did you take any measurements? My information is based on John O'Hanlon's work of some years ago, when he tested many AR capacitors sent to him by forum members. I have not dissected one of these as you have, though I have measured a number of AR red and black caps.

Perhaps we should take a closer look. Do you have any photos or others to test? Just sent you a PM

Roy

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Roy,

The black caps with red ends came from an AR91. I no longer have them nor did I take any pictures. I have readings but they are only uF readings. Do I use my Fluke on the OHM setting to get ESR reading ?

If they are electrolytics then I may need to re-think my caps I have set aside for my 90s. I am pleased with the recap of the 91s. I can't post the readings or my caps list for the 90s as they are on a laptop that crashed this morning. I was finally able to get it to boot up and I'm running a virus scan. I need to put all my files from that unit on a thumb drive. Its the 2nd time it has happened!

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2 hours ago, DavidR said:

Roy,

The black caps with red ends came from an AR91. I no longer have them nor did I take any pictures. I have readings but they are only uF readings. Do I use my Fluke on the OHM setting to get ESR reading ?

ESR can only be measured with a meter having that feature. I have 2 meters capable of measuring it. I should be seeing some of these caps again soon enough, and will report back when I do.

Roy

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I have 4 of the black and red caps somewhere from a Pair of British built AR-16  1977 vintage. I am pretty sure they had NPE stamped on them though. If and when I find them I will update this message.

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4 hours ago, RoyC said:

My information is based on John O'Hanlon's work of some years ago, when he tested many AR capacitors sent to him by forum members.

I remember John saying to ALWAYS ditch the black and red caps. For those who don't know, John is Professor Emeritus of Electrical and Computer Engineering and an IBM alum. He's a true scientist and has access to all kinds of cool test equipment. So if John says the black and red caps are crap you can take that to the bank.

As I recall, he said the problem was that the black body is PVC but the red end is a different material, so they expand and contract at different rates and are therefore guaranteed to leak.

Add to that the fact that I opened a KLH Seventeen once and found an EXPLODED Callins cap, and my practice is to always replace them.

Recently I bought an AR receiver and because I had read they are tricky to work on, I just took it to my favorite technician, Tim Schwartz. Tim is not a proponent of wholesale re-capping but after he fixed something that was obviously wrong he returned the receiver to me and suggested I replace all of the electrolytics BECAUSE they were Callins.

Today, after reading some of the recent posts here, I gathered a bunch of those caps from the discard can on my bench. Of the 16 caps I had saved, values range from 1uF to 450uF. Just checking capacitance, the 1uF are OK (7 of them measured between 0.95 and 1.25) but the higher the value, the more they were off.

One 5uF measured 10.49, another measured 0.0 (zero).

Four 150uF caps all measured ~1500uF

A 300uF measured 1700.

The two 450uF measured 5000

So... I'll echo John's advice: If you come across black and red Callins (or Temple or Whale) caps, replace them.

-Kent

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I found this picture on the internet. I think it might be Kent's as it was from the CSP. It shows the red plastic like film I encountered.

The fact that I keep reading responses like Kent's and Carl's is why I want to recap my 90s.

post-101828-0-83775400-1370107770.jpg

 

107770 - Copy.jpg

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6 minutes ago, DavidR said:

I found this picture on the internet. I think it might be Kent's

Yeah-- as a matter of fact I was about to add that to my post but no need now.

-Kent

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18 hours ago, RoyC said:

They are electrolytic caps, David...These caps have been shown to have the highest ESR of any capacitor used in an AR speaker. This suggests that replacing them with any capacitor arrangement providing significantly lower series resistance will take the sound into "brighter", possibly harsh territory, regardless of the price or the quality of the replacement cap(s) used.

Roy

6 minutes ago, Aadams said:

Understood. I am just waiting for the answer to the question, " are they film or electrolytic?"

Answered earlier in the discussion.  Now, DavidR and I just need to get off our duff's and recap our 90s, even though we're both still confused about it.

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6 minutes ago, DavidR said:

None of the ones I pulled from my 91s had a manufacturer's name of designation

1068 on the 100uF is Callins. Can't see the others in the photo but if you check you'll probably find EIA code 1068.

https://nebula.wsimg.com/a9c854152f0efe9d9dc0ce5760f53301?AccessKeyId=1884AA24B5A4B33E3F2B&disposition=0&alloworigin=1

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3 hours ago, DavidR said:

Do any members have a few of the black caps with red ends to send to Roy for inspection and testing?

Been there done that some time ago. DavidR, click on the link below and read the whole post and the prior post that explains the test methodology.

 

 

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1 hour ago, JKent said:

1068 on the 100uF is Callins. Can't see the others in the photo but if you check you'll probably find EIA code 1068.

https://nebula.wsimg.com/a9c854152f0efe9d9dc0ce5760f53301?AccessKeyId=1884AA24B5A4B33E3F2B&disposition=0&alloworigin=1

Thanks Kent

We are referring to just the black ones with red ends. However, the pdf in your link on Callins Caps had a picture of the black cap w/ red ends and the description says they are ELECTROLYTIC. I would have expected paper and aluminum foil w/o that plastic material.

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Someone mentioned seeing some caps in British speakers with black bodies and red ends. I don't know if they are the same as what we've been discussing. I think it's just coincidence they look the same.

I am quite sure though there was an era where a cap manufacturer made and private labeled caps for speaker manufacturers. They basically made the same cap with black body and red ends and printed whatever the customer wanted on the black. KLH was a big user of them, but there were many other speaker brands also. 

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3 hours ago, Carlspeak said:

I am quite sure though there was an era where a cap manufacturer made and private labeled caps for speaker manufacturers. They basically made the same cap with black body and red ends and printed whatever the customer wanted on the black. KLH was a big user of them, but there were many other speaker brands also. 

Thanks for the reminder, and the link to your measurements, Carl. They are consistent with John O'Hanlon's findings. I agree...those red and black caps are unlikely to be any different than those found in KLH and other speakers of the era. You've also confirmed the high ESR associated with these caps. David had me wondering what it was he saw when he opened his specimen, but Kent reminded me of John's comments, which were very specific and very much in line with your findings.

I've been intrigued at the behavioral differences between film and electrolytic caps of late. Although it is less pronounced than the black and red variety, it is apparent that even new electrolytic cap values rise as frequency goes down (unlike film caps). It is why many mainstream capacitor meters are showing high readings for new npe's. These meters are measuring at frequencies as low as 8hz.  I'm also finding Erse npe caps to be physically smaller and more variable than others (Parts Express and Bennic). I won't be using or recommending Erse npe's in the future.

Roy          

 

 

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16 hours ago, Stimpy said:

............................................ Now, DavidR and I just need to get off our duff's and recap our 90s, even though we're both still confused about it.

LOL. At least I have my caps in-hand. Which may not be a good thing at this point.

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11 hours ago, RoyC said:

 ................... David had me wondering what it was he saw when he opened his specimen, ............................................................

Roy          

 

 

Roy, in the attached picture you can see a red material. It appeared to me like a polyethylene type material.

107770 - Copy.jpg

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