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-   -   Tripath Input Coupling Caps (http://www.diyaudio.com/forums/class-d/101344-tripath-input-coupling-caps.html)

Davet 5th May 2007 08:40 PM

Tripath Input Coupling Caps
 
There was a thread a year and some months ago regarding input coupling caps in the T-Amps.

Original Coupling Capacitor Thread

I have been in contact with Michael Mardis regarding testing circuitry and I will be testing a number of capacitors over the next few months.

The circuitry will have stereo (two gang) switches on each channel. Therefore, the cap under test will be the only cap in the circuit. There will be no parasitic influences from other capacitors with this arrangement. All other capacitors will be electronically removed from the input circuitry. Using two sets of switches will provide the capability to compare one cap on channel A and another on channel B.

It is my intent to have the various capacitors listened to by musicians, music lovers, and audiophiles, but not anyone who really has an electronics background beyond myself will be listening to the caps under test.

I would appreciate any other consideration that comes to mind that may be employed as I undertake this task.

The proposed testbed will be a modified SI T-AMP with the forementioned switches in each channel. At some later time I will undergo the test with a 41HZ Amp6 and possiby a TA-10.1.

The Caps I currently have at hand are:

Obligatto Copper Case 2.2 MFD
Obligatto Paper In Oil (PIO) 2.0 MFD.
Auricap 2.2 MFD
Blackgate 2.2 MFD
Russian PIO 2.0 MFD

I have a number of Russian Teflon 0.1 MFD caps which I may use at some point to bypass PIO caps.

BWRX 5th May 2007 09:57 PM

A 16V 2.2uF electrolytic (Panasonic FC) and a 50V/63V 2.2uF MKT film cap.

Conrad Hoffman 5th May 2007 10:45 PM

I just spent some time comparing caps in a similar fashion, but making a high gain differential measurement between two channels, each with a particular cap. It was not possible to get a good null across the audio band unless the caps were matched in value to a high degree. IMO, if one can hear anything, one can hear slight differences in the frequency response caused by mismatched caps. When the caps were matched, little difference was measured or heard between various film types. I don't have any Black Gates or other exotics, but no electrolytics could produce a good null, leaving some obvious hash in the audio band. I believed I could hear the difference as well. Thus, my advice is to only compare caps that measure close to identical in value, say 1-2%, and never try to compare a cap to a wire- they don't result in identical signals for obvious reasons. There may also be mismatches between the channels of your amp, unless you confirm them to match with a high gain differential measurement. Just comparing outputs on a scope isn't good enough. Without these precautions, the results of the listening tests lose a lot of meaning.

theAnonymous1 5th May 2007 10:54 PM

How about no caps. It's so easy to do I don't see why more people don't do it. I've done it on a few AMP3's and AMP32's and haven't had any problems.

The sound could be described as "capless".:clown:

http://i19.tinypic.com/4u27puc.jpg
http://i19.tinypic.com/52efm7n.jpg

serengetiplains 5th May 2007 10:57 PM

Davet, if your Russian caps are hermetically sealed, and if you send me some, I'll inject them with Fluorinert and send them back to you. I've been experimenting with Fluorinert lately and find it to have premium dielectric qualities. Teflon/Fluorinert caps are better than anything I've heard (I've pretty much bought/heard/measured everything out there).

And if you have any hermetic sealed Russian caps you care to get rid of, I'll take them off your hands!

Pano 6th May 2007 01:26 AM

Dave, are you going to build the burn circuit I sent?

If you don't burn them in, you know you will get a lot of "these caps don't sound good until after 500 hours" type of thing. ;)

Just want to insulate you from an obvious complaint. It might also allow you to compare a fresh cap with one that has some "miles" on it.

Looking forward to your findings!

BTW, I second Brian's vote for Panasonic FC. 2.2 or 3.3uF
And maybe some generic electrolytic and film cap.

Davet 6th May 2007 06:14 AM

Capacitor Burn in Circuit.
 
Michael, I plan to build and use your burn in circuit.

I don;t have the Panasonics on hand; unless they are the ones that came with the Amp6. At this point I do not plan to purchase all the various caps available. Maybe over time I will test a great number of them, but initially I will test those listed above. In addition I do have some 5 MFD Polycarbonates, Solens 3.3 MFD, and some Dayton films that I may try as well.

The Auricaps have been in my SI T-Amp for the past 5 months. I swapped out the Auricaps for the Obligatto PIOs today. The PIO seem to provide fuller bass and smoothed the highs a little. My initial impression was the PIO don't have the focus/definition that the Auricaps yield. The PIOs provide a broader soundstage, but the musicians do not seem to have the air around them of the Auricaps.

This initial impression is based on 3-hours of my listening.

BWRX 6th May 2007 12:38 PM

Dave,

I can send you a bunch of 2.2uF Panasonic FCs and some of the 2.2uF MKT films caps. Send me an email with your address and I'll mail them to you.

My ears have led me to like no coupling caps the best - this wasn't with any Tripath amp though ;) With Tripath based amps I like the Auricap the best. The MKT was my next favorite.

soongsc 6th May 2007 12:41 PM

Quote:

Originally posted by serengetiplains
Davet, if your Russian caps are hermetically sealed, and if you send me some, I'll inject them with Fluorinert and send them back to you. I've been experimenting with Fluorinert lately and find it to have premium dielectric qualities. Teflon/Fluorinert caps are better than anything I've heard (I've pretty much bought/heard/measured everything out there).

And if you have any hermetic sealed Russian caps you care to get rid of, I'll take them off your hands!

Better than V-caps? Isn't Fluorinert some sort of coolling liquid?

Alastair E 6th May 2007 03:05 PM

Quote:

Originally posted by theAnonymous1
How about no caps. It's so easy to do I don't see why more people don't do it. I've done it on a few AMP3's and AMP32's and haven't had any problems.

The sound could be described as "capless".:clown:

http://i19.tinypic.com/4u27puc.jpg
http://i19.tinypic.com/52efm7n.jpg


Unfortunately, Doing this modification, In Some Cases, where the source equipment has, for some reason Not got O/P coupling-caps, and has a voltage-offset , then the tripath will amplify this and produce a large DC voltage offset at its O/P....

This could easily ruin a speaker or the tripath chip, blow-fuses etc...

Not a good idea to remove the coupling-caps at the I/P....


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