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Old 1st March 2006, 07:47 AM   #1
beppe61 is offline beppe61  Italy
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Default Are coupling caps such a disaster for sound?

Dear Sirs,

I notice that a lot of efforts are done, for instance in preamps, in order to avoid couplind caps.
Are they so bad for sound ?

Opinions and suggestion of good film caps are very welcome.

Regards,

beppe
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Old 1st March 2006, 08:37 AM   #2
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Hi Beppe

By now you probably realise that asking questions rarely yields answers. And the answers are usually meaningless and conflicting unless you already have lots of first hand experience and understanding.

How bad are caps then? It seems very few systems exist with no caps in the signal path. If your main source is a cartridge, this automatically means replacing caps with transformers and trying to choose the lesser evil. Depending upon the system i use between 2 and 4 transformers in the signal path and find their distortions more musically acceptable than those of caps. Others will, no doubt, differ.

DC coupling is probably best but not easy to implement. The average textbook dc servo seems more harmful than the cap it replaces.


Of course, unless you use batteries there are always the caps in the PS. One way to minimise their flavour is to use small caps and large chokes, but this works well only in tube curcuits.


Would i say that removing a coupling cap is worth all the effort, expense and annoyances? By all means yes - listening to an entirely cap-free system is a great experience.
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Old 1st March 2006, 09:02 AM   #3
beppe61 is offline beppe61  Italy
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Quote:
Originally posted by analog_sa
Hi Beppe
1) By now you probably realise that asking questions rarely yields answers.
And the answers are usually meaningless and conflicting unless you already have lots of first hand experience and understanding.
2) How bad are caps then?
It seems very few systems exist with no caps in the signal path. If your main source is a cartridge, this automatically means replacing caps with transformers and trying to choose the lesser evil.
3) Depending upon the system i use between 2 and 4 transformers in the signal path and find their distortions more musically acceptable than those of caps.
Others will, no doubt, differ.
4) DC coupling is probably best but not easy to implement.
5) The average textbook dc servo seems more harmful than the cap it replaces.
6) Of course, unless you use batteries there are always the caps in the PS.
One way to minimise their flavour is to use small caps and large chokes, but this works well only in tube curcuits.
Would i say that removing a coupling cap is worth all the effort, expense and annoyances? By all means yes -
7) listening to an entirely cap-free system is a great experience.

Thanks a lot for a reply full of interesting points of discussion.
1) I am here first of all to gather valuable opinions from audio experts like you and I thank you for that.
I find the discussions always stimulating.
Nevertheless I understand that the answers usually do not come easy, beacuse a lot of parameters play.
2) Presently I listen to an humble power amp with no caps in the signal path. My opinion is that it is slightly let down by the preamp actually and it is not bad all in all.
My main/only source is a CD player.
Now that you talk about coupling transformers I read positive reviews of transformer coupled preamps with digital sources as well.
If they were not so expensive I would like to try one, one day.
3) Very interesting. Once I thought that transformers added great amount of distortion. But after having seen some really impressive distortion spectrum from a McIntosh amp I am not so sure.
Maybe the best transformers are the best thing for DC blocking.
My mind always go to Audio Tekne brand. Do you know it?
4) I see it very well.
5) Interesting.
6) Also with batteries some caps are needed in the PS to low down their impedance I think (at least with lead batteries).
7) In what sense? Could you tell me something about that experience ?

Thanks a lot.
Kind regards,

beppe
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Old 1st March 2006, 09:21 AM   #4
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Hi Beppe

Quote:
Maybe the best transformers are the best thing for DC blocking.

Sadly, this is not normally the case. The best interstage transformers cannot take any reasonable amount of dc current. I dare not let more than a single mV dc in the TVC after Thorsten's recommendations. If you want to use transformers to block dc you should look at balanced circuits where the dc component in the transformer primary is zero. Not easy to keep the balance though.

Or you may try building one of the servos from curldiy.com
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Old 1st March 2006, 09:23 AM   #5
lineup is offline lineup  Sweden
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Thumbs up Coupling Capacitors - caps good or bad

.
1. Thank you very much Mr Beppe61. New interesting topic, again!

2. I do not mind using coupling caps. Always try to find best quality: Polypropylene.
- Comes from I often like to use only single ended power supply.
- They are easy and simple to make. +9 Volt Battery and 0 Volt=Ground
- Here talk about small transistors preamplifiers.

3. I do not mind building simple power amplifiers, too.
- With only single sided power supply.
- Here I must use output Electrolytic Capacitor.
- I use 4700uF Axial good quality caps for my 6-8 Ohm loudspeakers.

4. Regards from Mr Lineup

5.
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Old 1st March 2006, 12:55 PM   #6
Eva is offline Eva  Spain
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beppe61:

The best way to know is to try it in a double blind test.

Prepare a test setup where a switch allows to include or by-pass 10 or more series-connected low-cost electrolytic capacitors in the wire coming from the preamplifier to the amplifier. If the switch produces any noise, then add an additional placebo switch capable of producing the same noise but without doing anything else.

Ask a friend to activate the switches randomly where you can't see him, and try to guess if the capacitors are or not bypassed.

I've read about a similar test with several dozens of low-cost op-amps connected in series, and the "audiophiles" failed nearly 50% of the times. Note that 50% is the probability of failing when guessing the flip of a coin.
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Old 1st March 2006, 02:03 PM   #7
beppe61 is offline beppe61  Italy
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Default Re: Coupling Capacitors - caps good or bad

Quote:
Originally posted by lineup
.
1. Thank you very much Mr Beppe61. New interesting topic, again!
2. I do not mind using coupling caps.
Always try to find best quality: Polypropylene.
- Comes from I often like to use only single ended power supply.
- They are easy and simple to make.
+9 Volt Battery and 0 Volt=Ground
- Here talk about small transistors preamplifiers.
3. I do not mind building simple power amplifiers, too.
- With only single sided power supply.
- Here I must use output Electrolytic Capacitor.
- I use 4700uF Axial good quality caps for my 6-8 Ohm loudspeakers.
4. Regards from Mr Lineup
5.
Dear Mr. Lineup,
maybe some of my problems are just ramblings, but that is.
1)2) I prefer PP caps as well for signal coupling.
Batteries based PS are very interesting but a little complex to use.
I can understand that the noise is minimal in this case.
3) Interesting, Thanks for the info.
4) Kind regards,

beppe
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Old 1st March 2006, 02:07 PM   #8
beppe61 is offline beppe61  Italy
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Quote:
Originally posted by Eva
beppe61:
1) The best way to know is to try it in a double blind test.
...
2) I've read about a similar test with several dozens of low-cost op-amps connected in series, and the "audiophiles" failed nearly 50% of the times.
Note that 50% is the probability of failing when guessing the flip of a coin.
Dear Miss.Eva,
1) Thank you for the very interesting procedure explanation.
But I would be very interested to know your opinion.
Are some caps better than others for coupling applications?
What do you use?
2) Very very interesting. Do you have any link to this article?
It should be a very interesting reading.

Thanks a lot for the extremely interesting information and advice.
Kind regards,

beppe
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Old 1st March 2006, 02:11 PM   #9
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Dear Mr Beppe61,

Even some of the respectfull designers take this differently. Mr. John Curl seems to be allergic to caps (and also inductors).
His friend, Mr. Nelson Pass, uses caps, even in the output of his very updated power amps designs (ZV9), and one who build/heard it gives it good review about good sounding.
Some of the legendary amps like JLH have caps in the output node.

As our Mr. Lineup and Mrs. EVA mentioned, maybe you yourself should decided whether you should use or not using caps in your cct. But for myself, putting caps does more advantage than drawback (when solving problem like blocking DC offset). Trying to solve this kind of problem without caps will result in far more complex cct, usually not sounding better than putting 1 cap.

Kind Regards, lumanauw
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Old 1st March 2006, 02:12 PM   #10
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Oh sorry.....

Is it Mrs EVA or Miss EVA?
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