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bypass cap on input film cap?
bypass cap on input film cap?
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Old 18th May 2018, 01:44 AM   #1
laserscrape is offline laserscrape
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Default bypass cap on input film cap?

before spending money on high quality input caps I experimented by adding bypass cap to existing input caps.

The current input cap is a 2.2uf polypropylene.

the polypropylene bypass caps used were :
Rifa 10nF 400V
Arcotronics 4.7nF 1600V
WIMA 0.1uF 100V MKP2

The 4.7nF sounded the best, the 0.1uf WIMA just sounded worse.

After settling on the 4.7nF and having a proper listen it is sounding like a solid improvement . better transient response and overall cleaner sound.

There was no control so no idea what factors are important.
the lower value the cap, the better it sounded. its also better to keep it low to avoid changing the filter characterisitics
the higher the quality, the better it sounded:
The Rifa and Arco have copper leads, Wima is not copper (steel?)
Arco had highest voltage rating.

Last edited by laserscrape; 18th May 2018 at 02:06 AM.
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Old 18th May 2018, 02:41 AM   #2
Bigun is offline Bigun  Canada
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bypass cap on input film cap?
I have used MKP before, tried a few different types over the years - but the best sounding cap to me and the one I use most now, is an un-bypassed Nichicon MUSE Bipolar electrolytic, around 10uF to 22uF - the green coloured ones. No doubt my ears aren't too discerning though.
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Old 18th May 2018, 04:04 AM   #3
laserscrape is offline laserscrape
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would you say the MUSE is colouring the sound in a positive way or do you consider it the most accurate cap aswell?
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Old 18th May 2018, 06:59 PM   #4
DF96 is online now DF96  England
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There is no need to bypass coupling capacitors. At best it makes no difference at all. At worst it could (just) insert a slight suckout at the frequency where the inductance of the big cap resonates with the capacitance of the small cap; this will normally be inaudible, but if heard some people may misinterpret the change as an improvement.

Quote:
Originally Posted by laserscrape
the lower value the cap, the better it sounded.
This is because a low value bypass moves any resonance out of the audio frequency band, so the bypass does less damage; at worst you just get some HF phase shift. The ideal bypass value for a coupling capacitor is zero.
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Old 18th May 2018, 07:09 PM   #5
laserscrape is offline laserscrape
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Quote:
Originally Posted by DF96 View Post
There is no need to bypass coupling capacitors. At best it makes no difference at all. At worst it could (just) insert a slight suckout at the frequency where the inductance of the big cap resonates with the capacitance of the small cap; this will normally be inaudible, but if heard some people may misinterpret the change as an improvement.


This is because a low value bypass moves any resonance out of the audio frequency band, so the bypass does less damage; at worst you just get some HF phase shift. The ideal bypass value for a coupling capacitor is zero.
appreciate the explanation. the 4.7nf bypass did seem to sound better but the least time was spent comparing the 4.7nf to no bypass cap at all because I thought it could only help, will have to check again.


also is there any potential benefit to adding a bypass cap even though its bad practice? like lower ESR?

Last edited by laserscrape; 18th May 2018 at 07:12 PM.
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Old 18th May 2018, 08:18 PM   #6
laserscrape is offline laserscrape
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did some tests and the 4.7nf definitely offers the best sound, there is no difference in the level of detail or tone. with the bypass cap the sound is faster, bass and treble are more independent from one another. with a very fast and bass heavy electronic music the differences are most clear.


To compare one channel had the bypass cap, the other didnt. the headphone's detachable plugs were shuffled blindly and reconnected.
for every track I would judge which sounded better then swap the plugs and judge again, this eliminates driver inconsistencies and hearing inconsistencies. The amp is op amp based so channel differences, if any, are very small but I made sure to use the opposite channel from the first test to guarantee that its the bypass cap making the difference.

the test tracks were converted to mono aswell.
all 5 tracks I prefered the bypass cap and was able to guess which was which
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Old 18th May 2018, 08:38 PM   #7
Keruskerfuerst is offline Keruskerfuerst  Germany
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What type is that Polypropylene cap ?
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Old 18th May 2018, 08:58 PM   #8
laserscrape is offline laserscrape
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Quote:
Originally Posted by Keruskerfuerst View Post
What type is that Polypropylene cap ?
MKP
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Old 18th May 2018, 09:15 PM   #9
phase is offline phase  United States
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I recently used a 10uf Nichicon Muse for an input cap, and found that the Wima MKP10, in .22uf 400v works very well in unison.

It is very easy to produce interactions between the parts, that doesn’t sound very good, just have to search for combinations that work.
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Old 18th May 2018, 09:17 PM   #10
Bigun is offline Bigun  Canada
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bypass cap on input film cap?
Quote:
Originally Posted by laserscrape View Post
would you say the MUSE is colouring the sound in a positive way or do you consider it the most accurate cap aswell?
That's a good question. I'd have to say that it's hard to tell, the sound doesn't seem coloured to me and neither was it my aim to make the sound 'nicer'.

The MKP sounded accurate but also 'hard' sounding. I didn't like it and I would have called it coloured except that this didn't make sense to me how a film cap could sound coloured so I left it as a mystery.

In my TGM3 where I used a Tantalum (an old blue drop) the sound was definitely coloured slightly, and for the better.
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