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Old 21st March 2003, 01:06 PM   #1
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Default Which caps to use in Leach Amp?

Hi,

I'm trying to build a Leach Amp and wonder which capacitors to use for the circuit. I'll try to follow Prof.Leach's suggestions. Furthermore I prefer buying from Farnell in Norway, so the choices are kind of limited to what they sell.

What I'm most confused about is the film caps. The possibilites I've found so far are these:

wima MKS4, 160V
wima MKS2, 63 or 40V
wima MKS02, 40V
wima FKS2, 63V *
wima FKP2, 40V *
vishay MKP1837, 100V

*) these only come in the smallest of the values I need.

BTW; how critical are the voltage ratings on these caps, and when the professor says a cap should be 50V does this mean 50Vdc or 50Vac? (The ratings listed above are a.c.) Should I use 63V or 40V when he says 50? Could I use 100V or even 160V when he says 50 as well as when he says 100?

For the electrolytics I guess I'll go with Panasonic FC, but I haven't really checked for alternatives.

Farnell only seem to have one kind of silver micas, so they'll have to do.


All comments would be helpful.
-truls
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Old 21st March 2003, 05:34 PM   #2
Jeff R is offline Jeff R  United States
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The voltages are DC and are not especially critical, though you should not use lower rated voltages. In other words, to substitute a 50 volt cap you could use a 75 volt part, but probably not a 25 volt part. Of course, the printed wiring board that Leach sells is sized to accomodate the parts he lists.

I wonder if the ratings you give are AC, however. Typically the ratings are for the DC working voltage - you don't generally apply AC to nonpolar electrolytics.

I recommend building the amp with what you have described, then later you can try out some different types of caps to see if you can hear a difference. If you try out any esoteric caps at the beginning, limit them to the feedback network.

Good luck.
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Old 21st March 2003, 06:23 PM   #3
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Thanks Jeff.

So, this means that I could use the WIMA MKS2 caps rated at 100Vdc and 63Vac both when 50 and 100V is required? (which would be all the film caps in the Leach Amp)

How does MKS2 compare to MKS4, and what about the Vishay MKP 1837 caps?

-truls
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Old 21st March 2003, 07:11 PM   #4
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I'd further suggest a *blind* listening test. I used to think there were significant differences in the "sound" of components but, within reason, I don't anymore. Have a look at this post if you're interested:

http://diyaudio.com/forums/showthrea...threadid=12752

That's not to say that using the wrong part, in a critical part of a circuit won't hurt the sound, but I've learned there just aren't audible (or measurable) differences between brands of similar poly capacitors or between different metal film resistors, etc. So save your money, and select the least expensive ones that meet the circuit's requirements.
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Old 22nd March 2003, 05:21 AM   #5
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Quote:
Originally posted by nw_avphile


That's not to say that using the wrong part, in a critical part of a circuit won't hurt the sound, but I've learned there just aren't audible (or measurable) differences between brands of similar poly capacitors or between different metal film resistors, etc. So save your money, and select the least expensive ones that meet the circuit's requirements.

For some reason that post slipped my attention when it was under moderation. Seeing it, I would think twice before releasing it to view by everybody,
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Old 22nd March 2003, 06:34 PM   #6
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Ok, I have the choice between Wima MKS2 caps that fit the requested voltage ratings pretty closely or the more expensive Vishay MKP 1837 caps that are rated 160V. Based on nw_avphile's statement above, I'd guess that the MKP caps are better than the MKSs since all MKPs performe about the same(??). Is it a bad idea to go for the 160V caps when the required ratings are 50 and 100 volts? This will cost more, so I only want to use the MKPs if they are unquestionably better.

tnx,
-truls
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Old 22nd March 2003, 07:45 PM   #7
Cobra2 is offline Cobra2  Norway
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Default IMHO...

I have found higer voltage caps to sound better (whitin same family).
But the differences may be (very)small...

Arne K
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