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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Ceramic Power Supply Coupling Caps - Replace?? posted by Audiophile-in_Training on November 13, 2005 at 07:27:00:
I am modding a Flying Mole DAD-M100proHT digital amp
Flying Mole amps are extremely well designed equipment with no bullshit in it. Good choice !
I have already decided on replacing the input coupling caps with Black Gates of the same value,
Why not? Ask your girlfriend or boyfriend if s/he hears a difference (without telling him/her if you made the mod, obviously). Tell us the results.Replacing the 2 ceramic "safety recognized" Murata output coupling caps (KH472M and KH222M)with film-type (they are 4700pF and 2200pF, 250V). They connect the PS to the amplifier section.
I see no reason why you should do that (since no audio passes through them). I see some reasons why you should not:(1) the amp has been EMI/FFI certified with these caps and their characteristics. Often, the layout is done in order to deal with the cap's ESL. Change them, and you will jeopardize this fine tuning. (2) To design a digital amp in which changing the output common mode DEcoupling caps would change anything in the sound would be the evidence of a monumental incompetence, which is not the case of Flying Mole designers ! So, don't expect any change. (3) you could say, "well, I don't care about EMI/RFI certification, the Well Respected Audio Guru Jim Diamondear wrote somewhere those caps blur the bass imaging, so, I'm gonna make the mod". Think that you're likely to emit more EMI perturbation than previously, and given the scandalous EMI/RFI susceptibility of most other high-ends audio gear (most of them being not even tested in this regard !), you're likely to rotten your sound by some way. (obviously, since you made the mod yourself, human self-lenience will likely blind you to this fact...). Bypassing the two big Nichicon electrolytic 390uF, 200V PS caps with film caps (the biggest I can fit may be ~1 uF,though - is that too small?)
Don't. Paralleling the original cap with film caps will in fact be paralleling with caps in serial with their ESL. You are at risk of oscillations in the MHz range. The oscillating tank would be the power supply line (drawn as a transmission line), the cap and its parasitic elements).
BTW, the same phenomenon would exist with class A or B amps, but, since the current slope is slow (it's the audio signal), it quite does not trigger the tank. A class D amp, with its di/dt in the amp/ns range, would.
Also thinking of replacing the ceramic shunt cap in the output low-pass filter with film cap or Black Gate.
why not? Just be careful to use a cap with the same dimensions so that it fits exactly in the original holes. If not, you would add a curved lead which would give inductance in serail with the cap, and would jeopardize the filter functionnality in its highest frequencies. in the same vein, be careful to keep the cap orientation, in order not to modify the mutual inductanc e between the cap's wires and foil and the surrounding components.
Tell us the result after an honest boy/girl-friend testing.
A bet: if you hear something, it will be for the later mod. The first mod is inaudible. Just a bet. Tell us if I'm wrong...
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Follow Ups
- Re: Ceramic Power Supply Coupling Caps - Replace?? - Jacques 09:51:41 11/13/05 (0)
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