Marantz CD63 & CD67 mods list - Page 1370 - diyAudio
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Old 10th December 2009, 06:54 PM   #13691
avr300 is offline avr300  Denmark
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Ray - congrats..
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Old 10th December 2009, 09:00 PM   #13692
SimontY is offline SimontY  United Kingdom
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Here's my pseudo-science answer:

Theoretically more caps in parallel could be better, but too low impedance at certain frequencies could cause the circuit to resonate/ring or upset other things like voltage regulators and hence it sounds bad. It seems a smooth and low impedance curve is what we want.

A rule of thumb for capacitor bypassing I heard is to use 1/10 of the capacitance, e.g. 1000uF cap should be bypassed with a similar cap of 100uF. 100uF would be bypassed with 10uF. It is rarely done like this in practice, for some reason - perhaps because for analogue circuits it's usually not done at all, and in digital ones the small film caps are there specifically to deal with really high frequency noise.

Much smaller bypass caps can cause a sharp resonance and that is perhaps audible in how it effects the circuit. The resonance can be damped by a resistor, and then you have a snubber circuit. Something like 100nF and 1R has been used in power amplifier power supplies.

As for mixing electrolytic caps I don't know why it's technically bad but there have been various accounts by the keen-eared of these combos being hit and miss sonically. The sound being "confused" has been mentioned before in other threads!!

Simon

Last edited by SimontY; 10th December 2009 at 09:03 PM.
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Old 11th December 2009, 08:58 AM   #13693
RCruz is offline RCruz  Switzerland
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I had similar issues when paralelling different types of EL.

Even as psu smoothers, different build EL can produce an incoherent sound.

Ricardo
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Old 11th December 2009, 10:34 AM   #13694
6h5c is offline 6h5c  Netherlands
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Quote:
Originally Posted by avr300 View Post
Ray - congrats..
Thanks avr! She's a really sweet little girl, only not last night!

Ray
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Gonna buy my little girl a pink soldering-iron
The new DOS-CFP board is out!
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Old 11th December 2009, 11:27 AM   #13695
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Interesting...
I might take them off everywhere were they are in parallel:

+/- 12V rails (since the lm317/337+caps are in parallel with c805/806)
Servo (since in parallel with 2 other caps on each supply as well)

However... on Ray's pictures I see that he retains the caps on the regulators for the +/-12V rails. No electrolytes though
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Old 11th December 2009, 11:30 AM   #13696
SimontY is offline SimontY  United Kingdom
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This effect doesn't seem to apply or is less pronounced if there is some physical distance between the caps e.g. cap after regulator is different to local decoupling cap.

Simon
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Old 11th December 2009, 11:32 AM   #13697
SimontY is offline SimontY  United Kingdom
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Just done a couple more tweaks on Steve's CD63, partly for my own amusement.

I changed C505 to a 2200pF polystyrene (HF signal runs through this), as well as C601-C602 filter caps to ps. I also put a slightly better cap on C814 (-10V).

The sound is certainly more open and coherent. Very nice improvement for a few cheap part swaps.

Simon
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Old 11th December 2009, 11:44 AM   #13698
SimontY is offline SimontY  United Kingdom
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There's some genuine big earthy detail coming off the piano on Diana Krall now, Steve's gonna be a happy man...!

Any issues with the sound on this player are v slight now and would almost certainly disappear with a couple of low noise regs and better output stage, plus the servo re-clock... it never ends really.
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Old 11th December 2009, 12:36 PM   #13699
RCruz is offline RCruz  Switzerland
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Hi Simon

I believe you are now hearing the effect of the C505 2200pF polystyrene.

It is one of the most revealing mods I did.

Ricardo
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Old 11th December 2009, 01:41 PM   #13700
SimontY is offline SimontY  United Kingdom
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Hi Ricardo,

I'm glad you commented on this. I strongly suspected the improvements were 90% that cap. To look at it in the service manual it looks very important, and to see in the flesh this puny cheap ceramic toilet-waste cap I felt it would be a good price-performance ratio mod!

Simon
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