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Old 3rd October 2003, 04:36 PM   #1
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Default NAD C541i: possible tweaks and mods?

Hi, this is my first post...
I own NAD C541i player and like it very much but would like to improve it, if it is possible.
I'm thinking especially about op-amp replacement. I found two dual OPA2604 inside. Will replacement for say OPA627, OPA637 make any sense? And what about capacitor replacement/shortcutting? Does anyone have any experience with tweaking this player? Where can I found the schematics?

Thanks for any input.
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Old 13th October 2003, 10:07 AM   #2
Jay is offline Jay  Indonesia
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Hi new member,

1) I don't have the schematics. Most CDP circuits are standard. If you can post the close up picture of the PCB, many will recognize the schematic diagram.

2) It does make sense to totally upgrade a cheap CDP (say using NE5532), but a mid-end like C541? Not so I guest. But you can always "upgrade" or "exchange" () to improve it...

(a) The diode. Replace with MUR type (MUR140, MUR160, etc.). All.

(b) External clock and buffer. That is what I think not available with such CDP. More appropriate than changing the Op-Amps. A major and important upgrade (no exchange).

(c) Remove transistors for muting. I think the CDP uses these. But you will need to know the circuit (I think it is not dificult to open and see)

(d) Replace small caps surrounding the Op-Amps with quality ones (Paper is I think preferrable). These are caps for feedback and coupling or RC filter, not power supply caps.

(e) Fix the power supply regulation ( hence noise), then you can safely remove any RC or LPF to increase the sonic. Or reduce the capacitance (use Silver Mica).

If I'm not mistaken, this CDP uses Muse caps. Don't think it is necessary to replace it with BG or Oscon. The electrolytic DC coupling caps will introduce distortion but to use MKPs they might be as big as 100uF or at least 47uF. May want to try non-electrolytics with smaller capacitance, but watch for the bass response.

OPA2604 is a dual opamp while OPA627/637 is single. Exchanging is not easy, and I doubt a plug-and-play (without changing the whole DAC output circuit) will bring improvement (surely won't be proportional to the upgrade cost), IMO.
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Old 13th October 2003, 05:36 PM   #3
jwb is offline jwb  United States
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I opened up this player and found there was nothing I really wanted to do with it. Not only does the player have a fairly good sound, especially for the money, but the construction is quite nice. Each section of the player operates from its own secondary transformer windings, and there are local regulators. You might want to replace the power regs with something more exotic. To replace the opamp you would need to build a small daughter board with a pin interface on the bottom and two sockets on the top. Alternately you could replace the opamp setup with your own discrete design.
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Old 2nd November 2006, 11:31 PM   #4
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Click the image to open in full size.

I will try to be precise since my English is not very good

1.- points white: caps blackgate FK 2200uf / 35v (before 1000uF 25v)
2.- point orange: cap Blackgate 1000uf / 16v (before 470uF 16v)
3.- points yellow: Opams AD826 (before OPA2604)
4.- points blue: caps blackgate 47uf / 25v (before 470uF 25v)
5.- points black: Auricaps 4.7uf / 200v (before 100uF 16v)
and removed muting transistors

I need suggestions and advice... thanks


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Old 23rd November 2006, 07:20 PM   #5
Amal is offline Amal  Canada
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Default NAD CDP - how to remove the musting transistors

just wondering if anyone could explain in detail how to remove the musting transistors - thanks
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