Tweak report NAD 510

I tweaked my NAD 510 some days ago, and the results are great! The 510 is a little bit picky, reading some CD's, compared to my NAD 541i.

What I modified:

- parallel to every diode 0,1uF MKP under the board
- replaced the 5532 by OPA2134
- replaced the bypass caps nearby the opamps by MKP types
- bypassed the output cap and transistors by a direct wire from the last 2134 outputs to the output jack.

I am looking for a service manual for the 541i. My version is already modified by the importer (Rowen). Some caps are replaced by MKP types, the opamps seems to be some BB types, but silver painted to hide the exact type (look picture).

Kind regards


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my NAD 541i is the "Rowen Edition", modified by the swiss importer. They changed opamps and some caps.

When I bought it, I compared it to the standard edition and it was no question for me, to pay 66 Euro more (at this time, I did not modify things without tubes) :)

But, maybe, now I could try to tweak it a little bit more...

I made some mods to a 541i some time ago. As far as I can see from the picture Rowen didn't change too much. So there's room for more;)

Do you remember the differencies in sound between original model and "Rowen Edition"?

I don't remember in detail my modds but I've added a kwack clock, removed the muting transistors and output caps, and i think the opamps that stayed inside at end were AD826.

email me and get the manual:)

more tweaking

I continued, tweaking my NAD510 and up to now, I am quite happy with the result.

Soon, I will compare it to the NAD41i "Gysi Edition" :D

What I did:

- add a RF filter at the mains input
- add an additional tranny, specially for the DAC and audio-board

The new tranny gives 19-0-19VAC instead of the original 17-0-17VAC. This difference seems not to be a problem, the regulators don't get hot (for some reason, the original heathsink at the LM7915 was missing. I got the player second hand).


BTW: How good are the SAA7350GP DAC's compared to others?


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Here a picture from the mods on the upperside of the board.

Additional to my first posting I changed two electrolytic caps nearby the last opamp.

And I replaced the output wire from the output opamps to the connectors by 82 Ohm resistors to minimize possible problems with capacitive loads.



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And here, the cupperside from the board:

Bypassing the diodes to avoid switching noise. Bypassing the charging caps with some MKP's.

For the voltage regulators input- and output-caps, as described in the according datasheet.


next step: tweaking the transport unit. I could not figure out, up to now, how to remove the transport unit from the chassis :bawling:


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After comparing the modified NAD510 to my NAD541i with my "big chain" (PL519 SE, Coral Beta8 in backloaded Horns), I remarked that the result was far away from my goal:

Grainy sound, missing mids :bawling:

So, I worked again: nearby all caps and electrolytics are replaced now by better types.

I realized, the two 2200uF before the regulator where 25V types running now with 27VDC :att'n: I changed them by 35V types.

And I realized, that the whole amp was dc-coupled and measured about 50mV bias at the output.

So, I inserted two 2.2uF MKP caps (out of my hobbybox). This is still resulting in an acceptable roll off from 4.2Hz with my 50k amp input Z.

Now, the player sounds very good.


BTW: In the meantime, I found access to the screws to remove the (Philips) transport :)


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Thanks, I found those screws. I coud not found digital receiver chip on the board under transport section. Do you maybe know (in NAD 510), if the signal is oversempled and digitaly filtered at the point where it comes to the DAC board.
I can tell that NAD 510 works with TDA 1543A (Japanese format) and it works verry good (nice analog-like sound). This is very simple and eficient tweak.
There is a picture of Prosonic CDP with TDA1543A DAC.



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