Mod/upgrade NAD C 541i

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10uF Clarity caps are large! They could just fit into the chasis.

I used 2.2uF only. By increasing the resistor after the coupling cap you could have a very low corner frequency without ill effect. The increased noise is so small that it can be totally ignored.

I can't remember what that resistor value from my memory, but if you use 10uF then as long as the resistor is greater than 10k it should be fine. It would not cause loss of bass.

Seriously, I would increase the bypass capacitors so that the power supply can have a lower impedance at lower frequencies. This may help increase the bass response.
 
No USE

Done the modification as mentioned below to my NADc542 but of no use..Now it doesnt read some other discs too.. :bawling:

Aparently the following has to be done in c542:

1. Change resistor R227 from 100R to a jumper wire.
2. Change resistor R103 and R104 from 20K to 15K.
3. Change resistor R218 from 15K to 47K.
4. Change capacitor C221 from 0.1uF to 3900 pF.

the resistors 103 and 104 in my C542 is not 20k.
its colour band has.. brown ,black ,black,black ,brown

Can some one send me the c542 Sevice mnual to

saravanan.cn@gmail.com


Thanks
saran
 
Done the Mods with NAD c352

janusz,

found out the mistake, had replaced some other resistor,
Now I have done the mods properly as per your sugesstion .

The cd player is reading all the discs even the one that I compile from my PC :D .


Trying to do the same in my friends NAD c541i. Need service manual Can any one send me the manual for c541i :)

Saravanan.cn@gmail.com

Thanks in advance
saran
 
kelly said:
What is the purpose of R375(R376) and R379(R380) in the NAD 542?

If the muting transistors are removed, can these resistors be removed?

Why are there two muting transistors per channel?


As far as I know the resistors are included to make the output more tolerant to capacitance in different signal cables.

Probably it is best to keep these resistors even if you remove the transistors.

I do not know the purpose of the two-transistor construction.
 
kelly said:
What is the purpose of R375(R376) and R379(R380) in the NAD 542?

If the muting transistors are removed, can these resistors be removed?

Why are there two muting transistors per channel?
I haven't looked at this particular schematic, and am assuming these are fairly low value (100 ohms or so?), but I thought these were there to prevent the output devices from seeing a dead short when muted?
I also don't know for sure why they always seem to use a pair of transistors, unless a single transistor still provides its Vbe drop to the output and using them in pairs gives more complete muting?
 
The resistors are 75 ohms. Having one makes sense to keep the opamp from seeing a dead short, although it is internally short circuit protected. I would not see that the input to the next stage would care if it sees a dead short. I always short unused inputs with no problems so far .

I did read something about using more than one transistor to get the required muting level and also about using the resistors to stabilize the outputs to capacitive loads, but I do not fully understand either, hence my question.

Thanks for the input.
 
I know that is an old topic...
But i'm starting doing some mods on my Nad C520.
I changed the OP chips, the in and out cap of the amp stage, and i would like to change the 1N4001 diodes.I would like to use schottky diodes, i found 11DQ10 which should do the job quite well, i read in the topic also byw200 and SB300 could do the job...
Can also the 1N5819 work?
Because i can hardly find the other types of diodes...Any good substitute?
thanks a lot for your help,

Crim
 
Dear fellow tweakers,

Reading all the positive results with all your tweaks I wanted to share my own experience.
Although this tread is based on the NAD54x series I have an older NAD 524(i). The NAD 524i is an improved version by the Dutch distributor bought in 1998 for 1300 HFL = approx 600 EUR. What they did is using a standard 524 - costing 1000 HFL - and replace the Op-Amps for better types ( the "bastards" removed the text on top so you do not know what they have used ) and they also replaced the parallel coupling caps from 0,22 uF to WIMA 2,2 uF MKT. The main coupling caps are 100 uF Elna but no specific type.
The standard RCA plugs were also replaced by gold-plated heavy duty models.

Since I have much better speakers I realised there would be much room for improvement in the CD / Amp area.
The NAD distributor will supply a copy of any service manual for 15 EUR each so I ordered for the CD player and Amplifier (NAD 317) which really helps if you need to tweak.

Earlier this year I already installed an Euro connector to be able to use better mains cables instead of the standard pre-mounted wire + plug.

Starting with the cd player I decided to install a Tentlabs XO2.2 clock. Because I overlooked the installation guid on the Tentlabs site I started to search on the internet and I happened to find the site of the Autralian brand Burson Audio.
In the weeks before I also had read lots about Op-Amps which were also on my to-do list and so I found the Burson discrete Op-Amp so I realised the potential here.
I ordered a set and last week I installed the XO2.2 clock, discrete Op-Amps and replaced the Elna's for the Silmic II types. I was really amazed about the result.

A friend replaced his Marantz SA11-S1 for a Spectral cd-player some months ago and then I had the opportunity to try his Marantz for a weekend but the difference was not that big to my ears.
Now that I upgraded my NAD I could notice the difference immediately but unfortunately I can not borrow the Marantz anymore to do a new comparison. But I am sure it will blow the Marantz away... which is an expensive cd-player !!

I am also planning to replace the rectifier diodes (Skottky) and power supply capacitors. The 5Vdc that feeds the analog section of the PCM1716 DAC chip is from an 7805 whicch itself is supplied by the 12Vdc (LM317/337) for the analog section. I will replace this 7805 by a LM317 too becuase of the lower noice.
And the muting transistor in the output will go too.

The clock and Opp-Amps are responsible for maybe 80% of the upgrade but the other tweaks are inexpensive so I will continue although the results won't be as shocking as last weekend ;-)

When completely finished next week I will make some pictures for those interested.
 
Maybe a bit late ... I didn't even remeber I posted here but as described above I would post some pictures ;-)

Grotefoto-VIA6NF8O.jpg
 
Mod 541i

Sorry to bring back an old topic...

Was about to trash my old 541i since it had a broken laser + cd pulley belt. But then found this thread and thought I might as well bring it back to life.

After fixing the player have done the following mods:

removed muting caps
soldered sockets for opamps and changed them to 627AU
changed main caps to panasonic ones as per suggestions in this thread

Next I'll do the fixes correcting the reading problems. But I'd really like to try the 541i -> 542 convert and remove the output caps. There was one post here describing the process but being a total newbie at this I can't make out exactly what to do. Here's the quote from user clocknad:

It lool like it is a very simple convert from C541i to 542, by moving stuff around - the 4k7 resistors from mute transistors move up to pin 5 and 6 of the first opamp, adding a 10K between Gnd and after C376, short pin 6 (with 4k7 between) to Agnd, connect pin 5 with DAC out after C376(4k7 in between)

add another resistor 270k parallel with R360 to drop it down to 15k2. remove those coupling cap after the opamp output. NO trace cut needed, and that is the difference between 541i and 542 in the analog section.

Could someone please open the process up for me in detail? I'd really appreciate the help!

Really liking all the improvements in sound so far! Thanks to all the contributors in this thread! :up:
 
Way too late reply to the subject. But.... if anyone still fiddling around with this player, here is the "final solution":
The core of all reading problems with this player, is the power supply.
The raw DC feeding the servo and digital processing circuits is too low, boedering the fallout voltage of the 7808 regulator. This is why sometimes the relay is clicking during TOC readout, and also makes the operation of the servo circuits unstable. By replacing the four rectifier diodes with Schottky types (D514-517 - to 1N5819, or similar) you gain around +0.6V raw voltage for the stabilizer IC, and voilá, problem solved... This might require a little more cooling for this IC, so it is advisable to replace the heatsink with a taller one.
 
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