Output cap on a CD player

[rabbitz]

I've got a Sony CDP990 I've had since 1990 and even though I've had newer players which have come and gone, this always returns to the rack as the sonics are very appealing.

I changed the output op amps from 5532's to OPA2134's which gave a nice improvement in overall detail and clarity. The original output caps (C406 in the schematic) are Elna Duorex II 47uF 63V and would like advise on whether to change these as they might be getting past their used by date. I'm leaving the rest of the player as original.

a. Change to Nichicon Muse Fine Gold 47uF 50V which I have.
b. Change to a MKT or MMK of 1uF???
c. Put in a link and have no cap but I can't always be sure the amplifier that comes next in the chain would have an input cap.
d. Leave the Elna's in there.

Any advise would be appreciated.

 

[dsavitsk]

a. Change to Nichicon Muse Fine Gold 47uF 50V which I have.
b. Change to a MKT or MMK of 1uF???

How about both of these? Put in the 47uF caps to get the proper rolloff frequency, and bypass it with a decent film cap for the sonic improvement. You could also pick up something like a solen film cap that is 47uF for about $13 if you don't like bypassing.

-d

 

[georgehifi]

Stick with one cap, if you can, as bypassing coupling caps causes as strange smearing where both caps are doing the same job but at different speeds because their internernals do things at different speeds. (it good to bypass power supplycaps)

I would say get a if staying with electrolytics get a NX black Gate bipolar 47uf x 6.3v the voltage should be enough
as I've rarely see offset voltages of over 1v 0n cd players so 6.3 should be ample just check what your getting now dc offset wise before the Nichicon.

Or if you can find them a big say 10uf no less polypropylene cap from Auricaps or Solen.

Cheers George

 

[baggystevo82]

What are you driving with it? Even with a low input impedance SS amp 1uF is likely to be plenty, opening up lots of potential film n foil caps. Might be worth checking the input of the preamp for coupling caps too, no point having two lots of caps...
Steve

 

[georgehifi]

I would stay above 10uf, if you ever try say a passive pre that commonly has sometimes a 10k input impedence your low frequency roll off will still be -3db at 1.5hz so it safe for all types of pre's, I've even seen active pre's with inputs of 10k so a minimum of 10uf is a safe bet.

Cheers George

 

[rabbitz]

What are you driving with it? Even with a low input impedance SS amp 1uF is likely to be plenty, opening up lots of potential film n foil caps. Might be worth checking the input of the preamp for coupling caps too, no point having two lots of caps...
Steve

The amp is an AKSA 55N+ with an input impedance of 47K. There's an active pre in between but still not finalised as I'm testing OPA134, OPA627, OPA2134 and different layouts.

I've had the Black Gate NX at the back of the mind and remember the excruciating burn in of 150 hours with the AKSA, but well worth it in the end.... Hugh's always right. With a CD not so bad as just leave it on repeat for a week. Could even try the cap rack again to do some pre burn in but no success with that method previously.

Thanks for the advice guys.

 

[georgehifi]

What have you measured as far as the dc offset goes, as the original ne5532 has dc offset that needs a dc blocking cap, but since you changed to OPA2134 these may be fet input ic's and if so may have very little dc offset, if so and they are giving say below 10mv of dc offset you may want to try having no cap at all (ie: dc coulped) and that sounds better than any cap, just do'nt turn your player on or off while the rest of the system is switched on or you may get swicthing thumps. Just leave it on all the time.

Cheers George

 

[rabbitz]

George

Needs a cap as the offset is 66mV (100mV specified in the service manual).

Tried the Nichicon Muse and did give a noticeable improvement to the dynamics so added to the improved detail and clarity from the OPA2134, it's worked well and A$18 all up.

I'm going to order some 47uF 6.3V BG NX from Hi Fi Collective and some STD BG for the op amp power caps. They're 470uF 35V at the moment but I'll get some 470uF 16V as it's only got 5V rails.

Thanks for all the advice.

 

[georgehifi]

So you say that now with the OPA2134 you have 66mv, if that's the case then you will need a blocking cap


Cheers George

 

[Gasho]

Change OPA2134 , with AD828 , than change all resistors in signal distribution with Riken or Dale RN60 , as output cap you can put Mundorf Mcap 3.3-4.7uF . This will be more than you need to 20Kohm input resistance of your amp.


What about power supply in your player. Did you change diodes in Greatz. In digital PS path try to put OsCon caps near DAC/Filter chips. Before that pull out all factori caps (electrolitic/tantal/ceramic).

 

[rabbitz]

Gasho

Thanks for the advice. This has only been a simple mod and mission accomplished as the player sounds extremely nice as original... just a little exercise for the analogue stage. I will give the AD828 a try as I can get those. Are the Mundorf M-Caps any good as I was looking at using them or Solens in a speaker crossover?

I'm keeping away from the digital circuit as it not my expertise.... speakers and amps, yes.... digital, no.

Cheers

 

[Gasho]

I think , from expirience that Mundorf is much better than Solen , even better than 80% of all other "audiophile" MKP caps on market.

 

[HiFiNutNut]

Rabbitz,

I have a stock NAD542i I want to modify but don't know where and how I can get the service manual or schematic. How did you get yours?

Regards,
Bill

 

[rabbitz]

Got mine from here.

http://www.manualscenter.com/

They are in Poland.... you pay your money by credit card or Paypal, US$14.99, and within 24 hours you get an email with a link for the download. 8Mb or so later, viola.

Hope this helps.

Just checked and couldn't find any NAD on there. This is a place in NJ USA that I can't remember that sells paper copies of service manuals for US17.99.

 

[Leolabs]

I will take away the output caps and the muting transistors,just if i dont mine about the on/off click or pop sound.

 

[kevinkr]

I second doing away with the muting transistors, if you need muting and I did, just use one of the those muting transistors to drive a relay.
(Short output to ground, contacts not in series with signal.)

You might not need the coupling capacitor at all, you could null the offset or even ignore it if it is below 100mV provided that the power amplifier is ac coupled. 100mV dc is about the limit on the element of a typical volume control pot to avoid brush noise. (scratchy noise as control is moved about.)

I had a very similar sony cdp, it might have even been the same model but I gave it away a couple of years ago and can't remember. I converted output circuit to tubes. The dacs were analog devices 18 bit pcm types (AD1860) with current output option. I used 10 ohm resistors for I/V conversion and a couple of triodes for gain. Sounded very good.

Note Sowter makes a little transformer which with a resistor on the primary of the transformer (or larger one on secondary) makes a good I/V converter. I have heard it with my own ears. No active circuitry and the transformer takes care of any minor dc issues as well.

 

[rabbitz]

It seems it was only the US players that had the AD1860 with the rest of the world using a Sony chip looking at the schematics.

The muting transistors are also different as they do appear to drive a relay that's in the non US model.

There's no guarantee what this is used with and if with one of my GC's could be a problem without the coupling cap.... I'm playing it safe and conservative. As it stands with this setup, it will be going directly to the volume pot in the pre amp before any active stage.

Thanks for the tips.... much appreciated.