Rotel RCD-965BX CD Player,Worthwhile mods?

[fergs1]

Greetings Ladies and Gentlemen,
I have a Rotel RCD-965BX CD Player which I will be using an external dac(monica 2) and was wondering is it worthwhile putting any money into it as a transport and if so what mods are worthwhile. I'll only consider diy mods as I'm a cheapskate. What are your opinions of using the Rotel RCD-965BX CD Player as a transport. thanks in advance
cheers fergs

[Fin]

The build quality of the case is good compared to other budget CD player - so it has potential. The mechanism is a very reliable Philips CDM4/19 - a reasonable swingarm based mechanism - but not the best of its type.

The weak point of ths CDM is the motor which uses brushes....as opposed to a Hall Effect motor found in CDM2 and some better CDM4s. However, much of the HF noise produced by this type of motor can be reduced by adding a few small caps across the motor's power terminals. This should improve it as a transport and as a CDP.


OK - so if you are sure that you only want to use it as a transport....then there are a few things you can do which would also benefit its performance as a CDP - but might not fit if you want to keep all of its functionality.

You can disconnect and disable all circuits that will not be used. This will allow you to optimise the power supply for the CDM and Dig. Out.

In a thread here on improving the CD723, Thorsten Loesch (KYW) recommends an optimised PS for the servos for the CDM. He suggests : Schottky diodes, small resistor (.33 ohm), 10,000uF cap, Regulator, 10,000uF cap......

The next area to improve is the quality of the SPDIF output. You might consider reclocking this and improving the output transformer.

You could also save yourself a lot of trouble and jitter by placing the TDA1543/5 dac inside the case of the Rotel....and feed it derectly from the I2S from the decoder. This way you don't need another case for the dac, no SPDIF problems, no receiver chip required and you could even use the existing internal PS of the Rotel.

[tubenut]

And if I remember correctly the Analogue outs are on a little separate PCB with fly leads to main pcb, you could remove this pcb and no need to drill more holes if you fit DAC inside.
If not and used as trransport have a look at digital out implementation, there is a a switch to disable it in the RCA not sure if it switches logic on main board or signal, wire could be improved as well. Doubt the stuff inside is even 75 ohms.
The switch is to reduce interference in analogue mode but I feel the wiring route and quality would hamper the dig out performance.

[tubenut]

Oh, Fin, what should the value and type be of those brushed DC motor supressor caps then?

[Fin]

Originally posted by tubenut
Oh, Fin, what should the value and type be of those brushed DC motor supressor caps then?

Hahaha.....you caught me out.......I have no idea.....but I've been trying to find out. The people who have the equipment to measure and find out won't tell us. I first heard about this from Bernhard but he didn't tell us exactly how to do it. I was hoping that someone would come along and enlighten me as well.

It is probably something like 100nF...at a guess.


BTW - the Rotel RCD965BX is a nice machine, so make sure you really want to sacrifice it before doing all if this stuff to it.

[fergs1]

greetings and thanks for all your replies, I was just thinking that bypassing reciever chipp is not possible as the monica dac uses a differnt format to 12s as it uses the 1545a chip.I'll let this thread float a bit longer to see what other ideas come forth before attempting anything
cheers fergs

[Fin]

I think you can stick the non A chip or a 1543 in there too.....but check with Yeo.

[johnm]

Hi!

Any further information on what value cap(s) to use across the CDM4/19s motor to reduce HF noise? I'd like to try this mod myself.

Many thanks.

- John

[Fin]

Originally posted by tubenut
Oh, Fin, what should the value and type be of those brushed DC motor supressor caps then?

Originally posted by johnm
Hi!

Any further information on what value cap(s) to use across the CDM4/19s motor to reduce HF noise? I'd like to try this mod myself.

Many thanks.

- John

Here is some info from someone who tried it on a Sony mechanism - also with a Mabuchi motor:-
Tweaking: Bypassing spindle motor with caps: Yay or Nay?

[jnewbold]

I have read all the posts about RCD965, and the SAA7323 bitstream DAC and the QE digit and searched for specific information about this question.

I have removed the muting transistors in my RCD965BX and have been wondering about removing the remainder of the parts after the DC blocking caps. (see copy of schematic attached)

I know that the QED digit uses the same SAA7323 DAC chip and just uses a 4700pf polystyrene after the op-amp and DC blocking cap to roll of the highs a little.

Would it bring any benefit to remove the series resisters and other network components between the DC cap and the output, and replace it all with with a 4700pf polystyrene as in Digit.

Or is there something better to do with the section after the DC cap?