CD67SE mods - where do I go from here?

[dantwomey]

This is an exercise in myself thinking out loud and soliciting any comments from veteran DIYers.

My CD67SE has had the following done to it:

- Some LC Audio AD8065 opamps
- Kwak clock v7
- Cabinet dampening
- Nichicon FX 4700uf/63v Muse caps where C803, C804, C805 and C806 use to be. These caps were all bypassed with some Wima 22nF/63v electroytics.
- PS diodes D801-D804 and D811-D812 replaced with Hexfred soft recovery diodes.
- Output caps C655, C656, C657, and C658 were removed and replaced with a jumper.
- The muting transistors QN05, QN06, QN07, and QN08 are removed.

Waiting in the wings is:
- An IEC power socket
- A pair of Cardas RCA jacks
- enough caps to do the following:

The Circuit-board denominators are CD21, CD22, CD23, CD24 (120pF); C605, C606(1000pF) and C607, C608 (100pF). I did replace them all with Philips 1% Polystyrene Capacitors.

Looking at the analog Filter in Pspice, I noticed that the Filter has slight "bump" in the upper treble. While this is small, I had a look around how to change this, as I felt that CD-Player was too bright anyway. Replacing C607 and C608 with a slightly larger value unit will help. I used 150pF (again 1% Philips), but up to 220pF seem workable. Try out various values for Your desired result. With 150pF the -3db Point of the Filter is changed to about 30kHz from 40kHz in the original Version

The two excellent resources I've come across so far are
Thorsten Loesch's excellent CD67 website and an AudioAsylum post by Bob Noriega .

What have the mods done to date? I have excellent musical detail and clarity. I can hear every breath the singer takes and every subtle touch of any strings. There is a great sense of definition between various voices and instruments. As far as detail and clarity go I feel no need to go any further.

So what do I seek now? I currently find the sound a bit sharp and edgey. I suppose the dragon I'm chasing now is the often mentioned sibilance. But, hand in hand with the elimination of sibilance is something else I seek. I'm also after alittle less clinical sound. Alittle more warmth and smoothness. I have all the detail and clarity I could want but it is cold and stark.

The primary reason I'm now taking some time to contemplate my next move is that my most recent upgrade, the Nichicon Muse caps and Hexfred diodes, didn't make any easily noticed difference in the sound. So now I'm treading forward carefully. I don't want to invest in mods that offer no appreciable gain. And, I
would like to achieve the goals mentioned in the preceding paragraph. Hmmmmmmm.... time for some more thought and reading.

Comments anyone?

Regards,
Dan

[Zombie]

Hello!
See the recent discussion here about CD63 mods.
Pedja called for caution when executing some of the Bobwire mods.
I recommend to match the 10k and 27k resistors before the first opamp after the DAC within 0,1%. For me (but not for everybody) it made a huge difference.
Have you thought about adding coax in some vital signal paths?
Btw, if you do a search here on CD63 or CD6000, you will find a lot...
Cheers,
Tom

[Spartacus]

Hi Dan,

you may want to look here for more information:

http://www.acoustica.org.uk/

I'd suggest focusing on cleaning up noise from the digital section as well as the DAC's 5V rail which I've read is very noisy.

Hope this helps!

[dantwomey]

As far as cleaning up the 5v volt supply goes, I'm at somewhat of a loss. I don't want to go to the expense of putting super regulators in like ALW's. But, I would like to improve this supply. Thorsten suggests replacing the 7805 with a LM340T5. I have two questions about this. Would it be a direct swap? And, would it be an improvement?

Regards,
Dan

[Zombie]

Looks like they are...In GND Out
If not, you can always use a veroboard and set it up there...all caps etc...
Isn't LT1086 better? But it's not pin compatible...there are only +V versions, though, so it can't be used for the +/- 12V

T

[wojtek.l]

Zombie - what`s Your list of the best mods in Marantz (after listen) ?
I think, that the best mods it`s build new DAC

[Zombie]

Hello Wojtek!
Maybe you're right about the DAC, have you any recommendations? What mods did you do to your player before building a new DAC?

Anyway, I'm not an expert or equipped with golden ears, but here's my Top 5 IMHO:
1. shorting out the output caps
2. the acoustica.org.uk clock mod
3. the matching of the 10k, 27k resistors before the diff.amp at the DAC
4. putting in better opamps
5. filling the damn thing with lots of bitumen and blue tac

Wonder how much improvement cleaning up the 5V and +/-12V, shielding out RF and using coax might give?

Cheers,
T

[Spartacus]

Originally posted by dantwomey
As far as cleaning up the 5v volt supply goes, I'm at somewhat of a loss. I don't want to go to the expense of putting super regulators in like ALW's. But, I would like to improve this supply. Thorsten suggests replacing the 7805 with a LM340T5. I have two questions about this. Would it be a direct swap? And, would it be an improvement?

Regards,
Dan

I would be very surprised if you noticed any reall difference with the lm340t5 regs. lm317 type devices are rather better though, as Zombie suggests. Another simple thing you could do would be to simply stick a 470-1000uF OsCon after the 5v reg - this would definately lower noise appreciably.

[wojtek.l]

Hi, Zombie
I don`t exchange any elements in my Marantz CD yet, but I schedule it to do.
I modified cd Technics only.
This is greate mods in Technics:
- new master clock,
- separate an cleaning voltage for DAC and other digital ciruit (4x7805) – very nice result – this is inspiration : http://zaudio.hotbox.ru/diy/articles/63.htm,
- remove muting transistors,
- beter caps. in signal path (WIMA MKT),
- beter op amps with bessel filtr.

After this mods I now that my Technics playing better but it isn`t greate equipment J.
My favourite links with dac for Marantz:

http://www.geocities.com/rjm003.geo/rjmaudio/diy.html
http://home.student.utwente.nl/f.s.b...io/nonoz2.html

http://www.dddac.de/ma_dac21.htm
http://www.diyparadise.com/rm20dac.html
http://diyparadise.com/8x1543dac.html

[Zombie]

Interesting stuff!
My Russian is more or less non-existent. Where are they putting the 7805 regs? Around the DAC? I have three separate LM337 regs to the DAC and clock.

I also replaced the big caps around the HDAM with the output caps I removed. A clear improvement of the sound. It has made me determined to try to clean up the 12V supply to the opamps and HDAM.
Cleaning up the rest of the 5V is also a priority, have already put a 0,1uF bypassed 220uF ELNA there instead of the 3300uF at the 7805.

Cheers,
Tom