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-   -   Marantz CD-7 audio output mod. (http://www.diyaudio.com/forums/digital-source/71981-marantz-cd-7-audio-output-mod.html)

D.A.R.R.Y.L. 17th January 2006 09:29 PM

Marantz CD-7 audio output mod.
 
Hi All,
Having succesfully modified the output of my denon 2900 with two Mundorf Supreme Silver/oil 1F's I am willing to try to mod the output of my Marantz CD-7 also.

The cd-7 already has a Tent XO2 with XO supply, but I love what the cap change on the denon did, so I am willing to try it on the cd-7.

Included are the schematics of the parts concerned with modding the output of the CD-7.
From the HDAM (Marantz opamps) the signal, we take left channel as a guide, passes through R718 and then through the Elna's I want to replace, through relay L702 and then straight to the XLR connector.

I can not remove the caps and replace them with a wire, as I measured 0,5volt DC over these caps. So they definitely serve a purpose as to remove the dc component.

I was handed a formula to calculate the actual value needed for the replace cap, dictated by the lower cutt-of freq needed (in the order of 5 Hz) and the input impedance of the amplifier connected.

For the denon 2900 I calculated that 1F would suffice due to the extreem high impedance of my Electrocompaniet ECI-4 of 330 Kohm.

Can I do the same for my xlr connected CD-7 to the same amp, or should I be concerned with the dc component of 0,5 volt over the two 220F caps? Will a 1F (Mundorf Supreme Silver/oil) as a replacement be able to also remove this dc component? Or will any cap remove this component? Or is there a formula for which cap value removes what dc component?

Thanks a lot!!
http://home.versatel.nl/marantz/cd-7...c-coupling.jpg
http://home.versatel.nl/marantz/cd-7...muting_xlr.jpg
http://home.versatel.nl/marantz/cd-7...output_pcb.jpg

jean-paul 17th January 2006 10:39 PM

Re: Marantz CD-7 audio output mod.
 
Quote:

Originally posted by D.A.R.R.Y.L.
Will a 1F (Mundorf Supreme Silver/oil) as a replacement be able to also remove this dc component?
Yes.

Quote:

Originally posted by D.A.R.R.Y.L.
Or will any cap remove this component?

Yes.Some have more leakage than others. Electrolytics are the worst for this purpose ( in general ).

Quote:

Originally posted by D.A.R.R.Y.L.
Or is there a formula for which cap value removes what dc component?
No.



Please do not forget R720 in your calculations for the correct value for the capacitor.

f=1/(2xPixRxC). This is the -3dB point. So 100k parallel with the amps 330k = 76,7 kOhm

1/ ( 2 x 3,14 x 76.000 x 1exp10-6 ) = 2 Herz

X.G. 18th January 2006 12:32 AM

hi, D.A.R.R.Y.L.

could you share me the schematic and PCB layout papers of CD7?

thanks a lot.my email box is jmxg007@tom.com

X.G.

D.A.R.R.Y.L. 18th January 2006 09:14 AM

Hi Tom,

Thanks for your advise Jean Paul!

It is 6mb in size, can your mailbox handle this?

jean-paul 18th January 2006 09:29 AM

My mailbox can handle that ;)

D.A.R.R.Y.L. 18th January 2006 09:31 AM

And your e-mail is?

jean-paul 18th January 2006 09:40 AM

I have sent you a PM....

D.A.R.R.Y.L. 18th January 2006 11:29 AM

Jean Paul,

is there any danger in changing the output with regards to killing a HDAM?

jean-paul 18th January 2006 12:18 PM

Not really if you don't short things.

D.A.R.R.Y.L. 18th January 2006 08:17 PM

Ok thanks I will give it a go.

Regrads,
Ramon


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