Marantz CD-7 audio output mod.

[D.A.R.R.Y.L.]

Hi All,
Having succesfully modified the output of my denon 2900 with two Mundorf Supreme Silver/oil 1µF'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 1µF 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 220µF caps? Will a 1µF (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!!

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An externally hosted image should be here but it was not working when we last tested it.

 

[jean-paul]

Will a 1µF (Mundorf Supreme Silver/oil) as a replacement be able to also remove this dc component?

Yes.

Or will any cap remove this component?

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

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.]

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.]

Hi Tom,

Thanks for your advise Jean Paul!

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

 

[jean-paul]

My mailbox can handle that

 

[D.A.R.R.Y.L.]

And your e-mail is?

 

[jean-paul]

I have sent you a PM....

 

[D.A.R.R.Y.L.]

Jean Paul,

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

 

[jean-paul]

Not really if you don't short things.

 

[D.A.R.R.Y.L.]

Ok thanks I will give it a go.

Regrads,
Ramon

 

[D.A.R.R.Y.L.]

I started the modding!
I removed two caps in the rca output line, c604 and c605 and put a Dayton MKP 7,5µF in on one side. When set to mono I can already hear a big difference in clarity and detail.

I tried rca first, not to fry my true balanced part of my cd-7.

Now for my question:
There is no dc component in the rca output line.
But as I already mentioned I measured 0,431 Volt DC over the two 220µF el.caps. Does this DC definitely need to be removed? Or does it serve a purpose in the true balanced design?
I calculated for f3 with 76,7Kohm a value of 0,22µF.
This is handy because I have some very nice paper/oil caps NOS from Westcap laying around.

Will this provide any problems? Changing the two 220µF el.caps for this one 0,22µF paper in oil?

 

[jean-paul]

Paper in oil caps in a CD7 !?

Nothing is sacred.

 

[jean-paul]

Remember that the formulas output is the -3 dB point. So the frequency rolloff is starting earlier.

0.22 uF seems inappropriate, from calculation and from experience.

The 0,431 Volt DC over the two 220µF el.caps does need to be removed. If they could have been left out, Marantz would have done that wouldn't you think ?

 

[D.A.R.R.Y.L.]

Sure, I agree.
But will say 1µF remove this also?
Isn't the 2x220µF intended for worst case when some hooks up an amp with very low impedance?

 

[D.A.R.R.Y.L.]

PS 1 cap gives a rolloff of 6dB/octaaf isn't it?
So when I have 9Hz -3dB then roloff should commence @ 18-4,5Hz = 13,5Hz. I have no problem with this rolloff. Or do you find 0,22µF to low a value in other respect?

I will not kill the cd player by putting in this value, would you reckon?

 

[jean-paul]

Leave it like it is after you've soldered both Dayton caps as you seem unsure. CD7 is already a great cdplayer in its current setup and after adding a low jitter clock probably only the last 5% in improving its sound quality is left.

Please practise modding and changing cap values on a budget cdplayer which is not a big loss if you make a mistake. If you are unsure and do not know the basics in electronics ( no offence intended ) you better start gathering knowledge on a basic cdplayer. You will learn from your mistakes and you'll be able to mod the CD7 the right way when you're more experienced.

 

[D.A.R.R.Y.L.]

I use the XLR not the rca.

How is one to learn if the knowledgable aren't willing to help.
I already practiced on the Denon 2900 with great results.

My only question is, if there is a specific reason for the 2x220 in the balanced output? And if replacing these with a lower non-polar version, say 1 µF, will they not function in this setup.
I know it will in the rca line, but will it be sufficient to kill the dc component of 0,431 volt?

No book will tell me, you guys can. Because you now a lot in this specific department.

Or is everybody dodging the answer, thinking I will curse you for it when I blow it?

 

[jean-paul]

How is one to learn if the knowledgable aren't willing to help.

I beg your pardon ?

 

[D.A.R.R.Y.L.]

Sorry,

Did I offend you? Didn't mean to.

I mean that I know my basics and already modded the denon 2900 to great avail. Not being to familiar with true balanced designs, I was only inquiring about this high voltage component and it's 'possible use' in this design.

That's all.

 

[Peter Daniel]

I use the XLR not the rca.

How is one to learn if the knowledgable aren't willing to help.
I already practiced on the Denon 2900 with great results.

My only question is, if there is a specific reason for the 2x220 in the balanced output? And if replacing these with a lower non-polar version, say 1 µF, will they not function in this setup.
I know it will in the rca line, but will it be sufficient to kill the dc component of 0,431 volt?

No book will tell me, you guys can. Because you now a lot in this specific department.

Or is everybody dodging the answer, thinking I will curse you for it when I blow it?

There is a trend for using large caps in output coupling but they are not always neccessary. Depending on the input of your preamp, even 1uF may work well. The size of the cap has nothing to do with the offset value, any cap will block offset.

If you want to try 1uF go ahead and see if it sounds well, if it doesn't, try something else.

In my DAC I'm using 0.1uF V-Cap for output coupling and the bass performance is very good (the preamp's input has at least 100k impedance).