Coupling caps output cd player.

Hi, I have a SA15s1 Marantz CD player. I have done a «Lampizator mode «, take signal right from the dac and right to the RCA output. Right before the RCA there is a coupling cap ( 3.9uf ). The preamp have 50k impedance. What do you think about the cap valiu?
 
It's ok, you could go as low as 0.47 uF imo with 50k preamp impedance.

And also you can avoid the dc coupling cap if the Pre already has a shematic with a DC coupling cap in serie at its input. But I will keep a cap in the cd player to avoid any short of the dac chip output.

In some shematic you can have in serie at the output of your cd player a serie resistor for the voltage impedance adaptation with the load or to avoid some oscillation, there never is a component in a pcb by chance. And also a resistor between the pcb ground and the RCA ground (return signal path) you can deplug at one side if using direct coupling without cap (what I don't advise though, better keeping the protection cap)
 
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There isn't just the frequency response roll-off in the LF to consider, also there could be a noise penalty in the bass too, depending on the pre-amp. If the pre input stage is JFET or valve then the additional noise is likely negligible as there's no input current to speak of. With a BJT input stage though, noise current is likely an issue with too small a cap.
 
Hmm I thought the DAC has output filters to remove digital noise shaped further up the spectrum. Also the output buffer to not put too much load on the DAC thus keeping the frequency response stable. I thought that a cap too large and the poor DAC has to swing a large charge causing issues.

I thought about hacking two balanced outputs into my 25yo 1-bit CD player and taking the balanced output straight off the DAC itself. It may be easier simply getting a DAC card and adding that onto the SPDIF and using that differential output. There's space in the player for a small card too 🙂
 
NickKUK: Lampizator say that the board after dac is there so the manifacture is guarding himself 100% not to damage or make problem for item after say in my case the CD player. But the board does only bad for signal/ sound.
 
There isn't just the frequency response roll-off in the LF to consider, also there could be a noise penalty in the bass too, depending on the pre-amp. If the pre input stage is JFET or valve then the additional noise is likely negligible as there's no input current to speak of. With a BJT input stage though, noise current is likely an issue with too small a cap.

Definitely, thanks for pointing this out. A fact that is easily overlooked.
 
NickKUK: Lampizator say
And WHO IS|"Lampizator?
Just checked their site.
I have seen worse, but they definitely belong to the namedropping magic properties components Club, including questionable opinion just on the first page.
Snake oilish, etc. , including classic "Op Amps sound BAD" (guess how many dozens Op Amps the Music you are listening to went through at the Recording Studio 🙄)
And they prominently display Mundorf, Audyn, Auricap and Jensen caps, with pure copper foil, silver terminals, etc.
I am certain THAT will add details which were not there before 🙄
that the board after dac is there so the manifacture is guarding himself 100% not to damage or make problem for item after say in my case the CD player.
It does a little more than that, and much needed stuff, that´s why I called removing it "lobotomizing" your DAC
As in:

lobotomize
/ləˈbɒtəmʌɪz/
Learn to pronounce
verb
gerund or present participle: lobotomizing

Surgery
perform a lobotomy on.
"her brother had developed a schizophrenic illness and had been lobotomized"
informal
make (someone) less able to function
mentally or emotionally.
"couples we knew who had been lobotomized by the birth of their children"
But the board does only bad for signal/ sound.
Yes, Lampizator often says such nonsense.

You just removed an important part from your DAC and have the DAC core itself do a duty it does not expect.
 
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JMFahey: Yes i know the op amp 5532 has been in many recordings. When we speak of good capacitors we dont talk just of it add something that is better then the oem signal, we are talking about components that does litle or no harm to signal so we THEN get hearing what was made on records.
 
Johnmath: can you show me how you calculate. I want to learn.
I use an online filter calculator like this one: Filter Design and Analysis

If you know the frequency you want, then you can try guesses for the R and C and adjust until you get the right Fc.

One thing to remeber is getting the units correct. The calculator uses Henries, Ohms and Farads so you need to add the decimal places or zeros. 1mH= 0.001H, 1µF 0.000001F and 1kΩ = 1000Ω, etc.
 
Johnmath: can you show me how you calculate. I want to learn.
I use an online filter calculator like this one: Filter Design and Analysis

This one is for calculating Fc (the nominal corner or cut-off frequency), but if you know the frequency you want, then you can try guesses for the R and C and adjust until you get the right Fc.

One thing to remember is getting the units correct. The calculator uses Henries, Ohms and Farads so you need to add the decimal places or zeros. 1mH= 0.001H, 1µF 0.000001F and 1kΩ = 1000Ω, etc.
 
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