Is Your CD Player/Changer Too 'Hot'?

Ok, so my DAC puts out 2.25vRMS, no variable output. What (if any) attenuation would be wise running into the average AUX or Tape input on a vintage pre/integrated?

 

I don't have a separate pre-amp, and inside my JVC receiver aren't too many of what look like what's in that phono-pre.

 

Even if your CD peaks come to within no less than -5dBfs(digital full scale), that massive CD player output going into the input stage of your receiver could still shave as much as 6dB off them.

Which overloads and fatigues another component in the listening chain with the burden of subconsciously filling in all those clipped waveforms:


your brain.

 

On a preamp *with* gain knobs? No(as in redundant).

On an integrated? Yes.

 

Well Shiver me timbers !

I gotta do somethin' !!!!!!!!!!!

 

My Oppo 105 player lists:
Output Level: 2.1 Vrms (RCA) or 4.2 Vrms (XLR) at 0dBFS

What does Vrms mean?

My NAD C160 preamp inputs are:
"Input Sensitivity ref. 0.5V 150mV"

What does that mean?

Both the Oppo and NAD have variable outputs.

 

Vrms means volts RMS(average, not peak).


If the Oppo CD player has variable outputs, you could source a 1Khz sine full scale tone on CD and set your outputs to 0.5V per channel with a volt meter the way I did, or, turn down the sensitivity on the Pre-amp(which might be better as it allows the CD to remain at full output, overcoming any resistance in the cables connecting it to your pre-amp.


Do not under any circumstances use the xlr outs of that CD player unless you are connecting them to the desk in a PA system.

 

V means volts. RMS means "root mean square" and it's actually referring to continuous average power. Many, many digital players (DAC, CD, DVD) have around 2.0 volts of output, so yours is normal.

"Ref. 0.5V" is the reference voltage the sensitivity is being measured against. The number you're interested in here is the 150mV; that's the line input sensitivity of your preamp. That also seems to be common in current preamps/amps.

The mismatch between the two is the topic of this thread:

Oppo (2.1 V) output = 14 times greater than the NAD's input sensitivity (.15 V). So you'd want to crank down the variable output on the Oppo, probably.

 

This afternoon I assembled a combination of components I had not tried before: Accuphase E-202 integrated, Magnum Dynalab tuner, Denon DCD 1520 (as transport), CIAudio VDA-2 DAC (with VAC-1 PS) and Reference 3A mm de Capo speakers. A few hours of listening with the tuner and all sounded better than expected. I went to CD and put on the Joshua Bell 'West Side Story' recording. It starts out softly and then shortly in the first track suddenly gets quite loud. Plenty of distortion briefly. With gain set for the quieter passages (about 9 o'clock) the loudest get rather distorted.Output from the DAC is 2.25v, input sensitivity of the line input on the Accuphase is 160mv. Overloaded input?

 

Classic example, thanks for sharing.

If inputs are not adjustable on that integrated amp, pads will help. There is a link to a calculator somewhere in this thread - I cannot seem to find it online.

 

Classic example, thanks for sharing.

If inputs are not adjustable on that integrated amp, pads will help. There is a link to a calculator somewhere in this thread - I cannot seem to find it online.

 

Is this 'CD overload' scenario also occurring in the digital domain?
I currently have a digital coax connection between CDP & Receiver. I am finding the sound better, but it is louder (than previous analogue connection).
It does seem a bit of a waste using an £800 CD player as 'just' a transport, I'm putting it down to the newer Pioneer receiver having better DACs.
This thread made me wonder though.

 

Yeah, the digital side presents a whole 'nother can o worms. If you have a way to feet the CD audio out of that receiver via RCA outs(tape out/video out, whatever) and get a average reading with a multimeter, that might be a way to find out.

 

Very silly—if the attenuators are working ideally, the loudest regular signal would be with the pot wide open. Potentiometers sound worse as the level goes down because a Pot is a variable resistor and gets less linear in operation the closer you get to full attenuation [lowest playback levels.]

 

I'm very glad to have shared a resource that will allow CD listeners here to listen to and evaluate CDs more objectively. I would like to ask a general terminology question though: what does it mean to be linear in operation or "less linear" in operation?

Does that mean that control of volume becomes less linear, not as smooth, more twitchy? Or less linear in frequency response? Thanks!

 

Distorts more. Also gets hinky in operation as attenuation is increased. Left/right balance is affected adversely. Again, the less attenuation coming from the potentiometer, the better the SQ all things being equal.

 

Thanks! That probably extends to my using the variable output via headphone volume knob setup until my pads arrived. Damn thing was all crackly as I turned it up and down during playback. In my case, the pads have it.

At least now I know the clipping or distortion I hear is all coming from the Black Eyed Peas "Elephunk" CD itself, and not my system. But that's better addressed in a loudness war thread.

 

Get some De-oxit and a can of compressed air. Get a little De-oxit in the pot, rotate the control several times to work the De-oxit into the variable potentiometer, blow away the excess with compressed air. A lot of the crackle goes away when the pots get cleaned. Should be periodic maintenance for any mechanical contacts or controls for electronics.

 

Honestly I don't know if it's worth it now that I have these attenuator pads to use on the fixed outs, but thanks for the tip.

 

It's always worth it, this is standard maintenance.

 

Uggh. must. open. hood. again.

lol!

 

Here is the caluculator: http://www.crownaudio.com/db-volts.htm It tells me I need 23 db of attenutation. I do suspect the the guidelines for something like a CDP input might be perhaps a titch different than for a pre/power pairing? I'm thinking of picking up a couple of the Harrison attenuators, a 6 and a 12 db and see what happens.

 

HERE is the chart I've been searching for over a half-frikn-hour for!... http://www.russandrews.com/article-CD-DVD-overload-attenuation.htm At the top of the page for a quick reference.

Plus a good article to read. Pass it on!

 

Thanks for that! A very useful article indeed. As I suspected, the values used for a source input are slightly different from those for the pre/power interface.

 

Thank you for starting this informative thread. My cd player has both fixed and variable outputs, but I never use it.
I use a computer and usb dac as my digital source. The dac outputs 2.25 V, but the input sensitivity on my receiver is 150 mV.
I've ordered the attenuators to remedy the mismatch.

Also, I have a different intergrated amp that has an input sensitivity of 200 mV, but lists its maximum input signal as 7 V.
Perhaps attenuation is less needed in that case.