CDP Output impedance

There are 2 aspects to the spec of 2Volts / 10K Ohms :

Quantity &
Quality

QUANTITY : This aspect is that it will deliver 2Volts into 10 K Ohms ( or higher than 10 K Ohms, eg 15 K Ohms )

QUALITY : This aspect implies that the CDP will meet the specified DISTORTION if the Output load ( the Pre amp or passive Volume control or whatever ) is 10K Ohms or Higher ( eg 15 K Ohms )

If the output load is lower ( eg 5 K Ohms ) it will draw too much current from the CDP output stage and either :

a. 2V output will not be delivered. ( a smaller Voltage such as 1.5 Volts may be deluivered )

or / and

b. 2 Volts output will be delivered, at more than the max specified distortion.

Gentlemen:

2V output off the CDP's RCAs is fine BUT are you'll quite sure about the output impedance? Normally most of the units I've come across are below 300 ohms, good ones being typically below 100 ohms.

IMHO, Output Impedance is a measure of the "Quantity" that I have listed in my above.

Output Impedance is a measure where the Load of that value ( say 50 Ohms or 200 Ohms or whatever.. ) will drop the CDP output by 50% ie from 2 Volts to 1 Volt.

By that time, distortion on the output signals from the CDP will have gone to Hell ....

Hence the CDP / Preamp or whatever needs to be operated at its Recommended Load impedance, if you want to get the published specification.

Output Impedance is a measure where the Load of that value ( say 50 Ohms or 200 Ohms or whatever.. ) will drop the CDP output by 50% ie from 2 Volts to 1 Volt. By that time, distortion on the output signals from the CDP will have gone to Hell .... Hence the CDP / Preamp or whatever needs to be operated at its Recommended Load impedance, if you want to get the published specification.

A typical scenario: (Say Budget NAD gear)

CDP (Output): 2V/300ohms ----> PRE (Line-Level Input/s): 20kohms

The ratio here is 66x. Typical CDP's output imp is 100-300 ohms while input imp of Pre's CD input is 20k-100k; quite common is 47kohms.

Please enlighten me where's the scope of that 2V output from the CDP to fall by 50% or whatever & the distortion to rise to hell.....

20x is considered minimum & higher figures are better.

Do note that the CDP's 2V output is only possible when recorded material on a CD playing is at 0 dBFS which is "rare". Test tones have them, never come across any music recorded at 0 dBFS, always something like -6 or -8 dBFS. Western classical even lower due to high dynamic range present in them.

audio_engr - You are PERFECTLY correct in ALL that you have said.

I was pointing out that Output Impedance and the recommended load impedances are TOTALLY DIFFERENT and should not be confused.

As you have correctly pointed out .... the load impedance should be... and Generally IS 10 Times or so, the output impedance.

Cheers !

Yes...

thats what I thought...2V will be delivered into a 10Kohms load but what would be the actual output impedance of the source is still a question mark.

Funny for Denon pro cdp's...their balanced outputs have an output impedance number of 100Ohms but its the unbalanced(RCA) which is specified in this fashion....would it be that they want to hide an unusually high output impedance figure ?

Manek.

folks, please do forgive my "layman-ness" in this. but does not the capability to maintain the same voltage ie 2V across any load depend on the power supply capability, ie capability to supply constant current across all loads ?

also some DACs/CDPs put across a higher voltage than 2V. this does affect the gain of the suystem, but does it provide any greater ability to handle these dynamics ?

folks, please do forgive my "layman-ness" in this. but does not the capability to maintain the same voltage ie 2V across any load depend on the power supply capability, ie capability to supply constant current across all loads ?

The job is really of the output stage of the pre amp or CD player or whatever source.

also some DACs/CDPs put across a higher voltage than 2V. this does affect the gain of the suystem, but does it provide any greater ability to handle these dynamics

Frankly, there is an Embrassment of Output Voltage from CD players..

Most deliver a max of 2000 mV ( ie 2 V ) and some even more..

Most Power amps are driven to tgheir FULL Output with 500 mV ( ie 0.5 Volts )

Hence most pre amps deliver a Unity gain at their 12 o Clock position, and actually attenuate the signal below the 12 o clock position !

Ofcourse as audio_engr has pointed out, the typical output during everyday listning ( except at Crecendos ) the CD player output will be rather lower than 2V...

Infact the dynamic range will really be limited by the Power Amp + Speaker + Room + ofcourse the listne's preference of the minimum Volume he finds listnable during the soft passages.

The dynamic range of even budget CD players exceeds that of all else... even the music recorded on the master tape or the noise floor of the recording.

[quote="Amp_Nut"][quote]

Most Power amps are driven to tgheir FULL Output with 500 mV ( ie 0.5 Volts )

Hence most pre amps deliver a Unity gain at their 12 o Clock position, and actually attenuate the signal below the 12 o clock position !

[/quote]

Interesting..so what exactly does an active preamp do better than an passive preamp other than Provide an easier load to the source ?

Also do acive pre-amps preserve the same input signal and give it out as output OR provide modiulated signal with a different gain ?

The input impedance of my power amp is only 8000 ohms. Would this be lower than most sources would expect? When you speak of 2V at 10,000 ohms, is this spec also generally true for computer soundcards too? What price do I pay for not having a pre-amp, except convenience?

Yes it is on the low side....I think 20Kohms and above is the norm today for input impedance of preamps and integrated amp inputs.

Amp_Nut: Appreciate ur gesture!

Neutral:

The input impedance of my power amp is only 8000 ohms. Would this be lower than most sources would expect? When you speak of 2V at 10,000 ohms, is this spec also generally true for computer soundcards too? What price do I pay for not having a pre-amp, except convenience?

8k input imp of a Pwr amp? Very much on the low side, thus will definitely require a low output imp drive from either a CDP source (if you want to bypass a pre) or a pre will low output imp to drive that Pwr amp.

Input sensitivity is another spec that matters, esp that of a Power amp. The lower this figure, the less Gain on the pre is required to get healthy SPLs in the room. Usually the input sens of integrated amp's Pwr section is sometimes just 250mV - 350mV and invariably in such cases, by the time the Volume knob hits 12 O'clock, you are blasting.... In most of such cases, the pre section of the integrated is actually functioning in a mode where No Gain is required. Ofcourse, a passive will work wonderfully here and active cannot be compared with a passive. Passive is almost "straight wiring" whereas actives have Power Supply, loads of components etc. that progress to rob ultimate transparency, higher noise.

These days, highend Power amp's sens is around 1000mV to 1800mV (I am speaking of ones in the 100-300 watts 8-ohms category) that surely mandates an active pre. You can still get away using a Passive in these circumstances by using a high drive DAC like the Theta Pro Gen which outputs 6.5V in RCA and 7.5V in XLR. Wadias also have 4V outputs to drive amps directly. Even the little Benchmark dac sports a wonderfully adjustable output via its trimpots at the rear.

Manek schrieb:

hi all..... I have come across another instance of an output impedance rating that I cant seem to fathom. Jolida tube cdp rca output specs specs say 2V,47Kohms and a denon pro C-680 mentions 10Kohms, 2V for rca outputs.... I could understand Jolida making a typo mistake but all denon pro cdp's have this high output impedance on their manuals for unbalanced rca outputs. Does it mean it outputs 2V when connected to a 47Kohm/10kohm load ? This I dont think could be a typo so is there a way to interpret these specs ? Manek.

So, Manek, do you understand these output impedance specs after all this discussion OR are you still confused?


IMHO, the Jolida output impedance spec does not talk about the Jolida itself as it talks about the next stage (preamp or power amp) that will be connected to it.
What it's saying, IMHO, is that the Jolida will output 2V only if the next stage's input impedance is 47K. If the next stage's input impedance is less than 47K, the Jolida will (1) not be able to output 2V or (2) it will output 2V BUT with much higher distortion.

Same deal w/ the Denon.
In the Denon case, you can come down to 10K input impedance of the next stage before the Denon stops outputing 2V or outputs 2V with higher distortion.

(Amp_Nut's post written in my own words).

I agree that it is a funky way to express the output impedance of the unit itself by specifying what the input impedance of the next stage should be!

In the Jolida case, you can infer that the Jolida's output impedance is quite high since it needs the next stage to be 47K or higher. What the exact output impedance of the Jolida is, we do not know. All we know is that it is on the high side.

In the Denon's case, it is much lower. Again, what the exact value is, we do not know.

Hope that this clarifies some (if you are squared away on this issue, ignore my post).

Regarding Jolida CDP, I got a reply from Michael Allen (President & CEO) of Jolida saying that Jolida CDP output impedance is 47 Ohm and that 47K figure should be treated as a typo.

I got similar replies from Underwood Hi Fi, GC Audio and Responce Audio (all arr big Jolida dealers and specialize in modding Jolida products).

But according to me , 'Jolida CDP can deliver 2V only when next stage has 47K as an input impedance' sounds more logical.

bombaywalla...yes...thats what I thought as well but since I saw the denon specs were on the same lines as well it occured to be that it may not be a typo as Micheal Allen makes it out to be

Thats why the post....

I wonder if there is a tube output stage which is 47 ohms on the output impedance without having a buffer or impedance conversion of some sort after it ???

Manek.

audio_engr schrieb:

Input sensitivity is another spec that matters, esp that of a Power amp. The lower this figure, the less Gain on the pre is required to get healthy SPLs in the room. Usually the input sens of integrated amp's Pwr section is sometimes just 250mV - 350mV and invariably in such cases, by the time the Volume knob hits 12 O'clock, you are blasting.... In most of such cases, the pre section of the integrated is actually functioning in a mode where No Gain is required. Ofcourse, a passive will work wonderfully here and active cannot be compared with a passive. Passive is almost "straight wiring" whereas actives have Power Supply, loads of components etc. that progress to rob ultimate transparency, higher noise.

In other words, the preamp works as a passive gain control most of the time? In my observations, most amps work nicely at the 9 O'clock position.

audio_engr schrieb:

These days, highend Power amp's sens is around 1000mV to 1800mV (I am speaking of ones in the 100-300 watts 8-ohms category) that surely mandates an active pre. You can still get away using a Passive in these circumstances by using a high drive DAC like the Theta Pro Gen which outputs 6.5V in RCA and 7.5V in XLR. Wadias also have 4V outputs to drive amps directly. Even the little Benchmark dac sports a wonderfully adjustable output via its trimpots at the rear.

That would be really convenient.
Can I take it that an integrated soundcard would have a higher output impedance than any good CD player, resulting in a loss of details and dynamics?

When a source reaches close to its voltage peak (mostly 2V), does it start clipping / distorting its output?

I wonder if there is a tube output stage which is 47 ohms on the output impedance without having a buffer or impedance conversion of some sort after it ???

I am yet to see a tube output stage below 300-500 ohms. And 47 as per Jolida, ha! ha! I'll be wary.....

Very good solidstate highend CDPs or dacs are below 100 ohms, some as low as 20 ohms.

Cheers!

G_S_Madhav schrieb:

Regarding Jolida CDP, I got a reply from Michael Allen (President & CEO) of Jolida saying that Jolida CDP output impedance is 47 Ohm and that 47K figure should be treated as a typo. I got similar replies from Underwood Hi Fi, GC Audio and Responce Audio (all arr big Jolida dealers and specialize in modding Jolida products). But according to me , 'Jolida CDP can deliver 2V only when next stage has 47K as an input impedance' sounds more logical.

I would go with your gut instinct.

I am yet to see a tube output stage below 300-500 ohms. And 47 as per Jolida, ha! ha! I'll be wary.....

I'm with audio_engr on this! The only tube units that have 20 Ohms output impedance are usually transformer-coupled at the output.