Did you read previous linked test at all? Increased THD in higher frequencies is a false accusation: Google Käännä
"The distortions do not vary significantly over the frequency." Also graphs show nearly identical THD% with all used frequencies (20Hz, 1kHz, 20kHz). THD is below 0,01 with all mentioned frequencies between 0,5Vrms - 9,7Vrms. The very first graps ("Frequency response + distortion on the frequency:") shows nearly straight line (between 10Hz - 50kHz) of THD at 1Vrms (1Veff). Please stop spreding wrong information (includes also others).
I think there is not that great variance between DCXs, so it would seem that the test you refer to, was done wrong. Opinions?
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240 volt power?
Can someone in the USA please tell me if their DCX says it takes 240 volt power on the rear panel? Manual says "Internal switch-mode power supply for maximum flexibility (100 - 240 V~)" yet it seems they have released a version for each continent. Any reason to think one for the USA wouldnt work in Australia (240V)?
Can someone in the USA please tell me if their DCX says it takes 240 volt power on the rear panel? Manual says "Internal switch-mode power supply for maximum flexibility (100 - 240 V~)" yet it seems they have released a version for each continent. Any reason to think one for the USA wouldnt work in Australia (240V)?
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Yes it does. You can see for yourself here: http://cachepe.zzounds.com/media/qu...25496_rv-bb9242f45504de087b965195793116a5.jpg
If you distort a signal, you get harmonics- it is exactly analogous to a linearity error. See Bob Adams's JAES paper on the effects of jitter.
As to your second question, as long as the jitter isn't pathological (e.g., larger than the reciprocal of bit-rate), then the A/D and D/A jitter is all that affects the analog output signal. Jitter there causes distortion- again, see Adams's paper on the effect of jitter on the distortion of various types of D/A converters.
Hi Sy
still don't think its correct to refer to jitter as kinda harmonics - maybe with the exception of very special cases - do you have that paper you mentioned and could you possibly make it available to me?
Basically jitter is better described by a smear in the frequency domain IMO - especially when caused by pure noise. You'll find a paper on my page if you are further interested.
In simple explanation, distortion by jitter is in the style of Doppler intermodulation rather than harmonics.
Bottom line of my findings regarding jitter is that it can't be avoided – just minimised (same as Doppler IM by the way).
And second, that any meaningful digital resolution regarding bit depth is simply limited by jitter.
This makes it very unlikely that we soon will see a step towards 32 bit sampling rate that really *is* 32 bit .
My question regarding what else than AD / DA conversion could be affected was more rhetorically....
I am not familiar with "pathological jitter" you mention and in fact I have no clue what else than AD or DA conversion ever cold be affected by jitter. This - of course - also includes sample rate converters !
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On the other hand - I entered the discussion here at the point where analog versus digital volume adjustment was the topic – seems there is no long lasting interest in this ?
Michael
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DCX2496
Could someone comment on these mods, they seem not too expensive since pound's exchange rate to Euros is quite good. Are they any good? I'm considering that I might buy my second DCX with mods so I would be able to compare unmodded and modded. If there is some site that offers similar mods for cheaper, someone could throw a link.
Are there any downsides to output/input mods like that, when the whole board is removed. What happens to servo-balanced inputs? Is the input balanced or unbalanced after removing the board?
Could someone comment on these mods, they seem not too expensive since pound's exchange rate to Euros is quite good. Are they any good? I'm considering that I might buy my second DCX with mods so I would be able to compare unmodded and modded. If there is some site that offers similar mods for cheaper, someone could throw a link.
Are there any downsides to output/input mods like that, when the whole board is removed. What happens to servo-balanced inputs? Is the input balanced or unbalanced after removing the board?
It isn't and I didn't. The effect of jitter in the D/A and A/D process causes harmonics in the analog output- i.e., harmonic distortion.
"Clock Jitter, D/A Converters and Sample Rate Conversions", Adams, Robert W., 95th AES Convention, Preprint #3712. Available from AES.
"Theoretical and Audible Effects of Jitter on Digital Audio Quality", Benjamin, Eric and Gannon, Benjamin, 105th AES Convention, 1998, Preprint 4826. Ditto.
DCX Output stage schematic
Unsure about the Audiosmile mods but their website does contain a handy link to the output stage schematic.
http://www.audiosmile.co.uk/images/audiosmile/deq-output.jpg
My initial thought was that replacing R11 (2K32) with a 1K would reduce the gain by about 6dB. I am unsure about all the resistor network associated with the output op amps.
I would like to think that with a few resistor pulls on the resistors that change the gain when pin 3 is shorted, and maybe a few resistor subtitutions to adjust the output gain structure, this could be simplified to a simple balanced output that would not require pin 3 to be shorted for unbalanced outputs.
Unsure about the Audiosmile mods but their website does contain a handy link to the output stage schematic.
http://www.audiosmile.co.uk/images/audiosmile/deq-output.jpg
My initial thought was that replacing R11 (2K32) with a 1K would reduce the gain by about 6dB. I am unsure about all the resistor network associated with the output op amps.
I would like to think that with a few resistor pulls on the resistors that change the gain when pin 3 is shorted, and maybe a few resistor subtitutions to adjust the output gain structure, this could be simplified to a simple balanced output that would not require pin 3 to be shorted for unbalanced outputs.
Yes, reducing R11 will reduce the gain of the output stage. Changing R11 to 1K will reduce the gain of IC1B from 2.32 (7.33dB) to 1.002 (.017dB) reducing the gain by 7.31dB.
Another place to reduce the gain is by by lowering the value of R13 and R153 on IC1A. If R36=R37 and R13=R153 the gain of the balanced to single ended conversion stage is defined by R153/R37=4.99k/2K=2.495 or 7.94dB.
My head is too rummy now to try and decode the virtual transformer output stage (IC12A/B)...
Getting the output voltage of the DAC stage to meet your needs is an important detail of setting up a system. Too much system gain that results in high attenuation else ware in the system is not a good setup. With the Behringer being setup to deliver pro sound output levels we end up with more gain than necessary.
Hi Michael,
I for one am interested in digital volume control. Not sure if it belongs in this thread as the Behringer does not have remote capabilities or in the "A how to for a PC XO" That ShinOBIWAN started a long time ago. There is a lot more traffic in this thread.
I've been following in ShinOBIWAN and your steps setting up a computer based music server and digital crossover package. I'm quite happy so far but am still getting the system dialed in and details worked using a simple free crossover VST from www.rs-met.com out before graduating to the better FIR crossovers or going all the way to using "Acourate".
At this time the system is using the gain control VST from BlueCat audio controlled via MIDI to control the system volume. Seems to work well but I'll setup the system using Nyquist EQ as the gain control and see if I can hear any difference. I spend a lot of time listening to music at low levels so good performance at higher attenuation levels is plus.
Gary
Replacing the switcher with an analog supply is a pretty standard mod. For those in North America, Michael Mardis does that using special made (& very special) O'Netics transformers.
dave
Don't buy in that AES stuff
- sure, if you force opamps beyond their limits, you always can squeeze out a lot of fancy distortion, including harmonics – but this isn't our usual "any day" case with digital equipment like the DCX.
Jitter is a mere intermodulation (FM) – meaning it produces side bands, not harmonics at first hand.
Depending on the underlying source of intermodulation you get either rather descrete side bands like here :
or a "smear hill" both sides of your frequency like here
These outcomes are rock solid backuped by simulations and theory – and in case you don't trust my work I'll recommend to go through the reference links provided in my papers...
Michael
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Yes - not sure if that isn't too much off topic either.
But to me its interesting to see that no one has made an attempt towards using the digital attenuation capability of DAC's.
IIRC there is a plug in replacement to the DCX DAC that could do comfortable.
Might be, I have missed that part, as was not following throughout the thread.
Michael
There is pro and con to switched versus analog PS you know.
From mere measurement a switcher is plain heaven – depending on further treatment I guess there is no real need to step back to analog.
Here are measurements from the already linked thread about crossover distortion of amps – where as a by-product of that discussion measurements reveal, that analog PS have pretty ill effects to be addressed:
http://www.diyaudio.com/forums/solid-state/109147-geddes-distortion-measurements-4.html#post1330458
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
What we see at the left of the plots is that analog power supply introduces a lot of 50/60Hz harmonics whereas the swiched PS is pretty clean here.
This are measurements at the *speaker terminals* of poweramps – mind you !
Michael
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I think audiosmile is not going to replace the supply but will add LC filter(or i got you wrong): DCX2496
What about those input and output mods, is the analog transformer going to actually increase THD% from the original design?
Does anybody sell plug and play LC-filters for original PS of DCX, or is there some schematics how to make one?
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