"You know what, this is funny but the "Mute outs" is still bloody working even if T1 to T6 trannies are out of business !"
They may mute the signal out of the DSP to the DAC for the Mute button function.
Are the hardware shunt mutes used for turn on/off states to avoid transients?
I had the earlier BFD and it had very bady on/off transients.
Something like that in a line leve crossover where a tweeter is directly connected to an amp would be *bad*.
I have never tried the DCX to see if it has on/off transients as I didn't want to risk my drivers. I just leave them on all the time.
Shawn
They may mute the signal out of the DSP to the DAC for the Mute button function.
Are the hardware shunt mutes used for turn on/off states to avoid transients?
I had the earlier BFD and it had very bady on/off transients.
Something like that in a line leve crossover where a tweeter is directly connected to an amp would be *bad*.
I have never tried the DCX to see if it has on/off transients as I didn't want to risk my drivers. I just leave them on all the time.
Shawn
Konnichiwa,
Which begs the question: "Why don't you know?"
You could have consulted the DAC IC's Datasheet which is readily available on the net and you would have found out that the DAC will drive an 600R AC per phase and a 1K DC per Phase load, has 3.5mA rated output current or theoretically 8.2V Peak into 1K2 Balanced AC Load.
Stoppband attenuation (including the noisefloor from the Noiseshaper whic actually dominates) is better than -75db, a little lowpass filtering (best 2nd order LC LPF) seems indicated.
My final recommended output confioguration would be to use a 1.2K Load Resistor per phase in parallel with 1.5nF capacitance and a 4.7mH Inductor in series to the DAC Chip, per phase and DC coupled, take from each junction point a 2.2uF (or larger) coupling capacitor.
This circuit allows loads down to 10K per phase or 20k balanced, retains the balanced output and allows 1nF per phase or 500pF balanced cable capacitance, in other words more than enough to accomodate most sensible cables and amplifiers, but prohibiting extreme loads (which a 600R:600R line output transformer may actually allow).
FWIW, at the stopband return of the Digital filter (assuming 96KHz operation) the passive filter will be > 40db down, for 44.1KHz operation there will still be 30db attenuation, sufficient for most competently designed amplifiers to handle okay.
Sayonara
mbroyles said:
Which begs the question: "Why don't you know?"
You could have consulted the DAC IC's Datasheet which is readily available on the net and you would have found out that the DAC will drive an 600R AC per phase and a 1K DC per Phase load, has 3.5mA rated output current or theoretically 8.2V Peak into 1K2 Balanced AC Load.
Stoppband attenuation (including the noisefloor from the Noiseshaper whic actually dominates) is better than -75db, a little lowpass filtering (best 2nd order LC LPF) seems indicated.
My final recommended output confioguration would be to use a 1.2K Load Resistor per phase in parallel with 1.5nF capacitance and a 4.7mH Inductor in series to the DAC Chip, per phase and DC coupled, take from each junction point a 2.2uF (or larger) coupling capacitor.
This circuit allows loads down to 10K per phase or 20k balanced, retains the balanced output and allows 1nF per phase or 500pF balanced cable capacitance, in other words more than enough to accomodate most sensible cables and amplifiers, but prohibiting extreme loads (which a 600R:600R line output transformer may actually allow).
FWIW, at the stopband return of the Digital filter (assuming 96KHz operation) the passive filter will be > 40db down, for 44.1KHz operation there will still be 30db attenuation, sufficient for most competently designed amplifiers to handle okay.
Sayonara
Thmartin said:
Thierry,
Yes, please measure it. You'll find approximately 2.6 VDC on each of the four output pins on each chip. A simple low-pass filter like you described (I hope my reading of your description didn't get lost in the translation...I don't think so because your English seems fine) will not do anything to block or balance this DC level and it will be passed on to the following stage.....whatever that may be.
Please be careful because this is a 1% situation.
Cheers,
Davey.
Kuei Yang Wang,
I just made an experiment a few weeks ago with LC filtering on DCX.
My conclusion was that it looks good on paper but was bad in reality. The problem is that there seems to be a lot of RF floating around inside DCX and the L part of the filter will pick it up like antenna.
I can post measurements later when I get home. I looked at the spectrum of 10Hz-40kHz and the LC type filter created a lot more dirt that raised above the noisefloor.
Thus I burried the idea of LC and now my setup will be
RC -> 6ch volume pot -> RC -> OPA2134 in simple gain mode -> output.
I ran the DCX with simple RC filtering and no analog stage a long time, some 6 months or so, but in the end I did not like the sound especially in top octaves. There is something wrong there. At first it gives a very positive impression but gets tiring and irritating after a month or two.
Also the gain is too small for my liking.
Regards,
Ergo
I just made an experiment a few weeks ago with LC filtering on DCX.
My conclusion was that it looks good on paper but was bad in reality. The problem is that there seems to be a lot of RF floating around inside DCX and the L part of the filter will pick it up like antenna.
I can post measurements later when I get home. I looked at the spectrum of 10Hz-40kHz and the LC type filter created a lot more dirt that raised above the noisefloor.
Thus I burried the idea of LC and now my setup will be
RC -> 6ch volume pot -> RC -> OPA2134 in simple gain mode -> output.
I ran the DCX with simple RC filtering and no analog stage a long time, some 6 months or so, but in the end I did not like the sound especially in top octaves. There is something wrong there. At first it gives a very positive impression but gets tiring and irritating after a month or two.
Also the gain is too small for my liking.
Regards,
Ergo
Konnichiwa,
It is not surprising AT ALL. The circuit you cite is aimed at the exact opposite problem to the one faced wwhen directly interfacing the DCX2496 DAC's, that is it is meant to give a Pseudo-balanced output from a single ended source, while we need one that gives a SE source from a true balanced output.
Sayonara
AndrewT said:
It is not surprising AT ALL. The circuit you cite is aimed at the exact opposite problem to the one faced wwhen directly interfacing the DCX2496 DAC's, that is it is meant to give a Pseudo-balanced output from a single ended source, while we need one that gives a SE source from a true balanced output.
Sayonara
Konnichiwa,
I rather doubt that, actually, though some types of chokes are more sensitive to noise pickup than others, I suggest fully enclosed types, eg poy core etc.....
Are you sure that this was not the result of resonances in the filter? LC filters are invariably critical and need a well defined termination impedance to not cause all sorts of mischief.
Ciao T
ergo said:
I rather doubt that, actually, though some types of chokes are more sensitive to noise pickup than others, I suggest fully enclosed types, eg poy core etc.....
ergo said:
Are you sure that this was not the result of resonances in the filter? LC filters are invariably critical and need a well defined termination impedance to not cause all sorts of mischief.
Ciao T
Hi Ergo,
First of all, thanks for the XO2/5 clock installation tips you made available for us. I used it on my own modest website (in french) Clock installation About the distortion characteristics of the Behringer here's what I measured on my own DCX with the RC 1st order low-pass filter.
Cheers
Thierry
First of all, thanks for the XO2/5 clock installation tips you made available for us. I used it on my own modest website (in french) Clock installation About the distortion characteristics of the Behringer here's what I measured on my own DCX with the RC 1st order low-pass filter.
Cheers
Thierry
An externally hosted image should be here but it was not working when we last tested it.
I do not remember if we already had this discussion before or I 'v seen it at yahoo DCX group. It was about calculating correct cap in order to provide DC blocking as well as HF roll off.
Before I did my mod I consider price for that approach, and with good caps, it still would require some investment. Besides the price there is performance issue, and I would always choose transformer over cap in the signal path.
I completely agree with Kuei - transformers are best choice. Yes they will cost you as much as two Behringer units, but as I mentioned good caps will do as well. I needed balanced out, so in my case it would be minimum 12 caps - for 6 balanced outs.
I am using Lundahl 1674 transformers, and what they do: they block DC out of DACs, they provide balanced input and output, they roll off HF above 50 KHz, as well they provide galvanic insulation. On the top of that they are 1+1:1; 1+1:2 or 1+1:4.
That means that you could gain + 3dB in 1+1:2 set up without having anything else in the path of the signal. Obviously the best way would be 1+ 1:1. I am using mine in 1+1:2 since I need little more gain. Lundahls are $ 90.00 each.
In my set up nothing could replace that clean and wide open top end coming straight from DAC to the amp. There is only transformer and single resistor in the passive volume control before signal hits the amp.
Peace, and Happy Holidays
AR2
Before I did my mod I consider price for that approach, and with good caps, it still would require some investment. Besides the price there is performance issue, and I would always choose transformer over cap in the signal path.
I completely agree with Kuei - transformers are best choice. Yes they will cost you as much as two Behringer units, but as I mentioned good caps will do as well. I needed balanced out, so in my case it would be minimum 12 caps - for 6 balanced outs.
I am using Lundahl 1674 transformers, and what they do: they block DC out of DACs, they provide balanced input and output, they roll off HF above 50 KHz, as well they provide galvanic insulation. On the top of that they are 1+1:1; 1+1:2 or 1+1:4.
That means that you could gain + 3dB in 1+1:2 set up without having anything else in the path of the signal. Obviously the best way would be 1+ 1:1. I am using mine in 1+1:2 since I need little more gain. Lundahls are $ 90.00 each.
In my set up nothing could replace that clean and wide open top end coming straight from DAC to the amp. There is only transformer and single resistor in the passive volume control before signal hits the amp.
Peace, and Happy Holidays
AR2
Hmm perhaps yes - it might be the inductors were not good enough.
This is the type I used
Inductor
I think I will try to get by without inductors. Seems to be a more predictable way to go.
Anyway, this is the current state of my analog stages. I have two channels built and each channel has one OPA134 and it's own shunt regulator.
I also have a PCB design ready for all 6 channels but the next step is to get it etched and it will take a bit of time before I can do that
This is the type I used
Inductor
I think I will try to get by without inductors. Seems to be a more predictable way to go.
Anyway, this is the current state of my analog stages. I have two channels built and each channel has one OPA134 and it's own shunt regulator.
I also have a PCB design ready for all 6 channels but the next step is to get it etched and it will take a bit of time before I can do that
An externally hosted image should be here but it was not working when we last tested it.
Kuei Yang Wang said:
Well, the transformer allows a configuration for pretty much any solution needed. How 'bout this simple circuit:
http://www.jensentransformers.com/as/as089.pdf
An appropriate filter in addition and it should work fine.
Davey.
You know what, this is funny but the "Mute outs" is still bloody working even if T1 to T6 trannies are out of business !
Still can't figure out what Behringer has done there
I suppose it's possible that they activate "muting" at various points along the signal path....like maybe the DAC itself doesn't "mute" or "unmute" very cleanly so they threw in an mute/unmute downstream.. maybe it's just a quiescing or stabilizing feature for that filter circuit when no signal is feeding it.
Anyway, just hypothosising since I don't have the rest of the circuit or the design engineer here with me. That circuit is most definitely a shunt straight to ground though. Someone must have thought is necessary..
Still can't figure out what Behringer has done there
I suppose it's possible that they activate "muting" at various points along the signal path....like maybe the DAC itself doesn't "mute" or "unmute" very cleanly so they threw in an mute/unmute downstream.. maybe it's just a quiescing or stabilizing feature for that filter circuit when no signal is feeding it.
Anyway, just hypothosising since I don't have the rest of the circuit or the design engineer here with me. That circuit is most definitely a shunt straight to ground though. Someone must have thought is necessary..