Andrew thanks, I am with you.
Frank,
http://www.diyaudio.com/forums/showthread.php?threadid=57697&perpage=10&pagenumber=4
the reason why I was confused about what you were suggesting is this thread in which Thorsten (Kuei) suggests to implement the connection in the figure in post #37 and use just +ve or -ve.
Basically, other than the polarity switch, filtering and attenuation, it is the same output configuration as in jan's mod, but tapping only half of the signal ( as Andrew suggests). Thorsten actually warns against bridging pin1 and 3 in post #28 in the same thread.
I am trying to understand yours and Thorsten's argument. I am now clear that the two pins need to have the same filter ahead of them and being terminated to ground if I want to use just one half of the signal (so the connection in the picture in my post 858 in this thread is not suitable for this).
Thanks a lot for the patience
Giulio
Frank,
http://www.diyaudio.com/forums/showthread.php?threadid=57697&perpage=10&pagenumber=4
the reason why I was confused about what you were suggesting is this thread in which Thorsten (Kuei) suggests to implement the connection in the figure in post #37 and use just +ve or -ve.
Basically, other than the polarity switch, filtering and attenuation, it is the same output configuration as in jan's mod, but tapping only half of the signal ( as Andrew suggests). Thorsten actually warns against bridging pin1 and 3 in post #28 in the same thread.
I am trying to understand yours and Thorsten's argument. I am now clear that the two pins need to have the same filter ahead of them and being terminated to ground if I want to use just one half of the signal (so the connection in the picture in my post 858 in this thread is not suitable for this).
Thanks a lot for the patience
Giulio
no.
both output pins of the DAC should be loaded. But they don't both need the full filter.
The un-used output could be just grounded but this may affect the operation of the DAC, so instead feed the un-used output through a safe load to ground. I'm suggesting that a safe load is about 10k. I believe the DAC will behave itself if both outputs are properly terminated rather than floating or grounded.
Andrew,
Are you referring to the XLR outputs or the DAC outputs. The DAC outputs on the http://forum.audiophonics.fr/viewtopic.php?t=12 kit are left floating (except for LP filter).
Would it be better to tie the unused DAC outputs to GND via 30K so it looks the same to the DAC as the used output?
Philip
Are you referring to the XLR outputs or the DAC outputs. The DAC outputs on the http://forum.audiophonics.fr/viewtopic.php?t=12 kit are left floating (except for LP filter).
Would it be better to tie the unused DAC outputs to GND via 30K so it looks the same to the DAC as the used output?
Philip
oettle said:
I think what you are saying is the same as I said but, in case we are different, I shall rephrase.
The two balanced DAC outputs can be sent through two filters for a full balanced output.
or
one DAC output can be filtered and fed to the XLR and the other DAC output is loaded to 10k (cheap and zero space required).
BUT.
the unused pin of the XLR socket will completely upset any trully balanced receiver. The unused pin MUST be terminated if there is any chance that a balanced system will be connected downstream.
Have a look at Jensen's site for a psuedo balanced source if you don't believe me.
Hi,
The AK4393 has a balanced two line differential output. The two outputs have a 180° (inverted) phase shift. Once again, what you have to amplify is the difference between the two outputs and not the difference between one output and ground. That's similar but not the same.
Philip it's no problem to have an unbalanced power amp. Just read thread 879.
Frank
The AK4393 has a balanced two line differential output. The two outputs have a 180° (inverted) phase shift. Once again, what you have to amplify is the difference between the two outputs and not the difference between one output and ground. That's similar but not the same.
Philip it's no problem to have an unbalanced power amp. Just read thread 879.
Frank
Andrew,
could you please confirm that you mean section 2.4 here ?jensen_AN003
This is what a balanced receiver would see in my case if I just shunted through a resistor to ground the -ve output of the dac, but did not connect it to pin 3 and I terminated pin 3 to ground in a symmetric way to pin 2.
TIA
Giulio
could you please confirm that you mean section 2.4 here ?jensen_AN003
This is what a balanced receiver would see in my case if I just shunted through a resistor to ground the -ve output of the dac, but did not connect it to pin 3 and I terminated pin 3 to ground in a symmetric way to pin 2.
TIA
Giulio
Hi Oettle,
I do not understand something.
If the two DAC outputs are the same and they are inverted relative to each other, then referencing either to ground should be identical. Referencing one to the other should also be identical but with +6db gain.
I cannot see what you are trying to explain in using "similar".
However, I think someone (Janneman?) did say they both have a DC offset. Feeding the DC offset through a DC blocking cap will sort that and still the inverted should be identical.
I think you slipped in a phase shift by accident. That would involve a timing difference. I'm sure you didn't mean that. or did you?
BTW,
I have read posts 879 & 870.
You've said it again. "similar" but not the same.oettle said:
I do not understand something.
If the two DAC outputs are the same and they are inverted relative to each other, then referencing either to ground should be identical. Referencing one to the other should also be identical but with +6db gain.
I cannot see what you are trying to explain in using "similar".
However, I think someone (Janneman?) did say they both have a DC offset. Feeding the DC offset through a DC blocking cap will sort that and still the inverted should be identical.
I think you slipped in a phase shift by accident. That would involve a timing difference. I'm sure you didn't mean that. or did you?
BTW,
I have read posts 879 & 870.
Hi,
The difference is accuracy and noise. Since your plan is to improve something this should be important for you. Here the datasheet: http://www.asahi-kasei.co.jp/akm/en/product/ak4393/ak4393_f02e.pdf
If you prefer 'inverted' use this wording. It's the same as a 180° phase shift.
Bye,
Frank
The difference is accuracy and noise. Since your plan is to improve something this should be important for you. Here the datasheet: http://www.asahi-kasei.co.jp/akm/en/product/ak4393/ak4393_f02e.pdf
If you prefer 'inverted' use this wording. It's the same as a 180° phase shift.
Bye,
Frank
Hi Oettle,
your excused.
Phase SHIFT is a movement along the time line.
Phase INVERT is + to - and - to + but no time shift.
If the grounding in the DAC is properly applied then pole to ground SHOULD be identical to +pole to -pole.
If the ground has some noise that is isolated from the DAC then pole to pole may be cleaner and therefore more accurate. That's the beauty of isolated and balanced signals.
your excused.
Phase SHIFT is a movement along the time line.
Phase INVERT is + to - and - to + but no time shift.
If the grounding in the DAC is properly applied then pole to ground SHOULD be identical to +pole to -pole.
If the ground has some noise that is isolated from the DAC then pole to pole may be cleaner and therefore more accurate. That's the beauty of isolated and balanced signals.
nicko500 said:Hello,
To help you tuning this board, i decided today to publish schematics of my board.
I hope it will be usefull for DIYers
Enjoy :
http://forum.audiophonics.fr/viewtopic.php?t=12
I hope you will share your modifications with all user to arrive to a good finished board.
Kind regards.
FERHAT Nicolas.
Audiophonics.fr
That output board is fine. I'm looking to buy two of them, as soon as is possible. Plese put two back up on ebay, or give me a price here in a PM, if you can, please. I missed the ebay auction by a day,and would have bought it and asked for another. Is anyone selling the boards in North America? I can assemble them myself.
But what I'm looking for, is a 6 channel relay based shunt attenuator board, for the volume control. I wonder if such would fit inside the DCX...hhmm..... that would be quite a few relays.
Why relays? well, digital volume controls are not good, in my estimation, we have enough degredation from using a digital crossover in the first place.
Let's try and stop the signal damage there. It's bad enough already. The reason we are going to a digital crossover, are for it's avantages, not it's detrimental aspects. We should try and remember that the detrimental aspcts, for some of us, are less of a problem than the benefits the digital crossover brings to the audio bargaining table.
We have made a trade-off of qualities. Let's try and keep that balance of trade-offs.
Meaning, don't degrade the signal any further, via more digital manipulation. Go to what analog does well, at that point.
I am considering a remote controlled system here, not manually controlled. Another part of the equation, is the price. What I'm looking for, of course, is the best possible quality,at the lowest possible price. If the numbers get too high, I'll simply be switching to DEQX units,and forgetting about the two DCX units I own. In the end, that might be smarter of me, but all I will inheret then, is a new set of issues, at a much higher initial expense level.
This means, an analog channel output adjustment system.
However, with the use of motorized volume pots, we would literally need to used computerized measurement systems to replicate a given output level for using the crossover on multiple speaker designs, when switching the design around in our living rooms, due to the inaccuracy of volume pots. We need repeatbility in our settings, as we gain the advantage of the ganged volume manipulation, which is the whole point.
Using a shunt volume configuration, that is, with a post shunt volume amplification, or high grade op amp. The shunt volume brings about a constant load on the AKM chip as well.
A shunted stepped attenuator can be used for precise adjustments, but stepped attenuator volume pots are very scarce, and quite expensive, when found. I'm not aware of any motorized ones.
I like the Burr-Brown (TI) stereo volume chip, which is analog, and is in my tubed Shanling SACD units, but it too suffers from damaging the signal to a large degree, it is not of an audiophile nature. However much Burr brown says it is. I did single cause analysis of modifications of it's local power supply (on the circuit board) and coupling and could not achieve much of a change in the sound of the shanling via that method. This seems to indicate that the unit is not as transparent as one would hope, for a maximum quality application.
Some would say it damages the signal far less than a digial volume control, and that might be true. I feel it does damage the signal less than a digital volume control. But it does damage the signal far more than I want it to.
What is left for precise control, is switched resistive ladder networks, that are discrete, or relay controlled shunt volume designs, as my preference. The relay based shunt volume characteristic, keeps the relays essentially out of the signal path, or in this case, halves their sonic influence, as they are parallel to the singal that is being used, and heard.
Are there any out there, that have the required signal range, that can be adapated for this use?
What I desire to do here, in terms of a relay based shunt volume, can easily be placed before your output board.
I'm also running out of time. I have a set time limit, and that these two units must be fully operational and sussed out (all problems-issues overcome) by March at the latest. I'm getting ready for an audio show.
Hi Nicholas and all,
I have done some more work on the board based on the advice of people on this forum plus a useful PM.
Nicholas, basically you would have to terminate with a >10K resistor to ground both the +ve and -ve output. There is no way you can fit 12 Polyprops coupling caps in there, though. So if I were you I would stick with single ended (but I know that Frank will disagree
). On this topic, I am currently running the card into two pairs of TX102 transformer volume controls. I have been told that running balanced into the TX102 nulls DC offset to a satisfactory approximation. I was somewhat uncertain on this point until the useful PM. I have therefore rewired the card balanced and took out the coupling caps over the weekend.
(I am currently running two ways, I will move to three ways with a buffered stepped attenuator on the bass. There will be a coupling cap ahead of the buffer).
Two points:
1) those mundorf caps are good! I get of course more transparency w/out them, but the difference is not that big.
2) The card as it is connects pin 3 on the XLR connectors to ground and lets pin 1 floating. That is irrelevant when run single ended as one would brige -ve and ground on the RCA side, but is a major pain for users who want to turn the card into balanced. Nicholas, if you are doing a second run I suggest you connect pin 1 to ground. This would halve the number of connections that a modder has to establish. Especially given that those ground tracks to the output pins are very fragile!
Finally, to Jan:
you mention somewhere above in this thread that you are not sure that your muting circuit works if one runs your card DC coupled. The AKG dac has muting . My understanding is that your muting circuit eliminates noises from the discharge of the coupling caps. But w/out coupling caps those noises should not be there. Am I missing something?
Thanks all for the help
Giulio
Hi,
I did it my way (fully simmetrically of course) with a little help from Jan. Thanks!
It's a an active filter (fast roll off) without any additional active components (the instrumental amp is part of the UcD power amps). It has nearly no phase shift (about 1°) at both ends and needs small AC coupling caps (low 2.7uF, mid 1.0uF, high 0.1uF). A volume control pot is integrated.
If you are looking for clear mids and straight lows it's not such a bad solution - all together (DCX and power amps) in a 2U housing not much bigger than 2 DCX.
See attached file (change appendix to .asc and use http://www.linear.com/designtools/s...egistration.jsp).
There are different ways.
Regards,
Frank
I did it my way (fully simmetrically of course) with a little help from Jan. Thanks!
It's a an active filter (fast roll off) without any additional active components (the instrumental amp is part of the UcD power amps). It has nearly no phase shift (about 1°) at both ends and needs small AC coupling caps (low 2.7uF, mid 1.0uF, high 0.1uF). A volume control pot is integrated.
If you are looking for clear mids and straight lows it's not such a bad solution - all together (DCX and power amps) in a 2U housing not much bigger than 2 DCX.
See attached file (change appendix to .asc and use http://www.linear.com/designtools/s...egistration.jsp).
There are different ways.
Regards,
Frank