Thank you, Soren. Would you recommend pursuing further increase of vref accuracy beyond 0.1%? I can relatively easily get it to 0.03% (by tweaking value of just one resistor) but I am not sure how much SQ gain, if any, it might render. Also, what is the influence on other harmonics?
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Perhaps this is interesting for you:
I there compared the digital volume control with attenuation by a resistor (for one value only).
The dam1021 vref's is already tracking to 0.01%, as I said, the 0.1% was an experiment....
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I have strange situation powering the DAM1021. Im using LM317 and LM337 to get the voltage of 10VDC on the output of the regs after the dummy load of 56ohm and as expected im getting about 10VDC.
Im using 820 ohm and 6.8k for the regulators.
The strange part is that when dummy load is connected Im getting proper 10V on positive and -10 on negative but the moment I connect both on the Dam im getting negative voltage of -4V on the positive and -5 on negative.
Then I connected only the positive im getting the 10V on the dam and when I connect the negative side Im getting proper -10 on the negative but when both are connected the negative voltage is observed.
when I use direct 7V 7V direct transformer the dam is working properly.
What is wrong in my setup?
Im using 820 ohm and 6.8k for the regulators.
The strange part is that when dummy load is connected Im getting proper 10V on positive and -10 on negative but the moment I connect both on the Dam im getting negative voltage of -4V on the positive and -5 on negative.
Then I connected only the positive im getting the 10V on the dam and when I connect the negative side Im getting proper -10 on the negative but when both are connected the negative voltage is observed.
when I use direct 7V 7V direct transformer the dam is working properly.
What is wrong in my setup?
You must have missed my breathless posts about this!
umanager allows you to "invert" the signal which is the SOEKRIS term for polarity reversal. Glad we did not have to type in "polarity reversal".
I use one of those simplistic hot key programs so it is simple to switch polarity and between the filters. Got a cheap wireless keyboard I can keep near the chair.
I am using the non-isolated RS232 and am using a USB Isolator board (I think it is from ANALOG DEVICES) using one of the board USB outputs to make it easy to cut the USB power and for the moment am powering the isolator with an OPTIMA battery just because it was available. The a USB to RS232 adapter from BRAINBOX. Cable is over 16 feet. I did slow down the transfer speed but have not tried the setup at full speed (119,200).
Must say I did not hear anything strange without the isolator but it does give one peace of mind.
I felt indeed that I came accross this discussion before - thank you to be so kind as to explain it again.
Good news is that it is possible to do in the digital domain. Bad news (for me) is that I have to start from scratch building this solution.
It looks like you managed to create a kind of 'remote' control for switching the polarity. Do you think it would be possible to implement a built in circuit (remote controlled) so that you could switch the polarity with a remote control on the fly without using uManager?
Also, when you switch polarity do you hear changes in your system?
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I have connected now the SPDIF pin of my cd transport signal processor (Sony CXD1125QZ) directly (through L-pad resistor network) to the SPDIF input of dam1021. I have removed the output transformer, two capacitors, two ICs and one resistor. The signal path is also much shorter now.
The result is absolutely spectacular! After listening to 3-4 CDs it is still hard to believe that this is real, but it is. What a nice treat to finish a busy weekend ... If you do not try it you will rob yourself big time.
See DAM1121 Build thread for another interesting option:
http://www.diyaudio.com/forums/digital-line-level/291645-building-soekris-dam1121-2.html#post4751083
Greg in Mississippi
Hi all,
Recently I built a dual dam1021 rev2 balance DAC for my friend, the DAC is sourced from a CDP using Pro2. There's an issue that when he starts playing music, the first 4 seconds always mute, however, the umanager shows signal is locked already. There's no such issue when the CD keeps going onto next track, or it is in repeat track mode, or he press the "next track" button of the CDP.
The detail is as follow:
Dual dam1021-05 rev2 (bal-left & right)
Firmware version 1.06
XLR analog output
AES input to DS8921. The DS8921 accepts +/- signal (pin 2 & 3) and output TTL signal to SPDIF2 + GND of the two dam1021 in J3.
Recently I built a dual dam1021 rev2 balance DAC for my friend, the DAC is sourced from a CDP using Pro2. There's an issue that when he starts playing music, the first 4 seconds always mute, however, the umanager shows signal is locked already. There's no such issue when the CD keeps going onto next track, or it is in repeat track mode, or he press the "next track" button of the CDP.
The detail is as follow:
Dual dam1021-05 rev2 (bal-left & right)
Firmware version 1.06
XLR analog output
AES input to DS8921. The DS8921 accepts +/- signal (pin 2 & 3) and output TTL signal to SPDIF2 + GND of the two dam1021 in J3.
Yes, thank you. I believe at this stage the conclusion is that dam1121 does not support polarity switching. But as Soren said, he is still updating the manual.
Anyway, I have dam1021 so need to explore its' options first.
Did you before also listen to the DAM trough the "SPDIF factory reference design"?
If yes, how would you describe the improvements/changes soundwise?
Further to the above description, my friend said the "4 seconds muting" issue happens at beginning of each track if he keeps playing the CD from first to last track.
Does anyone have any idea?
Thanks!
Thanks Soren, the function is there indeed. Do you think it would be possible to change the Px value through an external micro controller 'on the fly' with a remote control device?
The original SPDIF output circuit of my cd transport is very simular to the one recommended as standard for dam1021 SPDIF input. And it is transformer based with c 75ohm impedance.
As we discussed earlier, the main reason to have a transformer in the circuit is galvanic isolation of devices connected to each other with a stratch of cable, e.g. cd transport/player and the dac, and the requirement to drive this stratch of cable of unknown quality and length, impedance, capacitance and inductance. In my case I do not have any issues with galvanic isolation as I directly connect the signal processor leg generating SPDIF signal to the SPDIF input of dam1021 and this connection is floating (it does not touch anywere any grounds or anything else).
After SPDIF circuit simplification SQ gains are very significant and touch all important areas: significant increase of resolution, depth and stability of soundstage and positions of individual instruments and voices, increased energy, music is more immediate and there is much more emotional connection. Everything is just more real and involving. I did not say more analogue as analoge is still my benchmark but I caught myself comparing now this system with my analogue set up instead of feeling I am on the path of just 'improving' digital. And more mods are underway.
Will do direct comparisons with analogue as I have some albums on Cd's as well as 33 and 45rpm.
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AS far as I can tell you are going to need something that sends signals over an RS232 cable to get it to do anything but the emphasis is on as far as I know.
Polarity switches make a big difference.
Once you hear it you will want to be able to find the best position. There is no perfection in audio, we can only approach it. Most recordings seem to have a mixture of polarity so I find I am most sensitive to the voice so I switch for the most realistic voice - once you learn to recognize it it does sound like the lungs are breathing in when it is wrong. On some records there will be worthwhile changes in width of the stage. There can be differences heard in the bass.
At first, just go back and forth. Listen to each position for awhile and then to the other. At this point I can hear it, if i am paying attention, immediately. If in a casual mode it can take a few minutes and then I must fix it if it is wrong.
There are tales as told by Clark Johnsen who "discovered" this (while listening to John Lennon's last record, of all things) that have each track in the opposite polarity from the one that follows. He feels sure this had to be done on purpose. Of course, it was a Japanese CD, from the land of the most intrepid audiophiles. He figured it was to see if anyone noticed; the assumption being THEY (the engineers) could hear it but wondering if the public would notice it.
What a wonderful world when engineers can hear the effects of polarity!
Needless to say, polarity switching is a must for music lovers who care about the sound.
No I tried both the ways i have two trafo one with single secondary with single bridge and another with two secondaries with two bridges.
By the end the dam psu input has both the grounds shorted there on the board.
I tried even that. I even thought if there is a current drop but im using a 3A per secondary trafo. Its surprising though.
Yes, polarity of media and hardware might be one of the most confused things out there. And indeed different tracks might be recorded with different polarity in the same album. There are lists of the recording labels and their 'preferred' polarity. That might be the reason I always thought that some labels do not sound good in my analogue system. And changing (only) polarity in an analogue system is not easy.
Back to digital, the hope is there. Did you implement your dam1021 polarity switch solution in a stereo or dual mono configuration?