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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
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Old 30th December 2017, 01:38 PM   #6821
kuribo is offline kuribo
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Quote:
Originally Posted by ynmichael View Post
The same problem with random delays in acquiring lock among the boards exist in your case. An official answer from Soren is probably needed.

You would have the peace of mind if you could work with dam1121, but it requires more work and is more fragile.
Yes, exactly my concerns. Soren said originally that it would work, which is why I went ahead and ordered 4 boards. There was a manual promised which I expected to address the issue. All we have been told is to split the signal between the boards. No subsequent confirmation anywhere that it actually works. Before I actually spend all the money on all the power supplies, etc. and all the time to put it together, I would like to know if it will work as promised without delay and other issues.
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Old 30th December 2017, 02:02 PM   #6822
ynmichael is offline ynmichael
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Originally Posted by kuribo View Post
Yes, exactly my concerns. Soren said originally that it would work, which is why I went ahead and ordered 4 boards. There was a manual promised which I expected to address the issue. All we have been told is to split the signal between the boards. No subsequent confirmation anywhere that it actually works. Before I actually spend all the money on all the power supplies, etc. and all the time to put it together, I would like to know if it will work as promised without delay and other issues.
If you have the 1121 I'm certain you could sync them using one clock internal or external. If you have the 1021, I did see somewhere Soren comment that it will have a max of several micro seconds in delay. He has not commented since.

Practically speaking, if you're using speakers in dual-mono, I don't see a problem with a few us of delay (mm in phase difference). But if you're using 4 channels (not sure why you would do that but anyways...), you need to consider the impact of the us level delay. If you're stacking 2 boards per channel in a balanced build, that could be a large problem imho.

I have 2 boards and am looking for an answer too...
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Old 30th December 2017, 02:04 PM   #6823
TNT is offline TNT  Sweden
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Why would you stack 2 boards for 1 channel?

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Old 30th December 2017, 02:27 PM   #6824
ynmichael is offline ynmichael
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Originally Posted by TNT View Post
Why would you stack 2 boards for 1 channel?

//
To copy MSB and totaldac's approach? Increase SNR the old fashioned way - spend more money...... It also has the added benefit of decreased output impedance. So if one stack, say, 3 ladders per signal channel (Totaldac d1 12?), you would get a third of the output impedance At some point you would not need a buffer any more, like MSB...

Also, I went through a lot more posts than I thought existed and found crazy mods like this: Soekris DAC with comprehensive guide on how to remove everything on the dam1021 and replace it with batteries instead...

And this: Сергей Шалаев - Моя поделка.
На выходных запустили мою... | Facebook
Russians win...

So perhaps I was wrong about 2 board per channel not feasible with dam1021...

Last edited by ynmichael; 30th December 2017 at 02:52 PM.
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Old 30th December 2017, 02:55 PM   #6825
soekris is offline soekris  Denmark
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Multiple boards: The dam1121 can be connected synchronous, the dam1021 can be connected asynchronous, but will sync to within a few uS, not something you can hear.

Fully Balanced: Can be used for the dam1021 and dam1121, a mode setting in uManager on dam1021 and a hardware setting on dam1121. Several people have done that successfully, search thread for details.

Paralleling multiple boards: Easy with the dam1121, probably fine with dam1021 unbuffered, not recommended using the dam1021 buffers.

As crossover: the dam1021/dam1121 have the hardware with support for up to 15 IIR biquad filters per board. How to do it is an advanced DIY project, not something I will provide support for. Probably much easier using a DSP....
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Last edited by soekris; 30th December 2017 at 02:57 PM.
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Old 30th December 2017, 03:13 PM   #6826
ynmichael is offline ynmichael
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After some more browsing... it seems that spikestabber had a similar question of whether to bridge the buffered outs in balanced mode. He resorted to a discrete head-amp board but the question is still relevant...

I'm guessing that bridging/paralleling the 2 signals of the same polarity would not introduce more noise. Quite the opposite, the noise from each signal would find its opposite in the other channel, canceling each other out. There might also be minor SNR improvements although the opamp buffer has no doubt deteriorated the signal to begin with...

----------------------------------------------------------------

On a completely different note, I also became a bit worried over how the dam1021 is powered by default due to the lack of a full understanding...

The digital parts, e.g. FPGA, oscillator, (?), are powered by the positive rail, whereas the opamps in the vref and the opamps in the buffer stage use both positive and negative rails. My worry stems from the common belief that digital and analogue must not share power source for best performance (perhaps to reduce noise interference in between the two?). After seeing that dam1121 offers three power in: 5V digital x2, and 5V analogue, I became more worried that a single set of DC input is insufficient even for folks who aren't going all out with batteries and external regulators.

Therefore, the questions are: (1) do we need separation of power source in this system (2) if we do, how can we mod the board to meet the requirements. If we still plan on using the opamp buffers (like I do..) we would need to keep the two rails powered as it is, without skipping to after the 5V regs perhaps. Then how are we to separate the digital power from the two rails?...

We could always go this route: randytsuch's audio page: Soekris R2R Dam Dac - Modding and forget about separation as we would basically have an independent power source for every major component... but short of that, do we have options?

------------------------------------------------------------

Also, Soren did say with high if not absolute certainty that the vref on the V4 boards is better than any external regulators. If this were true, and I tend to believe Soren's judgement here, then what else can we really plausibly improve on the dam1021 with our caps and regs? I noticed that spikestabber reported noticeable improvement in bass clarity etc. with A-B tests on the 3.3V reg upgrade for the oscillator. Is there a contradiction here or is there only the appearance of one?

Again any comments/discussions would be very helpful.
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Old 30th December 2017, 03:19 PM   #6827
ynmichael is offline ynmichael
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Quote:
Originally Posted by soekris View Post
Multiple boards: The dam1121 can be connected synchronous, the dam1021 can be connected asynchronous, but will sync to within a few uS, not something you can hear.

Fully Balanced: Can be used for the dam1021 and dam1121, a mode setting in uManager on dam1021 and a hardware setting on dam1121. Several people have done that successfully, search thread for details.

Paralleling multiple boards: Easy with the dam1121, probably fine with dam1021 unbuffered, not recommended using the dam1021 buffers.

As crossover: the dam1021/dam1121 have the hardware with support for up to 15 IIR biquad filters per board. How to do it is an advanced DIY project, not something I will provide support for. Probably much easier using a DSP....
Thanks and great to hear from you again Soren! I'll just use 2 dam1021 asynchronously and forget about the delay

In terms of paralleling, I understand that more than 2 boards would not be ideal for dam1021, but would paralleling the buffered outputs in a fully balanced setup be a good idea in terms of noise and output impedance? I.e. positive from BAL-L board left channel paralleled with negative from BAL-L board right channel to power headphones?

Thanks again!
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Old 30th December 2017, 03:28 PM   #6828
soekris is offline soekris  Denmark
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Quote:
Originally Posted by ynmichael View Post
Thanks and great to hear from you again Soren! I'll just use 2 dam1021 asynchronously and forget about the delay

In terms of paralleling, I understand that more than 2 boards would not be ideal for dam1021, but would paralleling the buffered outputs in a fully balanced setup be a good idea in terms of noise and output impedance? I.e. positive from BAL-L board left channel paralleled with negative from BAL-L board right channel to power headphones?

Thanks again!
As I said, not recommended paralleling using the dam1021 buffers.

The levels are set by a 0.5% reference and a number of 0.5% resistors, so the voltage levels might have a too large difference to just parallel the output buffer, even as the buffer have those 10R series resistors.

The noise is already very very low.
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Old 30th December 2017, 03:35 PM   #6829
ynmichael is offline ynmichael
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Quote:
Originally Posted by soekris View Post
As I said, not recommended paralleling using the dam1021 buffers.

The levels are set by a 0.5% reference and a number of 0.5% resistors, so the voltage levels might have a too large difference to just parallel the output buffer, even as the buffer have those 10R series resistors.

The noise is already very very low.
Thanks! I would definitely not want to short my boards this way... This really put an end to the age-old discussion!

Just a quick question while you're here, how much of an improvement would a fully discrete solid state pre-amp / head-amp be over the 0.5% parts used currently...? And could we expect such a fine add-on to be coming soon?...

Also, any comments on the digital/analogue separation in dam1021?...

Thanks for the great product as is!
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Old 30th December 2017, 03:59 PM   #6830
TNT is offline TNT  Sweden
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Quote:
Originally Posted by soekris View Post
As crossover: the dam1021/dam1121 have the hardware with support for up to 15 IIR biquad filters per board. How to do it is an advanced DIY project, not something I will provide support for. Probably much easier using a DSP....
Is all the information/prerequisites described in the manuals to really pull this off?

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