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ES9018K2M, ES9028Q2M, 9038Q2M DSD/I2S DAC HATs for Raspberry Pi
ES9018K2M, ES9028Q2M, 9038Q2M DSD/I2S DAC HATs for Raspberry Pi
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Old 13th March 2018, 08:57 AM   #151
Rod Coleman is offline Rod Coleman  United Kingdom
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ES9018K2M, ES9028Q2M, 9038Q2M DSD/I2S DAC HATs for Raspberry Pi
Yes, I use a capacitor directly after the DAC as well.

I don't believe that it is doing anything magic, but rather it acts as a functional low-pass filter to remove the very high-bandwidth transition artefacts generated at sample boundaries.

These transition are likely to extend into the 10s of MHz region, or even higher, and may well cause problems with op-amps in the I/V or any subsequent gain stages.

The need for such a filter was explained at least 20 years ago by the famous Dr Hawksford:

Dr MOJ Hawksford -Transimpedance Amplifiers

See section 5, page 21

On account of the bandwidth, the capacitor used in this position should be a surface mount type. The leads and general construction of through-hole caps will have enough inductance to impair the filtering at such high frequencies.

22-100nF are easily available in C0G 1206 ceramic caps, and these would seem to be first choice, although the polyphenylene sulphide [PPS] dielectric of the Panasonic ECHU (surface mount) series are also worth trying. Both of these should be soldered with extreme care, if using an iron - the damage caused by overheating is not easily visible.
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Old 13th March 2018, 09:07 AM   #152
androa76 is offline androa76  Slovenia
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Are there any cheaper alternatives on the market for ll1544A...from Neutrik, Monacor, ebay... Amorphus, Mumetal ...?
Madds1...i agree with your conclussions...i also found that es9018 is playing more analogue with (Rasmussen) filter cap...and that some second harmonics have influence on sound perspective...
With AK dacs it is not necessary because they are more damped inside dac Ic and noise is muuuch smaller on output of the AK vs ES dac. (and are voltage not current dacs) I think that too much digital noise coming in first filter opamp kill the dynamics, freedom, natural big soundstage...

Last edited by androa76; 13th March 2018 at 09:14 AM.
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Old 13th March 2018, 01:28 PM   #153
bisesik is offline bisesik  Kazakhstan
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Hello Ian, hello guys! I am very happy to know about Ian's new project. And it is about DAC this time! Cheers!
Regarding transformers available for ES90xx DACs outputs... For now it is totally finished the job of matching nano-crystalline-core transformers with ES90xx outputs. Schematic is similiar to madds1' (ratio is 1:3.5), but due to better ratio of inductance to coil-resistance in comparison with specs of any other available transfomers on the market, I get 2.6VRMS without any resistor across the primary coil. Moreover, the cost is much lower than that of brands.
Of course I will try yours DAC implementation on my table later, so I am in the list
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Old 13th March 2018, 03:07 PM   #154
madds1 is offline madds1
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Quote:
Originally Posted by iancanada View Post
Hi madds1,

That's very helpful. Thank you so much.

It seem's I should buy a pair of LL1544A to give it a try. I mainly use balanced output, is there any problem?

I still have some PCB available for the transformer I/V. I'd be very happy to share with you if you want to try something on it. DAC will be available later. Please let me know.

Regards,
Ian
PMed you separately.

You should be able to use any transformer with shielding pins for balanced output. Ensure that that the ground of the DAC board is connected to the shield which should then be connected to the chassis ground of the preamp

Cheers
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Old 13th March 2018, 03:31 PM   #155
madds1 is offline madds1
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Quote:
Originally Posted by Rod Coleman View Post
Yes, I use a capacitor directly after the DAC as well.

I don't believe that it is doing anything magic, but rather it acts as a functional low-pass filter to remove the very high-bandwidth transition artefacts generated at sample boundaries.

These transition are likely to extend into the 10s of MHz region, or even higher, and may well cause problems with op-amps in the I/V or any subsequent gain stages.

The need for such a filter was explained at least 20 years ago by the famous Dr Hawksford:

Dr MOJ Hawksford -Transimpedance Amplifiers

See section 5, page 21

On account of the bandwidth, the capacitor used in this position should be a surface mount type. The leads and general construction of through-hole caps will have enough inductance to impair the filtering at such high frequencies.

22-100nF are easily available in C0G 1206 ceramic caps, and these would seem to be first choice, although the polyphenylene sulphide [PPS] dielectric of the Panasonic ECHU (surface mount) series are also worth trying. Both of these should be soldered with extreme care, if using an iron - the damage caused by overheating is not easily visible.
Hi Rod

I thought so too initially that there was the HF explanation but there is some other mystery to be solved as well. Specifically - if you ground the caps, the effect is gone. In other words if you replace the 47nf across the pins with 94nf to the ground from each leg - the layering of instruments and the emotional connection is lost.

Also - if you vary the 3db corner - i.e. move it to say 30Khz - the effect is gone. It only seems to near the 20-22Khz region. I settled on 19.9 corner for my system. See this post. Other has have the same experience as well

Oppo's BDP105 - discussions, upgrading, mods...

Joe tried to seek an explanation of this phenomena this thread but it didn't go anywhere

DAC Filtering - the "Rasmussen Effect"

He again tried nearly a year later and failed again

Practical Implementations of Alternative Post-DAC Filtering

Whatever the phenomena is - the music is more enjoyable :-)

Regards
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Old 13th March 2018, 04:07 PM   #156
madds1 is offline madds1
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Quote:
Originally Posted by androa76 View Post
Are there any cheaper alternatives on the market for ll1544A...from Neutrik, Monacor, ebay... Amorphus, Mumetal ...?
Madds1...i agree with your conclussions...i also found that es9018 is playing more analogue with (Rasmussen) filter cap...and that some second harmonics have influence on sound perspective...
With AK dacs it is not necessary because they are more damped inside dac Ic and noise is muuuch smaller on output of the AK vs ES dac. (and are voltage not current dacs) I think that too much digital noise coming in first filter opamp kill the dynamics, freedom, natural big soundstage...
Completely agree. It is not required (and does not work as effectively) with AK DACs

So regarding transformers. Three things matter. Core, Winding and Structure. The core material determines 2nd and 3rd harmonics ratios relative to the amplitude, primarily because of the hysteresis curve. I used amorphous core since it had the least amount of artifacts at the 1V RMS. If your preamp and amp are low distortion then you can experiment with EDCOR (Steel Laminate) or Jensen (best mu-metal out there). Haven't tried anything else

In my system - the only place where color and warmth are introduced is at the preamp stage where I deliberately introduce in phase 2nd and 4th harmonics.The reason I do this is because of the open baffle nature of my Magneplanars. I prefer that it have asymmetric radiation. It also helps with improving dynamics since amplification follows a square law.

You can use the transformer to generate in phase 2nd and 3rd harmonics (symmetrical hysteresis curves generate both) and it may suit some systems

So core choice is very dependent on you overall system

Windings - these mostly influence low level detail retrieval. Lundahls, Jensens, Sowters etc are tightly wound. I would stick with Lundhals (price performance)

Structure primarily determines magnetic leakage or interference. Most audio transformers have a shield

In short - hard to find a transformer that can beat LL1545A or LL1544A for the price.

If you like the transformer effect in you system - use LL1545A (mu-metal) or any other brand. If the transformer is simply to sum the diff output - use amorphous core (affordable) or FineMET (ridiculously expensive - see)

If you don't care for summing the diff output - simply put a cap across the outputs. That is what Barbara does

http://web12491.serv4.spacequadrat.d...ro_DAB_V10.pdf


Regards
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Old 13th March 2018, 06:06 PM   #157
Rod Coleman is offline Rod Coleman  United Kingdom
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ES9018K2M, ES9028Q2M, 9038Q2M DSD/I2S DAC HATs for Raspberry Pi
Quote:
Originally Posted by madds1 View Post
Hi Rod

I thought so too initially that there was the HF explanation but there is some other mystery to be solved as well. Specifically - if you ground the caps, the effect is gone. In other words if you replace the 47nf across the pins with 94nf to the ground from each leg - the layering of instruments and the emotional connection is lost.

Also - if you vary the 3db corner - i.e. move it to say 30Khz - the effect is gone. It only seems to near the 20-22Khz region. I settled on 19.9 corner for my system. See this post. Other has have the same experience as well

Oppo's BDP105 - discussions, upgrading, mods...

Joe tried to seek an explanation of this phenomena this thread but it didn't go anywhere

DAC Filtering - the "Rasmussen Effect"

He again tried nearly a year later and failed again

Practical Implementations of Alternative Post-DAC Filtering

Whatever the phenomena is - the music is more enjoyable :-)

Regards
Yes, I did see that thread and have thought about it from time to time.

But one thing can be cleared up immediately: if you connect the capacitors to ground, I would expect a degradation of the sound.

Why? because connecting them to ground will cause the noise-currents to circulate into ground and contaminate some of the most sensitive nodes in the whole playback chain.
The bandwidth of the noise can reach into the VHF region, and it will not follow the paths that you intended!

The best to deal with this noise is to connect the cap across the DAC-out phase and anti-phase, which gives the best chance of a short and direct path for the currents.

Beyond that, anything that increases enjoyment should naturally be put to use
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Old 13th March 2018, 06:34 PM   #158
madds1 is offline madds1
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You are absolutely correct. I don't know how that didn't occur to me at all. No wonder Barbara in the Nitro DAB uses hand wound (5 turns around a pencil) inductor to connect the digital and analog grounds!

All this chat has made me wonder if I should simply uses Barbara's DAB design (skip transformers). The only reason I using transformers is to get back the 2V RMS, sum the outputs and finally be able to use diff or single ended in the future for experiments

But over the years I have settled on single ended. The noise floor in my system at listening levels is easily at -100db. Time to try retiring the transformers :-)
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Old 16th March 2018, 01:24 AM   #159
iancanada is offline iancanada  Canada
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ES9018K2M, ES9028Q2M, 9038Q2M DSD/I2S DAC HATs for Raspberry Pi
Quote:
Originally Posted by madds1 View Post
At work so I just drew it up to give you an idea.
I'll build an LL1544A transformer I/V based on your schematic. My LL1674 were ordered from KK. Very nice guy. Do you have some details with pin numbers?

Regards,
Ian
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Old 16th March 2018, 01:25 AM   #160
iancanada is offline iancanada  Canada
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ES9018K2M, ES9028Q2M, 9038Q2M DSD/I2S DAC HATs for Raspberry Pi
Quote:
Originally Posted by Rod Coleman View Post
Yes, I did see that thread and have thought about it from time to time.

But one thing can be cleared up immediately: if you connect the capacitors to ground, I would expect a degradation of the sound.

Why? because connecting them to ground will cause the noise-currents to circulate into ground and contaminate some of the most sensitive nodes in the whole playback chain.
The bandwidth of the noise can reach into the VHF region, and it will not follow the paths that you intended!

The best to deal with this noise is to connect the cap across the DAC-out phase and anti-phase, which gives the best chance of a short and direct path for the currents.

Beyond that, anything that increases enjoyment should naturally be put to use
Make sense
Ian
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