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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 12th March 2018, 04:18 PM   #141
madds1 is offline madds1
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Ian

Just found this thread

I have been using LL1545A for a quite sometime now and I can confirm that 1:4 Amorphous core with a Sabre loaded with an impedance slightly less than the output impedance of the DAC sounds the best. I have tried tubes, opamps, direct out etc.

The one thing that I found better than the cap connected to the ground to sink asymmetrical noise, is a cap across the legs.

For my Buffalo II dad (ES9018) - I have an effective impedance of 303 ohms across the legs shunted by a silver mica 47nf creating a 3db at 20Khz.

So in my implementation I chose to not use the central tap the transformer at all. I have a single 390 ohm wire wound resistor across the legs (303 ohms with the reflected secondary impedance from the 22k preamp pot i.e. reflected is 22k/16 with a 1:4 gain)

Best probably is to have both caps. The cap in the center like you have plus a silver mica or a really good shunt poly cap across the legs resulting in a 20K-22k 3db pt (depending on your tweeter). I haven't tried yet.

If you have time - you should try it shunting the legs too. That made the most difference to the depth and emotional content of the music. Much more than the cap at the central tap.
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Old 12th March 2018, 04:43 PM   #142
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
Ian

Just found this thread

I have been using LL1545A for a quite sometime now and I can confirm that 1:4 Amorphous core with a Sabre loaded with an impedance slightly less than the output impedance of the DAC sounds the best. I have tried tubes, opamps, direct out etc.

The one thing that I found better than the cap connected to the ground to sink asymmetrical noise, is a cap across the legs.

For my Buffalo II dad (ES9018) - I have an effective impedance of 303 ohms across the legs shunted by a silver mica 47nf creating a 3db at 20Khz.

So in my implementation I chose to not use the central tap the transformer at all. I have a single 390 ohm wire wound resistor across the legs (303 ohms with the reflected secondary impedance from the 22k preamp pot i.e. reflected is 22k/16 with a 1:4 gain)

Best probably is to have both caps. The cap in the center like you have plus a silver mica or a really good shunt poly cap across the legs resulting in a 20K-22k 3db pt (depending on your tweeter). I haven't tried yet.

If you have time - you should try it shunting the legs too. That made the most difference to the depth and emotional content of the music. Much more than the cap at the central tap.
Thanks madds1,

That's great. Do you have some details with schematic?

Regards,
Ian
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Old 12th March 2018, 06:17 PM   #143
madds1 is offline madds1
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At work so I just drew it up to give you an idea.
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Old 12th March 2018, 07:40 PM   #144
madds1 is offline madds1
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The drawing and the my post above say LL1545A. Thats a mu-metal transformer. The one I like better than that one is 1544A which is amorphous. That is what I am using. Apologies for the confusion

As an aside - mu-metal core sounds thicker and has more body than the amorphous cores. Slightly less details
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Old 12th March 2018, 08:24 PM   #145
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.
Thanks madds1, you approach looks nice. What's that 47n cap for? Dose it improve sound quality? what kind of cap did you use?

Both your LL1544A and my LL1674 are amorphous, right?

For ES9018 DAC stereo configuration, the internal resistance is 195 ohm. while ES9028Q2M is 403 ohm, ES9038Q2M and ES9018K2M are around 800ohm. So, the 390 ohm resistor need to be increased I think?

BTW, what kind of resistor did you use? Does it affect sound quality much in your test?

Regards,
Ian
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Old 12th March 2018, 08:59 PM   #146
madds1 is offline madds1
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Quote:
Originally Posted by iancanada View Post
Thanks madds1, you approach looks nice. What's that 47n cap for? Dose it improve sound quality? what kind of cap did you use?

Both your LL1544A and my LL1674 are amorphous, right?

For ES9018 DAC stereo configuration, the internal resistance is 195 ohm. while ES9028Q2M is 403 ohm, ES9038Q2M and ES9018K2M are around 800ohm. So, the 390 ohm resistor need to be increased I think?

BTW, what kind of resistor did you use? Does it affect sound quality much in your test?

Regards,
Ian
The 47nf cap creates a corner 3db point of 23K without the preamp secondary impedance reflected to the primaries and 20K with it reflected. But that is not the reason why I have the cap. I discovered the effect of a cap across the legs on sigma delta DACs nearly 3 years ago by accident. I reported in the these posts

Practical Implementations of Alternative Post-DAC Filtering

Practical Implementations of Alternative Post-DAC Filtering

That thread was started by a member who also noticed the same effect. He unfortunately got flamed for reporting it without adequate explanation. The effect is that is creates is a layering of instruments that makes listening to music - emotional.

The oldest reference I can find to this effect is here

http://www.raylectronics.nl/pdfs/Mau...6367_tweak.pdf

Regarding the transformers - yes LL1544A is amorphous too. Nearly $85 in the US vs LL1674 which is $130

The resistor value to be chosen depends on your taste. Put simply - the deeper you put the DAC into current mode (by lowering the resistor) - the THD improves. At 0 ohms - the THD is the best.

But in all honestly - I can't hear THD in my system below -105db.

But I what I can hear is that the slam/attack/dynamics are lost deeper in the current mode.

The optimal value for the resistor is 4/5 times the output impedance of the DAC for my system. So 640 ohms for ES9028Q2M.

I have a modified IRAUDAMP7S driving a highly modded Magnepan 1.7. Preamp is a poorly biased JFET that creates a 2nd order harmonic at nearly -80db. I have been told 2nd harmonics change the tone but I perceive it more as body to the music. LPs naturally had this and Tapes had tons of 3rd harmonics

Sorry for the long reply. Hope this helps

Last edited by madds1; 12th March 2018 at 09:02 PM.
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Old 12th March 2018, 09:25 PM   #147
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
The 47nf cap creates a corner 3db point of 23K without the preamp secondary impedance reflected to the primaries and 20K with it reflected. But that is not the reason why I have the cap. I discovered the effect of a cap across the legs on sigma delta DACs nearly 3 years ago by accident. I reported in the these posts

Practical Implementations of Alternative Post-DAC Filtering

Practical Implementations of Alternative Post-DAC Filtering

That thread was started by a member who also noticed the same effect. He unfortunately got flamed for reporting it without adequate explanation. The effect is that is creates is a layering of instruments that makes listening to music - emotional.

The oldest reference I can find to this effect is here

http://www.raylectronics.nl/pdfs/Mau...6367_tweak.pdf

Regarding the transformers - yes LL1544A is amorphous too. Nearly $85 in the US vs LL1674 which is $130

The resistor value to be chosen depends on your taste. Put simply - the deeper you put the DAC into current mode (by lowering the resistor) - the THD improves. At 0 ohms - the THD is the best.

But in all honestly - I can't hear THD in my system below -105db.

But I what I can hear is that the slam/attack/dynamics are lost deeper in the current mode.

The optimal value for the resistor is 4/5 times the output impedance of the DAC for my system. So 640 ohms for ES9028Q2M.

I have a modified IRAUDAMP7S driving a highly modded Magnepan 1.7. Preamp is a poorly biased JFET that creates a 2nd order harmonic at nearly -80db. I have been told 2nd harmonics change the tone but I perceive it more as body to the music. LPs naturally had this and Tapes had tons of 3rd harmonics

Sorry for the long reply. Hope this helps
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
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Old 12th March 2018, 10:15 PM   #148
markusA is offline markusA  Sweden
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Madds idea is pretty much what Iíve been talking about.
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Current build to be found in my blog. Not so current anymore, everything is put on hold until march.
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Old 13th March 2018, 03:46 AM   #149
iancanada is offline iancanada  Canada
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ES9018K2M, ES9028Q2M, 9038Q2M DSD/I2S DAC HATs for Raspberry Pi
Quote:
Originally Posted by ChuckT View Post
Just wondering if the cap to ground really necessary?
I have a LL1636 , tried 2 x 10ohm to ground on primary. But output is too low. I will try a higher resistor value later.
Hi ChuckT,

The capacitor is for the visual ground. Theoretically you can remove it. The only thing I'm bit worry about is that in the real world the two windings can not be 100% balanced. So the center may have some floating voltage. Please
see madds1's implement for reference:

ES9018K2M, ES9028Q2M, 9038Q2M DSD/I2S DAC HATs for Raspberry Pi

Please let me know your result if you have any.

Regards,
Ian

Last edited by iancanada; 13th March 2018 at 03:49 AM.
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Old 13th March 2018, 07:39 AM   #150
ChuckT is offline ChuckT
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Quote:
Originally Posted by iancanada View Post
Hi ChuckT,

The capacitor is for the visual ground. Theoretically you can remove it. The only thing I'm bit worry about is that in the real world the two windings can not be 100% balanced. So the center may have some floating voltage. Please
see madds1's implement for reference:

ES9018K2M, ES9028Q2M, 9038Q2M DSD/I2S DAC HATs for Raspberry Pi

Please let me know your result if you have any.

Regards,
Ian
I think Madds1 circuit is voltage mode? While with low value resistor to ground will run dac in current mode.
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