Anybody using the new ESS Vout DAC (ES9022)? - Page 56 - diyAudio
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Old 21st February 2013, 11:18 AM   #551
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Yes I've heard very positive feedback from a listener to the filter, so yes its definitely working.

To model an opamp output there's the open loop output impedance (which might indeed be around 200R or so for a CMOS opamp) at the unity gain frequency (probably 10MHz or so) and then this goes down with decreasing frequency so at 10kHz it might be 0.2ohm. The overall effect I'll try with an inductor for Zout in parallel with the 240R and also taking out the 40R now I'm slowly getting up to speed

<edit> The new inductor turns out around 3uH with my estimates and the plot is here - problematic is the ringing above 1MHz.
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File Type: png JGundamped.png (8.0 KB, 642 views)
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Last edited by abraxalito; 21st February 2013 at 11:26 AM. Reason: Added sim result
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Old 21st February 2013, 11:52 AM   #552
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Here's how it looks with two real resistors added - a 150ohm between the DAC and the 4n7, and a 47k across the inductor. Damping the inductor in this way makes variations in its value relatively inconsequential so there won't be a need to pre-select parts.
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File Type: png JGdamped.png (6.2 KB, 638 views)
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Old 21st February 2013, 12:35 PM   #553
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Thanks!

AFAIK 240 Ohm is the output impedance of the ES9023 as specified by ESS-tech in the audio band (eventually plus your 0.2 Ohm from the opamp itself). Probably a series resistor to protect the output and avoid load influences.

Can you perform another sim with 240 instead of 150 Ohm?
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Old 21st February 2013, 12:59 PM   #554
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OK then assuming the 240R is a real resistance in series with the opamp output here is how it looks (47k inductor damping resistor still in circuit) :

Inductor peaking is about 1.2dB at 70kHz quite benign. Second plot shows how it looks without the 47k - almost 3dB peaking.
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File Type: png JGdamped240Rand47k.png (5.8 KB, 629 views)
File Type: png JGundamped240R.png (7.2 KB, 620 views)
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Last edited by abraxalito; 21st February 2013 at 01:06 PM.
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Old 21st February 2013, 01:23 PM   #555
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Just for the sake of completeness, here's what happens to the FR when the inductor (with damping) is changed down to 15mH and up to 22mH - zero audible change to the audio band response - well under 0.1dB difference at 20kHz.

<edit> Please note this does not mean you can change the nominal inductor value and get no difference - this is just to show the effects of 20%-ish tolerance on the 18mH value specified.
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Last edited by abraxalito; 21st February 2013 at 01:33 PM.
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Old 21st February 2013, 01:29 PM   #556
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Many thanks! So I can leave my simulator in the pocket this evening and concentrate on transistor matching ;-)
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Old 21st February 2013, 05:02 PM   #557
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Default Coilcraft DCR 47-17 = 30 40R-30=10R...or not

Quote:
Originally Posted by abraxalito View Post
Here's how it looks with two real resistors added - a 150ohm between the DAC and the 4n7, and a 47k across the inductor. Damping the inductor in this way makes variations in its value relatively inconsequential so there won't be a need to pre-select parts.
So if Coilcraft DCR stays at 47, minus the 17 of the 07MFG Fastron, that's 30 Ohms... and the JG schematic calls for 40 just before the 07MFG coil as I recall.. not meaning to put you out, would I just plunk in 10 ohms series before the Coilcraft -- or just ES9023 DAC -> 150R {or 240} 4.7n to ground, 47DCR/18.7MH w/ 47K parallel, 18.##K to ground...etc? I feel like it must be "close".

Someone uttered OP AMP? Once I decided I must try this, I had impure thoughts about tubes, and wondered what of all the tube circuits is like the buffer stage? [I have 6088, 6021, 6n16b-v 6n1p, 2p, 3p, 6p...12Au7, 6sn7, and the cute Mickey Mouse-like single triode: 7193...] . I was about ready to make the Broskie Unbalancer with 6n16b-v x 4 when I discovered I like the ES9023 which is already single-ended, defeating the purpose of the Unbalancer, though one differential cap-free input could simply be grounded. I have the PCB but that seems complex for the task {and has excess gain to dump later} Pondering this I think it would be a circuit that would NOT have a series CAP at it's input? And SIMPLE, maybe 12-24-30V plate. {no more complex than PSU for the FETs} No flames please, I just like the glow of a valve. I'll try something off_line "in my spare time".
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Old 21st February 2013, 07:24 PM   #558
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Quote:
Originally Posted by enjoybiking View Post
So if Coilcraft DCR stays at 47, minus the 17 of the 07MFG Fastron, that's 30 Ohms... and the JG schematic calls for 40 just before the 07MFG coil as I recall.. not meaning to put you out, would I just plunk in 10 ohms series before the Coilcraft -- or just ES9023 DAC -> 150R {or 240} 4.7n to ground, 47DCR/18.7MH w/ 47K parallel, 18.##K to ground...etc? I feel like it must be "close".
Seems you are a bit confused

As a result of the simulations: you don't have to worry at all about the coils DCR and you don't need to add a series resistor there. The 40 Ohm in the original schematic just represents the (estimated) DCR of an arbitrary coil for the initial development of the circuit. However as abraxalito pointed out the influence of a different DCR is almost neglegible.
The same for the 240 Ohm series resitor in the original schematic: it just represents the output impedance of the ES9023. You don't have to add an additional resistor here
And finally the filter does not react too much on a varying inductance. E.g. between 15 and 22mH the influence is quite small. Matching between stereo channels still seems to make sense.

Best regards, Daniel
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Old 21st February 2013, 08:16 PM   #559
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Default Confused no more. +47K then PAR

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Originally Posted by curryman View Post
Seems you are a bit confused

As a result of the simulations: you don't have to worry at all about the coils DCR
-snip-
And finally the filter does not react too much on a varying inductance. E.g. between 15 and 22mH the influence is quite small. Matching between stereo channels still seems to make sense.
Best regards, Daniel
So ES9023 -> 4.7nF to GND to 47K in Parallel with the {matched} coil, 18.9K to GND...470R 150P to GND. Z-in of actual buffer is probably hiding in the above thread. Impure thoughts <deleted>.

Now, a slight reason for my confusion is ODAC uses some R there after the DAC I think 220.

Thanks for setting me straight!!

{The Other Pat}
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Old 27th February 2013, 04:30 PM   #560
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Sorry for jumping in like this,is there a pcb with ES9022?
What is the difference between ES9022 and ES9023?
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