Joachim Gerhard Filter Buffer for ES9022 - Page 45 - diyAudio
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Old 25th January 2013, 03:47 AM   #441
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Quote:
Originally Posted by qusp View Post
why? any decent IV would remove the need for the filter/buffer, so you would be just adding noise, THD and complexity.

not because its a bad design, it isnt, but because its extraneous circuitry and anything added after whats needed adds noise, THD etc.
I was mostly pointing out that I would rather have an active IV, which may or may not include a filter in its design and use this filter/buffer to provide that function vs the option of using this filter/buffer directly on the output pins of the DAC. I agree the complexity is unnecessary in many cases and that modifying the filter in the IV makes more sense. But, it is still a valid option that could be tried.

I was mostly pointing out that the additional THD/Noise/complexity of the extra filter/buffer IMO is still a better option that trying to drive this filter/buffer with current out DAC...
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Old 25th January 2013, 03:55 AM   #442
EUVL is offline EUVL  Europe
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Do you have any idea what the THD or noise is for this passive filter and the cascode source follower circuit in the audio band ?

We don't.
We cannot measure anything with a HP339, so we have to send one to the States to measure down to -120dB.

And those who actually built the circuit seemed to agree it is worth the additional THD & noise, whatever it is :
Joachim Gerhard Filter Buffer for ES9022


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Last edited by EUVL; 25th January 2013 at 04:00 AM.
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Old 25th January 2013, 04:51 AM   #443
qusp is offline qusp  Australia
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Patrick, its not a miracle filter, it adds THD, no matter how little.

There is no need to get defensive, I did not at any point criticize the circuit, I think for its purpose its very good indeed, but its IMO superfluous to add after an IV, which should already include a filter. it also adds expense, another set of power supplies etc etc, which are all IMO a waste and add complexity to what should be a pretty simple and for my taste minimal circuit. In fact it would seem against your very own ethos to add complexity where its not called for.
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Old 25th January 2013, 05:09 AM   #444
EUVL is offline EUVL  Europe
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> In fact it would seem against your very own ethos to add complexity where its not called for.

Indeed.

And we don't hesitate to add complexity if it brings benefits.
And we know, because we built, tested and listened first.


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Old 25th January 2013, 10:02 PM   #445
acko is offline acko  Australia
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Originally Posted by EUVL View Post
You choice.

I personally like passive filters, as Joachim is using here.


Patrick
Quite agree, best to keep things passive

...and if you are driving a high impedance stage like headphone amps or short interconnect cables to other buffer/amps you can do away with the on-board FET buffer.
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Old 26th January 2013, 04:26 AM   #446
qusp is offline qusp  Australia
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i'm quite amazed at the lack of understanding here, I thought I was pretty clear I was not talking about the es9023, we never have been. we have been talking about adding or modifying an existing filter as part of an IV stage, instead of adding an entire second board and more power supplies just to add a passive filter.

My assertion was simply that any decent IV stage worth its salt should optionally include the filter, which you can populate or not. that filter could if you so desire, be exactly as the passive filter here... adding an entire second board with its own power supplies and a further buffer WILL add noise and distortion in the pass-band, it may/will attenuate that outside of the pass-band if there is anything there, thats its job, but its no different to what can be done as part of the basic IV design.

myself I leave it unpopulated on mine now, but the option is there if I wish to play with it again; perhaps when I can reliably measure less than -115dB THD+N.

it was shown, with the type of measurement gear you dont have yourself Patrick, to be of no real (worthwhile) benefit in the case of the NTD1, as performance was already at the boundaries of the audio precision system 2 (well not quite, but you know what I mean).

adding a further buffer and filter after such a design, no matter how good it is (and as ive said, this is obviously VERY good) will lower performance, perhaps you may tune it subjectively to taste, but adding negative noise and negative distortion in the pass band is impossible, by adding active and passive parts in series with the output

Last edited by qusp; 26th January 2013 at 04:37 AM.
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Old 26th January 2013, 04:34 AM   #447
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its like saying we could lower noise in the pass band by adding another filter/buffer after the filter/buffer
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Old 26th January 2013, 04:43 AM   #448
EUVL is offline EUVL  Europe
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And of course you also know what equipment the xen team has.
And you have listened to Joachim's buffer or a similar circuit and concluded that it is not worth the trouble.

If so, I have no problems.
You are of course entitled to your opinion. This is an open forum.
I am also entitled to mine.
And I think Joachim has given us a worthwhile addition which I also use for the likes of PCM5102 and AK4430.


Cheers,
Patrick
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Last edited by EUVL; 26th January 2013 at 05:10 AM.
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Old 26th January 2013, 06:50 AM   #449
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what Is fc of that filter
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Old 26th January 2013, 10:19 AM   #450
shoom is offline shoom  Europe
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''And I think Joachim has given us a worthwhile addition which I also use for the likes of PCM5102 and AK4430.''

And that's exactly what I have in mind for my second filter buffer.

In my opinion the 9023 and PCM5102 struggle a little driving high capacitive loads (yes Iíve found them both to be very cable sensitive).

Thatís why Iíve used other buffers in the past with both of these DACs.

The buffer seems to sort that out quite nicely along with the other benefits Iíve mentioned in previous posts that the filter brings.

Others may have a different take but thatís DIY.

With my 9023 Joachim's filter buffer sounds great in my system and to my ears.

Iím looking forward to trying the filter buffer with my DIY PCM5102.
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