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Old 11th June 2012, 03:15 PM   #881
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by EUVL View Post
Xen Audio has their own shunt regulators, for internal use only.




Patrick
Does that mean that Xen Audio is using shunt regulators with R-core tx's for the SEN?
As you usually don't complicate minimalistic designs, like the SEN, with un-neccesary regulation I would take that to mean that there is a sonic benefit of doing so.
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Old 11th June 2012, 03:42 PM   #882
EUVL is offline EUVL  Europe
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No.

For most applications where the absolute voltage is unimportant, such as in the SEN IV, battery with LC filter is our preferred solution.

The question was whether we tried Salas shunt.
The answer was no, because we have our own.


Patrick
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Old 11th June 2012, 10:21 PM   #883
needsp is offline needsp  United Kingdom
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Hi Patrick

Sorry to come back to the ES9018 and its offset requirements, but, if Iím right, Iíll get out of your hair and get on with actually trying SEN! It might also help to in part repay Nicís largesse in providing me with matched FETs.)

Twisted Pearís Legato IV stage for the ESS9018 has appeared in three versions. All used a current mirror to set the voltage on the input. In the first two, this was set to Ĺ AVCC; in the third, to 0 V. See here

http://www.twistedpearaudio.com/docs..._schematic.pdf

and here

http://www.twistedpearaudio.com/docs..._schematic.pdf

In addition Russ White, the designer stated (quoted from Legato 3 - Look ma! No caps!)

"Legato 3.1 (THIRD VERSION) is a different circuit from Legato 2 (SECOND VERSION) with it input always centered at GND.....My research showed that there was really no benefit because of the symmetrical nature of the circuit in centering at AVCC/2. So that feature is out...."

I therefore think- from my position of relative ignorance!- that I could use SEN referenced to 0 V too, without a current offset. Do you agree?

Best wishes

Paul N
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Old 11th June 2012, 11:38 PM   #884
NicMac is offline NicMac  Italy
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Paul,
Would it not generate DC off-sett on the output ignoring the DAC offset?
When I set up the SEN I got zero output voltage off-set at exactly AVCC/2....... , but of course I did not try to leave out entirely the voltage divider.
Just my relative ignorance
Nic

BTW, Legato III has about 7V of DC off-set on the balanced output.
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Old 12th June 2012, 04:31 AM   #885
EUVL is offline EUVL  Europe
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Paul,

I would not commend on someone else's IV design.
If you would like to use SEN for the ES9018, we recommend you to build as we suggested.
Of course we welcome you to experiment and tell us what you find out with other configurations.

I don't want to recommend you to have 7V DC on the balanced output.


Regards,
Patrick
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Old 12th June 2012, 07:55 AM   #886
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Patrick

have you ever powered Sen with non batteries being shunt regulator or whatever
alternative to batteries which are expensive
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Old 12th June 2012, 10:22 AM   #887
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Default Variable Precision Current Source from 1mA until 1000mA

Quote:
Originally Posted by EUVL View Post
For those who need a stable current drain for the likes of PCM1794 :
http://www.edn.com/archives/1998/031398/06di.pdf
(Have not tried myself ....)
Patrick
Thanks for this URL. Unfortunately the link is death in the meantime.
But google shows this pages shortly by the button "quick view". I have save this article as PDF (3 files).

An other question: Are there clearly audible advantages by the use of the SEN instead the CEN (actually "Single ended" vs. "Push-Pull") ?
The differences in the measuring results don't show me things regarded the audible results by a listening test of both.
Additional I want to know, which unwanted effects I must accept, when I use MOSFET'S instead jFET's (actually Pass D1-I/V vs. SEN).

Last edited by tiefbassuebertr; 12th June 2012 at 10:26 AM.
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Old 12th June 2012, 10:46 AM   #888
regal is offline regal  United States
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Quote:
Originally Posted by tiefbassuebertr View Post
Thanks for this URL. Unfortunately the link is death in the meantime.
But google shows this pages shortly by the button "quick view". I have save this article as PDF (3 files).

An other question: Are there clearly audible advantages by the use of the SEN instead the CEN (actually "Single ended" vs. "Push-Pull") ?
The differences in the measuring results don't show me things regarded the audible results by a listening test of both.
Additional I want to know, which unwanted effects I must accept, when I use MOSFET'S instead jFET's (actually Pass D1-I/V vs. SEN).
I think using mofsets is touchy. If you simulate the D1, depending on the DAC output you can get -50db THD to -100 db THD, sometimes changing just a few mA of current thru the mofset swings the results 50dB more distortion. I don't get a good sense of robustness to the D1 circuit while the Sen seems very stable with the only penalty being minimally higher input impedance which is a dubious theory at best at actually adding distortion to most DAC chips.
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Old 12th June 2012, 11:24 AM   #889
needsp is offline needsp  United Kingdom
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Hi

That was the answer I expected. I was trying to use the Twisted Pear circuits as exemplars, but I suppose any mention of them in a public forum might be taken as I discussion of them in themselves, and lead to misunderstandings.


For the record, I was trying to show - as I understand it (maybe incorrectly) that, in the opinion of an experienced ESS9018 user (Russ- apologies if Iíve got this wrong), the ESS9018 doesnít need to see a voltage or current offset. To me, at their most basic, Legato and SEN are the same circuit- a common base/gate stage- a modified CFP in Legato, a common gate stage (if that's the right terminology) in SEN- together with a CCS. (The 7.5 V on the output is the result of non floating supplies used and the positioning of the IV resistor. In principle, I think, you could use floating supplies etc a la SEN and get zero volts on the output). So, what works for Legato should work for SEN?


Basically, I lack the courage of my convictions (I know how patchy my understanding is) to actually try this. I donít want to wreck my DAC!


Any comments appreciated , public or private, and, again, apologies if Iíve misrepresented anyoneís views

Paul
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Old 12th June 2012, 11:28 AM   #890
EUVL is offline EUVL  Europe
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You cannot use mosfets in this simple circuit without major modifications, due to the self biasing nature of JFETs.
You can of course use depletion mode MOSFETs in lieu, but I don't see the point, other than maybe higher transconductances, at the expense of higher noise.


Patrick
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