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Old 27th September 2019, 10:37 AM   #21
EUVL is offline EUVL  Europe
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Simulation is a very useful design tool to allow you to vary parameters.
Mordern-day engineering can hardly do without simulations, whether in Space or in F1.
Of course you always need to check against reality.
Simulation is only as good as the model you use.

And THD also does not tell you the entire story about how it sounds.
And how it sounds vary from one person to anther.


Cheers,
Patrick
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Old 27th September 2019, 11:51 AM   #22
mbrennwa is online now mbrennwa  Switzerland
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Quote:
Originally Posted by EUVL View Post
Of course you always need to check against reality.
Simulation is only as good as the model you use.

And THD also does not tell you the entire story about how it sounds.
And how it sounds vary from one person to anther.
Ah, well, my question was not about "how does it sound", that would be asking way too much! I was more interested about the fact that the original idea for the J2 was to use the SemiSouth parts instead of the IRFPs, because the SemiSouths allow lower distortion. This is in contrast to your simulation, which seems to indicate that the IRFP version has similar (if not lower) distortion as the SemiSouth version.
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Old 27th September 2019, 12:09 PM   #23
EUVL is offline EUVL  Europe
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If you read the article carefully, you will know how the lower transconductance of the IRFP is being compensated by the increase in input stage gain.
All information have been published and explained.

I can also show a simulation where the distortion is 10x lower by increasing the OLG further by a current mirror.
In a very similar way that opamps has ultra low distortion of < -120dB.
But that is not the purpose of this exercise.


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Patrick
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Old 28th September 2019, 07:24 AM   #24
EUVL is offline EUVL  Europe
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I was asked if an NMOS version would work.
I was not going to publish this, but yes it will work.
You will need unobtanium 2SJ74or 2SJ109, but you can still get those in GR grade (min 4mA Idss).

Since it is the UDNeSS with reversed polarity, it will have to be called RUDNeSS.




Patrick

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Old 28th September 2019, 07:32 AM   #25
EUVL is offline EUVL  Europe
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As you can tell from the schematics, you can use the already published PCBs for the SJJ, etc.
But this is as far as I'll go with the RUDNeSS.


Back to the "normal" UDNeSS,
Patrick
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Old 28th September 2019, 08:04 AM   #26
indra1 is online now indra1  Indonesia
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Quote:
Originally Posted by EUVL View Post
You will need unobtanium 2SJ74or 2SJ109, ...
And currently the store has LSJ74 matched pair in stock. Let's support the forum.
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Old 28th September 2019, 09:02 AM   #27
EUVL is offline EUVL  Europe
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For the price of a quad of 0.1mA LSJ74's, you can buy 300 pcs of J113 from Mouser.




Patrick
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Old 28th September 2019, 09:53 AM   #28
EUVL is offline EUVL  Europe
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> As you can tell from the schematics, you can use the already published PCBs for the SJJ, etc.

Forgot to mentiuon that you should really add the DC servo, for the same reason as in the UDNeSS.


Patrick
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Old 28th September 2019, 01:48 PM   #29
EUVL is offline EUVL  Europe
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As we are not using Power JFETs anymore, we can also use MOSFETs for the front end, as in the Pass Aleph.
So instead of unobtanium 2SJ74, how about not-so-unobtanium 2SJ79 ?
2SJ79 Japan-Transistor pnp 200V 500mA 30W TO220AB von Renesas (Hitachi) | eBay

UDNeSS with J113 is still unbeatable for value.


Patrick
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Old 28th September 2019, 02:47 PM   #30
indra1 is online now indra1  Indonesia
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Do you have opinions you can share on current production parts like the ZVP2110, ZVP3310 mosfet and J270, J177 jfet family? I read somewhere jfets from Interfet have better noise figure.
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