Some other Source Follower COnfigurations - Page 9 - diyAudio
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Old 12th September 2009, 12:23 AM   #81
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There is a X-balanced version about somewhere, but this Taylored version is the current "official" EUVL design.

They seem to suit all types of headphones - AKG701, Beyer 808, Senn 424 (old ones), and a few others that I've tried - most headphones like extra series resistor in the line (but not essential), and you can trim the headphones sound to suit yourself.

I added the lightspeed vol control plus a k170/j74 buffer to the input and a Salas shunt supply and this improved the overall performance quite a bit.

The next thing to go into it is the CT supply before the Shunt reg (works like the "Never Connected" system then possibly adding the extra grnd isolating 3rd amp (as per headwise unit)
The Xfeed ccts need to be less obvious, more suble - still playing about with this, and also, still looking for a clean, quiet set of tone controls - not so easy.

You can play with the resistor values quite a bit, to trim the sound - I used higher values all over and added parallel "trimmers" to suit - the IRFP044s do have a slightly different sound and seem to prefer a slightly lower rail volage.

It sounds much better when really hot - at least 50*C, so an outer "guard" on the heatsinks is useful.

' Hope this is of use to you - an excellent headamp and no fatigue at all.
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Old 14th September 2009, 02:57 AM   #82
fff0 is offline fff0  Singapore
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Thanks JH for the excellent update and sharings.
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Old 18th September 2009, 07:17 AM   #83
fff0 is offline fff0  Singapore
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Hi Jh, Steenoe, EUVL,

I understand loveltech LU1014D are P-JFET with a low transconductance but why cant we use it as the output fet (in replace of IRFP240)?
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Old 18th September 2009, 07:56 AM   #84
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The littlecritters will have a heart attack with the rail volts applied - perhaps try the IRF610 series instead of the IRFPs - I thought about trying it but then decided "why try to re-invent the wheel", especially one of Patricks. The only thing i played with is adding more current but found about 280mA to be about the right sound for me with the reg sinking about another 300mA on top of that - certainly keeps the heatsink fully at work, and justifies me using some beeefy power supply caps!

It works really well, costs bugger all, has a pcb designed, is fully specced, what more do we need unless it's a full kit of bits!!
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Old 18th September 2009, 09:52 AM   #85
juma is offline juma  Serbia
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Quote:
Originally Posted by fff0 View Post
Hi Jh, Steenoe, EUVL,

I understand loveltech LU1014D are P-JFET with a low transconductance but why cant we use it as the output fet (in replace of IRFP240)?
You couldn't be more wrong They are absolutely opposite of what you wrote!

You could at least read the datasheet before making such a comment - or are you deliberately trying to bring the confusion in here?
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Old 21st September 2009, 04:46 AM   #86
fff0 is offline fff0  Singapore
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Sorry, I thought its possible. Absolute newbie here. I dont see anything in the data sheet that shows me this therefore made this silly question.
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Old 21st September 2009, 08:59 PM   #87
EUVL is offline EUVL  Europe
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> I understand loveltech LU1014D are P-JFET with a low transconductance but why cant we use it as the output fet (in replace of IRFP240)?

By P-JFET he meant Power JFET and not positive JFET.
LU1014D does have a HIGH transconductance.

It cannot replace the IRFP240 in a 1:1 swap because :
a) It needs a negative Vgs instead of a positive.
b) It works best when cascoded with a low-ish Vds.
c) It needs some Vds variation for distortion cancellation.

Please read Nelson's article on Zen Version 9 for details.


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Old 22nd September 2009, 03:26 AM   #88
fff0 is offline fff0  Singapore
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Thanks Patrick.
You have got what I have meant, power Jfet.
I thought since LU1014D is working at around 5~6w in F3(if I am not wrong), why not use it as a output fet for a headphone amp with alteration, of course (how? I dont know, perhaps taking F3's front end & try). However, it seems like its not what I had thought, have got the concept completely wrong.

I have read thru Nelson's F5, F3, Zen V9, Zen V4 but maybe I didnt understand it as well as I have thought. I was thinking it like a tube triode which some had used for low power output. Nevertherless, I shall drop this idea. "Official" EUVL design seems good enough for me.

By the way, the circuit at shown at post#48 is meant for mono channel right?

Last edited by fff0; 22nd September 2009 at 03:36 AM.
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Old 22nd September 2009, 05:33 PM   #89
EUVL is offline EUVL  Europe
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Yes.
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Old 24th September 2009, 07:32 PM   #90
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Quote:
Originally Posted by EUVL View Post
I mentioned in Post #19 that the DAO Follower with Taylor Current Source (TCS) has 20dB more 2nd than without, but has also 20dB lower distortion from 3rd harmonics onwards.

Of course one can use two DAO TCS in balanced mode, which will easily reduce even harmonics by a factor of 10 if the devices are well matched. But that is a no-brainer.
Dear Patrick,

Just a simple question.
In the article "alternative jfet followers", the simplified all-JFET Taylor Follower was stated:
Distortion @ 1V, 1K load 0.005% (almost entirely 3rd)

So why in DAO Follower with TCS the distortion is mainly 2nd harmonic?
Thank you!

Zhou Fang
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