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The XEN XELF Headphone Buffer
The XEN XELF Headphone Buffer
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Old 14th July 2019, 07:18 AM   #11
EUVL is offline EUVL  Europe
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Spice file for the power amp version.


Patrick

.
Attached Files
File Type: asc ADA4627 XELF V1a Public THD.asc (7.6 KB, 124 views)
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Old 9th December 2019, 08:20 PM   #12
EUVL is offline EUVL  Europe
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I normally do not comment on the sound of my own creations.

The proto in post #6 went to a friend in Portugal for comparison with his other headphone amps, including the WHAMMY.
After weeks of listening sessions, here is what he wrote :

"Yesterday had a WHAMMY - XELF shootout with 3 new pairs of young ears ;D
The vote was unanimous....XELF with JCOPA is clear winner.
Now my problem is that the owner of the Whammy is unhappy.....and he was so happy before. "


He built the Whammy for his son.....

Details of the JCOPA you can find here :
One Last Attempt at Discrete Opamp in DIP8 Footprint

The DAO is still king. He also has one.


Patrick
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Old 10th December 2019, 06:09 AM   #13
Morde is offline Morde  Finland
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The XEN XELF Headphone Buffer
This is a remarkably good headamp when paired with a good opamp. Especially when considering how easy and simple this one is to put together. Highly recommended for all headphone enthusiasts.
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Head amps: SE84, Salas DCG3, UTHAiM, PassDIY HPA, Pioneer Super Linear, XEN JLH
Power amps: M2x, UDNeSS, F7 clone, F5X
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Old 3rd March 2021, 04:34 PM   #14
donovas is offline donovas  South Korea
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I adopted the bias circuit of this in place of the 10k resistor bias of the whammy, thus creating a hybrid of the 2 circuits- whammy's optocoupler and xelf current mirror, and i must say its a substantial uograde from the vanilla whammy. Id like to know your opinion on whether the optocoupler bias of the whammy is worth keeping or ill see another improvement adopting xelf's schematic there too.
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Old 3rd March 2021, 05:46 PM   #15
EUVL is offline EUVL  Europe
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They key to the XELF is the use of lateral power MOSFETs.
Since they have a negative tempco, there is no need for the opto-coupler biasing.
The latter is still a sort of feedback circuit, which is not the case in the XELF.


Patrick
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Old 9th March 2021, 11:43 AM   #16
InspectorGadget is offline InspectorGadget
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I have some semelab/exicon laterals spare that it seems this would be a perfect use for. now I just need to find some time to do a layout. a multichannel DAC, an ADC->DAC->headphone amp and a J2 are up first though. I only wish I could be as prolific as you Patrick
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Old 9th March 2021, 03:15 PM   #17
donovas is offline donovas  South Korea
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Patrick please have a look at this circuit- the old bakoon hpa-1. What if the b1 type buffer thats being used at its input was placed in xelf between the opamps output and the variable resistor? The opamp now only has to worry about driving the gate of the jfet thus a superior impedance matching is achieved?

Google Image Result

And yes i see that about the latfet bias, thank you. The unavailability of it dictates that i use the optobias and keep the hexfets in place

Last edited by donovas; 9th March 2021 at 03:21 PM.
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Old 9th March 2021, 03:50 PM   #18
EUVL is offline EUVL  Europe
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The input of the XELF follower drives the two gates of the lateral MOSFETs and two current sources in parallel.
The dynamic impedance of the current sources are IMHO high enough for any reasonable signal source.
If your signal source has poor driving capabilities, you can add a source follower upfront, like we need in the Pioneer Super Linear.
But it always adds distortion, however small.

You are of course free to do whatever is appropriate for your particular application.


Patrick
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Old 10th March 2021, 03:11 AM   #19
donovas is offline donovas  South Korea
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I think its worth it as a logical exercise because the whole point of circuits like these is to compensate for the lousy output of the opamp so why not also compensate it within the circuit if theres an opportunity to do so?

I will p2p this mod and report back the findings
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Old 10th March 2021, 03:35 AM   #20
EUVL is offline EUVL  Europe
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I don't use opamps with lousy output.
So no need for additional complication / distortion.


Patrick
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