Preamp-Buffers - simple idea

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#543
Well after fixed the PSU I have solid as a rock +-15VDC.

Used LSK389
J2A
Idss 7,54mA
Vp 0,76V

J2B
Idss 7,47mA
Vp 0,66V

Rs in both LSK389 10 ohms

Measurements:

0.072-0.073V across Rs J2a
0.071-0.072V across Rs J2b

4.29V J3 VGS
5.24V J4 VGS

If I understood well Andrew explanation the bias point is 7,2mA so very near of Idss 7,50mA. Now I have only to match VGS of both J3-4 right?
 
#548
Thanks Joshua, in my system sounds better Calvin schematic B buffer than JC buffer, the differences are clear: more resolution, no analytic sound, etc.

Congrats Calvin, surely I will try schematic C & D for the AVC volume control, not sure for the active xover, will see depending the result with the AVC.
 
#550
merlin el mago said:
Thanks Joshua, in my system sounds better Calvin schematic B buffer than JC buffer, the differences are clear: more resolution, no analytic sound, etc.

Congrats Calvin, surely I will try schematic C & D for the AVC volume control, not sure for the active xover, will see depending the result with the AVC.
Click to expand...

Congratulation, Felipe.
You saved me 2 topologies I had in mind comparing. Based on your experience, I intend to compare either B and C, or B and SE Hybrid Cascode Compound (C) and PP Hybrid Cascode Compound.
The buffer is intended to come between IVC and the power amp, however upon finding the best sounding buffer (to my taste and on my setup), I'm going to compare also the IVC to DACT Stepped Attenuator.
 

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#556
merlin el mago said:
I owned DACT & changed for Shallco with Shinkoh, Intact Audio AVC is best.
Click to expand...

I accept your experience, however the picture may change when the TVC/IVC/Attenuator is buffered by Calvin Buffer. It will cost me nothing to compare.
It's also my experience that without a buffer the Tribute IVC is the most pure and transparent preamp, though it lacks dynamics with my power amp. With a simple JC buffer, like in "A", the IVC is superior to any preamp I encountered in respects, or in all sound parameters, including dynamics.
The prospects are that it will be even better with one of the two versions of the Calvin Buffer (SE or PP).

Also, what's 'better' may depend on the entire stereo setup and personal taste.
 

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#557
I forgot to told you in my system & for my taste. I agree with you nothing beats the AVC alone, Calvin posted it depends of the load:

" ´D´ shows slightly better THD than ´C´ with highimpedance loads, while ´C´is slightly better with lowimpedance loads and can drive up to 6Vrms."

Following Calvin advice between pre an amp "D" will sounds better "C", for active xover loudspeakers "C".
 
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#558
merlin el mago said:
Very good news, I have on hand spare KSA1381 for my SSHV2🙂

Do you know the values for schematic C?
P1
R15-16-17-18-19-20
C1 & C2
Click to expand...

In the attached pdf document all values are given for version "D". There should be no change in resistors values for 2SK170/PN4391 JFETs.
For version "C" use the values given in the attached jpg, only, for KSA1381 change C1,C2 to 100pF.
 

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#560
merlin el mago said:
I forgot to told you in my system & for my taste. I agree with you nothing beats the AVC alone, Calvin posted it depends of the load:

" ´D´ shows slightly better THD than ´C´ with highimpedance loads, while ´C´is slightly better with lowimpedance loads and can drive up to 6Vrms."

Following Calvin advice between pre an amp "D" will sounds better "C", for loudspeakers "C".
Click to expand...

I compared the Tribute IVC to Music First (MKI) preamp (based on S&B TVC). I prefer the Tribute IVC.
Between "C" and "D", I believe it depends much on the specific setup and personal taste. As for the setup, everything counts, not only the speakers.
It seems to me that those minute technical date differences aren't much relevant to SQ.
Both are inexpensive enough as not to prohibit comparing.
 
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