Building a symmetrical PSU B1 buffer

[tommy_o]

I'm picking this project up again after a few years and I'm still stuck on the same JFET matching question.

Many years ago, I bought 2 matched pairs of 2SK170BLs. When they're installed, how are the paired together?

In other words, if I have matched pair "A" and pair "B," are they installed like this:


Or should they be attached like this:


From AndrewT's comment here, I'd imagine it is the former image.

 

[mnichols30030]

Order for 2SK170BLS

Tommy_O

The order for the two pairs is covered in posts 1805 and 1806 with pictures and measurerements.

I had the same question and stumbled on the answer.

Have fun.
M

 

[sergiog]

Hi, John Bali,ho appena adesso visto il tuo bel layout,ma mi mancano alcuni dati: il valore della resistenza del source of 9240 is 34 Ohm?,il valore della resistenza (R5 in original schematic) is 10 or 1 Ohm?.Ringrazio anticipatamente.

 

[sergiog]

Hi, John Bali, I have just now seen your nice layout, but I am missing some data: the resistor value of the source of 9240 is 34 Ohm?, The resistor value (R5 in original schematic) is 10 or 1 Ohm ?. Thank you in advance.

 

[longspeak]

Can I use LSK170A's in the Mezmerize (10YA board) PSU section? Maybe with some changes to the source-drain series LED/resistors?

 

[longspeak]

I probably should have asked this in the build thread, my bad.

I think the answer is "yes" based on the answer here: Mezmerize DCB1 Building Thread

 

[Salas]

Yes, LSK "A" is like 2SK "GR" i.e. the lower Idss category but still good for the PSU section. Without other changes needed there.

 

[csdawson]

I have a matched quad for the signal section, but does anyone know of a more readily available replacement for the six 2SK170's for the PSU section (it seems like the spec tolerances are less stringent for those)? Maybe someone at the DIYAudioStore could help me get an unmatched set of the LSK170's?

This might be another option, but those Fairchild PF5102's seem to be not that easy to get either.

 

[Salas]

You could buy random LSK170A from Nacsemi.com in Florida

 

[myleftear]

or there's still some available @ Genuine Toshiba 2SK170BL Low Noise N-Channel JFET.

 

[bkdog]

Or even cheaper the LSK equivalent here
LSK170B-TO-92 | LINEAR SYSTEMS | NAC Semi

 

[csdawson]

Thanks. Spencer hooked me up with some Toshibas for a very reasonable price.

I'm thinking about integrating a phono pre-amp in the same box as the DCB1. Any suggestions? Maybe a favorite Salas design? 😉

 

[Salas]

For keeping with a JFET theme, this design has proved quite popular: Ultra Folded Simplistic Phono (UFSP)

 

[Sedabaz]

Works wonderfully as output stage to V-out dac chips. Like my Technics CD-player with no DC.
Thanks boys.

 

[Sedabaz]

Thanks Salas for the wondersound desin,
and a little question please,
How can vi move the volume control to the output? Getting the best of a V-out DAC chip directly? Any changes in the input?

 

[Salas]

You are welcome. If you will move the volume pot to the dcb1's output you negate the pot's output impedance buffering by dcb1. Just the signal source remains buffered. If you must try that for some reason, no there are no further modifications needed.

 

[Sedabaz]

Tanks a lot.
and the volume control. I've got only 50k. Is it ok putting a 47K fast resistor, parallel to it? Sum of CA 25K.

 

[Salas]

It will skew its logarithmic taper i.e. its getting louder profile to the human ear. But there is no electrical problem in doing that.

 

[Sedabaz]

Thank you so much Maestro.

 

[Salas]

You can even turn a linear pot to almost log when putting a quarter of its value resistor between its wiper and ground. Say 25k for a 100k linear pot.