Simplistic NJFET RIAA

Jump to Latest
#2,787
Matched LSK389

Hi Salas

Finally matched the 12 pcs. LSK389 dual:

Group 1
1 IC: 1st njfet 7,42 / 2nd njfet 7,50
2 IC: 1st njfet 7,25 / 2nd njfet 7,02
3 IC: 1st njfet 7,83 / 2nd njfet 7,82
4 IC: 1st njfet 8,05 / 2nd njfet 8,24

Group 2
1 IC: 1st njfet 9,32 / 2nd njfet 9,25
2 IC: 1st njfet 9,74 / 2nd njfet 9,72
3 IC: 1st njfet 9,29 / 2nd njfet 9,28
4 IC: 1st njfet 9,23 / 2nd njfet 9,29

Group 3
1 IC: 1st njfet 10,53 / 2nd njfet 10,59
2 IC: 1st njfet 10,96 / 2nd njfet 10,97
3 IC: 1st njfet 10,54 / 2nd njfet 10,62
4 IC: 1st njfet 11,23 / 2nd njfet 11,29

3 pcs. K170GR single

1 Idss: 5,0
2 Idss: 5,2
3 Idss: 5,7

3 pcs. k170bl single
1 Idss: 7,6
2 Idss: 9,7
3 Idss: 10,24
4 Idss: 10,25

With these can I make your Simplistic NJFET RIAA? or it's necessary that I wait until I receive the batch of 100 pcs sk170 single from Spencer to match exactly Idss: 8-9?

Surely I buy the Denon DL-103R, it's a good idea to change the body & install one offered by Soundsmith, or buy both to Soundsmith so I will have the wood body installed?

An externally hosted image should be here but it was not working when we last tested it.


Merlin El Mago
 
#2,788
Hmm...I see many interesting pairs between 9-11 in your stash. I will have to see about the MC version with a mean average of 10.5 and let you know precisely, in the next few days. Surely you can get more gain with a different B+ and some possibly altered resistor values.
 
#2,794
I doubt that the damping benefit is going to overcome the SNR electrical benefit of much lower Ro for virtually the same Vo importance. Mechanically its a lighter coil as well. Though I haven't had a chance to subjectively compare on a TT. Take it with a pinch of salt.

Interesting solutions to your investigation maybe:
ISOkinetik Denon 103 dl-103 aluminium body RED DL-103R bei eBay.de: Turntables (endet 19.12.09 18:53:04 MEZ)
NEW DENON DL-103R WITH MOUNTING BLOCK MOD MK2 IMPROVED bei eBay.de: Turntables (endet 14.01.10 15:05:08 MEZ)
 
#2,795
merlin el mago said:
Hi Salas

Finally matched the 12 pcs. LSK389 dual:

Group 3
1 IC: 1st njfet 10,53 / 2nd njfet 10,59
2 IC: 1st njfet 10,96 / 2nd njfet 10,97
3 IC: 1st njfet 10,54 / 2nd njfet 10,62

3 pcs. k170bl single

3 Idss: 10,24
4 Idss: 10,25

With these can I make your Simplistic NJFET RIAA?
Merlin El Mago
Click to expand...

My idea is that those good strong LSK389 pairs should be put into action. We all get enough 2SK170BL 10-11mA pieces in small volume purchases too. So in your case you must use one chip for Q1&Q7 plus another for Q2&Q5 per channel. Your singles #3 & #4 will do Q6 per channel. C10 must be good quality, 6-16V is enough, you can subjectively try a bypass with Vishay MKP 1837 10-100nF or analogous, also. 63dB of gain is enough for low MC, else there is weak gain structure in the rest of a system. Double Jfet 1st stage and Rs bypass should keep the hiss just OK. Not champion, but normal. Especially with circa 90dB speakers. If it will work nicely for you, it may be OK for everybody. It has the advantage of simply taking out C10, by a local DIP switch even, and falling directly to 57dB for 0.5mV normal MC. Somebody can move between Low MC and normal MC carts without overhauling the phono stage. Just a new Rload value if needed, can be DIP switched too.
 

Attachments

  • LowMC63.gif
    LowMC63.gif
    8.2 KB · Views: 3,839
#2,797
Can this be done with "normal" 2sk170bl ?

I have some in that 10.5mA range 🙂

Can this version compete with the previous 56dB 37V version if used without the bypassing EL ?
besides the higher gain and working voltage, what are the main differences ?

Is there any kind of "special" dip switch ?
 
Last edited:
You must log in or register to reply here.
Top Bottom