My Take on Threshold NS10

[Russ White]

Hello all,

Tony and others have asked me to look over the NS10, so I did. I managed to find Nelson's schematic, but it is lacking values and ratings for parts. So I just threw something together hoping Nelson and the rest of you could help fill in the blanks.

Some questions:

1) What should the PS be.

2) What are the part values.

3) What other design factors should I consider.

So to get things rolling I submit what is likely a completely flubbed up layout:

Cheers!
Russ

[Russ White]

And my first attempt at the schematic:

[apassgear]

Originally posted by Russ White
Hello all,

Tony and others have asked me to look over the NS10, so I did. I managed to find Nelson's schematic, but it is lacking values and ratings for parts. So I just threw something together hoping Nelson and the rest of you could help fill in the blanks.

Cheers!
Russ

Good you did open this thread, you won me but I'm glad you did.

I wanted to post a GUESS WORK schematic with some values to gather some interest and maybe having others like Blues running a virtual test. Of course we would like Nelson throughing in all his knowledge and memory of it, unfortunately he does not have the original schematic.

One thing for sure, Nelson has tiped that the NPN devices should now be MPSA18 (On-Semi). I check on this and it is a modern replacement of the original MPS6571 same low noise and equal in most parameters with the added benefit of a higher voltage rating, VCEO and VCBO up to 45.

[Zen Mod]

Threshold NS-10 and M1 info. wanted

[Russ White]

Ok I found lumanauw's excellent instructions:

If you are a "dumb", then I'm the "dumber"

You got the blind NS10 schematic in your hands?
If you do, then here's what I do.

-First, I use symmetrical power supply, +/-25V with 0 gnd. So, I do not use R5, R6, R7 in the schematic. If you got only single supply 0/50V, then R7=200k, R5=R6=100k, C4=47uF.
- R13=20k potentiometer, for volume adjust. The wiper goes to left of C1 (470nF MKT), R12 is moved after C1. The bottom of VR13 goes to ground via additional 1k resistor, the upper is fed with input.
-The right of C1 connected to voltage divider (R6-R7), thus to R12=1k, and this R12 connects to gate of Q1, or if you got symmetrical supply, you can put the right of C1 with 100k to gnd (0V).
-R12=1k, is placed after the voltage divider (that is after C1) and before the gate of Q1 (2sk30y).
-I also put 470pf WIMA from gate to drain of Q1 (2sk30y).
-R4=10k, Q2=mpsA92, Q3=mpsA42, R8=470ohm, C2=C3=22uF non polar elko. R1=10k, R2=2k2 (makes gain=10k/2k2), R9=2k7 1/2watt.
- put base stopper at base of Q3, I use 1k there.
- R3 is for adjusting DC output, it is about 100k-470k, depends what device you use for Q1. I myself don't mind DC offset at left of C2, I got only 0V5 there, so I don't use R3. Sounds better without R3, even it has DC.
-R10=100ohm, R11=100kohm.

I tried various devices for Q1, MPSA06, MPSA42, 2n5401, BC550C, BC546, they sound differently. The best sound is 2sk30y (you can also buy 2sk30gr suffix).

And I have attempted to do a bipolar schematic, but I am affraid I have botched it. Especially I am worrind about what should be connected to the negative rail.

Please bear with my ignorance. This is a learning expedition for me.

Cheers
Russ

[apassgear]

Originally posted by choky

Threshold NS-10 and M1 info. wanted

You are right

On post 11 Lumanauw gives values for a double rail NS10.

So if we are doing it a double rail (+-25V) we have a very good staring point from a working clone.

[steenoe]

Maybe it would be possible to convince some of the owners to take the lid off, and do a little investigation?

Steen

[apassgear]

I guess this is the circuit that Tom (tmblack) is mentioning on the other NS10 thread (NAC 32?) or NA321?. This one uses a CCS.

PD Sorry, the file is to big for posting

[Russ White]

So does anyone know where the negative rail connects to the circuit? Did I do it correctly?

Thanks,
Russ

[Nelson Pass]

There is only a positive rail and ground in the original, in
case this is a point of confusion.