My Take on Threshold NS10

[jacco vermeulen]

Mr. Pass himself.

I am convinced NP is a twin, the biggest audio secret.
Or triplets, "The Only One" is not enough for pumping out so much, so fast.
(either that, or God, but let's not go that stereotype road)

 

[steenoe]

Some people want to try a FET for Q1. There is no change needed in biasing it.

Thanks a lot, Tom

Is there a NS10 PSU schematic around I´missing?

JC, there was no psu posted yet, but someone will eventually

Here is a pic of the proto boards in the making. No fancy parts yet. The first test will be to see, if this works at all Dont let Q2 confuse you, I have used a BC560C, which has a different pinout than the MPS4250.
Where is best to wire the pot, for a circuit like this. Input or output?

Steen

 

[tmblack]

Kewl boards, did you make them with the laser toner method?
If so, which paper did you use?

Tom

EE

 

[apassgear]

Some people want to try a FET for Q1. There is no change needed in biasing it.

Tom

EE

Thanks Tom, That's what we wanted to hear

 

[apassgear]

Re: NS10 PSU schematics

Is there a NS10 PSU schematic around I´missing? What could be the trafo VA rating?
JC

I will propose a PSU soon. A double rail regulated supply similar to other Pass projects.

The actual demand of the circuit is very low so a small trafo will do, some 20/30 VA for both channels is enough.

 

[Russ White]

As promised, the split rail schematic for the layout I submited.

 

[Russ White]

Steen,

Nice PCBs man! that was a good etch.

I hope I didn't muck up the layout.

Man I hope it works....

Cheers!
Russ

 

[steenoe]

Tom, yes thats the tonertransfer method. Here is a link with a really good description of the process. The paper I used is called OCE glossy photo paper, IJ570. It was bought a couple of years ago, but I am not sure I can get that paper again.

http://www.fullnet.com/u/tomg/gooteepc.htm

Russ, thanks for the schematic. Yes that etch turned out pretty good. There is no problems populating the boards, so no muckups yet Here is a closer pic of the boards.

Steen

 

[JC Fardo]

Thanks guys.

What tinny wonders.
I made a print from PDF and could not believe it´s quite as big as a credit card

Cheers everybodyl. JC

 

[apassgear]

Here is a pic of the proto boards in the making. No fancy parts yet. The first test will be to see, if this works at all Dont let Q2 confuse you, I have used a BC560C, which has a different pinout than the MPS4250.
Where is best to wire the pot, for a circuit like this. Input or output?

Steen

Steen,

I will say it again, your work is one of the best around. Absolutely very nice boards you did. Which etching solution are you using? Hope to do some as nice as yours, some day.

Regarding the pot position it’s a matter of preference and testing, but will also depend on your source output impedance. If you plan to use it with a highish source impedance I would try it at the output of the preamp. But otherwise I would put it at the front, guess that the original NS10 was also at the input.

For the front pot try a 20K and for the rear position I would start with a 10K and increase it to 20K if you think it’s to much load.

 

[apassgear]

Steen,

I would also try the circuit without RBS (1K). Worth the effort I think. Let us know about the any diference you may hear

 

[apassgear]

Thanks Russ for all the effort, think all is coming out nice

Next board iteration, after ironing other issues and of course after some testing results I would suggest you try to put all 3 transistors closer still, the closer you can. I think it would be well worth the effort.

 

[Russ White]

Yes I was thinking the same Tony, I could really get things close if I go double sided.

 

[apassgear]

PSU

Russ,

I think a good PSU for this pre would be what you have on the XBOSOZ. If you agree pls post the schematic for others to see.

For all of you:
Rails after regulation would be +25/-25V, so adjust zeners to have these voltages (some 28V zener stacks).

It would be a good idea to load the outputs of the regulators with some 10mA using a shunt resistor to get good voltage stability. This means to add a 2.5K resistor from rail to ground after the PSU output caps.

 

[Russ White]

Hah Tony,

I was just about to suggest the same!

Here it is:

 

[Russ White]

Here is how the PS looks:

 

[Russ White]

PS copper.

Copper:

 

[Russ White]

PS component side

Here is the component side:

component side

 

[Zen Mod]

Re: PSU

Russ,

I think a good PSU for this pre would be what you have on the XBOSOZ. If you agree pls post the schematic for others to see.

For all of you:
Rails after regulation would be +25/-25V, so adjust zeners to have these voltages (some 28V zener stacks).

It would be a good idea to load the outputs of the regulators with some 10mA using a shunt resistor to get good voltage stability. This means to add a 2.5K resistor from rail to ground after the PSU output caps.

shunt current-make it 30 or 50 mA
piece of cake with this voltage and used (proposed) parts
3w resistor per rail will do the job

 

[Russ White]

I think it would be best to put those rail shunt resistors on the preamp PCB, because I have no room to expand the PS PCB because it is as big as I can get it with my current license.

Cheers!
Russ