Review: Threshold NS 10 Preamplifier

Category: Preamps

The Threshold NS 10 was Nelson Pass first preamplifier bearing the Threshold name. And was one of those early over the top products from the mind of Nelson Pass.

While the cosmetics of this unit were more like a laboratory audio preamp as opposed to the next generation preamp from Threshold being the SL 10. The SL 10 cosmetics were very good with its lower profile,sculptured control knobs and separate power supply and remains to this day a stunningly beautiful preamp.

It is clear from the outset that the NS 10 was built as a pure no nonsense,no holds barred preamp,that could pass signals with zero degradation to the original signal. The build quality of this preamp immediately set an industry standard as no other before it and that few today can match. While its cosmetics are somewhat austere, the true beauty of the NS 10 is in its execution of its design. Built during the time that analog was in its prime exceptional detail was lavished upon the phono section of the NS 10 and two inputs for turntables is provided. The phono inputs are for MM, however an optional accessory for MC was available.

The NS 10 was the match for the first amplifiers from Threshold the CAS 1,CAS 2,400A,4000, Stasis 1,Stasis 2 and Stasis 3, were benchmarks not only for Threshold but the industry as well. Truly breakthrough products, that firmly established high end audio as we now know it.

Listed below are the design parameters and specifications for the Threshold NS 10.

The Threshold NS 10 preamplifier embodies design concepts and empirical performance that set new boundries for the classification" state of the art". The NS 10 utilizes a signal path so simple,so distortion free and so extraordinarily fast that it is virtually incapable of degrading any information passed through it which is in the range of human perception.

The model designation NS 10 is derived from the unprecendented propgation capability of the active circuitry expressed in nanoseconds.With its active circuit bandwidth of 50 mHz and through-the-system bandpass capability in excess of 1 mHz the Threshold NS 10 simply removes the realm of possibilty any chance for transient and phase anomalies to affect the signal. In fact the active circuitry of the NS 10 will introduce less alteration to high frequency waveforms than passing the signal down a 3 foot length of top quality audio cable.This lunatic fringe performance assures that the high frequency roll off of the system as a whole consists only of those passive losses caused by cable and input capacitances and not but undesireable limitations in the action of the amplifying circuits themselves.

A new level of resolution for the NS 10 has been achieved through biasing the active input devices to current levels an order of magnitude beyond those normally applied to solid state preamplifiers. These very large bias currents radically reduce the distortions in the gain transistors, yielding a " super Class A " operating mode where the idling currents are many times larger than the current called for in active operation. In addition to high linearity,the large bias increases the magnetic phono input transistor overloand point to approximately 2 volts measures at 100 kHz so that the only possible overload occurs when the output swing reaches the supply voltage of 24 volts.

The Threshold NS 10 is a component of extraordinary performance that will radically surpass the capability of any source equipment or amplifier and loudspeaker with which it may be associated.


Description: Two channel,low signal level processing component having selectable input facilities for two velocity characteristics phono cartridges, four constant amplitude preamplified sources and record/monitor facilities for two tape recorders. Two pair of preamplifier outputs are provided as well as front panel controlled power for the Threshold preamplifier accessory modules.

Frequency Response: 1Hz through 50mHz

Rise Time: 25 nanoseconds

Propgation Time: Input to output propgation delay,approximately 10 nanoseconds.

Through the System Specifications:

Frequency Response: +0,-3dB 1Hz through 1 mHz

Distortion: Total harmonic and intermodulation distortion less than .005 percent at 1 volt output for both phono and high level stages.Below test equipment residual for distortion components higher than 3rd harmonic.

Maximum output before clipping: 10 volts peak

Magnetic phono input stage overload point: 1 volt peak at 20 kHz, 2 volts peak at 100 kHz

Slew capability: Maximum voltage slewing rate 100 volts per microsecond.

Impedance: Magnetic phono inputs 47 kohms, high level inputs 225 ohms, preamplifier outputs 1 kohm

Gain factor: Magnetic phono stage + 40 dB at 1 kHz, high level stage variable to + 20dB

Hum & Noise: -70dB unweighted through magnetic phono stages,reference to 1 volt output 20Hx through 20 kHz

No doubt these are indeed lofty aspirations and the resulting specifications where totally unheard of for the time.

Although time and technolgy may have surpassed the NS 10, it remains to this day as one of the finest preamplfier designs built to date.

Virtually a service free preamplifier with only the power supply caps that need attention some 25 years down the road. Equipped with gold plated RCAs, which was also unheard of for the time.

The one I recently acquired was in very pristine condition and functioned as intended. It has been sent to Jon Soderberg of Vintage Amp Repair, for a complete check out and to have new caps installed, which will give another 20 plus years of service.

These are becoming somewhat hard to find now as the NS 10 was replaced early on by the SL 10. If memory serves me correct the NS 10 had only about a 18 month production run.Used prices for these in operational condition range from $300 to $450.00 and those with box and manual command higher prices.

Without question Threshold under the leadership of Nelson Pass knew that in the final analysis, that the true endeavour was the music and the accurate reproduction thereof. This total dedication to music remains the essence of all Nelson Pass designs, from Threshold to Pass Labs.

Few products one buys have enduring value. Look at how many cars or homes we have owned in the last 25 years, all in search of something better or so we think at the time.

But here with Threshold was and is products that stood the test of time and continue to deliver the promise, many years since they were new. The reason for this is quite simple. Extraordinary design, coupled with great craftsmanship and a build quality that was and is second to none, even today.

After 47 years in this hobby and owning more gear than I can remember and a lot of it Threshold/Forte/Pass Labs here I am back in the beginning of high end with the NS 10 and 400A. Once again I have that super silly grin on my face, that has not been there for sometime and once again I am discovering the true joy of high end and its promise.

The Threshold NS 10 is a visionary preamplifier from one of audios most gifted designers and after all these years continues to deliver the promise as intended.

So now my system is basically back to the beginning, or back to the future in some ways. The Threshold NS 10 Preamp is driving a Threshold 400A amp with Alon Model 1 speakers. With all this Threshold recently serviced and
sounding as good as ever, it appears that I have returned home and thats a very good feeling for once. Now at 62 I
can finally get off the train, the trip is complete.

Associated gear
Click to view my Virtual System

Similar products
Threshold,Classe,Marsh,Forte,RGR,NAD, and far more others than I can possibly list.
Enjoyed your review. I've always been a Nelson Pass fan, and was the happy owner of a beautiful NS-10 until I sold it 3 years ago.

Enjoy your audio happiness!
Have just found out from Jon, that the NS 10,that is the subject of this review is a Threshold prototype NS 10, with the blue and gold circuit board and other refinements not found in the production units. Fortunately he has not only the knowledge, but the necessary parts to totally restore this unit. A great find and a real keeper. A wee bit of Threshold history.
From Nelson Pass:

I'm very pleased to hear that the NS10 is still working out for
you. The M1 remains a unique circuit that no one seems to
have copied, much like the I/V converter of the D1.

Also, I'm pleased to hear good things about Jon, as we continue
to recommend him for Threshold service issues.
I was also a happy owner of an NS-10 for about 5 years (79 -84) until it was stolen along with a very cool SAE MK-VI Tuner (Nixie tube digital readout!). The preamp was very clean and quiet. I had my Threshold 4000's gone through by Jon a couple years ago and they sound a work great.
Some of you may want to visit this link, where many of the diy users are learning and building the NS 10, plus some posts from Nelson Pass as well.

Clearly one of audios greatest pre amps.
I just bought a pair of 1.6 maggies to go along with my DR2 Classe amp. I have a Threshold NS 10 amp that I haven't used for about three years. We moved and I haven't set up my stereo since then. I'm now starting to miss my music so here I am. This is my question. With my DR2 and NS10 amp, should I upgrade the pre-amp for the speakers? I was thinking of the AR SP16. Does my NS10 compare in any way to the AR in bringing out the finest detail in clarity and imaging for my maggies? I don't want to spend the cash if I don't have to.
Just would like your input on this. Thanks. Ralph
I have not heard a NS 10 with the Classe DR2 amp. If the DR2 was mine I would pair it with a Klyne preamp or the Classe DR 7 preamp. Seeing as the Classe DR 2 is a pure Class A output amp, it needs to run 24/7. Turning Class A amps on and off frequently shortens the life of a Class A amp. The ARC SP16 is a tube preamp and a good one as well. But to leave it on 24/7 will shorten tube life and may not be a good match to the solid state DR2. It is always a risk to mate tube to solid state. Sometimes works very well and at other times is a total mismatch. Sometimes with unpleasant consequences.

In my opinion if your going to spend the kind of money that a ARC 16 will cost you, I would call Stan Klyne and have him build for you, precisely what you want.

The NS 10 you have will need updating. Jon Soderberg has done two of these for me and they sound marvelous, once updated. Usual charge is about $200.00 to $300.00 for the update. this would be the most cost effective to achieve to your goal.

The DR 2 is a marvelous amp and in my opinion clearly one of the ten best ever made. Just a glorious signature, that is not often found.