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leftThreshold - Fet-10 He preamp review
Welcome back for a new review of a mythic Threshold device ! The article is not yet fully written, so this is the first part only... The ranking will be probably delivered in the 3rd quarter of 2009, and a high quality upgrade is currently designed for a target implementation in the 2nd half of the year.

A few weeks ago, I acquired a THRESHOLD FET/10 He preamplifier. As you can see on the Threshold Product Line History page, this preamp was built from 1990 to 1994. It is during this period that the most interesting devices were manufactured by Threshold, -such as the famous SA amplifiers line operating in pure class A-, when Nelson PASS was still the Chief Designer...
The FET/10 He is the last evolution of the Fet/10 line of preamps, the first one being the original Fet/10 released in 1987.
The Fet/10 He is a true Nelson PASS baby, contrarily to the T2 for example.


As you can see, the Fet/Ten He is "small" if we look at its size, but despite its small volume, the THRESHOLD Fet/Ten He was considered as a  "state of the art" preamplifier when it was released in 1990. As for the other famous THRESHOLD preamps, the power supply is housed in a separate box:


One of the most famous French high-end reseller, named "COHERENCES", had rated the Fet/Ten He as an absolute reference in 1992: just have a look  at this page (which is also available in the "Photos" section) amongst a few other high end devices listed herebelow:
  • PIONEER Exclusiv C7 (surprising, but visibly a confidential device)
  • CONRAD JOHNSON Evolution 20
  • JEFF ROWLAND Consumate
  • METAXAS Opulence
  • CELLO Audio Suite

The COHERENCES rating was a very serious rating and one of the most respected notation in France at this time.

1-.What is inside the box ?

This is a question I like to ask, because I believe that actually, the people care more about the look and the appearance, than about what is of the highest importance for the sonic reproduction: the inside design and parts !
So if you (or your wife, or both) are looking for a super sexy preamp having tons of buttons, and hundreds of tone correction curve parameters with a "Star Wars style" remote control, then please have a look to the last BANG & OLUFSEN products: you are not at the right place here...

I will not write, once again, how much I am disappointed when I see the current productions of the world most famous brands such as MARK LEVINSON, INFINITY, or even KRELL, compared to the beauties that they produced in the 1990s... no, do not insist, I will not complain once again !

So back to, and into, the THRESHOLD Fet/Ten He preamp, just by using a global view:


The review of the THRESHOLD Fet/Ten He was done with the Reference System 1 and later on with the Reference System 3, but only using the THRESHOLD SA/6e Class A monoblocks amplifiers.
We firstly start with the Reference system #1 in order to start with a system we perfectly know and also in order to compare the sonic performance of the Fet/ten He against the U-T2 (*) on two pairs of speakers, the THIEL CS-2.0 and the PROAC Response 3.8.

(*): the U-T2 acronym stands for the upgraded T2.

Don't you see anything surprising for a "state of the art" ranked preamp able to manage a lot of different sources ? How does the inside look compared to the current preamp devices ?

OK, the power supply is external, which is obviously an excellent decision, but what else ?

The answer is sim-pli-ci-ty ! There is only a few parts, much less than in the majority of the current preamps. This is the Nelson PASS approach, perfectly explained in his paper: "Simple sounds better", available for our members in our download section.

The Fet/Ten He is built with:
  • a main board using very large printed rails, on which are plugged...
  • six small daughter boards, 3 for the left channel, 3 for the right channel
  • the RCA/XLR connectors are screwed on the chassis but no directly on the mainboard
  • the controls (input selector, balance, volume, etc...) are also screwed on the chassis, not directly on the mainboard.
The six daughter boards are the equivalent of the "modules" that we found on the current high end preamplifiers, such as the excellent VIOLA for example (see note 1), but they offer a big advantage: in case of failure, they are easy to repair ! If a module gets out of service, then you do need the manufacturer to repair... and if the manufacturer does not exist anymore, or has internal problems, you are...dead.
These daughter boards are mechanically isolated from the main chassis, which is obviously a good point.


The internal parts used belongs to those traditionally used by Nelson PASS at this time: only discrete parts, and for a lot of them, the same than those used in the SA serie amplifiers.

All the components implemented in the Fet/Ten He are of a good quality, and are not the low cost "made in Taïwan" parts that we (too) often find even on the high end devices. All of them are still manufactured, and consequently, a Fet/Ten He is still  very easy to repair in a pb occurs.


Just take a few minutes to think about some actual preamps (or amp or other device) that use modules or a lot of onboard software / CMS parts / low cost parts (meaning going out of production after a few months/years): the super sexy toy that you have paid 15.000$­­­­­­­ cannot be repaired if the manufacturer fails or disappear....
Do not smile
: we know a lot of people that currently have their beauty on a sleeve for months, without any hope to get it back to their listening room because the manufacturer has closed, went to bankrupt, or because the importer does not make his job properly ! this is not a rare story at all....

By going to this kind of preamp (the Threshold Fet/Ten He is one of the finest transistor preamp), you get both a State of the Art preamp, a very cheap one (at 1.500$­­­­­­­ it can compete with the current 10.000$­­­­­­­ or more preamps...) and your investment is protected because it is easy to repair in case of failure !

The internal parts are for a lot of them, also used into the Threshold SA series amplifiers, also designed by Nelson PASS:
  • MPS-A92, PN-4250A from FAIRCHILD, MPS-A18, 2N-5566 from VISHAY
  • 8 capacitors (not in the signal path) are identified as "Wondercaps - Ultima with Danor" 0.1µF / 425V, and one is identified as a NICHICON, 2,200µF / 20V (blue model).

  • the other capacitors are more standard grade, generally they are ELNAs
  • the volume  and Balance potentiometers are manufactured by NOBLE (black model), one of the best manufacturer we can find in the potentiometers gear.

  • the contactors are from GRAYHILL:

This level of quality in the building is very rare to find nowdays, and locate the THRESHOLD FET/Ten in the equivalent of 10k$­­­­­­ to 15k$­­­­­­ range of the current preamps.

A point of disappointment compared with what we can find on the other state of the art preamps, is the use of a potentiometer instead of a stepped attenuator such as a DACT for example: the JEFF ROWLAND Coherence One used a stepped attenuator as many other state of the art preamps.

There is no doubt that an upgrade with a stepped attenuator would bring even more transparency to the Fet/Ten audio performance: I cannot promise you that I will not implement such an upgrade in the future...

here are the 2 NOBLE potentiometers used for the Volume and Balance

2-.And what about the Power Supply ?

The power supply is external, like on most of the state of the art preamps, and is big enough for a lot of the current Chinese power amps... It is smaller than the T2 one, but it has far less parts to feed because the Fet/Ten uses only a few parts and has no LCD or no remote control to power !

The power supply uses an AVEL transformer Model CE5241 made in the UK, and 2 x 15,000µF/35V capacitors, identified by a long reference but I have not been able to find their coutry of origin nor their manufacturer.
Updated on March 2010, 13th: the capacitors are manufactured by SPRAGUE, which is therefore a VISHAY company. A full diagram of the power supply has been done with the Easy-SCH ® software and the various voltages are identified. But I have been informed by Threshold that different versions of the power supply had been released.
I also take this opportunity to congratulate THRESHOLD (I mean the current Threshold company) for the outstanding quality of its aftersales service: it is still very easy and quick to get spare parts for the old SA serie amps as well as this preamp. Contact by email, immediate answer by a (qualified) technician who perfectly knows this old products line, and the capacitors were in my home 4 days later ! I really want to emphasize on their quality of service because I know  too many persons owning a (current)
« state of the art » device who are in a total mess because of the manufacturer or because of the importer...(I am just still looking for a Threshold logo plate, but they do not  want to sell this item, so if one of you owns such a plate...).


There is no doubt that some of the parts, particularly the capacitors, should be changed after years of service, but as we will see later on, the audio performance of this preamp is simply outstanding...

To be continued soon...

note 1: I would like to express my sadness because of the recent death of Tom Colangelo, who was one of the two founders of VIOLA LABS, one of the rare remaining companies really committed to high end products. He had worked with MARK LEVINSON for years (before the company were bought by Harman International) and successfully designed some of the worlldwide very best preamplifiers at VIOLA LABS.

Creation date : 15/07/2008 @ 17:23
Last update : 20/03/2010 @ 19:41
Category : Threshold
Page read 19192 times

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react.gifReactions to this article

Reaction #9 

by Nounours18200 17/06/2010 @ 20:43

Hi ad2000,

I believe it is possible but I do not have the skematics under my eyes at the time as I am not at home. I encourage you to email to POWER ELECTRONICS (give a call if does not reply to your mail). He has tuned my Fet-10He and made a superb work...

Reaction #8 

by ad2000 17/06/2010 @ 09:42


One channel of my FET 10e outputs significant DC drift voltage. Meridian power amp 557 protection circuit may active and cut the power sometimes. I found there are some VRs on the FET 10e circuit board. Is it possible to trim the output offset voltage?

Reaction #7 

by Stefan 19/05/2010 @ 12:53

I do not fully agree. The main caps are not directly in the signal path. As long as you hear no noise it would not be a good reason to replace them.

In the case you want an upgrade for the main unit you can go with either the Wonder Dynami Caps and if you have Infnity or Genesis loudspeakers you would be more happy with Rodenstein or Lima caps. Those caps where also used in the Genesis Stealth amp and in some crossovers for Genesis loudspeakers too.

Any other update would be more speuclating and I have seen lots of Thresholds equipment upgraded incorrectly, so knowledge and years of experience is neceassary to do it correctly.

If somebody come of the idea of using Mundorf caps, he hasn't understand what Threshold is all about!

Reaction #6 

by Nounours18200 13/03/2010 @ 20:52

Hi Kev,

The answer to your question is available in our Forum, here:

Kind regards,

Reaction #5 

by Kev 13/02/2010 @ 18:35

Hello everyone, i was just wondering, if i have one of these used that i received from a relative, how much would it be worth? in good condition, no nicks or scratches, just used.

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