1) C1 and C2 - 47uf capacitors located right where the power supply comes into the preamp.

The have been replaced previously, with bigger value (300µF if I remember correctly) by my favorite technician. It does make a big change, just a very very little one, and I am unable to say if it makes an improvement or not.
2) C3 - this is a 2200uf capacitor associated with the time delay relay. I don't think this will have any effect on the sound but it would be a good idea to replace it to extend the life of the preamp

If you look at the photography, it has been replaced with the best possible NICHICON KZ. The original capacitor was also a NICHICON, but not of this high level of quality.
3) C7, C8 - these are capacitors associated with the servo loop on the plug in gain modules

4) C6, C7 - 220uf 10v, these caps bypass the zener references on the voltage regulator boards

I have to open the box to see where are located these caps: if they are where I assumed they are, I replaced them a few months ago with the best NICHICON KZ available. I am not sure but I believe I already did it.

Hi vick,

It is always possible to upgrade the original power supply by building a new one, with the same diagram, but with a bigger transformer and better parts.
But if you want to really go a big step further than the original power supply, you have to follow the route that I described in the original Threshold Lovers article and build a more sophisticated power supply.
The minimum sophistication is the one described in this article. The best would be to go a bit further by adding some filters after the p.s.: this will be described in the v2 of this power supply.

I have personally not looked inside a Fet-10HL preamp (but I have the skematics) , but there is no doubt that if you perform an upgrade similar to the one described in the article, you will get a huge improvement...

Feel free to ask if I can help you,

[Question from John Etnier] received on September 21st, 2013
While I wait for permission to post, can you tell me if the Version Two power supply of the Threshold FET ten preamp project was ever completed? I can't find any reference to a completed PS at the site.

Also, any schematic of EITHER version one or two would be much appreciated.

Many thanks!!!

All the best...

YES: the version 2 of the "Fet-10 He competition upgrade" has been fully completed for a few months. It has not yet been published on our Thresholdlovers.com website but it runs in my home...

Nevertheless, for the time being, there is no musical benefits to build the v2 of the power supply, which is much more complex and costly than the version 1.
I have a very precise idea of the cause (i.e why it does sound better than v1 yet) but will not have time to fix it until I have completed my current projet (meaning a few months).

So I recommend you to proceed with the version 1 of the power supply upgrade, and of course with the upgrade of the preamp itself (do not forget the Goldpoint attenuators...). If you start to build it, send me a MP I will give you a recommandation that is not commented on the diagram.

The full diagram of the Power Supply upgrade version 1 can be downloaded from this link:
http://www.thresholdlovers.com/file/Threshold_Fet-10He/alim_v1.00_fulldetail.zip

If you perform a Fet-10He upgrade, please share it with us on this Forum !
All the best !

Hi John,

The link has been inserted in the above message.

If you start the building , contact me by MP for a tip regarding the power supply.

See you soon,

Thanks: that's a wonderful document, containing as it does a BOM and so much info (like: I've been trying to figure out what Tajimi connector I had to buy). I will PM soon.

You are right: it took me a lot of time to find the exact reference of the TAJIMI connector.... But it is time for me to share this "secret" 😀 ...
I have two FET ten/e devices: the line preamp and the phono. I want to build up these supplies for them, but I can't help thinking it might make more sense to specify, say, a slightly larger (400va) transformer and put the two supplies into one cabinet? Or is one supply adequate for two preamps (I would doubt this)?

My experience is that the Upgraded Power Supply (the one you have downloaded the schematic) is more than largely enough for powering the 2 devices ! The original stock power supply from Threshold had a 70VA (max) transformer, where I put a 300VA in the upgraded P.S. with huge capacitors : there is NO chance that these 2 devices reach the P.S. limit...
Of course you can build a P.S. for each device for "intellectual pleasure", but I doubt this makes a sonic difference, although I perfectly understand your quest for the best possible approach and the reasons you may want 2 P.S.. At max, you can maybe expect an improvement because of the separation of the P.S., but not because of a limitation in terms of VA or power.

In my opinion, the quality of some parts, such as the stepped attenuators or the RCA connectors may bring a bigger improvement.

A route to consider is to:
-first build a single P.S. with taking a lot of care to the other parts quality (such as stepped attenuators and so on...)
-in a second step, build a second P.S. to see if it transports you to another level of nirvana...

All the best,