Sonic improvement with Threshold FET 9 refurb?

Hi All,
In a recent post I was asking if anyone knew of an affordable ($1200 or so) sonic step up from my ARC SP14 preamp since a threshold FET 9 I had recently aquired from a fellow Agoner did not, to my ears. sound quite as transparent and holographic as the SP14. Very,very nice, yes, but not a step up. I didn't get any suggestions other than to upgrade the SP14 electronics and a comment that there was probably no affordable step up.
Anyway, after re-reviewing the glowing write-ups on the FET 9, I'm wondering if, despite its nearly pristine condition inside and out, my example might be a bit "tired". I realize that there is significant controversy about the need for capacitor replacement and or power supply upgrades and don't want to spend a lot of money trying to fix somethhing that is really working as well as it can, but am wondering if this might be sonically worthwhile. I would greatly appreciate hearing from anyone who has actual experience with this or a parallel scenario.

There were 3 versions of the FET9, which one do you have?


2)Original with “e” power supply (FET9 on unit and “e” on the supply)

3)Full FET9e (FET9e on unit and “e” on the power supply)
I update a lot of fine audio gear. I don't see the controversy. The fact is, most electrolytic capacitors last 15-20 yrs, less if they're in a hot environment or the equipment had been sitting for many years without being used. Rubber gaskets on the caps start to crack and/ or bulge (venting). Replacing them can also be considered a sonic upgrade if the type of caps used are chosen wisely. Fet transistors do not need to be replaced unless they get noisy.
Thanks for the input so far. My unit is the original with no e on the unit or power supply. I knew there was an e but was not aware that there was a "full e" that had more than just the upgraded outboard power supply. Are there substantial sonic differences?
Thanks Again
Contact Jon Soderberg at vintageamprepair. He is a Threshold/Forte expert rebuilder.
The “e” power supply was the most significant upgrade. Later the main unit was tweaked, with the addition of balanced input/output, and a slight cosmetic change.

Absolutely contact Jon Soderberg, he was at Threshold for many years during that time. I’m sure he could make your FET9 perform as well as any out there.
Thanks Folks,
I will contact Jon Soderberg next week but am still wondering if, following refurbishing, my unit will be an improvement sonically on my ARC SP14. If anyone out there has had a chance to compare a properly functioning "well tuned" FET9 or FET9e to an ARC SP14 I would greatly appreciate your impressions.
FWIW, as far as I can tell the differences between the FET 10 and the FET 10e is that the e series has a beefier external power supply with completely removable (and possibly upgradable?) umbilical cord, a set of XLR inputs and outputs (though neither set is truly differentially balanced), slightly different control options and layout, with different knobs and other cosmetics. I would think that the 9 series would have similar differences, and that a standard FET with e series power supply, would be at the very least comparable to a "full blown" e series.
I believe the SP-14 is somewhat similar to the SP-9. Both of these units had crosstalk issues. As frequency went up, crosstalk went up. This caused a problem with the image to some extent. It manifested itself as a whitish curtain between instruments in space and a lack of silence between them. I doubt the FET9 had the same issues as the SP-14 but remember, both units use older FET technology.
FWIW, here's a comparison of a newer higher end model Threshold FET 10 with an older model Audio Research SP 11 and a Klyne.
The SP-11 although an older design is also a very different design from the SP-14....
Hi Everybody,
A big thanks to all the folks who have helped me out on this one. I talked at length to Jon Soderberg yesterday evening and he said that I would get a significant improvement with a power supply which he makes which is an FET9e equivalent and with an upgrade recapping of the main unit. So, off it will go to him. I'll report on the results when it gets back to me in a few weeks, since there may be interest in the effects for others who have similar situations.
Thanks again,
FWIW, I just came across this: