I just picked up a Threshold FET-10 HL for two channel playback, and all I can say is "WOW-What a preamp". This unit has provided a major upgrade for two channel audio playback.
I was using a Krell Showcase for all preamp playback, and while it is a fine preamp/processor, it's not in the same league as the FET-10 for two channel playback. The lite haze one usually hears with most audio playback setups is simplly not there with the FET-10.
For now, using the FET-10 with a newly refurbished Nakamichi PA-5, and the results are stunning with Legacy Signature III's. Can hardly wait to finish getting the two Nakamichi PA-7's refurbished.
Later this year, will be refurbishing the FET-10. The power supply would be a no brainer to refurbish, but how much and what should be refurbished on the main unit itself. Want to make sure to keep (hopefully improve) this level of sonic clairty.
Thanks in advance for any advice.
I was using a Krell Showcase for all preamp playback, and while it is a fine preamp/processor, it's not in the same league as the FET-10 for two channel playback. The lite haze one usually hears with most audio playback setups is simplly not there with the FET-10.
For now, using the FET-10 with a newly refurbished Nakamichi PA-5, and the results are stunning with Legacy Signature III's. Can hardly wait to finish getting the two Nakamichi PA-7's refurbished.
Later this year, will be refurbishing the FET-10. The power supply would be a no brainer to refurbish, but how much and what should be refurbished on the main unit itself. Want to make sure to keep (hopefully improve) this level of sonic clairty.
Thanks in advance for any advice.
I just helped a friend refurb a FET-10. No electrolytic caps in the main unit to worry about. Some larger polyester caps could be upgraded, but I couldn't find any polypro caps that would fit, so I left them alone. I did replace the caps and diodes in the power supply. He is extremely happy and says it is a huge improvement over the Krell preamp he was using. He needs a phono stage, so I told him to wait for the Pearl 2 which I hope will start shipping soon..... (Hint, hint Wayne
)
I got the parts for this from my tech buddy, so not sure of the make/model, but believe it's a HEXFRED type. (You can see it pretty clearly in the pic). I do know that they go for 25.00 a pop, so it's going to cost me 100.00 to install them in the two PA-7's. They made the amp a fair bit quieter, as did replacing the internal wiring.
I'll ask him where he got them, and who made them. I'll post as soon as I find out.
Red,
I refurbished an FET-10hl last fall. Here is what I did.
Since it's a 20 year old unit, I was certain that the old electrolytic capacitors needed to be replaced. There are not many electrolytic capacitors in the unit - only 2 for the external power supply (2100uf 35v) and 4 in the on board regulators (4.7uf 50v). I replaced the 2100uf electrolytics with some Panasonic FC 3300uf 35v capacitors and while I was making changes I also upgraded the power supply diodes to some Fairchild stealth soft recovery diodes - model RHRD660. The 4.7uf 50v electrolytic capacitors were replaced with some ASC 4.7uf 50v film caps that I found at a local surplus electronics store.
The output of the preamp is capacitor coupled with some 10uf + 10uf EPCOS film caps. These aren't the best quality caps but as Mashbill pointed out, they are compact. The low profile of the preamp means that there isn't room to fit higher quality 10uf film caps and still fit the top panel. Instead of replacing these caps, I decided to bypass them with some film caps that I had in house. A combination of a 1uf 100v Hovland polypro musicap + 0.1uf 100v Sprague Vitamin Q Paper in Oil gave a very nice improvement in soundstage. I also experimented with the orientation of the EPCOS caps and I think things sound with the EPCOS flipped around 180 degrees - i.e. the input swapped for the output.
Future changes that I'm considering are building a bigger power supply to replace the very small external supply and putting in a stepped attenuator to replace the volume control.
For others interested in experimenting with this preamp, here is a schematic of the gain stage from the 10/hl. I have not included the power supply or regulator schematic.
---Gary
I've been using the FET-10/HL for the past year and half... it's my favorite linestage so far, supplanting my DIY 6N6P tube unit.
Gary B - thanks for the parts list as I've been looking to upgrade the power supply parts.
For phono, don't forget the companion FET-10/PC. It's the best I've heard so far... very natural and neutral.
Gary B - thanks for the parts list as I've been looking to upgrade the power supply parts.
For phono, don't forget the companion FET-10/PC. It's the best I've heard so far... very natural and neutral.
There were flat oval-shaped axial polypropylene caps that could replace the standard 10uF green Ero Roederstein MKT1813 and yellow CDE caps of the FET-ten/hl without having to lift the rooftop.
Plenty of NOS places that might have some.
Redwingnine
Your preamp looks great.
If you are updating the preamp then I think you will find the biggest change will come from replacing the volume control with a stepped attenuator using discrete resistors. I recommend the ladder type where each change in the attenuator uses just two resistors. I use 23 step attenuators. I have not found any carbon or plastic volume controls that can equal a ladder type attenuator. I think you will be surprised by the difference this makes.
Other than that you might improve the power suply - making the supply cleaner and better regulated. For your pre amp I think that using a power supply with a pass transistor on the positive and negative lines is sufficient ( As Nelson Pass uses on some of the Pass labs preamps ) A disc pre could use better regulation.
Please provide more pics as you update.
Don
Your preamp looks great.
If you are updating the preamp then I think you will find the biggest change will come from replacing the volume control with a stepped attenuator using discrete resistors. I recommend the ladder type where each change in the attenuator uses just two resistors. I use 23 step attenuators. I have not found any carbon or plastic volume controls that can equal a ladder type attenuator. I think you will be surprised by the difference this makes.
Other than that you might improve the power suply - making the supply cleaner and better regulated. For your pre amp I think that using a power supply with a pass transistor on the positive and negative lines is sufficient ( As Nelson Pass uses on some of the Pass labs preamps ) A disc pre could use better regulation.
Please provide more pics as you update.
Don
Any brands, part numbers that you could suggest? My friend's unit had the green Ero Roederstein MKT1813 caps in it.
The Dearborn 731P series is an attractive option, body size of the 160Vdc type in 10uF is roughly 0.6" x 1.0".
Their 10uF oval 734G series may likely be too big.
Others : Paktron FPF, American caps VW2, Electrocube 935B series.
Cornell and Illinois cap manufacture ovals, but from 600Vdc and not in 10uF, too large anyway.
A phono and line stage in separate cases and an extra powersupply have better noise/separation numbers, theoretically.
The FET ten/hl, FET ten/pc, and FET nine were manufactured in the exact same period, no need to use other than the same line and phono circuits in the FET nine.
My favorite combo was the FET ten/e balanced inputs/outputs series, see attached pic for circuit details.
Biggy overhere : http://img380.imageshack.us/img380/4033/s6300714zx6.jpg
(the later Bladelius designed T2 preamp model is a totally different animal)
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