Tuesday, August 31, 2010

Upgrading the Threshold FET-10/HL linestage


My beloved Threshold FET-10/HL linestage is getting a little long in the tooth. The few electrolytics need replacement and the couplers are due for an upgrade as I'm no fan of Mylar capacitors.

I first tackled the Power Supply, replacing the original four diodes with UF4007s. It's hard to find quality axial capacitors and the outboard power supply is too small for fitting in radial capacitors. With that in mind, I ended up replacing the 2200uF/25V electrolytics with 3300uF/35V Nichicon FGs.

Next up is the actual signal unit. 4.7uF power supply bypass capacitors were replaced with Elna Silmics. Inside, it's a tight fit height wise with the input and output coupler capacitors. So I used 1.0uF Rel-Cap PPMFs on the input and 10.0uF Wima Polycarbonates on the output section. This is a much improved upgrade over the original input film and output metallized Mylar capacitors.

How does it sound? Polycarbonate have always been some of my favorite 'sleeper' capacitors and once again they proved their mettle. They are much superior to the original Ero Mylar capacitors with a cleaner, less fuzzy soundstage. There seems to be more minute detail too. The combination of the new parts makes for a much better preamp and a brings this old girl back up to world class level again.


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