I bought this on a whim to be modified. Unmolested this is a very good pre and bought used a steal. It compares very well to my modified Bottlehead Foreplay II. Bass is taught, mids(voice) are to die for, and the highs are snappy without sibilance. A very smooth pre that simply gets out of the way.
I began by rebuilding the power supply with FREDs, flash caps, and a poly cap. I have rolled various boutique coupling caps andfinally settled on the russian k40y9 foil in oil caps for their strong bass, romantic mids, and pristine highs. I also replaced the volume pot with a Noble stepped resistor pot .
I have rolled many 12AU7, 6189, 5814 type tubes through this amp with my favorites being the Mazda 6189 chrome plates, the RCA 12AU7 cleartops, and finally the GE triple mica 5184. The Mazda leans more toward a cool solid state sound. The RCA is a little warmer and a bargain on ebay. The GE has a more romantic tube sound and is a good bargain as well.
It easily drives any solid state amp I have thrown at it. It mates beautifully with my modded Dynaco stereo 70 and is very quite into a pair of Khorns. With its two pre outs vertically biamping with solid state and tubes yield great results with less effecient speakers. I believe that this preamps very simple circuit is the secret it to its exceptional sound. It is excellent as is, easy to modify, and I have no hesitation to recommend it to anyone.

I have been using this product for over two years. This unit was purchased from Audio Advisor and I think for the price it is one of the best bargains around. For $350 you get a very basic tube preamp that adds a touch of tubes to your music. It includes four gold plated line level inputs and two pairs of gold plated outputs. It comes with one 12AU7 tube. All wiring is point to point. It is an extremely quiet and pleasant sounding unit that goes well with my Quicksilver Mini Mono's driving my Acarian Alon 1 speakers. Although the bass is fairly good considering it is being used with a pair of 25 watt per channel tube power amps, I think the strength lies in the midrange. It is full and rich where I can almost picture the musicians in front of me. This is a very basic unit there is no remote, no phono stage, and no tape loop.
The one concern I had was reliability based on some of the comments I have seen on the internet. When the unit arrived it did have one loose screw rattling around, however, it was easy enough to open up and attach the screw and nut. I have not had any other problems with the unit since.
Highly recommended.