[size=medium]Score! A friend of mine brought over his headphone tube amp for me to try. He’s letting me use it for a few weeks in exchange for working on his bicycle, how sweet is that? [/size]
[size=medium]It’s the Extreme model made by Singlepower Audio Inc (apparently defunct). The L&R output tubes have makings: on the tube base, TUNG-SOL 3224705-3; on the glass tubes, 5633, 5998, 5. He gave me a set of “driver tubes” to try, the unit only takes one driver tube that have markings as follows. [/size]
[size=medium]2. 153, B4L2, 102, MADE IN GREAT BRTIAN. [/size]
[size=medium]3. KEN-RAD VT-99[/size]
[size=medium]4. JAN 6SN7WGTA, Philips ECG 8582, 34167 USA, ADB. [/size]
[size=medium]I’m using it with my Sennheiser HD650 phones. Currently, I plugged the analog stereo outputs of my Yamaha DVD-S2700 (CD, SACD, DVD-Audio) in the L&R inputs of the Extreme. Right now I’m listening to Dire Straights ~ Brothers in Arms, it sounds very good. [/size]
I use the Tung Sol 5998 and 5670WA with the K701s on the Extreme. Good bass, soundstage and crisp highs without being hot.
Check the temperature of the transformer cover after playing for a while. If it is hot to the touch, beware there are problems with some of the Extremes. The square transformer was undersized and improperly wired according to some members. Some of the covers were taken off and the transformer paper was toast and starting to smell. The round transformer units didn't have this problem (though some common design flaws are consistent throughout).
That caveat out of the way, the Extreme and 650s had a good synergy with the proper tube compliment. Use the search function in the amps forum to find some good tube threads. The amp is pretty good IMO.