gofar99 Messages: 1947 Registered: May 2010 Location: Southern Arizona
Illuminati (5th Degree)
Hi music lovers, I have been working on a pair of KT120 Push-Pull Class A U/L mono blocks for some time. As soon as the tubes became available I wanted to try them. Some of you may have seen the amps at the LSAF. Since then I have been tweaking them to get them up to the power they should. Well they now can deliver 45 watts RMS into 8 ohms before going sour. This is great, except the tubes are not as linear as some other members of the KT family. Without using huge amounts of NFB the compromise I reached was extremely low (under 0.25%) distortion at 1 watt, under 1% at 10 watts, 1.5% at 20, and increasing linearly to 4% at 40 watts. The sound is quite good, but not IMHO as good as the EL34 and KT88 Oddblocks. A bit more "clinical" or less warm, than the smaller amps. Then again, for power they can't be beat with any other valve class A design I know of. Large, robust sound. I'll post the revised schematic in few days.
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Some of you may have seen the amps at the LSAF. Since then I have been tweaking them to get them up to the power they should. Well they now can deliver 45 watts RMS into 8 ohms before going sour. This is great, except the tubes are not as linear as some other members of the KT family. Without using huge amounts of NFB the compromise I reached was extremely low (under 0.25%) distortion at 1 watt, under 1% at 10 watts, 1.5% at 20, and increasing linearly to 4% at 40 watts. The sound is quite good, but not IMHO as good as the EL34 and KT88 Oddblocks. A bit more "clinical" or less warm, than the smaller amps. Then again, for power they can't be beat with any other valve class A design I know of. Large, robust sound. I'll post the revised schematic in few days. 
