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soundbadger 10th October 2007 12:18 PM

Single Ended Amp Design -- Help Needed
hello there
i am trying to design a single ended amplifier based on the kt88 beam tetrode. i have beed told i want about 40 - 45 volts peak to peak input in to the kt88 for optimum performance.

from this i decided to use a 6sn7 for the driver stage, i played about with load lines for the 6sn7 for a while and found a simple common cathode stage using 1/2 a 6sn7 could provide a voltage gain of about 16 which would be perfect to turn a 2.88 pk-pk signal (1Vrms) in to a signal around 45V pk-pk.

is this single stage enough, or should i consider other options to obtain higher gain,,, an srpp based on the 6sn7 for example.

i was wondering about possibly having more gain available at the driver stage for low recording levels on music,

any thoughts?



Sherman 10th October 2007 01:51 PM

Search the forum for "Mikael's KT88". It is a single-ended KT88 design that several members have built. It uses 1/2 a 6N1P for the voltage amp. In mine I get between 7 and 8 watts with that schematic. Based on that you should be OK with your setup.

I use my amps (I built them as monoblocks) with CD, tuner, iPod and cable TV and all work fine as sources. I also use a turntable but of course have a phono preamp for that.

soundbadger 10th October 2007 03:59 PM

thanks, but your kind of missing the point.

there are hundreds of amp schematics out there i could build that would work and im sure lots of them are great. i have looked at mikaels amp in detail and even drawn its loadlines to get an idea of its operation. however i am trying to calculate everything myself,,,,

kevinkr 10th October 2007 05:22 PM

The 6SN7 will be adequate with a line stage that has some voltage gain driving it, consider the 6SL7 in SRPP - enough gain to do the job and run at 2mA should provide enough drive to deal with miller capacitance out to 30kHz or so.. (Triode connected, UL not an issue.)

I used 6SL7 in SRPP to drive my cheap and cheerful 45 SE amplifier - it's the oldest amplifier I still own, and sounds good within its limited power capability. Supply voltage to the SRPP would need to be over 300V for best performance.

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