Cathode CCS based PP amp KT88

[tikiroo]

I'm not going to model CFB, it is too time consuming. By definition 6dB feedback means half the gain. For triode no feedback you need 1V rms for full power (~18W for a low loss transformer). So 2 V rms for 6 dB feedback. For UL at the same power it is 0.55V rms no feedback, 1.1 Vrms with 6 dB feedback. If you bypass the CCS's for UL at the same 0.55Vrms, power increases to 24W and distortion drops by a factor of 4 (even less than triode distortion).

 

[Staticx]

tikiroo:
Thank you for results. Now I have to build the circuit and make measurements and listening tests.

 

[Staticx]

tikiroo:
And are you sure that your sensitivity values are RMS values and not peek? According to my simulations in paint_kip/kit, it looks more like it's Vp.

 

[tikiroo]

Yes they are rms. The issue is that the simulation shows a quite large ac signal on the KT88 cathodes if you don't bypass the ccs. This reduces the sensitivity compared to what you would calculate from the curves.