Tube Amp Archive

Thanks. I am using electrolytics in the bias supply, and for the cathode bypass caps (just because I don't have room on the board). The DC heater system isn't actually hooked up, because it was actually quieter with AC. The power supply is standard arrangement. 47uF - Choke - 32uF - 10k - 22uF - 10k...

Yeah, it's not parasitic. Apparently, the plate to plate impedance for goes down when the plate voltage is that low. This would explain why a pair of 6V6's worked better (higher plate to plate to start with).

Angela SCR (Solen) Non-Polar power supply. The response of the power supply is very fast, but you lose some of the forcefullness in the bass frequencies. Overall, i like the sound. If you want to hear the effect without changing your power supply, change one of your cathode bypass caps with one of t...

I tried the preamp attenuation thing with no result. I should clarify that the amp works. Play guitar through it it sounds really good up to maybe 10 o'clock on the volume control. This point coincides with the screen grids drawing massive current and the output (on the scope) totally cliping hard, ...

Marshall / Bassman style preamp - push-pull output stage. Pretty standard design except for the Class A output stage at 250V with fixed bias and no negative feedback. The basic premise of this design is to get output distortion at lower volume.

Well, i had been thinking of going with lowering the value of the plate resistors and grid reference resistors in the phase inverter to 33k ala later Twin Reverb. Just haven't tried it yet. This should curb the size of the waveform, no?

Ron, just wanted to clarify, the plate is not dropping voltage, its dropping current. The power supply seems to be very stable. What are my options on making this voltage/current scenario work? Preamp attenuation?

Here's my problem. I just built an amp with 250V on the plates of KT66. 6.6K output transformer primary. Fixed bias with bias set at 100ma current draw. Here's the thing. Everything is fine until signal is applied. All of a sudden, plate current drops to practically nothing (measured at the plate), ...