#61 Re: Another go at PP -> IT -> PP
Posted: Sun Nov 06, 2022 6:59 pm
Still thinking about trying to shrink this down. When I originally tried the followers, I was using the sowter step up transformers for gain, so without the followers I was driving the output stage with quite a high impedance. I preferred the sound with the followers. I repeated the experiment with the valve gain stage and again preferred the followers, but at that time I wasn’t using the mu output of the CCSs, so again the driving impedance without the followers was quite high.
Today, using the mu output, I again tried without the followers and again didn’t like the sound. I was trying to figure out why. The followers weren’t the only variable…
With the followers I’m able to use a 1Mohm resistor after the coupling cap, which means I can use a small cap. Without the followers I’m limited to a 50kohm resister so I need to use a larger cap.
For the small cap I’m using some ERO KP1832 film and foils, my favourite caps, but I don’t have any larger than 0.075uF, and they don’t make them anymore. For the large caps I’m using some ‘decent’ film caps that I used in the past for speaker crossovers.
Still without the followers, I tried bypassing the large caps with the EROs, and the magic was mostly back.
Losing the followers will allow me to eliminate a toroidal transformer, a positive and negative supply, and quite a lot of heat inside the chassis. But I’ll need 4 caps of at least 1uF, that are as good as the ERO film and foils. I’m considering the Mundorf M Cap ZN, tin foil and film. Any other suggestions?
Today, using the mu output, I again tried without the followers and again didn’t like the sound. I was trying to figure out why. The followers weren’t the only variable…
With the followers I’m able to use a 1Mohm resistor after the coupling cap, which means I can use a small cap. Without the followers I’m limited to a 50kohm resister so I need to use a larger cap.
For the small cap I’m using some ERO KP1832 film and foils, my favourite caps, but I don’t have any larger than 0.075uF, and they don’t make them anymore. For the large caps I’m using some ‘decent’ film caps that I used in the past for speaker crossovers.
Still without the followers, I tried bypassing the large caps with the EROs, and the magic was mostly back.
Losing the followers will allow me to eliminate a toroidal transformer, a positive and negative supply, and quite a lot of heat inside the chassis. But I’ll need 4 caps of at least 1uF, that are as good as the ERO film and foils. I’m considering the Mundorf M Cap ZN, tin foil and film. Any other suggestions?