You really got my attention. Can we pursue this for a bit? I feel like this one put me in a fog. I've got hiss beyond what I'd like. Are you suggesting that there is a direct relationship between noise and Vk? This would be new territory for me.skyboltone wrote:balance pot artificial center tap, bottom plate firmly attached to chassis. Express presence control, francesca layout, shielded volume pot to v1b, 33k grid resistor on V1a. Oh, I almost forgot 1.8k Rk V1a/b. This depends on your K voltage. I only had 1.02 on A and .89 B. This bumped both cathode voltages to about 1.33 with my 174 volt plates on V1. Cut the noise a bunch, I may pull the 33K resistor.
sorry to keep beating the same drum but my TW is silent
from thread: Noisy Express
I can't measure anything in my TWX right now because I'm waiting for a replacement OT (egad, don't ask; it'll be here in a day or two).
My records indicate that V1A Va=193 Vk=1.26 and V1B Va=276 Vk=4.42. I used the "Kelly 90" schematic, so the R/C for V1A is 1k5/22mf and for V1B it is 2k7/22mf.
I didn't think much of it, but I'm really disliking that Vk=4.42. Don't know if that's significant or not, but your post (from another thread on noise) makes me want to explore this.
Is there an ideal target for voltages on V1? What do you think they are? Suggestions on how to get there?
The amp has shielded in to both grids on V1. That helped some, but not enough. 5751's helped too, but I keep thinking this could be better and that 5751's aren't the "right" answer. (Cheating!)
If I can find something to use for a bias pot without spending an arm and leg, I'll do that, too.