I am not sure what the loss of feedback is, do you any thoughts about the best way to determine that?Firestorm wrote:The published 5F1 schematic shows both triode stages unbypassed, but all the factory-original 5F1s I've seen had a 25uF across the first-stage 1K5 like on the 5E1. I didn't think to keep notes whether they were early or lateRJ Guitars wrote:I added a 25uf bypass cap to the 2nd gain stage and it really started to come to life.... but not ideal yet. I think I should have added it to the first gain stage but I'm going to leave it at as is and start prepping some chassis now. I'd like to get a few of these out to you and and let everybody join in the joy of tweaking them into submission.
rjBy putting the cap on the second triode, how much negative feedback do you lose?
I am considering taking a couple ideas from "Merlins" book on preamp design and using a 25uF across the 1.5K cathode resistor on the first stage then going with a 1uF bypass on the 2nd stage.
I couldn't find a voltage chart for the 5F1 but I do have one for the 5E1 which apparently uses the same power tranny. Right now my voltages are really close to the 5E1 values.
I had assumed that the 5F1 was newer than the 5E1, but it kinda seems like they took a step backwards if that is the case. The sound I got with the 5F1 circuit was cool but I had to use the bridge pickup on my Stratocaster to get enough treble for it to be useful. I got a lot more treble once I added that bypass cap.
I should mention that it isn't necessarily a lack of brightness as much as it might be a dominance of lower frequency response. Still early in the process of sorting that out but it is getting down to the fun stuff now...
rj