stickjam
Well-known member
(If you feel a vague sense of deja vu reading this, I made a similar post in the Lab yesterday. I have clarified it a little and moved the topic to the Drawing board, as it's more appropriate, as it really is at the "drawing board" stage than a project under construction.)
I'm just getting back into tube work after a 35 year hiatus! I'd really appreciate the input of PRR and all you other hollow-state dudes to as to how I can improve this design (make it work right). I'd also like to validate that I'm generally on the right track as well. No offense will be taken, as the component values are shots in the dark and my tube design chops are extremely rusty.
I'm working on a circuit modelled on the Leslie 122 amp to essentially be a unity gain device to insert beween the output of a Hammond X-5 organ and a Leslie 770 speaker. The idea is to add the distortion character of the 122 amp to an otherwise too-clean solid state signal chain.
I tried a simple single-ended transformerless 12AX7 design and ended up with more of a crackling farting sound than anything else. I got basically the same tone from the real circuit as did LTSpice--disappointing, but a pleasant surprise that LTSpice predicted it so well.
As I understand, the Leslie 122 amp gets its distortion characteristics from the combination of balanced 12AX7 amp feeding into a 6550 push pull amp. This is what I've come up with so far, grafting the 122 input stage onto a 12BH7A PP preamp output stage I found somewhere else.
Version 1 schematic here
The LTSpice model that produced the schematic above actually does pass a signal to the output -- one heck of a huge signal--definitely not unity gain, however, I'm sure the transformer model isn't right. :?: What is a decent, but affordable output transformer make and model for a design like this and how would one model such a transformer in Spice before I blow up a real one? (safety goggles on!)
FWIW, here's the LTSpice file for the above too.
Thanks!
--Bob
I'm just getting back into tube work after a 35 year hiatus! I'd really appreciate the input of PRR and all you other hollow-state dudes to as to how I can improve this design (make it work right). I'd also like to validate that I'm generally on the right track as well. No offense will be taken, as the component values are shots in the dark and my tube design chops are extremely rusty.
I'm working on a circuit modelled on the Leslie 122 amp to essentially be a unity gain device to insert beween the output of a Hammond X-5 organ and a Leslie 770 speaker. The idea is to add the distortion character of the 122 amp to an otherwise too-clean solid state signal chain.
I tried a simple single-ended transformerless 12AX7 design and ended up with more of a crackling farting sound than anything else. I got basically the same tone from the real circuit as did LTSpice--disappointing, but a pleasant surprise that LTSpice predicted it so well.
As I understand, the Leslie 122 amp gets its distortion characteristics from the combination of balanced 12AX7 amp feeding into a 6550 push pull amp. This is what I've come up with so far, grafting the 122 input stage onto a 12BH7A PP preamp output stage I found somewhere else.
Version 1 schematic here
The LTSpice model that produced the schematic above actually does pass a signal to the output -- one heck of a huge signal--definitely not unity gain, however, I'm sure the transformer model isn't right. :?: What is a decent, but affordable output transformer make and model for a design like this and how would one model such a transformer in Spice before I blow up a real one? (safety goggles on!)
FWIW, here's the LTSpice file for the above too.
Thanks!
--Bob