Hi,
I was looking at all different kinds of tone controls and came up with the idea to put a Baxandall treble & bass circuit instead of the local feedback loop of a triode, in the global feedback of the poweramp.
This should replace the common presence and resonance controls but I am really not sure how the dimensions have to look like, especially if I'd take the feedback from the 8Ohm tap of the OT after a bootstrapped cathodyne PI..
There is pretty much impedance matching and scaling going on I guess so maybe someone here can give some input which values could work somehow?
Aiken has some calculations concerning the global feedback loop: http://www.aikenamps.com/index.php/desi ... e-feedback
Maybe the impedance matching is easier with a cathode follower between the recovery stage and the tone circuit?
Is there a chance to get this to work properly?
Thanks!
Global NFB Baxandall circuit?
Moderators: pompeiisneaks, Colossal
Global NFB Baxandall circuit?
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Re: Global NFB Baxandall circuit?
Based on my experience, it works way better if you equalize with a dedicated stage just before the PI.
Re: Global NFB Baxandall circuit?
Give it a go by all means but bear in mind that presence and resonance are boost controls, they progressively remove NFB in their respective bands.
To put a 'cut' function in there means a fair bit more (frequency selective) negative feedback.
As there's a transformer in the loop (with its own phase shifts), introducing more phase shift and NFB in the loop may reduce the system's margin of stability (less gain doesn't necessarily equate to more stability).
To put a 'cut' function in there means a fair bit more (frequency selective) negative feedback.
As there's a transformer in the loop (with its own phase shifts), introducing more phase shift and NFB in the loop may reduce the system's margin of stability (less gain doesn't necessarily equate to more stability).
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