~QUESTIONS ABOUT "LOCAL"-NEGATIVE-FEEDBACK OUTPUT SECTIONS THAT ARE BASED ON A TERTIARY-WINDING OUTPUT TRANSFORMER~
Posted: Tue Jul 23, 2019 12:36 am
~hello all( especially Wayne )...
I've tried to do my due-diligence-web research on this subject, to make the muddy waters of this topology a little more clear & have not had much luck unfortunately. What little i could scrounge( & it's really not much ), aside from being vague & devoid of systematic absolutes on the process...most, if not all, was addressed to the context of guitar & bass amps/power amps for driving live, large-scale installations. I'm interested in getting a handle on the concept, as it applies to high-end professional preamps/eq's/comp-lim's etc. In other words, the most refined, elegant & broad-audio-spectrum accommodating iterations of such, that i can learn to implement. At this point, i've zeroed-in on one specific version of local-negative-feedback that, i want to understand & incorporate into some current builds.. which, is the kind derived by utilising custom output transformers, with a purpose-built tertiary(feedback) winding designed for that function. I know that those are normally associated with tube-output stages..but, the only info i could *somewhat* derive aside from that is, that it may be in a cathode-follower type configuration? If that is correct, is there a *best-of-the-best* version, which lends itself particularly well to high-end audio production gear? Is it ONLY something that can be implemented through a tube-output-stage configuration or, can it be utilised in solid-state circuit designs as well? I have a specific transformer set that was designed for this purpose, in it's original application...i have all of the transformer's parameter-data & specifications, as well as, a step-by-step method of how to utilise it in a *normal*, non-feedback based orientation..which, i'm sure will work quite well in it's own right, to be sure but...because of the build quality & top-shelf nature of the transformer itself & corresponding high-end mastering processor that, it was produced in relatively small-batch-orders to complete..i can't therefore help but, to wonder if this is a situation that warrants using it in it's intended configuration( i.e., will it make a significant difference over using it without the negative-feedback tertiary winding? )
I will post the relevant transformer data below & it bears mentioning that, these transformers were designed by R. Neve, for use in the output section of the mastering system he designed in collaboration with Legendary Audio called, the "Masterpiece". They were unused shelf-stock that, never found their way into a build, due to production ceasing on account of parts unavailability. They apparently are modern renditions in design & spec, of the output transformers wound for the "Air MontSerrat" studio console...beefy as hell toroids. Figured that it'd be worth looking into, especially considering that i will be using these in a mastering processor capacity as well. So, on that note, any information that anyone can provide on the subject would be IMMENSELY appreciated! Even if it's just pointing me in the proper research direction, ANYTHING WOULD BE GREAT!!! Thanks either way for enduring my rant ~
{{{ SPECS AS FOLLOW: }}}
Transformer Specs:
RED = Signal In
BROWN = Input Winding (Grounded in circuit)
Input Impedance Measurement = 7.4 Ohms
ORANGE = Signal Out +
YELLOW = Signal Out -
Output Impedance Measurement = 11.2 Ohms
BLUE = Tertiary (Feedback) Winding Input
GREEN = Tertiary Winding (Grounded in circuit)
Tertiary Impedance Measurement = 9.0 Ohms
BLACK (x2) = Screen/Case most likely. These should always be connected
to analog ground on the circuit board. (if there is a circuit board)
Configuration for passive use:
Connect the wires as below for +2.5 dB of gain and tone:
Blue remains open with no connection.
Red + Green = tie together, use for INPUT
Brown + Blue + Black (x2) = tie all to GROUND
Yellow = OUTPUT -
Orange = OUTPUT +
I've tried to do my due-diligence-web research on this subject, to make the muddy waters of this topology a little more clear & have not had much luck unfortunately. What little i could scrounge( & it's really not much ), aside from being vague & devoid of systematic absolutes on the process...most, if not all, was addressed to the context of guitar & bass amps/power amps for driving live, large-scale installations. I'm interested in getting a handle on the concept, as it applies to high-end professional preamps/eq's/comp-lim's etc. In other words, the most refined, elegant & broad-audio-spectrum accommodating iterations of such, that i can learn to implement. At this point, i've zeroed-in on one specific version of local-negative-feedback that, i want to understand & incorporate into some current builds.. which, is the kind derived by utilising custom output transformers, with a purpose-built tertiary(feedback) winding designed for that function. I know that those are normally associated with tube-output stages..but, the only info i could *somewhat* derive aside from that is, that it may be in a cathode-follower type configuration? If that is correct, is there a *best-of-the-best* version, which lends itself particularly well to high-end audio production gear? Is it ONLY something that can be implemented through a tube-output-stage configuration or, can it be utilised in solid-state circuit designs as well? I have a specific transformer set that was designed for this purpose, in it's original application...i have all of the transformer's parameter-data & specifications, as well as, a step-by-step method of how to utilise it in a *normal*, non-feedback based orientation..which, i'm sure will work quite well in it's own right, to be sure but...because of the build quality & top-shelf nature of the transformer itself & corresponding high-end mastering processor that, it was produced in relatively small-batch-orders to complete..i can't therefore help but, to wonder if this is a situation that warrants using it in it's intended configuration( i.e., will it make a significant difference over using it without the negative-feedback tertiary winding? )
I will post the relevant transformer data below & it bears mentioning that, these transformers were designed by R. Neve, for use in the output section of the mastering system he designed in collaboration with Legendary Audio called, the "Masterpiece". They were unused shelf-stock that, never found their way into a build, due to production ceasing on account of parts unavailability. They apparently are modern renditions in design & spec, of the output transformers wound for the "Air MontSerrat" studio console...beefy as hell toroids. Figured that it'd be worth looking into, especially considering that i will be using these in a mastering processor capacity as well. So, on that note, any information that anyone can provide on the subject would be IMMENSELY appreciated! Even if it's just pointing me in the proper research direction, ANYTHING WOULD BE GREAT!!! Thanks either way for enduring my rant ~
{{{ SPECS AS FOLLOW: }}}
Transformer Specs:
RED = Signal In
BROWN = Input Winding (Grounded in circuit)
Input Impedance Measurement = 7.4 Ohms
ORANGE = Signal Out +
YELLOW = Signal Out -
Output Impedance Measurement = 11.2 Ohms
BLUE = Tertiary (Feedback) Winding Input
GREEN = Tertiary Winding (Grounded in circuit)
Tertiary Impedance Measurement = 9.0 Ohms
BLACK (x2) = Screen/Case most likely. These should always be connected
to analog ground on the circuit board. (if there is a circuit board)
Configuration for passive use:
Connect the wires as below for +2.5 dB of gain and tone:
Blue remains open with no connection.
Red + Green = tie together, use for INPUT
Brown + Blue + Black (x2) = tie all to GROUND
Yellow = OUTPUT -
Orange = OUTPUT +