Home Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Tube DIY Asylum ]
[ Alert Moderator ]

RE: clairty on a couple of issues

Good post. Thanks!

I realize that if everything else in an amp is designed
to be able to support a FBK scheme, then the total result can
be both clean and coherent.

McIntosh designed the MI-200 Industrial gold mining shaker-table
amp. (For shaking out gold dust in mining operations by driving
a shaker table with a transducer, driven by the MI-200, that
driven by an audio signal generator.

The amp, which was rated at 200W continuous, but could easily
put out 450 watts, sported a P/P pair of 8005 directly-heated
triodes. The B+ supply was 1000 volts, the rectifiers were 4 5U4GB
in a full-wave bridge. There was another power supply, using (2)
5Y3's in a full-wave Center-Tap arrangement. Each monoblock had 4
separate chassis. One was a meter panel.

The output triode pair was driven by a stage similar to (2) Kt-88s.
That was driven by the usual "MAC" lineup, using things like 12BH7,
12AU7, 12AX7, etc. I usually removed one of these stages.

If modded right this was a great high-fidelity amp. It had 4
different input windings on the primary side of the output
transformer, each connected to a various amplifier stage.

This amp is mentioned because negative feedbacks generated were
brought back into phase/and time alignment by building the output
transformer primary with different time-delays and phase
relationships designed to compensate for, and make coherent--
signals that were time delayed from one stage's FBK compared
to the timing of another stage. All was summed-up in the output
trans with its time/phase-compensated windings.

This accomplishes what you are talking about-- making a FBK
scheme actually work musically.

This amplifier, once cleaned up and prepped, sounds EXACTLY like
one of my triode SE amps. EXACTLY. These old MAC's were built
BEFORE all the "MAC" tube gear that people collect, and are vastly
superior to all of them. This could be called
"multi-stage unity coupling"-- if you please.

This is what it takes to make a P/P Neg. FBK amp actually work
musically. And it was designed for Mining Gold.

So, I agree with you. But we don't need any of that today.

Just run a tube where it operates at the right temperature,
uses no feedback, and just listen to it.

If the power supply, the build and the parts are good enough,
it's not going to have any competition musically.

-Dennis-



This post is made possible by the generous support of people like you and our sponsors:
  Schiit Audio  

Follow Ups Full Thread
Follow Ups
FAQ

Post a Message!

 Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Subject:
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]