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In Reply to: RE: I had a nice talk with Doc Hoyer. posted by Michael Samra on February 25, 2015 at 15:39:59
The output TX primary is working just like a split load phase inverter. which of course has a gain of ~2...
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Follow Ups:
There is no voltage gain when reference to ground,it is a swing from the cathodes.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
One way to look at the gain of the output stage is to reference everything to g1. The voltage gain at the cathode will be ~ +1 while the gain at the anode will be ~ -1. If meas betw A to K, gain will be approx +1-(-1)=+2.Bootstrapping has nothing directly to do with the unity coupled output stage. It's simply a means of generating a large AC voltage using a limited B+ voltage.
Edits: 02/25/15
Steve
It needed to be done tho because of the lack of voltage amplification in the output stage, or very little by comparison to a conventional output stage. One time I put in a pair of 6L6gcs in one of my Mc60z..It sounded very good but what happened was it sucked in the side of the glass and warped the inside of the tubes.
Now under most conditions a 6L6gc biases up like a 6550 as far as negative bias voltage and plate voltage goes..I had put 6L6gcs in the citation 2 and no such thing happened but I did reduce the current to about 50ma a tube.After seeing what I saw what the Mc60s did,I had no trouble believing doc when he said current amplifies thru the output stage of the unity coupled circuit..
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Edits: 02/25/15
...recall that the patent indicated use of an interstage transformer to drive the finals as did the production version 50W2. Bootstrapping was just a lower cost means of achieving the nec drive voltage compared to the high quality interstage transformer of the original concept.
Correct
The initial circuit used the innerstage as you said..Give doc a call when you get time..He loves to talk when he has time and he is winding things down so he has some time now.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
One of the things I will do to the next set of MC amps I get my hands on is eliminate that boot strapping. It is easily done with a CCS replacing the 12BH7's 12k plate loads. Then you still get the bootstrapping voltage headroom, but not the bootstrapping positive FB.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
...they're bootstraped too.
first things first...let's deal with the big fishes first...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Mike, do tell me what is happening at the plates please.
cheers,
Douglas
or, better yet, please look at why you think this stage is anything different than a split load phase inverter.
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I will check each G1 referenced to ground and then each plate referenced to ground.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
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