Schade Feedback In A Push Pull Differential Amplifier?

[Kay Pirinha]

Since a conventional cascode, consisting of two triodes, has an output impedance comparable to that of a pentode, I don't think that this MM arrangement is worse in here. Of course, plate (and screen) current is dominated by the bottom BJT.

Best regards!

 

[nigel pearson]

I liked the pilot story about a Blackbird over the North Sea that had an engine failure. Pilot radio'd in to some Norwegian airport for permission to land and they OK'd that, even though nothing was on the radar. Then this big long black thing lands on the runway and the pilot gets out with a space suit on. They thought the Aliens had landed and called security, so the pilot asked for a beer to cool things down. Too bad they were so expensive to run and got put out to pasture. Something else up there now.

The house I hope to buy is a bit out of the way so uses heating oil. I have been learning how these boilers work ( 1880's style selenium [ Siemens ] cell to shut down the fuel if no flame detected ) . Seems the boiler in this house uses an oil that is very much like jet fuel. I think it is called 28 second oil. Older types use 35 second much like diesel. The Blackbird used a special safer fuel which allowed the plane to leak a little which was the way it had to work.

Interesting the the Music Man amp has caused debate. I can see an arguement to use as much shunt feedback as possible.The transistor could be a PNP NPN compound pair ( 2 x 2 ) of very high current gain and also low distortion in that element. That might be the way to get a low output impedance to drive the transformer. Over Schade it has some advantages. If the current gain is very high a nice linear driver could be used.

 

[Kay Pirinha]

The house I hope to buy is a bit out of the way so uses heating oil. I have been learning how these boilers work ( 1880's style selenium [ Siemens ] cell to shut down the fuel if no flame detected ) . Seems the boiler in this house uses an oil that is very much like jet fuel. I think it is called 28 second oil. Older types use 35 second much like diesel. The Blackbird used a special safer fuel which allowed the plane to leak a little which was the way it had to work.

At least in Germany, there aren't too big differences between heater oil, jet kerosene and diesel fuel. Actually, the main component of all three is kerosene.

Interesting the the Music Man amp has caused debate. I can see an arguement to use as much shunt feedback as possible.The transistor could be a PNP NPN compound pair ( 2 x 2 ) of very high current gain and also low distortion in that element. That might be the way to get a low output impedance to drive the transformer. Over Schade it has some advantages. If the current gain is very high a nice linear driver could be used.

Right. Getting the relationship between signal input and plate current as linear as possible will garant for low distortion, as in the load impedance only signal AC current counts.

Best regards!

 

[nigel pearson]

My big guess was the transistor side could be very low in distortion so allowing the valve to be itself ( or our choice of that ). This design in the link has a very full investigation into a feedback pair plus cascode albeit all transistor. One reason to look at this is the biasing could be exactly as a single transistor. Linearity will be better as will current gain over the Music Man. We could have a ECC83 doing a bit better than usual driving it as we could have a more ideal anode load ( perhaps ). The idea is super performance from very low cost parts. I have used a complimentary pair as the so called VAS in a transistor amp. It gave me no trouble and was a dream to drive.

MJR7-Mk5 Mosfet Power Amplifier Design Notes