DC restorer

[kingfisher]

Can someone explain the DC restorer zener circuit and how to apply it? I have the same 'Base' model vintage amplifier used in Bob Carver's NEW design 'http://www.bobcarver.com/vta20s.asp' in the vintage amp he used a DC restorer zener circuit to stablize the voltage drop from tubes driven close to cut-off at high output demands. "This circuit 'zener is connected to the cathode bias resisterand fed back to the grids such that thegrid bias is held at a constant voltage (Carvers used 12volts) thereby restoringthe lost DC component of thedrive signal." His words.

kingfisher

 

[LinuksGuru]

It should be on another thread, sorry.

 

[Yvesm]

No possible answer without seeing a schemo . . .

 

[DavesNotHere]

its a simple auto bias circuit. so the amp doesn't run in class B

on another note if someone expands on the circuit say with a ccs the auto bias circuit would have enough gain in essence to trnsform the final stage into a local AGC keyed VCA and compress the signal.

 

[kingfisher]

DC Restorer

Thanks DavesNotHere The simplest answer is the best starting point!

 

[LinuksGuru]

Not exactly DC restorer, which is discussed in details in this thread
http://www.diyaudio.com/forums/tubes-valves/239652-putting-stock-carver.html
but automatic bias control developed back in 1947 and published in Audio Engineering - "High Quality Audio Amplifier with Automatic Bias Control".

Article in PDF format attached.