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A Tube amp without coupling capacitors? Possible?
A Tube amp without coupling capacitors? Possible?
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Old Today, 02:49 PM   #211
Keit is offline Keit  Australia
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Originally Posted by lechuck View Post
This is an example of a Norton shifter:
Click the image to open in full size.
The circuit as shown is likely to exhibit poor treble response, and if overall neg feedback is used, is very likely to oscillate.

A few picofarad (if next tube is a pentode or tetrode) to 20pF or so (if next tube is a triode) across the level shifting resistor will compensate, so the fix is quite simple

Originally Posted by lechuck View Post
Another option would be to use sweep tubes (EL509..) and drive them on the screen grid (G2)
The screen grid used as a control grid is insensitive and usually not as linear as the true control grid. It draws power too, complicating the design of the previous stage.

Originally Posted by lechuck View Post
A Norton shifter is not a single device and can be built with components that where already available in the late 50's, early 60's.
All you need for the CCS is a small pentode (eg 6AU6 or 6BA6, pentode half of a triode pentode) and three resistors. Nothing could be simpler - except using a neon tube as coupling device (but neons are noisy, have a short life, and can exhibit small voltage jumps in old NOS devices and in neons intended as indicating lamps.)
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Old Today, 03:07 PM   #212
jhstewart9 is offline jhstewart9  Canada
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Location: near Toronto
Default DC Amplifiers

The DC Amplifiers I built were most all in industrial & scientific applications, no one had to listen to them.Many were in the regulated Power Supplies for both constant voltage & constant current apps.. When good silicon rectifiers became available they were the obvious choice for the rectifier.

The largest was a monster 4.5 KV, One Amp CV thing. The iron was all Hammond, built to order for us. One of the features of the whole thing for which I'm thankful to Prof Anderson for was an SYA setup. Save Your ***, the source relay contacts welded together on contact, they did not release on shut down. There was a very loud explosion as the SYA device operated.

By 1965 there were quite a few multi layer silicon devices on the market. But nothing that would shift something like 100V CC or more. All easy to do now, we are in an age of plenty.
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Old Today, 08:51 PM   #213
Wavebourn is offline Wavebourn  United States
Anatoliy Lisovskiy
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Location: Pleasant Hill, CA
A Tube amp without coupling capacitors? Possible?
Originally Posted by jjasniew View Post
From the suggested article; "Note; even if the measured performance appears flat, our ears are quite capable of distinguishing micro-effects that limit the potential musical beauty of an amplifier and that is, I assert, the point of this hobby - so long as we are having fun"
Right, and that micro-effects are dynamic, while measurements are static and averaged.
Single Ended Class-A-Holism is addictive!!!
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