[akiroz]

 
Hi, I am designing a Hybird Headphone Amp with Triode input stage and BJT Output stage. I am experienced in designing for BJT's but completely new to valves, I learned about Anode followers and Cathode followers but don't really know how to put them together without a coupling capacitor. Is it possible to put a cathode follower after a anode follower without a capacitor in between? if so, How?

 

[wakibaki]

Here's a (DC coupled) grounded cathode followed by a White cathode follower:
 
http://gilmore2.chem.northwestern.edu/projects/cmoy5_prj.htm
 
and an optimised version using cheap, readily available Russian tubes:
 
http://gilmore2.chem.northwestern.edu/projects/showfile.php?file=bender_prj.htm
 
Of course these are all-tube amplifiers.
 
The problem with using a DC coupled BJT after a common cathode stage is that voltage output from the stage is likely to be high with most common tubes, conventionally employed.
 
There are, however, a number of tubes intended to be used at low voltages, and it is possible to use regular tubes at low supply voltages (google 'space charge'). Take a look at the Oatley K272A headphone amplifier which uses low-voltage JAN 6148 tubes.
 
http://secure.oatleyelectronics.com/files/K272A%20NOTES.pdf
 
If you want to understand (modern) tube design, you should really read Valve Amplifiers by Morgan Jones, It's not an expensive book.
 
Failing that you can download the (old but good) Radiotron Designers Handbook
 
http://www.paleoelectronics.com/the-radiotron-designers-handbook-4th-ed/
 
The link is to an online version, but you can find both the 3rd. and 4th. editions available as a single pdf by googling.
 
w

 

[nikongod]

 
Quote:

If you want to understand (modern) tube design, you should really read Valve Amplifiers by Morgan Jones, It's not an expensive book.
 

+1

 

[wakibaki]

Quote:

 
Hi, I am designing a Hybird Headphone Amp with Triode input stage and BJT Output stage.

 
 
An anode follower or common cathode stage can be fed directly (DC coupled) to a BJT emitter follower, but of course its output voltage will set the bias conditions for the BJT follower.
 
To keep the tube stage quiescent output voltage low the cathode may be connected to a negative supply.
 
Hybrid designs with MOSFETs are quite common, but I've never really tried to design a hybrid, either with MOSFETs or BJTs.
 
http://digilander.libero.it/essentialaudio/hybrid_circuit.htm
 
w