re design of a SE tube amplifier

[Original Burnedfingers]

I ran across this and would like your comments. I would like to do something like this except to use a 6SN7 as the second tube and some of SY's 6BG6's as output tubes.

If there were roughly 150 volts on the grid of the 2nd half of the 6SL7 and 290 on the plate what would be across the 47K cathode resistor?

How could this amp be changed to provide the most power and best sound on a basement level price?

[7N7]

To answer your first question I would estimate 152V or so.

Why not build a 317 regulator to feed g2? This is cheap to do and since the g2 voltage is so critical, should make a big improvement.

7N7

[Original Burnedfingers]

7N7

Thanks for the reply

I can't find a circuit for the LM317 regulator so I could use it in a high voltage application. I did however find a circuit that uses a 1XCY 10M45S Would I be correct in assuming that this would work as good also? How about (2) VR150 tubes? How about a CCS like SY talked about before?

Given the 330 volt input to the divider I am assuming that it would output 300volts to G2. Current draw being about 1mA?

Could I just plug in a 6SN7 in place of the second 6SL7 tube?

[7N7]

There is a thorough description of building HV 317 regulators in Morgan Jones's Valve Amplifiers ; based on this I have built many successful regulators. You might find some data on the sites of some of the manufacturers such as Fairchild or National Semiconductor.

If you wanted to change over to 6SN7 then you would need to run more current through the valve - at present you are running about 3mA; it is said that 8mA is ideal for lowest distortion. Again see Jones.

There are many cleverer peple hereabouts especially with SE amplifiers which I have never built; I should wait a bit!!

Best of luck

7N7

[Original Burnedfingers]

Thank You 7N7

There is a thorough description of building HV 317 regulators in Morgan Jones's Valve Amplifiers ; based on this I have built many successful regulators. You might find some data on the sites of some of the manufacturers such as Fairchild or National Semiconductor.

Found it I think I did page 239 Second edition of Valve Amplifiers by Morgan Jones.

[7N7]

Originally posted by burnedfingers
Thank You 7N7



Found it I think I did page 239 Second edition of Valve Amplifiers by Morgan Jones.

The explanation is better in the third edition - especially useful for dummies like me!

7N7

[Original Burnedfingers]

The explanation is better in the third edition - especially useful for dummies like me!

It would appear that I am the only dummy here.

Don't have the third edition yet.

[7N7]

Nonsense!

Positive thinking always!

7N7

[Original Burnedfingers]

If I changed the 2nd 6SL7's cathode resistor to 22K roughly couldn't I put in a 6SN7 then?

Anybody???

[7N7]

Try 33k first and measure. You can then see if the voltage is satisfactory and of course calculate the current using Ohm's law.

If incorrect then go to 22k.

Sorry but I'm a bit out of practice.

7N7