Swap 12au7 for 6N16b in RCA amp.

[Jaap]

I would like to build this RCA amp from tube manual RC-19. But I have not enough holes in my chassis. So I would like the to change the front tube to the subminiature 6N16b. Any suggestions for the resistor values to use in that case. CCS on the anode ? Or should I convert to a LTP with a ccs under it ?

 

[Lingwendil]

These have a max plate voltage of ~200 volts, so you would want to reduce the supply voltage to them to maybe ~220-250 or so.

100 volts at the plate, 6mA, and -2 volts grid is a good spot to run these. I would probably use it as concertina, 330r cathode resistor and plate resistor tuned to whatever value drops the supply voltage to 100 volts or so, half that value each for the anode and cathode on the concertina half to start.

 

[MagicBus]

Omit first tube and convert driver to LTP? Gain will be reduced but how much?


Edit: But then, how is feedback going to work?

 

[PRR]

These have a max plate voltage of ~200 volts, so you would want to reduce the supply voltage...

From numbers on plan: first section runs at 93V 0.8mA, second stage at 101V 2.4mA.

This is spot-on your voltage recommendation. The lower current is fine for the high impedance it drives.

 

[Lingwendil]

At a second look it looks like the 6N16B can take 300 volts if cut-off, so It should be just fine as is, I was more worried about warm-up time when it hasn't began to draw much current, but I bet it wouldn't hurt anything, these are tough little tubes

I really like these tubes, very linear and rugged. Probably the closest to a easily acquired submini 6SN7 (functionally) that you're likely to come across. I've used them for a handful of preamp duties and they work very well at a 185~ volt supply for small signal stuff. ~5k plate resistance, so something like ~12-15k plate resistor.

This is also a fine tube for use in a mu follower (or even morgan jones style "beta follower") and will be very nice paired with a mosfet follower to drive cables, larger loads, etc.

 

[6vheater]

Just be aware the submin Russian valves are very sensitive to hum.
You can also use raytheon 6111, it's almost the same.

 

[Jaap]

With some delay

I build this design with the Russian 6N16B sub-miniature tube. I used a mosfet regulator on the 6N16B. 6AU6 and 6V6 are fed via a mosfet ripple filter.
I must say that this amp sounds incredibly good !