Stereo class A 6+6W - 2x 6L6G 1 x 6N2P

[pilovis]

Schematic:



Line transformer output = 250 Vac 0.3A - 6.3 Vac 3A
Diode bridge = 4 x 1N4007
Filter Cap = 2 x 100 uF 385 V
Plate voltage of 6L6G = 290 Vcc (plate <> cathode)
Grid #2 voltage of 6L6G = 240 Vcc (grid2 <> cathode)
Bias current of 6L6G = 44 mA (17.2 V @ 390 ohm 2W self bias resistor)
Audio output transformers = 3Kohm/8ohm, Grid #2 connection @ 43% of primary winding (ultralinear).

note:
6N2P =6AX7 = ECC41 = 6h2n
6N2P, 6N2PEV (6H2n, 6H2n-EB)

You can try out 6N1P = ECC88 instead of 6N2P (with less gain)
6N1P, 6N1PVI, 6N1PEV (6H1n, 6H1nBN, 6H1nEB)

6L6 = 6L6G = 6L6GT
http://hvid.it/datasheets/6L6%20RCA.pdf



Youtube video:

Stereo Hi-Fi Tube amplifier 6L6G - YouTube

[costis_n]

Nice and simple. I can even call it too simple, I see no gridstopper resistors.

[pilovis]

Simple doesn't mean bad or incomplete .
Less components you use, less trouble you'll get.

There is no need for gridstoppers in this particular circuit, but you can use 1 Kohm resistors for that.

[TheGimp]

If you can be sure the source does not place a DC offset on the inputs you could even remove the input caps.

[kevinkr]

Never use them myself, haven't lost a tube or amp yet.. (40 + yrs)

[pilovis]

Originally Posted by kevinkr

Never use them myself, haven't lost a tube or amp yet.. (40 + yrs)

Never used what ?
Gridstoppers or input caps?

[TheGimp]

Input Caps. They block DC from upsetting the bias on a stage. It wont destroy your input stage as it is current limited by the anode resistor.

An example of a stage that could result in anode over-dissipation would be a choke loaded input stage. If a DC bias shift occurred, the DC resistance of the choke might not be enough to limit the anode current. This could result in destruction of the tube due to excessive anode dissipation.

Grid-stop resistors help prevent pickup of RFI from radio stations, TV, etc but this is not a potential damaging source for the tube or circuit. Only causes distortion.

[pilovis]

What about a short circuit on the driver between anode and grid?
It could inject High Voltage on the preamplifier output stage, I suppose.

[kevinkr]

What the Gimp says as I was corroborating his comment..

(No input caps, but I do use grid stoppers religiously, perhaps too religiously in some instances.)

[kevinkr]

Originally Posted by pilovis

What about a short circuit on the driver between anode and grid?
It could inject High Voltage on the preamplifier output stage, I suppose.

The source impedance is usually quite high in the event of a grid to plate short except in the case of IT or choke coupling where some serious mischief could occur. I've never seen a grid to plate short in any small signal triode or pentode to date - this does not mean it can't happen. The transformer coupled output circuitry in my line stage cannot be damaged by quite large voltages as long as the current is limited (it is) - if you are using solid state gear I would recommend fitting a higher voltage output cap - this will take care of the issue without requiring an additional part in the signal path.