6N11 tube work at 24V power supply?

[siliconray]

I got an interesting headphone amplifier board today. There's a 6N11 tube on it, other silicons are 2xIRF630, 2xLM317 and 2 TO-92 transistor. The sound is fairly good with my HD600. Most interesting of all it is powered by single DC 24V! How can 6N11 work at such low voltage?

Google a bit, found that most 6N11 circuit need much higher voltage such as 150V or higher.

This is the headphone amp board

[Bone]

You will probably find that there is a voltage multiplier/inverter on the PCB to get this higher voltage.

[VictoriaGuy]

Is the circuit something like this?

[siliconray]

There's no voltage multipler on board. The circuit should be like the one VictoriaGuy posted but there's one more transistor to drive the gate.
See the following photo, the TO-220 on the left is IRF630, right is LM317. There's a small TO-92 transistor near the IRF630.

[siliconray]

How about the sound of the 12AU7 headphone amp?
I'm thinking of build a hybrid amp with 12AU7+TDA8920 class D, what's your thought?

[Tony]

i think you will be better off with 6GM8 tubes as it is a low voltage tube...

[ericj]

Most all tubes will sort of work at low B+ voltage.

The distortion will be very high, but most of the distortion will be even-order distortion that most people perceive as sounding nice. And there is nothing wrong with that.

The (c) Rogers Gomez schematic looks like yet another variation on an amp designed a few years ago by a korean who went by the handle "sijosae" on the forums. He called this basic sort of design the Multi-Hybrid Headphone Amp or MHHA. He designed 6dj8 and 12au7 versions, with irf610 for output i think.

They were very popular back around 2004-2005. Many lookalikes have turned up on ebay.

Since the 6n11 is similar to a 6n1p which is similar to a 6dj8, i would assume that it's just another version.

There is nothing new under the sun, so i would not be surprised if it's been done before sijosae did it.

[VictoriaGuy]

Originally Posted by siliconray

How about the sound of the 12AU7 headphone amp?
I'm thinking of build a hybrid amp with 12AU7+TDA8920 class D, what's your thought?

Those little 'Bravo/G2-style' amps are fun (I've got one), but it's not a direction that holds much interest for me. I think the tube is a bit of a gimmick- same as in the 'tube preamp' guitar effects running tubes at low voltage.

I've assembled both SS (Panda) and tube (Crack) HP amps and they are both miles ahead of the little hybrid I have. (More $$ by factor of 4?, also.)

But give it a shot and let us know how it turns out!

EDIT: ericJ has given you the pointers you need.

[ericj]

Originally Posted by VictoriaGuy

Those little 'Bravo/G2-style' amps are fun (I've got one), but it's not a direction that holds much interest for me. I think the tube is a bit of a gimmick- same as in the 'tube preamp' guitar effects running tubes at low voltage.

Eh, whether or not a boatload of 2nd order harmonic distortion is a gimmick is a question of taste.

If you're going to run at low B+ there are space charge tubes, but 12au7 is cheaper than 12ae6a these days.

[Bigun]

Originally Posted by ericj

Most all tubes will sort of work at low B+ voltage.

Since the 6n11 is similar to a 6n1p which is similar to a 6dj8, i would assume that it's just another version.

.

The 6N1p is often touted as similar to the 6dj8, especially by ebay sellers. But it's not equivalent.

The 6dj8 is known to work well at low B+, but I doubt that the 6n1p works anywhere near as well.

A better choice, and a real equivalent to the 6dj8 is the 6n23p. Not sure if it's pin compatible with the 6n1p though.