Dinky little 2-valve Chinese pre-amp

[Joe]

I've just had my dinner and now I feel sick.

- Joe

[AlanBeckett]

You can't have set the Mood Lights properly.

Alan

[pwdrive]

Interesting stuff, still not sure what it's all about, presumably no EQ and no input sensitivity specs, just a headphone amp maybe but in conjunction with what...20 mw output but into what impedance...
Needs a distortion test set on it to get full specs.

Lawrence.

[Nick]

Interesting stuff, still not sure what it's all about, presumably no EQ and no input sensitivity specs, just a headphone amp maybe but in conjunction with what...20 mw output but into what impedance...
Needs a distortion test set on it to get full specs.

Anyone want to lend me one? I'll put it through a Tektronix AA501 and an HP 8903B...

[pwdrive]

Blimey...my limit was the old Ferro RTS1/2.

Lawrence.

[Joe]

Are these three-legged fuses I see before me?

   

- Joe

[Mark Hennessy]

Yes, presumably the MOS-FET and LM317 that we see on the schematic Nick posted earlier. As if the design wasn't idiotic enough already...

If we're going to talk gear, I can offer a Prism Audio D-Scope 2, or possible an AP if I'm willing to travel. Frankly, this little POS isn't worth the effort - I can't believe it's generated this number of posts, and I can't believe I'm still here contributing. I feel dirty.

[Joe]

My mis-understanding again (so nothing new there!). I thought that the one Nick posted was to illustrate use of a 12V HT whereas the one under discussion was all-valve, and therefore as much use as a chocolate tea-pot. If it's got some sort of output stage it would at least have a hope of operating headphones. I'm also so used to LM317Ts that I failed to recognise one of the LZ version.

It's odd as there are others on sale described as hybrids.

I'm NEARLY tempted to by one to see just what is what.

- Joe

[pwdrive]

What's needed is a circuit description.

Lawrence.

[pwdrive]

Here's more of a description.

http://diyaudioprojects.com/Solid/12AU7-...7-Headamp/

Lawrence.