OR120 microphonic v1

[yossarian83]

Hi,
I recently was tinkering with my amp and noticed that no matter what tube is in V1, it always fails the "Tap Test"
Is this typical?

[Gladmarr]

In the high-gain first stage of all tube amps, you'll always hear the tap. The tube is mechanically microphonic, but only becomes a problem when it "rings" after being tapped. That's what people usually mean by a tube going microphonic - when the tube gives you ringing or mechanical feedback that doesn't dampen out quickly.

[yossarian83]

That's what I figured, thanks Gladmarr.

[a.hun]

All other things being equal the first preamp valve in line will always seem more 'microphonic'. This is simply because any noise there (and all valves are to some extent microphonic!) will then be amplified by all subsequent gain stages.

The OR120 is a relatively low gain amp though, so I'd not expect real problems unless a valve is pretty bad. Basically the way I look at it, microphonics are only ever a problem when they actually become a problem!


Andy.

[drbob1]

Which is why you'll find that a short or medium plate tube will work much better in V1 than a long plate-even if it's not technically microphonic, the increased gain after the tube will amplify any ringing induced in the plates and it'll be functionally microphonic. Smaller plates, less shaking…

[nlimbaugh]

yeah, the truly microphonic tube presents itself when you turn on the amp and start playing.... things just aren't acceptable period.