[linux-audio-dev] Re: Cheby amp code

[Lamar Owen]

On Tuesday 05 November 2002 17:57, Steve Harris wrote:
> On Tue, Nov 05, 2002 at 08:26:40 +0100, Tim Goetze wrote:
> > Steve Harris wrote:
> > >The bad news is that it means going inside someones amp with a probe, I
> > >would have a go myself, but I've allready killed my last amp, and my
> > >electronics skills are bad enough that I would probably fry myself ;)

> > looking at a fender tube amp schematic shows +140 V after the first
> > 12AY7 -- i don't have any equipment that would make this signal
> > digestable by a computer.

> Yeah, ggjjjzap. I dont have anything that can handle that either. How do
> those attenuating osciloscope probes work? Maybe you can build something
> equivalent in an audio lead, though I wouldnt be happy putting anything
> like that through a homemade attenuator into my desk.

I have one of these:
http://www.velleman.be/Product.asp?lan=1&id=338488 (Velleman PCS64i digital 
oscilliscope adapter for PC).  It's good to 600V, I think.  It attaches to 
your parallel port.  RadioShack carries them in the US.  They run about $300.  
As it also works as a transient recorder and spectrum analyzer (to 32MHz), it 
is a great buy.  Even though it is an 8-bit device, it is useful in showing 
what the signal looks like, as your eye can't distinguish the difference on a 
75dpi screen between 16 bit and 8 bit samples.

If you were close enough, I'd let you borrow my Tektronix 475 analog 
oscope.... With a 10x attenuator probe it's good for signal amplitudes of a 
couple hundred volts with a DC offset of 600V.

If I had the amp in question here, I would be happy to do the trace for you; I 
routinely work on hot tube gear. (I'm a broadcast engineer; broadcast 
transmitters that are tube output have 10kV or more floating around them.)
-- 
Lamar Owen
WGCR Internet Radio
1 Peter 4:11