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
