Sowter TVC LF Oscillation?

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Ali Tait
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#16 Re: Sowter TVC LF Oscillation?

Post by Ali Tait »

Maybe they all drive Minis Mark..
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#17 Re: Sowter TVC LF Oscillation?

Post by Dave the bass »

Mini's.....pfffttttttt! :)
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#18 Re: Sowter TVC LF Oscillation?

Post by Dave the bass »

I think.... I may have entered a new era of measurement!

Oooo!
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#19 Re: Sowter TVC LF Oscillation?

Post by Mike H »

Flash sod. :D

Wot is it?
 
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#20 Re: Sowter TVC LF Oscillation?

Post by Dave the bass »

Thats a screen grab from AudioTester. I was using a USB soundcard interface I'd built from an EPE magazine a couple of years back. The top 2 traces are a frequency sweep and the same at attenuated level, the lower 2 are the response of a Hagerman iRIAA filter.

I dun learning, with our-Thomas's encouragement.
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#21 Re: Sowter TVC LF Oscillation?

Post by Mike H »

Had to look that up, wooo!

Bookmarked ~ a while back I was thinking about some sort of PC 'scope stuff.
 
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#22 Re: Sowter TVC LF Oscillation?

Post by Nick »

Using that front end and a 96/24 m-audio card, you can get down to this sort of floor. Thats on the 200mv range, and 0dB is 100mv RMS. So you can see signals down to about 200nV

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#23 Re: Sowter TVC LF Oscillation?

Post by Dave the bass »

Oh, your noise floor looks cleaner than mine Nick, is that using an un-tweaked ATEST and M-Audio Transit?
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#24 Re: Sowter TVC LF Oscillation?

Post by Nick »

Thats a m-audio PCI card, and a atest with copper shielding and andrews tweek to the limiting resistors. It also involves keeping the a-test away from any other source of hum.
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#25 Re: Sowter TVC LF Oscillation?

Post by Dave the bass »

Ta for the reply, I'm still very much getting grips with the software (which times out after 10 mins of measuring!), I've purchased the license but haven't received the key yet.

Wow, your noise floor trumps mine. This is a 2D FFT with the default 'Rife Vince 3' window selected. Bog standard unshielded un tweaked ATEST + M-Audio USB Transit. EDIT. 200mV range selected.
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#26 Re: Sowter TVC LF Oscillation?

Post by Dave the bass »

Yey, the licence Key has come, I can measure for longer than 10 mns now at a time. So to celebrate I think I've successfully looked at the noise floor of the PCM2902 soundcard interface.
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#27 Re: Sowter TVC LF Oscillation?

Post by Dave the bass »

Oooo! While I'm on a roll :) ... I do believe I've just managed to measure/look at the distortion spectra of a little chip amp running into a dummy load. I think I can see the harmonics too.
Chipampdistortionspectrum.jpg
and here's a freq sweep of the same...
Chipampsweep.jpg
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#28 Re: Sowter TVC LF Oscillation?

Post by thomas »

Looks like you've got the hang of it! Are the soundcard/ audiotester behaving themselves?
I don't fancy that chip amp very much…..I'll have a go measuring mine later
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#29 Re: Sowter TVC LF Oscillation?

Post by Dave the bass »

Yeah, its coolio ta Thomas! The Transit USB seems much better behaved after you threatened it with the curse of the spangly pink mouse (and I stopped setting the Audio in/out parameters to a setting that wasn't available, ahem)!

I just re-read a little on the Pete Millett site and 'calibrated' the 'Zero' and 'FS adj' using my sig gen flat out at 2.23V AC @ 50Hz. I'll compare it to a Heater TX another day just to check at say 12V or so too.

A good day.

How's the Plumstead Peril? :)
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#30 Re: Sowter TVC LF Oscillation?

Post by thomas »

Dave the bass wrote:Yeah, its coolio ta Thomas! The Transit USB seems much better behaved after you threatened it with the curse of the spangly pink mouse
That usually seems to work….

'Plumstead peril' aka the Matchless G12, my new mid life crisis toy, apart from displaying a worrying tendency to want to bump into things, is doing ok for something of such advanced years, and doesn't seem to leak very much either….

….wait for it…..

:roll:
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