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Old 26th April 2002, 06:36 PM   #51
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Default current soundcards with S/PDIF input?

I am a little wary of anything that sits inside a computer and is powered by it. What are current soundcards that have a S/PDIF input that will accept >20 bits, preferably at 96 or 192 kHz?

TI has a nice 24 bit ADC. With a decent oscillator and S/PDIF transmitter (or even I2S directly), it would make a very good analyzer.

Eric
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Old 27th April 2002, 01:58 AM   #52
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Thumbs up Jim Williams oscillator

Wow, I had forgotten all about the Williams version of the HP200 (wien using a lamp). So I quickly built one myself just to see. Yup - 0.01% distortion (as far down as my HP 333A goes) right off the bat. No extra filtering, just a one opamp oscillator.

I used a common 5W nightlight bulb we had on hand. They're quite easy to solder to. See schematic below for a 1kHz frequency. Adapt as you need, but this is one quick and easy project.

Now 0.01% may not be low enough for some of you high-feedback fans, but for my zero-feedback tube amplifiers, it's adequate. I measured my new "Cornet" phono preamp with this oscillator (padded down to 5mV) and got a total 1kHz distortion level of 0.02%. Not bad!
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Old 27th April 2002, 02:29 AM   #53
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Thumbs up LDO

I built one with a AD797 and 5 series connected bulbs for a 60Hz amplifier transformer power source. Low distortion at 60Hz even.
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Old 1st May 2002, 11:35 PM   #54
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Default PC polling rate?

One could actually read I2S or any other serial audio format into a PC provided the PC is fast enough to detect changes on the serial clock and the read the data line.

The last time I tried I/O port programming, I could get about 300 kHz on the parallel port and it seemed to be pretty independent of the speed of the computer used, but that was in the times of 75 MHz pentiums and 133 MHz 486s. Anybody know the polling rate of a modern GHz PC running Windoze98 or better and using Delphi?

Eric
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Old 20th October 2002, 09:51 PM   #55
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Lightbulb Enhanced S Blaster

I have in project to build a bridged tee filter, and to insert it at the input of a standard S Blaster PC card. Correctly designed and constructed, bridged tee can attenuate the fundamental by 60 dB.(Some amplification will be necessary between the filter and the SB card, depending of the level of the signal.)

S Blaster 128 can give correct analysis on a 60 dB range (or more) So, I expect possibilty of measuring distortion in the range -60 to -120 dB (or more), which is exactly that I need to measure audio amplifiers or components... cheap and effective !

Thank you for your comments/advices...

Regards, Pierre Lacombe.
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Old 21st October 2002, 03:12 PM   #56
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Anyone try Praxis? http://www.libinst.com/
I use LAUD (no longer available) to get distortion <.01% which is not great but it is easy to use.
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Old 22nd October 2002, 04:58 PM   #57
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Default FFT and Dist.Analyzer

Hi,

One idea I saw when browsing the internet run the signal to a ordinary THD analyzer wich attenuates the fundamental to -60dB feed the output to a cheap 16 bit soundcard with a freeware fft program do the math and calculate the residual I think one can get really low thd figure out of this I don't remember how but it should work.
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Old 23rd October 2002, 01:19 PM   #58
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Default Miscellaneous Thoughts

On the Cordell Analyzer: I have the 3 part article and the PC boards, but this is a vary complex project and the selector switches are made out of unobtainium (at least at resonable prices ).

On the Jim Williams Oscillator: The best version uses a CdS photocell, the Vactec VTL5C10 or Clarex CLM410 both made out of unobtainium.

On the Charles Hansen Oscillator: The 5/1998 issue of Audio Electronics magazine has his article on a buildable version of the Williams oscillator.

On SpectraLab software: You can downlord a 30 day trial of the complete package. When the time expires get a new computer and to it again.
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Old 23rd October 2002, 01:40 PM   #59
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Default Miscellaneous Thoughts

Right on brother Can I get a witness?

"On the Jim Williams Oscillator: The best version uses a CdS photocell, the Vactec VTL5C10 or Clarex CLM410 both made out of unobtainium."

You can make this device from an LED and CdS photocell from Radio Shack I think but will have to adjust the circuit for the different transfer function. It looks very doable and has loads of cooliosty potential.

I use the light bulb feedback Wein bridge for my clean AC power and it is very clean. More on the subject of oscillators later and
freeware FFt at:

Fred
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Old 23rd October 2002, 01:48 PM   #60
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On the Cordell analyser:
could you please post the schematics ?
I'm curious about it !
Thank you !
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