Hi Paulwv,
Yes, currently I use an external +/-15V supply. My plan is to make a small daughter card with regulators that would be connected to the Murata pcb pads.
I've have also screened the plastic box and grounded the input range selector housing/shaft. The latter made a big improvement.
Hi,
I should clarify that the common mode switching noise did not directly influence measurement results (probably dependent on the DUT). I discovered the presence of common mode switching noise when probing a circuit with a scope. An erratic scope sync revealed the issue.
The additional screening did however help lowering the noise floor within the audio band.
I should clarify that the common mode switching noise did not directly influence measurement results (probably dependent on the DUT). I discovered the presence of common mode switching noise when probing a circuit with a scope. An erratic scope sync revealed the issue.
The additional screening did however help lowering the noise floor within the audio band.
Hi all,
I've been using the interface for quite some time with great results. Occasionally I screwed it up, just by running it with grounded input (i.e. by pressing the front GND button) and by measuring a GND connected to earth. Evidently have a ground loop in my workshop between the DUT and the also earthed PC.
The way I realised this after some initial measurement is that the THD goes to the roof as driven signal back to the SC is heavily clipped. The DRV 134 (U7) gets really hot as clear signal that is damaged. By replacing it, all goes back to normal and obviously y carefully deselect the GND button back to float to avoid same issue twice!
I was about to buy some spare DRV134 when reading this thread found that the THAT 1646P08-U was used by some other people. It is not just cheaper, but also has better THD and lower noise level. Any experience or suggestions?
Also, is there any way of adding a protection to the DRV134 when in a ground loop to avoid burning it by my careless operation?
PS: I've bought a sheet of Ultraperm to add magnetic shielding to my box. Currently have an aluminum foil for electrostatic screening and am keen to improve shielding further.
cheers
Ale
I've been using the interface for quite some time with great results. Occasionally I screwed it up, just by running it with grounded input (i.e. by pressing the front GND button) and by measuring a GND connected to earth. Evidently have a ground loop in my workshop between the DUT and the also earthed PC.
The way I realised this after some initial measurement is that the THD goes to the roof as driven signal back to the SC is heavily clipped. The DRV 134 (U7) gets really hot as clear signal that is damaged. By replacing it, all goes back to normal and obviously y carefully deselect the GND button back to float to avoid same issue twice!
I was about to buy some spare DRV134 when reading this thread found that the THAT 1646P08-U was used by some other people. It is not just cheaper, but also has better THD and lower noise level. Any experience or suggestions?
Also, is there any way of adding a protection to the DRV134 when in a ground loop to avoid burning it by my careless operation?
PS: I've bought a sheet of Ultraperm to add magnetic shielding to my box. Currently have an aluminum foil for electrostatic screening and am keen to improve shielding further.
cheers
Ale
Pete is still selling PCBs and panels on eBay I think. (eBay user: pmillett)
Yeah he's still selling them. Would anyone be willing to build one for me to buy completed unit?
Regards
Richard
An improved design?
I'm considering doing a design refresh on this. So, I started a new thread to discuss suggested design improvements for the sound card interface:
http://www.diyaudio.com/forums/tube...d-sound-card-interface-ideas-suggestions.html
Pete
I'm considering doing a design refresh on this. So, I started a new thread to discuss suggested design improvements for the sound card interface:
http://www.diyaudio.com/forums/tube...d-sound-card-interface-ideas-suggestions.html
Pete
... I brought it today and i think its a steal
Please say its worth the money i paid.
These are tools. There are tool freaks like you and me.
Rugged, accurate, flexible, good probes ... I have a similar Fluke model and love it and would be hard pressed to give it up.
There are plenty of US$10 digital volt/amp/ohm meters, but the one good one in a batch of mediocre gadgets is the one you will use the most and appreciate.
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You said: 'I think it's a steal'.
So what else do you want? Enjoy your purchase!
Jan
Ok so iv now got one of these built
When setting zero on meter i have float/gnd switch set to gnd and input on front shorted
I can get a reading of 00.0mw
With the switch set to float. I can only get it at 01.3mw
Have i done this right?
Kind regards
Richard
Whatever it is what you are measuring, floating the ground will make it pick up hum so you'll never get to zero.
Maybe you could have thought about it yourself?
The thing to remember again and again is that you never measure voltage at one point. You always measure voltage between two points!
Jan
"Its all relative, you know" ... "Ground loops happen."
... Both gnd and input are picking up the background voltages from your lights and household wiring ... SOP would be to set gnd to "not float" for the purposes of calibration. (Same, same with any oscilloscope, too.)
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I recently completed a soundcard interface, thats been on the slow burner.
Works nicely but I see an annoying 1KHz (and harmonics) when not enabling any signal through arta, weird, seems to come from the soundcard.
Measuring THD on a 950Hz fundamentals gives very nice results (Juli@ soundcard + some changes to the interface)
See attached THD plots.
Works nicely but I see an annoying 1KHz (and harmonics) when not enabling any signal through arta, weird, seems to come from the soundcard.
Measuring THD on a 950Hz fundamentals gives very nice results (Juli@ soundcard + some changes to the interface)
See attached THD plots.
Attachments
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