Pete Millett ATEST

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Dave the bass
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Post by Dave the bass » Fri Dec 27, 2013 9:47 pm

Has anyone here who's built a Pete Millett ATEST interface bothered fitting IC's U5 and U2 (14 pin devices) into sockets like the 8 Pin devices are?

Is there a reason this isn't a good idea?

DTB
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Post by Andrew » Sat Dec 28, 2013 12:16 am

Yes, I did sockets for all of mine, never know what you might blow up when its test gear.

Interestingly, the data sheets say that some of the devices shouldn't be put into sockets...but hey ho...

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Post by jack » Sat Dec 28, 2013 11:34 am

Dave the bass wrote:Has anyone here who's built a Pete Millett ATEST interface bothered fitting IC's U5 and U2 (14 pin devices) into sockets like the 8 Pin devices are?

Is there a reason this isn't a good idea?
Yes. Stray parasitic capacitance between the pins - generally, this is an issue normally only for very high slew rate amps - if you are trying to get every last ounce out of your system, trust yourself and solder to the PCB - Pete's design is quite specific about this. For reference, there is about 1pF between adjacent pins in a typical DIL socket...

If you absolutely MUST use sockets, make sure that they are hand-turned and made from pure, oxygen-free, silver that have been cryogenically treated and plated with 24ct Au. :)

HTH

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Post by Dave the bass » Sat Dec 28, 2013 11:50 am

nickds1 wrote:Pete's design is quite specific about this.
Is it? I couldn't find anything relating to not socketing the 14 pin devices anywhere on his site or the mammoth 68 page thread! Erks! :-)
nickds1 wrote:If you absolutely MUST use sockets, make sure that they are hand-turned and made from pure, oxygen-free, silver that have been cryogenically treated and plated with 24ct Au. :)

HTH
I'm sure the ones from Maplins are all that...and more! :lol:

I trust my soldering skills... what I don't trust is me measuring things correctly and connecting things up correctly everytime using computers and DUT's and wires n stuff and actually understanding what I'm doing!

Thanks BTW Nick and Andrew.

Onwards!

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Post by Andrew » Sat Dec 28, 2013 5:31 pm

Yes, the one I recall is the differential op amps as it is trimmed to obtain close to ideal balance, if recall correctly.

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Post by Dave the bass » Mon Feb 03, 2014 8:45 am

Dave the bass wrote:Dunno if anyone else has seen this but the December issue of 'Everyday Practical Electronics' has construction details of another USB Interface that might be interesting to some here too.
You know I've been quiet recently.... well :-) I thought I'd have a bash at the EPE USB IF project.

Ta dah!
Image

Image

Blummen works n'all!
Image

Image

I downloaded a 21 trial of measurement software that EPE featured, crikey its intense. Its called Virtins Multi Instrumment 3.3 Admitidly this is the 1st time I've played with measuring software but there's so much thats tripped me up eg. Why am I seeing two identical traces on the scope when I have different signals into Ch A + B... answer.... because you hadn't set the PC Windows driver to 'see' a 2 channel i/p Dave. Duh! Only took about 2 hours to suss that one.

Its all learning.

I might try the Audio Tester SW next that you fella's use with the Millet box.

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Post by jack » Mon Feb 03, 2014 10:09 am

Woooo Hoooo !

Very nice - what sound card are you using?

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Post by Dave the bass » Mon Feb 03, 2014 11:01 am

The interface based around a PCM2902, trickiest little sausage I've ever soldered onto a PCB, SMT natch which I'm not geared-up for but do have a steady hand :-)

Windows sees it as a USB Stereo CODEC. Steep learning curve ...pah! Vertical more like! Just you wait until I learn what to do with it. Might be a long wait!

Its been projects a-go-go here recently, just finished an AK4396 DAC for the project room Touch and I've been trying to get an ESS9023 DAC to receive I2S from a CM6631a unsuccessfully, thats for another thread mind.

My beloved Weller TCP from 1982 has conked out too :-( I don't think it could stand the intense pace of my builds recently...

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Post by jack » Mon Feb 03, 2014 11:26 am

Dave the bass wrote:The interface based around a PCM2902
Is that the "C" variant? The "A" and "B" are deprecated...

http://www.ti.com/product/pcm2902c

Only has 48kHz sampling max - is that fast enough to detect and measure higher-frequency effects - even at base Nyquist levels, that's a top end of 24kHz which means that unless input filtering is used there will be in-band aliasing artefacts which will confuse your spectral and distortion analysis.

Ideally you want to be sampling at 96 or preferably 192kHz... the SNR will also be greatly improved by oversampling then digitally filtering -

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Post by Dave the bass » Mon Feb 03, 2014 3:34 pm

Yeah, the C variant. I knew before I built it that its not exactly a hi-end bit of kit but it seems like a good simple way into USB linked multifunction measurements. I'll say again... I have NO experience in this area at all! :lol:

The sound card (M-Audio Transit 24/96) I'd like to use with the ATEST box is almost always in use here at work so I'd need to buy a 'proper' sound card at some time before I start using that in earnest.

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Post by figlet108 » Mon Jun 16, 2014 12:14 pm

I was going to start a new thread about Pete's ATEST but saw this and thought I'd ask my noob questions here for efficiency.

Both me and Thomas are new to this so prepare for some hand holding requests... :)

First of all, I want to shield the case and was originally going to get copper tape like this one
I assume I don't need one with conductive adhesive - or do I?

But then I read on this thread about the Ultraperm 80 stuff that Nick got which looks good too.

Which is the best bet and do we need to avoid bending the Ultraperm as with MuMetal?

Thanks.
Jason

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Post by James » Mon Jun 16, 2014 1:15 pm

Dave the bass wrote:Yeah, the C variant. I knew before I built it that its not exactly a hi-end bit of kit but it seems like a good simple way into USB linked multifunction measurements. I'll say again... I have NO experience in this area at all! :lol:

The sound card (M-Audio Transit 24/96) I'd like to use with the ATEST box is almost always in use here at work so I'd need to buy a 'proper' sound card at some time before I start using that in earnest.

DTB
http://www.ebay.co.uk/itm/M-Audio-Audio ... 4d1f0b24ec

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Post by pre65 » Mon Jun 16, 2014 1:23 pm

That item has just gone, at 13:20.
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Post by Dave the bass » Mon Jun 16, 2014 1:32 pm

Bum, wasn't me. Thanks for the heads up James and Phil.

Jason, WRT screen. I seemed to have a lot of background noise without the screening so I bought but haven't installed yet some of that self adhesive Mu Metal sheeting Nick linked to. Since the good weather has been here I've not done much DIY-ing, I'm a foul-weather Fettler.

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Post by thomas » Mon Jun 16, 2014 5:02 pm

Hi
Yes I too am the proud owner of a P Millett interface.
I am gathering some bits to make an inverse riaa from Morgan Jones 'building valve amplifiers'.
I too need a soundcard, to go with a vista laptop i've inherited. Presumably a 24/96? Any recommendations please?
Thanks
Thomas

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