pre standard two preamp, and development of measurement methods

[PMA]

sound card is though not the best tool for serious measurements,

Agreed.

 

[syn08]

In single ended is much worse, but still acceptable for the DIYer.

Same card, same everything, in single ended mode. It pretty much sucks. Note the 60Hz harmonics, the channels asymmetry and the S/N ratio plunging down.

 

[BV]

Can You try it at 1V rms (0dBV)output signal?

 

[syn08]

Can You try it at 1V rms (0dBV)output signal?

Later, I'm on the road now.

 

[PMA]

Another suggestion might be a measurement at higher frequencies, like this THD 100kHz:

 

[syn08]

Can You try it at 1V rms (0dBV)output signal?

Balanced, 0dBVrms. Much worse, of course.

 

[KSTR]

Here's what EMU 1212M can do in balanced mode. In single ended is much worse, but still acceptable for the DIYer.

Thanks for that measurement! I was planning to purchase an ESI Juli@, but the EMU card seems to be a better choice in the same price range, maybe (except for the 48kHz restriction, but I haven't checked that for the Juli@ )

- Klaus

 

[syn08]

Thanks for that measurement! I was planning to purchase an ESI Juli@, but the EMU card seems to be a better choice in the same price range, maybe (except for the 48kHz restriction, but I haven't checked that for the Juli@ )

- Klaus

You are welcomed. Again, the limitation applies only for the internal loop (which you shouldn't use, anyway); you can use 192KHz to analyze an external signal.

 

[KSTR]

I have posted quite some time ago the reasons why a sound card is though not the best tool for serious measurements, I'll find the reference and repost.

Definitely. But we can agree it's pretty OK to do relative measurements (looking at changes) at least, can't we?

- Klaus

 

[syn08]

Definitely. But we can agree it's pretty OK to do relative measurements (looking at changes) at least, can't we?

- Klaus

Maybe, I don't know. I don't use a sound card for my regular measurements, I quickly got sick of the dependencies on the signal level, AC coupling only, lack of attenuators, unknown bandwidth, etc... And looking at that board full of cheap electrolytics makes me dizzy.

 

[PMA]

Balanced, 0dBVrms. Much worse, of course.

This is still very good, absolute number considered. But as I am interested in preamp circuits that produce almost no measurable higher order harmonics above 3rd, this result would be unacceptable. Probably a combination with notch filter would help, provided it does not rise noise background.

 

[PMA]

I made some measurements in last months to explore how usual audio box design behaves at high frequencies. Quite typical frequency response, extended to 1GHz, is now attached:

 

[PMA]

I also made an attempt to simulate this behaviour, look at the blue plot:

 

[grenert]

Do any of these (or other) software packages work with a National Instruments DAQ card? Are they limited exclusively to sound cards?

 

[Wavebourn]

I am going to try it with my TASCAM US-122 device, I hope it works well.

PS: Thank you Pavel for saving the thread.

 

[PMA]

My intent is to show results with a box milled from 8mm Al plates, after it is produced. I believe in 2 or 3 weeks.

 

[KSTR]

Pavel,

what do you think of this material, a sandwich of aluminum foam between aluminum panels?

http://www.gecom-technologies.com/ems_haupt.htm
and especially
http://www.gecom-technologies.com/ems_messungen.htm
(@all: translate with google if you don't read german)

From the measurements they provide this looks pretty nice.

They are also trying to get into the HighEnd realms, from what I can see they do it very right, especially as they are very concerned with HF ingress and clean power supply. Devices that look that ugly as these have to be good
http://www.gecom-technologies.com/audio_haupt.htm
(some english text there)
http://www.gecom-technologies.com/audio_entwicklung.htm

- Klaus

 

[PMA]

IMO we have 2 completely separated issues:

1) material of the box, and its shielding properties (including linearity, non-saturation),

2) leaks in the shielding box (even if made of 100% EMI proof material) like insulated connector mount, power supply input.

 

[PMA]

some small progress

 

[Wavebourn]

Hi Pavel;
speaking again about observing of distortions, did you try something like this?

http://en.wikipedia.org/wiki/Lissajous_curve


Sometimes it is very revealing, especially when phase modulation is involved. I used it developing guitar effects.