24 bit 96kHz seemed to work ok in and out on my soundblaster. I didnt get ASIO to spin first time so I used WDM. This was 16384 FFT, which was his recommendation for soundcard self-test. Easy to change. Arta is good, even I understand
Try all combinations in self loop test and keep the best one for THD and noise floor at -10dBV amplitude. The card's own thresholds demands are not great for tube audio testing in general.
Did some more Arta/ground/choke experiments today. I re-did my soundcard test and calibration at 24 bit 48 kHz. I run something like 1578 mV RMS out at -3 dB so the card clipped at self test. I went down to -6 dB. Self test is pic 1.
It says in the Atra documentation to put input near minimum on self test so I set it to 5%. Then I dont know how to do with DOT-tests. First 3 I kept 5% full pot, on the later I went up to 100%.
I released the chokes from their earthground plane with a thin piece of plastic. Quite better at high frequensies now. Pic 2
Pic 3 I took the chokes to audioground (not earthground). Not much of a difference.
In pic 4 I turned the chokes 90 degrees. I cant see any major change there either.
Pic 5 is 100 % sensitivity on soundcard input.
Pic 6 I removed eathground from the whole application (only connects thru RCA to soundcard). Not very good highs there.
Then I tested with different shielding of the chokes with metal, but the curves doesnt move so I can see it. I dont think the choles is bugging me now when I separated them from chassie/earthground. What really interferes is touching/tapping the application. Curves move up like crazy for a sec or 2. Maybe my 50 Hz is some microphonic.
I can see almost the same peaks on Salas measures. Not as big 50 Hz as mine but otherwise it looks quite alike.
What I dont know is to interprete this. What does the curves say?
It says in the Atra documentation to put input near minimum on self test so I set it to 5%. Then I dont know how to do with DOT-tests. First 3 I kept 5% full pot, on the later I went up to 100%.
I released the chokes from their earthground plane with a thin piece of plastic. Quite better at high frequensies now. Pic 2
Pic 3 I took the chokes to audioground (not earthground). Not much of a difference.
In pic 4 I turned the chokes 90 degrees. I cant see any major change there either.
Pic 5 is 100 % sensitivity on soundcard input.
Pic 6 I removed eathground from the whole application (only connects thru RCA to soundcard). Not very good highs there.
Then I tested with different shielding of the chokes with metal, but the curves doesnt move so I can see it. I dont think the choles is bugging me now when I separated them from chassie/earthground. What really interferes is touching/tapping the application. Curves move up like crazy for a sec or 2. Maybe my 50 Hz is some microphonic.
I can see almost the same peaks on Salas measures. Not as big 50 Hz as mine but otherwise it looks quite alike.
What I dont know is to interprete this. What does the curves say?
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I guess that is because I measure with only 5% input level on self-test. As the Arta guy recommends. I dont know why.
The cable I just spent a lot of work to fetch where it is now, because the comp is like in a desk-drawer-thingie. But I can maybe just switch input digitally?
An old Soundblaster Elite Pro
You'll be amazed how much unshielded cables will pick from the environment. They don't even need to be near psus. Run with no cables and let's see what it looks like, that will your reference noise. Also, you should do the calibration in Arta. That will give you some idea closer to reality, of dBs.
Oki Iko
Heres
Heres
- Calibration of output level in Arta with Picoscope
- Calibration of input level that clips at - 3 dB
- Chosen level - 9 dB
- Taking input sensitivity down to 5% for self calibration
- Spectrum test cables in loopback
- Test with input cable unplugged
- Cable plugged back
Attachments
Well, levels is one thing. I was maybe more interested in thoughts of the deviances/peaks. I can see on one of your measures Salas that you have them on the same places in some pics. 50, 160ish, 200 etc. Mine is a little bigger and some more. Is it way out for an unshielded test setup with chokes or am I on the ballpark according to Arda?
Your card levels look better now. Mine is R loaded bootstrap with input AC coupling, has a big trafo near also, not double mono. When I drive with signal those harmonics vanish from the FFT so I think its the Tx mechanical buzz they pick up when idling and I just watch the noise floor. Still my microphony is minimal.