EricZenviewStud
Member
Hi all,
I know most of you know about these three products ! , but as I never could find actual results of the three used together, and as this gives one of a hell of a impressive measuring tool in my book, without further due here are my results :
after finally upgrading from a QA400 to a QA403, I ran some tests and comparaisons using QA403 + Cosmos APU Notch + Victor generator.
Notch APU + 6db
I Think pictures speak louder than words !
How to get there , I followed Mat (Quantasylum) notch procedure where he details how to run a frequency test first then with file export I got the notch weighing file automatically. Thank you Mat for such a great feature ! Before I did that I had measured the Victor frequency which in the picture is 997,489Hz and not 1Khz… you have to let your Victor oscillator warm up and measure i’ts frequency then…
I did this tests three times, to make sure I was abble to “REPEAT” my measurements !
I did, sometimes if you don’t wait long enough you’ll get a THD of -141,77 db !
When I started the tests I ran the notch without the +6db and got first this :
Notch with APU 2
Which was my first trial , than I used the +6db and got consistently still better results all the time…
I took care of comparing how much “error” you would get without no weighing / no displayed correction , like when you are running it with a ten year old QA400 and the results are :
Notch APU No Correction
THD = -141,84 db instead of -141,22 db… I saw on average -0,7db or less imprecision still very impressive in my book … SNR = -121,25 instead of -120,97…etc…
So this lead to my tests of the OLD QA 400 and the results are :
APU NOTCHVICTOR SUSBSTRACT30DB+6DB
This the best THD measurement I could get lowering the output of the Victor oscillator to be just at -0,1 db input at the QA 400 , Quick results when you take off -30db ,
THD = -130 db for a ten yeas old unit !
best SNR / THD+N I could get :
APU NOTCHVICTOR SUSBSTRACT30DB
Quick SNR = - 120 db ,
THD = - 128,8 db,
THD+N = - 119 db
My Setup:
I power the victor oscillator with a lab bench power supply old style that is not noisy, I run the COSMOS APU on a battery pack. For the QA 400, I use an OPTOISOLATOR on the QA 400… to mimic newer units and be abble to do floating (quasi) symetrique measures with the older unit plus my -20 db / -40 db homemade QA probe and I lower the Victor oscillator output with the pot with the QA400…
In my book these are remarkable numbers for both units ! and a fairly inexpensive way to be like the big boys!
Cosmos APU + Victor Analog Oscillator
I know most of you know about these three products ! , but as I never could find actual results of the three used together, and as this gives one of a hell of a impressive measuring tool in my book, without further due here are my results :
after finally upgrading from a QA400 to a QA403, I ran some tests and comparaisons using QA403 + Cosmos APU Notch + Victor generator.
Notch APU + 6db
I Think pictures speak louder than words !
How to get there , I followed Mat (Quantasylum) notch procedure where he details how to run a frequency test first then with file export I got the notch weighing file automatically. Thank you Mat for such a great feature ! Before I did that I had measured the Victor frequency which in the picture is 997,489Hz and not 1Khz… you have to let your Victor oscillator warm up and measure i’ts frequency then…
I did this tests three times, to make sure I was abble to “REPEAT” my measurements !
I did, sometimes if you don’t wait long enough you’ll get a THD of -141,77 db !
When I started the tests I ran the notch without the +6db and got first this :
Notch with APU 2
Which was my first trial , than I used the +6db and got consistently still better results all the time…
I took care of comparing how much “error” you would get without no weighing / no displayed correction , like when you are running it with a ten year old QA400 and the results are :
Notch APU No Correction
THD = -141,84 db instead of -141,22 db… I saw on average -0,7db or less imprecision still very impressive in my book … SNR = -121,25 instead of -120,97…etc…
So this lead to my tests of the OLD QA 400 and the results are :
APU NOTCHVICTOR SUSBSTRACT30DB+6DB
This the best THD measurement I could get lowering the output of the Victor oscillator to be just at -0,1 db input at the QA 400 , Quick results when you take off -30db ,
THD = -130 db for a ten yeas old unit !
best SNR / THD+N I could get :
APU NOTCHVICTOR SUSBSTRACT30DB
Quick SNR = - 120 db ,
THD = - 128,8 db,
THD+N = - 119 db
My Setup:
I power the victor oscillator with a lab bench power supply old style that is not noisy, I run the COSMOS APU on a battery pack. For the QA 400, I use an OPTOISOLATOR on the QA 400… to mimic newer units and be abble to do floating (quasi) symetrique measures with the older unit plus my -20 db / -40 db homemade QA probe and I lower the Victor oscillator output with the pot with the QA400…
In my book these are remarkable numbers for both units ! and a fairly inexpensive way to be like the big boys!
Cosmos APU + Victor Analog Oscillator
