Diabolical Artificer
Active member
- Joined
- Aug 12, 2014
- Messages
- 32
I've recently been experimenting with various free software audio testing programs and ran a few tests yesterday on a valve amp I've designed and built. I ran some frequency response tests on it using first audiotester.de, then a simple frequency response program and lastly with REW.
Every test showed a less than flat response with it varying by as much as 10dB in places. I then ran a manual test using a very good vintage wein bridge oscillator (THD less than 0.01%) and a vintage B&K AC valve voltmeter. the response was flat from 2hz to 20khz with a slight dip at 4hz (1/2dB) and a slight rise of another 1/2dB from 10khz up to 20khz. I monitored the IP with a Fluke bench DMM, the OP with a Fluke 25 as well as the B&K AC voltmeter as well as both on a Tektronix scope.
So what's the craic? The Soundcard was calibrated on all three bits of software and the old test gear has also been recently calibrated, I tend to believe the old test gear. One thing I have noticed on a few of the software programs is that the sweep is modulated.
The only difference in the two types of measurements is that the PC software goes through an attenuator, both use the same dummy load. thought's?
Andy.
Every test showed a less than flat response with it varying by as much as 10dB in places. I then ran a manual test using a very good vintage wein bridge oscillator (THD less than 0.01%) and a vintage B&K AC valve voltmeter. the response was flat from 2hz to 20khz with a slight dip at 4hz (1/2dB) and a slight rise of another 1/2dB from 10khz up to 20khz. I monitored the IP with a Fluke bench DMM, the OP with a Fluke 25 as well as the B&K AC voltmeter as well as both on a Tektronix scope.
So what's the craic? The Soundcard was calibrated on all three bits of software and the old test gear has also been recently calibrated, I tend to believe the old test gear. One thing I have noticed on a few of the software programs is that the sweep is modulated.
The only difference in the two types of measurements is that the PC software goes through an attenuator, both use the same dummy load. thought's?
Andy.