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Aug 2018 in progress
I have started the
measurements on my projects in the year 2003 with the
Clio system 6
Audiomatica, this was a PC PCI audio card
(16bit 44KHz) with an external unit.
After some year these has been upgraded to the version 8 using the M-Audio Transit USB as audio card (24bit 96KHz).
The Clio system was designed for loudspeaker measurements but it can be used also to test amplifiers with some limits.
I have destroyed 2 times the input circuit of the Clio system during tube amplifier measurements.
To overcome these problems I have designed the EMU input project able to measure 1000Vrms like the anode of a 845 tube.
This project use the M-Audio 0404 USB audio and the Arta software.
Also if the M-Audio 0404 USB have 192Khz A/D converters the limit is 20KHz for the measurements.
To increase the frequency band and the distortion resolution are necessary 2 different systems for THD and frequency spectrum.
It is necessary an ultra
low distortion sine generator like the
board with an harmonics typically about -150dB.
MEASURE OF DISTORTION
Measure the distortion with
very good resolution is not possible with normal audio card so the my choice is
the Olivine 2 an USB Analog To Digital Converter by
In order to purchase this USB ADC contact Alexander Torres by contact page.
Follows the measurement of the Victor ultra low distortion sine generator with Olivine 2 unsing Arta software, the result is very good 0.0003%.
MEASURE OF FREQUENCY RESPONSE
To measure frequency spectrum I suggest an USB oscilloscope with minimun 12bit ADC and at least 1MHz band like the ISDS2062B by Instrustar.
This USB device have 2 input channels with an impedance 1Mohm 25pF and a variable output.
Here the frequency of the Gainclone amplifier using LM3886 chip.
Open the panel Sweeper of the interface and connect the amplifier using this layout.
At this time I have problem with the original 10x probe because it give a bad output result.