I've been asked about how the Burson V6 discrete operational amplifiers would perform in the Muffsy Phono Preamp quite a few times. They don't seem to have many published measurements, so I thought I'd give it a go.
To perform the measurements, I have a QuantAsylum QA401 audio analyzer. This will obviously not be measurements of datasheet quality, but I still hope I can find out if these op amps will work for the low signal levels from an MM cartridge. They have JFET inputs and work with up to +/- 16.5V power, which are two of the basic requirements.
To get the very best results from the QA401, I followed the tips in this blog article. Using the R- output and the R+ input gives the best measurements. I tested signal levels to find what gave the cleanest input signal and the very best THD measurements, which was -10.33 dBV.
A loopback test on the QA401 shows that I get a THD of -118.7 dB / 0.00012%. Operational amplifiers have great noise rejection, so I might get somewhat better measurement results. It shouldn't be by much though, this is basically as good as it gets.
The noise graphs at the bottom of this post shows that using a BNC cable (I tried several of them of varying brand and length) adds about 0.5 dB noise. I can't do anything about that...
For reference, here's the noise floor of the QA401, inputs shorted with BNC cables (hires image):
And finally the QA401's noise floor with the inputs shorted with BNC terminators (hires image):
