Hello,
I bought RME ADI-2 Pro FS BE yesterday and wanted to try measuring my analog stereo preamp. Hope I didn't make too many mistakes, but if I did, I appreciate the input and help.
I connected ADI's output to Preamp's input and then Preamp's output to ADI input. That is now measuring Preamp, because i supposed that ADI is more accurate then preamp.
So, this is the result.
If you want more info, please ask and comment.
The preamp is Jeff Rowland Capri, and all connections were balanced.
Thanks
View attachment 121119
Hi
A few quick comments:
- switching UoM to dB would be more readable than %. The limiting factor is obviously noise, so dB makes even more sense (88dB SNR is more readable than 0.0039%)
- Make sure and show that measurement is done for a range limited to 20Hz-20kHz, otherwise noise may be out of display. Also, sampling rate (44k or 48k), window type and size should be specified to allow others to duplicate
- Input level and gain are arbitrary
Given Amir's standard is 2Vrms (unbalanced) or 4Vrms (balanced), you should probably use those as preamp input level (and 0 gain - RME input level = RME output level) per default.
Display the dashboard with those values.
If THD is then too high, lower input level to a value where SINAD is best. Specify this input value.
If Noise is still predominant, do the opposite: raise input level until THD starts to be predominant and you get the best SINAD.
Those are probably the 2 most useful dashboards
- If you have time you may check the gain limits for best SINAD with input level at 4V (or 2V)
- Try to measure 31 tones
(Don't saturate RME output, and show input level)
- Try to measure frequency response at 48k sampling rate or higher
- Channel balance vs gain level is useful
- IMD (Amir uses SMPTE IMD) vs input level and crosstalk vs frequency are other interesting measurements
...
The RME performance is way better than what you measure here.
It still makes sense to optimize it, as an habit, though.
So, at least, measure with RME input and output ranges where your level on RME is between -0.5 dBfs and -6dBfs.
For 4Vrms balanced, RME range should be +19dBu and level on REW at -4.7dBfs.
For 0 gain on preamp, RME should show the same -4.7dBfs with +19dBu range. If possible, check the preamp input and output voltages with a true RMS multimetre with a 80Hz signal to make sure.
There are other tricks to improve RME performance even further, but you don't need that here.