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Topic: Strange RMAA Results (Read 4627 times) previous topic - next topic
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Strange RMAA Results

I'm trying to measure a Dacport with a Tascam US-1200 using a TRS to dual TS cable, and I get some really strange results:

https://onedrive.live.com/redir?resid=5B2A7...int=photo%2cPNG

I can easily verify by ear that crosstalk and distortion numbers on the Dacport are not this high.  I was trying to measure a headphone amp with "active balanced ground" using the Tascam.  Is it possible I damaged these inputs somehow?

Strange RMAA Results

Reply #1 –
Most likely your device is fine, because the first results seem good. It could a sync loss or something similar. Try an offline test when you create a WAV file with test signals, run it manually, and then trim the file and analyze in RMAA. Also post your resulting WAV file here.

Strange RMAA Results

Reply #2 –
I'm thinking you have a loose ground connection in the TRS plug/jack. When you break the ground on such a connection you can still access the L-R content. It is a common malady with headphones, for instance. You still get sound to both ears however the monophonic, L+R common content disappears.

Simply reseating the connection, pushing it in fully, and giving it a quick rotary spin (to scrape clean the contacts) often cures the issue. [A bad/intermittent solder point can't be cured quite so easily, but it is often the first problem, not the solder points.]

Strange RMAA Results

Reply #3 –
Quote from: Alexey Lukin on
Most likely your device is fine, because the first results seem good. It could a sync loss or something similar. Try an offline test when you create a WAV file with test signals, run it manually, and then trim the file and analyze in RMAA. Also post your resulting WAV file here.


How do I do an offline test?  Here's the wav file:

https://onedrive.live.com/redir?resid=5B2A7...hint=file%2cwav

Strange RMAA Results

Reply #4 –
I downloaded your file and found that left and right channels are swapped, please check your cables and hardware/software settings.

Strange RMAA Results

Reply #6 –
You may also try to re-run the test in 24-bit to test the true limit of your equipment. Since the file you uploaded is 3dB lower than RMAA's reference file and your signal chain may also have dithering applied, -92.4dB noise is already very close to the limit of a 16-bit test.

Strange RMAA Results

Reply #7 –
Quote from: bennetng on
You may also try to re-run the test in 24-bit to test the true limit of your equipment. Since the file you uploaded is 3dB lower than RMAA's reference file and your signal chain may also have dithering applied, -92.4dB noise is already very close to the limit of a 16-bit test.


Thanks!  I had to use gain on the Tascam to reach -0.2dB, and I assume this reflects the performance of the Tascam US-1200 more than the Dacport:

https://onedrive.live.com/redir?resid=5B2A7...hint=file%2cPNG

Strange RMAA Results

Reply #8 –
After googling about US-1200 I think the RMAA result is totally acceptable for a $118 interface. Some more expensive interfaces with similar functions from manufacturers like Roland, Steinberg and Focusrite have worse results. Just don't know if Tascam have good driver support or not.

Strange RMAA Results

Reply #9 –
Quote from: bennetng on
After googling about US-1200 I think the RMAA result is totally acceptable for a $118 interface. Some more expensive interfaces with similar functions from manufacturers like Roland, Steinberg and Focusrite have worse results. Just don't know if Tascam have good driver support or not.


Sure, although the numbers are kind of academic at this point.  The latest driver update was February of this year.

Strange RMAA Results

Reply #10 –
So, out of curiosity, what are the Tascam's crosstalk results, etc., now that the L/R channels have been sorted out?

Strange RMAA Results

Reply #11 –
Quote from: mzil on
So, out of curiosity, what are the Tascam's crosstalk results, etc., now that the L/R channels have been sorted out?


Here you go!

https://onedrive.live.com/redir?resid=5B2A7...int=photo%2cPNG

Edit: I believe the slight differences vs. the Dacport can be accounted for by the additional gain on input that I had to use for the Dacport.

Strange RMAA Results

Reply #12 –
Can you get better RMAA results if you switch your Tascam's input as GUITAR and use minimum input gain when testing the DACport?

Strange RMAA Results

Reply #14 –
Then it seems that the position of gain knob will not greatly affect sound quality, and the LINE/GUITAR switch can be safely used as a +4dBu/-10dBV switch as well.