sweetbeats
Reel deep thoughts...
Sorry and no offense too, but amplitude is amplitude and RMS is RMS. When we have a sine wave with 1V amplitude, RMS value of this signal is 0.707Vrms. For example with +4dBu = 1.23Vrms = 1.73Vpeak
No. Amplitude is the distance from a negative peak to a positive peak. You still measure amplitude if you are referencing the RMS wave...that IS the measurement from the peak of the RMS wave. So there is raw peak-to-peak amplitude, and RMS peak-to-peak amplitude, but we typically leave off the "peak-to-peak" reference when discussing measurement of RMS waves to avoid confusion. The signal levels specified in the Tascam manuals assume RMS values. SO...you ALWAYS should be using a true RMS measuring voltmeter with sufficient bandwidth capability to measure signals across the audio spectrum when working with a tape machine. If the Tascam manual cites a 1.23VAC amplitude, that means 1.23VAC RMS amplitude. And if you are using a true RMS measuring meter then it will be measuring the RMS amplitude of the signal (unless you switch it to measure raw peak-to-peak).
I think I am writing clearly. I do not do anything with ATR input channel sensitivity for now. Nothing. I just try to tell you that my 0VU input level is 1.4Vrms. It was measured between 2 and 3 pin of XLR connenctor.
I looked at the manual for your Fluke 177. Be aware it is only rated to be accurate (and only moderately accurate) from 45Hz to 1kHz. I would not use it to measure tone outside of that frequency range, and 1kHz is at the limit of its rated range, so likely to be the least accurate.
Your meter is an unbalanced meter. You do not measure between pins 2 and 3 of the XLR connector, you measure between pins 1 and 2, OR pins 1 and 3. Also, to be most accurate you want to take those measurements with the signal connected to the ATR or "loaded". This means you need to have a 'Y' cable connected, unless you can get to the back side of the XLR jack on the ATR while the XLR cable is connected and measure at the solder lugs or the jack PCB of the connector.
So re-check your measurement with the voltmeter probes connected to the proper pins and see what the level is at 0VU. Also, just to verify, your tone is what frequency? 1kHz?
When I apply ES-50 SMPTE signal to THIS input, on my VU meter I can see signal around -3dB. This is too much. SMPTE signal should be lower, around -10dB. I try to set it with VR1 trimmer, but still to high. Thats all. It was only information about how big signal from ES-50 is. I just curious why it is. It lets say rhetorical question.
I agree -3VU is too hot, it should be around -10VU, but first we need to really know to what signal level reference your VU meters are calibrated, and I'm not yet confident 0VU equals 1.4VAC RMS based on the meter you are using, and the way you are measuring the signal (measuring across pins 2 and 3, and measuring the tone with the signal unloaded.
VR1 is...on the ES-50? An output level trimmer? You probably clarified that earlier but I haven't read your entire post before last yet because if you are having level issues I thinks its important to first establish the source of that problem, and before we can do that we have to know how your ATR is setup. And that's why I'm saying all this stuff about how to measure, clarifying terminology, and making sure you understand the limits of your voltmeter.
So its not a rhetorical question, because until we actually establish what 0VU represents on your ATR, and verify you are correctly measuring signal, and verify what that signal is (frequency), who's to say the ES-50 timecode signal output is too big?
That 1.4Vrms is not so common - yes - I will calibrate my ATR to standard 1.23Vrms later.
I'll be curious to know, after you load the input, measure between pins 1 and 2 or 1 and 3 of the XLR, and clarify what frequency tone you are using, what RMS amplitude equates to 0VU. Once we know that, we can continue onward. I'll look at your previous post in the meantime as soon as I can.