Yep, that's what mine says. I think the only thing that confuses me is the wording here: "As a complimentary amplifier is used for balanced output... ...when using the unbalance outputs for checks and measurement." Their use of "unbalance" there after talking about taking measurements with 3 pins is what I don't get.
Yeah it’s worded really weird. Here’s what they are trying to tell you...if you are trying to measure the output level at the XLR jacks, you either have to have a meter with a balanced input (not common...only found on more expensive audio test sets and equipment), and in that case if you want the test tone level at the output to equal +4dBm, you adjust the level so your balanced meter reads 1.23V AC RMS. Okay. Fine. But what if you’re like me and most of us and you only have an unbalanced meter with which to measure the output? When you connect your unbalanced meter to the complimentary balance amplifier output (via XLR pins 1 & 2 or pins 1 & 3), you are unbalancing the balance amp, and furthermore you are only measuring one side of the balance amp output. That +4dBm is achieved via signal on two conductors...pins 2 & 3 of the XLR jack. If you’re only measuring one leg of that complimentary pair, then when the output is at +4dBm, your unbalanced meter is going to read 6dB lower. -6dB is a halving of the signal level, so the correct measurement with an unbalanced meter at the XLR output is not 1.23V, but 0.615V (1.23V divided by 2). Does that help? Furthermore, best practice is to “load” the output...IOW to have the output you are measuring connected to an input. How do you do that? ‘Y’ cable. That way you can have the output connected to an input, but also still have access to the output vid the second arm of the ‘Y’.
While you're here, could I ask you another question? I want to make sure I am maximizing the relationship between my mixer and the 48. My Tascam M208 mixer has a nominal output at the group XLR (unbalanced) outs of 0dBu, while the Tascam 48 has a nominal output of +4dBm at the XLR (balanced) outs (but they specify the XLR connection there is 600 Ohms, and that 0dBm = 0.775v = 0dBu). So assuming I calibrate the VU meters to read 0 VU when each device is outputting its respective nominal level, there will always be a discrepancy between the VU meters on each machine. That is, 0 VU on the mixer will not equal 0 VU on the 48 if I'm understanding this all correctly.
How can I say this...don’t get hung up on there being a “mismatch”. Both the 48 and the M-200 series consoles’ internal nominal operating level is -10dBv okay? And understand that by “nominal” we mean some number that is in the middle of a range. 0dBu nominal outputs are typically going to have no problem driving +4dBu nominal inputs and vice versa, and when you are calibrating the meters on either the tape machine or the console, if you think about the instructions, the procedure, the meters are being calibrated to the device’s internal nominal operating level anyway. That’s why, for instance, on the tape machine you are being instructed to calibrate to different voltages depending on which outputs you are referencing (i.e. 0.3V for the unbalanced RCA jacks, 1.23V for the XLRs, or as we discuss above 0.615V if you are using an unbalanced level meter...) So the meters are actually calibrated to a common standard between the two machines, and even if it wasn’t common that wouldn’t matter, because what you really care about is that the meters inform you about the device they’re mounted to. So feel free to calibrate the meters of each device per the instructions for that device, and feel free to drive your tape machine inputs using the 0dBu outs on the console, but honestly why even mess with the balanced I/O? In case you didn’t know, the balance amp section on the 48 branches in and out of the unbalanced I/O, so by using the balanced I/O, unless you actually need to use it (i.e. you are interfacing a console that must interface hi level balanced I/O, which your console does not), or you have long cable runs (like greater than 25-30’) and are actually having issues with environmental noise interference, by using the balanced I/O when you don’t need it you are adding noise and distortion to your signal chain. Also, I suspect it is true for the 48 as well, but my 58 actually has significantly better HF spec when using the unbalanced I/O as compared to the balanced I/O. They included this detail in the manual for the 58. I see they redacted that set of specifications when they wrote the 48 manual.
I suppose my hang up is that I want to be able to drive the signals on both devices hot enough to gain some positive benefits, but due to the 48 being calibrated 4dBu hotter than the mixer I'm worried by the time I get suitably hot signals out of the mixer I will find the tape machine is receiving them at much too high a level (past the point of any positive saturation, etc.).
Refer to my above comments about nominal levels, etc., and to summarize, unless you tell me your mixer and tape machine are 50’ apart, or you live down the street from an AM radio station, if it was me I’d 100% skip the balanced I/O and go for the lower noise, lower distortion and higher bandwidth unbalanced interconnect. You’ll lose nothing in terms of drive and gain in all the above elements as well as simplifying the interconnect. Now here’s the other thing...people seem to fixate on this idea that to get “that tape sound” you have to use super high output tape and bury the meters. No. What you will get on your setup if you do that, depending on how you calibrate your 48 (more below), is likely some degree of line amplifier clipping (which on this type of gear is not typically desired), and little if any actual sought after third order harmonic tape saturation distortion. And furthermore if you are using any dbx noise reduction you’ll freak the crap out of those electronics and cause pumping and tracking errors. Now, I’m completely convinced that there is a whole echelon of tape enthusiasts that believe their line amp clipping dbx pumping artifacts are tape sat. But these are not the droids you’re looking for. If you are actually seeking tape saturation, then just calibrate your machine so the signal hitting the tape is marginally hotter. You don’t have to do this by shoving it down the tape machines inputs from the console outputs. Yes you want to maximize your signal level so it is as far away from the noise floor of your equipment as possible, but not to the point of clipping the console and tape machine line amps. When you set the record and playback levels on the tape machine during calibration, you are adjusting trimmers that set internally how hot the nominal level of signal is that goes to tape. Teac specified this nominal level on a 48 to be 250nWb/m @ 1kHz using “+6” tape. A nanoweber is a measure of magnetic energy. The higher the number, the hotter the nominal signal level. And the “+6” designator simply means the tape formulation will take 6 more dB of signal before eliciting 3% harmonic distortion than the original Ampex standard operating level. That’s right...the higher the number, the harder it is to saturate the tape. It also means you can hit the tape harder without distorting, and that means cleaner signal to tape and more sonic distance from the tape noise floor. See? There are all these things in play with a tape machine and tape formulations. I always advice first to set the machine up as designed, which is, in your case, calibrate to 0VU = 250nWb/m using +6 class tape. Interconnect using the -10dBv I/O on both the console and the tape machine and see what you think. Then experiment during tracking and start pushing the levels to tape during tracking. Rather than 0VU averages shoot for +3. Remember those are averaging meters, so your peaks are well past +3VU. Now if you want more saturation you can either calibrate for a hotter signal to tape during tracking (meaning during your record level calibration try increasing the record level trimmers so that your signal to tape is at +3VU, and then when you do your playback level cal you’ll turn down the playback level trimmers so that the hotter signal on tape is at 0VU level at the output jacks...see the point here is so that you can play around with having signal that is at 0VU averages at the tape machine inputs actually hitting the tape at +3 level, and then when you are playing back it reproduces at 0VU...input = output as far as volume level consistency, but what actually hit the tape was at 355nWb/m vs 250nWb/m. You’ve effectively increased the the level of signal to tape without impacting the headroom reserve if your input and output line amps, and for ease of visual reference everything still lines up to 0VU across the system. The other way to approach this is to set the machine up at 250nWb/m, but use a +3 class tape. In doing so you take the signal level intended for the higher threshold +6 tape and you lower the saturation threshold by using a +3 tape. Or you can combine these two approaches for even more saturation potential without potentially overloading your line amps. It can be a powerful tool to understand you have multiple gain stages in your system with independent trim controls so you can isolate *where* you want to push. And if it is to distort the tape, then you can isolate driving that stage, and/or experiment with different classes of tape.
