Topic: R44, FR2LE - Why isn't the GAIN specified???

[sanaka]

Hi. This Q is more general than the 2 units mentioned, but came up because I am considering them.

I just don't get why there is not a Gain specification for these (and other) units. On a mixing board the gain knob for a mic input will read from 10 to 60 dB, for example. If you buy an Aerco preamp you can specify a gain range, like 10dB - 50dB or 30 - 70. A Sound Devices 702 mic pre will provide up to 70dB of Gain. Etc., etc... Gain is just the fundamental number describing anything with an amplifying circuit in it.

Neither the R44 or the FR2LE give this number anywhere I can find. What the hell is up? The closest seemingly possibly related figure in the R44 manual is:

Nominal Input Level
11 steps: +4,-2-,8,-14,-20,-26,-32,-38,-44,-50,-56

What does that mean? 60dB Gain? (i.e. 4-[-56]=60 )

The FR2LE manual states:

<MIC input>
Nominal input level : -50 dBu to -10 dBu

Again, what the heck is that?

Sorry if I am just ignorant of some simple correlation between "Input Level" and Gain that everyone knows about  But Gain just seems conceptually more relevant and effective for comparisons. I mostly record quiet acoustic stuff and often find myself pushing gain up into the noisy zone on my current equipment. All the excellent testing and observations on this board would be SO meaningful if I knew what gain range was under discussion!

Please take me to school!


Peace,
Sanaka

[Ozpeter]

Good question.  In my innocence I figured that it meant there was 4dB of attenuation and 56 dB of gain available in the case of the R-44, but that could well be incorrect.

[Roving Sign]

I think some of those might be mic sensitivity numbers...i.e. ideally you would match the input trimmer to the same spec as your mic...

check this thread...I wondered something similar once...

http://taperssection.com/index.php/topic,97381.msg1296933.html#msg1296933

[sanaka]

Thanks so much for the replies. I feel much better knowing "it's not just me" 

That thread with your inquiry Roving Sign was very helpful. I'm betting now that the stuff DSatz said there is probably right. Since the spec is named "Input Level" it makes a contorted sense that they are saying "set this knob to the nominal output level of the mic" The suspicion that this is what they mean had crossed my mind when I posted last night, but I think "Please God, no" crossed my mind simultaneously.

As I understand (which ain't much), how this would have to break down is: If you feed your mic a nominal reference acoustic signal, and set the trim to the nominal output level value of your mic, and the level knob to 0, you will get a nominal 0dB line level signal coming out. Which is just astoundingly useful because of course we're all going around recording 94dB, 1000Hz sine waves at 1 meter (or whatever the heck the reference acoustic signal is) all the time!!!

Seriously though, I am still pretty much a novice. Is there really some argument for setting gain "matched" to a mic's nominal sensitivity this way? I've always operated according to what I thought was the standard practice of adjusting gain, with level at 0, to achieve peak signal for the loudest expected sound, i.e. loud stuff=lower gain, quiet stuff=higher gain.

Peace,
Sanaka

[sygdwm]

i know my busman vintage mod fr2le goes to 11.

[sanaka]

So, you can get that little bit extra? 

[BayTaynt3d]

I'm not sure it's necessary to dig that deep...

I follow a simple rule myself with the R44, and that is to run the inner knob at zero (12 'o clock) so no digital gain/attenuation is used, and then I set the outer knob to the highest I can without clipping (watch out for clipping peaks on the meters AND/OR clipping inputs which cause the channel indicators to reverse color).

The other thing I kind of like about the stepped sensitivety is that if I need to change the level during a show, as long as I set a marker or write down the timecode, it's relatively simple to reverse in post cause you know exactly where it was and you know it was a 6 db change.

[sanaka]

Thanks for the reply, BayTaynt3d.

Your gain staging description is exactly how I would set up my (hopefully soon to be acquired) R44. Stepped gain for stereo is da bomb, crucial.

And you're right, it's not 'normally' necessary to obsess like I do. However, most of what I tape is apparently abnormally quiet - my own little acoustic band - and I've been squeezed hard against the noisy upper gain regions to get decent levels on equipment I have. Recently I shed the little array of Panasonic capsules I had been using and got a pair of Crown PZM-30D's, which are hotter, so have finally experienced a bit of headroom while recording. But even more would be nice.

Doug Oade graciously helped me (as he has always unfailingly done) understand gain vs. 'input sensitivity'. It is just as one would intuit it to be: sensitivity = inverse of gain. i.e. -56 input sensitivity, as on the R44, is just 56dB of gain. So no worries, even though I still think just 'gain' is a better way to conceptualize it.

The upper gain reaches of any mic pre start getting noisier, and this compounds because you are normally using this range to capture quieter sounds, so the noise floor is more prominent. So, 56dB max gain, which is maybe only 50dB before the noise gets troublesome, is not as awesome as say 72dB, as on a Sound Devices unit. But since I'm simply not fiscally looking at even a 702, I'm left with, well, my own little obsessiveness. 

If I really master myself for a moment and try to be objective, it's likely that a stock R44 would actually be awesome for me. But why work to attain objectivity when remaining paranoid is effortless? 

Peace,
Sanaka

[Ozpeter]

Here, with the R-44, a few weeks' experience has taught me that, with my particular mics, the "noon" sensitivity setting is right for symphony orchestra, the next one up is right for chamber music, and the next one up is right for even quieter music.   And now I won't ever need to look at the meters again.

[Ozpeter]

I know that it is generally accepted that recording something quiet with the middle gain setting of the Zoom H2 and then digitally amplifying in post-production, gives no worse a result in noise terms as recording with with the high gain setting.  In other words, there's no point in using "H", especially as that can result in an unexpectedly loud bit causing clipping.

I've not tried similar tests with the R-44 to determine whether the highest sensitivity settings are similarly not actually worth using - has anyone?

[sanaka]

Hey Ozpeter, thanks for chiming in 

When you say:

...with my particular mics...

do you refer to your Sennheiser MKH's? A pair of these and all my worries would vanish. Their output spec is like 25mV/-32dB, yes? My new PZM's are 7mV/-43dB. They so far seem perfect for what I'm doing, mind you, except they could be hotter. My next planned mic investment is a hotter, normal stereo pair, probably Avantone or Studio Projects (both I think around 15mV/-36dB).

Peace,
Sanaka

[Ozpeter]

Yeah, those MKH series mics can be used to power lights in a power cut!   I've had mine for about 20 years I think, and they've been my main pair on every recording since then, so if I divide the cost of the mics by the number of outings they've had, they've worked out pretty cheap.  Price then was about the same as now, so they've effectively got cheaper over the years. 

[DSatz]

Hi, sanaka--I'm sorry I didn't see your original message sooner. You wrote:

> I just don't get why there is not a Gain specification for these (and other) units. On a mixing board the gain knob for a mic input will read from 10 to 60 dB, for example. If you buy an Aerco preamp you can specify a gain range, like 10dB - 50dB or 30 - 70. A Sound Devices 702 mic pre will provide up to 70dB of Gain. Etc., etc... Gain is just the fundamental number describing anything with an amplifying circuit in it.

I think the conceptual problem is that in these recorders, the preamps are just one section of the unit, and aren't replaceable components with alternatives that you'd need to compare. As I recall the Nagra III recorder was arranged that way--you could buy a preamp for a dynamic microphone and/or a different preamp for a T-powered condenser microphone, and install them yourself; they didn't have "universal preamps" until the IV series. In that type of situation, the specifications of the preamp as a separate entity would be very important.

But the makers of these recorders aren't marketing them for use as preamps, so their voltage gain as such isn't directly relevant to most users. Considering their use as recorders, what the user needs to know is the range of signal levels (voltages) that the recorder can handle. For example, if the microphone input of a recorder overloads at only 100 mV (which is true for some consumer equipment), I'll need to use a "pad" (attenuator) if I want to attach a modern, transformerless condenser microphone to that input--otherwise some day I'll have severe distortion that can't be prevented with the record level control. That's vital information.

dBu is an informal term meaning: dB relative to an open-circuit (u = "unloaded") voltage of 0.775 Volts. That's an awkward reference level nowadays, but many decades ago it fit with Bell System practice (and to studio practice, insofar as U.S. studios used equipment which was similarly based on 600-Ohm transmission lines), in which the reference level was one mW into 600 Ohms. 0.775 Volts into 600 Ohms = ca. 1.29 mA, and 1.29 mA x 0.775 Volts = ca. 1 mW.

I hope this helps. If you have more questions, ask 'em!

--best regards

[Carlos E. Martinez]

As I recall the Nagra III recorder was arranged that way--you could buy a preamp for a dynamic microphone and/or a different preamp for a T-powered condenser microphone, and install them yourself; they didn't have "universal preamps" until the IV series.

The Nagra 3 only two inputs, one mic + one line, and you could not change the preamps. On the Nagra IV and 4.2 they offered different two mic preamp choices, one for dynamics and the other for Sennheiser MKH mics, feeding T power. Later on, when they released the IV-S, they developed the universal mic preamps that were also options for the mono 4.2 types, for dynamics, T and phantom mics. 

[sanaka]

I've not tried similar tests with the R-44 to determine whether the highest sensitivity settings are similarly not actually worth using - has anyone?

There's some testing on a another thread (the R44 vs. FR2L one?) that might address this pretty well. That's a good point that it might be better to record low and jack up in post even if you could record hotter, to preclude preamp noise at high gain. The more I ponder things, the more I crave some MKH's. Super hot output with super low noise. You're just never going to run into this particular problem you're asking about, are you Ozpeter? 

Peace,
Sanaka