Topic: Dynamic range, mic vs line inputs.. gain, pads on mics, preamps, in-line filters

[Gutbucket]

Quoted from another thread, but exactly what I was working towards here-

... When sound is so loud that it threatens to overload the microphone's own electronics (a capsule is nearly impossible to overload with sound alone), you have to use the pad in the microphone. In effect, it operates between the capsule and the "amplifier" of the microphone.

But the pad in a microphone, with very few exceptions, raises that microphone's noise level relative to its sensitivity, since it reduces the output of the capsule at all levels without affecting the (fixed) noise level of the mike's electronics. The pad at the input of a recorder generally doesn't have this problem, so if you can use the pad in the recorder, it's generally preferable.

If a recorder is being overloaded with signal from the microphones, and the recorder has no pad of its own, then it's generally better to buy in-line resistive pads and use them at the inputs of the recorder, rather than use the microphones' pads for this purpose. In a pinch, however, a moderate amount of extra noise is preferable to overload distortion ("brickwalling")--so if you have absolutely no alternative, use the pads in the microphones.

Most microphones nowadays can handle such high sound pressure levels that the only times they overload are when the sound levels are actually hazardous to your hearing--or else something else is going on, such as wind noise or inadequate powering.

--best regards

[BayTaynt3d]

Thanks for that, that's good info...

Now, what kind of started some of this was my use of my mic's -10db pad in order to avoid using my R4's -20db pad. The trade-off sounds like it's an "add more noise by using the mic's pad and less noise from the R4's preamps b/c you don't have to use as much gain" vs. the "don't add noise by using the mic's pad but b/c the R4's pad is bigger at -20db you add more noise by having to using more gain on the R4 preamps." I'm also a little curious about whether using a larger pad (in general and all other things being equal) is worse than using a smaller pad.

But beyond that, and upon reflecting more on DSatz's comments, it seems like I might want to reconsider using the R4's pad a little more often.

One other question I have -- given what DSatz just said -- is that as an owner/user of AKG480's, I actually have a +6db setting on the same switch as the -10db pad (it's +6, 0, -10). I wonder if by using that, I can actually raise my signal higher off the noise floor, which would be great. If that's true, then it'd be worth doing as long as the signal doesn't overload the mic's built-in preamp in the body. Considering I record a lot of acoustic jazz, classical, and chamber music, I might be better off going +6 on the mic, and then go line-in (pad on) on the R4 if it's too loud for mic in. That'd get my signal higher off the noise floor by using the +6, then the pad on the R4 would keep me from clipping the recorder, and because of the +6 on the mics, I'd need less gain on the R4. This might be moot though, because I can usually run mic-in for a lot of my gigs (at 0 on the mics).

Interesting...

[ScotK]

With all the components, variables, and options, it's sort of amazing that ANY
recording turns out OK!

scot

[Gutbucket]

Attenuating later in the signal chain should also reduce low level EMI interferences picked up in the cabling and any other intervening equipment (such as a mic powering box).  In general I'd think that the better option unless there is reason to fear of eating up all the desired headroom in some part of the chain before the pad.  The other issue that is a mysterious, hidden bugaboo is "what is actually going on with the gain structure of these all-in-one recorders like the R-4?"  Does changing input sensitivities on the box (via switch or input jack choice) mean switching simple resistive attenuation in and out, increasing or reducing an analog amplification stage, adding or removing an additional analog gain stage, or doing a digital signal adjustment?

I guess I haven't payed enough attention to the manufacturer's spec's of mics that have switchable pads either.  Do their maximum SPL before clipping measurements indicate if those measurements were made with the internal pad engaged at it's most attenuating setting or flat?

It would be really interesting to setup a 'research' recording rig that included metering marked with the appropriate range between noise floor and clipping (or some other acceptable distortion level) at every stage of the chain to really get a handle on what's going on.

I imagine I could learn a lot experimenting with various combinations of settings and also get a great 'seat of the pants' feel for the level magnitude differences of the various stages.

[BayTaynt3d]

Pretty sure in the R4 that the mic/line switch is simply a 20 db pad, but YMMV with other devices.

[Kyle]

Ahh, I've read this thread a few times but just can't seem to nail down the answer I am looking for. When running Sennheiser ME-40s > Sony TC-D5 PROII I need 30db of reduction to avoid overload. I ca get away with 20db in quieter settings but FOB and rock'n'roll PA's necessitate 30db. So what is the best option? Use the 20db pad on the deck and a 10db inline pad or just use a 30db inline pad. I just want to get as much out of the D5's mic-pre as possible, and I don't know much about the quality of the 20db attenuator circuit in the D5 Thanks!!

[BayTaynt3d]

In that case, and from some of what I took from this thread, you might be better off with the 30db pad. The logic was that when using the pad on the mic, you are basically giving up some of your signal to noise ratio on the mic. The pad on the mic is really designed to help prevent overload of the mic body itself, it lowers the signal before its own circuitry. (I think, LOL.)

[Kyle]

In that case, and from some of what I took from this thread, you might be better off with the 30db pad. The logic was that when using the pad on the mic, you are basically giving up some of your signal to noise ratio on the mic. The pad on the mic is really designed to help prevent overload of the mic body itself, it lowers the signal before its own circuitry. (I think, LOL.)

Thanks for the quick response!

I have been following the idea behind giving up some s/n when using the pad on the mic - great info, BTW - but these mics have no onboard pad, leading me to the use of xlr in-line attenuators. So I am still not sure which approach is the best. 30db Attenuator and no attenuation on the deck, or 10db attenuator and 20db attenuator on the deck?

I may be over thinking all of this- just want to maximize s/n and get the most out of this little beast!

Thanks again