Topic: R-26 and input sensivity on SBD question (paging Ted G, others)

[acidjack]

Encountered a weird issue with my R-26 last night, which ended up fine, but I'm curious what I saw.

I had mics running into the XLR ins, everything normal there.   Into the 1/8" I had an SBD feed from the 2trk 1/4" line outs of an Allen & Heath board.  I had the input sens set to LOW. According to the manual, p. 105, the maximum input when set to low is +4dBu, which I believe is the same as pro line level. 

In addition, I had -12dB attenuators in the chain, since I wasn't that familiar with how low the input sensitivity of the R-26 could be.

My levels came out fine, but I noticed that the very last light at the very end of the meter for the PIP input would turn from white to black at times when the vox got loud. I assumed this was is the clip light, although the R-26 has a red "PEAK" light which I'm not sure applies to the plug in power input.  It did not light. The attenuators were working fine (I tried removing one during the opening band, and indeed, my levels jumped 12dB and the light stayed on longer).  I should also note that the indicators that show the most recent peak level never hit zero; they hung around -9dB at highest even during those vocal "peaks".

I asked the engineer if he could turn the output down, but he could not. He told me after the first set that he was ramming the levels pretty hard on the vocals because all of these bands had really noisy guitar amps. He said his own levels were super hot on the board. 

I had no idea what else I could do, so I just engaged the limiter on the PIP input (incidentally, a nice feature, since I think the -44 only lets you "Group" the limiter by channel but not engage for one group and not for another) and let it go.

The waveforms on the resulting recording are extremely ugly looking-- like stalactites, with deep downward peaks that aren't matched by corresponding upward peaks.  However, I do not hear distortion and they sound "fine" (i.e., like small venue board feeds with mostly vocals and some percussion).

I am wondering if what I'm seeing is a result of something that the engineer did, having to do with the venue's gates and compressors. I don't know enough about that stuff to speak authoritatively, but the waveform would seem to suggest that something like that was going on.

The only other mystery is why the end of the level meter behaved like that. It continued to do it even after I engaged the limiter, so I'm not entirely sure what was going on.

Thoughts?

[yates7592]

I dont know about sbd feeds because I never get them. But the spec max input level for the 1/8"  jack is about -7.5dBu from memory. That is at the default recorder input level of 50. Of course if you drop the input level dial to say 30 that would improve to about 2dbu.  The 4dBu input in the spec relates to the XLR inputs. I dont know if this explains the problem. I read somewhere that it is recommended to use a -20db pad on the 1/8" input for sbd feeds.

[acidjack]

I dont know about sbd feeds because I never get them. But the spec max input level for the 1/8"  jack is about -7.5dBu from memory. That is at the default recorder input level of 50. Of course if you drop the input level dial to say 30 that would improve to about 2dbu.  The 4dBu input in the spec relates to the XLR inputs. I dont know if this explains the problem. I read somewhere that it is recommended to use a -20db pad on the 1/8" input for sbd feeds.

What you're quoting, I think, is the average input level when the knob is at 0. I believe that is different than the actual sensitivity, no? 

It's all on page 105 of the manual fwiw.  I'm pretty sure what I am quoting applies to the PIP input. 

That said, maybe I will get a -20dB pad...

[yates7592]

My understanding, and I might well be wrong, is that the nominal values quoted are at a level of 50. The maximum  values quoted in the spec relate to the input levels right down at 1.  So if you were recording the sbd feed at 50 your max ouput level would be a lot less than 4 dbu.

[Todd R]

My understanding, and I might well be wrong, is that the nominal values quoted are at a level of 50. The maximum  values quoted in the spec relate to the input levels right down at 1.  So if you were recording the sbd feed at 50 your max ouput level would be a lot less than 4 dbu.

I don't have an R-26 (though I keep considering one), but from the specs it does look like the R-26 should take a signal as hot as +4dbu on its 3.5mm input.  Though as yates notes, this might be with input levels down to their lowest setting.

I'm not sure what you're referring to regarding maximum output being less than +4dbu.    +4dbu is the max input rating, not sure what the reference to output is about.

AJ -- where did you have your levels set when you had this problem?

[aaronji]

I had mics running into the XLR ins, everything normal there.   Into the 1/8" I had an SBD feed from the 2trk 1/4" line outs of an Allen & Heath board.  I had the input sens set to LOW. According to the manual, p. 105, the maximum input when set to low is +4dBu, which I believe is the same as pro line level. 

I think the +4 dBu on the mic input is a maximum, whereas the pro line level +4 dBu is nominal.  So the soundboard could get much hotter than +4 dBu...

[yates7592]

My understanding, and I might well be wrong, is that the nominal values quoted are at a level of 50. The maximum  values quoted in the spec relate to the input levels right down at 1.  So if you were recording the sbd feed at 50 your max ouput level would be a lot less than 4 dbu.

I don't have an R-26 (though I keep considering one), but from the specs it does look like the R-26 should take a signal as hot as +4dbu on its 3.5mm input.  Though as yates notes, this might be with input levels down to their lowest setting.

I'm not sure what you're referring to regarding maximum output being less than +4dbu.    +4dbu is the max input rating, not sure what the reference to output is about.

AJ -- where did you have your levels set when you had this problem?

Yep i meant input not output.

[Todd R]

Yep i meant input not output.

Oh, I got it -- you mean the max input level will be less than +4dbu if the recorder is set to 50.  I'm a little slow today...

[acidjack]

My understanding, and I might well be wrong, is that the nominal values quoted are at a level of 50. The maximum  values quoted in the spec relate to the input levels right down at 1.  So if you were recording the sbd feed at 50 your max ouput level would be a lot less than 4 dbu.

I don't have an R-26 (though I keep considering one), but from the specs it does look like the R-26 should take a signal as hot as +4dbu on its 3.5mm input.  Though as yates notes, this might be with input levels down to their lowest setting.

I'm not sure what you're referring to regarding maximum output being less than +4dbu.    +4dbu is the max input rating, not sure what the reference to output is about.

AJ -- where did you have your levels set when you had this problem?

The level knob was at 9 o'clock.  The "clip" light did not appear to be affected by where the level knob was. The actual levels were peaking around -9dB at the max.

I may have garbled some terminology, but my understanding was +4dBu is pro line level (which should be compatible with any SBD) and that the manual seems to indicate that is what the PIP input is when it's on LOW with PIP OFF.  To put it another way, on my R-44, if you turn the "clicky" all the way down, the input sensitivity is +4dBu -- the lowest sensitivity it is capable of.  I thought that it was more or less impossible to overload a line level input at that sensitivity.  Well, not impossible, but in terms of taking a line out from an SBD, I would have thought it was pretty tough unless the guy was overloading the SBD itself (which maybe he was... he wasn't the regular house guy and he was screwing up other stuff).

And more oddly, as I said, the recording is fine, so I really don't understand why those lights were coming on unless the clipping was just not very severe.

[yates7592]

I don't know if this is the cause of the "problem" or not, but the max input level of +4dBu quoted in the manual is a maximum and in my understanding relates to the lowest input level dial setting (i.e. 1, at 6 o' clock). The manual also gives the 'nominal' input level limit of -7.5dBu (at the default input dial setting of 50, 12 o' clock). Your input level on the dials was 9 o'clock, so probably about 25? I think that would give a maximum input level of about -2dBu or thereabouts, which I guess might have been exceeded by the SBD feed. The pro line +4dBu pro line-in value normally relates to nominal, which is some 12dBu higher than the R-26 1/8" in jack can take at nominal levels. However, you mentioned you had a -12dB attenuator on, so that would have still been ok provided the SBD feed didin't exceed +10dBu. I'm getting confused now.... - am I confusing my dB's and dBu's ? Me thinks so.

[acidjack]

^   Certainly I could be.  Anyway, the whole thing just makes me curious.  I assume nobody disputes that those lights on the end are the clip lights, right?  Although then why is there the PEAK light as well?

[aaronji]

As I understand it, the +4 dBu maximum on the mic input means that the input will distort if the signal exceeds +4 dBu, regardless of where the gain is set*.  The +4 dBu nominal pro level on the board represents the typical level the board was designed for, but is nowhere near the maximum output level, which is usually around +24 dBu (give or take).  If the sound guy was running things hot, the output could have easily exceeded +16 dBu (+4 dBu max of the recorder plus the 12 dB from the attenuator).

*There should be a gain setting at which a +4 dBu signal reads as 0 dBFS on the recorder; that may or may not be the lowest gain setting (I have no idea about the R-26).