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[dejacky]

Hi,
I noticed (particularly) on drums I get digital overloads that sound horrible and I only like the sound of my mics on vocals with gain turned up (but this overloads the signal into the pc when I get slightly louder). So, I think I need a limiter or compressor so the loud parts don't overload the PC input.

I'm feeding my audio signals through an SM ProAudio PR8 8 channel preamp directly into my RME Multiface A/D and I've tried adjusting levels to no avail...it ends up sounding useable, but not to my satisfaction as when the gain is turned up . My Drum setup is 3 mics for now (2 Oktava MK012 overheads & 1 AT3035 for kick drum).

Do I need a particular compressor or limiter and what do you all suggest for under $200 & at least 2 channel (including used equipment)? Thanks in advance .

[John Ivan]

Hi;

I'm not sure what you mean when you say you like the sound better when it's louder. There can be a difference in how a pre amp sounds in it's "sweep" from minimum gain to max gain but, this should not be a huge difference in your case. There can be a small difference in how hard you hit the converters also,within the "clean" boundaries of the converter but, I think what you are describing might be this: You like the sound better when the monitors are louder. While a compressor or limiter might be handy to have around, It sounds like you need to record at lower levels and monitor the results louder. I don't think it's a difference in tone you are hearing as much as a difference in volume. A compressor or limiter can help give you a variety of sounds and they can help you get more average level but it sounds like you just want to hear it louder. Just my 2 cents.

[josh]

One of the big limitations of that SM Pro Audio PR8 is that it only has 40dB of gain.

The clipping you are getting is likely in the preamp.  You crank it up and it clips in the pre.

Have you actually looked at the waveform?  Does it clip in the converter?  It's not a digital overload as you describe because that's not possible on a recorded track...  you will clip in the converter, and you will get a clipped track but it will never go above "0" unless you amplify it internal to the DAW (does that make sense)?  Even then the DAW won't clip it if it's worth a hoot, it's got a lot of digital headroom due to having a 24-bit float or 32-bit datapath in the DAW so it's not clipping inside the DAW.

Anyway, my point is, it's probably the preamp.  With a very loud mic and lots of gain I can clip the input of my Delta 1010 and it sounds nasty, but it was flat out impossible to get clipping at the input of the Delta 1010 with my old console which had 60 dB of total gain.  With the PM-1000 modules I can get it to clip, but those modules have a hell of a lot more output than a cheap console.

The major flaw in sound/usability of my Behringer console was that with vocals and some other instruments the mic pre would clip, which is heard as 2nd harmonic distortion that can easily be identified on the sample if you look at it.  This is because there is only one gain stage and with a wideband signal with sustained sound (vocals, long, loud notes) the gain-bandwidth product is insufficient with the gain rung out in the preamp and it clips/overloads.  It's like the overload threshold is reduced temporarily due to thermal reasons or other things happening in the amplifier.  The PR8 probably uses an almost identical if not identical mic pre but with less total gain, which implies lower rail voltage or some other limit, meaning it will likely clip even sooner than the Behringer, and certainly have 20dB less output.

Turn the gain down on the channel until it doesn't clip, then you will need to apply more gain downstream somehow.  My Delta 1010 had a +4/-10 switch for each input and switching the output of the Behringer console to "+4" and the input of the 1010 to "-10" made it possible for me to use gain settings that didn't clip (often) but still get sufficient signal into the converter.  This is essentially a switchable 14 dB of extra gain in the front end of the converter.  

[John Ivan]

josh wrote on Thu, 13 May 2004 09:59

One of the big limitations of that SM Pro Audio PR8 is that it only has 40dB of gain. The clipping you are getting is likely in the preamp.  You crank it up and it clips in the pre. Have you actually looked at the waveform?  Does it clip in the converter?  It's not a digital overload as you describe because that's not possible on a recorded track...  you will clip in the converter, and you will get a clipped track but it will never go above "0" unless you amplify it internal to the DAW (does that make sense)?

Hi Josh;

I guess I don't understand what you mean here. I can very easily clip the wave forms in wave Lab while I'm mixing Through a Layla card. I can get the meters in Wave Lab to go "over" with no problem. Explain what you mean in more detail. I'd like to read it.

[dejacky]

Quote:

My Delta 1010 had a +4/-10 switch for each input and switching the output of the Behringer console to "+4" and the input of the 1010 to "-10" made it possible for me to use gain settings that didn't clip (often) but still get sufficient signal into the converter. This is essentially a switchable 14 dB of extra gain in the front end of the converter.

Correct me if I'm wrong, but if the preamp is swtiched to +4 output level and the A/D converter box is set to -10, wouldn't it clip-overload the converters easier since the preamp signal is hotter?  The SM ProAudio PR8 has -10 outputs, so I'm fairly sure I set my Multiface inputs to -10 level.  Should I change this or is it a bad idea to use mismatched levels between preamp and Digital input A/D?

[Family Hoof]

I think what josh is saying is that he didn't want to crank the preamps in his Behringer because they sound nasty so he was getting a low output from it. They aren't always spitting out +4dBu, only at high levels. By reducing his converter input to look for lower levels like -10 (probably around where his mic levels were peaking) he would make up for the loss. I do the same thing with my setup.

As for you Dejacky,
Condenser mics on drums often put out enough output so that the preamps do not need to be cranked at all, stay at 0 gain. Even at that setting, I've had similar problems with my converters being clipped. I'd recommend that you 1) buy or build some inline pads. -10dB should do. and/or 2) switch your converters to accept +4dB inputs. When recording at 24 bit you do not need to have your levels peaking. There's no S/N ratio to maximize so don't worry about seemingly low levels while tracking or raising your preamp gains to compensate. Instead, worry about getting good relative levels so that you only have to do one stage of digital gain later on to compensate.

[John Ivan]

Oh;; I see what he's saying now ,I think. If I'm getting overs while mixing in Wave Lab for instance, the meter is indicating an over in the converter,not the software? So if I look at the wave form and see that it is clipped, It will be because the converter clipped. It would also show squared of audio that was clipped at the pre amp but, This clipping is not a result of the soft ware going over digital zero. Do I understand this now? Thanks.

[josh]

ivan40 wrote on Fri, 14 May 2004 16:02

Oh;; I see what he's saying now ,I think. If I'm getting overs while mixing in Wave Lab for instance, the meter is indicating an over in the converter,not the software? So if I look at the wave form and see that it is clipped, It will be because the converter clipped. It would also show squared of audio that was clipped at the pre amp but, This clipping is not a result of the soft ware going over digital zero. Do I understand this now? Thanks.

Yes you're exactly right.

And when looking at the waveform, you can usually tell what is causing the clipping.  A "squared off" waveform was clipped in the converter (highly unlikely).  The sudden presence of 2nd or 3rd harmonic in the signal indicates clipping in some analog stage (probably the mic pre, or in the front end of the "converter", analog buffer/amplifier input).  You can see this if you have, say, a vocal note that is predominantly a sine wave that suddenly develops a "dip" in the crest of the wave so it goes rise, then fall a little, rise back up, then back to zero.  Make sense? The wave would look like this (maybe):

    /\/\   /    \  /      \          <---analog clipping+         \      /           \    /            \/\/    ___   /   \  /     \+        \      /  <---converter clipping (very unlikely)          \    /           \__/

What I was originally trying to point out is that it is nearly impossible for the RECORDED track to have digital clipping.  You would have to overload the front end of the actual converter chip directly without distorting first in the analog driver that's on the input of the converter system.  Your converters have a jack, probably a capacitor, then some kind of amplifier (dual op amp probably), then go into the converter.  Any clipping you hear from a freshly recorded track is in this analog stage ahead of the converter.  You'd have to ignore all kinds of audible distortion and really drive the hell out of it to get digital clipping on input, but you'd see it as a combination of harmonic distortion from the analog stage and flat-lining from the converter and it'd be nearly impossible to lay blame on one or the other.

Once the track has made it to disk, you can certainly crank it up to the level of overload of your converters, but this doesn't happen inside your DAW software, which in all liklihood uses 24-bit floating framework or 32-bit throughout, so there's all kinds of headroom on top of a 24-bit sample.  You could add tons of gain to a normalized sample and still not get the internals of the DAW to clip.  However, on output to the output converters, you can get it to clip because they have to output it at 24-bit (not 32-bit or floating).  You will not see this clipping in the waveform unless you export the track and then you will see it in your exported track.  You will hear it though!!!

My point was that the SM PR8 does not have enough headroom + gain to be able to overload the input of anything but maybe a SB16 card or a built-in laptop sound input... but certainly not a decent sound card or converter.  So if you're hearing clipping in a track you just recorded, it's a recording of clipping that happened in the mic pre...  the signal is clipped out of the mic pre.  An easy way to tell is to plug the output of the mic pre on the suspect channel directly into your headphone amp and begin to play, see if you can hear the clipping.  My guess is you can.

What I found with my Behringer console is that with a loud mic (like a LDC, in my case a Studio Projects B1), without a pad switch on the mic, regardless of the mic gain setting, the INPUT to the mic pre was clipping.  Since the mic pre just has one gain stage, it clips in that stage, which are bipolar transistors so they sound awful when clipping.  With other mics, if you crank the gain up too high, then it would clip in the mic pre, even though the thing was not outputting +4dBu.  So my technique was to use the +14dB of clean gain in the front end of my DAW to give me an extra 14dB of headroom in my Behringer console so I didn't have to crank its gain enough to induce any clipping at all.  Unfortunately this amplifies the noise.  But c'est la vie.  I guess in this case, it's a $200 console so it's hard to complain, same goes for a $100 8-channel mic pre.

[josh]

Family Hoof wrote on Fri, 14 May 2004 05:57

I think what josh is saying is that he didn't want to crank the preamps in his Behringer because they sound nasty so he was getting a low output from it. They aren't always spitting out +4dBu, only at high levels. By reducing his converter input to look for lower levels like -10 (probably around where his mic levels were peaking) he would make up for the loss. I do the same thing with my setup.

bingo, thanks for saying it better than I could.

Quote:

As for you Dejacky, Condenser mics on drums often put out enough output so that the preamps do not need to be cranked at all, stay at 0 gain. Even at that setting, I've had similar problems with my converters being clipped. I'd recommend that you 1) buy or build some inline pads. -10dB should do. and/or 2) switch your converters to accept +4dB inputs. When recording at 24 bit you do not need to have your levels peaking. There's no S/N ratio to maximize so don't worry about seemingly low levels while tracking or raising your preamp gains to compensate. Instead, worry about getting good relative levels so that you only have to do one stage of digital gain later on to compensate.

Yeah, but I bet the problem is at the other end.  Where he needs the -10dB attenuator is between the mic and the pre.  The clipping is not because the preamp is overdriving the converter (I'm assuming here, but it may be a safe assumption), but because the mic pre itself is clipping inside the gain stage, either because the input level is too hot (the old mack truck through a mouse hole thing) or because it's run out of headroom with the amount of gain he's trying to get to get a decent signal into the converter.

The reality is that the output of the SM PR8 says "-10dB" but I bet it can only peak to that level for short transients and anything really pushing the outputs to that level over any amount of time other than transient is going to clip or distort.  So what this means is that if you want to get a hot signal into your converters even set to -10, you may get clipping.  IMHO of course, but this was what I found with my similar Behringer console.  So you have to turn down the gain on the pre until it stops clipping and then accept the lower-level signal into the converter.

[John Ivan]

It's a good subject, Thanks for all the info. I understand the analog world pretty well for someone who is not a Tech but the digital world is quite new to me when it comes to looking under the hood.

Drums are loud AND fast. A snare drum can produce a ton of very fast high end and it takes a good pre to capture that well. Tambourines are another thing that can drive ya nuts. We recorded a tam, a while back at my buddies place with a LDC and a john Hardy and it was amazing how careful we had to be to not let the electronics in the mic  collapse. The pre distorted WAY before the light came on also. Strange indeed.Where do they sample the OVER LED on the John hardy pre's? the out put?

[dejacky]

Quote:

The pre distorted WAY before the light came on also. Strange indeed.

I found out this to be the case with my setup, but it would only distorted once the level was close to the led clip level..the led would just go from dim to bright depending on the overloading signal.

I switched my Multiface inputs to "low gain" settings (higher than -10, but lower than +4), giving a much "fuller" sound from the drumset since I can now turn up the preamp gain on all mics and for some reason it's not overloading the multiface inputs.  It ends up overloading at the preamp before it does the analog inputs of the multiface.  All in all, I seem to have more headroom on the recording inputs and I can take advantage of close-source recording instead of having to put mics far away from the source.

Several people suggested simply turning the gain down..and while I tried this, the recorded sound was "small" and "less spacious" and "sterile" (even after compression & effects) compared to turning the preamp gain up now and recording the mics closer to the source.  Now, I like the sound better, it just doesn't sound louder, but just more "musical."  Am I mad, or can any1 else confirm what I'm perceiving?  Thanks again!

[josh]

dejacky wrote on Sat, 15 May 2004 10:21

Several people suggested simply turning the gain down..and while I tried this, the recorded sound was "small" and "less spacious" and "sterile" (even after compression & effects) compared to turning the preamp gain up now and recording the mics closer to the source.  Now, I like the sound better, it just doesn't sound louder, but just more "musical."  Am I mad, or can any1 else confirm what I'm perceiving?  Thanks again!

Hard to say without looking at your setup and actually listening myself.  What it sounds like to me is you are getting enough gain to get some 2nd harmonic distortion and this to you sounds less "small" and "sterile".  Yes, you're clipping the preamp, and you like the sound (which is quite alright!).

IMHO "if it sounds good it is good".  So if you like it, rock on.

[dejacky]

I'm thinking of using my stedman pop filter in front of my AT3035 mic, in front of the kick drum mic hole?  Maybe this will allow me to use even more gain w/out clipping.  Has any1 used a pop filter with a kick drum mic b4?

[Family Hoof]

I have tried a pop filter but it doesn't help a lot. What solves the problem much more effectively is rotating the mic to point off axis so that the air is no long blowing directly at the mic's diaphragm. A good way to do this I found is to position the mic near the edge of the outside bassdrum head and aim at the center or the hole. Experiment with some headphones on and by putting your hand in front of the mic to feel where not a lot of air is going straight at it but where you still get a good sound.

[dejacky]

I like the sound best with the mic on axis  ...It captures more thump and less tiny "boing" sound.  I need some better isolation headphones than these direct sound extreme isolation headphones to make it easier for testing.  Thanks though