Topic: Microtrack + AD-20 combo question

[yousef]

Not sure whether to post this here or the pre-/ADC board...

I recently bought a Microtrack to replace my ageing D8 but I've been a little underwhelmed with the results thus far.

This is mainly, I think, to do with the quality of the on-board pre and ADC but there is also the issue of the MT's inability to deal with even moderately hot signals. For instance, earlier this week I used my DPA 4060s directly into the TRS inputs and even on the "L" setting and lowest record level I wasn't happy with how high the signal was - peaking right at the far right of the meter and occasionally flashing the red clip lights. And this wasn't a particularly loud gig. (And, yes, this is with the +27dB boost turned off and with the most recent firmware installed).

Anyhow, I'm currently in the process of buying an AD-20 through the yard sale, in the hope that this might improve matters. But I'm a little concerned about the minimum of +17dB gain that this unit supplies - more than enough to have me clipping non-stop, based on this week's experience.

So, a couple of questions - 1) if I'm going digi-in from AD-20 to the MT, does this added gain matter and 2) if it does, can anyone give me some pointers as to how to construct at 3.5mm minijack to 2x XLR lead that will give adequate attenuation between my mics and the AD-20?

As ever, any help or words of advice are much appreciated,

Yousef

[Todd R]

Well, a few things here:

1) the added gain of the AD-20 doesn't matter.  The AD-20 puts out a digital signal, so at that point the maximum analog signal the MT can take without clipping doesn't matter.  All that will matter is the maximum analog signal the AD20 can take.

2) I looked up the specs on the AD-20.  It can take a maximum input of -5dbu before clipping (gain at minimum -- 17db).  The MT can take a +3.8dbu input, so the MT can actually take an approx. 9dbu louder signal on it's analog input than the AD-20.  So if you were having problems clipping on the MT, you'll really be having problems clipping on the AD20

3)  I really don't understand why you are clipping on the MT.  Like I said, the MT can take a +3.8dbu max signal.  The 4060's from their specs have a sensitivity of 20mv/Pa.  So the 4060's won't get up to the clipping point of the MT until they get a sound pressure level of 130db -- which is really, really, really loud.  I doubt even with your head right in the stacks of a ear-splitting concert you'd get more than 125db.  Which makes me wonder -- do you have some sort of preamp in your setup?  Like a DPA MMA600?  If you just have a battery box, the clipping on the MT doesn't make sense to me.

[yousef]

Thanks for the considered and illuminating reply.

I'm only using a 9v battery box (ie no pre) but I think part of the problem is that although the Microtrack is meant to be able to accept a +3.8dB signal, some (mine included) can't. There is some discussion about this here: http://taperssection.com/index.php/topic,81722

On Monday I taped Nouvelle Vague (vox, acoustic gt, double bass, keys, drums; not terribly loud) with the 4060s>battery box>TRS inputs on MT. Even with everything set on minimum, the red clip lights were lighting up fairly regularly. I know these come on a few dBs before clipping and, happily, there was no clipping in evidence on the actual recording but it makes me wonder about what might happen at a louder gig.

But if I go digital in to the MT, I should be OK? My only worry is that I know some people have swapped 4060s for 4061s because of the mics overloading at loud gigs - something that shouldn't happen to a 4060 below 130dB. So maybe I'll need a little attenuation before the AD-20 anyway.

Thanks again for the reply - you've cleared a lot up for me.