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Gear / Technical Help => Battery Boxes, Preamps, Mixers, ADCs, and Processors => Topic started by: jerryfreak on July 05, 2015, 03:33:24 PM

Title: does this waveform look wierd to you (tinybox>ad2k)
Post by: jerryfreak on July 05, 2015, 03:33:24 PM

from last night, nbobs>tinybox (high gain)>ad2k at +24 db input level>digi in>pmd661 . was peaking at 12 db, i though i was ok but it appears im brickwalling/limiiting somewhere

(http://i.imgur.com/H3fq47V.png)

close up

(http://i.imgur.com/OEr5JdF.png)

Title: Re: does this waveform look wierd to you (tinybox>ad2k)
Post by: jerryfreak on July 05, 2015, 04:19:08 PM

ah that makes sense. was in my bag and wasnt even watching. are all TB's the same max input level?  i have 2

the one i bought from you in sept 2013, where i requested both LNA + headphone amp and you had some design compromises with that combo so i ended up with:

"I built your box with standard gain (4/16/30) as the headphone amplifier was unstable at 40dB gain with maximum load and volume using the Nbox input. "
 
and:

"I used a new intermediate amp in this unit as it was more stable than the low noise amp.  Noise performance is in between; -122dBV (unweighted) EIN vs. -125dBV for the low-noise amp and -115dBV for the standard amp.  Its noise floor will be lower than the CMR or Nbox microphones.  It also uses 1/3 the current of the low-noise amp and only twice that of the standard amp, so runtimes will be longer than with the low-noise amp. "


I also own ghomenghasts which was built more recently:

http://taperssection.com/index.php?topic=172272

i dont have specs on this new one but i assume its an off-the shelf unit? it has a 3 way toggle for power (high (up)/off(center)/low(down)). my old TB only has off and on in that switch. whats the difference? my pinout on my old unit is:

"6-pin input pinout: 1 +8V 2 R+ (CMR) 3 L+ (CMR) 4 +54V 5 R-&16V (Nbox) 6 L-&16V (Nbox) chassis gnd"

wanna make sure i dont cook my CMRs by accidentally sending high voltage to them, though i think cabling takes care of that. I have no idea of how ghormenghast's pinout is, only that it works with nbobs as is

thanks

Title: Re: does this waveform look wierd to you (tinybox>ad2k)
Post by: jerryfreak on July 05, 2015, 04:43:51 PM

ok so if you say the TB clips at +13dBu, i should be running the ad2k input level at +14dBu to match the levels, so 0dB on the ad2k is within a dB or so of the tinybox's clip point

and 'mid' gain (+18dB) would be best in this case

Title: Re: does this waveform look wierd to you (tinybox>ad2k)
Post by: harmon712 on August 18, 2015, 08:45:12 PM

I've only used the high gain setting on mine once for a quiet show at a bar. I have nowhere to post the recording since they're not on LMA.