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Gear / Technical Help => Battery Boxes, Preamps, Mixers, ADCs, and Processors => Topic started by: OFOTD on October 30, 2007, 01:25:45 PM
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So gumbino and I are going to try to attempt a new V3 a/d comp. Here's how I see it going down.
Mics > V3 > recorder
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| (analog out)
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V3 > recorder
We'll be running analog out of the the first V3 into the XLR inputs of the second V3. Of the second V3 all we're planning on using is the a/d section. The pres of only the first V3 will be used.
Anyone hooked up two V3's like this before? Any thoughts? Things to beware of?
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Why? I guess I don't get what you're trying to compare.
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Why? I guess I don't get what you're trying to compare.
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Why? I guess I don't get what you're trying to compare.
ISO: Neumann AK20 x1
Mics: AKG 480/ck62/ck63 * Neumann KM100 x2/ak40 x3
Pres: Oade ACM Lunatec V3 * Oade m248
Cables: HiHo Silver Interconnects and XLR's
Recorders: Oade Warm Mod R4 Pro / D8 / D10Pro II
Im guessing the v3 listed above and a stock one......................
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Yes we are doing a comp of the A/D sections of the stock V3 and the ACM V3.
We'll be running a pair of 4023's into a stock V3. We'll then run the analog outs of the stock V3 into the analog inputs of the ACM V3. So we'll just be using the pre on the stock V3.
I thought about the built-in attenuators in the V3 but are they necessary since i'll be feeding it an analog signal from the stock V3?
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Ahhh, sorry I totally missed that.
good luck. their doesn't seem to be much out there on the ACM V3, what little their is seems positive though
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I think You're going to need to attenuate the signal before the 2nd V3, but I'm drawing a blank on the V3's input specs right now. I'd skip the attenuation bit and use a transformer isolated XLR splitter, instead:
/--- V31 (w/ phantom) > recorder
Mics > splitter >
\--- V32 (w/o phantom) > recorder
In either case, you'll have challenges matching levels precisely, so might as well remove the unnecessary gain structure / attenuation (gain > attenuation > gain) from the equation.
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I think You're going to need to attenuate the signal before the 2nd V3, but I'm drawing a blank on the V3's input specs right now. I'd skip the attenuation bit and use a transformer isolated XLR splitter, instead:
/--- V31 (w/ phantom) > recorder
Mics > splitter >
\--- V32 (w/o phantom) > recorder
In either case, you'll have challenges matching levels precisely, so might as well remove the unnecessary gain structure / attenuation (gain > attenuation > gain) from the equation.
I should have just come to you first Brian. :) +T
Then that begs the question does anyone have a transformer isolated XLR splitter I can borrow this weekend?
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Then that begs the question does anyone have a transformer isolated XLR splitter I can borrow this weekend?
I've always used XLR splitter cables, not isolated. They work fine, but are not ideal. Keep meaning to pick up a proper splitter box, but haven't gotten around to it. If you can't find a loaner, Guitar Center has a transformer isolated splitter box for $35/ea (http://). So...options:
- loaner TI splitter box (good luck!)
- pick up two of the Guitar Center boxes (and return them the next day?) :P
- pick up plain old cable splitters
- I can send you my cable splitters (though after shipping both ways, the new ones probably aren't hugely more expensive)
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Gonna go out on a limb and suggest that any $35 splitter box is going to have really mediocre transformers... but it'd be great if that wasn't the case.
Since you are using the same pre-amp in both cases, I would be less worried about using a passive splitter than if you were running two different pre-amps (this assumes the oade v3 mod is just on the a/d section, as has been suggested).
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here's a couple of thoughts...
Brian's comments are spot on. There is no way to NOT run the signal through the pre-amp of the V3 and only use the A/D (i.e. if you went V3 > analog > ACM V3, even if you use the internal attenuators and got the levels right, you'd still be passing the signal through the second V3's pre-amp).
That said, it seems like the best way is as Brian described, using some sort of splitter. As far as level matching between the two units, other threads have described the ACM V3 as being more sensitive, i.e. a lower input level results in 0dBfs relative to a stock V3. Based on that, you should get everything set up before hand, and then set the gain on the two V3's to be identical. for example, 20dB and all the trim knobs at 0dB. Then take both recorded files to a computer, and look at the overall level. Whatever the difference in levels between the two files is equal to the difference in sensitivity between the units. Now you know the difference between them, so you can adjust accordingly in the field, i.e. if you find a 10dB difference in those recordings, at the show, you can adjust the stock V3 exactly 10dB higher. with this method, you should be able to get the final levels very close, and thus have a better comparison...
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Gonna go out on a limb and suggest that any $35 splitter box is going to have really mediocre transformers... but it'd be great if that wasn't the case.
Ahhh...good point. :-\
Any handy TSer want to contribute some time building a quality transformer isolated splitter box (2 > 4) we can pass around as necessary? I'll chip in some cash for parts and such.
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Why does it need to be transformer isolated? That WILL change the sonic characteristics of the signal passing through it.
I think for a test like this you truly want a parallel passive split - you just want to be careful about applying phantom from only one side...
The only way it would be equal would be to have a 3 way split with both the isolated sides running to the preamps, but then you'd still need a third device to supply the phantom power.
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I've never done this, but I was always under the assumption that you could run phantom power on both units. I have absolutely nothing to base this on, I just thought this was what I've read. I feel like Marc Nutter posted some stuff about this a long while back while testing different pre-amps.
I could've sworn he ran mics->standard xlr splitter->2 preamps both with phantom power.
Obviously I'm not gonna try this with the u89i's first, but I have considered doing it.
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I'm not sure about the single vs. dual phantom source.
I've done splitter comps with both pre-amps sending phantom. One time I had problems with distorted bass and I was pretty sure that I forgot to enable phantom on one of the pre-amps. So my tendency is to enable both phantom sources.
I kinda wonder if the single-phantom case suffers from additional load due to the second pre?
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Were those comps done with parallel splits or isolated splits?
A transformer isolated split does not normally pass phantom power, so it wouldn't matter if phantom were engaged on both decks in this case.
In a parallel situation it could cause pops and other line problems.
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here is a comp by marc nutter and chapper a while back. trying to find some more detailed notes:
http://taperssection.com/index.php/topic,25769.0.html
http://taperssection.com/index.php/topic,25719.msg322067.html#msg322067
marc's notes: http://taperssection.com/index.php/topic,19485.msg322179.html#msg322179
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It was just a passive splitter... never noticed any problems when running with both phantom sources on.
But such is the complexity of good comps... Ideally you eval the sound of the one rig and compare it to the dual rig config as a control before comparing the different gear..
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I've never done this, but I was always under the assumption that you could run phantom power on both units.
I've run most of my comps using a simple XLR-splitter with phantom engaged on one preamp or both. Both options worked fine to my ears with the gear I was using. Doesn't mean it's an ideal solution (due to load, impedance, I don't know what else b/c I'm not techie-enough), but it's definitely workable. And while different phantom power implementations may have an impact on the sound of the unit, in this case we're talking about 2 V3s, so I wouldn't expect significant differences in sound due to different implementations of phantom.
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what i would do is rally another v3 (i have one i'd spare for this), and go:
_V3 #2 (oade mod, attenuated)
/
v3 #1 (preamp and analog out)>--
\_v3 #3 (stock, attenuated)
doug acm'd one of my v3's, and i promised him i'd get some comps up, but have never had the ability to... until now....
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I think that would be a pretty good config for the comp.... I'd just add a digiout from that front-end v3 as a control for the other two and to confound any know-it-alls out there ;)
How about not running attenuation on the pair of comp v3's. And if attenuation must be used, run it on the front end v3 (which would be run at min gain, 10)?