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Sent Pre Through Line instead of Mic = WOW!
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noah330
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#1
12th November 2010
Old 12th November 2010
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Sent Pre Through Line instead of Mic = WOW!

I have all external pres for my DM-3200.

I have a UA-610 (the rack one). When I moved about 4 and a half years ago I hooked up all my stuff and for some reason I ran the 610 into the XLR in of my mixer.

I forgot about this until last week and ordered the stuff to make a new cable.

Used it in a session for the first time tonight - man what a difference!

If you're running your pres into your xlrs then change them to the line.
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#2
12th November 2010
Old 12th November 2010
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Quote:
Originally Posted by noah330 View Post
I have all external pres for my DM-3200.

I have a UA-610 (the rack one). When I moved about 4 and a half years ago I hooked up all my stuff and for some reason I ran the 610 into the XLR in of my mixer.

I forgot about this until last week and ordered the stuff to make a new cable.

Used it in a session for the first time tonight - man what a difference!

If you're running your pres into your xlrs then change them to the line.

Always!
#3
12th November 2010
Old 12th November 2010
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#4
12th November 2010
Old 12th November 2010
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yes it helps a lot if you don't run the mics through a good pre-amp then an alright pre-amp. It also helps if you dont add mic gain to a line signal.

How about 'always read the instruction manual' as better advice!
#5
13th November 2010
Old 13th November 2010
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Wow...
RLD
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13th November 2010
Old 13th November 2010
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Hey, that's alright Noah...
You learn from your mistakes...and others do too.
#7
13th November 2010
Old 13th November 2010
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good post. someone will read this and know not to do this. nothing wrong with good information, however obvious some might make it out to be.

why waste a on a thread post when there are people who need information on things that others will scoff at?
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#8
13th November 2010
Old 13th November 2010
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Now I'm confused.

Don't most XLR mic inputs run at 0db gain when turned all the way down?

And on most budget mixers isn't the signal being fed to the line inputs simply padded and sent to the same gain stage as the XLR mic pre inputs? At least, that's what the schematic in my Onyx manual looks like.

So if that's the case, as long as you're careful with the gain what should there be a difference? If anything, avoiding the padded line input should in theory provide a cleaner signal path, right?

I must be missing something. Is there somehow a headroom issue?

OK, never mind, there is a difference - from the Onyx manual: max input level for the mic inputs is +21 dBu @ unity gain whereas the line inputs are +30dBu @ -20 dB.

Still, I think I might be inclined to use the mic input @ 0db unless I absolutely needed that extra 9 dB of headroom. Or am I still missing something?
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#9
13th November 2010
Old 13th November 2010
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Originally Posted by southsounder View Post
Or am I still missing something?
yes... you are missing something.

Preamp LINE OUT goes into LINE IN. Not into another preamp input. Big difference. C'mon guys this is band/DJ/engineering/home stereo 101
#10
13th November 2010
Old 13th November 2010
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I think you might have missed the whole point of my post.

Check the schematics of any budget mixer. On the mono channel inputs the "mic input' and the "line input" use the same gain stage. The difference is the connector and a resistor or two being used as a pad.

The reason there is a difference in gain between the two inputs at the same gain control setting is the line input is padded.

If you're functionally using 0 dB gain in either case, there should be no theoretical difference - except possibly that the resistors being used to pad the line inputs may affect the tone slightly via loading, as they do in most other circuits I'm familiar with.

That's why I was wondering if using the XLR "mic" inputs might actually provide a cleaner signal path, provided you didn't need the last little bit of headroom the padded line input provides.

Using proper gain staging was a given.
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#11
13th November 2010
Old 13th November 2010
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most mixers (at least not cheap ones) will have a PROPER line input that BYPASSES the gain stage of the mic pre.


the whole point is to not run your line level signal into something not looking for a line level signal, and to avoid the extra circuitry/unnecessary gain stage. Nothing really about headroom, it kinda just depends if you want your signal to sound good or not
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#12
13th November 2010
Old 13th November 2010
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No argument - on a proper mixer with switchable inputs then the line input is of course preferable.

That being said, I would wager that a significant percentage of the mixers owned by users on this particular forum are of the design I was referring to. For them, using the XLR inputs might actually be the cleanest signal path - even though it seems counter intuitive. That's all I was trying to point out.
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13th November 2010
Old 13th November 2010
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in your scenario with that sort of mixer, then yes, i would agree as well, the pad would just introduce unneeded circuitry into the signal flow.

it looks like the person who started this thread, his mixer had an appropriate line input, or i would be surprised that he heard that much of a difference
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13th November 2010
Old 13th November 2010
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Quote:
Originally Posted by southsounder View Post
No argument - on a proper mixer with switchable inputs then the line input is of course preferable.

That being said, I would wager that a significant percentage of the mixers owned by users on this particular forum are of the design I was referring to. For them, using the XLR inputs might actually be the cleanest signal path - even though it seems counter intuitive. That's all I was trying to point out.
actually, on that type of mixer, the cleanest signal would be the aux in, assuming there is one. That, followed by going directly to the onboard pres if there's no other way to bypass them.

However, if you have a much nicer outboard pre, wouldn't it be best to pad down the gain and use the better outboard gear?
#15
13th November 2010
Old 13th November 2010
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Surprisingly, while the DM-3200 does have an actual line/mic switch, both inputs feed a single gain stage as previously described (actually two gain stages in series). The manual doesn't specify the minimum amount of gain the preamp provides, so if it's > 0dB then that might have been the problem.

As far as using the aux input, it depends on what he's trying to do with the signal. The DM-3200 has crazy complicated routing, so I won't even try to guess, but on regular analog boards the channel inputs have direct outputs whereas the aux inputs feed the main and/or alt buses only.

If the OP was using the DM-3200 as A/D conversion for tracking, then he was likely using the digital version of the channel direct out so the aux inputs wouldn't really work. Looking at the schematics of the DM-3200 shows that the cleanest path would actually be the channel insert returns - they bypass one of the two channel gain stages, unlike either the mic or line inputs.

And in this case I don't think it's a question of using the outboard vs. the onboard pres - he's already using the outboard pres. The question is what's the cleanest path to get the signal from the outboard pre into (presumably) a channel input to send to the DAW. Adding a pad (aka resistor) and any stage will affect the signal to a certain degree. Chris had it right - avoiding any unnecessary circuitry is the key.
#16
13th November 2010
Old 13th November 2010
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+1 on using the ring of the insert returns. I found this useful tweak on the Tascam forum as I own a dm-3200. While it's not horrible to run an outboard pre into the line you are indeed using the circuitry of the pre, therefore adding that color to your signal. You will hear and like the sonic diff of using the insert return point which bypasses the line/mic circuit. You can verify this by studying the Schematic in the manual.

Too bad the Tascam doesn't have separate send and return jacks that are balanced, but this is still the better way. One more note; since you no longer have trim before the fader, you will have to do that at your pre and/or comp (if in the chain) output so you don't overload coming in. You will have fader at the 3200 going out from there to your DAW or whatever. Very easy to adjust to.
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Last edited by Mr. Wilson; 14th November 2010 at 02:18 AM.. Reason: Typo
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13th November 2010
Old 13th November 2010
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Quote:
Originally Posted by therealbigd View Post


yes it helps a lot if you don't run the mics through a good pre-amp then an alright pre-amp. It also helps if you dont add mic gain to a line signal.

How about 'always read the instruction manual' as better advice!
That's a simple mistake a lot of people make, no big deal right? Hey, I admit I made the same mistake for quite some time and you're right...not adding mic gain to a line signal makes all the difference in the world. Boom, the noise floor drops considerably and your world gets all happy.
#18
13th November 2010
Old 13th November 2010
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Translation of the above: It depends upon your equipment.

Choices are: connect your outboard preamp,
a. Direct to your digital converter,
b. To your unamplified Line In,
c. To your Stereo Line In,
d. To your channels Aux Return (if it has one),
e. To your Mic in (with the gain dialed way down),
f. To your amplified line in,
g. I am not sure about the board's Aux Return.

It also depends upon whether you are using that pre for silent gain, or for effects. Generally, it is best to get your gain as close to the source as possible, additional gain stages amplify the noise from the preceding stages along with the signal.

I do think, that this being the Low End forum, that a lot of the readers do have Low End gear. I certainly do.

My mixer is also one of those where the Line In is merely padded 20db down. I seem to get the best signal to noise ration and headroom with about 90% of the gain coming at the outboard pre, and 10% from the mixer's Mic pre.
#19
13th November 2010
Old 13th November 2010
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I have a Tascam US-1641 and it's only got 4 line ins. I have my go-to preamps hooked up to the line-ins, but I also have a Ramsa console and use the channel strips on that for when I setup a bunch of mics (drum kit, full band, etc). I have no choice but to run the outs of the board into the mic pre inputs of the US-1641. I keep the gain all the way down on the Tascam and have no problems, and it sounds fine. Optimal? No. But like many, I'm working with I got, and I make it work...I'd dare say I even make it work well.
#20
13th November 2010
Old 13th November 2010
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Quote:
Originally Posted by noah330 View Post
I have all external pres for my DM-3200.

I have a UA-610 (the rack one). When I moved about 4 and a half years ago I hooked up all my stuff and for some reason I ran the 610 into the XLR in of my mixer.

I forgot about this until last week and ordered the stuff to make a new cable.

Used it in a session for the first time tonight - man what a difference!

If you're running your pres into your xlrs then change them to the line.
Surprise!


Gear does have a way of working better when it's set up the way it's designed to be used.

That said, it should be remembered that many boards use XLRs for mic and line. Sometimes they're separate inputs and sometimes a single XLR serves both paths and they're switched or simply variably padded.

Quote:
Originally Posted by RLD View Post
Hey, that's alright Noah...
You learn from your mistakes...and others do too.
We all make them from time to time. Most of us probably hide them most of the time.

It can take a
big guy to let others learn from his mistakes.
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#21
13th November 2010
Old 13th November 2010
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Hey, not to futher come in and say that what you are doing was wrong, because there is no right and wrong, but there is more than just gain to be concerned with when selecting an input to connect gear to.

There is also the matter of impedance. Connecting the preamp's line out to the mic input, is going to load the heck outta the preamp's output...the outboard one in this case. This outboard preamp is going to have to deliver into impedance that is reduced compared to what it is designed for, loading the output circuitry of the outboard preamp.

The line in of the DM3200 has an input impedance of 10k. The mic in is 2k.

For line, this is lower than some, and could be higher. Most converters for example are in the ballpark of 20k or so nowadays.

In short, screwing with the impedance can really screw your sound up, and it's NOT just about padding the gain down.

If you want it to sound nasty, and are trying to make it sound "screwy" then sure, experiment all you want. Mix and match "Z' all day long.

If not, observe proper impedance matching, bridging etc.

Again, engineering 101. Sorry.
j
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#22
13th November 2010
Old 13th November 2010
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Mic through mic can be a beautiful thing.... depends what's going in....




Quote:
Originally Posted by noah330 View Post
I have all external pres for my DM-3200.

I have a UA-610 (the rack one). When I moved about 4 and a half years ago I hooked up all my stuff and for some reason I ran the 610 into the XLR in of my mixer.

I forgot about this until last week and ordered the stuff to make a new cable.

Used it in a session for the first time tonight - man what a difference!

If you're running your pres into your xlrs then change them to the line.
#23
13th November 2010
Old 13th November 2010
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Noah, on behalf of all the human beings i'd like to apologise for this thread, glad you improved your mic sound
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#24
13th November 2010
Old 13th November 2010
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Quote:
Originally Posted by NEWTON IN ORBIT View Post
Hey, not to futher come in and say that what you are doing was wrong, because there is no right and wrong, but there is more than just gain to be concerned with when selecting an input to connect gear to.

There is also the matter of impedance. Connecting the preamp's line out to the mic input, is going to load the heck outta the preamp's output...the outboard one in this case. This outboard preamp is going to have to deliver into impedance that is reduced compared to what it is designed for, loading the output circuitry of the outboard preamp.

The line in of the DM3200 has an input impedance of 10k. The mic in is 2k.

For line, this is lower than some, and could be higher. Most converters for example are in the ballpark of 20k or so nowadays.

In short, screwing with the impedance can really screw your sound up, and it's NOT just about padding the gain down.

If you want it to sound nasty, and are trying to make it sound "screwy" then sure, experiment all you want. Mix and match "Z' all day long.

If not, observe proper impedance matching, bridging etc.

Again, engineering 101. Sorry.
j
#25
14th November 2010
Old 14th November 2010
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Sigh. This actually isn't engineering 101, more like electronics 101. Your statements regarding loading are unfortunately not correct in this instance.

Note that the output impedance of the 610 pre is only 60 ohms.

If the DM-3200's XLR in's input impedance is 2k ohms that's still well more than 10x the source impedance, which is the minimum recommended ratio for bridging impedance, which in turn is the principle most modern audio devices are designed around. It will work and sound just fine.

The recommended minimum input impedance the 610's output wants to see is listed as 600 ohms, for this exact reason.

Loading occurs when the input impedance is lower than the source impedance, which is not the case here.
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#26
14th November 2010
Old 14th November 2010
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Well sorry, I did not realize it was as low as that. It is greater than 10x yes.

However, that statement is not all true with respect to what I said in my post either.

I merely was saying that it would load the output circuitry more than if it was in the line input, which has a far greater input impedance. No?

I suppose it would work running it into the mic in, but the OP clearly notices a subjectively "better" sound. I am sticking to my theory on this one. Unloading the output of the outboard preamp is clearly helping the sound, and my guess is this because the amp was maybe either overshooting, ringing, or the output transformer (if there is one) was doing the same.

Besides..the input doesn't have to be lower than the source impedance to be "loading" the output circuitry and making the amp misbehave. Ten times or more is better, but it doesn't mean that it wouldn't work even better further "unloaded" feeding a 20k input.

You are saying the input could be just twice the output impedance, and there wouldn't be any loading?

Also, are you certain on the industry designs line ins around 2k input impedance?

This seems very low to me for a line input.

Why is that a Neve 8816 for example, has an input impedance of 20k then? Are they just an esoteric odd man out? This seems typical to me, as this seems to be about average for most converters and line inputs.

I think you misunderstand my post, or maybe I wasn't clear?

Loading is a term I have most often seen used as in "How much is the input "loading the output of that amplifier". As in what "load" is that amp being asked to drive?

There was a time when electronics 101 was considered art of being an audio engineer FWIW. Sorry if I came away looking like a jackass know it all...I am certainly not ...at least not a know it all :0)

I am no expert by any means, but I know enough to get by. When I get in over my head, I ask people who know much more than I do...

Impedance bridging - Wikipedia, the free encyclopedia
#27
14th November 2010
Old 14th November 2010
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Hey, I just looked at the manual for the 610. Yes the output inpedance is 60ohm.

The recommended MINIMUM load is 600 ohms, and to me, this would be pretty low, and apparently this is what they are thinking is getting bottom of the acceptable range. Maybe from back in the day when everything was designed to drive 600 ohms.

If you notice, even the line input on the 610 itself is 13.8k. Much higher than 600 ohms. Much higher than your industry design standard of 2k.

Are you sure you don't mean standard for mic preamp input impedance?

This would seem more "standard" to me.

J
#28
14th November 2010
Old 14th November 2010
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Yes, I was referring to the XLR mic input of the DM-3200, and actually I got that 2k impedance figure from your earlier post. The Onyx XLR input's are 2.4k so I figured it was in the ballpark.

My point was simply that as long as the input impedance on both the inputs of the DM-3200 are over 10x the output impedance of the 610, which they are, then there should be full voltage transfer and no loading using either input. The resistors padding the line level input would therefore be unnecessary in this instance and merely represent additional circuitry which could be avoided by using the XLR inputs - unless headroom is an issue.

The only reason I brought all this up was to refute the misconception that there was some sort of magic difference between the "mic" and "line" inputs on most budget mixers and that sending a line level signal into a "mic" input was a bonehead blunder and which would somehow automatically "trash" the signal regardless of circumstances.

People were kind of harshing on the OP for doing this, and I was just trying to point out that his choice of input may not have been the actual problem. Rather, my guess was that it was really a gain staging issue. That, or the 610 has a crazy hot output and the extra headroom of the line input was needed.

In general though, mic inputs on most budget mixers can accept line inputs without signal degradation, as counter-intuitive as it might be.
#29
14th November 2010
Old 14th November 2010
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Need to forget all that extra smart stuff and use the equipment as it was designed to be used. Line out to Line In.
#30
14th November 2010
Old 14th November 2010
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Quote:
Originally Posted by work2do View Post
Need to forget all that extra smart stuff and use the equipment as it was designed to be used. Line out to Line In.

Thank you. Sorry. I am not trying to be "extra smart". In fact, I think I am pretty "extra below average". That said, use whatever works for you, but I agree. Use line out to line in.

These words you posted are pure wisdom.

I'm out,
Peace,
j
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