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Post new topic How to Bypass Pre Amps?
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Author Topic:  How to Bypass Pre Amps?
James Quillian


From:
San Antonio, Texas, USA
Post Posted 11 Feb 2018 4:49 pm     Reply with quote

I should already know this but I don't.

With USB recording interfaces, does running a separate through line in normally bypass the pre amps provided by the device?
The device I am using now is an Alesis i04.

I have other pre amps that a sound a lot better than anything I have found in a USB interface.
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Tony Prior


From:
Charlotte NC..
Post Posted 12 Feb 2018 3:13 am     Reply with quote

The Alesis is a 4 in/4 out USB INTERFACE with preamps built in. It does not appear that you can bypass the preamps section while still maintaining the DAW I/O INTERFACE. At least not on this particular model.

You can still use your external preamps in front of the Alesis , just run the Alesis preamp knobs FLAT. Play with the knobs ( tones) on the external preamp until you find what sounds pretty good !

Probably the biggest issue you will deal with is LEVELS, from your external preamp thru the ALESIS preamp.

Experiment, see what happens !
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Jack Stoner


From:
Inverness, Fl
Post Posted 12 Feb 2018 3:25 am     Reply with quote

Some devices let you bypass the built in preamps and others do not. I had a Roland Octa-Capture and those couldn't be bypassed. I now have an MOTU 896Mk3 Hybrid and if a TRS connection is used instead of XLR then the internal preamps are bypassed. Then there are other recording interface units that do not have built in preamps and you must use external pre-amps.

The io4 is a very basic unit and I wouldn't expect the preamps to be great. My first recording interface was an Alesis io26 and it didn't last long before I got a "real" interface unit (a Focusrite Saffire Pro 40).
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James Quillian


From:
San Antonio, Texas, USA
Post Posted 12 Feb 2018 4:40 pm     Reply with quote

The best system I have ever used is an M-Audio Delta 66. It just had a break out box that accepted the signal from an external pre amp. It worked great with xp but I have never been able to use it a lot with windows 7 and above.

It would be great if there was something like that usb based. Oddly, the I04 does o.k. with steel and other instruments. Vocals are the problem and as a singer I am bad enough without any issues.

I appreciate you guys answering my questions.
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Tony Prior


From:
Charlotte NC..
Post Posted 13 Feb 2018 8:46 am     Reply with quote

James Quillian wrote:
The best system I have ever used is an M-Audio Delta 66. It just had a break out box that accepted the signal from an external pre amp. It worked great with xp but I have never been able to use it a lot with windows 7 and above.

It would be great if there was something like that usb based. Oddly, the I04 does o.k. with steel and other instruments. Vocals are the problem and as a singer I am bad enough without any issues.

I appreciate you guys answering my questions.


Why not ? I use the Delta 66 with WIN 7, it loaded just fine, the only thing that did not load was the stand alone Control Panel program which allows some features to be altered outside of the DAW. Make sure you don't have a conflict with another audio device with Win 7.

Download and install the latest MAudio Delta driver for the 66. I Use it with Pro Tools 12 . No issues. It was on my XP system previously.
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Bill Terry


From:
Bastrop, TX
Post Posted 13 Feb 2018 12:59 pm     Reply with quote

I bought one of these a quite few years ago, lost it in a house fire, bought another, and now they seem to be out of production.. No preamps, nowhere.. Smile

Great converters IMO...


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James Quillian


From:
San Antonio, Texas, USA
Post Posted 13 Feb 2018 1:55 pm     Reply with quote

Tony Prior wrote:
James Quillian wrote:
The best system I have ever used is an M-Audio Delta 66. It just had a break out box that accepted the signal from an external pre amp. It worked great with xp but I have never been able to use it a lot with windows 7 and above.

It would be great if there was something like that usb based. Oddly, the I04 does o.k. with steel and other instruments. Vocals are the problem and as a singer I am bad enough without any issues.

I appreciate you guys answering my questions.


Why not ? I use the Delta 66 with WIN 7, it loaded just fine, the only thing that did not load was the stand alone Control Panel program which allows some features to be altered outside of the DAW. Make sure you don't have a conflict with another audio device with Win 7.

Download and install the latest MAudio Delta driver for the 66. I Use it with Pro Tools 12 . No issues. It was on my XP system previously.


I am going to try it again.
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James Quillian


From:
San Antonio, Texas, USA
Post Posted 13 Feb 2018 2:09 pm     Reply with quote

With respect to the Delta 66, is the cable that runs from the sound card to the breakout box just a certain size cable or is it unique to the Delta 66?
If it is something that can just be bought? If so, is there a description that describes its size, number of pins etc.

I actually have two Delta 66 sound cards but just one cable.
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Tony Prior


From:
Charlotte NC..
Post Posted 14 Feb 2018 1:22 am     Reply with quote

James Quillian wrote:
With respect to the Delta 66, is the cable that runs from the sound card to the breakout box just a certain size cable or is it unique to the Delta 66?
If it is something that can just be bought? If so, is there a description that describes its size, number of pins etc.

I actually have two Delta 66 sound cards but just one cable.


James I believe it's a proprietary cable. It's specific to the Delta 66 which is 4 in 4 out analog and then the two additional digital in/outs . I have never heard of an aftermarket break out cable.
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werner althaus


From:
lincoln, NE
Post Posted 16 Feb 2018 8:07 pm     Reply with quote

I don't understand what the problem is, of course you can use an external pre-amp, that's what the line level 1/4" jack is for. It will bypass the mic-pre and match impedance better. The specs unfortunately don't tell us what the maximum input level is, so you might need a pad on the pres' output if you want to push the pre-amp but the answer to your question is clearly Yes"
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Tony Prior


From:
Charlotte NC..
Post Posted 18 Feb 2018 5:10 am     Reply with quote

werner, not on this model. It's a reasonably low cost combo, interface/preamp. The 1/4 Instrument/Line does not disable the preamps. And we don't want it to, otherwise the user would have a useless tool in front of them if they did not own another preamp . They would use one input or the other and then have no preamp.


Are you saying that some preamps disable the preamp stage when someone uses the 1/4 input ? Line/ VS Instrument ?

I'm not talking about a BYPASS switch.

Alesis states that on this model you can connect EXT devices via the 1/4 or the Inserts but basically brags that they are all compatible with the on board preamps.

The op knows he can use another preamp, thats not the question.
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werner althaus


From:
lincoln, NE
Post Posted 18 Feb 2018 9:29 pm     Reply with quote

Tony Prior wrote:
werner, not on this model. It's a reasonably low cost combo, interface/preamp. The 1/4 Instrument/Line does not disable the preamps. And we don't want it to, otherwise the user would have a useless tool in front of them if they did not own another preamp . They would use one input or the other and then have no preamp.


Are you saying that some preamps disable the preamp stage when someone uses the 1/4 input ? Line/ VS Instrument ?

I'm not talking about a BYPASS switch.

Alesis states that on this model you can connect EXT devices via the 1/4 or the Inserts but basically brags that they are all compatible with the on board preamps.



The op knows he can use another preamp, thats not the question.




Unfortunately I can't find a schematic for this model but I wouldn't automatically assume that a cheap interface can't do this. My 4 channel lexicon Omega from 12 years ago cost next to nothing yet has 2 mic pres and 4 line amplifiers. The line in on it does not pass through the mic pre.
Do we know that the line input switch on the Alesis inserts a pad or is it possible it re-routes the signal straight to the second stage (the line amp). How much total gain is on tap and is it from one stage or two stages of amplification?

But the more important question is whether "bypassing" a mic-pre and running it into an equaly cheap line amp vs running into a mic-pre with pad, set to the correct impedance and to unity gain will make much of a difference.

IMO the important thing is that the impedance is right and that you can't accidentally put phantom power on unbalanced output devices like keyboards or micpres with insufficient protection against DC voltages (yes, they do exist)
Meeting these criteria qualifies for "bypassing the micpre" IMO unless
"Bypassing the micpre" is some quest for tonal purity. In that case, don't bother with a budget interface to begin with. YMMV

BTW, the $250,000 console I spend a lot of my time on has a mic/line amplifier, everything runs through it, line, mic and High Z, so what?
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Tony Prior


From:
Charlotte NC..
Post Posted 19 Feb 2018 1:29 am     Reply with quote

werner, I hear ya, but comparing a NEW era Interface/Preamp to one made a decade ago is probably not a fair comparison.

Users of this particular INTERFACE/PREAMP combo are stating that the preamps cannot be bypassed. Many new era COMBO's units are limited. remember this is not just a preamp but a USB DAW Interface as well, 2 for 1.

On top of this, the users are stating that the INSERT inputs are noisy as all get go .

Regarding BUDGET interfaces, good luck with that, the entire world is now chock full of low cost combo units, Interface / Preamp. Many of them come with a scaled down DAW. These are starter packages and are flying off the shelves. Much has changed in the last 5 years let alone the last decade.
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werner althaus


From:
lincoln, NE
Post Posted 19 Feb 2018 7:52 am     Reply with quote

There seems to be a lot of contradictory info on the web regarding which interfaces allow for the mic pre to truly be bypassed (as in removing it from the circuit in its entirety). Claims are made regarding the MOTU 896Mk3 Hybrid in this thread (and elsewhere, some folks cite conversations with the manufacturer to bolster their claim) yet one look at the manual states "For line level quarter-inch inputs, turn on the pad." (the same pad that Motu uses for all the inputsources, line, mic and Hi-Z) and schematics can't be found. I recall similar confusion regarding the Saffire 40. makes me wonder what the customer service folks at MOTU/ Focusrite etc. mean when they say "line input bypasses mic pre"? Maybe all that it means is that the impedance is higher and that phantom power is disconnected on the 1/4" line input. I'm not claiming to know the answer and find the issue to be a lot of fuss about nothing. My guess is that the OP doesn't want redundancy in his signal chain (running a mic pre into a mic pre= bad gainstaging) and that makes sense but IMO the higher impedance/ no DC on the 1/4" line input addresses the more important issue. Maybe it'd help to just think of the Alesis analog input as a Mic/ Line amplifier.
Anyway, it's all good, if you only want a line amp between the outboard pre and the ADC, there are plenty of cheap interfaces with 4 analog in (2 mic/ 2 line), but I would not be surprised if the diff is negligible. It would be a great experiment to record the same external mic pre to 2 channels, one on a mic/line combojack @ unity gain and one on a pure line in, then do the null-test (invert the hopefull gainmatched and samplelocked tracks) to hear the difference if there is any.
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David Mitchell


From:
Texas, USA
Post Posted 14 Mar 2018 3:51 am     Reply with quote

I bought the Audient id14 two channel interface but if you buy this 8 channel unit you get all the features you can imagine in an interface. It allows you to go direct to computer but has an insert point on each of the 8 channels that let's you bypass the mic pre's if you want to use external preamps but keep using the converters. You can also use that insert point to patch in compressors or reverbs.
I think this unit sells for about $1300.00
It has 8 class A discrete mic preamps, hi gain instrument inputs and line inputs as well. It's high end gear that feels high end in use. The pots are smooth and stepped gain. I use to use 24 channels of Delta PCI 1010lt cards with mixing consoles but I am an Audient man now.

https://youtu.be/2knx1rPyq0I
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Brett Lanier


From:
Vermont
Post Posted 14 Mar 2018 8:38 am     Reply with quote

Is this what you have? I haven't read all the back and forths on this thread but it looks like you have a 1/4" line in right there under (and to the left of) the xlr input. Probably best to use a balanced cable going from your preamp. XLR --> 1/4" TRS, or 1/4" TRS on both ends.

A lot of the modern interfaces have selectable mic vs line inputs via the software that's used to run it. The Apogee duet works that way as well the Metric Halo interface I have.

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Michael McGee


From:
Everton, Missouri, USA
Post Posted 8 Apr 2018 3:45 pm     Reply with quote

I can certainly relate to discussions and disagreements about this issue on the internet. It is a great question.

I am using a focusrite 18i20 gen1. I run a dedicated mic preamp into inputs 1 and 2 via TRS cables. I can turn the gain knobs down completely on the 18i20, set those inputs to instrument, and I am able to get an acceptable and reasonable amount of gain into my DAW with adjustments made on the mic preamp. To my ears, it sound fine.

But is it a true bypass? Are the focusrite inputs adding additional "color" to the signal? Some say yes... some say no. Can my ears hear a difference? (I don't THINK SO... lol!).

Great discussion! Love this forum.
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