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External pre-amps into MOTU 896
Posted: Wed Dec 20, 2017 11:38 am
by darrell
Hi all,
I asked this question several years ago, but since there are a lot of new faces on MOTUnation, I thought I would try for some more specific answers:
If an external pre-amp is chained between my microphone and the 896 channel input, does this 'disconnect' the internal pre-amp of the 896, so that only the sound of the external pre-amp is delivered to my Mac/Digital Performer? If not, is there a way of routing around the 896 pre-amps?
Thanks!
Darrell
Re: External pre-amps into MOTU 896
Posted: Thu Dec 21, 2017 6:46 am
by mikehalloran
Interfaces with combo input jacks bypass the mic pre when a 1/4” Line plug is inserted.
http://motu.com/products/motuaudio/896mk3/inputs.html
Re: External pre-amps into MOTU 896
Posted: Thu Dec 21, 2017 7:48 am
by darrell
Thanks Mike,
I didn't find the exact verbiage on the link you provided, but never mind that...
So, if I take a 3-pin cannon out of my Avalon pre, and go into any TRS (combo) channel input on the back of the 896, then that channel's preamp will be defeated, is that right? I do believe I can also go TRS out of the Avalon, but I prefer 3-pin.
BTW, I my 896 is a 'legacy' unit, and am assuming this same routing applies to it?
Thanks again!
Darrell
Re: External pre-amps into MOTU 896
Posted: Thu Dec 21, 2017 9:20 am
by HCMarkus
darrell wrote:Thanks Mike,
I didn't find the exact verbiage on the link you provided, but never mind that...
So, if I take a 3-pin cannon out of my Avalon pre, and go into any TRS (combo) channel input on the back of the 896, then that channel's preamp will be defeated, is that right? I do believe I can also go TRS out of the Avalon, but I prefer 3-pin.
BTW, I my 896 is a 'legacy' unit, and am assuming this same routing applies to it?
Thanks again!
Darrell
896 gain at 0. Try it. You'll like it.
Please note that properly wired XLR (Cannon) and TRS 1/4" will sound identical.
Re: External pre-amps into MOTU 896
Posted: Thu Dec 21, 2017 1:39 pm
by darrell
Thanks! I've always been suspicious of TRS, but need. I am free!
Re: External pre-amps into MOTU 896
Posted: Tue May 30, 2023 3:11 pm
by Zeno
Hello -
Revisiting this old topic. Did MOTU ever confirm that 1/4" bypasses the preamps?
The reason I question this is that MOTU recommends engaging the 20dB pad whenever a 1/4" is inserted with line-level signal. That made me think that maybe the preamp is always in the signal path, even with 1/4" inputs, and thus gives a potentially too hot signal for line level inputs.
From the 896mk3 Hybrid manual (p. 7):
"All eight inputs have preamps, so you can plug just about anything into them:
a microphone, a guitar, or a synth. If you plug in a +4 or-10 line level signal, use the quarter-inch jack and be sure to enable the -20 dB pad."
I also am curious since I just compared this MOTU 896mk3 Hybrid to a UA Apollo, both with same nominal gain/trim settings, and recorded various signals into a DAW: condenser mic, dynamic mic, mic through preamp into the line ins of the interfaces, synth into the line ins of the interfaces. In each case, the results in the DAW are anywhere from 10-20dB hotter from the MOTU in contrast to the UAD Apollo. Which makes me think the MOTU, even with the trim at zero, and whether using XLR or 1/4" inputs, is calibrated to add a larger default gain to inputs than the UA.
Any clarification appreciated.
Re: External pre-amps into MOTU 896
Posted: Wed May 31, 2023 2:36 am
by mikehalloran
Zeno wrote: ↑Tue May 30, 2023 3:11 pm
Hello -
Revisiting this old topic. Did MOTU ever confirm that 1/4" bypasses the preamps?
The reason I question this is that MOTU recommends engaging the 20dB pad whenever a 1/4" is inserted with line-level signal. That made me think that maybe the preamp is always in the signal path, even with 1/4" inputs, and thus gives a potentially too hot signal for line level inputs.
From the 896mk3 Hybrid manual (p. 7):
"All eight inputs have preamps, so you can plug just about anything into them:
a microphone, a guitar, or a synth. If you plug in a +4 or-10 line level signal, use the quarter-inch jack and be sure to enable the -20 dB pad."
I also am curious since I just compared this MOTU 896mk3 Hybrid to a UA Apollo, both with same nominal gain/trim settings, and recorded various signals into a DAW: condenser mic, dynamic mic, mic through preamp into the line ins of the interfaces, synth into the line ins of the interfaces. In each case, the results in the DAW are anywhere from 10-20dB hotter from the MOTU in contrast to the UAD Apollo. Which makes me think the MOTU, even with the trim at zero, and whether using XLR or 1/4" inputs, is calibrated to add a larger default gain to inputs than the UA.
Any clarification appreciated.
You are confusing Instrument Level with Line Level. They are not the same thing.
Re: External pre-amps into MOTU 896
Posted: Wed May 31, 2023 6:34 am
by Zeno
mikehalloran wrote: ↑Wed May 31, 2023 2:36 am
You are confusing Instrument Level with Line Level. They are not the same thing.
Thank you for the reply. Yes, perhaps it does seem confused, the way I wrote that. I understand those are different levels.
Nevertheless, my questions remain, so any thoughts on this are valuable:
- Has MOTU confirmed that the 1/4" input (whether TS or TRS, line-level or instrument-level) bypasses the preamp? The above referenced link to MOTU info does not seem to specify.
- Why would the MOTU show much hotter signal levels for the same input sources (whether external preamp, direct mic, or synth) relative to the UAD Apollo?
Any help on this much appreciated. Trying to figure out whether I have one of the units set oddly, whether one is defective, or whether this is just the nature of the different designs between MOTU and UAD.
Best regards.
Re: External pre-amps into MOTU 896
Posted: Wed May 31, 2023 8:20 am
by mikehalloran
The mic preamps are accessed through the XLR only in a CombiJack. It doesn’t matter who makes the gear.
Re: External pre-amps into MOTU 896
Posted: Wed May 31, 2023 8:41 am
by Zeno
mikehalloran wrote: ↑Wed May 31, 2023 8:20 am
The mic preamps are accessed through the XLR only in a CombiJack. It doesn’t matter who makes the gear.
That may indeed be so for the MOTU. That's what I am trying to confirm via some official word from MOTU; I didn't find this so far in the manuals or the MOTU site. I shall inquire directly with MOTU.
In contrast, the UA Apollo does allow the line 1/4" jacks of the combi jacks (or the equivalent line input on the DB25 jacks) to route through the preamp. Indeed, that is the default setting (see quote below). There is a preference where one may select whether each line input routes through the preamps or not. (The Apollo also has separate hi-Z inputs on the front).
From the Apollo Hardware manual (p. 30):
"¼” & DB25 Input Gain:
Line inputs 1 – 8 can be individually routed into the channel’s preamplifier for variable
gain adjustments, or the preamp circuitry can be completely bypassed for the purest
path directly into the A/D converter. This option is set with the LINE INPUT GAIN menu
in the Hardware panel within the Console Settings window. By default, line inputs 1 – 8
are routed into the preamp. When the preamps are bypassed, line inputs 1 – 8 operate at a fixed reference level
of +4 dBu. When routed into the preamps, gain for line inputs 1 – 8 is continuously
variable with up to 65 dB of available gain."
Re: External pre-amps into MOTU 896
Posted: Wed May 31, 2023 9:04 am
by EMRR
We’d need a schematic. Many many circuits are the same path for mic and line, just with some pad resistors for the line option. I think there are combi jacks that are normalled for both connections, and others that keep it separate. That may be a design choice based on how the connector is wired in, been awhile since I looked at the options.
Think about it this way - whatever is after a pre doesn’t need a buffer to the outside world, the pre is the buffer. No pre, need a buffer. There’s no less stuff in a line path, usually, not if you’re covering all the expected bases. Many products use the same circuit for both purposes.
Re: External pre-amps into MOTU 896
Posted: Wed May 31, 2023 9:16 am
by Zeno
EMRR wrote: ↑Wed May 31, 2023 9:04 am
We’d need a schematic. Many many circuits are the same path for mic and line, just with some pad resistors for the line option. I think there are combi jacks that are normalled for both connections, and others that keep it separate. That may be a design choice based on how the connector is wired in, been awhile since I looked at the options.
Think about it this way - whatever is after a pre doesn’t need a buffer to the outside world, the pre is the buffer. No pre, need a buffer. There’s no less stuff in a line path, usually, not if you’re covering all the expected bases. Many products use the same circuit for both purposes.
Thank you for the time and reply, EMRR.
Here's a schematic from the Apollo Hardware Manual. I couldn't find a schematic for the MOTU...If anyone has a link to one, please advise!
Re: External pre-amps into MOTU 896
Posted: Wed May 31, 2023 11:57 am
by EMRR
Looks like using the line switch position adds an extra amp stage over using it in pre position. Unless you’re using the pga path…. Block diagrams like this aren’t always truthful.
Re: External pre-amps into MOTU 896
Posted: Wed May 31, 2023 4:15 pm
by Zeno
EMRR wrote: ↑Wed May 31, 2023 11:57 am
Looks like using the line switch position adds an extra amp stage over using it in pre position. Unless you’re using the pga path…. Block diagrams like this aren’t always truthful.
Which gain stage do you mean? The PGA itself is the controllable gain knob (10-65dB) of the preamp, which always applies to mic signals, but by default also applies to the Line In signals. The PGA path is the upper path. So, if I read it correctly, it's the PGA path which adds the extra amp stage (i.e. the PGA), no? (Maybe the placement of the "PGA" label in the illustration is confusing; I take it to refer to the 10-65dB amplifier triangle).
Re: External pre-amps into MOTU 896
Posted: Wed May 31, 2023 4:17 pm
by Zeno
Just heard back from MOTU tech support (via on-line ticket):
1/4" into the combi jacks still goes through the preamp.
So it seems there is no way to bypass the preamp on these units.