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RME User Forum → FireWire & USB series → proper way to usa an external preamp with babyface
hi
i would like to use a focusrite isa one with my babyface. I would like to know how to use properly the line in. i just need to turn off the gain trimmer?
Thanks in advance
hi! i also had that question in my mind,
the right way to do is like you say! just turn the gain down all the way, and be shure that phantom is off. Im not shure if its true true line signal, but it sounds great, at least when i use my GA pre73 pre-amp.
thanks for your reply fije!
I'm curious about this too. Can anyone from RME confirm this? Is turning the gain all the way down equivalent to a line-level input? Are the Babyface preamps completely disabled?
The Babyface pre-amps are never out of circuit, however the chip used has a special provision for 0dB gain setting which basically converts the circuit to a unity gain buffer. Make sure that the input gain in the control panel is set to 0dB.
Note carefully that pre-amps like the ISA-One or the GA73 are capable of outputs much higher than +20dBu, but even at 0dB gain the maximum input signal the BabyFace can handle is +12dBu.
A lots of these external preamp units get their sound from being driven hard. For the pre-amps named, you might find that a 10dB or 15dB pad between the preamp output and the BabyFace input works better. Make you own (very simple - I can give guidance) or if you are not into construction, try these:
http://store.shure.com/store/shure/en_U … .104210500
panatrope, nice thanks. what is the audible difference when not using this pad thing?
i would like to still say , just turning down the gain on the babyface, makes my pre73 sound great. if its gain on babyface, there is hiss and buzz and game over sound. so set gain at Zero !
panatrope, nice thanks. what is the audible difference when not using this pad thing?
i would like to still say , just turning down the gain on the BabyFace, makes my pre73 sound great. if its gain on babyface, there is hiss and buzz and game over sound. so set gain at Zero !
The only difference will be the difference in sound from when the preamp output is driven harder. The pad does not change the sound, but makes it easier to avoid overloading the input stage of the BabyFace.
I also have a pre73, which is a very useful unit for the price. Mine has some low-level (-70dB) 50Hz and harmonics from the power supply which are still there even with the gain and output level controls turned right down. Running the output 20dB lower into the BabyFace would effectively increase their level to about -50dB. So the pad would help to avoid this if your pre73 has the same behaviour.
Otherwise, if it sounds OK to you then don't worry.
panatrope,
actually i am noticing an electricity hum, same as yours. but only when i record silence (not playing) and listening back to this, through my genelec 8020.
i have output 70% of babyface, then a nano patch volume control, sen genelec set at 30 % maybe.
i i turn the nano patch at full volume, then that humming is there. its not there when i use babyface pre-amps.
i also have problems to hear it if i listen through my standard hi-fi setup. then i bounce the file, and put a mint-tele in macbook pros sound jack. then i dont here it.
do you think it could be a problem in my babyface-pre73-nanopatch-genelec setup?
i have tried to put all the audio and electricity cables seperated for each other.
RME, what do you say ?
all the best
fije
With the setup you described, then with the GA73 directly connected to the BabyFace, with the GA73 output level set at minimum, BabyFace input gain set at 0 and the Nanopatch at full, then with no signal and a quiet room you will most likely hear the output hum from the GA73. But it will not be noticeable with normal music levels present, and a normal setting on the speakers NanoPatch (mine usually runs at around -15 - -20).
By the way, a NanoPatch can also be used as the input attenuator between the GA73 and the BabyFace input - set it around 15dB to start with. (You will need an adapter from TRS out to XLR in but these are widely available.) This also gives you a lot of flexibility in choosing how hard you drive the GA73. The NanoPatch is a purely passive device and therefore does not change the signal other than in level. And however much input attenuation you use effectively lowers the level of the residual hum by the same amount.
Very nice posting panatrope, thanks!
Actually when i put my GApre 73, to my motu 8pre with TRS jack (which i dont if it can handle line level, cant find an answer... any help?) , i set the gain to zero, then there is a buzz/hum/hiss sound still. If i then use the -20dB pad on the motu, that noise goes away and the its very clean sound. Note now when i hear this sound, i have the nano on full and there is no music, just sound. My ears would be dead if i listened to music to this level. Is this -20dB pad on the motu, the same procedure as you describe?
i analyzed the hum when going pre73-babyface, its around 50-100-150-200 hz, most 250 hz. If i put a small EQ band right there, i might be able to take it away?
Checked other forums now, some recommend to move the power supply away from my other gear. right now its under my desktop.
all the best
The Babyface pre-amps are never out of circuit, however the chip used has a special provision for 0dB gain setting which basically converts the circuit to a unity gain buffer. Make sure that the input gain in the control panel is set to 0dB.
Hello Panatrope,
a question: Do you mean with "0dB Gain Setting" the minimum gain setting? 0dB is relative and thus I'm not sure...
As far as I know all digitally controlled mic/line preamps have more stages of gaining. Thus you never have the full noise of a "classic" analogue mic preamp that has just one gain stage and thus you have quite a lot noise.
Does Unity Gain Buffer mean that the signal is not run through the gain stage of the mic/line preamp?
Thank you for your help in advance,
Hermann
Hello Panatrope,
a question: Do you mean with "0dB Gain Setting" the minimum gain setting? 0dB is relative and thus I'm not sure...Does Unity Gain Buffer mean that the signal is not run through the gain stage of the mic/line preamp?
The device used has a provision to digitally control its gain between 9 - 60dB (in 3dB steps), plus it has a separate control to set the gain to 0dB (that is, a voltage gain of 1 or unity gain, which means the output voltage is the same as the input). This gives it the ability to handle "line level" signals with the lowest level of distortion.
But as I said before, the whole of the amplifier chain always remains in circuit. If you wish to understand it better, if you search on line for the data sheet for the device which is a Texas Instruments PGA2505, you will find in there a simple diagram showing the signal path.
RME User Forum → FireWire & USB series → proper way to usa an external preamp with babyface
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