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RME User Forum → MADI/AES Premium Line → ADI-8 pro and asymetrical input
Hi!
I felt I had too much gain at the input of my ADI-8 pro. I use preamps with asymetrical outputs...
I read in the ADI-8 pro user guide that "servos" automatically detect asymetrical input and rise the level by 6dB!!!
Why? Don't need these 6dB since my preamp's outputs are asymetrical! Is there any way to desactivate this "servo detection?"
Thanks.
No, that is the behaviour of the outputs. Unbalanced the ADI-8 can handle near +20 dBu at its input, which is the limit when using 30 Volt power supply.
I'm just quoting the RME official manual:
"The electronic input stage is built in a servo balanced design which handles monaural and stereo jacks correctly. When used unbalanced it automatically corrects the gain by 6dB."
Out of my studer 169 (which has asymetrical output), with a dynamic microphone, and preamp to minimum, I get overloads, even in low gain.
Maybe I misunderstand the sentence above, but I thought that this 6dB correction (totally inapropriate in this case) was causing these overloads at the input of the converters...
Up! Please...
I can not imagine how this combination of "dynamic microphone, and preamp to minimum" could produce a signal loud enough to overload the inputs, even with an added 6 dB... Is the ADI connected to the Stereo Master output?
Regards
Daniel Fuchs
RME
Ok, I confess, that's on a kick drum with high level output dynamic mike.
And no, this signal is taken from the insert out of the console, wich is asymetrical.
I just don't want the ADI-8 to add 6 dB. First, because I'm easily overloading the inputs (I have to use an attenuator in this case), secondly because I love my preamp's color and prefer the working of my preamps (which are made for it) to the gain of ADI 8.
So do you confirm that there's, in this case, a gain of 6dB? And is there a way to avoid it?
Thanks
There is no way to change the circuits behaviour. Just add two resistors as passive attenuation externally and the problem is fixed.
Could you use a TRS plug into the ADI, but only connect the T/S at the Preamp? Basicaly leave "Pin3/Ring" open (not shunted to ground) at the ADI to "trick" it into operating w/o the +6dB gain boost? Or will this have a noise penalty or otherwise affect the ADI's balanced input reciever's performance?
Actually I think I'm already in this configuration? I use TRS Jacks to link my preamp's insert (tip->send, ring->return, sleeve->ground) so ring and sleeves aren't linked. But that doesn't seem to "trick" the ADI...
By the way, I think servos detect "asymetrical" inputs not by measuring the tension between ring and sleeve, but by comparing signal on tip and eventual ring...
Can a RME specialist explain the way servos detect asymetrical or symetrical signal?
You use a 1/4" TRS plug in an INSERT PORT on your mixer to feed the ADI-8's 1/4" TRS inputs? Are you plugging the 1/4" TRS all the way in on the mixer's insert?
I was actually talking about using a special cable where one end was TRS (at the ADI-8 input), and the other was TS (at the mixer insert - plugged into the 1st "click" to get the Direct Out w/o breaking the Insert's "normal" to the rest of the Mixer's channel strip), and the Ring/Pin3 is left unconnected. AFAIK, the balanced input reciever looks for a short from Ring (inverted polarity input) to Sleeve (ground) to determine whether to compensate +6dB for a "Single Ended" unbalanced input - but I might be very wrong :-)
Yes I use a TRS on both side. I plug it all the way into my mixer.
Thus, I have no shorts between ring and sleeve since one is grounded and the other is connected to the insert return (which I don't use as a return of course). So in this configuration, if servos detect the balanced/unbalanced by looking for short between ring and sleeve, I would "trick" the ADI-8. That doesn't seem to work...
Hmmm - If you are plugging all the way into an "Insert" - you are basically connecting the ADI's "Ring" to your Mixer's "Return" (input connected to input). I'm not sure if that would have any negative effect (likely noise) on the ADI or on the "single ended" detection and associated gain (it obviously renders the rest of your Mixer's chanel strip un-useable since you are "breaking" the insert's "Normal", correct?). I'd probably be more comfortable using a TS to TS plug, and only plugging into the "1st click" on the Insert - this will prevent you from presenting anything to the ADI's Ring input, and will allow you to use the rest of your mixer's channel strip if desired for monitoring, EQ, Aux Sends, etc.
Beyond that - I'm not sure how the ADI's +6dB of gain is activated for single-ended inputs - I figured it was only when a direct short was detected from Ring to Sleeve at the ADI's inputs (indicating a TS jack is plugged in as the Shield and Ring are shorted via the TS Jack's Shield connection). I'd figure my "Special Cable" suggestion would work - but RME will need to confirm what triggers the +6B of gain on the Balanced Input Receiver chips they use...
As a test - you can try using a plain TS > TS cable (a guitar cable will work) and see if you observe +6dB more gain than you do now. If so, then you are not getting the added gain with your TRS cables (as I suspect might be the case by my assumptions above).
RME User Forum → MADI/AES Premium Line → ADI-8 pro and asymetrical input
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