[sdiy] OT: Audio line levels

[Michael Ruberto]

Thank you Peter, and happy holidays to you!

What I am have having to contend with is the choice between using the 
floating transformer isolated inputs or the +4 unbalanced recieve inputs. 
This is a real dinosaur:

http://i108.photobucket.com/albums/n13/somnium7/gear/ToaBoard01.jpg
http://www.toaelectronics.com/disc/manuals/RX-7-164_248_328_IM.pdf

According to the specs I have a fairly large amount of channel headroom 
(clipping at 12.3V-24dB) and there are 3 levels of padding for the tranny 
inputs (-20, -40, -60).
Do you think I will have decent performance if I use the transformer inputs 
and ground the cold pin at the instrument output?
Or will I absolutely need a DI box?


In the past I've connected -10 outputs to +4 inputs on effects boxes and 
sometimes it was very noisy and other times it didn't seem to make a 
difference.

Overall this installation will be quite a challenge with all these signals 
levels. The synths are all -10, the effects and preamps are -10, +4 
unbalanced and +4 balanced, and the sampler has a combination of +4 balanced 
and -10 outputs. Also I've never actually been exposed to gear with floating 
transformer inputs.

M. A. Ruberto

>From: Peter Blackett <dragon.servicing at virgin.net>
>To: Michael Ruberto <frankentron at hotmail.com>
>CC: synth-diy at dropmix.xs4all.nl
>Subject: Re: [sdiy] OT: Audio line levels
>Date: Sun, 08 Apr 2007 18:46:16 +0100
>
>Hi,
>I think that some active Di boxes don't provide electrical isolation 
>between the input and output (the feed to the desk). this can be a problem 
>if you are trying to get rid of earth loops.
>are the gains on the input channels on the  new mixer adjustable ? as it 
>might be able to cope with the - 10 signal levels without being too noisy. 
>Otherwise I think it would be possible to make up an amplifier to increase 
>the signal level.
>I think there may be a kit avaiable to do this, but I can't remember where 
>I saw the details.....
>Happy Holidays
>regards Peter
>
>
>Michael Ruberto wrote:
>
>>Soon I will be picking up my new mixer. Problem here is that I just found 
>>out all of it's inputs are unbalanced +4 level. So I have to find or 
>>preferably build a level shifter that can accomodate the 20+ outputs of 
>>all my -10 output synths and sampler. I imagine buying something to do 
>>this will cost a hefty sum for this
>
>>Also I am curious about Active Direct Inject boxes. Anybody use them? Are 
>>they better/worse than passive?
>>
>>M. A. Ruberto
>
>

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