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need to convert signal from +4 to -10 (x 16 channels)

 
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nag hammadi
gettin' sounds


Joined: 18 Jul 2010
Posts: 136

PostPosted: Tue Aug 16, 2016 11:03 am    Post subject: need to convert signal from +4 to -10 (x 16 channels) Reply with quote

hi folks. i do a lot of on location live recording, and have started incorporating some tape machines into the rig. i know it sounds silly, but i think it is cool and so do a lot of bands, so there has been a pretty good call for it in my neck of the woods.

at any rate, the 16 tracks machines i am currently using for this are a pair of foster e16's that run at -10.

everything i have runs at +4, as do all of the consoles at the venues i regularly get called to.

when i bring my midas, i can just roll back the gain and get by (though that sort of neuters the pre), but i can't have the FOH engineer do that obviously.

which brings me to an interface. most interfaces i see are 2 channels, or 4 channels and hundreds of dollars.

i can definitely solder, and i would imagine this is one of those times where DIY will be the only affordable solution.

is anyone aware of an affordable alternative? or does anyone want to point me towards a diy solution?


i am actively trying to find a tascam ms-16 or something similar that runs at +4 to just be done with the whole thing, but i have gigs now, and need to get with it.

any help or nods in the right direction would be much appreciated.
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Jim Williams
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Joined: 03 Jun 2006
Posts: 1132
Location: beautiful Carlsbad, CA

PostPosted: Tue Aug 16, 2016 11:47 am    Post subject: Re: need to convert signal from +4 to -10 (x 16 channels) Reply with quote

Easy fix. Wire a 2.2k resistor is series with the signal, follow that with a 1 k resistor to ground, that will attenuate the signal about -12 db, the difference between +4 dbu and -10 dbV.

Those parts can easily fit inside an XLR connector.
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Jim Williams
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nag hammadi
gettin' sounds


Joined: 18 Jul 2010
Posts: 136

PostPosted: Tue Aug 16, 2016 12:55 pm    Post subject: Re: need to convert signal from +4 to -10 (x 16 channels) Reply with quote

perfect! thanks Jim, as always a gem...

forgive my stoooopid, but let me make sure i have it.

assume i will repurpose a patch bay to do this {i have a lot of them laying around).

the rca inputs on the tape machine are obviously unbalanced. i would insert the 2.2k resistor between the tip connections of the in and the out, then connect the 1k between the sleeve of the in and out?
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nag hammadi
gettin' sounds


Joined: 18 Jul 2010
Posts: 136

PostPosted: Tue Aug 16, 2016 1:31 pm    Post subject: Re: need to convert signal from +4 to -10 (x 16 channels) Reply with quote

better yet, i bet i can do it in the barrel of my 1/4" snake, right? essentially just put the 2.2k in series between the tip of the 1/4" plug and the wire, and the 1k between the sleeve and the ground wire?

or does the 2.2k go from hot to hot,and the 1k from hot (before the 2.2k) to ground?
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