Behringer ADA8000 pre bypass questions

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asm

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im trying to figure out how to get past these pre's in my ada8000, and i need some help!


kev provided me with this info, but im a bit unclear, on jakobs schematic it appears that the AD convertors are the tl074 chips, while in the al1101.pdf located below, it says ITS the AD convertor. which one is it? there are only 4 al1101 chips, but 8 tl074's, there are alos 4 al1201 (i think thats the right number) so im guessing thats the sister DA convertor chip.

http://www.gyraf.dk/schematics/Behringer_ada8000_analouge.PDF


http://www.profusionplc.com/static/images/data%20sheets/al1101.pdf


he said that it shouldnt be a problem to inject unbal into the tl074, but me being a moderate noob, and not wanting to mess anything up i'm double checking.
as in inject a hot pre'd signal DIRECTLY to the leg of the chip?

these frickin chips are so small and ive never soldered chips this small or board mount resistors and caps. how much do i have to worry about frying the chip by overheating?


thanks for any help. i really hope i can get this to work. i need alot of ch of AD but i cant go out and pay 1500$ for 2ch of apogee or anything else right now :?


thanks.
taylor
 

synthi

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Hi asm,

The AD converter chip is the AL1101 and the DA is the AL1201. You`ll need some voltage protection if you want to go directly into the AL1101 chip, it has been discussed in the main B* ADA8000 post.

Best Regards,

Synthi.
 

asm

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voltage regulation in what means? opamp, step down transformer, cap, ?

what kind of voltage regulator follows their built in pre's?

thanks for the help.

t
 

synthi

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Overvoltage protection, not voltage regulation!

You could fry the chip if you put very hot signals directly to the input pins for the AD chip. Check the original post, I think someone sugested using diodes. Sorry I`m not an expert, ask in the old post.

Synthi
 

asm

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gotcha...

but why is it a mystery. theres a built in pre right before the AD chip allready in there, and the schematic of it is simple...

all i see before it is some 22u caps, and some diodes in the pre path.

:?
 

rafafredd

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Have a look at the other thread about the AD8000... You probably need the opamps in there to drive the AD converter chip.
 

asm

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i'll check it out...


but out of stupidity, im not getting it here.... there allready was a pre in the signal path right before it..... so (here comes the ignorant part) cant you just follow the same path right before the chip to inject the external pre? just like the built in pre is entering the chip.

:?
 

Flatpicker

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You have to step-down the voltage a great deal going from line level to A/D converter inputs. A great solution for this, albeit an expensive one, is to use a transformer. Jensen has info at their site.
 

synthi

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asm:

I think I cans ee your point.
Well, think that you can`t get the signal from the pre at the point where it feeds the AD, the pre don`t feed the AD at line levels, right? So you can`t feed that point with a line level coming from other gear. its not a stand alone pre with line level feeding a AD, the micpre is also adjusting the signal for the AD chip inputs.

Synthi.
 

asm

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[quote author="Flatpicker"]You have to step-down the voltage a great deal going from line level to A/D converter inputs. A great solution for this, albeit an expensive one, is to use a transformer. Jensen has info at their site.[/quote]

how expensive?

and i'd need a transformer per channel right?

what are the other options?

thanks.
 

Flatpicker

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[quote author="asm"]...how expensive?...what are the other options?...[/quote]Depends on where you get transformers. Jensen?s are $70 - $100 each.

Here?s some examples from Jensen:
http://www.jensen-transformers.com/as/as006.pdf
http://www.jensen-transformers.com/as/as043.pdf
http://www.jensen-transformers.com/as/as062.pdf

You will have to do some digging for this one. Call Jensen and other transformer companies like Cinemag, Lundahl (K&K Audio), etc., give them the converter part #?s and see what they recommend.
 

Mbira

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Maybe a better way would be to check out the pres that are being used now and decide how bad they are and if there's anything that could make them better? If they aren't "really" a full preamp (IE they're not getting the signal all the way up to line-level) then maybe they aren't f^&king with the signal too much at that stage?

I'm real curious to see how this plays out as I've been planning on getting one of these very soon as well.

Joel
 

asm

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thats an idea, but i think one guy said he tried running the built in pre's all the way at 0, and they still clipped when running the other pres thru them.
 

synthi

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the XLR (mic input) have 10 to 60dB, so minimun is 10dB, not Zero... Using the Jack (line input) is the way to go when coming from other pres.

Synthi
 

synthi

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yes, the line input goes thru a PAD then into mic pre. I`m just advice you to use the line input for avoid clipping when using external preamps.

Synthi

i think one guy said he tried running the built in pre's all the way at 0, and they still clipped when running the other pres thru them
 
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