Noisy Output MOTU 896HD - DVR134 or That1646?

[creal]

Hi
My motu 896hd Main Output doesn't work properly .
The ouptut leveI was very low and noisy.
I replaced the mjn4580, the level looks louder but the signal is saturate.
I tried other OPA like NE5532 and tl072 without a good result.
So, I suspect the DV134s are damaged.
I don't have the DVR134s at home but i found 4 That1646.
The pinout looks be the same.
I like to know, if i can replace the DVR134 by a That1646?
Any advices are welcome

Cyril

 

[hymentoptera]

I know a guy doing pretty much the same thing to a MOTU 1224, and I know there's a THAT chip that's good in that model, but I don't remember which chip. Maybe search around for MOTU 1224 mods.

 

[LeeYoo]

I think the only difference is the input impedance.
10k for the DRV and 5k for the THAT.
So the answer is "it depends"
On the circuit that's driving the chip.
Leo..

 

[creal]

Hi
Thanks for these informations.
I found another post here
http://groupdiy.com/index.php?topic=19963.0
It looks the BB DRV134 line driver can be the cause of the noise and saturation.
I will order some DRV134 to my next order and see what's happening...
I'll post the result.

Cyril

 

[LeeYoo]

Easy to measure if the DRV is ok.
There has to be (almost) zero volts on the two outputs.
The outputs are direct coupled to the XLR/Jack outs, so you could also measure on the XLR socket.
The THAT 1646 should be a direct replacement... >if it's input is directly coupled to the output of opamp.
According to THAT, their chip does better at clipping level.
If you are worried about blowing this chip from accidently connecting it to a phantom powered preamp, install 4x1N4004 diodes from the outputs to the power rails.
As per diagram.
Leo..