Mixer project finally completed (DONE!)

geoff004 said:

What did I miss or leave out?

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First of all, very  nice build!!!!
I've used THAT 1243  and THAT 1203 line receivers in my mixer project. So far no problems when connecting something with transformers.
I had a (very quick) look at both data sheets (1510 and 1243) but could not find anything apart from the 1243 having a higher input impedance (1510 has 10K, 1243 has 21K). AFAIK these two are not pin compatible :-( otherwise you could have tried replacing the 1510 with a 1243.
Anyway, I think this is a impedance problem. The 1510 is designed as mic pre IC. I'm not good at this but the answer should lay somewhere in the 1510 data sheet I guess. Does the distortion change at various gain settings?

Your schematic does not show DC bias resistors connected from THAT1510 inputs to gnd.
Are they present in your actual circuit ? If not, that would explain the difference between connecting electronically balanced outputs (which may have resistors from output to gnd) and the transformer balanced outputs (which are floating).

As seen on THAT1510 datasheet:
http://www.thatcorp.com/datashts/1510data.pdf

Other than the connection to the protection diodes, the 1510/1512 input pins are connected only to the bases of their respective input devices. For proper operation, the bases must be provided a source of dc bias that will maintain the inputs within the IC’s input common-mode range.

Click to expand...

keefaz said:

Your schematic does not show DC bias resistors connected from THAT1510 inputs to gnd.
Are they present in your actual circuit ? If not, that would explain the difference between connecting electronically balanced outputs (which may have resistors from output to gnd) and the transformer balanced outputs (which are floating).

Click to expand...

Wow.
I think you're totally right.  I probably intended to follow the schematic more closely.  I think I even bought the resistors but forgot to solder them into the circuit.
Doh!
At least they should be easy to add on.
Thanks a ton - I'll add them and report my findings.

Fixed and working better than ever.
Thank you everyone for your help.

Finally got it all completed.  It's working really well for me.  I've already mixed a bunch of stuff on it.
Added a little graphics too.  The sharpie comes of real easy if I ever need to change anything.

keefaz said:

Your schematic does not show DC bias resistors connected from THAT1510 inputs to gnd.
Are they present in your actual circuit ? If not, that would explain the difference between connecting electronically balanced outputs (which may have resistors from output to gnd) and the transformer balanced outputs (which are floating).

As seen on THAT1510 datasheet:
http://www.thatcorp.com/datashts/1510data.pdf

Click to expand...

Lately I built a stereo mixing module exactly by this spec below, but with a 5532 I'm getting distortion when turning the "Gain trim" pot and the signal dims out. I've got an mp3-player coming straight to the L/R bus inputs and the L/R pre outputs go directly to fireface 800 inputs for routing. I also built sockets for a possibility to choose between two 2520 and the 5532 for comparison, in my case the ML2520 don't distort but the sound gets a lot darker and lower in volume.

Apologies for "hijacking" the subject, but I was thinking could I be having the same problem? Do I need to plug in resistors somewhere to get the plain master module working?


Image from http://sound.westhost.com/project30.htm
Probably we all diy-mixer fantasizers have seen that website/page before