Review this Layout of a simple 4 input mixer (please)

[Captainobvious99]

I created a layout of Jack Orman's 4 input mixer layout. Schematic here: http://www.muzique.com/schem/mixer.gif
I think I'll combine this with a small amp circuit to have an easily portable multi-input amplification solution.

I added potentiometers on the input resistors instead of the fixed 100K. Pins 1/5/8 on the IC are left floating in the schematic...is this correct ?

Other than that, does this look good to go ?  Thanks for taking a couple minutes to review a noobs work. 

Layout:

[Processaurus]

Hello, I don't think your individual level controls will work very well for you, because even though those resistors you're replacing with pots do vary the gain, by changing that resistance from 100K to 0, you can only get more level than unity gain for each channel, not less.  Even though there is a master volume, and you could turn everything down to get a channel quieter than unity, it's a... weird... way to do it (sorry).  Also, as you lower the 100K pot's resistance and increase the gain, you lower the input impedance until at 0 (max gain) you short out the input, because in the inverting amplifier configuration Jack's using, there is a "virtual ground" created at the inverting input to the opamp.

It would be better to use real voltage divider type volume controls right on the input of each channel, and then feed the wiper of each level pot to the corrosponding input on jack's complete circuit, (like the GGG mixer), or if you are plugging hi impedance sources like guitars straight in, a mixer like the one I threw together in my gallery, that buffers each signal before a level control.

Also  this layout's pinout is wrong on the opamp: http://focus.ti.com/lit/ds/symlink/tl071.pdf

[Captainobvious99]

Wow, after looking over the TL071 pinout its WAY off. 

I understand what you are saying about the volume controls. I suppose they wouldnt be of much use if you have a control on the instrument being used...

I like your design. So each input is using 3 pins off of the single TL074...what about pins 4 and 11? Are they left floating?
Also, can you explain the power supply/vref spots.
Is the input connected to the diode the NEG from the power supply,  while the +9v is then the POS? And what is the function then of the vref in this circuit?

Sorry for the beginner questions and thanks for taking the time to respond. I appreciate it !

[fixr1984]

A while back I had made a layout for this. It is verrified. Here is a thread that
has quite a bit of info that might help as well as a layout.