Help needed to convert balanced passive mixer with LCR switch to pan pots

Hi there,

I know that this subject comes up again and again but I need some guide and help figuring this conversion  ;D

I use a simplified mixer with 16 channels made with modified channel strips (preamp and EQ with THAT 1646 output) feeding NYD balanced passive mixer.
It has worked very well for years, but it the L-C-R is quite limitating... This arrangement is quite lossy (40dB)



I have re-read posts about it (10 years old with lots of pix missing) and I'm quite confusing.
What's the best ? Using the orban pan pot with dual pots ? but in this case wouldn't it be even more lossy ? And what would be the best resistors value considering what is driving the pan and also considering  my mixing network resistor's value ?

-I have also found back a "strange" implement made by NYD (I suppose...) but I have no idea of its performance or drawbacks, it also use a dual pot, but the wiper aren't connected to ground contrary to Orban implement....



-and last but not least another implement with quad pot that I found on a old usb memory stick without value...Don't know where it comes from...The filename suggest that it is "lossless". Quad pots are not easy to find (I found some in China.....)



Any help or suggestions are welcome.

The problem with passive mixing is it is always rather lossy and tends to need multi-ganged pots. Adding pan simply adds to the losses. The loss in itself is not a problem as it can be made up with gain - the problem is the noise from the amplifier making up the gain and the more loss you have the more gain you need so the more noise you get.

NY Dave's pan pot is a very clever way of achieving a passive balanced pan with only two pots but it is lossy.

The most obvious solution is to move from balanced passive to balanced virtual earth mixing and thereby include the gain make up amplifier with the mixer.

Cheers

Ian

Thanks for your answer Ian,

If I understand well, this topology :





                                                                                                +








This mixing network will work but at the expense of 40dB + 14.6 dB of loss=total of 54.6 dB, right ?
I use a Crane Song Spider as a make-up gain mic preamp. That preamp is very quiet and has 66dB of gain available.

That is essentially correct. As I mentioned before noise is the issue. Even a perfect mic preamp with 54dB of gain will have an output noise level of about -76dBu when fed from a 200 ohm source.  If your nominal operating level is +4dBu then your signal to noise ratio will be about 80dB.

Cheers

Ian

thanks for your answer Ian  ;D

flaheu said:

thanks for your answer Ian  ;D

Click to expand...

My pleasure. Just to put what I said into context, I was not trying to say that passive mixing is therefore bad. The noise problems arise by choosing to have the passive mixing present a suitable low source impedance so that you can use an external mic pre as gain make up. In other words, it is the choice of the gain make up amplifier that resulted in a noise issue. Within a mixer, provided you ensure the driving source impedance is low (to minimise crosstalk) then you can use any bus impedance you like - there is no need to slug the bus as in all the standard balanced passive mixer designs. This usually means the bus loss is much less than 40dB and the noise is consequently better,.

Cheers

Ian

Thanks,

I see the culprits, I will try.

Cheers