My Mackie 808s will only play in Mono. Does anyone know what the problem is and if it can be fixed?

Take the main outputs into a stereo input (or a pair of mono inputs) on the Peavey - without knowing which Peavey I cannot tell you further info re set-up but as you'll be sending line level signal you'll need to back off the gain on the channels you input to on the Peavey

Take the mono output from the desk to the powered subwoofer, it should have it's own crossover/low pass filter built in.

Yes, you can use the A output, as long as you're OK with it being a mono system. It may be helpful to read the manual which has a lot of info including possible setup configurations. Here's a link-
http://www.mackie.com/products/srm1801/pdf/SRM1801_OM.pdf

Here is a link to the owners manual. I hope this helps you.
http://www.mackie.com/pdf/ppm_om.pdf

On page 28 of your user manual there is a block diagram. You will find the outputs on the right side of the drawing... They will innclude the mains, the mono, the subs and aux andd the tape outputs. There are a bunch and many are stereo types.

You can do a major amount of troubleshooting using tests from the many jacks on this unit.
I can walk you through a lot of those if you keep getting back to me with the results. First test: When the failure occurs does one or both sides of the headphones plugged in the headphone jack ALSO quit? Also does the level meter LED's reflect loss of signal? If these are still OK I want you to plug the headphones into the MAIN MIX MONO OUT jack. The headphone signal won't be very strong, but is it OK and not distorted.

I hope you have remembered to use BALANCED (TRS) audio interconnect cables and not plain mono cables from your mixer to the amps. Use of mono cables shorts out one side of the balanced output driving amps in the mixer. Also the other send of these MUST connect to balanced amplifier inputs... NOTE some amps don't have this and you have to use a BALUN or a DI at that end.

Lastly, ALL inteconnected equipment MUST be powered from the same source or receptacle for system safety.

Feel free to contact me via email or whatever.

use the xlr (3 prong) main left and right outputs of the board. get xlr to 1/4 inch cables. one end will be 3 prong, to plug into the mixer, then the other end will be a mono 1/4 inch plug, like a big headphone plug. Then you have to get a dual mono 1/4 inch to stereo 1/8 inch adapter and plug it noto the line in. if there is no lone in, but a microphone jack instead, you will get a mono signal instead of a stereo signal. in this case, just use 1 channel of the mixer, instead of both of the stereo outs, and use a single mono 1/4 inch to mono 1/8 inch adapter.

the xlr to 1/4 inch cables can be purchased at a music store. the 1/4 inch to 1/8 inch adapters will probably need to be purchased at radio shack.

Use TRS to TRS balanced cables from the M Audio to the line in 11 and 12.

Set the pan controls for the 11 and 12 to opposite directions to split the stereo to left and right main outputs. (otherwise both main outs mix the left and right and you get mono result.

The user manual has fairly good diagrams.

Get user manual here:

http://www.mackie.com/products/1604vlz3/pdf/1604VLZ3_OM.pdf

On page 34 is the BLOCK layout which has everything you need to know, once you figure how to read it!!!

The Triangle symbols are operational amp/analog summing amps.

By looking at the jack symbols you can tell if they are mono or TRS.

A lot of the TRS ones will show a TRS three lead jack but have a resistor to ground. These can be used as mono's.

The TRS (stands for Tip-Ring-Sleeve) connectors are used in two ways. One is as a balanced input where both the signal and its inverse is used. A balanced line is far more noise free and ground loop free than an unbalanced line.

Another use of the TRS is for external effect insertion where the sleeve is ground and the tip is the signal SENT to the external effect box and the ring is the RETURNed signal from the effect box.

SOMETIMES you may have to make your own cables to get the signals where you want them on the connectors.

HINT: Use XLR connections wherever you can. More rugged, balanced and noise free- ground loop free.

If all other functions work for those channels, the most likely problem is the fader itself. These can fail and operate more like switches rather than faders. Without witnessing the behavior, I can not state that for sure. While these mixers are not the hardest to work on, they are time consuming. The faders can be purchased from Mackie directly. If you need to have this repaired, any shop that repairs audio gear should be able to erpair this for you. Where are you located?

Dan