[Boatanchors] OT: A question about using an 'audio mixer' in a ham set-up

Wed Apr 6 17:57:48 EDT 2016

I use an Extron MAV Plus audio router. It is a crossbar switch allowing interconnection of any input to one or more outputs. It is controllable with front panel switches and also using a web browser.

Here is some information on it:
http://w2hx.com/x/Extron/

I have both 16x16 and 32x32. I think they even sell 64x64 and 8x8, etc.  Search google for ebay MAV Plus. Many switch both video (all kinds) and audio. The one you want has the lit up switches with number labels on the switches. There is another model with the labels above and below the switches, but that doesn't have the network access which I find useful. I can switch audio sitting at my operating location and the switcher is off in a rack.

The prices on ebay vary greatly, but good deals can be found with patience. I paid probably $200 maybe $250 for my 32x32. If you find one missing switch covers, they can be purchased from the company (and possibly ebay as well).

I should point out that this is for low level audio, not speaker level.  I use mine to route audio from receivers to things like my pc, terminal units (for RTTY), audio amplifiers/speakers, etc.  But I also use it to route audio FROM TUs (using teletype machine and loop), my PC and mic audio (through a preamp) to any transmitter in the shack (for those that will take line level input which is nearly all the ones I have).  It is all very convenient and very handy little thing. 

You can see it in this picture of my shack (look about midway up the rack in the distance. You can see all of the audio lines in and out from the back.

Good luck!

-----Original Message-----
From: Boatanchors [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Phil
Sent: Wednesday, April 06, 2016 5:11 PM
To: Boatanchors
Subject: [Boatanchors] OT: A question about using an 'audio mixer' in a ham set-up

Hi All,
First, sorry about the OT post, but I really don't know where else to ask this question, and I suspect that 'some' of you may use audio mixers and other advanced techniques in your ham stations. Especially if you're into using BCB AM transmitters etc.

The first part of this message is general info, at the end are a couple questions.

My 'receiving post' has expanded greatly over what it once was, with the ability to simultaneously use multiple receivers, make overnight recordings of a wide spectrum (192kHz) of the LF band, etc.

The antenna routing is taken care of with the antenna/rig select witches and 4 port receive multicoupler, but the audio routing is quite primitive, a single 5 position switch to select which receiver feeds the audio filter/headset/speaker etc.

In addition, routing the computer audio (when listening to the
recordings) complicated matters.  In addition, the computer sound card feeds my "Fender Passport 150 Pro" stereo PA system (75W/channel) and with it's decent sized speakers and 150W sub-woofer serves as my "stereo" system

Well, I just ordered a used Timewave DSP-599zx filter to augment the homebrewed audio CW filter (440Hz CF 8Hz Wide).  So that complicates things further.
************************************

Then while I was working on the churche's mixing board (Behringer 24
channel) it hit me.  What I needed was a smaller version of the board for my receiver interfacing and general audio routing!

An Amazon search for mixers turned up this unit which seems to be ideal for my application.  Yes, it has special effects which aren't useful for ham radio, but I'm also a (church) musician who plays guitar and piano/synth.  SO it just might get some music use in addition to the ham-shack.

http://www.amazon.com/Behringer-Xenyx-1202fx-Mixing-Console/dp/B000J5Y214?ie=UTF8&psc=1&redirect=true&ref_=od_aui_detailpages00 

I figure that I'll use channels 1-4 for receiver inputs (using the 'Hi-Z line' input of each channel for the receivers).  That will let me "eq" 
the receivers, limiting the audio response to reduce any hum or hiss etc.

The computer sound card will feed one of the stereo inputs.  There aren't any "eq" functions on those inputs, but it's not needed, the computer media player has eq built in, though I normally leave it pretty much 'flat'.

The Effects "send" control on each of the channels will let me route the receive audio to the effects output where the two audio filters
(cascaded) will be connected, then routed back into the board.

When I want to use headphones the "Control Room" feed will feed the headphone output of the board.  When I want speaker audio the "Main" 
output will feed the Fender System.

I'm sure it'll take a bit of playing around to get everything routed and set up just the way I want it, but it'll be a HUGE improvement over what I've been doing. . .
***************************************
I didn't even think to check eHam reviews until after I'd already ordered the board, and I was a bit surprised to see that some people ARE using this exact board in their Ham station, with generally favorable reviews.
***************************************

QUESTIONS:
While this unit will be used for RECEIVE ONLY, not in the transmitting chain, the receive audio from my Transceivers (IC-7200 & IC-735) WILL be routed through it and in use on the occasional QSO's I have (I listen far more than I transmit).

1.  How susceptible is something like this to transmitted audio getting into the system (I only run 100W, no real power)?

2.  I have a large number of QUALITY 1/4" TRS plugs (shielded) on order to make up patch cables between receivers and board, audio filters and board, and the Fender Amplifier and board.  I wonder if it'd be worthwhile to put an "RF filter" comprised of a small series resistor (maybe 1/4W) and capacitor to ground on the board end of EACH patch cable as well as the input end of the cables going to the Fender. If so what would be suitable values for resistor and capacitor?  I think that 
with small enough parts they'll fit right in the plug,   Something like 
this.  Please excuse the crude ASCII graphics, it's not something I do often. . .

Input >----^v^v^v---v-------> To board input
              Res    l
                   ------
               Cap ------
                     l Ground
                     V
                     v

Several things I REALLY like about this board (or think I will ;-)

1.  It's fairly compact, NOT like the 24 Channel one we have at church that's nearly 4 feet wide, and which barely fit on my workbench when I worked on it (XLR mic connectors had broken solder joints to the PCB as well as scratchy controls).

2.  The Cost, it's REALLY quite economical (though Behringer doesn't have the greatest rep for reliability in rough use).

-- 
73 From "The Beaconeer's Lair"
Phil, KO6BB
http://www.qsl.net/ko6bb/  (Web Page)

PRESENT HF/LF RADIOS:
Grundigs: S-350 (~2006), G6 (2011) & S450DLX (2014).
HOMEBREW: 7 Tube+Rect 1v3 Regenerative RX for LF (built 2015)
Icom:    IC-735 Transceiver (~1990).
Icom:    R-75, Cascaded 250/125Hz CW-Filt, Panadapter. (~2009)
Icom:    IC-7200 Transceiver (~2015).
R-Shack: DX-380 digital portable (~1990).
SDR:     Softrock Ensemble II LF (built from a kit 2015).
Zenith:  Royal-7000 Transoceanic Portable (~1968).

ACCESSORIES: HOMEBREW LF-MF Pre-Amp, MFJ-993B HF Auto-Tuner.
              HOMEBREW 8 Hz Audio Filter.

ANTENNAS:  88 foot Long Ladder-line fed dipole, 35 feet AGL for MW/SW.
            Active Mini-Whip, 36 Feet AGL for LF/MW/SW.
            37 foot "Low Noise Vertical", 11 feet AGL for LF/MW/SW.

Merced, Central California, 37, 18, 37N   120, 30, 6W CM97rh

______________________________________________________________
Boatanchors mailing list
Home: http://mailman.qth.net/mailman/listinfo/boatanchors
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Boatanchors at mailman.qth.net

List Administrator: Duane Fischer, W8DBF
** For Assistance: dfischer at usol.com **

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to w2hx at w2hx.com