Mic and Mixer set-up question.

[Grogan]

I know I can olny get so much with a mic and mixer board, The Radio without mods will limit it's Audio. I have a Shure PG-48 mic with a Xenyx-802 mixer bd. and was wondering where to set the Low,Mid and High EQ settings.Is it best to monitor thru talk-back, Have someone I can trust to help me on their radio, monitor thru the board? Low is 80 HZ -15 to +15, Mid is 2.5KHZ -15 to +15, High is 12 KHZ +15 to -15. Thanks for your in-put.

 

[Grinder74]

What radio? If it is a mobile you could start with PA. The best is a second radio to monitor your transmitted audio.

 

[dave457]

Try this....
Low +4/5 db
Mid -6/8 db
high +4/5 db

 

[Grogan]

I will try those settings, the radio is a galaxy DX-979 with a base set up, I can Also switch to a Connex 3300fHp thanks

 

[Robb]

Hi Fi mod for ept6900 series board
Galaxy 900 series radios 919 through 979

Receive

Remove C39
Change C78, C40 and C185 to 2.2uF non-polarized electrolytic
To add more highs change C184 to a .001uF ceramic disc

Transmit

Want more Bass?
Change C-154, a .22uF 16V tantalum, to a 3.3uF 16V tantalum.
Change C-171 and C-235 to .47uF 50-100 volt Mylar.

For even more Bass:.
Change C-154, a .22uF 16V tantalum, to a 10uF 16V tantalum.
Change C-171 and C-235 to 2.2uF, 50-100 volt Mylar.
(the 2.2uF non-polarized and the 10uF tantalum available at Radio Shack)

 

[RatsoW8]

How are you matching the impedance of the line output of the mixer to the mic input of the radio?

 

[GnG8d]

How are you matching the impedance of the line output of the mixer to the mic input of the radio?

The output of the mixer should be low enough to work. Most of this audio gear sticks with the high input, low output theme instead of trying to match impedences with a plethora of different pieces.

edit___
I just looked, it's 120ohm output. It would be nice if the radio had a little higher input impedance, but it should work.

 

[Robb]

I think Ratso was trying to say that using a xformer between the mixer would match the impedance and remove hum from the signal.

 

[GnG8d]

I think Ratso was trying to say that using a xformer between the mixer would match the impedance and remove hum from the signal.

You could you use an impedance matching transformer, or just a 1:1 isolation transformer to get rid of hums. I keep everything balanced as late in the chain as I can before feeding unbalanced to the radio and I haven't had any issues yet.

 

[Captain Kilowatt]

Matching impedance will ensure maximum power transfer which is not really an issue in this case however it will effect frequency response. In an audio circuit if the two impedances are vastly different then the frequency response may be affected. Of course this can be compensated for by using an EQ. In the case of using an EQ on a radio, every radio is different and everybody has a different voice so asking where to set the EQ at is pointless. Best to listen until you get the result that YOU want and then ask for other's opinion when they hear you. Follow up with more adjustments as necessary.

 

[RatsoW8]

I think Ratso was trying to say that using a xformer between the mixer would match the impedance and remove hum from the signal.

Exactly and what CK said.

 

[GnG8d]

Matching impedance will ensure maximum power transfer which is not really an issue in this case however it will effect frequency response. In an audio circuit if the two impedances are vastly different then the frequency response may be affected.

I ageee. That radio is probably 400ohm input (maybe 600ohm), so 120ohm out of the mixer should be fine.

If I remember, the audio industry tries to adhere to 10:1 ratio when making this equipment ..... low impedances driving high impedances ....... keeping current down and voltage up. The 10:1 ratio I believe was to allow more than one peice of gear driving another stage of gear keeping inline with low impedance driving the high impedance.

 

[Robb]

Most Pro Audio gear uses a balanced low impedance XLR/TRS outputs and Grogan will probably have to sum the negative and ground leads together. Unless he gets a xformer that will do that too, they do make them and would prolly be the best thing to do.

 

[GnG8d]

Most Pro Audio gear uses a balanced low impedance XLR/TRS outputs and Grogan will probably have to sum the negative and ground leads together. Unless he gets a xformer that will do that too, they do make them and would prolly be the best thing to do.

I already said that. The key is staying balanced as long as you can and then going unbalanced. I do that with a dpdt while keying the radio, I can also switch polarity. If he has noise issues a few ferrites might work but the isolation transformer is a pretty sure bet.

edit___
Good wire is key too, most audio cables aren't shielded for RF, I only use HeilWire for cables.

 

[Captain Kilowatt]

I ageee. That radio is probably 400ohm input (maybe 600ohm), so 120ohm out of the mixer should be fine.

If I remember, the audio industry tries to adhere to 10:1 ratio when making this equipment ..... low impedances driving high impedances ....... keeping current down and voltage up. The 10:1 ratio I believe was to allow more than one peice of gear driving another stage of gear keeping inline with low impedance driving the high impedance.

The pro audio industry likes to keep impedances matched. In the case of consumer audio gear where you often have mismatched impedances it is always better to have a low impedance driving a higher impedance. There are several reasons for that. we often used audio distribution amps that had an output impedance of 0.1 ohms. One benefit of this was that any hum or stray audio superimposed on one branch would not feedback to all branches as it saw a near dead short at the distribution amp end and series resistors as well. A high source impedance driving a low load impedance is not so good.