Turtlerock Forum

After kicking myself 1000times after not picking up that one of my leads was phase reversed (made for some interesting drum overhead sounds!) i decided to go through and check them all, and on the way check the levels through some of my gear using a +4dBu test tone..

i have a pair of avalon 737s, consecutive serials..

i neutralised all the settings and then put the test tone (1k) through, on the 1st preamp the VU reads just below 0, and on the second, +3 ?!

I then ran the outputs into protools and checked that they both showed up at -12db, which they did...

so at this stage it seems that i can't really trust the VU on the one of the avalons, i'm guessing i'll need to get them checked out? any idea where?

Martin wrote:After kicking myself 1000times after not picking up that one of my leads was phase reversed (made for some interesting drum overhead sounds!) i decided to go through and check them all, and on the way check the levels through some of my gear using a +4dBu test tone..

i have a pair of avalon 737s, consecutive serials..

i neutralised all the settings and then put the test tone (1k) through, on the 1st preamp the VU reads just below 0, and on the second, +3 ?!

I then ran the outputs into protools and checked that they both showed up at -12db, which they did...

so at this stage it seems that i can't really trust the VU on the one of the avalons, i'm guessing i'll need to get them checked out? any idea where?

One of the best things i've bought (and yes, i'm almost ashamed to admit it) was a $75 bear ringer cable tester. it's really bloody handy!

I went through and every patch and mic cable I own (about 150 or so) and found about 3 that were mysteriously phase-reversed. I knew I had some (as every so often I need to flip phase) but using a multimeter was too much hard work. I also spent a couple of hours finding little gremlins in the patchbay.

there should be a way of adjusting them by way of a little screw somewhere on the meter. alternatively, there'd be a pot somewhere to adjust them, maybe rob can tell you where it is.

Cheers

Chris

If the 737's are like the 747 then there is an adjustment pot for the VU accessible through the face plate. A small hole gives access and adjust with a small screwdriver.

the adjustment screw seems to only affect the neutral point when the compressor and meter buttons are in, seeing as its situated on the compressor section of the pre im assuming thats all it does

might have to take them get them looked at... thanks for the advice

yes the trim available through the front panel set the meter to 0VU in compressor mode ( no gain reduction )

there are two trim pots inside ( behind and to the left of the meter ) that adjust the unit for unity gain on the line in and adjust the meter to read the output level correctly ( ie 0VU for +4dBu out ). They are located on the main board. Avoid the four trim pots on the compressor sub board, small adjustments of these can throw your compressor settings and metering out the window.

I can't remember of hand which of the two pots does which! But you'll soon work it out, although adjusting the unity gain pot will also change your metering, but adjusting the meter pot will not change your ouptut level.
I've never seen a 737 that far out of spec, worst i've come across is 0.5dB, so i wonder what is happening here. In fact i'm not even sure that there is that much range available on the trim pots. Perhaps there is but i've never had to bend it that far.

Check it out....or send back to Mixmasters for a full check over.
Do you use them stereo linked? If so we can also fine tune the compressor tracking in stereo mode.

Rob

thanks rob, somethings definately out of whack, the same level signal fed into both meters very differently! although the sound is still fine its strange to see the meters swinging around so far out of whack with eachother. I'll look into sending them off when i can spare the down time...

thankyou everyone!