Calibration
Sine level
I used a Multimeter to get the sine tone level of +4 from the output XLR of the lunchbox with the unit installed, but I used XLR pin 1 and 2, but your instructions states pin 2 and 3? I do not get enough voltage using 2 and 3, the readings I get are mini-volts and not normal volts, unlike with pin 1 and 2 where its volts? Is this right?
XLR 2 & pin 3 is the balanced out and is the only correct pins to measure the +4dBu (1.23vac) Pin 1 is ground and pin 2 one side of the floating transformer output so there should be almost no volts. So I think you have this the wrong way around and have used pin 2 & 3. Remember pin 1 is on the opposite side in chassis male and female XLRs
I don't know why, I checked, its pin 1 and 2 for me. I am reading it from the XLR connector. So Joe, if you measure pin 1 and 2 with you, do you get mVolts because I get volts (1.25 volts was the closest in my multimeter)?
Balance Trimpot
I followed the instructions of turning the threshold knob until 5 on the VU, then flipping the Meter switch between GR and VU, to see if the VU readings match and if not, turn the Balance trimpot. When you turn the trimpot both VU and GR will change simultaneously, in opposite direction, so you switch back and forth and adjust the trimpot until they both meet and match.
Yes correct and when the meet readjust threshold to check they are correct at -5dB
So are you saying, mine meets at 3 on the VU and GR, so what I need to do is readjust the threshold until it goes back to 5 on GR mode. Then switch it to VU mode and do further balance trimpot adjustments until it matches again with GR mode. Then keep doing this until I eventually get matching 5 for both GR and VU mode? Is that correct?
Or is it, once it matches at any value for both GR and VU mode (mine at 3), then the GR and VU modes will match regardless even when I put the threshold at 8?
I don't know why, I checked, its pin 1 and 2 for me. I am reading it from the XLR connector. So Joe, if you measure pin 1 and 2 with you, do you get mVolts because I get volts (1.25 volts was the closest in my multimeter)?
When you get 1.23vac on the output what voltage is between pin 2 & pin 3 on the input XLR? Remember pin 1 & pin 2 are reverse on input to output XLRs
So are you saying, mine meets at 3 on the VU and GR, so what I need to do is readjust the threshold until it goes back to 5 on GR mode. Then switch it to VU mode and do further balance trimpot adjustments until it matches again with GR mode. Then keep doing this until I eventually get matching 5 for both GR and VU mode? Is that correct?
Yes
Or is it, once it matches at any value for both GR and VU mode (mine at 3), then the GR and VU modes will match regardless even when I put the threshold at 8?
Why did you choose 5?
Because I need a set reference to help me help you
Just did further checks and you are right, pin 2 + 3 gives 1.23vac, not sure what happened with my original measuring
I checked the VU and GR and my 5 is about 1 line notch to the right difference. So when I set my GR at 5, my VU is the line notch to the right of 5. I already installed the LA500a into my lunchbox and can't be bothered setting up the test rig again.
What exactly does this mean? So if I compress by 5 using the threshold, my output is actually lower than what is showing on the VU meter?
I presume this does not affect sound quality and just how I see the signal on the VU will be off? This will probably make my gain staging off by a few db if I rely on the La500a VU than a reading from the signal feeding the XLR in and returning to my DAW using a VU plugin?
Just did further checks and you are right, pin 2 + 3 gives 1.23vac, not sure what happened with my original measuring
I checked the VU and GR and my 5 is about 1 line notch to the right difference. So when I set my GR at 5, my VU is the line notch to the right of 5. I already installed the LA500a into my lunchbox and can't be bothered setting up the test rig again.
What exactly does this mean? So if I compress by 5 using the threshold, my output is actually lower than what is showing on the VU meter?
I presume this does not affect sound quality and just how I see the signal on the VU will be off? This will probably make my gain staging off by a few db if I rely on the La500a VU than a reading from the signal feeding the XLR in and returning to my DAW using a VU plugin?
For single LA500A comp that is perfectly fine. It is more for matching stereo pairs of LA500A comps this needs to be super accurate. So it should be working perfectly. Enjoy
Hi Joe,
one of my LA500a’s VU meter keeps winking at me. Ben off for a while then started working… kinda and just now since it hears me typing about it, has stop again! again, just appears to be the led in the meter.
Hi Joe,
one of my LA500a’s VU meter keeps winking at me. Ben off for a while then started working… kinda and just now since it hears me typing about it, has stop again! again, just appears to be the led in the meter.
you thoughts on servicing or replacement?
thx,
SteveMc
The meters have clear high brightness 5mm round led in them. First check the 4 meter tabs are soldered well to the pcb.
If the led fails open circuit the comp will going into hard bypass and adding a wire shorting the outside meter terminals will return the comp to working but no meter led.
If the led fails short circuit the comp will continue to work but no meter led.
The square section of the meter unclicks from the round section so the scale can be slid up and off to see the 5mm led pointing upwards and its 2 solder terminals to change it.
Hi Joe,
one of my LA500a’s VU meter keeps winking at me. Ben off for a while then started working… kinda and just now since it hears me typing about it, has stop again! again, just appears to be the led in the meter.
you thoughts on servicing or replacement?
thx,
SteveMc
The meters have clear high brightness 5mm round led in them. First check the 4 meter tabs are soldered well to the pcb.
If the led fails open circuit the comp will going into hard bypass and adding a wire shorting the outside meter terminals will return the comp to working but no meter led.
If the led fails short circuit the comp will continue to work but no meter led.
The square section of the meter unclicks from the round section so the scale can be slid up and off to see the 5mm led pointing upwards and its 2 solder terminals to change it.
Well… evidently it failed open as its passing tone as if it were bypassed(no change in output level or gain reduction)
and firstly, i re flowed solder to those tabs cuz they looked messy(pretty sure this the first of the two i built).
I added a jumper to the two outside meter terminals (ledk/leda) but that killed the input signal and just output noise-variable w make up pot. measured 15vdc from those led tabs to chasis. thanks for any input!
s
Hi Joe,
one of my LA500a’s VU meter keeps winking at me. Ben off for a while then started working… kinda and just now since it hears me typing about it, has stop again! again, just appears to be the led in the meter.
you thoughts on servicing or replacement?
thx,
SteveMc
The meters have clear high brightness 5mm round led in them. First check the 4 meter tabs are soldered well to the pcb.
If the led fails open circuit the comp will going into hard bypass and adding a wire shorting the outside meter terminals will return the comp to working but no meter led.
If the led fails short circuit the comp will continue to work but no meter led.
The square section of the meter unclicks from the round section so the scale can be slid up and off to see the 5mm led pointing upwards and its 2 solder terminals to change it.
Well… evidently it failed open as its passing tone as if it were bypassed(no change in output level or gain reduction)
and firstly, i re flowed solder to those tabs cuz they looked messy(pretty sure this the first of the two i built).
I added a jumper to the two outside meter terminals (ledk/leda) but that killed the input signal and just output noise-variable w make up pot. measured 15vdc from those led tabs to chasis. thanks for any input!
s
OK check the 2 10R on the sidechain pcb and the 2 10R on the LA500/BIO500 pcb are still measuring 10R??
loop back and relay working.
also, cable shows continuity.
anything else to check out before i put it back together and give it another go?
I appreciate your help!
thx,
Steve
If the BIO500 and cable work it is only one side of the GR/OFF/VU switch and 1k8 resistor and meter led in series in the path to turn the relay on the BIO500 on and off. Check all IDC10 pins are soldered on all pcbs
I just finished building a la500a and I was hoping to get it working similar to my la500 I built years ago.. the new one seems to be reading much higher on the vu than the old one.. probably somewhere between 5-10db higher(I don’t have the units in front of me)…
Using the 0vu trim doesn’t get me even close. Any initial thoughts,tips?
I just finished building a la500a and I was hoping to get it working similar to my la500 I built years ago.. the new one seems to be reading much higher on the vu than the old one.. probably somewhere between 5-10db higher(I don’t have the units in front of me)…
Using the 0vu trim doesn’t get me even close. Any initial thoughts,tips?
If you have 1.23vac = +4dBu on the balanced output between pin 2 and pin 3. The meter on VU for the first time will read bout -2dB and need to be turned up on the 0VU trimpot. The GR after that will be off the scale and need to be turned down by the zero gr trimpot a far bit to get back to 0VU
There is no gain difference between the LA500 and LA500A. The setup is identical.
