Topic: SVU-1 Calibration affected by heat?

[mmmatt]

What makes you think the l/r output of the adc is perfectly ballanced to the analog out of the ua5?  End of the chain is the only place where there is not room for error... slight as it may or may not be.

Matt

[blu666z]

What makes you think the l/r output of the adc is perfectly ballanced to the analog out of the ua5? End of the chain is the only place where there is not room for error... slight as it may or may not be.

Matt

I have to assume that the -3db light does what it supposed to and that is what I am calibrated against.

-Kevin

[dklein]

What makes you think the l/r output of the adc is perfectly ballanced to the analog out of the ua5? 

It's not...
The analog out is affected by 2 things which DON'T affect the digital output (and can lead to bad readings after you've calibrated
1) monitor switch (on/off, should be off, pain in the butt since it defaults to on)
2) output level (the one above the headphone jack)

And if you accidentally leave the monitor button on, then the monitor volume level becomes the 3rd factor that changes analog output level without affecting digital output level.

So yes, the line-out of the JB3 would be the best place to run the SVU for consistency.  The down side is it *might* shorten the JB3 battery life a little bit as the JB3 is now driving an additional load.

[blu666z]

The only thing I don't understand is, if the UA-5 is run with the setting consistent with how they were when it was calibrated, what does it matter?  Consistency is the only thing that bit me this time because I didn't realize the REC Source button would change the output on the RCAs.

-Kevin

[willndmb]

i personally don't think you need to run the svu nonstop if jb3 battery power is an issue
chances are after a few songs are are not going to change the levels and could turn off the svu anyway

[dklein]

The only thing I don't understand is, if the UA-5 is run with the setting consistent with how they were when it was calibrated, what does it matter?  Consistency is the only thing that bit me this time because I didn't realize the REC Source button would change the output on the RCAs.

-Kevin

I guess it doesn't matter if the setup is consistent.  But that means no movement of dials and you have to remember to turn the monitor button off every time you power it up.  I don't think you can properly calibrate with the monitor on.

[blu666z]

I don't think you can properly calibrate with the monitor on.

Why?  I calibrated mine with the monitor on since that is the default...again, if it's consistent.....

[dklein]

You tell us - does it work or not?  Sounds like you're having some trouble.  With the monitor button on, any gain changes you make affect the signal twice.  Once on the jumpered path and once thru the monitor path.  I wouldn't think that's linear.  My guess is the higher the gain setting, the more the SVU and JB3 drift apart, with the SVU displaying artificially high levels.  Just a guess.

Enough guessing - time for you to test it.
Take some FM hiss from your stereo and use the headphone out > UA-5.  Confirm the monitor button is on and adjust the UA-5 input until you're at a steady -3dB or something like that (as read on the SVU).  Record it.  Now drop the volume on your stereo and turn the UA-5 gain up until you're back at a steady -3dB on the SVU.  Record it.  Compare the levels on the 2 recordings.

[blu666z]

I thought the monitor switch only affected what was output through the headphone jack on the front of the UA-5.

I'll try and run the test you suggested tomorrow.

-Kevin

[mmmatt]

I thought the monitor switch only affected what was output through the headphone jack on the front of the UA-5.

I'll try and run the test you suggested tomorrow.

-Kevin

the headphone jack and the rca out on the ua5 share the same amp... it is a split signal going to both.  This is why many people give an analog patch off the ua5 from the headphone jack... yet another thing that would screw with your metering if you choose to patch from your ua5.

Matt