Distorted returns

[Phil.c]

Well this sends my memory back to the late 70’S when using Lasky noise reduction and running a small tape with a tone into the units to calibrate them!

[Y-my-R]

You're totally right, Bruce, and I know I shouldn't fly by the seat of my pants as much as I do, when it comes to setting levels between devices.

I'm generally aware of the need to match impedances as closely as possible and if a device allows, switch the impedances accordingly. In some cases, this makes a dramatic difference not only in signal-to-noise, but in frequency response and how much "punch" the signal has.
Heck... even when plugging a guitar straight into an audio interface and failing to set that input to High-Z, the sound loses a lot of its character and bite (even if enough gain is available to get the level to look right).
So, totally agreed on the importance of matching impedances, although I'm sure I'm not quite as careful about this as I really should be.

...and for calibrating levels. I was aware for a long time that I'm supposed to do that but always want to go straight to work, and calibration feels like it holds me back from getting started... so, when it sounds OK, why calibrate, I thought.

And to some degree, it's not quite as important today as it was during the analog days, where noise was a major issue. But still, some devices work best when they receive a certain level, and just don't sound as good, or the controls don't respond quite as they should, if the level doesn't come in at the expected (and sometimes a little narrow) range.

That GSSL Buss Compressor (SSL Bus Compressor clone) I have was a great reminder. It's a DYI kit but I got it used/assembled and always had trouble with the Threshold doing nothing and then suddenly jumping to action and doing too much when turning the knob the slightest bit. I thought the previous owner just didn't put it together right and even found instructions how to modify the circuit to make the threshold accept a bit of a wider range and was planning to do that mod, when I get around to it... until I noticed the other day, when I sent a test tone through it for the first time to calibrate the levels, that I just sent a completely wrong level into it every time I tried to use it before. It works fine, if the level going in is in a certain (fairly narrow) range.

So, basically, calibration "fixed" my setup... or my completely false understanding of the level this compressor unit was supposed to accept. In that sense, thanks very much, Bruce, for fixing my setup by pointing out that it's important to calibrate the signal path through external analog gear Feels like I just got a new compressor, years after I bought it

Long story short: While often ignored (and I'm guilty of that, too), impedance matching and level calibration is still important in this time and day.

As for myself, I'll try to make it a habit... at least until I know by heart around where to set the levels for my external gear to operate at its best

Thanks again, Bruce!

[Phil.c]

Just wondering, setting the balance on outboard effects with a tone signal and the VU's to 0 is well and good but what would be the setup (if there is one) for a compressor like an Altec or Chandler/EMI RS124 as the only meter is gain reduction?

[Bruce Graham]

Hey Guys;

Y my R, glad to hear that thinking about calibration, then checking your divice has solved the issue, which likely wasn't and issue, but just the wrong level!

Phil, I think the best way to get a handke on levels is to know what the levels should be. Here is few questiojn to ponder which I can't answer all, as I don'y know your gear. I know mine.

What is the level of the output of the Insert Jacks of the d8b first 12 inouts? Is it -10, 0, or +4dbu, or something else? What does the level on the meters actually read at the nominal level? I still haven't totally figured out what the d8b LED meters are telling me. Something I need to know after almost 10 years on this beast.

What are the input and output nominal levels of the device you are using, whether as an insert or in-line with an output. Again what are is SOL (Standard Operating Level (Nominal) and what SOL is the deive fedding it an receiving it. If, for example, the insert jacks are 0dBu and your device is +4dBu, there is a 4 db descrepancy in, and out which as long as you know this, you can adjust and you will know what the numbers mean. The threshold of the device (if a Compressor or Gate), will be 4 dB out, as will the output return. You wil know where to drop or make up gain. This of course is really not "critical" in this example, but what if your inserts are -10dbu, and you compressor is +8dBm? That is 18 dB difference and a difference of Bridgiung versus Terminated (600 ohms). Now you have an isuue.
Once you get a handle on thre correct SOL for your gear, calibration can be put aside as you have a handle on it. It would onlt be used to check the gear to proper operation (level and frequency), when you think it needs or before an important mix.

I check compressors with the thresold at infinit and the output level, if there is a knob, set at it's "0". Then I put in what it's correct SOL is (-10, 0, +4dBu), at 1kHz, and see what I get out using my Extended range VU. If what I put in is what comes out than the unit is :unity gain at 1kHz. I then sweep the frquency and watch the levels to ensure that the frequency response tracks other wise I have a problem.

Does that make sence and hopefully helps some.

Cheers
Bruce

[Phil.c]

Thanks Bruce for your in depth reply and I'm sure your correct way of setting up is correct But to be honest, with regards to my Altec And Chandler compressors, I've been running them on the fly so to speak for about five years and they sound great, if the setup is wrong it shows, they are a little different to modern compressors, for example, the more input the more compression, so, no ratio control, with me it tends to be, if it sounds right...it is right.

Regards,

Phil

[Bruce Graham]

Hey Phil;

It's all about what works. The creative side should always be in front of the Technical side of things.

Cheers
Bruce

[Phil.c]

True