Distorted returns

[Phil.c]

I noticed that my Altec was distorting, I got it checked out but there was nothing wrong with it, it seems like the XLR input is distorting, I've never had this problem before? A few weeks ago I stripped the desk to change worn switch buttons, just wondering if this might have caused the problem with ribbon connectors etc anyone had this problem?

[Y-my-R]

Which XLR do you mean? A Mic input on the D8B or on the Altec?

I had some dirty pre pots on the D8B, that wouldn't stop distorting in any position until I cleaned them out with Deoxit Fader F5. Other than that, I didn't have distortion on the D8B XLR inputs (if that's even what you're talking about).

[Phil.c]

Yes, the mic inputs.

[Bruce Graham]

Hey Phil;

Maybe I am missting something but the XLR I/P's on the d8b are mic level (-50dbu +/-) and the Altec O/P is line level (+4dbu +/- RMS), Right???

Bruce

[Phil.c]

I'm not sure Bruce, the Altec has an open output so full on, my Chandler RS124 has a controlled output, when that's set half way everything is ok, but when I open it right out the same as the Altec I get distortion. I've always used the Mic I/P's and have always had no problems, even if I use the standard Line I/P's I get the same, the only thing that has changed is that I added new switch buttons which meant taking the surface board out, maybe a ribbon connector issue, anyway, later I'm going to couple up another desk that should varify things!

Phil

[Bruce Graham]

Hey Phil;

I had a look at the spec on the Chandler RS124 and although it is 200 to 600 ohms, there was no level mentioned.

What is an open output? I haven't heard that term before?

Just to make sure, for me, I went to my room and adjusted my oscillator (at 1KHz) for +4dBu, and put it into a mic inout on my d8b and it really doesn't like it. I adjust the gain on thre d8b but it was still on the high side and distorted. Connected it into the line input on the same channel, all was good. So..........?????

Unless there is a pad (like 40db), I'm not sure why it hase worked in the past? Not doubting please understand, I just don't have enough info to help ugggest why it's not working any more.

Here's a couple of other thoughts for trouble shooting

- Does the same channel you are connecting this signal into, sound good with a mic?
- Do you get the same results with all other channels (Mis inouts)?
- Do you have access to an extended range VU meter? If not do you have a Volt Meter and a 600 ohm resister? I want to know what the levels "actually" are.

Thanks
Bruce

[Phil.c]

Thanks Bruce, it's now sorted, I'll explain, what I meant by open output is the output up full, the Chandler is adjustable from off the full, the Altec is set at full.
My other effects are all line in to the desk except the Altec and Chandler, they've always been this way, don't ask me why, maybe I didn't have stereo jacks at the time of making the leads? Anyway, they worked because the main gain knob was right down and the input was adjusted with just the digital trim knob, what had caused the distortion is, when I removed the surface board, the gain knobs must have turned up overloading the input signal, as I said I always adjusted with just the digital trim knob but when I turned this down it didn't stop the overload even though the VU's weren't clipping.
I'm now using line in's for both compressors and they are sweet, the Altec has just had some new caps fitted and a thorough check out and it's sounding great.

[Bruce Graham]

Glad you got sorted. I had no doubt.

I have a Ward-Beck M405C, Extended Range VU that I use to confirm "actual" level of audio signals Very handy tool. I wish I had the model that has a PPM meter! Oh well!

It is adjustable from -50dBm to +30dBm. so it coveres quite a range of signals at bridging and loaded (600ohms).

Cheers'
Bruce

[Y-my-R]

I read along here, and it was a great reminder that I should actually calibrate my outgoing and incoming levels properly, to get the best possible gain-staging setup and best resulting signal quality out of my setup... I never really did that for the D8B and the outboard gear I tie in with it and just made the settings on-the-fly, when I needed to send something out, etc.

Thanks to this conversation, this made me look into how to properly calibrate such levels, and was looking where the D8B's test-tone generator/oscillator is (I didn't know before). It's part of "Acuma Labs - Pro Audio Lab" on the D8B.

If you're using the crack and have all the plug-ins, you have that one as well.

So, this allows you to play a test tone at a frequency you can choose (e.g. 1 kHz sine), and route that tone anywhere, where the output of other plug-ins can be routed. In my case, I wanted to set the levels for my outboard gear, so I sent the signal out a pair of (physical) Aux Sends, through (bypassed) outboard gear, and then back to the D8B... and made sure that the signal comes back at about the same level it went out.

This didn't work with all the gear, of course... for example, I have a few devices that use unbalanced connections, so they can't handle a +4 dB level. But at least the test-tone from Pro Audio Lab allowed me to get an idea what signal level I can send to a particular device and where the various gain settings need to be, to get a healthy signal out into external gear, and a healthy signal back into the D8B, at the level it expects/needs for that input.

Long story short: Thanks for asking about this... I hadn't really discovered the Oscillator in the Acuma Labs Pro Audio Lab plug-in, and this gave me some revelations about some struggles I had with some external gear I'm using (e.g. a GSSL Bus Compressor with a really finicky Threshold setting, that was apparently just because I always sent the wrong level to it).

Just thought I'd share... maybe finding the Oscillator in that plug-in will help others here as well

[Bruce Graham]

Hey Lads;
In my proffessional life "Correct Level" had to be maintained. This was the analog days, where not only the correct level observed but impedance was important as well. We had to pass-on, or accept levels from hundreds of other Boroadcasters (be they live or recorded events), and it was important to "change" their levels to match your levels, for recording or distribution. So it was dilled into us. Knowing what is being sent to you is vital to maintain signal quality when you on-pass it to some one else or into a oiece of gear. Sending a signal that is balanced at +4dBu into a piece of gear that is unbalanced and -10dBv needs to be looked at and trated properly.

I recall a post in hear about mixing with our ears and not with meters. I get it but, when mastering and when broadcasting those levels need to be corrected for everyone else. So they know what they are getting. In an isolated world (your studio for you and your friends), it is one thing but not "Mastering" properly gives the results like the CD's of the last 2 decades (maybe longer), the continuing adjust of the volume control on playback devices. "This ones too loud, this ones too quiet". "Why is that?" Hmmmmm? Differing audio standards, if there even was a standard considered!

As I mentioned, I use an Extended Range VU meter, and I also have a variable outboard Oscillator (Level and Frequency) that I calibrate using the Extended Range VU. Handy and keeps things working propoerly, and helps to identify faulty gear to.

Just my observation and my opinion, and apparently my OCD thingy!

Cheers
Bruce