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Title: DBX 266xl lights working but no compression heard! HELP!!
Post by: Joel McNaughton on February 07, 2014, 02:06:46 PM
Hey all - I"m not sure if I'm being dumb but as the title suggests I'm having a bit of a problem with my DBX compressor. All the lights indicate that the compressor is working, as I adjust the threshold for example, but I hear no difference through the PA. It's as if I've got bypass selected, but I haven't.

At first I had the master outputs from the desk going into the XLR inputs on the unit, and then into the PA from the XLR outputs. Then I tried using TRS cables and using the two channels as inserts, but the same thing happened each time.

Any ideas what it could be?

Thanks in advance for any help!
Title: Re: DBX 266xl lights working but no compression heard! HELP!!
Post by: Mark McFarlane on February 07, 2014, 04:39:48 PM
Hey all - I"m not sure if I'm being dumb but as the title suggests I'm having a bit of a problem with my DBX compressor. All the lights indicate that the compressor is working, as I adjust the threshold for example, but I hear no difference through the PA. It's as if I've got bypass selected, but I haven't.

At first I had the master outputs from the desk going into the XLR inputs on the unit, and then into the PA from the XLR outputs. Then I tried using TRS cables and using the two channels as inserts, but the same thing happened each time.

Any ideas what it could be?

Thanks in advance for any help!

What model compressor? What's your ratio and attack time set at?
Title: Re: DBX 266xl lights working but no compression heard! HELP!!
Post by: Ray Aberle on February 07, 2014, 04:45:24 PM
What model compressor? What's your ratio and attack time set at?
... are there multiple compressor models within the dbx266XL line? (He had 'DBX 266xl' in the subject line. I just don't know if you saw that, or missed it.)

-Ray
Title: Re: DBX 266xl lights working but no compression heard! HELP!!
Post by: Mark McFarlane on February 07, 2014, 04:55:21 PM
... are there multiple compressor models within the dbx266XL line? (He had 'DBX 266xl' in the subject line. I just don't know if you saw that, or missed it.)

-Ray

My bad, I missed that in the subject line.

To the OP, What is your ratio, attack, release, makeup gain, and how many db of compression are you getting?  Hearing low ratios, or low levels of attenuation takes a fairly well trained ear and the changes aren't usually noticed in volume, but rather in texture.

What you 'hear' is also dependent on the type of material you are putting through the compressor.
Title: Posting Rules
Post by: Mac Kerr on February 07, 2014, 05:17:56 PM
Hey all - I"m not sure if I'm being dumb

Please go to your profile and change the "Name" field to your real first and last name as required by the posting rules displayed in the header at the top of the section, and in the Site Rules and Suggestions (http://forums.prosoundweb.com/index.php/board,36.0.html) in the Forum Announcements section, and on the registration page when you registered.

Mac
Title: Re: DBX 266xl lights working but no compression heard! HELP!!
Post by: Joel McNaughton on February 08, 2014, 07:47:36 AM
My bad, I missed that in the subject line.

To the OP, What is your ratio, attack, release, makeup gain, and how many db of compression are you getting?  Hearing low ratios, or low levels of attenuation takes a fairly well trained ear and the changes aren't usually noticed in volume, but rather in texture.

What you 'hear' is also dependent on the type of material you are putting through the compressor.

Hey Mark - thanks for the reply, much appreciated. With the unit hooked up at home in both the ways stated above, I've played with all the attack/release settings along with the ratio/threshold and there's definitely no effect.

Perhaps most telling is that the makeup gain also makes no difference, so I'm wondering if I've got something fundamentally hooked up incorrectly (though I can't see what/how!) or if it's a common fault or anything? If the outputs were broken, presumably I'd hear no sound at all, rather than a sound unnafected by the compressor? The fact that the lights are indicating compression just makes it even more confusing?
Title: Re: DBX 266xl lights working but no compression heard! HELP!!
Post by: Mark McFarlane on February 08, 2014, 08:12:41 AM

Plug your mixer out into the XLR inputs. Amp/Speakers into the XLR outputs.  Play some music so your meters on the console are hitting around 0Vu.

Set the gate at threshiold=off, ratio = 1:1.  Set the compressor ratio at infinity, gain at 0, attack = fastest, release = slowest. Make sure the bypass is not engaged.  Lower the threshold from the highest to lowest setting, your volume change should be obvious and you should see when the reduction meters kick in.

If the volume change isn't obvious, stick something in the insert jacks and insert/remove a bunch of times. You could have oxidation on the insert which is normalled, so the unit may think it is receiving a side chain signal when it is not.  You might have to clean these jacks if the oxidation is bad.

Report back.
Title: Re: DBX 266xl lights working but no compression heard! HELP!!
Post by: Scott Stephens on February 08, 2014, 08:58:46 AM

Joel,
A few years ago DBX had some issues with lights and relays or cold solder joints. I had a 166xl that was funky. Harman fixed the issue at no cost, just shipping. It took about a little more than a week to get it back. Maybe it's the same thing.
scott
Title: Re: DBX 266xl lights working but no compression heard! HELP!!
Post by: Joel McNaughton on February 12, 2014, 01:11:50 PM
Joel,
A few years ago DBX had some issues with lights and relays or cold solder joints. I had a 166xl that was funky. Harman fixed the issue at no cost, just shipping. It took about a little more than a week to get it back. Maybe it's the same thing.
scott

Thanks again for the replies. Mark, I've set the compressor up like you said, and as I reduce the threshold I see the lights begin to indicate compression and continue to indicate further compression the more I lower the threshold, until the point that the they're basically solid red lights when the threshold is at its lowest. Regardless, the sound is unnafected. I do have some experience using compression (just to clarify that I know what it should sound like) and there is categorically no difference to the sound in this instance. The bypass is also definitely not engaged.

So in short, I have a faulty unit on my hands? Scott, thanks for your input - does what I'm describing potentially sound like the problem you encountered?

Thanks again for your replies - much appreciated...
Title: Re: DBX 266xl lights working but no compression heard! HELP!!
Post by: g'bye, Dick Rees on February 12, 2014, 01:32:00 PM
Thanks again for the replies. Mark, I've set the compressor up like you said, and as I reduce the threshold I see the lights begin to indicate compression and continue to indicate further compression the more I lower the threshold, until the point that the they're basically solid red lights when the threshold is at its lowest. Regardless, the sound is unnafected. I do have some experience using compression (just to clarify that I know what it should sound like) and there is categorically no difference to the sound in this instance. The bypass is also definitely not engaged.

So in short, I have a faulty unit on my hands? Scott, thanks for your input - does what I'm describing potentially sound like the problem you encountered?

Thanks again for your replies - much appreciated...

Just for fun, try exercising the side-chain inputs with a 1/4" jack.  Insert and remove the jack several times.  Using some Deoxit in the process won't hurt.
Title: Re: DBX 266xl lights working but no compression heard! HELP!!
Post by: Mark McFarlane on February 12, 2014, 02:16:32 PM
Just for fun, try exercising the side-chain inputs with a 1/4" jack.  Insert and remove the jack several times.  Using some Deoxit in the process won't hurt.

Sorry, I ASSumed you may not be familiar with compression.  MY bad.

I suggested oxidation on the side chain earlier, but based on the light behavior the compressor seems to be keying off the inputs.

Looking quickly at a DBX 266 (non XL) schematic it looks as though if the reduction lights are lighting, either the bypass switch or the VCA is malfunctioning. There are a few 'jumps' on the schematic that I didn't find so I may be missing something important.

Is the Bypass LED turning on and off when you hit the bypass switch? Maybe exercise the bypass switch a hundred times :)

Are both channels behaving identically?  Did you test each channel independently with 'stereo couple off'?  It seems odd that you'd have two bypass switches or two VCAs go out at the same time, but there is also circuitry that ties the two channels detection circuitry together. Does the stereo couple light go on and off? Maybe exercise the 'stereo couple' button

I'll let one of the more knowledgable electronics guys comment if they have time to dig further.

Here's the schematic:
http://adn.harmanpro.com/product_documents/documents/546_1324055740/266%20Schematic_original.pdf

The only docs I found for the UPC1252 (VCA) are in Chinese.
http://pdf1.alldatasheet.com/datasheet-pdf/view/103346/ETC/UPC1252.html