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Author Topic: Dolby lake noisy?  (Read 1190 times)

Terry Fryar

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Dolby lake noisy?
« on: February 28, 2012, 01:55:33 pm »

We have a dolby lake that we've used over the last year or two to drive our larger line array.  I've notice some "hiss" in the higher frequencies...nothing too major, but it always bothered me!  Last year, we converted all our amp racks to x20 to knock down the noise floor a bit, as the lake has plenty of output drive.  Oddly, it didn't seem to make too much of a difference.  Given the big array's up in the air it was a non issue for the season.  This isn't 60hz or any bad wiring...it's just noise floor.

However, this year, I'm setting up a new vertec 4888 rig using this same lake.  Been using smaart to do some adjustments and such and in the shop I notice the noise floor seems to be fairly high.  This is odd, as our signal chain is pretty tight....we clip the lake just right after the console, sound output quality is very good and our gain structure seems solid.  I've noticed this using both the v4 settings, and some other custom ones.  I believe with the v4 settings, there is a filter somewhere up high (maybe 13k or so?) that extends the freq range up high.  We have a similar filter in our custom settings and I've bypassed that filter, but it doesn't seem to matter much.  This hints the noise isn't coming from upstream.

I've played around with the rms headroom on the lake's inputs to no avail and I "forced" the input selector to analog just in case.  I recall the noise being there even with the analog inputs to the lake unplugged.  Seems like it was there with the outputs muted also?  Now, we aren't driving the lake's outputs very hard and the amp attenuators are wide open...I realize there's room there.  But this noise has me puzzled.  We had a BSS omnidrive running the old array years ago and it was whisper quiet!  Seems like this particular lake's been a bit noisy from the start (we bought it used).  I can certainly crank the amps down 15db and drive the crap out of em....but I have a feeling the lake's not quite right?

Anyone run across a noisy dolby lake?  Perhaps there's a setting I'm missing in the lake?  Perhaps the input card's hosed?  I doubt the outputs are bad, as I notice this noise floor across all 8 of them.  Any ideas?  I guess I'll get smaart out and do some comparative measurements in the signal chain and see what I've got.  Historically, we've been able to plant our larger array in some indoor smaller area and the s/n's so good you can't even tell the rig is on!  Given the smaller 4888 and where it'll be used, I really need to get that noise floor back down.  I hate to crank the attenuators down...then I'll have to reset the limiters and if our "high school help" cranks one all the way up at a show...I'll be replacing drivers!
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Hayden J. Nebus

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Re: Dolby lake noisy?
« Reply #1 on: February 28, 2012, 07:28:17 pm »

We have a dolby lake that we've used over the last year or two to drive our larger line array.  I've notice some "hiss" in the higher frequencies...nothing too major, but it always bothered me!  Last year, we converted all our amp racks to x20 to knock down the noise floor a bit, as the lake has plenty of output drive.  Oddly, it didn't seem to make too much of a difference.  Given the big array's up in the air it was a non issue for the season.  This isn't 60hz or any bad wiring...it's just noise floor.

However, this year, I'm setting up a new vertec 4888 rig using this same lake.  Been using smaart to do some adjustments and such and in the shop I notice the noise floor seems to be fairly high.  This is odd, as our signal chain is pretty tight....we clip the lake just right after the console, sound output quality is very good and our gain structure seems solid.  I've noticed this using both the v4 settings, and some other custom ones.  I believe with the v4 settings, there is a filter somewhere up high (maybe 13k or so?) that extends the freq range up high.  We have a similar filter in our custom settings and I've bypassed that filter, but it doesn't seem to matter much.  This hints the noise isn't coming from upstream.

I've played around with the rms headroom on the lake's inputs to no avail and I "forced" the input selector to analog just in case.  I recall the noise being there even with the analog inputs to the lake unplugged.  Seems like it was there with the outputs muted also?  Now, we aren't driving the lake's outputs very hard and the amp attenuators are wide open...I realize there's room there.  But this noise has me puzzled.  We had a BSS omnidrive running the old array years ago and it was whisper quiet!  Seems like this particular lake's been a bit noisy from the start (we bought it used).  I can certainly crank the amps down 15db and drive the crap out of em....but I have a feeling the lake's not quite right?

Anyone run across a noisy dolby lake?  Perhaps there's a setting I'm missing in the lake?  Perhaps the input card's hosed?  I doubt the outputs are bad, as I notice this noise floor across all 8 of them.  Any ideas?  I guess I'll get smaart out and do some comparative measurements in the signal chain and see what I've got.  Historically, we've been able to plant our larger array in some indoor smaller area and the s/n's so good you can't even tell the rig is on!  Given the smaller 4888 and where it'll be used, I really need to get that noise floor back down.  I hate to crank the attenuators down...then I'll have to reset the limiters and if our "high school help" cranks one all the way up at a show...I'll be replacing drivers!

Why don't you use smaart to measure the electronic output of just the processor?
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Re: Dolby lake noisy?
« Reply #1 on: February 28, 2012, 07:28:17 pm »


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