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is it possible to overload the input of a Bryston 4B? DAW Software
Old 4th September 2007
  #1
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is it possible to overload the input of a Bryston 4B?

I think I'm doing just that - I have Pro Tools going into a Bryston 4B > Proac Studio 100s, and when it's open all the way, it's like a fuzz face pedal. Am I losing it? This has never happened to me before...I didn't think it was possible to overload a Bryston.
Old 4th September 2007
  #2
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Tibbon's Avatar
I mean, you can overload anything. Just take the 120VAC from the walls and try that as your input. Instant overload.

Proper gain staging is still needed. Perhaps your monitor control or convertors are putting out too much. Pull out the scope/dmm and see what types of voltages you are seeing on the output.
Old 4th September 2007
  #3
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loving the fact that our names are EXACTLY the same (Dave Fisher here, too).

Don't have a scope available unfortunately. Any other way to troubleshoot macgyver style?

Worth mentioning - ProTools out says everything is hunky dory. I tried PT out > PT in with a sine wave, no visible distortion on ultra zoom even though I could hear it.
Old 4th September 2007
  #4
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Tibbon's Avatar
Nice to meet another... me?

Hmm. Lets see. I guess try outputting to something else, or try something else outputting to the amp. That's somewhat non-scientific, but if everything going into the Bryston distorts, then that's where the problem is. Leaky diodes? Hard to say. Try plugging an iPod into the Bryson input.

A really really good purchase for your studio would be a $20 Multimeter from the hardware store or radioshack even. If you can see that with a sine wave that you're getting a specific voltage out, then it's easy to figure out gain staging issues. Yea, there's advantages to the super expensive ones, but the $20 will get you started.

Does turning it down by 3dB or so help? What's your interface? Maybe some pots got turned on it?
Old 4th September 2007
  #5
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likewise

i do have a Fluke meter, but it's on the fritz, so it's useless.

Turning down DOES help - the noise goes away. The ipod idea is brillig - will try. Thanks.

I'm coming out of a Digidesign MBox. I don't *think* it's the Bryston - reason being that I can push the headphone out of the MBox too. It all started when I imported a mastered audio file from a "reference" record into a session and tried to listen - of course the meters were pegged, but not clipping (ahh modern mastering...), but the output was completely distorted. If I dropped the level down, distortion was gone, apparent volume the same. This all reeked to me of pushing the input stage too much. The whole problem is it doesn't make ANY logical sense to me. Why would it have clipped so hard at this oh so common level (just below 0 peak) - this would mean no modern mix session could be done on a PTLE session, which we know not to be the case.
Old 4th September 2007
  #6
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Rick Sutton's Avatar
 

Quote:
Originally Posted by auralman View Post

If I dropped the level down, distortion was gone, apparent volume the same. This all reeked to me of pushing the input stage too much.
Just curious, how and where are you turning the volume down when the problem goes away? If you are turning it down on the Mbox it is likely that the Mbox is just not capable of the drive level that you are asking it to put out. Could also be complicated by impedence issues between it and the amp. Also, you are not running any plugs, gain or ? inside of PT that could complicate this? Just wondering.
Old 4th September 2007
  #7
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"Just curious, how and where are you turning the volume down when the problem goes away"

cheating a bit - I'm turning the direct/playback knob towards direct. Nothing funky in plugins.

Could it really be impedance? The MBox is 1Kohms, I *thought* the 4B was 50/50, no?
Old 4th September 2007
  #8
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Rick Sutton's Avatar
 

I've got HD so I don't know exactly what the direct/playback knob would do in this situation. Tibbon gave you great troubleshooting advice. To repeat what he suggested, take the output of the Mbox into another amp (even a headphone amp) and see if the problem acts the same. If it does, the problem is generated at the source (Mbox or it's output cabling if that is also used) and not an overdriven input on the Bryston. My guess is the Mbox has only so much drive level available....only a guess. But it would seem a Bryston that is getting any kind of drive level would be damn loud on your speakers.
One more thing, does the Bryston have input levels on it? If so, where are they set? Cables direct from Mbox to Bryston with nothing in between? Balanced to balanced in?
Probably not impedence but if something is miswired or improper in/out combos used a higher impedence drive into a low impedence load can limit the output capability of the driving device and mimic the problem you're describing.....just throwing out ideas.
Old 4th September 2007
  #9
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the knob on the mbox just reduces the amount of mix vs. direct signal going to the monitor output. In this case, in the absence of input signal, it's just reducing the amount of playback.

no input level on the bryston.
Old 4th September 2007
  #10
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it turned out to be that i had bad connectors on one of my cables. Swapped out, sound is mighty and full again. I was pretty worried there for a while. Thanks to all those that made suggestions.
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