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Trident 80B users... help? Consoles
Old 10th June 2006
  #1
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Trident 80B users... help?

Alright, now that all of you are here...

I seem to have a problem getting anyone to help me out on this matter.

Is there anyone out there with an 80B that can do an eq test for me? I posted a thread a while back about mine having some inter-relativity between the low mid and hi mid sweep controls. I have what is obviously an earlier 80B somewhat customized from the factory. My input modules are the same as what is found in an original 80. I have a hunch that the eq circuit may have been changed on later versions and I'm trying to figure out how.

The test would be this...

1.) Which circuit board do you have? CB9182 or CB 9246?

2.) Run a 1K test tone into any line input. Adjust tone until it sits at -10 on the VU. Insert eq.

3.) Boost 1K (all the way counterclockwise) on the high mid band as far as it will go. Observe needle on VU. Put control back to 12:00

4.) Boost 1.5K (all the way clockwise) on the low mid band as far as it will go. This is where my eq doesn't do so well. I usually only get a couple dB worth of boost.

5.) Now, while boosting 1.5K on the lo mid band, turn high mid sweep fully clockwise.

If the needle on the VU went through the roof when you turned the high mid sweep control, then your eq is behaving like mine. If not, I would love a copy of your schematic.

Thanks to any and all who can do this test for me.

-Aaron
Old 10th June 2006
  #2
All 80's do this EQ thing, it's a design flaw that couples both mid EQ bands to the same opamp. Even 80C's do it as the layouts for the input modules are unchanged from 1979 on.

Trident was well aware of this at the time but didn't generate a new pcb layout for the input module to fix this.

When the 80C came out with the same EQ on the monitor side, Trident corrected the mistake on the monitor EQ but never fixed the input EQ's.

One would be wise to only use one of the mid bands at a time if possible.
All this from the "father of British EQ".

Jim Williams
Audio Upgrades
Old 11th June 2006
  #3
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Jim is correct. There is one opamp shared between the two midrange EQ bands, hence the interaction.

It's not a bug..............it's a feature heh
Old 11th June 2006
  #4
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I'm not sure I understand. What is the problem with the two sharing an opamp? Please use musical terms instead of technical terms.
Old 11th June 2006
  #5
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Quote:
Originally Posted by Jim Williams
All 80's do this EQ thing, it's a design flaw that couples both mid EQ bands to the same opamp. Even 80C's do it as the layouts for the input modules are unchanged from 1979 on.
I understand what you are saying. However, someone here in town has an 80 that does the same thing as mine. He said there is another guy in town that has an 80B and it doesn't do this. If there is a mod to be done or a way to improve the eq section, I want to at least know my options.

Quote:
Originally Posted by phelbin
I'm not sure I understand. What is the problem with the two sharing an opamp? Please use musical terms instead of technical terms.
When you turn the hi mid sweep (not the boost/cut), it affects the frequency center and/or boost/cut potential of the low mid band.

Basically, boost something on the low mid band. Now, turn the frequency sweep on the HI MID band. You should hear it changing.

Can someone please just do the test and tell me what you find?
Old 11th June 2006
  #6
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Fletcher's Avatar
Quote:
Originally Posted by Jim Williams
All 80's do this EQ thing, it's a design flaw
That's a bug? I thought it was a feature!!
Old 11th June 2006
  #7
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Quote:
Originally Posted by Fletcher
That's a bug? I thought it was a feature!!
It sounds weak to me.
Old 11th June 2006
  #8
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Quote:
Originally Posted by phelbin
I'm not sure I understand. What is the problem with the two sharing an opamp? Please use musical terms instead of technical terms.

The result of sharing the opamp is that the two different bands of EQ affect each other's sound slightly. For instance, once you have the upper mid-band set like you want it, changing the gain and freq of the lower mid-band can have some impact on the upper mid-band settings, which you had the way you wanted, presumably.

In practice, it's not that huge of a deal in my experience. And it's most pronounced when doing radical EQ, which is something to generally avoid anyway, IMHO.
Old 11th June 2006
  #9
Quote:
Originally Posted by phelbin
I'm not sure I understand. What is the problem with the two sharing an opamp? Please use musical terms instead of technical terms.
OK, say two band members need to share one music stand and one piece of music, but only one can see the page at a time. Meanwhile, the guy that can't see the music makes it up as he goes....

Jim Williams
Audio Upgrades
Old 12th June 2006
  #10
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Quote:
Originally Posted by BrianT
In practice, it's not that huge of a deal in my experience. And it's most pronounced when doing radical EQ, which is something to generally avoid anyway, IMHO.
I've been using my series 80 for almost two years and haven't noticed that being a problem. I can see what you're talking about. It sounds to me like it could be a big issue technically, but not necessarily a big issue musically.



Quote:
Originally Posted by absrec
Can someone please just do the test and tell me what you find?
My console is down until I get the power supply back from the tech. But if no one has done it by then (hopefully early next week), I'll be happy to do the test.
Old 12th June 2006
  #11
member no 666
 
Fletcher's Avatar
Quote:
Originally Posted by absrec
It sounds weak to me.
That's what makes the world go round... they don't sound even remotely weak to me.

Peace.
Old 21st June 2006
  #12
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I had a friend do a test on an 80. From what he told me, the console that he tested behaved differently from mine. I knew there was something not quite right going on here. If anyone out there could do this simple test and let me know what you find, it would seriously help me out.
Old 21st June 2006
  #13
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CB9182 PCB

Same results you had. I wouldn't worry too much!
Old 21st June 2006
  #14
Simple frequency sweeps with an Audio Precision will "map" out the EQ curves. Then one can compare to another, otherwise, it's a guess. Have an operator with one visit your facility and do the tests, it may show even more problems.

Jim Williams
Audio Upgrades
Old 25th June 2006
  #15
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Quote:
Originally Posted by obostic
CB9182 PCB

Same results you had. I wouldn't worry too much!
Thanks. I feel like I'm getting closer to the truth.
Old 25th June 2006
  #16
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Quote:
Originally Posted by Jim Williams
Simple frequency sweeps with an Audio Precision will "map" out the EQ curves. Then one can compare to another, otherwise, it's a guess. Have an operator with one visit your facility and do the tests, it may show even more problems.

Jim Williams
Audio Upgrades
I had a tech analyse it on his HP. He said the low mid frequency sweep only went up to about 500Hz. It's supposed to go to 1.5kHz! Listening to it, I can hear that from channel to channel, the top frequency on the low mid sweep varies slighty. On some channels, it sounds like it goes as high as 700Hz. Now, the high mid sweep starts at 1kHz. How do I eq frequencies between 500Hz and 1kHz? That's a lot of frequencies we are talking about!

-Aaron
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