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Op-amp gain trouble

Discussion board for Mackie's d8b Digital Console users.

Re: Op-amp gain trouble

Postby Guitarik » Sun Jun 14, 2015 8:18 am

channels 13-24 are only line level inputs?
Last edited by Guitarik on Sun Jun 14, 2015 10:49 am, edited 1 time in total.
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Re: Op-amp gain trouble

Postby High C Double G » Sun Jun 14, 2015 9:40 am

Hi,

There are a lot of inputs on the d8b... On Fader Bank 1, Channels 1-12 have a integral microphone preamplifier for microphones with a trim control - Chapter 1 Page 7 in my d8b v5.1 manual.

Do you have your copy of the manual?

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Re: Op-amp gain trouble

Postby Guitarik » Sun Jun 14, 2015 10:49 am

I see Ch1P14 uses line levels on inputs 13-24. do you use preamps? if so what do you use for them?
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Re: Op-amp gain trouble

Postby High C Double G » Mon Jun 15, 2015 12:48 am

Hi,

The block diagram on Ch1Pg14 shows the difference between channels 1 through 12 compared to channels 13 through 24. Channels 1-12 have already a pre-amplifier to boost the input signal for microphones and channels 13-24 do not have the pre-amplifier.

Any thing that will boost (match) the input signal to line level (+4) will work to get a strong level on channels 13-24 - a microphone pre-amplifier is the best solution for microphones. There are many products available that will help to match the signal that might not be a professional +4 signal to what the d8b wants to see which is +4.

If you are not recording everything at once, you can route the channel inputs 1-12 pretty much anywhere you want - it is a incredibly flexible mixer - it is all in the manual.

Hope this helps,
HCDG
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Re: Op-amp gain trouble

Postby Guitarik » Tue Jul 14, 2015 11:39 pm

I see.. I assumed the mic/ line switches on 1-12 were merely pads and all the pre-amps were uniform. I dont think i ever came across a mixer that had only line level on 1/2 the preamp inputs.
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Re: Op-amp gain trouble

Postby Guitarik » Sun Jul 19, 2015 10:02 pm

Still the same problem... I ran a line-level input and the gain is still weak -15 at full gain on the HA. Something is not right.
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Re: Op-amp gain trouble

Postby Crash » Mon Jul 20, 2015 1:33 pm

Guitarik wrote:Still the same problem... I ran a line-level input and the gain is still weak -15 at full gain on the HA. Something is not right.


What did you use as your line input device?
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Re: Op-amp gain trouble

Postby Guitarik » Mon Jul 20, 2015 6:36 pm

I'm using a motif and I had it at max volume
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Re: Op-amp gain trouble

Postby Crash » Mon Jul 20, 2015 7:49 pm

Guitarik wrote:I'm using a motif and I had it at max volume


Line and instrument out are different. I am guessing the motif is a keyboard? Try plugging in the output of a cd player or an F/X box (Not stomp box) and see what you get. If you have an external preamp, plug your motif into that to get it up to what channels 13-24 are looking for. I think your d8b is working as it should from I have read here.
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