OT: Behringer ADA8000 gain problem

[IraSeigel]

The problem that's been mentioned here many times - of the uneven gain change in the last "click" of the ADA8000's gain knobs: any idea as to what serial numbers this problem applies to?

If the company hasn't posted any info on a recall or fix, perhaps if folks here list their serial numbers of the units with problems, maybe we can begin to get an idea of the span of time and/or units this problem applies to.

Such info would be good not only for the company (assuming they're interested), but also to help prospective buyers avoid certain units - or at least not be surprised if they buy one with the problem. As noted elsewhere, for many users this might not be a problem because it would be unusual to have to turn the knob for max gain.

Thanks,
Ira

[AudioAstronomer]

Perhaps it would be easier to simply call behringer and ask?

A distributor or reseller of behringer units may be able to offer similar information as well I suspect.

[Bob L]

I personally have 6 units and have installed probably over a hundred of these things... and have never had the problem... of course, there is so much gain in them anyway... and all of my trim controls give a smooth gain change over the range of motion, that I never ever have gone to the last click.

I just tested again now on my live rig and stepped the trim to the last setting... the increase in gain, watching the meter in SS was even and smooth. (of course the pots in my units are detented, so they do step in small increments).

Either there was a bad batch of units that got out... or, the newer current units have had a design change for the worse... I have not purchased one in a few years.

Bob L

[Dave McKenna]

Hi All,

I actually have one of these 'problem' units opened up here (S/N N0800484187, Date Code 0801). I got a schematic from here: http://www.gyraf.dk/schematics/Behri...0_analouge.PDF and started looking at the components. It turns out the 2 circuit boards have all component values and names printed right on it, so it is easy to see if the components on the board are what they are supposed to be. There is only one component different - the board lists one of the transistors in the conjugate pairs of the preamp as 2SA1316 (a Toshiba part designed for amplifying moving coil signals) but they installed 2SA970 (a standard amplifier, also Toshiba). A quick search of Digikey shows they cost about half as much in bulk... I am guessing this is the root of the problem (although I suppose it could also be the pots themselves - they have no markings on them so I can't tell if they are 5k as they should be).

WRT the design, the schematic above was done in 2004 (I assume from reading the values on the board at the time) and this one I am looking at has minor differences in the resistor values (as printed) right in front of the A/D converter - so it is virtually identical.

HTH,

Dave McKenna

[Bruce Callaway]

I bought two of these a month ago and they both have this problem however I don't think that I would ever need that much boost (ie, turnig the volume to maximum) so am not really concerned about fixing it especially if you have to start modifying board components etc.

[Ian Alexander]

I wish I'd thought about this before shipping my problem unit back. Sorry Ira. The one I got in replacement was a store display unit, so I suspect it's significantly older.

I'm glad that the problem doesn't matter to those who don't need all the gain. One of the uses here is for the talkback mic. The gain is not all the way up, but close. I wouldn't want an inadvertant adjustment to blow the talent's ears off. On the unit I sent back, the last click bumped the level about 30 dB.

[Perry]

....the last click bumped the level about 30 dB.

[UpTilDawn]

I wish I'd thought about this before shipping my problem unit back. Sorry Ira. The one I got in replacement was a store display unit, so I suspect it's significantly older.

I'm glad that the problem doesn't matter to those who don't need all the gain. One of the uses here is for the talkback mic. The gain is not all the way up, but close. I wouldn't want an inadvertant adjustment to blow the talent's ears off. On the unit I sent back, the last click bumped the level about 30 dB.

Is there an opportunity to use a talkback mic with more output? That could help some.

DanT

[Ian Alexander]

Is there an opportunity to use a talkback mic with more output? That could help some.

DanT

Thanks Dan. With the replacement ADA8000, the trim pot works as it should, with a small bump in level for each detent in the rotation. So using the very cheap dynamic for talkback works fine. And I'm happy leaving that mic sitting out collecting dust all the time, too.

[UpTilDawn]

Thanks Dan. With the replacement ADA8000, the trim pot works as it should, with a small bump in level for each detent in the rotation. So using the very cheap dynamic for talkback works fine. And I'm happy leaving that mic sitting out collecting dust all the time, too.

I know what you mean.... I do the same thing.