Topic: Denecke AD20 gain knobs

[tchoub]

Hi ,
I'm going to make a stealth recording soon with my AD20.
The setup I am going to use is the following :
OKM II/R > A3 > AD20 > D8
During the recording, I won't be able to see the AD20 knobs. I will only check the recording levels through the DAT levels.
Therefore, since the OKM mics are matched, I would like to be able to add gain to the mics signal just by turning one gain knob of the AD20.
The problem is that the two AD20 channels are independent.
So my question is :
is there a way to make the two AD20 knobs dependent of each other ? so that when I turn only one knob of a given angle, the other knob will be turned of the exact same angle ?

Thanks ! 

[moewu4u]

Radio Sack has some small knobs that will fit nicely onto the AD20 knobs w/ a small mod. The RS knobs need to be 'sanded down' slightly so that they'll fit onto the AD20s. The RS knobs have notches on them so you can feel where you set your levels without having to look at the AD20.

Dunno about adding one gain knob to the unit; however that is a great idea. Internal would likely be the route to take though.

[tchoub]

I'm not sure if there is an elegant affordable mechanical solution.  What about adding knobs to the miniscule shafts and use a single rubber band or something around both knobs to force dependant movement? Or ideas along the same line using belts, a chain or three small gears?  It might not be easy to get a homebrew solution to work reliably. 

To get single shaft stereo volume control the unit must be modified internally. 

yes, I thought about doing that.
I tried with a piece of rubber but it didn't work.
I need something that is less "elastic". Might try with a chain.
thanks !
 

[pfife]

Keep in mind- just because the mics are matched doesn't mean that they are going to be exposed to the same volume all the time... My TL's are matched, and I usually use the meters on the JB3 to equal out the levels between the R and L - sometimes I have looked down, and seen on the UA-5 that one channel knob is turned quite a bit higher than the other...  or so it seems!

Anways- my advice, if you did this mod, would be to make sure it was something that could be "un-modded" if the situation warrants it.

[tchoub]

thanks for the advice pfife 

[pfife]

no problem dude- here's another suggestion you could try- you could get an attenuator cable w/ a volume control on it:

http://www.soundprofessionals.com/cgi-bin/gold/item/SP-ATEN-1

Set your two levels to be equal, and use the volume control on this cable to control both levels.

I have this cable that I run with the AD-20 and a battery box, and it seems to work fine.

[pfife]

BTW- are you running mics -> battery box -> AD-20 -> recorder?  If so, you'll need an attenuator of some kind anyways.

[dklein]

no problem dude- here's another suggestion you could try- you could get an attenuator cable w/ a volume control on it:

http://www.soundprofessionals.com/cgi-bin/gold/item/SP-ATEN-1

thumbs down on sticking that thing in your signal path.

BTW- are you running mics -> battery box -> AD-20 -> recorder?  If so, you'll need an attenuator of some kind anyways.

Why?  Really high output mics?  Brickwalling the AD-20? I had heard this before but my experience is otherwise.

fwiw, you can find where you need to be and just tape down the AD-20 pots in advance.  I recently stealthed a 'high security' show and didn't want to play with anything.  I took the rig out to a bar, got my levels set, gave myself a little extra headroom and put a piece of tape over the knobs so they can't change.  Then head out to your real show and record.  Unless you're changing mics, the fixed gain approach is fine if you're going to something of similar loudness.  I've pretty much found the spot that's good for just about every show I go to.  Things don't seem to vary by more than about 6 dB, which is an acceptable range for me.  Even when you have good meters going, it can be tough to predict what peaks are coming later in the night when you set levels early on.

[pfife]

Yeah - brickwalling.  I ran sp mics -> sp bb -> ad20 -> NJB3, and even with the levels turned all the way down on the AD-20, it was peaking all over the place on the NJB3.  The only time I didn't need an attenuator was when I was recording quiet music.   +17db of gain from the AD-20, I've read, and that's been my experience.

Yeah- that attenuator is a POS, but it would satisfy his needs...

[tchoub]

I'm either running
Oktava mk012 > PS2 > AD20 > D8
or OKM II/R > A3 > AD20 > D8 (for stealth recordings).

The A3 (battery module) has a -20dB pad so, with the minimum +17dB of the AD20, that makes a +3dB at minimum gain.
Since I posted my initial question, I recorded one show and found out that with the knobs of the AD20 placed at "0", my levels on the D8 were just hitting -12dB.
Therefore, I didn't have to worry about the gain knobs position.
Unfortunately, the recording is not great... very muddy and distant...
The lightness and presence that I hear with the oktava are not present at all with the OKM.

I also experienced some "distorsion" with the Oktava mk012 > PS2 > AD20 > D8 setup.
I'm not sure if this is due to the DAT or to the AD20... since this is not clipping but distorsion, I assume that the signal passed to the DAT (by the coax out of the AD20) was too hot (?).
Anyway, I now have Shure attenuators to prevent this problem.

[spyder9]

I also use the Shure attens at -10db for the below setup.  My recordings come out clean, no distortion or brickwalling.  AD20 is very managebale.  I tape w/ hypers.  I connected a set of Sennheiser ME66 shotguns to my rig and also got a good recording.  Attenuators are must for the Hypers > PS-2 > AD20 setup.  Especially, during loud shows.  Quiet shows, you could probably skip the attens, but I have yet to test that environment.  That's just my experience.