Topic: Another "gain" thread

[musicsherlock]

Does it matter at which point one adjusts the gain in a rig.  i.e.: at pre-amp, recorder, line transformer, batt box, etc. 

In my rig, I can adjust the gain at the AD-20 as well as at the recorder. I think it would be better to keep the gain set low on the recorder and set/adjust accordingly on the AD-20.

What thoughts do guys have?

[Brian Skalinder]

If you're running an AD-20, you're running a digital output from the AD-20 into a recorder.  Gain adjustments on our gear occur before the ADC, in the preamp stage.  The AD-20 is a preamp and ADC, so the gain is applied in the AD-20, the AD-20's ADC converts to digital and simply passes the signal to your recorder . Adjusting your recorder's levels will have no effect.

[hexyjones]

Does it matter at which point one adjusts the gain in a rig.  i.e.: at pre-amp, recorder, line transformer, batt box, etc. 

In my rig, I can adjust the gain at the AD-20 as well as at the recorder. I think it would be better to keep the gain set low on the recorder and set/adjust accordingly on the AD-20.

What thoughts do guys have?

Well - sure it matters...

The AD-20 has a certain circuit with it's own set of sonic charateristics...same for the recorder.

I think the general principle is to try to achive the highest gain setting as soon as possible in the chain.

For example - I use a small mixer (Yamaha MG10/2) in my rig. It has 3 places to adjust the gain.

http://www.yamahaproaudio.com/products/mixer/a_mixer/mg_series/mg10_2/

1 - the main trimmer after the mic in
2 - the channel fader(s)
3 - main fader (L/R)

Always best to get the gain right at stage "1" - Make fine adjustments at stage "2" - Drive A/D with stage "3"

If the gain is too low early in the signal path - I think you end up with a poor signal to noise ratio...you will be adding gain to a noisy signal...

[dklein]

I think the general principle is to try to achive the highest gain setting as soon as possible in the chain.

I think the general philosophy would be to add only the required gain (vs. highest)  and do it as early in the chain as possible.  This is probably what hexy is saying above  but I wasn't quite sure.  Just wanted to be sure it doesn't read as 'turn the first control to all the way up and tame it down the line'.

Try not to attenuate then boost (i.e. using attenuators on a mic level signal in front of a pre - if you have to the mics and pre are not well matched)
Try not to boost and then attenuate (cranking the gain on a pre and using attenuation down the line (say on your a>d), either in the form of line attenuators or a level control that is turned down to the point of attenuation - just turn down the gain on the first device)

[musicsherlock]

'prreciate all the responses.  Trial and error will provide the "truth".

However, glad you chimed in dklein...I am specifically enquiring about the AD-20>MD situation (>JB3 as well).  We all know it runs pretty hot, if gain knobs are turned all the way down the signal will still pass, no?  In other words, gain turned all the way down does not mean signal "off". 

Just wanted to be sure it doesn't read as 'turn the first control to all the way up and tame it down the line'.

  That's pretty much what I was doing on my first run with my current set-up.  I had the AD-20 gain set at approx 20-25% and had to play with the record volume on my MD and still recorded to hot.

[hexyjones]

Well...stop fiddling with the levels on the MD - cuz as Brian said...you are connected digitally (you must be - there doesnt appear to be any other way of connecting this device...) So...your level controls on the MD have no effect...none...

The "too hot" part must be happening in AD-20

[pfife]

Although in other threads David has said he does not have the same experience as I, but anytime I have run w/ a battery box in front of my AD-20, the levels are hot as hell on the NJB3... the only time I could record like that was with quiet music (and it turned out quite nicely).  If you have high SPL's, you'll need an attenuator.

And yes- I had mics->bb->AD-20->NJB3, and w/ no attenuator, it was peaking all over the place on the NJB3, even when I had the knobs on the AD-20 turned all the way down.

'tis my experience.

[dklein]

yeah - pfife and I have run into this already.  The only mics I've run with the AD-20 are CSBs, whose output is on the low side.  I have not found the AD-20 provides too much gain.  I was recently in a situation with the highest SPLs I can remember and I was still safe with the AD-20 at about 11 o'clock.

pfife's situation seems to prove that there are mics whose output (combined with the AD-20s minimum gain) are too much.  Too much meaning the AD-20s preamp is driving it's a>d to full scale (overs).  In that case, an attenuator b/w mics and AD-20 is the only solution...but it also says that combo is not a good one.  People may refer to the AD-20s minimum gain of 17 or 20 dB which is not terribly meaningful unless you consider where full scale occurs on the a>d (which appears to be low).

p.s.  people are assuming that sherlock's md does not offer gain adjustment on optical in....which is probably correct but...just because it's digital input doesn't mean you can't adjust the gain.  I had a soundcard that could - it's a sure sign that everything is being resampled or DSP'd.  By no means impossible...just undesirable.  You cannot get back to a good place if you start with digital overs - it's the same as cutting the amplitude on a badly clipped recording - quieter? yes, distortion gone? no.
Now that I think about it, this is the digital equivalent of brickwalling.  So if you can adjust a digital input, don't - leave it at 0 dB and get the right levels by adjusting the device feeding the recorder.

[pfife]

pfife's situation seems to prove that there are mics whose output (combined with the AD-20s minimum gain) are too much.  Too much meaning the AD-20s preamp is driving it's a>d to full scale (overs).  In that case, an attenuator b/w mics and AD-20 is the only solution...but it also says that combo is not a good one. 

True enough.  That's why the mics are for sale...