Topic: AD-500 Help

[ingsy]

I have ran the Portico > AD-500 rig a few times now, all with not so great results.  I have been keeping the AD-500 levels at zero, and have tired many different levels on the Portico.  In short, my levels have always been too low (peaks around -5.5 dB), often the peaks were all chopped off at this level, like clipped sectors except not close to 0 dB.  I did some testing, and re-read the AD-500 manual and now think it must be related to a maximum input level on the AD-500 stated as:

(front panel gain controls at minimum, fully counterclockwise)
+28dBu balanced, +24dBu ubalanced

I feel like an idiot for not figuring this out sooner.  Anyway, it seems like I will need to have levels adjusted on both the Portico preamp and AD-500 A/D to get reasonable levels.  Is this correct for all variable gain pre amps run in font of the AD-500?  Any tips/pointers on getting the perfect balance?  I would ideally like to run the Portico as hot as possible without causing the psuedo-clipping.  Thanks!

[Kindguy]

Wish I could help, I've only ran the 148 in front of the 500. Interested in hearing your tapes. Looks like a kick ass rig you've put togther.

Jeff

[todd e]

running the m248 in front of the ad500, i usually crank the knobs 3/4 on the m248 and close to full on the ad500. 
it's more of an art than a science, although some would probably argue otherwise.

you can always turn the soft-limit on and cover your ass, while turned all the way.
i'm so glad that i got this ad500 back, paul at prodig hooked it up and fixed such an old unit.

[JasonSobel]

Matt -
I'm pretty sure there's a way to calibrate the ad500 to your pre, so they both overload/clip at the same point.  that way, you can set your levels on the portico, and not worry about the ad500 overloading before digital clipping occurs.  unfortunately, I don't know the exact procedure.  I'm sure if you search around, you can find info about how to calibrate your A/D to your preamp.

[todd e]

Matt -
I'm pretty sure there's a way to calibrate the ad500 to your pre, so they both overload/clip at the same point.  that way, you can set your levels on the portico, and not worry about the ad500 overloading before digital clipping occurs.  unfortunately, I don't know the exact procedure.  I'm sure if you search around, you can find info about how to calibrate your A/D to your preamp.

here's the manual for the ad500, i'm looking to see if it mentioned calibration of the unit with a pre-amp.
http://www.taperssection.com/reference/pdf/Manual_ApogeeAD500.pdf

[ingsy]

+T to all - thanks for the help.  I am also looking into the manual to see if there is any info on calibration.  Atleast I now know that it is common to use some sort of gain on the AD-500 side.  I have also found that the Portico has a max level on output:

Maximum Output Level:     
Balanced and Floating Transformer Output from 20 Hz to 40 kHz:  +25 dBu. (Clips at just over +26 dBu)

So it appears that the Max Output level of the Portico is close to the Max input level of the AD-500 - the pseudo-clipping may be happening on the Portico side.  Given that, I wonder if this is a cailbration issue or just me being stupid for not knowing I would need to run a decent amount of gain on both boxes.  I am kicking myself for not doing a living room recording test earlier, once I did this (using various levels on the Portico and AD-500) it was easy to see that I could never get a hot signal w/out using gain on the AD-500.  Now I just need to find the perfect mix of gain on each.  Thanks again, Matt

[ethan]

I suggest reading that manual definitely. Make sure you know the difference when it's talking about dBu vs. dB. Page 27 has the discussion of Headroom and page 28 has the section on metering. Also see page for where it has picture of where the jumpers are for switching between knob and cal pot.

When I originally got an AD1K back in 02 I read my Apogee manual several times and I came away with a much better understanding of how everything works. Very informative.

-e