Topic: what happened here? CA omnis and nasty low end

[SmokinJoe]

It wasn't a loud thumpy show...  In the above picture, those bug antenna mics around the LSD2 are my stock AT853s... which are known to overload easily, and they sound fine... http://www.archive.org/details/dtb2007-11-13.at853.flac16f

I have run CA cards > ST9100 > H120 a couple of times.  I think I set the gain on the ST9100 about half way, then set iRiver gain to +15db with the auto AGC so it will ratchet down to whatever is required... typically ends up around +5.  In other words, the iRiver is applying about 5db gain.  If the iRiver ratchets down to negative DBs then it is applying attenuation, which means the signal coming in is too hot, and you start to hit invisible walls signal-wise and get distortion.  Better to let the iRiver apply some gain.  Letting the iRiver apply too much gain will generate some hiss, so the trick is to find that happy medium.

While I agree with Chris's statements about mounts, I don't think that was the problem here.  It's a nice mellow show at a nice opera house... it's not Ozzfest.  I tend to agree with battery issue or too much boost out of the preamp.

[Church-Audio]

It wasn't a loud thumpy show...  In the above picture, those bug antenna mics around the LSD2 are my stock AT853s... which are known to overload easily, and they sound fine... http://www.archive.org/details/dtb2007-11-13.at853.flac16f

I have run CA cards > ST9100 > H120 a couple of times.  I think I set the gain on the ST9100 about half way, then set iRiver gain to +15db with the auto AGC so it will ratchet down to whatever is required... typically ends up around +5.  In other words, the iRiver is applying about 5db gain.  If the iRiver ratchets down to negative DBs then it is applying attenuation, which means the signal coming in is too hot, and you start to hit invisible walls signal-wise and get distortion.  Better to let the iRiver apply some gain.  Letting the iRiver apply too much gain will generate some hiss, so the trick is to find that happy medium.

While I agree with Chris's statements about mounts, I don't think that was the problem here.  It's a nice mellow show at a nice opera house... it's not Ozzfest.  I tend to agree with battery issue or too much boost out of the preamp.

I think your right. I just saw the mounts and wanted to make sure when he wanted to tape again he should pay some close attention to the mounting of my omni mics.. They are pretty good for not picking up to much vibration. But I wanted to rule out everything.

Good point about the gain issue.

Chris

[Church-Audio]

Yea, sounds like what happened was that you overloaded the iRiver's pre with too much gain coming out of the CA pre. Something like that wouldn't show up on the iRiver's meters. Start with the CA pre to unity gain, and set gain from the recorder first before using the CA preamp. You want to use the least amount of gain possible from the CA pre.

Um actually since I am the one that designed it you want to use the most amount of gain from my preamp just watch the clip lights....  

[Will_S]

I think what Alchemy meant is that you don't want the preamp to be supplying so much gain that the iRiver has to be set to negative gain to compensate, as the iRiver really can't attenuate an incoming signal and if run in the negative gain range will clip while the meters still indicate good levels.

So, good practice would be:
Set the iRiver's gain to 0dB.
Crank the preamp as high as needed to get the levels you want.
If levels are still too low with the preamp cranked all the way, start adding gain with the iRiver.  But never run the iRiver at negative gain.  Turn down the preamp instead.

Alternatively, if you use the safety setting in Rockbox, you could set the iRiver to ~ +6dB and then crank the preamp to the needed level.  Then if things get a bit louder, the iRiver's gain will be turned down as needed.

Safety won't work if you start out at 0 dB - it will lower the iRiver's gain but the incoming signal will still be strong enough to clip the A>D.

[Alchemy]

Yea, sounds like what happened was that you overloaded the iRiver's pre with too much gain coming out of the CA pre. Something like that wouldn't show up on the iRiver's meters. Start with the CA pre to unity gain, and set gain from the recorder first before using the CA preamp. You want to use the least amount of gain possible from the CA pre.

Um actually since I am the one that designed it you want to use the most amount of gain from my preamp.... 

Actually, what I wrote was perfectly good advice. Start at unity on the iRiver and boost with your pre to get decent levels, but no so much that it overloads the iRiver's pre.

Chris, this is the second time this has happened. Why do you take everything I write so personally? My intention is to help someone out- making you angry was not my intention at all.

[Church-Audio]

Yea, sounds like what happened was that you overloaded the iRiver's pre with too much gain coming out of the CA pre. Something like that wouldn't show up on the iRiver's meters. Start with the CA pre to unity gain, and set gain from the recorder first before using the CA preamp. You want to use the least amount of gain possible from the CA pre.

Um actually since I am the one that designed it you want to use the most amount of gain from my preamp.... 

Actually, what I wrote was perfectly good advice. Start at unity on the iRiver and boost with your pre to get decent levels, but no so much that it overloads the iRiver's pre.

Chris, this is the second time this has happened. Why do you take everything I write so personally? My intention is to help someone out- making you angry was not my intention at all.

I am not angry but your advice was not correct for my product.. So I corrected you.. since I built it I know.

[vanark]

Yea, sounds like what happened was that you overloaded the iRiver's pre with too much gain coming out of the CA pre. Something like that wouldn't show up on the iRiver's meters. Start with the CA pre to unity gain, and set gain from the recorder first before using the CA preamp. You want to use the least amount of gain possible from the CA pre.

Um actually since I am the one that designed it you want to use the most amount of gain from my preamp.... 

Actually, what I wrote was perfectly good advice. Start at unity on the iRiver and boost with your pre to get decent levels, but no so much that it overloads the iRiver's pre.

Perhaps that is what you meant to say, but your original post was pretty unclear to that point.

[Church-Audio]

Yea, sounds like what happened was that you overloaded the iRiver's pre with too much gain coming out of the CA pre. Something like that wouldn't show up on the iRiver's meters. Start with the CA pre to unity gain, and set gain from the recorder first before using the CA preamp. You want to use the least amount of gain possible from the CA pre.

Um actually since I am the one that designed it you want to use the most amount of gain from my preamp.... 

Actually, what I wrote was perfectly good advice. Start at unity on the iRiver and boost with your pre to get decent levels, but no so much that it overloads the iRiver's pre.

Perhaps that is what you meant to say, but your original post was pretty unclear to that point.

Hence the reason for my editing my original post and softening it somewhat Funny thing is I did it way before there was any response to my original post. So I would say its moot now.

[bugg100]

In my experience, (with the same gear ) I find the below advice (Will_s's) to be spot on for a good level with the pre.  I have had the same problem with audio - mushy bass with mostly everything else sounding pretty ok. 

Checking levels on the pre battery and finding it low.  New battery, similar show (same room, same bass, etc.) came out perfect.

I think what Alchemy meant is that you don't want the preamp to be supplying so much gain that the iRiver has to be set to negative gain to compensate, as the iRiver really can't attenuate an incoming signal and if run in the negative gain range will clip while the meters still indicate good levels.

So, good practice would be:
Set the iRiver's gain to 0dB.
Crank the preamp as high as needed to get the levels you want.
If levels are still too low with the preamp cranked all the way, start adding gain with the iRiver.  But never run the iRiver at negative gain.  Turn down the preamp instead.

Alternatively, if you use the safety setting in Rockbox, you could set the iRiver to ~ +6dB and then crank the preamp to the needed level.  Then if things get a bit louder, the iRiver's gain will be turned down as needed.

Safety won't work if you start out at 0 dB - it will lower the iRiver's gain but the incoming signal will still be strong enough to clip the A>D.

The only difference I have with the above, is that I find it OK to run the iRiver at slightly negative levels with no ill effect. 

In closing, always check your battery before heading out.  Set your levels as above. Have a good time.  In that order!

Joe

[run_run_run]

For the mount I rolled up some duck tape so it springy, set the mics on it and wrapped a piece over to protect them from falling.  I will track out CA Cards > 9100 > JB3 on a low stand just behind,  Joe let me use Cards and pre. I am pretty sure they where fine.