Author Topic: what happened here? CA omnis and nasty low end (Read 5662 times)

run_run_run · « **on:** February 01, 2008, 03:25:30 PM »

Way back in november I ran split omnis on the baloney rail for DTBs and it came out really bad

Photo of the mics

Duck tape for the win

short sample
http://download.yousendit.com/F70409245CB0BA36

Church Audio Omnis > Church Audio ST-9100 > Iriver iHP-100

ilduclo · « **Reply #1 on:** February 01, 2008, 04:09:44 PM »

check your batteries in any amp/preamp/battery box?

run_run_run · « **Reply #2 on:** February 01, 2008, 04:45:03 PM »

Quote from: ilduclo on February 01, 2008, 04:09:44 PM

check your batteries in any amp/preamp/battery box?

they where fine before the show

bugg100 · « **Reply #3 on:** February 01, 2008, 06:57:02 PM »

Yeah, but what is fine? I find that I need to check voltage w/ DMM to minimize battery waste. The louder the show the more important it is to have no less than 8v or so.... At lower than that, i found that you get distortion on the low end. I hate 9 volt batteries.

run_run_run · « **Reply #4 on:** February 01, 2008, 07:01:49 PM »

Quote from: bugg100 on February 01, 2008, 06:57:02 PM

Yeah, but what is fine? I find that I need to check voltage w/ DMM to minimize battery waste. The louder the show the more important it is to have no less than 8v or so.... At lower than that, i found that you get distortion on the low end. I hate 9 volt batteries.

I see, I don't really recall its been awhile

Alchemy · « **Reply #5 on:** February 01, 2008, 10:45:19 PM »

It sounds like the levels coming out of the pre were too hot for the iRiver. Even though it may have looked OK on the level meters, it was too much for the iRiver to handle. Was the CA pre doing most of the gain work?

Belexes · « **Reply #6 on:** February 02, 2008, 02:17:50 AM »

I think you may have overloaded the pre. I got a Tool recording that sounded like this.

run_run_run · « **Reply #7 on:** February 02, 2008, 11:22:53 AM »

Quote from: Alchemy on February 01, 2008, 10:45:19 PM

It sounds like the levels coming out of the pre were too hot for the iRiver. Even though it may have looked OK on the level meters, it was too much for the iRiver to handle. Was the CA pre doing most of the gain work?

yeah it was +20

Belexes · « **Reply #8 on:** February 02, 2008, 11:41:25 AM »

Quote from: run_run_run on February 02, 2008, 11:22:53 AM

Quote from: Alchemy on February 01, 2008, 10:45:19 PM
It sounds like the levels coming out of the pre were too hot for the iRiver. Even though it may have looked OK on the level meters, it was too much for the iRiver to handle. Was the CA pre doing most of the gain work?
yeah it was +20

Do you have the ST-9100 with the red LED that shows if it's hot/clipping? I don't think early versions of the pre had this, but version 3 does and is extremely helpful when dealing with a high SPL situation.

run_run_run · « **Reply #9 on:** February 02, 2008, 11:54:42 AM »

it has a light, honestly I was just checking the irivers meter

Alchemy · « **Reply #10 on:** February 02, 2008, 02:32:27 PM »

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.

Belexes · « **Reply #11 on:** February 02, 2008, 03:52:54 PM »

Start at about 11 'O Clock on that pre. That's unity and then you just keep turning it up until you get the gain you need from the pre, but without overloading it.

taylordb · « **Reply #12 on:** February 03, 2008, 07:19:14 AM »

I'm a little confused from the last 2 posts. If you can overload the iRiver's pre with too much gain coming from the CA pre....and it won't show up on the iRiver's meters, how can you start at unity gain on the CA and just keep turning it up until you get the gain you need, but without overloading it.....if overloading it won't show up on the iRiver's meters?

Does my question make sense.

Belexes · « **Reply #13 on:** February 09, 2008, 03:09:09 PM »

Quote from: taylordb on February 03, 2008, 07:19:14 AM

I'm a little confused from the last 2 posts. If you can overload the iRiver's pre with too much gain coming from the CA pre....and it won't show up on the iRiver's meters, how can you start at unity gain on the CA and just keep turning it up until you get the gain you need, but without overloading it.....if overloading it won't show up on the iRiver's meters?

Does my question make sense.

You can overload at the pre and the meters on the recorder won't show it. The signal into the recorder will be a hot distorted mess. I start at unity on the pre and on the recorder and then add gain on the CA pre until I am seeing satisfactory levels, then double-check the CA pre to make certain I am not overloading it.

With the CA pre, you can get +20 dB, which is really uncalled for at a loud concert. I learned my lesson at Tool!

Church-Audio · « **Reply #14 on:** February 09, 2008, 04:13:50 PM »

Quote from: run_run_run on February 01, 2008, 07:01:49 PM

Quote from: bugg100 on February 01, 2008, 06:57:02 PM
Yeah, but what is fine? I find that I need to check voltage w/ DMM to minimize battery waste. The louder the show the more important it is to have no less than 8v or so.... At lower than that, i found that you get distortion on the low end. I hate 9 volt batteries.
I see, I don't really recall its been awhile

Try to support my mics by the cable ends do not have them resting on a hard surface because you can end up with vibration that is picked up and reproduced by the microphone as distortion

You should use tape on the heat shrink side of the mics so that they are sticking out from your clamps.. Or build a elastic shock mount

Don't forget to give me the plans

I have an idea on how to build one but it involves castration bands.....

Also when using my omni mics you must back off on the gain just a tad to say 75% instead of 100% because my omni mics are hotter then my cards.

SmokinJoe · « **Reply #15 on:** February 09, 2008, 04:44:04 PM »

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 · « **Reply #16 on:** February 09, 2008, 06:28:24 PM »

Quote from: SmokinJoe on February 09, 2008, 04:44:04 PM

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 · « **Reply #17 on:** February 10, 2008, 02:44:40 PM »

Quote from: Alchemy on February 02, 2008, 02:32:27 PM

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 · « **Reply #18 on:** February 10, 2008, 03:53:04 PM »

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 · « **Reply #19 on:** February 10, 2008, 04:14:18 PM »

Quote from: Church-Audio on February 10, 2008, 02:44:40 PM

Quote from: Alchemy on February 02, 2008, 02:32:27 PM
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 · « **Reply #20 on:** February 10, 2008, 04:55:03 PM »

Quote from: Alchemy on February 10, 2008, 04:14:18 PM

Quote from: Church-Audio on February 10, 2008, 02:44:40 PM
Quote from: Alchemy on February 02, 2008, 02:32:27 PM
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 · « **Reply #21 on:** February 10, 2008, 05:34:53 PM »

Quote from: Alchemy on February 10, 2008, 04:14:18 PM

Quote from: Church-Audio on February 10, 2008, 02:44:40 PM
Quote from: Alchemy on February 02, 2008, 02:32:27 PM
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 · « **Reply #22 on:** February 10, 2008, 05:37:41 PM »

Quote from: vanark on February 10, 2008, 05:34:53 PM

Quote from: Alchemy on February 10, 2008, 04:14:18 PM
Quote from: Church-Audio on February 10, 2008, 02:44:40 PM
Quote from: Alchemy on February 02, 2008, 02:32:27 PM
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 · « **Reply #23 on:** February 11, 2008, 12:03:17 AM »

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.

Quote from: Will_S on February 10, 2008, 03:53:04 PM

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 · « **Reply #24 on:** February 11, 2008, 10:54:18 AM »

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.