Author Topic: Overwhelming bass or mic overloaded? UPDATE: PROBLEM SOLVED! (Read 6240 times)

greppson · « **on:** August 18, 2007, 09:46:43 AM »

Ran the 671 last night for the first time and love it. Great great stuff. Nice and easy.

So, first part of the show is fine, but then this happens and it just gets worse as the show goes on. Did I run too hot or what?

It's not peaking according to wavelab...

http://www.mediafire.com/?850yn52whbj

edit: switched mics last night and it still happened in the same left channel. so it's either the cables or something with the box.

----------------------------------------------------

Ok, so I recorded one more show in my trip and finally got around to messing with the waveforms in Steinberg Wavelab.

So I ran:

Audix m1290 Cardiods > Mini-quad star 20' mini XLR to standard XLR > ACM Marantz 671 @ 24/48 (on 8 NEW energizer rechargedable 2500 batts in an internal sled)

I had the 671 split automatically every hour since I tried recording at 24/48, just to be safe. For a show that was around 2.5 hours, it was 3 files, the waveforms of which can be seen below. I also did not touch the levels after the first song of the show.

AUDIO SAMPLE: First song of the show - http://www.mediafire.com/?8jnkyizhxnb (decent balance, sounds pretty good IMO)

The first waveform clearly shows that the left channel drops in volume just shy of the 1 hour mark during the show.

AUDIO SAMPLE: Level drop in left channel - http://www.mediafire.com/?bv9lkvay2z1

Not only that, but then the right channel then appears to sound "overloaded". It's weird.

AUDIO SAMPLE: Right channel overload - http://www.mediafire.com/?ci5jlxm2qdl

But, the weirdest thing is that by the end of the show, the left channel appears to have the problem.

AUDIO SAMPLE: Left channel overload - http://www.mediafire.com/?fcg0c15xzoc

I'm so confused and have no clue what in the chain seems to be having the problems.

Doug Oade suggested switching mics, switching cables, running the RCA ins and the Digi in as well, but I haven't had the time yet. When I do, I plan on trying a few different things.

Anybody got any ideas what the problem could be?

---------------------------------------------------------
UPDATE 10/17/2007

So, I got a new battery holder from marantz and it seemed to solve the problem. The only real problem I am having now is with it shutting down. I think some of the contacts are not working all the way.

Any 671 users have this problem before?

---------------------------------------------------------
UPDATE 02/13/2008

No problems with shutting down, everything seems to be working fine now.

jkbyram · « **Reply #1 on:** August 18, 2007, 10:17:32 AM »

did the batteries begin to run down?

SonicSound · « **Reply #2 on:** August 18, 2007, 10:26:19 AM »

Good Call

Quote from: jkbyram on August 18, 2007, 10:17:32 AM

did the batteries begin to run down?

greppson · « **Reply #3 on:** August 18, 2007, 10:34:03 AM »

i was running on 8 powerex 2500s and had a walmart 9v batt external plugged in as backup.

greppson · « **Reply #4 on:** August 18, 2007, 10:36:57 AM »

and the batts were all fully charged before the show...

greppson · « **Reply #5 on:** August 18, 2007, 10:40:32 AM »

audix m1290 (minis) cards > acm 671

greppson · « **Reply #6 on:** August 18, 2007, 10:43:13 AM »

show starts out fine, sounds fine, but then the left channel just goes nuts as the shoe goes on and basically drops out as the show goes on.

doesn't make any sense cause i just had the mics fixed by audix about 2 months ago and i just used them 2 weekends ago to tape the same band with no problems.

and it's the advanced concert mod 671 done by oade.

greppson · « **Reply #7 on:** August 18, 2007, 10:49:26 AM »

and blaming the batts just doesn't seem right since the walmart batt wasn't even touched (it was still displaying full charge or VERY close to full charge) when i checked it after the show.

greppson · « **Reply #8 on:** August 18, 2007, 10:59:28 AM »

one of the boards had shorted out in the mic apparently. i was getting a 6 db difference between the two...

but i've run the mics at 4-5 shows since then and no problem...

greppson · « **Reply #9 on:** August 18, 2007, 11:19:51 AM »

Yeah, the 4 or 5 shows I taped after I got them back were with the UA-5 for a few and a V3 for a few. No problems. Last night was the first time running the 671.

Wiggler · « **Reply #10 on:** August 18, 2007, 11:40:16 AM »

If you did not run the -20 mic pad on the ACM671 that might be the problem.
With many mics the pad must be used for loud pa recording with the ACM671.

greppson · « **Reply #11 on:** August 18, 2007, 11:43:13 AM »

yeah i realize now i did not use the pad, but why would that matter if i still didn't peak.. according to wavelab?

Wiggler · « **Reply #12 on:** August 18, 2007, 11:52:35 AM »

Doug asked me what mics I was running. I told him Schoeps and he told me I would need to run with the pad on.
I think if you check with the other guys on this board with Acm671's you will find they also run with the pad on for loud PA.

greppson · « **Reply #13 on:** August 19, 2007, 12:58:04 AM »

well, it wasn't the pad... it did it again tonight.

fine to start for a while, then halfway through the show gets bad and then just worse and worse.

greppson · « **Reply #14 on:** August 19, 2007, 01:22:12 AM »

so i switched the mics tonight and it happened in the same channel.

it's either the neutriks interconnects or it is the recorder. something appears to happen in the left channel when it gets hot...

i'm thinking it can't be the interconnects because i used them recently for other shows and they worked fine.

anybody got any ideas?

greppson · « **Reply #15 on:** August 25, 2007, 05:00:02 PM »

updated the first post with some waveforms and audio samples.

George · « **Reply #16 on:** August 27, 2007, 09:16:49 AM »

Quote from: greppson on August 18, 2007, 10:43:13 AM

show starts out fine, sounds fine, but then the left channel just goes nuts as the shoe goes on and basically drops out as the show goes on.

doesn't make any sense cause i just had the mics fixed by audix about 2 months ago and i just used them 2 weekends ago to tape the same band with no problems.

and it's the advanced concert mod 671 done by oade.

I had the same thing happen to me back in June at a Nelly Furtado concert. The right channel had the same exact symptoms. Ran hot, then dropped out, I clicked up the volume on the mma6000 and I eventually brickwalled the right channel about half way into the show.

Afterwards, I tried the same 9V with the mma6000 at a friends house (I was taping him playing guitar and piano for a school project) and the same symptoms popped up. I switched to a new 9V and all was well. Maybe a battery (or more) were just "bad" for you?

greppson · « **Reply #17 on:** August 27, 2007, 11:32:50 PM »

I have a hard time thinking it is the batteries though as they were brand new...

greppson · « **Reply #18 on:** August 30, 2007, 08:46:44 AM »

couldn't have been too long on the shelf as they had 3 or 4 pegs and these were the some of the last few packs.

did some testing the other night and found that one channel appeared to increase in gain throughout the recording until it was very noticeable. that was on batt power, i'm going to try it again but this time plugged into the wall and see if i get the same result. lastly, i'll probably give a 9v batt a try to see if that does the same thing.

from there, it will be trying the RCA ins.

SmokinJoe · « **Reply #19 on:** August 30, 2007, 06:41:08 PM »

What does Doug have to say about all this? If it's new, then that means there are a bunch of new components in there. Who knows if a resister that cost pennies is changing with it gets hot....

Here are some suggested "living room tests"?
- run your stereo line out > 671 line in, and see how that sounds over time. Put the same song on "repeat" for 2 hours.
When you pull that waveform up on the computer it should be even and cyclical, not creeping up.
- I have some attenuator cables I could loan you... designed for running line levels into the XLRs on an AD-20...
Then you could run line out of your stereo > attenuators > mic XLRs. Repeat above test. This is using 671 XLRs components, but not phantom power yet.
- Set your rig up, mics and all. Blast stereo speakers > mics > rig, again, same boring song and see how the waveform looks.
- Let it all cool off. Find a voltmeter, and run the rig (sound isn't important). Check over time to if the 48VDC phantom power drops off when it warms up.
If the voltage drops off, that would affect your mic's headroom. You can probably test this with a particular resistor instead of real mics... not sure what value.

I suspect at that point you will have narrowed it down a bit. Good luck.

greppson · « **Reply #20 on:** September 21, 2007, 08:44:16 AM »

Update.

I FINALLY had a night where I could set it up and let it run for a couple hours. This time, I tried it with plugged in power, phantom on, and the thing ran fine.

So, even though they are new batts (I've now got 16 batts that should be working no problem), it has to be something related to that. Was going to try the RCAs, but all I'm getting with those is a buzz, probably cause I've got different adapters and cords between the mics and the box.

In any event, Doug said he thought it MIGHT be a record level control. He said they can sometimes lose their ground. So, I've sent another email off to him and hopefully we can figure something out from there.

I just want to get the darn thing working so I can sell my 2 JB3s and w+ mod UA5. :lol

greppson · « **Reply #21 on:** October 17, 2007, 08:44:23 PM »

UPDATE 10/17/2007

So, I got a new battery holder from marantz and it seemed to solve the problem. The only real problem I am having now is with it shutting down. I think some of the contacts are not working all the way.

Any 671 users have this problem before?