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Why was I getting bleed into the Bass' DI channel?

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Why was I getting bleed into the Bass' DI channel?

Postby peddlebreaker » Sun Mar 17, 2013 11:30 am

I engineered a recording session yesterday at our newly built DIY project studio, which I must say was an absolute pleasure. Finally I could get behind the desk and get to work after 8 months of intense research and labour

I had a 4 piece folk-rock band coming in to record their new E.P, but only had 8 inputs to do it.

We have built custom wall boxes in the live room that are feeding into a Soundcraft Ghost 32 mixing desk in the control room, this is then pumping directly out to 8 inputs going into Logic Pro, courtesy of a Focusrite Saffire Pro 40 I/O.

I decided to place 3 mics on the drums, using the "recorderman" technique (an AKG D112 on kick and 2 x Josephson C42's overhead), 1 mic on Acoustic Guitar (a little KM84i), 1 mic on Vocal (Neumann TLM 103), 1 mic on Electric Guitar (Groove Tubes GT44), DI'd the Bass (plugging it directly into one of the TRS jack sockets on the wall), then slapped a SE2200a on Fig 8 as a room mic, in front of the kit.

I must say that after a couple of hours tweaking the kit and adjusting the position of the mic's, we got a wonderfully warm and open sound.

BUT

For some reason, when I soloed the bass guitar after recording, it seemed to pick up all of the other instruments, especially acoustic guitar and vocals, but in a really distant, muffley kind of way, but it is quite prominent in the recording.

It's weird because it sounds as if it's microphone bleed coming in at a selective frequency, say around between 500 - 2000hz, but it was DI'd??? And every time the bass plays a note it pushes the "bled" sound back into the distance, acting almost like a limiting device?

I'm stuck, has anyone any idea what is happening here? Have we wired the TRS jacks wrong? Could it be within the software? Hmm

Any help would be greatly appreciated.

Many thanks
Ben
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Re: Why was I getting bleed into the Bass' DI channel?

Postby The Elf » Sun Mar 17, 2013 11:38 am

When you say 'DI-ed the bass', do you mean you used a DI box in the recording room, or a DI box in the control room? If you didn't use a DI box I'm wondering if this was simply cross-talk by trying to send an instrument level signal such a long way.
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Re: Why was I getting bleed into the Bass' DI channel?

Postby ronmac » Sun Mar 17, 2013 11:43 am

I am not sure how you are routing through the desk, but you likely need to check to make sure the buss sent to the bass track doesn't have something else routed to it in error.
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Re: Why was I getting bleed into the Bass' DI channel?

Postby Mike Stranks » Sun Mar 17, 2013 12:22 pm

The Elf wrote:When you say 'DI-ed the bass', do you mean you used a DI box in the recording room, or a DI box in the control room? If you didn't use a DI box I'm wondering if this was simply cross-talk by trying to send an instrument level signal such a long way.
Yup! We need to know more about this "Di-ing the bass" and what exactly you did.

... and just to check... you weren't getting any crosstalk elsewhere - only on this channel?
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Re: Why was I getting bleed into the Bass' DI channel?

Postby damoore » Sun Mar 17, 2013 1:10 pm

Some questions:

Was it a conventional bass or something exotic? Does the level of the leakage change or is it fixed?

- rational: If exotic perhaps the bass itself acted as a mic. If so probably there would be noticable changes in the level or quality as the player moved.

Were you running any pre-amps in the room and if so on what? Have you checked for cross-talk on the cabling?

- rational: If just mics at mic levels other than the bass, they would be lower level. So if the problem is crosstalk in your cabling, it should be easy to detect by feeding line level down one pair and listening on another.

What sort of DI were you using on the bass?

- rational: This could change levels, making the signal more susceptible to crosstalk. If it was a tube DI then there is the additional possibility of tube microphony in the unit itself. Which leads to one more question:

How were the musicians monitoring?

- rational. If on headphones/in-ears then the tube microphony possibility is less likely. If you were feeding line level or head-phone level signals back down the cabling then that would be the prime candidate for a source of cross-talk in the cabling.
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Re: Why was I getting bleed into the Bass' DI channel?

Postby ef37a » Sun Mar 17, 2013 2:12 pm

"Finally I could get behind the desk and get to work after 8 months of intense research and labour"

But did you spend a day or so with an oscillator, scope and millivoltmeter checking all the lines out for response, phase and crosstalk?

Did the mixer come with/go back for a specification check?

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Re: Why was I getting bleed into the Bass' DI channel?

Postby Daniel Drummond » Sun Mar 17, 2013 2:18 pm

Once I recorded an acoustic guitar in a live show, through its internal pickup and it also picked up a tiny distant bit of everything else. I suppose pickups can do that if the volume is really high as I see no reason for crosstalk on the equipment I was using (I mean, it doesn't crosstalk when I record in the studio).
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Re: Why was I getting bleed into the Bass' DI channel?

Postby peddlebreaker » Sun Mar 17, 2013 2:52 pm

Hi guys, thank you so much for your replies.

I can tell you that I didn't actually use a DI box for the bass as such, so I lied , I just plugged it straight into the wallbox which was TRS jack socket.

I have to really crank up the gain on the channel as the bass player played really softly. I think it was a relatively cheap guitar, and I am certain it did not have any microphone built in or anything that exotic

The distance from the wallbox to the desk is approximately 5 metres.

The only preamp I had on in the live room was that of the Groove tubes, but that was plugged in to the other wallbox on the other side of the room.

I think by the sound of it, it seems that its more than likely cross-talk, but this is something that I am not familiar with. How can I eliminate this? It has meant that we are going to have to re-capture bass on at least 3 of the tracks that we recorded.

Thanks again for your help.
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Re: Why was I getting bleed into the Bass' DI channel?

Postby The Elf » Sun Mar 17, 2013 3:06 pm

peddlebreaker wrote:I can tell you that I didn't actually use a DI box for the bass as such, so I lied , I just plugged it straight into the wallbox which was TRS jack socket.

There's your answer. Invest in a decent DI box for the future, plug this into a mic channel and it should be problem solved.
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Re: Why was I getting bleed into the Bass' DI channel?

Postby ef37a » Sun Mar 17, 2013 3:25 pm

The Elf wrote:
peddlebreaker wrote:I can tell you that I didn't actually use a DI box for the bass as such, so I lied , I just plugged it straight into the wallbox which was TRS jack socket.
There's your answer. Invest in a decent DI box for the future, plug this into a mic channel and it should be problem solved.

Not so sure Elf. I think the problem was a cranked channel on the mixer causing crosstalk in that. Interchannel mixer crosstalk might be no better than -90dBu or so and we no longer have that nice tape hiss to cover it up!

OP, where is the bleed, ref 0dBFS?

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Re: Why was I getting bleed into the Bass' DI channel?

Postby The Elf » Sun Mar 17, 2013 4:30 pm

ef37a wrote:
The Elf wrote:
peddlebreaker wrote:I can tell you that I didn't actually use a DI box for the bass as such, so I lied , I just plugged it straight into the wallbox which was TRS jack socket.
There's your answer. Invest in a decent DI box for the future, plug this into a mic channel and it should be problem solved.

Not so sure Elf. I think the problem was a cranked channel on the mixer causing crosstalk in that.
But cranked due to introducing an unbalanced instrument-level signal into a balanced line-level input?
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Re: Why was I getting bleed into the Bass' DI channel?

Postby ef37a » Sun Mar 17, 2013 5:40 pm

Hmm? You are thinking E that the balanced, shielded, low level mic lines are coupling into the medium impedance unbalanced bass cable?

Well maybe but I would put my money on interbus crosstalk in the mixer.

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Re: Why was I getting bleed into the Bass' DI channel?

Postby Sam Inglis » Mon Mar 18, 2013 9:24 am

Could it have been a microphonic pickup on the bass itself?
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Re: Why was I getting bleed into the Bass' DI channel?

Postby Guy Johnson » Mon Mar 18, 2013 10:12 am

Pug the bass in on the channel/line it was on. Get someone to talk into pickup. See what you get.

Thinking how low the bass signal was, and the high line-level headphone feed signals are, relatively (BTW, are the headphone amps in the live room, or are you routing even hotter signals from the control room?) ... I'd guess crosstalk. Try a nice Orchid DI on the bass, DIs are the things missing in your set-up.
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Re: Why was I getting bleed into the Bass' DI channel?

Postby James Perrett » Mon Mar 18, 2013 10:29 am

peddlebreaker wrote:
It's weird because it sounds as if it's microphone bleed coming in at a selective frequency, say around between 500 - 2000hz, but it was DI'd??? And every time the bass plays a note it pushes the "bled" sound back into the distance, acting almost like a limiting device?

First, this doesn't sound like electrical crosstalk which normally sounds like sounds above 2kHz. If the bleed disappears when the bass plays a note there must be a compressor in the system. If you find the compressor then you know for sure that the noise is being introduced before it.

I'd suspect that either the bass has a built in compressor of some sort or the bass player was using a compressor pedal and that the real problem is with loose windings in the bass pickups which are picking up ambient noise.

If you are using a decent desk and an active bass (or an active pedal between the bass and desk) then there's no problem plugging an unbalanced instrument into a line input. While using a DI is considered best practice, a decent line input will have enough gain to accommodate a bass guitar.

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Re: Why was I getting bleed into the Bass' DI channel?

Postby peddlebreaker » Mon Mar 18, 2013 11:36 am

Hello all, thank you again for your replies.

The bass player was not using a compressor of anykind, hmm?

Anyhow, I think we need to invest in a couple of decent DI boxes.

I am afraid that we are clued up on millivolts or use multimeters etc. I think we need to do some more research as I put it

Thanks again for your suggestions and knowledge, it's really helped us out!

Ben
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Re: Why was I getting bleed into the Bass' DI channel?

Postby damoore » Mon Mar 18, 2013 2:09 pm

peddlebreaker wrote:Anyhow, I think we need to invest in a couple of decent DI boxes.


At least! If you ever want to record stereo keyboards and bass at once, you will need a minimum of three.

The other problem with plugging the bass directly into the wall is that now you have a nice long aerial which can introduce RF into all your inputs.
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Re: Why was I getting bleed into the Bass' DI channel?

Postby James Perrett » Mon Mar 18, 2013 2:46 pm

peddlebreaker wrote:
The bass player was not using a compressor of anykind, hmm?

From your description of the problem it sounds like something was acting like a compressor. Any chance of posting a sample of the problem somewhere?

While some will suggest you need a DI, if the rest of your setup is wired correctly, you can often get away without it. I'm really not sure that the lack of a DI box is your problem.

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Re: Why was I getting bleed into the Bass' DI channel?

Postby Hugh Robjohns » Mon Mar 18, 2013 3:01 pm

The DI box might have circumvented the problem by using a mic line instead, and at least they appeared to be working normally. And that would be the 'tarditional' way of working... but that assumes the connection format was the problem, and while it might have been, I'm not entirely convinced.

There is clearly an unusual problem here somewhere, and it would pay to get to the bottom of it to avoid any future problems.

I agree with James that, from the original description, this doesn't sound like a console crosstalk problem.

It could well be a bass guitar problem, with microphonic pickups. This kind of thing wouldn't necessarily be apparent in normal playing at gigs or rehearsals, but would become obvious when recording.

It could also be an issue of crosstalk in the stage box/studio wiring -- especially if high level headphone signals were being routed back in adjacent cables to the bass line cable.

But the description of an auto-gain/compression effect in the way the background noise comes and goes between bass notes is troubling, and I'd suggest checking the whole signal path to see if there was a compressor -- or something behaving like a compressor -- somewhere.

First off, though, I'd invest in a cable tester and have amethodical work through all your studio/control room mic and line connections to check eveything is wired as it should be.

H
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Re: Why was I getting bleed into the Bass' DI channel?

Postby James Perrett » Mon Mar 18, 2013 3:51 pm

One more thought - is it an active bass? If so, check the state of the battery.
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Re: Why was I getting bleed into the Bass' DI channel?

Postby peddlebreaker » Thu Mar 21, 2013 8:59 am

Hi there all, sorry for the late reply.

I would like to upload a sample of the Bass Guitar so that you can hear what I am talking about What would be the best way of doing that? Soundcloud?

Cheers
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Re: Why was I getting bleed into the Bass' DI channel?

Postby James Perrett » Thu Mar 21, 2013 9:46 am

Soundcloud would be fine.
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