Neve Portico 5016 DI Buzz Problem- Gain Staging???

Posted: Tue Oct 14, 2008 9:15 am

Hi there

I thought I would try something new to me with my Neve Portico 5016 yesterday and record 2 bass tracks simultaneously. The 5016 is a 2 channel unit with 1xMic Pre and 1x DI/Line Level.

My set up was:

1. My Fender Jazz Bass going into the DI then going into my RME Multiface 2 then into Sonar 7 PE.

2. The Fender Jazz Bass signal (unaltered) simlutaneously being routed from the THRU ouput of the 5016 to my modest Fender Rumble 15 watt combo. This then having an SM57 pointed at the speaker cone going into my MIC PRE side of the 5016, this also going into the RME Multiface 2 etc.

When I tried to do the above, I seemed to get major noise issues with a constant buzz coming through the Fender Rumble combo which would get louder as I raised the volume. It also happened with a Marshall amp I have too. Therefore, may rule out the amps at this point. I drove myself mad trying to get rid of this buzz which at times sounded as though it had a clock ticking through it. GGrrrr.

I am not an expert on gain staging. Therefore, if this is the issue I would be grateful for advice in solving the issue. I will describe a few things below:

My Bass guitar volume knobs were turned all the way up as this is something that I was always told to do. Was this good advice as it ties in with what I have read regarding that good gainstaging requires that you get as much hot signal into the signal chain as early as possible?

Even with my DI on the 5016 turned all the way down, the Fender Rumble buzzed. This was also the case with the MIC PRE turned all the way down also having the SM57 disconnected from the 5016. Therefore, I got the buzz from going into the 5016 (turned all the way down), then from the THRU>>>Fender Rumble. I am just totally stumpted as to why this has happened.

I tried the Fender Rumble in another room to no avail. Even my mouse on the mousepad was making sounds in the buzzing. If any louder I would have been able to mimic the record scratching breakdancing stuff from the 1980s using my mouse...lol

I tried switching to other guitar cables. Incidentally, I was using unbalanced mono cables from the Bass>>>5016 DI and from the 5016 THRU>>>Fender Rumble as the 5016 stated that the THRU takes an unnaffected signal to an external amplifier.

The Ground Lift Switch on the 5016 marginally helped. However, this tended to affect the DI track. Therefore, everything was now buzzing. In fact, the only way I can get rid of the buzzing is to disconnect the THRU output and unswitch the Ground Switch and solely use the DI.

I do not think the issue is the 5016 or Fender Rumbles proximity to other gear as I also tried thing quite spaced out.

Is there sonething I am missing regarding the intended use of the 5016 or something? This is what the manual says:

Quote:

THRU - An output Jack is provided on the front panel that replicates the D.I. input signal, appearing as an unbalanced source. This THRU Output may be used to feed an external loudspeaker amplifier. (Use a T.R.S. Tip-Ring-Sleeve or a single pole Plug).

Quote:

Ground Isolation Push-Button switch - If hum or buzz should be heard, which might be caused when a separately powered and grounded guitar or instrument is connected, a Push-Button on the front panel lifts the Portico 5016 D.I. internal ground rail from the TRS circuit to break a potential loop. Such Loops are formed when separate grounded utility power outlets are used, for example on the stage for mixing or amplifying equipment.

Any advice on sovling this would be gratefully appreciated.

Regards

Lid.

Posted: Tue Oct 14, 2008 10:09 am

[quote=\"lostindundee\"]I tried the Fender Rumble in another room to no avail. Even my mouse on the mousepad was making sounds in the buzzing. If any louder I would have been able to mimic the record scratching breakdancing stuff from the 1980s using my mouse...lol [/quote]

That is because you have the gain cranked on your amp and the unbalanced instrument cable is working like an antenna.
[quote=\"lostindundee\"]The only way I can get rid of the buzzing is to disconnect the THRU output and unswitch the Ground Switch and solely use the DI. [/quote]

This tells you that the ground problem is between your DI and your amp. On a DI the ground from the input to the Thru is always tied. The ground lift will disconnect the ground from the input to the output. (The front and the back of the box) Try switching the cables on the thru and output. Or use a passive DI (or active with phantom power) instead of the thru.

Posted: Tue Oct 14, 2008 10:42 am

Thanks for a speedy reply GekoMusic.

I should have mentioned that the amp volume was merely raised just 0.5 cm from zero. If all the way down was say 7 on a clock face, then I am taking it to around 8 and getting the appaling noise. Therefore, the amp is bearly being brought into play.

My bass was cranked up. The DI was cranked all the way down at one point with the amp set as detailed above.

So... is it the unbalanced cable from the THRU that is the problem then? I will try several different cables tomorrow to see if it makes a difference.

I cannot switch the cables on the THRU and Output as the Output is XLR.

When you say - Or use a passive DI (or active with phantom power) instead of the thru.

Do you mean ditch using my 5016 in favour of another DI. How would this work seeing that my aim is still to record 2 distinctly different tracks with one performance? Wouldn\\\\\\\'t this require a DI with another THRU?

Thanks GekoMusic.

Lid

p.s. Is anyone else on the forum having the strange issue with apostrophes and quote marks turning to back slashes and ruining quotes etc?

Posted: Tue Oct 14, 2008 11:25 am

lostindundee wrote:

My bass was cranked up. The DI was cranked all the way down at one point with the amp set as detailed above.

OK I thought you had the amp cranked, and the bass down... Not sure on that one.

lostindundee wrote:

So... is it the unbalanced cable from the THRU that is the problem then? I will try several different cables tomorrow to see if it makes a difference.

The type of cable shouldn't make a difference because the signal from the bass is unbalanced. The output will be balanced, but the thru will be whatever the input is. It seems that the input is coupled to the ground of the DI box, and that is not agreeing with your amp. You can try plugging both into the same outlet or power strip. Use a XLR to 1/4 cable to connect the output of the DI to the amp.

edit: fixed the //// problem.

Posted: Tue Oct 14, 2008 11:52 am

GeckoMusic Wrote: The type of cable shouldn\'t make a difference because the signal from the bass is unbalanced. The output will be balanced, but the thru will be whatever the input is. It seems that the input is coupled to the ground of the DI box, and that is not agreeing with your amp. You can try plugging both into the same outlet or power strip. Use a XLR to 1/4 cable to connect the output of the DI to the amp.

Thanks GeckoMusic

I understand everything you wrote regarding the input on the DI (an therefore, the THRU) not agreeing with both my amps. This is terrible. The DI input signal and THRU should be compatable with an amp. I wonder if anyone else has this problem with their 5016?

Regarding your advice on pluging them both into the same outlet, I\'m not too sure what you mean by the same outlet or power strip? What do you mean specifically?

Are you suggesting I test and compare both signals on another amp taking an XLR>>>1/4 balanced cable from the DI Ouput to an amp or something else?

Regards

LiD

Posted: Thu Oct 16, 2008 7:07 am

Same power strip to avoid ground loops.

Check your cable too Wink

Posted: Thu Oct 16, 2008 11:11 am

Hi there

Thanks to the pair of you for your help. I've tried both appliances on the same and different power strips. I've also tried different combinations of the 20+ or so cables I have.

Someone else has suggested this:

http://www.ebtechaudio.com/humxdes.html

Any thoughts? Must be worth a shot I guess.

Regards

Lid

Posted: Fri Oct 17, 2008 1:04 am

GeckoMusic wrote:

Try switching the cables on the thru and output. Or use a passive DI (or active with phantom power) instead of the thru.

Ah....do you mean use a passive DI between the THRU and the Amp? One with a ground lift perhaps?
http://www.smartsounddirect.com/rolls-db-25-matchbox-passive-di-box-with-ground-lift-23-p.asp

This way my set up going into my 5016 DI (into my DAW) and my THRU (into my Amp) would remain except for slotting the passive DI in between the THRU and Amp.

Is this what you mean?

LiD

Posted: Fri Oct 17, 2008 1:14 am

Yeah, that's it. If you could borrow one to see if this is your problem that is your best bet. A good passive DI can cost $$$.

Posted: Sun Oct 19, 2008 1:58 am

Thanks Geckomusic Very Happy

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