Do I Need a DI Box?

Inkyfingers

New member
I just bought a Boss RC 300 looper and when I plug it into my amp I get a bit of hum that I'd like to get rid of. Should I put a direct input box between the looper and the amp? I don't have any problem with my guitar causing humming when I plug it into the amp.

Thanks,
Ken
 
You're running the looper off a wallwart? Make sure that's plugged into the same power strip as the amplifier first. If that doesn't help, try a different wallwart. Always make sure that the pedal supply matches the voltage, but also the polarity that the pedal wants. Watch out for AC vs DC too. It needs to be able to source more current than the pedal says it wants.

It's very unlikely that a DI box will help this situation.
 
A noise gate between the two should fix it. If you're recording onto a Digital Audio Workstation, you can wipe the noise off afterwards.
 
If the RC 300 PSU is a 3 pin wall rat then you could have a hum loop, if it isn't you can't. Could just be that the total system gain has increased and thus more hum is being generated. Could be a faulty PSU. Could be a signal cable too close to the wall rat, the things are notorious for chucking out hum fields.

Soon as you can, post a clip, 10 secs or so of attached 320k MP3 of JUST the noise.

Dave.
 
- Reading one of your other threads you stated you had a Boss RC30. Did that have a hum also?
- Have you tried different output level settings on the RC300 and input gains on the amp? Or is the hum present at any level/gain setting of either the RC300 or the amp?
- What is the amp and does it have a 3 wire/prong plug on its power cord as well as any extension cord or outlet having the same?
 
The amp and the Looper are plug into the same outlet strip. When I used the RC 30 I didn't have any problem with humming. Guitar plugs into the looper wtih a trs and the looper plugs into the amp again with a trs. The amp is a Fishman Loudbox Artist. The only thing that change from when I had no humming is to swap the rc 300 for the rc30.

Hope this helps,
Thanks all,
Ken
 
Guitar plugs into the looper wtih a trs and the looper plugs into the amp again with a trs.

Hope this helps,
Thanks all,
Ken
By 'trs', do you mean TRS(tip-ring-sleeve) type cables? You should be using TS(tip-sleeve) type cables for connecting the guitar to the RC300 and then out to the amp. Regular instrument cables would be fine. Only the Mic XLR jack would be balanced and there is no mention of the 1/4" jacks being balanced that would accept a TRS plug. Not sure if it may be the reason for the hum, but an extra conductor in the cable that has no termination between devices possibly could pickup some unwanted hum or noise.
 
Most pedals won't even turn on with a TRS cable plug in the input. This one might be different, but you should be using TS cables all the way through.
 
By 'trs', do you mean TRS(tip-ring-sleeve) type cables? You should be using TS(tip-sleeve) type cables for connecting the guitar to the RC300 and then out to the amp. Regular instrument cables would be fine. Only the Mic XLR jack would be balanced and there is no mention of the 1/4" jacks being balanced that would accept a TRS plug. Not sure if it may be the reason for the hum, but an extra conductor in the cable that has no termination between devices possibly could pickup some unwanted hum or noise.

Oops, sorry, yes I use mono ts cables from my guitar to the looper and from the looper to the amp.

So let's go back to the original question. If I put a DI box between the looper and the amp first, will I hurt anything and second should it help with the humming issue?

Also, sorry for the newbie question, but what is a PSU?

Thanks again,
Ken
 
If the RC 300 PSU is a 3 pin wall rat then you could have a hum loop, if it isn't you can't. Could just be that the total system gain has increased and thus more hum is being generated. Could be a faulty PSU. Could be a signal cable too close to the wall rat, the things are notorious for chucking out hum fields.

Soon as you can, post a clip, 10 secs or so of attached 320k MP3 of JUST the noise.

Dave.

No the PSU is two pin.

Ken
 
Oops, sorry, yes I use mono ts cables from my guitar to the looper and from the looper to the amp.

So let's go back to the original question. If I put a DI box between the looper and the amp first, will I hurt anything and second should it help with the humming issue?

Also, sorry for the newbie question, but what is a PSU?

Thanks again,
Ken

'Power Supply Unit'. A DI box typically takes a guitar signal and delivers a balanced mic level signal and so inserts about a 20dB (by 10) loss they also isolate the incoming signal earth from the outgoing signal. They are not typically used between a guitar and an amplifier.

There are isolator boxes (that should NOT be called "DI boxes" IMO) that isolate the earth but are almost lossless, 1:1 transformers, but I am convinced your hum problem is either a gain issue or stray pickup or, as I mentioned, a faulty PSU.

Dave.
 
PSU is the box you plug into the AC outlet and it drops the 240/220/110 volts to, say, 6. You might know it as a transformer.

There will be no earth loop when using PSUs. Other than laptop ones, they are double insulated and therefore have no earth bond. The plug into the device is your clue. Two connections only means no earth. Being plastic and low voltage, the Boss doesn't need earthing. I know this from being registered to safety test mains appliances—PAT testing here in the UK. The noise is coming from inside your 300. Talk to the seller. It might be something all 300s do or you might have a faulty PSU. Don't use it until you've checked, as faulty mains appliances can be unsafe to use.
 
PSU is the box you plug into the AC outlet and it drops the 240/220/110 volts to, say, 6. You might know it as a transformer.

There will be no earth loop when using PSUs. Other than laptop ones, they are double insulated and therefore have no earth bond. The plug into the device is your clue. Two connections only means no earth. Being plastic and low voltage, the Boss doesn't need earthing. I know this from being registered to safety test mains appliances—PAT testing here in the UK. The noise is coming from inside your 300. Talk to the seller. It might be something all 300s do or you might have a faulty PSU. Don't use it until you've checked, as faulty mains appliances can be unsafe to use.

Actually the RC 300 is all metal as is the RC 30.
 
If you turn down the output level or the input gain of the RC300 leaving the gain setting of the Fishman amp the same, does the hum go away or reduced?
Unplug the instrument cord plug at the amp.
Any hum in headphones plugged into the RC300?
Is the anything else plugged into the RC300 besides an instrument or the output to the amp? (the PSU is a given)
 
Okay, all metal. I didn't know. There's still no need for earthing. Reading your OP again, I'm pretty sure the problem is circuit noise. Maybe the PSU is unregulated. Check with the maker, anyway. Is there a gain or level control?
 
The PSU is likely going to be a switched mode, regulated, non-transformer power supply. Most countries have banned transformer based PSU's.
This is the RC300..
 

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There's a PHONES jack in the back of that thing. Is the hum present there, as well, whether connected to the amp or not? Amp on or not? Etc...

Try changing to different cables - I assume this has been tried?
 
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