Tech: Behringer DI20 Hiss problem

Subject: Tech: Behringer DI20 Hiss problem
From: John J
Date: 22 Feb 13 - 07:49 AM

Hi folks,
A local folk band (Nelson-Peach) are using Behringer Ultra-DI20 D.I. boxes...but they generate a lot of hiss, using either internal battery or phantom power.

I've delved inside and discovered that the active devices are TL064 quad op-amps, unfortunately they're surface mount so replacement is going to be difficult, but not impossible, with the gear I've got. I wonder if replacing them with TL074 or TL084 might improve matters.

Does anyone have any experience of these DI boxes? A search on t'interweb shows that they're know for hissing so it looks like a design problem.

Ta,

John

Subject: RE: Tech: Behringer DI20 Hiss problem
From: Bonzo3legs
Date: 22 Feb 13 - 08:40 AM

I'm not sure that changing a TLO64 for a TLO74 would significantly reduce hiss. This unit has been designed for balanced inputs and ouputs, so if for instance an unbalanced mic is used it might be the culprit. I don't have the circuit diagram for this unit and without that it's difficult to advise.

Subject: RE: Tech: Behringer DI20 Hiss problem
From: Bonzo3legs
Date: 22 Feb 13 - 08:51 AM

D120 reviews

Scroll down in this link, the reviews speak volumes!

Subject: RE: Tech: Behringer DI20 Hiss problem
From: John J
Date: 22 Feb 13 - 09:07 AM

Thanks for your input.

According to the socket markings, Ch1 input is either balanced or unbalanced - it's a 1/4" stereo jack socket. I imagine the connections will be 1: screen 2 & 3: balanced input.

I guess that plugging an unbalanced signal in via a mono jack plug in will just ground one side of the balanced input. A bit crude but I suppose it works!

Any thoughts?

JJ

Subject: RE: Tech: Behringer DI20 Hiss problem
From: John J
Date: 22 Feb 13 - 09:10 AM

Ooh, just read those reviews....nasty!

JJ

Subject: RE: Tech: Behringer DI20 Hiss problem
From: GUEST,Graham Bradshaw
Date: 22 Feb 13 - 10:04 AM

I have a few of these, but we avoid using them unless there is no alternative. They are very hissy if the gain is turned up on the mixing desk. If they are fed with a strong signal, and you don't need much gain on the desk, they are acceptable. And the stereo feature can be quite useful.
I also have some of the bigger single ones - DI100 I think. These seem to be fine and have very little hiss, although they will clip and distort if you overload them.
We now use mostly the LA Audio ones - excellent, very clean, and less prone to clip. Also use some BSS, but very expensive.
Interestingly, there are the odd occasions when the Behringers seem to work better! Horses for courses I suppose.
Other cheaper ones that are worth checking out are the Studiospares ones - similar to the DI100 Behringer. Same sort of price but seem better made. Most now made in China these days.

Subject: RE: Tech: Behringer DI20 Hiss problem
From: Bonzo3legs
Date: 22 Feb 13 - 11:36 AM

I wonder if they would be any less hissy using a dual 15 volt power supply. Still can't find a circuit diagram (schematic for USAians).

Subject: RE: Tech: Behringer DI20 Hiss problem
From: John J
Date: 23 Feb 13 - 05:00 AM

It may help although I'd be surprised if it made much difference.

With it being S.M. fiddling with stuff like that will need the eyes of a 16 year old and the fingers of a gynaecologist - I'm neither!

It just seems to be a poor design using el-cheapo bits. Perhaps changing the op-amps to some quieter (like a quad NE5534 - if such a thing exists)would help. It seems that the noise is less noticeable if they're driven with a higher signal level - the noise will still be there but won't be as noticeable. Perhaps more gain is needed earlier on so as to over-ride the inherent noise.

I reckon Nelson-Peach are just going to have to spend a bit more money on better kit.

I'm still open to suggestions though!

JJ

Subject: RE: Tech: Behringer DI20 Hiss problem
From: GUEST,Musket sans cookie
Date: 23 Feb 13 - 05:30 AM

Op Amps certainly vary in quality. I was dismayed to see a 555 Op Amp (circa 1975?) soldered into a quality (not cheap) piece of kit recently.

When I was a volunteer on hospital radio many moons ago, we found balanced line for mics started introducing hiss that certainly wasn't there before. (We had raided the piggy bank and bought some AKG mice) but a single power supply, with mid point earthing on the transformer (built it ourselves to save money) not only got rid of an earth hum but also seemed to eliminate the hiss. Still not sure how that worked..

Subject: RE: Tech: Behringer DI20 Hiss problem
From: JohnInKansas
Date: 23 Feb 13 - 05:33 AM

Still can't find a circuit diagram (schematic for USAians).

In the US, much common usage calls the drawing that shows the components and how they're connected a circuit diagram. The term "schematic" is more often used to show the "logical diagram" that indicates only the functions of the parts but not necessarily what parts are used. The terms are used casually with interchangeable meanings, but few here (in the US) will have any difficulty knowing what you mean.

The substitution of components suggested could be a Kludge (the way it's done in the UK) or a Kluge (like we do it in the US), which are distinctly different terms with separate and specific meanings, so there is still some separation between our two vaguely similar languages.

John

Subject: RE: Tech: Behringer DI20 Hiss problem
From: John J
Date: 23 Feb 13 - 08:45 AM

Ah yes, two nations separated by a common(ish!) language!

I think you'll find the 555 isn't an op-amp but a timer IC - mind you, it's so damned versatile that I'll bet SOMEONE out there has made it work as an op-amp!

JJ

Subject: RE: Tech: Behringer DI20 Hiss problem
From: Bonzo3legs
Date: 23 Feb 13 - 09:55 AM

I constantly mourn the discontinuance of the CA3094 transconductance op amp, used in many old Electro Harmonix effects pedals.....and the wonderful SAD 1024 bucket brigate IC.

Back on topic, I believe that the TLO64 has a fairly low current draw which makes it ideal for battery power, but I've never experienced them as being particularly noisy. Try bypassing the battery supply with a decent 0.1uf capacitor, that may decrease some noise.

Subject: RE: Tech: Behringer DI20 Hiss problem
From: bruceCMR
Date: 23 Feb 13 - 10:06 AM

The DI20 has a reputation for being noisy. Interestingly, it apparently doesn't affect all of them - I know of some pro engineers who have been using them successfully without problems. Perhaps it's a batch thing? But at less than 20 quid per unit, it's hardly worth modifying...

At a budget level, the other behringer DIs are fine - the DI100 etc. The Studiospares own brand one is pretty good - and the own brand one from Thomann looks like it's the same unit, but a little cheaper.

Or check out the DIs from Orchid Electronics. A little more expensive, but great products from a UK company that makes great kit and understands our needs. http://www.orchid-electronics.co.uk (I have no connection with them other than as a satisfied customer)

Subject: RE: Tech: Behringer DI20 Hiss problem
From: GUEST,leeneia
Date: 23 Feb 13 - 01:58 PM

I'm just a girl, so what I would do is:

1. Read the manual, which can be found online.
2. Ask Behringer customer service, if they are still in business.
3. Ask my husband, who said,

   a. "Tell him to turn it down."
   b. Don't let wires cross over one another.
   c. Don't pile wires in coils.

For example, the manual says that you have to connect the gazeedus before you connect the upshot, or you may damage the thing. Somebody may have done that in the past, in which case your efforts are probably in vain.

Sounds systems are sure lingo-ridden, aren't they?

Subject: RE: Tech: Behringer DI20 Hiss problem
From: John J
Date: 23 Feb 13 - 05:14 PM

Thanks Leeneia - that made me laugh!

I've done all that - apart from contacting Behringer.

You're dead right about it all being lingo-ridden!

I now have A Plan. The noise level is constant and only a problem on very low-level inputs. I reckon if I increase the input level it should improve the signal-to-noise ratio. I'll build a simple single transistor pre-amp. If The Plan works, the hiss will still be there but at such a low level it won't be a problem.

But you know what they say about plans. We'll see - I'll report back!

JJ

Subject: RE: Tech: Behringer DI20 Hiss problem
From: Chris Partington
Date: 23 Feb 13 - 05:20 PM

Well. I bought one of those hissy D120 things too, thinking how bad could it be? I didn't lose too much when I Ebayed it shortly afterwards, so the lesson wasn't too expensive..

Subject: RE: Tech: Behringer DI20 Hiss problem
From: s&r
Date: 23 Feb 13 - 08:31 PM

Haven't used these, but Behringer are quite specific about the input being via an unbalanced TRS cable.

Stu

Subject: RE: Tech: Behringer DI20 Hiss problem
From: John J
Date: 24 Feb 13 - 07:47 AM

These DI boxes hiss just the same with nothing plugged in. I'd considered knocking up a low-pass filter to connect to the output but I fear it would bugger up the overall frequency response too much.

JJ

Subject: RE: Tech: Behringer DI20 Hiss problem
From: Boston Bass
Date: 24 Feb 13 - 10:21 AM

Have to say I've had one in my gig bag for many years. Used only occasionally when the house PA ran short of boxes, but with no problems.
BB

Subject: RE: Tech: Behringer DI20 Hiss problem
From: GUEST,Joe Sockit
Date: 09 May 13 - 07:49 AM

Add my voice to the many, fierce hiss makes it unusable. I bought it for using on the 2 channels of a powered board that didn't have pads on them. I thought if you were padding down a guitar that would give you less noise not more. But the more pad you use on the box, the louder the hiss. Damn, you'd think Behringer could at least make a direct box!. Those $7 XLR to 1/4 inline transformers work fine. Remember if it says "Professional" on the box...It's not.

Subject: RE: Tech: Behringer DI20 Hiss problem
From: treewind
Date: 09 May 13 - 09:57 AM

I've designed TL074s into various bits of home made kit many years ago, and despite being sold as low noise devices (and they are supposed to be a lower noise version of the TL064) I found then noisy.

This has nothing to do with balanced vs unbalanced. Changing the supply voltage and decoupling are unlikely to have any effect.

Adding a preamp before the box will help, but getting a better DI box in the first place would be a lot less messy and maybe cheaper in the long run.

The NE5534 is a great low-noise op-amp (and has been for nearly 40 years), but will take more current, and it won't be a drop-in replacement as it takes a lot of input bias current, while the TL064/74 family are FET input taking almost no bias current at all.

Would a passive DI do the trick? If their mixer has good low-noise inputs and they don't have instruments with high impedance outputs (e.g. some electric guitars/basses) they might be good enough.

Subject: RE: Tech: Behringer DI20 Hiss problem
From: Bonzo3legs
Date: 09 May 13 - 02:09 PM

Ah Treewind, I'm looking for the schematic for the MXR 126 Flanger/ Doubler. Unfortunately all known copies to be found on the internet are very difficult to read.

Subject: RE: Tech: Behringer DI20 Hiss problem
From: John J
Date: 09 May 13 - 07:10 PM

I've come up with a frig: the noise is fairly constant....so I thunk to meself, if I increase the input signal level it *should* improve the S/N level. A dead simple single transistor pre-amp proved this to be the case, gawd bless the BC337!

It's not a particularly elegant fix, but it works. Whilst I was messing about on the bench, Rick (who's DI box it is) went out and bought a couple of decent DI boxes that have sorted the problem rather more elegantly than my botch.....but I like rolling my sleeves up!

Treewind: I considered using NE5534 and tweaking the bias, but they're surmo and I'm not brave enough - many thanks for your input though!

Cheers,

JJ