Hum on LR Baggs Radius pickup

[Morgan76]

I recently got an LR Baggs Radius pickup and I'm having some issues with electronic hum when I try and wire it up.

The setup I'm using is:

Radius > 1/4" Jack > LR Baggs Para DI preamp > XLR > Behringer X1204USB mixer

The only way I'm able to get a useable signal is to have the volume up full, and the gain turned up fairly high on the Para DI. When I do that though I get quite a bit of electronic hum coming through.

I started off with a store-bought model. When I reported the issue to LR Baggs customer service they were very helpful and have sent out a Warranty replacement - but it seems to have a similar issue (though not quite as bad). I've attached an mp3 (with a few bars of music), which is about as good a sound as I'm able to get:

LR Baggs Radius Number 2.mp3

Am I just being dense here? Is there something I'm doing wrong, or is this just meant to be normal? Fiddling around with the EQ settings just seems to change the tone / frequency of the hum, but doesn't eliminate it.

Any advice much appreciated.


Kind Regards

Dave M

[Dave Martin]

This is not my experience with this pickup and DI. If you take the DI out of the loop, is the signal clean (but weaker)?

[Morgan76]

Hi there

No - I've tried plugging them direct into the mixer, but once the gain's turned up on that you can still hear the same thing.

When I worked through it with the guy from tech. support he was saying that it sounded like a problem with the internal grounding in the pickup. Seems odd to have would up with 2 units that have a similar problem though.

[Billy Packard]

I've used the same setup with no such issues at all. I have stopped using the Para DI because the preamps in my Acoustic Image Corous ll are very good and don't require anything else. Could your mixer be the problem? Poor grounding does sound suspicious.

Billy

billypackardmandolin.com

[pops1]

When I worked through it with the guy from tech. support he was saying that it sounded like a problem with the internal grounding in the pickup. Seems odd to have would up with 2 units that have a similar problem though.

Could be a bunch went thru with a new worker and they were grounded wrong. I have gotten car parts that several in a row were bad.

[Morgan76]

I was wondering about that, but I've tried running other sources through the mixer without the same problems.

It feels like it's maybe something related to a ground-loop issue, but I can't figure out why that would be if everything's running off the same power supply. The frustrating bit is that the Para DI doesn't have it's own ground-loop cut off switch, so I can't try that (without shelling out more money on kit).


Dave

[Mandoplumb]

Sounds likeba ground loop to me too but you are not plugged into two different circuit are you. I would try different cables if you haven't already then I would try.a three prong to two prong adapter carefully taking the ground out of the circuit. Lay the instrument down turn up volume then don't touch any part of the circuit, if buzz is gone you have some type of ground problem.

[Tom Wright]

From you recording I'm not sure there's a problem---tone is fine and I have to strain to hear the hum (very quiet to me). Forgive me for asking but have you used both the volume and gain adjust on the Para DI to get the signal at an appropriate level for the Behringer? The contact pickup will not have a whopping big signal and may need all the boost the Para DI has. Also, what is the result if you use the 1/4" output of the preamp instead of XLR?

[Beanzy]

i’ve not used one but just had a look at the spec for the BEHRINGER XENYX 1204USB
If you’re using the XLR to connect to the Berhinger that’s a mic input, the line input is on a jack.
You should get an XLR-F to balanced Jack lead to go from the DI to that input.

[pops1]

I have used the mic input and phantom power to use the Para, I think it is designed to go into a mic input if you use the XLR. If it is too hot use the 1/4", but the OP is saying it has to be turned way up so it is not too hot. Are you using phantom, and is your battery in good shape. The telltale sign of a low battery is noise.

[Beanzy]

Apart from the difference in impedednce the Berhinger has a mic preamp on that XLR.
Putting two preamps in line would be noisy.

[pops1]

The preamp in the Berhinger is the channel preamp and it has an input impedance of 2.6k. The para should match that quite well. While all impedance matching devices are called preamps, they really aren't. They are more of a buffer to the signal and match the one million ohms of the transducer to the input of the PA. a preamp is really an incorrect term and it should work into the Berhinger. All my preamps go into the PA using an XLR and all the XLR channels have a preamp. I have had no problem. I believe the pickup is flawed as there should be more gain, OP said the gain and the volume have to be up high. On any I have used I needed very little volume or gain to have plenty of volume thru the PA.

[Tom Wright]

The gain question is why I asked of the OP had also checked his gain + volume settings on the Para DI. My copy has the main volume but also the gain adjust on the connector panel. It has a very wide gain range with two options. I also had no trouble using the XLR out, and taking the phantom power when available. As pops said, check the battery, and I suggest confirming the gain adjust.

[Folkmusician.com]

This stuff is never simple.

Gain (small knob by the input jack):

Setting the gain: For optimum performance it is important to set the gain correctly to accommodate the output of your pickup, mic or other device.

Gain is not volume. Gain is the amount of amplification that is applied to an input signal to boost it to a useful level. To accommodate a wide range of pickups, active devices and such, the Para D.I. has adjustable gain. For instance, if you are using a low-output passive pickup such as the Ribbon Transducer, and you fail to turn the gain all the way up, you will need to turn the PA up so loud to hear the pickup that there will be a significant amount of hiss.

Conversely, if you plug a high-output active pickup into the Para D.I. and do not turn down the gain, you will hear a great deal of distortion.

The key is to adjust the gain to find a window between hiss and distortion. The Para D.I. is so quiet that this window is pretty wide, but there is a smaller "sweet spot" within that window.

IMPORTANT PART:

With your pickup or mic plugged into the Para D.I., and with the Para D.I. plugged into your PA or amp, play your instrument very hard. Turn the gain trim up (clockwise) slowly while playing until you begin to hear some distortion, then back the gain off (counter-clockwise) until the distortion just disappears. This setting will provide both the richest and cleanest sound. Once you have determined your preferred setting, we recommend that you leave the gain control alone.

In other words, set the gain on the preamp as hot as you can go without it distorting, then adjust volume with the volume knob.

Do not use the gain control as a volume control. Using it in this manner will vary the character of your sound as you adjust it up and down.
=======================


This would be the first thing to set and rule out. It may not be the cause of your noise, but it if the gain is too low, it could be.



* A standard guitar cable will attenuate our passive pickups by approximately 1dB per foot.

An extremely long, too small of gauge, or otherwise poor quality cable would lend to this. Plus if it is not shielded well, who knows what it is picking up. That would be the next thing to check off the list.

[Morgan76]

Thanks for the responses everyone. I'll try having a bit of an experiment when I get some time over the next couple of nights, and I'll report back on the results.


Dave M

[MontanaMatt]

If your pickup is kaput, Baggs will replace it for a nominal fee. Contact them to get the return authorization.
I bought one through the classifieds that arrived and promptly died in my arms...I thought I was stuck holding the bag, but Baggs set me up with a new one, even though I wasn't the original owner.
Happy pickin

[gspiess]

Given the description, first thing I would do is take your gear and try it in another board to see if the problem repeats itself. If it does, then you can assume you've isolated it to either the DI or the pickup. So the next step would be to try a different pre-amp/DI with the same intent - isolate the problem. Repeat until satisfied you've found the culprit.

[Morgan76]

Hi everyone - managed to get time to test some things and work up an update.

Since the weekend I've managed to get hold of a Condenser Microphone and also a 1/4" jack to USB cable.

The microphone works well on every channel on the mixer, with minimal background noise, so I can rule out the mixer as the source of the problem.

I've continued testing the setup of the pickup and DI box with a variety of different cabling options, as well as with & without Phantom power - which doesn't seem to make a great deal of difference.

Finally I've also run the pickup straight into my laptop using the 1/4" to USB cable. This gives the best volume level I've had so far, but still continues to include a degree of hum. I've tested both the pickups with it and they make the exact same tone:

PIckup standard signal.mp3

That would suggest to me that the problem is right at the source. The only question I'm left pondering is whether this is "normal", and I'm just being too fussy.


Kind Regards

Dave

[gspiess]

Dave, A microphone is a completely different animal than a pickup, and does not represent what I'd consider a valid A/B test. My concern is that there may be a "headroom" incompatibility issue between your stage gear and the sound board's channel pre-amps. The best way to test that is to begin isolating various components to see if the hum disappears; and my first step would be to test your mandolin and stage gear through another sound system. The solution may simply be adjusting the gain at some point in the signal chain to decrease the source of the hum so it is not subsequently amplified further down the line.

[pops1]

Is there somewhere where you can go that sells these or could plug it into other equipment just to finalize that it is indeed the pickup.

No it's not normal, call and return the pickup. they must have had a batch that were bad. If that is the case others may have called and they would be aware of the problem. Just tell them all you have tried and return it again.

[Folkmusician.com]

Agree, not normal, unless there is something else that is the cause. Hum is usually being picked up from something nearby, in the signal chain or the power. There is a very good chance that the pickup is simply acting like an antenna, but isn't the actual source. Anything electronic could be the cause of the hum. Lights can cause it... Something in another room on the same power circuit. etc..

This is where the A/B testing comes in. And that needs to include a different location and power source. If it really is the pickup, then it needs to be replaced. I have installed hundreds of the LR Baggs Radius on mandolins and never heard any hum. Not saying it isn't the problem in your case though.

[almeriastrings]

The microphone works well on every channel on the mixer, with minimal background noise, so I can rule out the mixer as the source of the problem.

No, you can't.

a) Your mics will be balanced - the transducer is unbalanced.
b) Mics = 600 ohms vs. transducer 1M+ so massive impedance differences.

Also (if I recall correctly) this mixer utilizes a 'floating' ground vs. true ground and these are notorious where induced hum is concerned.

You really need to check this out systematically. Get someone who is well versed in audio electronics to help.

There could be several things going on here.... please do not send phantom power to the transducer, either. You will fry it...

[Tom Wright]

a) Your mics will be balanced - the transducer is unbalanced.
b) Mics = 600 ohms vs. transducer 1M+ so massive impedance differences.

The Para DI XLR output is low-impedance balanced, and accepts phantom power, so going into mixer mic input should be fine (always has been for me).

OP says he tried 1/4" into his laptop via USB, but doesn't say if the 1/4" is from the pickup direct or from the Para DI. I still suspect improper gain structure in the DI, but haven't heard if this was tested.

[pops1]

If you plug your pickup straight into the PA, nothing inbetween, is there still hum. If there is and you are using a cord that you have plugged something else into the PA with no hum then it has to be the pickup.

[almeriastrings]

The Para DI XLR output is low-impedance balanced, and accepts phantom power, so going into mixer mic input should be fine (always has been for me).

OP says he tried 1/4" into his laptop via USB, but doesn't say if the 1/4" is from the pickup direct or from the Para DI. I still suspect improper gain structure in the DI, but haven't heard if this was tested.

That is with the Para DI in line - it was not clear that this comparison test was conducted like that.

With correct grounding, you can really crank the gain on Para DI's. Should certainly not be any audible hum present, though residual noise (hiss) will rise a fair bit.

The 'virtual' ground (floating ground) can still be an issue on some low cost mixing gear even if an active DI/pre is used.