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Weak electric guitar signal (from electric banjo)

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Weak electric guitar signal (from electric banjo)

Postby ChuckkH » Thu May 14, 2020 10:58 am

This is a solid-body electric banjo, a Gold Tone EBT. It has a single coil pickup by the neck and a humbucker under the banjo head, not exactly at the bridge, more like a middle pickup.
I get some AC hum, for which I plan to open it up and apply shielding soon.
Regardless, the signal that does come out has always been relatively weak. It didn't used to be a problem onstage, with a moderate-sized amp, because we just cranked it up. Now, though, I'm trying to record it at home, and if I turn up the gain enough, the background noise gets too loud.

I bought a Behringer UMC22, since they advertise a wondrous preamp for the inputs, thinking it would raise the signal enough. It doesn't. I can raise it, but the UMC22 gets audible and visible static just by raising the gain past 70%, even with nothing plugged in.
I contacted Behringer support, and they recommended a DI box?!?! He says the preamp is meant for mics, not instruments. But what I read about DI boxes is that they take already-strong instrument signals and balance them for mic inputs. It seems no matter what I try, I was supposed to try something else! I have thought of crafting my own preamp from some NE5534 chips I have lying around. I don't have so much cash to throw just for the electric, as I mostly play acoustic. I'm also able to filter out the noise passably in software. I looked into buying new pickups; I could possibly afford a kit for a rail pickup, but that's without the wire. I'd prefer to be able to just use the sound it already makes (the electric is not my main axe).

But how is this supposed to work? I have pickups, a guitar jack, a guitar cable, and a signal that isn't quite strong enough. The Behringer I bought adds noise if I raise the gain (they also censored my review, predictably). How can I amplify it cleanly before going into the audio interface? I don't need it for shows right now. I just want to get the signal in the computer to be able to sculpt it. I don't trust what Behringer tells me to buy, after they advertised what they had to sell as a holy grail.

Thank you!
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Re: Weak electric guitar signal (from electric banjo)

Postby Wonks » Thu May 14, 2020 2:18 pm

Without having it in front of me, it's hard to say why the EMT output is so low. Both pickups are in fact humbucking, the single coil is in fact a stacked coil (according to the website specs), so should be pretty silent and hum free, as should be the humbucker.

A normal reason for low output is that the pickups are too far away from the strings. the humbucker is under the drum head, so you can't do much about that, but the Tele-style neck pickup can be raised up if there's room to do so. Press the strings down at the last fret and get it to about 2mm away from the strings. If the pickup won't raise that high, then it will need some more foam under the pickup to push it up further.

If you feel like taking the head off, you could see how high that humbucker is from teh strings. You may be able to raise it a bit, but you don't want it to foul teh head when it vibrates.

I don't know what strings you have fitted, but you need a nickel plated steel string for the wound string to work properly with the magnetic pickups, not phosphor bronze. the thicker the strings, the more output you will get. The banjo came factory supplied with 11s, so if you've changed down to 9s, then you will have less output a s a result

The "Inst 2" jack input on the UMC22 is designed to work with electric guitar level signals, so should be perfectly fine with the output from the banjo. You shouldn't need a DI box unless there is something else seriously wrong with the guitar electrics.

Can you borrow an electric guitar from someone and try that in the "Inst 2" jack? If you then get a strong signal, you know the UMC22 is fine and the problem is elsewhere.

Otherwise, have you tried a different lead? Sometimes there can be a fault with the lead that can cause a significant drop in signal level. You are using a TS to TS jack lead (mono) rather than a TRS to TRS (stereo) one? if not, get a TS to TS lead to get your volume back.

Unless there is a problem with the Behringer unit (it seems to be working), it's more likely there may be a wiring issue within the banjo or the lead.
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Re: Weak electric guitar signal (from electric banjo)

Postby shufflebeat » Thu May 14, 2020 9:18 pm

It's hard to tell if the pickup under the head has separate poles for each string. If not then it might be designed to work with a metal shim attached to the head like the Fishman mag pickup. If this is the case then check to see if the shim (if it exists) hasn't become detached or if the pickup has moved in relation to it.

This is all a bit vague but I'm looking at other models from the same manufacturer and making some semi-informed assumptions.
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Re: Weak electric guitar signal (from electric banjo)

Postby Wonks » Thu May 14, 2020 9:36 pm

But it's got two pickups, so even if one isn't great, then the other should be a lot louder, which I'm sure the OP would have mentioned.

I feel it's far more likely to be a dodgy or missing/broken solder connection, or a duff guitar lead. Pickups that are too low will give a weaker signal, but not that weak. It should be really easy to diagnose if only I had it in front of me.
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Re: Weak electric guitar signal (from electric banjo)

Postby Sam Spoons » Thu May 14, 2020 10:08 pm

shufflebeat wrote:It's hard to tell if the pickup under the head has separate poles for each string. If not then it might be designed to work with a metal shim attached to the head like the Fishman mag pickup. If this is the case then check to see if the shim (if it exists) hasn't become detached or if the pickup has moved in relation to it.

This is all a bit vague but I'm looking at other models from the same manufacturer and making some semi-informed assumptions.

I'd say that is almost certainly the case with the under head pickup, my mate has one on his Gibson 5 string banjo.
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Re: Weak electric guitar signal (from electric banjo)

Postby shufflebeat » Thu May 14, 2020 11:54 pm

Wonks wrote:But it's got two pickups, so even if one isn't great, then the other should be a lot louder, which I'm sure the OP would have mentioned.

Fair point, the steady hum seems to be beyond what we might expect from even the hummiest of hummers as well.

We're all still shooting in the dark a bit, and from distance.

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Re: Weak electric guitar signal (from electric banjo)

Postby ef37a » Fri May 15, 2020 6:42 am

The hum could be electro-magnetic or electro-static, usually a bit of both but if mainly the former, shielding won't help. Does the hum level change as you move the banjo about and can you find a 'null' position? If so you are picking up the magnetic field of a transformer or similar.

Incorporating a 5534 pre amp could be a good move. Go for about 12dB of gain and you can use a bias resistor of 470k which is high enough for the pickups (pups straight into op amp then low Z volume control or leave it out) The output offset will not be zero but only a few tens of mV and no bother. A top line FET amp would give slightly better noise performance but at a cost and you already have the NEs!

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