Piezo pickups and hum

[TOCS]

I really want to understand this a little bit better, so I decided to make this thread.

So, lately I've been toying around a lot with piezo pickups from USTs to SBTs. One of my guitars has the eSonic2 preamp system installed which comes with a dual-source pickup configuration consisting of a UST and a magnetic pickup. The magnetic pickup sounds fine with absolutely no noise to be heard even with the gain cranked to max on my audio interface (which is a Behringer U-PHORIA UMC404HD). However, that most certainly is not the case with the UST. It hums, not a lot, but it does hum -- it's not completely silent like the magnetic pickup. Most of it goes away when I touch the endpin and even more when I touch the endpin and a metal object such as the strings on the guitar.

Now, a month ago or so I purchased one of those cheap piezo SBT pickups from eBay for like $2 just to see what an SBT sounds like compared to other types of pickups. And it suffers from the same problem. I figured it might be because it wasn't shielded properly since it was basically just a piezo disc with no insulation going to a female end with no apparent shielding of the wire.

Yesterday, I received a pair of JJB transducers. I basically ordered the transducers without any endpin so I could solder it myself. I soldered it together with my Sunrise magnetic pickup to a shielded stereo Switchcraft endpin. And yet again, the result is pretty much the same. Hum. No problems with the Sunrise.

I keep reading everywhere that you have to "ground it properly" and I'm getting pretty confused as to how this is done. How can I possibly ground the signal even more without actually modifying the wire or transducer itself? Do piezo pickups just have a really high noise floor or something? Can someone please school me on this? Because I find it odd that people praise this pickup technology so much when it seems pretty much impossible to make silent.

[simondylan]

How are you shielding the connection? If you solder the ground but don't shield the hot it will hum. If you wrap the connection with shielding tape but don't solder the shield to the ground the tape will act as an antenna and cause even more hum! If you have a jack that has a metal barrel cover it should shield adequately as long as you did all your soldering correctly.
Are you running the signal through a preamp?
It could be that you're trying to get a low output, high impedance passive pickup up to a usable volume level. If that is the case a good preamp with the appropriate level of gain at the input will likely take care of it.

[TOCS]

Originally Posted by simondylan

How are you shielding the connection? If you solder the ground but don't shield the hot it will hum. If you wrap the connection with shielding tape but don't solder the shield to the ground the tape will act as an antenna and cause even more hum! If you have a jack that has a metal barrel cover it should shield adequately as long as you did all your soldering correctly.
Are you running the signal through a preamp?
It could be that you're trying to get a low output, high impedance passive pickup up to a usable volume level. If that is the case a good preamp with the appropriate level of gain at the input will likely take care of it.

The transducer comes shielded. It has a hot red conductor that is shielded. The shielding is then used as ground. It's also shielded with a metal barrel like you said.

I don't know what the impedance level of the JJB transducers are, but I am trying to obtain a respectable level of volume without too much hum, which I find impossible. I run the configuration straight to either a cheap electric guitar amp or my Behringer U-PHORIA UMC404HD audio interface with the same results.

JJB recommends that their transducers are interfaced with a 1Mohm preamp. According to the specs of my Behringer audio interface, it has exactly 1Mohm input impedance.

What may be the difference of running it to my Behringer or a good piezo preamp?

[simondylan]

Yeah I was only referring to the connection at the jack for shielding.
I don't have hands on experience with the JJB pickups specifically so I can't say whether or not what you're experiencing is normal with those but I have worked with the K&K and almost every other model of pickup and most of them don't have this problem.
Now for the preamp, it should help some because it will boost the signal level of the pickup which should cause the hum to be much less noticeable. You'd won't have to turn up your volume as high to get a good usable signal.
As far as the recommendation of a 1 meg ohm input, don't worry so much about that. What that does essentially is tame your bass response like a high pass filter would do because this type of pickup, just like the K&K, has an abundance of bass! If you have access to another preamp that doesn't have the 1 meg ohm input you can just adjust the bass response with EQ.

[Kater]

I had that problem come and go , very often, was very frustrated.
The SBT I am using is the Trance Audio Acoustic Lens,
the first time I soldered that to my TRS endpin jack, with a Sunrise Magnetic, Sunrise to the tip, SBT to the R, share sleeve. When it goes in to the preamp stage, the Sunrise was doing good, the SBT was making a hum around 60hz.

When I touch the preamp box, the hum goes away.

I talked to Greg who created the SPS1 preamp then about this, he was very helpful and said it was about the shielding of the pickup, and possible something to do with my endpin soldering too. Turns out, he was darn right, I took everything out and resoldered every thing, god was I messy and ignorant when I soldered it last time. there was copper conductors going here and there, possibility creating bridges between signal and sleeve.

When I fixed these, it turns out to be whole lot better, still some hum going on with the same frequency, but , with normal gain staging, that's no longer a problem.

Also, I notice that on some power sources, this problem seems to be gone completely, I used to play at a university rehearsal room, everything equal, the hum is gone, I assume it has something to do with ground and power grid? not sure.

So, I guess it is always good to check the solder work first, use good quality shielded cable,or if the hum solely happen around 60hz, dial it out with notch filter or any parametric EQ using narrow bandwidth, other than that, I cannot figure out anything yet with my capability. hope my experience help.

[TOCS]

Originally Posted by Kater

I had that problem come and go , very often, was very frustrated.
The SBT I am using is the Trance Audio Acoustic Lens,
the first time I soldered that to my TRS endpin jack, with a Sunrise Magnetic, Sunrise to the tip, SBT to the R, share sleeve. When it goes in to the preamp stage, the Sunrise was doing good, the SBT was making a hum around 60hz.

When I touch the preamp box, the hum goes away.

I talked to Greg who created the SPS1 preamp then about this, he was very helpful and said it was about the shielding of the pickup, and possible something to do with my endpin soldering too. Turns out, he was darn right, I took everything out and resoldered every thing, god was I messy and ignorant when I soldered it last time. there was copper conductors going here and there, possibility creating bridges between signal and sleeve.

When I fixed these, it turns out to be whole lot better, still some hum going on with the same frequency, but , with normal gain staging, that's no longer a problem.

Also, I notice that on some power sources, this problem seems to be gone completely, I used to play at a university rehearsal room, everything equal, the hum is gone, I assume it has something to do with ground and power grid? not sure.

So, I guess it is always good to check the solder work first, use good quality shielded cable,or if the hum solely happen around 60hz, dial it out with notch filter or any parametric EQ using narrow bandwidth, other than that, I cannot figure out anything yet with my capability. hope my experience help.

I played on the big stage a few weeks ago and had no noise or hum at all. It ran through a nice PA with a Midas board and I had no issues at all. So, I had a chat with the sound guy about this since I then concluded it probably wasn't my soldering or the pickup. He said that piezos in general can be tough to battle with and that you need good ground to get rid of the hum. I later realised that neither my amp or audio interface I use on the computer is grounded in any way, so that's probably one of the biggest reasons for the hum.

Another thing is, when I played on that stage I would run my pickups to a DIY preamp/splitter box and then to some box that would convert the unbalanced signal to a balanced one which would then go to the board. I have a feeling this step might help reduce the hum as well.

I still would like someone to explain to me why magnetic pickups doesn't act the same way. The Sunrise I have in my guitar seemingly don't care if I plug in to an interface that isn't grounded. There's no audible hum at all. Not even at ridiculous gain levels.



On a side note: You gotta explain that setup of yours to me! I read on Trance Audio's website that their pickups just didn't work properly with manufacturers preamps. Did you just buy one Acoustic Lens instead of one of their entire pickup systems? Or did you ditch their preamp in favour of the SPS1?

I reckon Hedges did something similar with his FRAP pickup. He'd utilise it passively and then run it into a custom external preamp by Trance Audio. Not sure why he wouldn't just use the internal preamp bundled with their systems.

I've been looking at their stereo system for quite a while now, and it just seems great. I'd run a Sunrise + an Acoustic Lens through their internal preamp and then to some external EQ/preamp (I'm not sure if another gain stage is necessary).

[Kater]

Originally Posted by TOCS

I played on the big stage a few weeks ago and had no noise or hum at all. It ran through a nice PA with a Midas board and I had no issues at all. So, I had a chat with the sound guy about this since I then concluded it probably wasn't my soldering or the pickup. He said that piezos in general can be tough to battle with and that you need good ground to get rid of the hum. I later realised that neither my amp or audio interface I use on the computer is grounded in any way, so that's probably one of the biggest reasons for the hum.

Another thing is, when I played on that stage I would run my pickups to a DIY preamp/splitter box and then to some box that would convert the unbalanced signal to a balanced one which would then go to the board. I have a feeling this step might help reduce the hum as well.

I still would like someone to explain to me why magnetic pickups doesn't act the same way. The Sunrise I have in my guitar seemingly don't care if I plug in to an interface that isn't grounded. There's no audible hum at all. Not even at ridiculous gain levels.



On a side note: You gotta explain that setup of yours to me! I read on Trance Audio's website that their pickups just didn't work properly with manufacturers preamps. Did you just buy one Acoustic Lens instead of one of their entire pickup systems? Or did you ditch their preamp in favour of the SPS1?

I reckon Hedges did something similar with his FRAP pickup. He'd utilise it passively and then run it into a custom external preamp by Trance Audio. Not sure why he wouldn't just use the internal preamp bundled with their systems.

I've been looking at their stereo system for quite a while now, and it just seems great. I'd run a Sunrise + an Acoustic Lens through their internal preamp and then to some external EQ/preamp (I'm not sure if another gain stage is necessary).

Hi TOCS.
Thanks for sharing!

I agree with the Proper Ground theory you put, since I am experiencing different hum level from place to place.
I never used any DI between preamp and board before, I guess that is a must on stage, since normally you will be dealing with long cables on stage, to me , I record in my home studio most of the time, I try to avoid extra gain stage to keep my recording clean.
Trance page and its manual did state that ' the lens wont work well with other brand pres' , meh, I just love to test every thing out even when I was told no, the worst thing could happen is ' it feels not right', no harm trying right? And I guess people from Trance did not consider every possible signal chain possibility, generally, they want to discourage you from trying and error, sometime , on a consumer perspective, that is not a happy scenario.

I always keep one and only goal in mind when I choose the perfect companion for Sunrise, that is, no harshness, no Low Freq Boom, higher feed back threshold, some fine sonic texture to compliment the buttery Sunrise typical Mag sound. Turns out, the lens fits all specs I need.
I play a lot of Japanese fingerstyle songs,they tend to use lots of extended harmonics , which require a lot of detail on the high end,or, As i say' texture', at the same time, Sunrise add the flexibility on the texture of bass line, which vary from songs to songs.
Generally this set up requires good preamp to bring out the tonal complexity and potential of the two pickups. A good EQ is a plus, for stage gig, I always feel that full parametric EQ useful.
It is a shame that Greg don't make these great preamps any more, there is one Japanese boutique workshop called M-Factory seems to have something similar( tonally) , they use their own piezo head which only comes with their system and they sound really amazing, they have test video on Youtube.
Just a side note, by saying ' great', I mean 'flexibility', since i always take SPS1 as the point where I stop my exploring on preamp. it is a swiss army knife to my rack, but I've heard dtar, kk, and other preamp, they all sound great but some how lack the flexibility I need. I know I am way off topic right now, I just cant stop saying good things about them !

Reason why Michael shift to a trance preamp is pretty simple, IMO, the preamp ship with FRAP shapes like a small stomp box, too heavy, too dangerous to be mounted inside,there might be other internal versions, yet I saw none during my search, Correct me if any one know if there was any. Simply put, there is no other good option to put the critical 1st stage amp inside the guitar, I read some posts about his stage equipment. some said he did have pendulum preamp, it is just unknown to me why he did not base his signal chain on SPS1. (come to think of it, he might like the flexibility of wireless system, he did jump and move, a lot!)

I now have two version of FRAP preamp( both old red version and later silver version with 'IT' Printed on, and one FRAP PU head. I dont know how many revision FRAP engineer did back then, the version seems to be very confusing.

Any way, I am going to take the Lens down and put the old FRAP in, I am planing to throw an AB testing to both and we will see who win the battle of generations. LOL

Again, I want to mention once more the great talk with Greg from Pendulum, as I remember he did said something about the build of Sunrise, it is constructed with shielding in mind, maybe in the body, i did saw some aluminium or copper foil sticking out, assuming that it is shielded with care. as to the piezo, not that lucky, most of them are just 'naked'.

[TOCS]

Originally Posted by Kater

Hi TOCS.
Thanks for sharing!

I agree with the Proper Ground theory you put, since I am experiencing different hum level from place to place.
I never used any DI between preamp and board before, I guess that is a must on stage, since normally you will be dealing with long cables on stage, to me , I record in my home studio most of the time, I try to avoid extra gain stage to keep my recording clean.
Trance page and its manual did state that ' the lens wont work well with other brand pres' , meh, I just love to test every thing out even when I was told no, the worst thing could happen is ' it feels not right', no harm trying right? And I guess people from Trance did not consider every possible signal chain possibility, generally, they want to discourage you from trying and error, sometime , on a consumer perspective, that is not a happy scenario.

I always keep one and only goal in mind when I choose the perfect companion for Sunrise, that is, no harshness, no Low Freq Boom, higher feed back threshold, some fine sonic texture to compliment the buttery Sunrise typical Mag sound. Turns out, the lens fits all specs I need.
I play a lot of Japanese fingerstyle songs,they tend to use lots of extended harmonics , which require a lot of detail on the high end,or, As i say' texture', at the same time, Sunrise add the flexibility on the texture of bass line, which vary from songs to songs.
Generally this set up requires good preamp to bring out the tonal complexity and potential of the two pickups. A good EQ is a plus, for stage gig, I always feel that full parametric EQ useful.
It is a shame that Greg don't make these great preamps any more, there is one Japanese boutique workshop called M-Factory seems to have something similar( tonally) , they use their own piezo head which only comes with their system and they sound really amazing, they have test video on Youtube.
Just a side note, by saying ' great', I mean 'flexibility', since i always take SPS1 as the point where I stop my exploring on preamp. it is a swiss army knife to my rack, but I've heard dtar, kk, and other preamp, they all sound great but some how lack the flexibility I need. I know I am way off topic right now, I just cant stop saying good things about them !

Reason why Michael shift to a trance preamp is pretty simple, IMO, the preamp ship with FRAP shapes like a small stomp box, too heavy, too dangerous to be mounted inside,there might be other internal versions, yet I saw none during my search, Correct me if any one know if there was any. Simply put, there is no other good option to put the critical 1st stage amp inside the guitar, I read some posts about his stage equipment. some said he did have pendulum preamp, it is just unknown to me why he did not base his signal chain on SPS1. (come to think of it, he might like the flexibility of wireless system, he did jump and move, a lot!)

I now have two version of FRAP preamp( both old red version and later silver version with 'IT' Printed on, and one FRAP PU head. I dont know how many revision FRAP engineer did back then, the version seems to be very confusing.

Any way, I am going to take the Lens down and put the old FRAP in, I am planing to throw an AB testing to both and we will see who win the battle of generations. LOL

Again, I want to mention once more the great talk with Greg from Pendulum, as I remember he did said something about the build of Sunrise, it is constructed with shielding in mind, maybe in the body, i did saw some aluminium or copper foil sticking out, assuming that it is shielded with care. as to the piezo, not that lucky, most of them are just 'naked'.

That's great info!

Please, when you AB the FRAP and the Acoustic Lens let us know your results in a different thread.

[jseth]

I hate to be the one to pee in your punch bowl, but I have used UST pickups since they came out in the 70's... all different brands and types... and I have NEVER experienced even the slightest bit of hum with any of them... seriously NOT ONE!

Sounds like there is a fundamental aspect of the installation that you don't grasp, or are unaware of. I'm sure you aren't creating a problem on purpose, but every one of my UST pickups has been installed by a pro, by someone who is very good at doing what they do for their living... as I mentioned, not one issue with hum, not when a pickup was working correctly, anyway.

I think that, in this case, it IS the Indian and not the arrow...

[martingitdave]

Check the grounding.

Sent from my SM-G930V using Tapatalk

[TOCS]

Originally Posted by jseth

I hate to be the one to pee in your punch bowl, but I have used UST pickups since they came out in the 70's... all different brands and types... and I have NEVER experienced even the slightest bit of hum with any of them... seriously NOT ONE!

Sounds like there is a fundamental aspect of the installation that you don't grasp, or are unaware of. I'm sure you aren't creating a problem on purpose, but every one of my UST pickups has been installed by a pro, by someone who is very good at doing what they do for their living... as I mentioned, not one issue with hum, not when a pickup was working correctly, anyway.

I think that, in this case, it IS the Indian and not the arrow...

You should probably read the previous posts first.

Anyway, the JJB pickups I have are not USTs, but SBTs. I do, however, have a UST with matching preamp in my Epiphone which is factory installed and it shares the exact same problem thus eliminating any reason to think that it might be an installation issue.

Like I already posted earlier, I basically narrowed my problem down to a ground issue. None of my equipment is grounded and I have no DI box to help it either (but I'll probably get that in the future).

If you've never experienced this you must have been lucky to always have good ground. I don't know if this hum is very audible with speakers since I always use headphones when at home for recording and sound evaluation.

Originally Posted by martingitdave

Check the grounding.

Sent from my SM-G930V using Tapatalk

Yup, it was the problem.

[Mandobart]

I've used JJB pickups in over a dozen instruments from fiddles to upright bass and everything stringed in between. Never had a hum, but I always play through a house PA or my own acoustic amp which is grounded.

[martingitdave]

I should clarify that you should check the grounding of the whole signal chain from pickup install to amp. It seems you did so, and identified the culprit. Glad it wasn't the final pickup install.

Sent from my SM-G930V using Tapatalk

[Toptip]

Isn’t the real reason for the hum, that piezo pickups have extremely high impedance, so high in fact, they are like an open circuit? Sending a signal from that impedance, down any length of cable to an amp, must be like having an unconnected feed.

I do not know what the cure is except perhaps the shortest cable to the first device, preamp or pedal.

Alternatively there might be an immediate circuit past the piezo to exchange this impedance to something lower.

I wonder if resistor loading can also do the trick?

[TOCS]

Originally Posted by Toptip

Isn’t the real reason for the hum, that piezo pickups have extremely high impedance, so high in fact, they are like an open circuit? Sending a signal from that impedance, down any length of cable to an amp, must be like having an unconnected feed.

I do not know what the cure is except perhaps the shortest cable to the first device, preamp or pedal.

Alternatively there might be an immediate circuit past the piezo to exchange this impedance to something lower.

I wonder if resistor loading can also do the trick?

This was a few years ago. Still a newbie but I figured it comes down to having proper grounding, and staying away from interfering devices. Recording to battery powered devices is a quick route.