Thank you so much! With the schematics here I was able to rewire my SR500 to a passive after the preamp failed. Got a working bass again, and don't have to worry about the battery :)
The preamp is actually an input buffer and eq. The high impedance drops after buffering and the pickups reach the blend pot buffered. That's why it's just 25KOhms while the pickups are passive. The 25K blend is too low a value to directly connect your pickups to.
And that's why you lose so much treble with "Preamp Bypassed". Get a 250K or 500K MN taper blend, like, yesterday. Thank me later when you have all your treble back and no noise.
someone pointed that out when this came out, and yeah I swapped in 1M pots, it's at the top of the description. some of the "noise" that was removed was just treble, so it's hard to say if this really reduced the noise much in the end, but I still like having it passive.
@@NickLeonard you could shield the electronics cavity and also the pickup cavities (connecting them to the grounded electronics cavity). Shielding paint will do but copper foil is best.
When I had a newer SR505 I actually considered removing the preamp but I didn't want a passive bass, so I wound up blowing a ton of money on a Dingwall, simply because I still wanted an active bass that sounded better. Especially when recording I'm definitely not a fan of passive guitars, let alone basses, and thankfully my new 10-string guitar had Fishman Fluence Moderns, which, while I was hoping for something better, it at least had active pickups which still saved my recording sessions.
I'm late to the party but if I were to pursue a project like this and wanted maximum treble out of the pickups, I'd wire it Volume, Volume like a Jazz Bass without the Tone control. That eliminates the effects of the Blend pot. One of the key take-aways should be that if the bass has passive pickups and if either balance/blend or volume pots are in the 25K to 50K ohm range, they should to be replaced with values more traditionally suitable for passive pickups, aka 250Kohms and up.
Dude active pickups do not need a preamp its built into the pickup. Active basses with passive pickups have a preamp like you are talking about. And like your saying removing the preamp us fine.
I’ve got the SR500. I have the treble control permanently turned down to remove the brightness from the preamp. It’s not noisy luckily but going passive is definitely on the cards soon
Nice ! I did get a pair of Bartolini MK1 a while back, for just 15€ used :D I put them in my Ibanez EDB600 (which I got for under 50€) that had a dead bridge pickup and dead preamp. This was not the first pickup change I did in that one (used a dual blade Belcat guitar pickup at the neck position for a while), but in the end the Bartolini are much better than what originally came with that Bass. I seen plenty people complain about the preamp which usually comes with these Bartolini Mk1. One thing with these ; they have a pretty low output (and ohm reading) and I have to use a clean boost in the chain when I use this specific Bass. (as seen in my latest vid) I would suggest leaving any blend pot out and instead use a DPDT switch to have Series/Parallel option, which is really good with these 😁 The wiring in my EDB600 ended up kinda weird with a dual-tone pot with a switch between two capacitor values. But really it was an excuse to populate the empty holes left by the preamp 😅
Part of me would live to rip everything out my Ibanez and just have a volume knob and pickup selector switch BUT I do like the brightness. Its just a headache having EQ on the guitar and an EQ in my signal chain AND on the amp plus whatever pedals with their tone options. Too many variables. Concluding it might be better to leave the Ibanez alone and just buy a Squire P bass so have both options. Or of i can get another SR cheap pre-owned mod that one.
The brightness loss was really because the blend and volume pots are super low values for a preamp. Stick 1M or 500K parts in and you're fine. Of course, some of the "noise reduction" in this video was just treble being lost, so I don't know if this mod really reduces noise, but it's nice to have it passive anyways
That's an insane amount of detail in the info! I was just looking to replace a barrel jack in my 305M, but this is an interesting idea, have to look into what the stock pick ups are in mine 🤔 stellar work!
Hi there, very useful and informative video! I have an Ibanez BTB series bass and I have a constant noise that goes away when touching ANY METAL PARTS OF THE CIRCUIT, and that includes the Metal parts on the amp, the Multi-effect , bridge, strings , preamp knobs and etc... could this still be a grounding issue? I tested back of the cavity with a multi meter and some parts seemed to have "continuity" , whereas some of the pots seemed to be off (with a wiring or soldering problem...) I am really confused and I would appreciate if you could help me ! (Also the noise doesn't get any louder when touching specific parts)
That definitely sounds like a grounding issue, that's exactly how to diagnose one! There should be continuity from the strings to the jack, if there is, maybe the ground connection is poor and needs to be reinforced with more wire.
I have a question, I have a Warwick Corvette Std. and it picks up radio noise to the point that I can’t record with it at all, and it has active pickups/electronics. However, my fender Jazz Bass with passive pickups/electronics and strat both pick up no radio noise. How would you go about fixing this? Putting a whole new electronics circuit and pickups in it?
@@matthewmorter7803 my Warwick had noisy pups too. Could be a potting or shielding issue. I just put in a Bartolini split coil that was the same size and that's much quieter. A bit expensive, but I tried shielding first and that didn't help
@@NickLeonard thanks for the advice, but it’s not just white noise, it’s picking up clear voices from the radio, did you have that issue as well? And do you mean you out in basically a noiseless single coil pick up and that solved your issue without replacing all the electronics?
@@matthewmorter7803 yes, a noiseless single coil, split coil, so a humbucking single coil. You can try shielding the electronics cavity better with copper tape, but you may not see any real benefit. It could be poor potting on the pickups, but easiest fix for that is new pickups. Just measure carefully as bass pickups are many different sizes
@@NickLeonard thanks! A tech told me shielding wouldn’t help when I took it to them, they said everything was dead quiet in their shop, it must just be because I am under the radio towers, but I may try noiseless pups, thanks
Most Ibanez active bass's use passive pickups with an active 9v 3 band eq....my old SRX360 had an active 2 band eq, blend & master volume...now it is passive with a brass nut, 8% CTS linear 500k pots, fully pro sheilded, new wiring throughout, Greasebucket tone controls, 2 x 5% hifi grade polypropylene caps & a 1% 4K7 resistor per Greasebucket tone pot...set up with 2 volume & 2 tone pots...all linear 8% CTS, the PFR pickups sound far better now as standard passive pickups rather than with the 2 band eq with the bass pot set at 40hz & treble pot at 10k...a bit bright for me...far better tone now with Greasebucket tone pots & passive....
Dunno - the noise is still very much there (just sounds different), yet clean bass with no preamp sounds worse. To each his own I guess. I have the same one - SR500, but a newer model with a preamp bypass switch.
The noise sounded quieter because the blend pot was 25k and significantly darkening the tone. I replace volume and tone with 1M and it sounds much more similar to the preamp tone again, the noise is lower still but it's not so drastic anymore
I have an Ibanez SRX500 active bass. The issue I’ve had is that I’ve gotten no sound / signal from this bass when I plug it into an amp. I’ve changed out the 9v battery but to no avail. Is there hope? Am I able to bypass the 9v, this converting the bass to a passive one? It’s bothered me for quite a while. I’d rather not pay somebody the cost of the bass to have this remedied either so I’m just looking for solutions.
Have you checked all the connections? Might be a dead jack, mine was dodgy so I replaced it. Maybe a bad pot or something broken in the preamp. If you do this preamp mod, swap the blend and volume for 500k or 1M pots at the same time. Be sure the blend pot is a real blend pot with 6 legs.
Cool vid. Very detailed. I have a GSR 205 and I didn't like the slight noise and I didn't like the idea that I had to have a battery in there to play the guitar (dead or alive). So I removed the Phat II along with the pot it was on and plugged up the hole. So now the sound of each pickup is a little strange when they are by individually, however when both pups turned up to max they sound great. Not sure if this was caused by a wiring error on my part but I do love the sound and the quiet background. Great vid! TYFP! (PS: I now use the battery compartment to store extra picks!)
Those remaining 25KΩ and 50kΩ pots are going to load the pickups down a bit, not necessarily a *bad* thing, there will be less output and the treble response will be reduced considerably. If it bothers you then replace the blend pot with a switch and put in a 250kΩ or even 500kΩ pot for the volume control.
Didn't find a rotary switch that would be easy to drop in, but I put in a 500K blend pot instead. Difference is night and day! The bass is bright and clear now. I'll post a short clip in the next video!
NICE, I will do it on my Ibanez Gio Bass, I searched for the wiring diagram and looks more simple to bypass the active circuit, I just need remove the battery, conect IN/OUT from that stupid boost knob on "Ibanez GSR205 stock wiring" so it is bypassed to the pots, that active circuit only makes my signal clip and get some complaints from the audio tech guy
I have this exact bass, and a while ago, an issue with the treble boost knob came up. Initially I couldn't turn it all the way up because it would make the bass loud enough to the point it would distort. Now recently, no sound will come out of the bass anymore unless I mess with the treble boost knob. Any idea what might be the issue?
Not off the cuff, but it's possible there's some dead spot in the pot that's cutting out the signal, I don't know how likely that is. It could also be something failing in the preamp, though that's pretty sturdy too, not much to break. Maybe a loose wire, and turning the knob is somehow fixing the connection. Only real way to find out is to probe around under the hood or take it to a tech!
This is awesome! I stumbled onto this while looking for a wireless system for a bass with active pickups. I have an SR500 that I also do not use the EQ knobs. Gonna disconnect the preamp board and update the pots. So 500k for the volume and a 500k blend pot?
Yes, or even 1M pots. I did find that some of the noise came back with proper pots, this video "fixed" the noise but cutting out a lot of treble... but I'm still happier with the tone now. For a true noiseless solution, I think replacing the pickup is the only way to go, though extra shielding in the cavities also seemed to help some
Man, I’ve been tearing my hair out trying to fix the noise issues in my RGB305 so this vid is exactly what I was looking for. I’m a total novice with this stuff so I was had a few quick Qs if that’s okay? 1. If I just wanted a volume and a pickup blend, nothing else, once I’m done there shouldn’t be anything else other than the two pots, the jack, and a few wires connecting everything, is that correct? I can remove all the rest of the circuitry? Total noob here lol 2. Can I use the original pots or would I need to get new ones? Thanks!
1. Yes, you can remove the eq electronics, I left mine so there isn't a bunch of holes, but only the vol/blend are actually connected to the circuit. 2. You can use the stock pots, but you may want to change values for tone reasons. Check the values, they should say on the back. My volume was 500k, which was fine, but the blend was only 25k, which darkened up the tone a lot. I would swap that for a 500k as well and then the brightness is back. If you have the mk1 pickups, they're still a little noisy, but it is better.
@@preciseaudioblog you need to check that the ground is fully connected everywhere - from the output jack through the electronics and to the bridge. A multimeter with a continuity checking function helps a lot. It probably just came loose somewhere and needs to be resoldered
500k for volume, but only 25k for blend. Replacing the blend knob made the bigger difference in the end, but I hadn't put it in when I made this video. Will demo it soon.
@@NickLeonard wow the sr500 series are really strange...some basses like my bass sr506 without mid switch with mk1 preamp....have a 25k in volume pot and ac25k for blend... And some models have 500k with mk1 preamp... Is really curious
@@ronaldcardenas796 I found a number of wiring variations for the soundgear series over the years. I guess it depends on parts price, though they have some different preamp wirings too for some reason.
I'll have to post an update video on it, but after I posted this one, I swapped out the 25k stock blend pot with a 500k. That added back the brightness that was lost, but also with it came the noise, not sure if it's as noisy, and I like the tone better now, I also shielded the pickup cavities, which have graphite pain, but I added a few layers of copper all around and that seemed to help at least on the bridge pickup, which is oddly like 10 dB less noisy than the neck now. Overall, it's an improvement, and the noise is only really audible if I'm running really high gain, so it's perfectly usable. I think to fully fix it, I'd need a new pickup like the Bartolini MK5, which is the right size. I put a US-made Bartolini humbucker in my noisy Warwick and it's totally silent now.
@@NickLeonard thanks. i think i have to start with the 9 volt connector. For years i thought the cable jack was bad/loose. but recently realized that no 9 volt connector should require this much strength to use. moving a connected 9 volt battery around in the slot caused the sound to cut in and out.
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Thank you so much! With the schematics here I was able to rewire my SR500 to a passive after the preamp failed. Got a working bass again, and don't have to worry about the battery :)
The preamp is actually an input buffer and eq. The high impedance drops after buffering and the pickups reach the blend pot buffered. That's why it's just 25KOhms while the pickups are passive. The 25K blend is too low a value to directly connect your pickups to.
And that's why you lose so much treble with "Preamp Bypassed". Get a 250K or 500K MN taper blend, like, yesterday. Thank me later when you have all your treble back and no noise.
someone pointed that out when this came out, and yeah I swapped in 1M pots, it's at the top of the description. some of the "noise" that was removed was just treble, so it's hard to say if this really reduced the noise much in the end, but I still like having it passive.
@@NickLeonard you could shield the electronics cavity and also the pickup cavities (connecting them to the grounded electronics cavity). Shielding paint will do but copper foil is best.
I realized the noise goes up as the battery goes down 😮.
When I had a newer SR505 I actually considered removing the preamp but I didn't want a passive bass, so I wound up blowing a ton of money on a Dingwall, simply because I still wanted an active bass that sounded better. Especially when recording I'm definitely not a fan of passive guitars, let alone basses, and thankfully my new 10-string guitar had Fishman Fluence Moderns, which, while I was hoping for something better, it at least had active pickups which still saved my recording sessions.
I'm late to the party but if I were to pursue a project like this and wanted maximum treble out of the pickups, I'd wire it Volume, Volume like a Jazz Bass without the Tone control. That eliminates the effects of the Blend pot.
One of the key take-aways should be that if the bass has passive pickups and if either balance/blend or volume pots are in the 25K to 50K ohm range, they should to be replaced with values more traditionally suitable for passive pickups, aka 250Kohms and up.
I may return my sr500e, I really feel the active EQ is gimmicky, especially for a bass. Active pickups maybe not.
Dude active pickups do not need a preamp its built into the pickup. Active basses with passive pickups have a preamp like you are talking about. And like your saying removing the preamp us fine.
I’ve got the SR500. I have the treble control permanently turned down to remove the brightness from the preamp. It’s not noisy luckily but going passive is definitely on the cards soon
Nice !
I did get a pair of Bartolini MK1 a while back, for just 15€ used :D
I put them in my Ibanez EDB600 (which I got for under 50€) that had a dead bridge pickup and dead preamp.
This was not the first pickup change I did in that one (used a dual blade Belcat guitar pickup at the neck position for a while), but in the end the Bartolini are much better than what originally came with that Bass.
I seen plenty people complain about the preamp which usually comes with these Bartolini Mk1.
One thing with these ; they have a pretty low output (and ohm reading) and I have to use a clean boost in the chain when I use this specific Bass. (as seen in my latest vid)
I would suggest leaving any blend pot out and instead use a DPDT switch to have Series/Parallel option, which is really good with these 😁
The wiring in my EDB600 ended up kinda weird with a dual-tone pot with a switch between two capacitor values.
But really it was an excuse to populate the empty holes left by the preamp 😅
Part of me would live to rip everything out my Ibanez and just have a volume knob and pickup selector switch BUT I do like the brightness.
Its just a headache having EQ on the guitar and an EQ in my signal chain AND on the amp plus whatever pedals with their tone options. Too many variables.
Concluding it might be better to leave the Ibanez alone and just buy a Squire P bass so have both options.
Or of i can get another SR cheap pre-owned mod that one.
The brightness loss was really because the blend and volume pots are super low values for a preamp. Stick 1M or 500K parts in and you're fine. Of course, some of the "noise reduction" in this video was just treble being lost, so I don't know if this mod really reduces noise, but it's nice to have it passive anyways
That's an insane amount of detail in the info! I was just looking to replace a barrel jack in my 305M, but this is an interesting idea, have to look into what the stock pick ups are in mine 🤔 stellar work!
Hi there, very useful and informative video! I have an Ibanez BTB series bass and I have a constant noise that goes away when touching ANY METAL PARTS OF THE CIRCUIT, and that includes the Metal parts on the amp, the Multi-effect , bridge, strings , preamp knobs and etc... could this still be a grounding issue? I tested back of the cavity with a multi meter and some parts seemed to have "continuity" , whereas some of the pots seemed to be off (with a wiring or soldering problem...) I am really confused and I would appreciate if you could help me ! (Also the noise doesn't get any louder when touching specific parts)
That definitely sounds like a grounding issue, that's exactly how to diagnose one!
There should be continuity from the strings to the jack, if there is, maybe the ground connection is poor and needs to be reinforced with more wire.
I have a question, I have a Warwick Corvette Std. and it picks up radio noise to the point that I can’t record with it at all, and it has active pickups/electronics. However, my fender Jazz Bass with passive pickups/electronics and strat both pick up no radio noise. How would you go about fixing this? Putting a whole new electronics circuit and pickups in it?
@@matthewmorter7803 my Warwick had noisy pups too. Could be a potting or shielding issue. I just put in a Bartolini split coil that was the same size and that's much quieter. A bit expensive, but I tried shielding first and that didn't help
@@NickLeonard thanks for the advice, but it’s not just white noise, it’s picking up clear voices from the radio, did you have that issue as well? And do you mean you out in basically a noiseless single coil pick up and that solved your issue without replacing all the electronics?
@@matthewmorter7803 yes, a noiseless single coil, split coil, so a humbucking single coil. You can try shielding the electronics cavity better with copper tape, but you may not see any real benefit. It could be poor potting on the pickups, but easiest fix for that is new pickups. Just measure carefully as bass pickups are many different sizes
@@NickLeonard thanks! A tech told me shielding wouldn’t help when I took it to them, they said everything was dead quiet in their shop, it must just be because I am under the radio towers, but I may try noiseless pups, thanks
Most Ibanez active bass's use passive pickups with an active 9v 3 band eq....my old SRX360 had an active 2 band eq, blend & master volume...now it is passive with a brass nut, 8% CTS linear 500k pots, fully pro sheilded, new wiring throughout, Greasebucket tone controls, 2 x 5% hifi grade polypropylene caps & a 1% 4K7 resistor per Greasebucket tone pot...set up with 2 volume & 2 tone pots...all linear 8% CTS, the PFR pickups sound far better now as standard passive pickups rather than with the 2 band eq with the bass pot set at 40hz & treble pot at 10k...a bit bright for me...far better tone now with Greasebucket tone pots & passive....
I did the same thing to my bass … the improvement is huge
Dunno - the noise is still very much there (just sounds different), yet clean bass with no preamp sounds worse. To each his own I guess. I have the same one - SR500, but a newer model with a preamp bypass switch.
The noise sounded quieter because the blend pot was 25k and significantly darkening the tone. I replace volume and tone with 1M and it sounds much more similar to the preamp tone again, the noise is lower still but it's not so drastic anymore
I have an Ibanez SRX500 active bass. The issue I’ve had is that I’ve gotten no sound / signal from this bass when I plug it into an amp. I’ve changed out the 9v battery but to no avail. Is there hope? Am I able to bypass the 9v, this converting the bass to a passive one? It’s bothered me for quite a while. I’d rather not pay somebody the cost of the bass to have this remedied either so I’m just looking for solutions.
Have you checked all the connections? Might be a dead jack, mine was dodgy so I replaced it. Maybe a bad pot or something broken in the preamp. If you do this preamp mod, swap the blend and volume for 500k or 1M pots at the same time. Be sure the blend pot is a real blend pot with 6 legs.
Cool vid. Very detailed. I have a GSR 205 and I didn't like the slight noise and I didn't like the idea that I had to have a battery in there to play the guitar (dead or alive). So I removed the Phat II along with the pot it was on and plugged up the hole. So now the sound of each pickup is a little strange when they are by individually, however when both pups turned up to max they sound great. Not sure if this was caused by a wiring error on my part but I do love the sound and the quiet background. Great vid! TYFP! (PS: I now use the battery compartment to store extra picks!)
Those remaining 25KΩ and 50kΩ pots are going to load the pickups down a bit, not necessarily a *bad* thing, there will be less output and the treble response will be reduced considerably. If it bothers you then replace the blend pot with a switch and put in a 250kΩ or even 500kΩ pot for the volume control.
I put in a 1M volume pot, it's still a bit dark though. Maybe I'll put in a pickup switch, though I like the look of the blend knob
@@NickLeonard You need a Rotary switch..! The blend knob is two 50kΩ sections in parallel so still loading the pickups with 25kΩ
@@zmix ah, that explains it. I'll get one and put it in! cheers!
Didn't find a rotary switch that would be easy to drop in, but I put in a 500K blend pot instead. Difference is night and day! The bass is bright and clear now. I'll post a short clip in the next video!
I plan on swapping the op amp. I quite like the preamp, but a tl062 just is not a low noise op amp
NICE, I will do it on my Ibanez Gio Bass, I searched for the wiring diagram and looks more simple to bypass the active circuit, I just need remove the battery, conect IN/OUT from that stupid boost knob on "Ibanez GSR205 stock wiring" so it is bypassed to the pots, that active circuit only makes my signal clip and get some complaints from the audio tech guy
Check the value of your blend pot while you're at it, might want to replace that with a 500k, 25k is too low
I have this exact bass, and a while ago, an issue with the treble boost knob came up. Initially I couldn't turn it all the way up because it would make the bass loud enough to the point it would distort. Now recently, no sound will come out of the bass anymore unless I mess with the treble boost knob. Any idea what might be the issue?
Not off the cuff, but it's possible there's some dead spot in the pot that's cutting out the signal, I don't know how likely that is. It could also be something failing in the preamp, though that's pretty sturdy too, not much to break. Maybe a loose wire, and turning the knob is somehow fixing the connection. Only real way to find out is to probe around under the hood or take it to a tech!
This is awesome! I stumbled onto this while looking for a wireless system for a bass with active pickups. I have an SR500 that I also do not use the EQ knobs. Gonna disconnect the preamp board and update the pots. So 500k for the volume and a 500k blend pot?
Yes, or even 1M pots. I did find that some of the noise came back with proper pots, this video "fixed" the noise but cutting out a lot of treble... but I'm still happier with the tone now. For a true noiseless solution, I think replacing the pickup is the only way to go, though extra shielding in the cavities also seemed to help some
Man, I’ve been tearing my hair out trying to fix the noise issues in my RGB305 so this vid is exactly what I was looking for. I’m a total novice with this stuff so I was had a few quick Qs if that’s okay?
1. If I just wanted a volume and a pickup blend, nothing else, once I’m done there shouldn’t be anything else other than the two pots, the jack, and a few wires connecting everything, is that correct? I can remove all the rest of the circuitry? Total noob here lol
2. Can I use the original pots or would I need to get new ones?
Thanks!
1. Yes, you can remove the eq electronics, I left mine so there isn't a bunch of holes, but only the vol/blend are actually connected to the circuit.
2. You can use the stock pots, but you may want to change values for tone reasons. Check the values, they should say on the back. My volume was 500k, which was fine, but the blend was only 25k, which darkened up the tone a lot. I would swap that for a 500k as well and then the brightness is back. If you have the mk1 pickups, they're still a little noisy, but it is better.
@@NickLeonard amazing, thank you!
Hi! I installed a J Retro preamp on my bass and is noisy. Could it be the ground cables inside? Thank you
That's always the first thing to check. You can diagnose that by seeing if the noise goes away when you touch the strings or bridge
@@NickLeonard Hi. Yes, the noise stops when I touch the bridge and or strings. If the cables are not the problem, what could it be? Thank you.
@@preciseaudioblog you need to check that the ground is fully connected everywhere - from the output jack through the electronics and to the bridge. A multimeter with a continuity checking function helps a lot. It probably just came loose somewhere and needs to be resoldered
@@NickLeonard Thank you!
What was the original value of the volume pot?... 25k?
500k for volume, but only 25k for blend. Replacing the blend knob made the bigger difference in the end, but I hadn't put it in when I made this video. Will demo it soon.
@@NickLeonard wow the sr500 series are really strange...some basses like my bass sr506 without mid switch with mk1 preamp....have a 25k in volume pot and ac25k for blend... And some models have 500k with mk1 preamp... Is really curious
@@ronaldcardenas796 I found a number of wiring variations for the soundgear series over the years. I guess it depends on parts price, though they have some different preamp wirings too for some reason.
My SR705 is noisy as hell. It's idiotic.
I'll have to post an update video on it, but after I posted this one, I swapped out the 25k stock blend pot with a 500k. That added back the brightness that was lost, but also with it came the noise, not sure if it's as noisy, and I like the tone better now, I also shielded the pickup cavities, which have graphite pain, but I added a few layers of copper all around and that seemed to help at least on the bridge pickup, which is oddly like 10 dB less noisy than the neck now.
Overall, it's an improvement, and the noise is only really audible if I'm running really high gain, so it's perfectly usable. I think to fully fix it, I'd need a new pickup like the Bartolini MK5, which is the right size. I put a US-made Bartolini humbucker in my noisy Warwick and it's totally silent now.
@@NickLeonard thanks. i think i have to start with the 9 volt connector. For years i thought the cable jack was bad/loose. but recently realized that no 9 volt connector should require this much strength to use. moving a connected 9 volt battery around in the slot caused the sound to cut in and out.
just upgrade to a Aguilar OBP-3TK