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| Need help with a client's problem... http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10123&t=27223 |
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| Author: | clavin [ Sat May 01, 2010 9:51 am ] |
| Post subject: | Need help with a client's problem... |
Hi Guys- Here is a quote from an e-mail describing an odd problem with an Ibanez bass. Any of you have a similar experience? Any one know how to fix this? Thanks, Craig Lavin "It's hard to explain the problem because it's been rather complicated. I have been playing a Spector Euro bass with active EMG pickups. I bought an Ibanez because after many years of back and neck issues I decided I needed to find a lighter bass. I was looking at the SR line, and happened to find someone selling a new bass she had won, never played, still in the carton. It's relatively high-end for Ibanez..nice neck thru, active pre-amp with Bartolini passive pickups-new for me to have an active bass with passive pickups. Anyhow, I got to practice with my band which is the first time I played it through the rig I use at gigs, and it made a lot of noise-like the usual mid-range humm but way too loud. I took it to a local guy who switched out the stock pre-amp for an EMG preamp. I got it back, better, but still noisier than I am used to. He then put some copper shielding behind the pickups and reversed them (one was noisier and I guess he thought it would be better in the other position). It was then fine at practice. I took it to a gig, and after about 5 songs I started getting major feedback humm from my amp and I lost about 70% of my sound. I grabbed my Spector and finished the gig, no problem The following weekend I brought both basses to my gig to try and figure out what was going on. The Ibanez immediately caused a high end squeal-like microphonic feedback, and my sound dropped out. I switched to the Spector and it was better, but I had to keep a couple of feet away from the amp. I checked them out at the break and both basses caused the squeal and loss of power, so I figured it was the amp (Ampeg SVT III). I have used this rig with my Spector for the last couple of years, never had a problem. I took the amp in to the best electronics music place in town, and they could not find anything wrong with it. I then took the Ibanez into a local music store and played through a bunch of equipment. All was fine until I plugged into an amp that was at the level of my pickups, and the squeel/power loss happened again. Now I have an amp that is acting up with both basses, and a bass that is causing the problem with multiple amps.... I go back to the electronics place this time with both basses and my cabinet and we replicate the problem..both basses cause the high end squeal and power loss. I have talked to people all over town, and all over the country. The best info I get is that the Ibanez probably has something loose that sets up an oscillation, and then it happens with the Spector because the amp is already reacting. I did not turn my amp off inbetween switching basses, only hit the mute button, so maybe that's why it was still acting up with the Spector. I went back to the electronics place again (my amp was still there) to test out the theory, but we could not get the reaction with either bass. The guy at the shop suggested putting a cap in the input jack of the Ibanez, so that the high end frequencies that I don't need to produce for my sound will get filtered out. I have a gig tomorrow night, and have no idea what to expect! It may be that the cap will solve the problem, although the source has not been detected or corrected." |
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| Author: | MRS [ Sun May 02, 2010 1:03 am ] |
| Post subject: | Re: Need help with a client's problem... |
Could be that the pickups where not potted correctly. That is sealed in wax and taped around the pickup to prevent squeal and hum at loud volume. If not potted the windings can vibrate against each other causing these problems. If he's an active pickup man maybe a swap to EMGs in the new bass will be and end to his problems...Mike |
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| Author: | clavin [ Sun May 02, 2010 4:58 am ] |
| Post subject: | Re: Need help with a client's problem... |
Thanks Mike, I'll send this info out to them, Craig |
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| Author: | theguitarwhisperer [ Mon May 03, 2010 2:00 am ] |
| Post subject: | Re: Need help with a client's problem... |
If he plays with his EQ's cranked, that can cause feedback. Also, if he has the wrong value pots for the bass mid and treble pots that can cause feedback. Should be 50K or less. Does he have an 18-volt system? If it was accidentally wired in parallel instead of series, that can cause problems as well. I mix passive pickups with active EQ systems all the time. I'm very familiar with the EMG EQ systems, they work well with passive pickups. The pickups need 250K or more for the volume and blend pots, which then output to the EQ system. The EQ portion of the pramp system needs 50K or less pot values, and the EMG systems use 25K specifically. |
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