Excessive Feedback, Dimarzio Dp222 Hb's

[chrisr]

Greetings, first post.

I just finished a 6 month build on a Precision Kits Les Paul Junior double cut away routed for two humbuckers. I put Dimarzio DP222 (bridge) and DP221 (nexk) D Activator X Humbucker pickups in it and used a Toneshaper for Les Paul with the Borsch 500k push/pull tone pots for single (north) coil tap on the neck and series/parallel on the bridge. I have it dialed in pretty good now with about a 3/16's rail to string spacing. I am playing through a Rocktron Voodu Valve Witch Doctor pre-amp and using a TC Elect compressor.

I am having terrible problems with high-frequency feedback on the bridge humbucker. It'll start a feedback loop and the only way to stop it is to turn down the volume on the bridge or de-select it on the 3-way. Also lower frequency feedback but I can control that by muting the strings with my palm. The high-frequency feedback however is a direct self-sustaining loop that has nothing to do with string vibration. The high-frequency feedback loop will stop if I start playing but will start again if I tap ("ding!") the PU ring with my pick (as a test). Or if I just leave the bridge volume open all the way and wait a few seconds :\

I have tried increasing the HUSH on the Rocktron and that helps but sheesh I have it dialed up almost all the way to max and that is not normal. I have also tried playing with the PU height, low, way low, kills tone and articulation and doesn't seem to help much. Happens in both parallel and series on the bridge whenever I turn my amp up to a moderate level.

The neck PU also has shown some high-freq feedback issues, but the Rocktron HUSH circuit took care of that at a moderate setting. I have also tried by-passing the compressor and that helps some but I really like leaving that compressor on.

I wanted to see if anybody here on the forum has had problems like this and what, if anything, can be done to control it. It may be that I just need to dial in some new settings on my pre-amp and tube head (a ENGL stereo rack 100W) specifically for the LPJ/Dimarzios but I would really like to have a "shared" setting that works for my Tele (with GFS pups) and Strat (with Dimarzio rail stacked humbuckers), neither of which display this feedback problem, at least to the extent I am seeing with the D Activator's.

Thanks!

[SwedishLuthier]

Welcome to the forum

When reading the description it sounds like you have microphonic feedback. The difference between "normal" feedback (you know, the Jimi Hendrix style we all like...) and microphonic feedback is this: The "normal" feedback is caused by the sound of the speaker making the strings vibrate, this vibration being amplified and send to the speaker that makes the strings vibrate stronger. It is a musical type of feedback. With the microphonic feedback it is not the strings that vibrate but the tiny magnet wire inside the pickups. This is often a high pitched squeal. Also not a very musical feedback. The frequency of the feedback is one thing that makes me think it is microphonic feedback. The other thing is that it doesn't die when you mute the strings (as the problem isn't that the strings vibrate...).

So what to do about it? There are a few things and apart from the most complicated solution I generally don't think that you will like any of them but here we go...

- "Pot" the pickup. This is the method of submersing the pickup in hot wax to solidify the coil and stop the wire from vibrating. Probably something you need to have a pro do as it also can ruin your pickup(s) if done wrong. And that was the solution you might like. next up are:

- Lower the volume of the amp

- Lessen the gain on the amp

- Lessen the compression used

- Increase your physical distance from the amp

And as you have problems with both pickups (although the bridge is the worst one) I think it is a combination of the last four you need. And when looking at you choice of pickups and amp I guess you know what sound you are after and then you need all that gain/volume/compression. Hairy problem...

[chrisr]

"microphonic feedback" -- that is the term I was looking for and definitely what is happening. It has nothing to do with string vibration (the "good" feedback we know/love), but a uncontrollable squeal that is the audio from the amp re-entering the signal chain directly through the pickup coils.

You are right about turning down or backing off gain *not* being an option; I'm not pushing it that hard anyway; I am in a home studio environment and if/when I play out, with a live drummer and open up that ENGL and the 2X12 Marshall cab -- man it's gonna be bad (in a very unfavorable way).

I would think that Dimarzio would pot their pickups better to avoid this. The D-Activator series are not exactly "boutique" but not cheap "consumer grade" either and then there is the Dimarzio name. I may send them a note asking about it.

I have a hot glue gun I *could* use to permanantly pot the entire bridge pup but frankly, if this is an issue that can be resolved with a better set of pups, I will ditch the D-Activator's on eBay and go that route.

Anybody else here with Dimarzio D-Activator X series DP221 and DP222 pickups having this problem?

Thanks for the information and advice

[curtisa]

Is it a new pickup? You could probably get your money back or an exchange if it's actually faulty. The only humbuckers I've ever heard go microphonic were extremely poor quality ones to begin with. A modern Dimarzio shouldn't suffer from those issues.

Can you swap out the pickup to see if the microphony follows the pickup? Even swapping neck and bridge temporarily?

Do you have any other issues with the pickup (excess noise or buzzes)? Always good to check for wiring errors - it'd be a shame to write off an expensive set of pickups if it was just a case of a simple wiring mistake.

[guitar2005]

I agree with curtisa. Try another pickup as a test. I've been using Dimarzios for 30 years and never had issues with them being microphonic.

[SwedishLuthier]

OK, not for the weak at heart: Wax potting pickups by Lindy Fralin

It it is a new pickup, try to have it exchanged before doing this as it will void the warranty

Edit: Do you by any chance have mounted covers on the pickups? If so that is most likely the problem as a non-potter, after-potting mounted cover will squeal like ...yeah you know. Potting a new cover

[chrisr]

I don't have any covers on these pickups, they are sitting in metal slanted rings I sourced from StewMac. They test out okay with my meter (base plate continuity to ground) as well as the mounting rings.

I *do* have substantial copper sheilding in the pickup cavities but that is well grounded.

The pickups don't hum or make buzzing noises, at least in a humbucking configuration. The series setting on the bridge PU does buzz a little as well as the single coil tap on the neck.

I am using a Toneshaper for Les Paul and the bare and ground wire on the pickups is connected to the Toneshaper terminal block where it is supposed to be.I did reverse the green and red/white wire connections on the Toneshaper terminal block to resolve an out of phase problem. They sounded thin and weak and reversing phase helped a lot.

I have a set of GFS humbuckers I can swap in and see if they display the same issue. Dimarzio just got back to me on my email from this morning and suggested they may need to be repotted and offerred to do so if I send them in. I am gonna try swapping the GFS pups in first and see if the problem follows the pickups, if so I will send the D-Activators back to Dimarzio.

I am also going to try raising the Dimarzio's up to 1/8 or less to the strings and reduce the input gain on my pre-amp.

[curtisa]

Might also be worthwhile trying the guitar with the Toneshaper board removed and wiring it up as a "normal" Les Paul.

One other thing worth having a look at - double-check your wiring from each pickup to the Toneshaper. I notice that the manual mentions that the colour codes marked on the Toneshaper terminal block are for Seymour Duncan pickups. The Dimarzio colour codes are quite different.

[chrisr]

The Dimarzio colour codes are quite different.

PROBLEM SOLVED.

Thank you curtisa, that was it. I had wired the Dimarzio's using the color codes printed on the Toneshaper terminal connection block which as you point out is per Seymore Duncan color codes, *not* Dimarzio.

When I went back and redid the connections, using the Dimarzio wiring color codes for North/South Start/End, the squealing feed back problem went away *plus* the parallel mode on the bridge and single coil tap on the neck took on new life (more articulate and full-bodied, etc.) and the pickups smoothed out tonewise, big-time. The D-Activator's sound great, really hot, maybe a bit on the excessively bright side so I am playing with pickup height to dial that in exactly the way I want it.

Here I was, ready to pull them out and send them to Dimarzio for re-potting. Lesson learned.

Sorry, would have posted sooner but I've been too busy jammin' on my new axe

Thanks a lot.

[curtisa]

Good to hear it was an easy fix. Time to roxxorz