Magnet mod with BlackTop FilterTrons--Closer to nirvana!!

[boots64]

Hey gang,

Just wanted to share with you all a mod I performed today on my Electro G5622t. So, this guitar came stock with Blacktop FilterTrons . I have to say, after hearing how awesome HS FilterTrons sounded in my G2622 Streamliner (I bought that guitar previously and upgraded pups, knobs, etc. I'll post a pic of that guitar as well), I was finding the Blacktops too harsh and "ice-picky" for my taste. So...I started reading some posts here on magnet swaps and their effect on tone.

My first thought was to replace the 1/8 inch thick Alnico V magnet in the Blacktops with 1/4 inch Alnicos; the magnets used in the HS FilterTron and see what kind of results I got--yes, the newer Blacktops do, in fact, have Alnico magnets, for anyone who still thinks Gretsch is using ceramic.

After scouring the internet, I could only find one website that carried an actual spec replica of the 1959 Alnico magnet designed specifically for replacement in the HS. FilterTron. He was out of stock, of course!

So, I decided to use the 2nd 1/8 Alnico V from my Streamliner BroadTron pups (gathering dust) and stack them with the existing magnet in Blacktop to "make" a 1/4 inch Alnico V.

Stacking the magnets was not that difficult. The hardest part was getting the pup cover separated from the baseplate of the pickup. Once I got that off, it was just a matter of unscrewing the pole screws a bit to allow the other magnet to slide underneath the existing magnet. I also needed to buy 4 3/4 inch screws to screw the baseplate back on because of the added depth. Anyway, doubling the magnet made a HUGE difference in the sound!!!! Very, very close the the HS FilterTrons now! For anyone that's not happy with the sound of their Blacktops, this is a fairly easy mod that will give very pleasing results. Here are some pics (Sorry, I should have taken more step by step pics...)

 

[Synchro]

Very cool! That’s only the second time I’ve heard of anyone modifying pickups via the magnets. Assuming it doubled the strength of the magnetic field, I would imagine that it changed the tonal characteristics somewhat, perhaps favoring the fundamentals to a somewhat greater degree. A bit more power can be nice too.

Chet Atkins actually chose a blacktop for the bridge position of his ‘59 Country Gent. I guess it was a Baldwin era pickup that he found to be the perfect counterpart to the Supertron in the neck position.

Pickups are my area for experimenting, although I let the folks at TV Jones do the hands-on with the pickups and I just do the pickup swaps. I’ve found a lot of interesting combinations, mostly with Supertrons and variants thereof. Ray Butts had some great ideas which have evolved into the various Filtertrons, Supertrons and Duo-Trans we have today.

 

[TSims1]

.........Duo-Trans we have today.

Wait, is that like a Filter that feels like it’s a Dyna?

 

[Synchro]

Wait, is that like a Filter that feels like it’s a Dyna?

I had never thought of it in those terms but it is a Filter with exceptional clarity and balance.

 

[boots64]

Thanks for the reply, Synchro. That's interesting about Chet Atkins liking the Baldwin era Blacktop in his bridge pup...I guess I have an unfounded bias against pickups with ceramic magnets in them. I have always equated: ceramic=inferior sound, Alnico=vintage and better sound. Not really a fair assumption because I've never played a Gretsch Blacktop with a ceramic magnet before, so I really don't know what they sound like! Anyway, I saw a pic of a Baldwin era Blacktop taken apart from another post on this website. I'll post the pic. Looks like they used a 1/4 inch magnet back then. I wonder how the modern Blacktops sound in comparison to the Baldwin era?...

 

[MikeSchindler]

I wonder if there is any difference in metal pole pieces between the Filtertron and Blacktop which relates to the sound.. I think someone told me that the pole screws on tv jones are different compared to the hs filters which relates to the overall sound though I find it hard to believe there would be a difference that would be discernible really.. anyone have experience with this?

 

[MikeSchindler]

I think the ceramic filters I had in an older 6122 sounded more full and balancecwas exceptional .. but a bit darker in that guitar.. less chime .. less three d or texture.. more straightforward , pronounced mids

 

[MikeSchindler]

Has a lot to do with the guitar.. the body, the bracing and plys cause I also had the same pups in an older 6120-60. ..quite a difference in the sound..

 

[Geckomecca]

Hello Boots64!!
I am so happy to read the great info you shared in this posting from December. I purchased a Pro Jet not long ago and was thinking of swapping the Blacktop Filters for HS Filters (I have two other guitars with HS FTs and just absolutely love them). I like the look and feel of my new Pro Jet and hope to make it my number 1. Your input about the magnet upgrade is the perfect and simple solution as I really don't want to pull out the guts or splice/solder any wiring as it all looks so neat and tidy. The BT FTs really sound great too, but I still give the edge to the HS Filters. One quick question for you if you don't mind- do I have to "charge" or prep the magnets in some way prior to install or just stack them on top of the existing 1/8" Alnico 5's. Thanks for your help and info. What a great site with great people. Thank you!
- gecko

 

[imguitardan]

Hello Boots64!!
I am so happy to read the great info you shared in this posting from December. I purchased a Pro Jet not long ago and was thinking of swapping the Blacktop Filters for HS Filters (I have two other guitars with HS FTs and just absolutely love them). I like the look and feel of my new Pro Jet and hope to make it my number 1. Your input about the magnet upgrade is the perfect and simple solution as I really don't want to pull out the guts or splice/solder any wiring as it all looks so neat and tidy. The BT FTs really sound great too, but I still give the edge to the HS Filters. One quick question for you if you don't mind- do I have to "charge" or prep the magnets in some way prior to install or just stack them on top of the existing 1/8" Alnico 5's. Thanks for your help and info. What a great site with great people. Thank you!
- gecko

It depends. Most magnets I've bought come charged.

 

[GCKelloch]

Hiya, hiya, all. This is my first post on this site. I was intrigued by this thread because I just bought a set of Blacktops for a project build. I find AlNiCO V powered Steel core HB's to have a harder attack character than I like, and the guitar will have a rather bright sounding Wenge neck w/stainless frets, but with a Walnut center w/Roasted-Poplar wings body for strong bass and mids.

I not sure the intended goal of adding a more powerful magnet, but I think the HS models sound warmer mainly because the Brass cover is over most of the coil. The longer screws in the HS would actually draw more of the magnetic flux away from the pole screw heads, so they aren't necessarily more powerful pickups. The Blacktops might sound more like them if one of the pots is 250k instead of 500k, but I am speculating.

It's more likely stacking the magnets actually reduced the flux in he pole screws. I tested the polarity of some extra A4 bar magnets with another magnet, and they can only be stacked if the poles are aligned so that the flux lines wrap around into each other at the ends facing the pole screws. The second magnet would be drawing flux from the first, which I'd assume would draw flux away from the pole screw heads so output is reduced and the attack is a bit sweeter/fatter.

I plan to try a much easier fix that should actually increase efficiency while reducing flux at the pole screw heads. Steel has much higher permeability than AlNiCO V. Attaching a Steel plate to the bottom of an AlNiCO V powered pickup draws flux from the strings down more through the coils, as well as reducing flux in the pole screw heads. The pickups should be louder and warmer. It should not have significantly less high end than eddy currents from the diamagnetic Brass covers cause, but I believe that depends on the thickness of the Steel plate. My plan is to order various Ni-plated Steel spacers from here to stick on the pickup bottoms:

https://www.solomusicgear.com/product-category/pickup-parts/keeper-bars-spacers/

At 3mm, they are a bit thick for the purpose, but I think it's worth a try. I imagine one of the ~1/2" wide bars will stay magnetically stuck in between the pole screws, and I can experiment with double-side taping one of the thinner bars, or some galvanized Steel nails on the other sides of the pole screws so the flux lines from the strings draw down through each side of the coils, which might also draw much more flux away from the screw heads. It may not make much difference anyway since the pole screws are also Steel, but I think it's worth a try.

I'll be doing this over the next few weeks, and I'll record some b4 and after tests with all else being equal. I may just attach a tuning peg, bridge and pickup to some spare wood so the string to pickup distance doesn't change with the different amounts of Steel plates. I'll do a recording of each:

-without any plates.
-with just one plate on the center.
-with just plates on the outer edges.
-with plates all across.

Should be an intersting experiment. If there is a marked difference, I imagine I'll want less Steel plating for the neck pickup.

 

[audept]

Welcome to the forum, @GCKelloch ! I will be watching your experiment with interest!

 

[GCKelloch]

Thanks, audept. I didn't notice b4, but it looks like the BT's don't have a Steel keeper bar the pole screws would normally go through in many other pickups. The 4 screws coming up through the baseplate anchor to the plastic bobbins. The pole screws are held snug inside the bobbins, and the structure is held rigid by the baseplate sidewalls and cover. It may reduce parts and simplify assembly, but it also contributes to "ice pickiness".

There isn't already any extra Steel under the coils to draw flux lines from the strings, which may be another difference from the HS model. Adding Steel under the baseplate should indeed make a difference, including marginally lowering inductance. The net result should be stronger bass and a less strident note timbre like the HS model. Granted, the HS are prettier, but not 2x price prettier.

I forgot to mention that the two magnets Richochet used look slightly different widths. If so, the top magnet would be contributing even less to the flux at the pole screw heads. That got me thinking about whether I should go with the 13mm or 12.5mm wide Steel spacers under the baseplate. What I've determined is the 12.5mm would more likely ensure the pole screws are not forced away from the magnet edges, but I will want some Steel on the outer sides of the pole screws to pull string flux lines through the outer portions of the coils, and to pull the screws toward the magnetized Steel spacer for the most flux drain from the pole screw heads. However, all that Steel mass directly connected to the magnet might draw most of the flux into it, and I don't think I want that. It might be better to insulate the Steel from the pole screws with electrical tape, yet make sure the Steel is grounded to the Brass baseplate so it doesn't act as an antenna for hum. That's another configuration worth testing. Again, some DS tape might be needed to keep everything in place.

 

[GCKelloch]

I wonder if there is any difference in metal pole pieces between the Filtertron and Blacktop which relates to the sound.. I think someone told me that the pole screws on tv jones are different compared to the hs filters which relates to the overall sound though I find it hard to believe there would be a difference that would be discernible really.. anyone have experience with this?

Different core alloys can change the Q and efficiency of a pickup depending on the electrical conductivity and permeability. My understanding is that conductivity increases eddy currents that generally roll off highs, and permeability increases flux power and inductance.

 

[GCKelloch]

Got the Blacktops today, and ordered a bunch of Steel keepers and plates for $22 (with the $13 standard shipping).

This article by Dr. Scott Lawing shows how a Steel plate under the coils can increase pickup efficiency:

The Wide Range Humbucker and The Genius of Seth Lover — Lawing Musical Products

The Wide Range Humbucker was introduced in 1971 and originally discontinued in 1979. The Wide Range pickup was unique because of its threaded CuNiFe pole piece magnets, but as we’ll see, they aren’t the only key to the unusual design of this pickup.

lawingmusicalproducts.com

I don't expect much in that regard because the Blacktop pole screws are likely just high-permeance Steel that will draw in the flux lines from the strings more than the Steel under the Brass baseplate. It might do a little, and should at least reduce the flux from the magnet. We shall see.

 

[GCKelloch]

It turns out the two AlNiCo 4 bar magnets I have are a perfect fit for the Blacktops. I have to open one up to run a separate chassis ground wire for my phase reverse blend option anyway, so I'll replace the stock A5 bar with one of the A4 for at least the bridge pickup. Haven't ever done that. I assume my solder sucker device will be indispensable. A4 has ~4x the permeance of A5, and demo comparisons with such a magnet swap in PAF types definitely sound sweeter and warmer. I can also try Steel bars on the bottom at some point, but I'll first see if I can replace the internal plastic side spacers with the 5.2mm wide Steel keepers I ordered. They should fit snuggly in. That might also draw the string flux more into the outer coil sections. The neck pickup might be fine with the A5 magnet. I'd rather not open up the pickup, and a Steel bar under the middle may reduce string flux a bit without increasing output or reducing the Q. I can start on it after I build an upside down pickup bracket and remove the pickguard in my "Austriocaster", but I have to wait till I get the Steel bars from Canada next week to finish all the tests.

 

[GCKelloch]

So, I cut up an old food container as the pickup bracket, and compared the bridge Blacktop as is to with an AlNiCo IV bar stuck to the bottom between the pole screws. Yes, it can only be placed so the magnetic poles feed into each other, but there isn’t as much flux loss at the pole tops as I had assumed.

I plugged into my Motu M2 A/I unit (1M Ohm input) with a 235k R pot wired in parallel, and my low capacitance (160pF) guitar cable. The guitar bridge has thick Brass saddles on the top 3 strings and Stainless steel on the bottom 3. The strings are a 10-46 set tuned down to D. I plucked the top 3 strings on various frets up the neck with a sharp/rough-edged 2mm Ultex pick ~½” in front of where a middle Strat PUP would be, and then rendered the samples through a Fender twin-like S-Gear amp sim preset with combined ported Celestion G12-65 cab & closed-back JBL K120 4x12 cab IR’s.

Of course, each string pluck is a bit different. The A4 bar does have an overall more rounded treble character, which may be partially due to a lower Q A4 generally imparts, but I doubt that’s a significant factor compared to the effect the Steel pole screws have on the Q. The main difference is probably just how the weaker flux reduces string pull effects.

I prefer the A4 with the 235k R, even with the bright sounding Wenge neck and Stainless frets. The high end is down enough as is from the Steel pole screws and Brass covers. Both of the 175k R samples lack a full sounding chime to my ears. It should be nice with two 500k pots, and I'll add a small cap on a switch for a 4-4.5kHz resonance peak like a typical PAF. The peak is up around 6kHz now, which I had hoped for with my very low C cable. The neck Blacktop peak should be up around 8kHz, which has a nice airiness. That should be cool, along with my special blend/OoP wiring. I will also have a small cap value tone pot on the single PUP settings for a mild ~1.6kHz to a stronger ~2.2kHz peak as the knob is rolled down below 5. I’ve done that on several guitars.

Here are the bracket pic and clips:
https://drive.google.com/drive/folders/10AQld_ew6Du73DzQKL2LGMzizmz_RH-W?usp=sharing

 

[Ricochet]

A4 has ~4x the permeance of A5,

Interesting experiments. ^that^ can’t be correct though?

 

[GCKelloch]

Interesting experiments. ^that^ can’t be correct though?

I must admit I don't fully understand the technical side of magnetics, although I thought I understood permeance vs permeability. I have read that A4 permeance is higher than A2, and as much as 4x A5. Dr Scott Lawing has written the A2 he gets is ~2x the relative permeability of A5, and that A4 is only ~1.5x, more like A3. I may be misunderstanding something, but I had always thought the permeability of A3 was higher than A2. Perhaps I should ask him about that, and/or try some A2 magnets?

 

[Ricochet]

I must admit I don't fully understand the technical side of magnetics, although I thought I understood permeance. I have read that it's higher than A2, and as much as 4x A5. This page shows the permeance coefficient as lower than A2, but I'm not sure if that's the same as permeability or permeance. Dr Scott Lawing has stated the A2 and A3 he gets is ~2x the permeance (permeability?) ratio of A5. Perhaps I should ask him about that, and/or try some A2 magnets?

I know just enough to be dangerous, but it’s my understanding A4 is typically closer to A5. If A2 is -2x to A5, A4 would logically fall somewhere in between. Alnicos are only roughly defined and will vary between manufacturers, so who knows.