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Re: Filtertrons Anyone?

2/24/2004 4:32 AM
Bill Raymond
Re: Filtertrons Anyone?
I recently obtained a couple NOS filtertron coils from, who took over Duke Kramer's business. I think he has a few left. If anyone's interested, I'll measure them and post the dimensions of the bobbin. Also found a chart of the wire gauges/number of turns for several varieties of filtertrons, which I'll look up and post the URL of the source. Filtertrons were originally ca. 4k, but sometime in the '80s (I think) they were wound to about 8k with thinner wire. I know Chet had his bridge pickup rewound by Shot Jackson to about 7.8k, according to longtime accompanist Paul Yandell, who knows more about Chet's equipment than perhaps Chet did.
2/24/2004 5:03 AM

Yep that sounds right I mostly wind them to 4k, but I have wound a set all the way up to 12k !!! was a bitch did it w/ 45awg wire.  
2/25/2004 1:31 AM
Bill Raymond

There is a chart of specifications for several of the current filtertron models at: downloads/GretschPICKUPSinfo.xls  
I measured the pickup bobbins to be:  
flanges are 7/16" wide x 2 15/32" long  
core is 1/4" high x 3/16" wide x 2 3/16" long  
overall height of the bobbin is just shy of 3/8"  
I didn't get out a micrometer or caliper, just used a scale, and since these are wound bobbins, I had to estimate the size of the core, but the bobbin material is sufficiently translucent that these measurements should be pretty close.
2/25/2004 6:09 PM
Fred Hammon

There seems to be a lot of difference in the wire gauges and DC resistance that are being used here.  
How is it affecting the sound? Aren't they supposed to be very bright sounding pickups? I was wondering how the #45 wire was sounding compared to the #42. I assume that allowances are made in the # of winds.
2/27/2004 3:01 AM
Dave Stephens
2/28/2004 12:48 AM
Bill Raymond

I tried it, and you're right. However, I can get there from a Google search for "filtertron spec", and the URL seems to be the same as I wrote it (I actually cut-and-pasted it from the site). Perhaps I got an extra space or something in there. At any rate, if you do a Google search, it'll get you there, and you can view the chart in HTML, or download the Excel spreadsheet. Sorry about that. If anyone has trouble accessing it, I'd be glad to email him/her the spreadsheet as an attachment.
2/29/2004 2:50 PM

Very interesting stuff, Bill and Curtis. So, these were wound to a total of 4k DC at some point?  
Thanks for all the info.

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