clara
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Post by clara on Mar 25, 2021 23:52:31 GMT -5
I havent found much information on the Kent Armstrong Tone Choke - So I thought I'd share what I've found: Specs and Dimensions: single wound 1.5 henries Basically this a tightly wound spool of fine wire like a pickup without a pole piece. Dimensions = 57/64 in. (23mm) X 47/64 in. (19mm) Wire lead length = 1 11/64 in. (30mm) 3.5 k dc resistance The choke coil can be wired in series with an appropriate value of capacitor to implement a mid-scoop (Wire Tone cap to Armstrong to ground). See picture for mid scoop when the coil is wired in series with a typical 22nF tone capacitor. Can be used to get a clean scooped sound out of the neck or bridge pickup. Also tends to make humbuckers sound more like single coils. The only problem with this wiring is that is does reduce the volume/output and scoops most of the best frequecies. I was looking for something to take the muddiness out of neck pickups (which IMO dislike along with typical tone control - too dull IMO). So I made and modeled a "Bass Filter" that seems to do the trick. Ra and Rb are meant to represent a typical tone pot - mine is 250K. The pot will range from no effect (pass thru) to the bass cut shown below. This seems to cut some lower bass and should take away some muddiness without a big volume drop - according to modeling in LTSpice
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Post by frets on Mar 26, 2021 11:41:04 GMT -5
Hi Clara!!😸😸, What you need is a Mouser Xicon 42TL021 4K Ohms 1.5 Henry Audio Signal Transformer (choke). There has been a lot written about these transformers on the forum. Just search on the term “Varitone.” Also search on “Rothstein” and “Midrange”. Here is a link to the transformer (choke). It’s dimensions are .591 of an inch by .433. Not too big. www.mouser.com/ProductDetail/Xicon/42TL021-RC?qs=%252BLh6ltJumVT3Qy3R%2Fg2Kgg%3D%3D
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Post by antigua on Mar 26, 2021 15:42:55 GMT -5
I havent found much information on the Kent Armstrong Tone Choke - So I thought I'd share what I've found: Specs and Dimensions: single wound 1.5 henries Basically this a tightly wound spool of fine wire like a pickup without a pole piece. Dimensions = 57/64 in. (23mm) X 47/64 in. (19mm) Wire lead length = 1 11/64 in. (30mm) 3.5 k dc resistance The choke coil can be wired in series with an appropriate value of capacitor to implement a mid-scoop (Wire Tone cap to Armstrong to ground). See picture for mid scoop when the coil is wired in series with a typical 22nF tone capacitor. Can be used to get a clean scooped sound out of the neck or bridge pickup. Also tends to make humbuckers sound more like single coils. ... Thanks for sharing this info. If you weren't liking the frequencies it scooped out, a cap value other than 22nF would move it to another frequency. I can't remember which cap value I liked the best, but my preference was different for the neck and the bridge pickup. For a bass roll off, I've much preferred series caps instead of parallel inductors. You might find a series cap value, maybe 22nF, which produces a cut off frequency that takes bass away from the neck pickup, but leaves the sound of the bridge pickup unchanged. That works a little better than putting a cap in series with the neck pickup alone, because it changes the phase of that one pickup but not the others, so when you combine it with the other pickups in series or parallel, they don't have that same "in phase" sound, which I think most would agree is a lot more pleasant than the out of phase tones. The Kent Armstrong inductor might possibly be intended as a replica of the "choke" used in a 1.5H Gibson Veritone. The secondary of the Mouser 42TL021 is 4k ohms, the inductance is 1.8 henries, so these two are very similar, performance wise, but one is a dedicated inductor at the other has a repurposed transformer, so they might not work exactly the same, there might be some unwanted parasitics with the 42TL021. The Bill Lawrence Q Filter guitarnuts2.proboards.com/thread/8288/bill-lawrence-filter-analysis is a bit different, it has an inductance of over 2 henries, though has a ceramic pot core, and a much lower DC resistance, 50 ohms, form maybe a hundred turns of wire, which goes to show how much more inductance you can get with a pot core. I made some Q filters of my own, they're about $3 a piece in parts. Since thicker wire can be used and they only require a hundred turns, they're fairly easy to assemble by hand. The much lower DC resistance doesn't seem to make much difference LTSPice modelling, but I think the lower resistance / pure inductance is all around more ideal. The Q filter is $30, the Kent Armstrong is $15, and a 42TL021 is about $3, so I'd say the price is ranked by quality, but the returns diminish greatly by price. I had the impression that I liked the Q Filter inductor better than the 42TL021, but I've never compared them side by side, and I should. Another thing I wonder about is whether the 4k ohm inductors produce more noise in the circuit than the 50 ohm Q filter.
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clara
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Post by clara on Mar 30, 2021 16:05:30 GMT -5
I see the impedance but the then Henry rating - are Henries usually calculated at 1 kHz? Use the primary side - 4kOhms impedance? Thanks
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clara
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Post by clara on Mar 30, 2021 16:14:54 GMT -5
I've been more interested in a tigher (higher Q?) notch filter to center around 300Hz - this seems to get the frequency cut I like to cut some mud out of a neck pickup. Ive had better luck modeling in GuitarFreak with the 3H Wilde-Lawrence Q-Filter. Also considering a Framus filter - seems to look promising. Anyone wire a Framus filter on a guitar?
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Post by antigua on Mar 30, 2021 23:51:36 GMT -5
I see the impedance but the then Henry rating - are Henries usually calculated at 1 kHz? Use the primary side - 4kOhms impedance? Thanks The different impedance of the two inductors is something that confuses me. With the Xicon 42TL021, the LCR meter shows the inductance climbing with frequency, but I don't assume it is, I assume it's a calculation error due to loading factors, unwanted parasitics, but the Bill Lawrence Q Filter reads about 2 henries at 100Hz or 1kHz, it's a lot more stable, and appears to have much less parasitic loads. That's also apparent in the plot I made in the other thread comparing them, where it can be seen that the Q Filter produces a very high Q factor in tandem with the pickup, while the Xicon 42TL021 does exactly the opposite. I don't know why the Xicon 42TL021 performs so much worse, but clearly it does, in both the bode plot and with the LCR meter. I guess he didn't call it the Q Filter for nothing. If you want a deep mid scoop, the Bill Lawrence Q filter definitely seems like the way to go. This is the mid scoop wiring diagram for the Q Filter: The value of the cap sets the frequency where the "scoop" occurs, 22nF puts the scoop around 1kHz. To get it down to 300Hz, it looks like you would need 300nF or a 0.3uF cap. The value of the resistor determines the depth of the scoop, lower resistance produce a milder effect, and no resistor at all produces the deepest possible valley. I used a trim pot to get an ideal tone, and I think I ended up settling on 10k.
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Post by blademaster2 on Mar 31, 2021 8:35:07 GMT -5
I've been more interested in a tigher (higher Q?) notch filter to center around 300Hz - this seems to get the frequency cut I like to cut some mud out of a neck pickup. Ive had better luck modeling in GuitarFreak with the 3H Wilde-Lawrence Q-Filter. Also considering a Framus filter - seems to look promising. Anyone wire a Framus filter on a guitar? I have a Framus Nashville, which has a 800mH inductor in the tone circuit (air-core bobbin with what appears to be pickup wire windings). It cuts the mids while leaving the clarity of the signal. I like it and replicated something like it on my own guitars, although it does not sound like the typical thick 'jazz guitar' tone that other tone circuits give me so I only use it on one of the two pickups (bridge).
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faydit
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Post by faydit on Feb 14, 2022 15:33:24 GMT -5
The Framus mid control is - theoretically - a good idea, if you want to get a mid scoop, but f you use it eg. with 1.5nF capacitors instead or the original 1nF, you will get about -6dB less bass (from 330 Hz to 0 Hz) and - 17 dB less (low) mids at about 330Hz, but due to the Q factor this scoop will even affect frequencies up to about 4000Hz which means you will lose a lot of signal strenght too. Also scooping at about 300 Hz will thin out the tone, but hardly will remove the neck (humbucker) pickup typical too intense, too loose, too muddy bass. On the other hand you could change the intensity by using different resistor values so that the filter works more decent: www.guitarscience.net/tsc/framus.htm#RIN=1k&R1=100k&RM=1M&RL=1M&C1=1n&C2=1n&RM_pot=LinearI personally rather recommended a bass cut, as G&L or Reverend use it. I‘d only use different values, a 500kOhm potentiometer instead of a 1Meg and not 2,2 to 4,7nF, but rather a value between 6 and 10nF, as the lower values also cut already a lot of mids too. With eg. 250 kOhm and a 6,8nF capacitor you get a cutoff frequency of about 100Hz, with 500kOhm about 50Hz, with 100kOhm about 265Hz, with 50kOhm about 530Hz. So a fixed, parallel resistor/capacitor combination with a resistor value between 200 and 300kOhm will also do a good job. You get even better results if you wire it like a treble bleed on a volume potentiometer, which means, not only a capacitor between lug 1 and 2, but also make a ground connection to lug 3. blackstoneappliances.com/BassKnob/Simple, but effective. __ I've also made some experiences with the Q-filters. In general not a bad idea, with the right resistor and capacitor values it can sound nice, the reason, why I soon removed the circuit again, was, that it works noticeably more intense with higher output pickups (which Mr. Lawrence also describes), which unfortunately means, if you eg. have a 7,3 kOhm neck pickup and a 14 kOhm bridge pickup and use the Q-filter, it will work much more intense at the bridge pickup, while it - in comparison - affects the tone of the neck pickup much less, so as a result the q-filtered neck pickup will sound fuller bodied and also much louder than the q-filtered bridge pickup, which will sound comparably thin and quietly then, which is - for me personally - not really a desired result. In my opinion a q-filter therefore only makes sense, if both pickups have the same (or very similar) values, in a guitar with a single pickup or if you have the option to install separate q-filters, in the best case also with different resistor and capacitor values, for each pickup. Of course, as any other passive filter, also a Q-filter unavoidably reduces output level.
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