george
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Post by george on Jul 2, 2015 6:29:41 GMT -5
Hi John,
Thank you for the Excel file, I've been playing with it on and off yesterday and today, but I'm not sure about how it works. Have you made some kind of tutorial available on this calculator? Like a captured screen video on Youtube or a PDF manual? I'm just asking because if you have, I'd rather watch it or read that before bothering you with questions that you might have answered numerous times since you came out with this Excel calculator.
George
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Post by JohnH on Jul 2, 2015 6:55:24 GMT -5
Im glad it runs for you. All I've written about it is on the main thread: GuitarFreakI haven't written out any formal instructions beyond that, and the notes and comments hat are in the spreadsheet itself
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george
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Post by george on Jul 2, 2015 11:22:18 GMT -5
Hi John, I read that thread but couldn't find answer to a few questions: 1. how and where do you set the value of the bass pot R7? (right now based on it's name it seems like it is a 1Mohm pot, but I am not sure because the Treble pot doesn't have any numeric value following the word "treble".) 2. Which tone circuit should I pick for PTB tone circuit? 3. There is a radio button selector switch in the Treble section "Modern" and "50-ies" that swaps a treble tone pot with a volume pot. What is this for? a) if you have a Vintage strat, you should use the "50-ies" option because that's what you have in your strat, or b) You should wire your strat this way if you want it to produce a vintage sound? 4. What is the "Vin" circle is there for in the pickup section? 5. What does "buffer" means at the "Output" section? When do I pick that? I do use a 10' long high quality guitar cable, I guess, it differs from a plain vanilla 10' long coiled cable. Which one should choose or what C4 R6 values should I use? 6. If I do a snapshot, is it only an image, or there is a way to "go back" to the state when the snapshot was taken and go from there? For e.g. I did a snapshot at a possible best settings with my current knowledge (without knowing how to set many parameters) then I proceeded to find better curve, when I realized that I cannot produce better curve with my present knowledge I wished I made a screenshot of my computer screen with all the numeric values, so that I can reset it to those previous settings manually. For example it would be a cool option to double click on the blue snapshot curve and that would reset the settings to the values of the snapshot, to make it even extreme, you could do several snapshots in different colors and later you can go back to them and modify them if you want to. I know, I know, I'm asking for too much, no, my brain just shifted into my IT gear and that's all what happened. Anyhow, as you can see, I am not a seasoned electronic guy who is on the same page with you on all level when it comes to musical instrument electronics. Basically, my mind is set to setup a horizontal mid range curve with the bass cut off not too sharply at around 125Hz and the treble at around 2kHz and just wanted to check if it is feasible with my S1 switching Strat circuit. I know, that I could get a 10 band EQ like Caline CP-24 to get to the same result, but if I could manage to achieve the same result with a few caps and pots then I'd give it a shot. Since there is no way to simulate all possible settings of a deluxe strat circuit in this excel file since when you're using two pickups, there is an option on the strat with the S1 pushed in that one pickup has a special cap while the other does not. But I still want to know whether I could achive the above mentioned EQ range when the S1 switch is not pushed in. Cheers, George
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Post by JohnH on Jul 2, 2015 15:29:48 GMT -5
Great questions!, the best that have ever been asked about GuitarFreak so thankyou for those.
1. how and where do you set the value of the bass pot R7? (right now based on it's name it seems like it is a 1Mohm pot, but I am not sure because the Treble pot doesn't have any numeric value following the word "treble".)
In the current version, its fixed as a 1M linear pot. The scale is from 0 to 10, so 10 is actually zero ohms ie max bass. if you want to know how much cut a 250k pot will give, set the knob to 7.5
2. Which tone circuit should I pick for PTB tone circuit?
The bass cut part is built in, and the treble cut part can be the standard tone circuit, or, I think it would work very well with the no-load tone. But actually, you can try any them.
3. There is a radio button selector switch in the Treble section "Modern" and "50-ies" that swaps a treble tone pot with a volume pot. What is this for? a) if you have a Vintage strat, you should use the "50-ies" option because that's what you have in your strat, or b) You should wire your strat this way if you want it to produce a vintage sound? 50's wiring is popular mod on Les Pauls so its included here. It has never been a part of Strat design so I suggest not to use it, but try the buttons and you'll see what happens
4. What is the "Vin" circle is there for in the pickup section?
That represents the theoretical source of signal in the modelling of the circuit, its not a physical part of he real pickup except you could think of it as the 'generator' inside the coil
5. What does "buffer" means at the "Output" section? When do I pick that? I do use a 10' long high quality guitar cable, I guess, it differs from a plain vanilla 10' long coiled cable. Which one should choose or what C4 R6 values should I use?
If you want to cut out the tone effect of the cable, you can built a small preamp into the guitar, or into the cord or use a wireless system. This option represents that and you can see how it changes treble response. The only parameter that apples to the cable is the capacitance. The built in values are based on 35pF per foot (=0.035nF) plus 100pF for the amp input. I think that is a reasonable average value but if you have a good low capacitance cable you can type a lower value into the box.
6. If I do a snapshot, is it only an image, or there is a way to "go back" to the state when the snapshot was taken and go from there?
Sorry, its only an image of the trace as a record, with ability to make numerical comparisons to the live trace. It is not set up to record all the many settings that applied to it. Maybe keep two copies open if you want to work that way.
Since there is no way to simulate all possible settings of a deluxe strat circuit in this excel file since when you're using two pickups, there is an option on the strat with the S1 pushed in that one pickup has a special cap while the other does not. But I still want to know whether I could achive the above mentioned EQ range when the S1 switch is not pushed in.
You can set up the basic series and parallel combinations of pickups from a Deluxe by putting in the combined properties. I also have a working file that can separately model two pickups and have the bypass caps modelled, not released though - Ill explain why later.
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george
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Post by george on Jul 10, 2015 19:32:29 GMT -5
Hi John,
Sorry about not getting back sooner, this week was a hectic one for folks in Hungary, first the 4 day long heat wave (~39 Celsius degrees) then the tornado like storm that came out of nowhere.
Thanks for answering my questions so thoroughly, I played with the Excel file a few times this week and I just wasn't successful getting anything close to these EQ settings:
Gain ................... 0dB 31.25 Hz ............ -12dB 62.5 Hz .............. -12dB 125 Hz ............... 0dB 250 Hz ............... 0dB 500 Hz ............... 0dB 1 KHz ................ 0dB 2 KHz ................ 0dB 4 KHz ................ 0dB 8 KHz ................ -12dB 16 KHz .............. -12dB
Maybe I just want too much from it? Or these values aren't such that one would expect it from tone pots of a Strat?
Cheers, Geza
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Post by JohnH on Jul 10, 2015 21:23:12 GMT -5
Hi John, Sorry about not getting back sooner, this week was a hectic one for folks in Hungary, first the 4 day long heat wave (~39 Celsius degrees) then the tornado like storm that came out of nowhere. Thanks for answering my questions so thoroughly, I played with the Excel file a few times this week and I just wasn't successful getting anything close to these EQ settings: Gain ................... 0dB 31.25 Hz ............ -12dB 62.5 Hz .............. -12dB 125 Hz ............... 0dB 250 Hz ............... 0dB 500 Hz ............... 0dB 1 KHz ................ 0dB 2 KHz ................ 0dB 4 KHz ................ 0dB 8 KHz ................ -12dB 16 KHz .............. -12dB Maybe I just want too much from it? Or these values aren't such that one would expect it from tone pots of a Strat? Cheers, Geza Well done for trying. You must have extended the graphics a bit to see the extremes of that range! That sort of tone control definitely needs active electronics to pull it off. It's outside of what can be done passively due to the sharp roll off that you seek and the flat mid response. A couple of op-amp stages would do it quite easily.
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george
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Post by george on Jul 12, 2015 7:00:09 GMT -5
No, I didn't modify the chart screen, I was concentrating on the flat mid range with some symmetric roll off on both ends. Do you happen to have any similar op-amp circuit diagram handy without applying it to the current scenario just for me to see how complicated it looks or smells like? I can do simple stuff, but I know that there can be quite a big differences between simple and simple.
Cheers, Geza
P.s.: John, I noticed that I used my real name in my last reply "accidentally", the reason for me to prefer to use George on user forums because it's a common name and no one will try to make any association between me and the Egyptian city Giza. I like to keep things simple. To pronounce it correctly, say the first part of it like the "ga" part in the word "game".
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Post by Ro_S on Nov 2, 2015 16:56:09 GMT -5
I came across the Joe Gore article cited in the opening post of this thread, a few weeks ago.
I think the passive dual treble/bass tone controls arrangement seems excellent - especially so for humbucker guitars. So easy to do. It seems like a 'no brainer'. Why isn't it encountered/used more often? I have several wiring and guitar projects lined up and intend to implement this as often as I can.
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Post by simeondavidschaub99 on Jan 26, 2016 15:29:05 GMT -5
Hello, I'm new here. Great post! Would it be possible to use this with a P90 to make it sound more like a normal single coil? And what resistor and cap values would I use? Thanks!
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Post by newey on Jan 26, 2016 18:23:22 GMT -5
SDS99-
Hello and Welcome to G-Nutz2!
JohH, the author of this whole tone control section, is the one to provide an answer to your question about values. From his post yesterday, he is apparently traveling at present, and so he may be awhile before he checks back into The NutzHaus™. So, sit tight a bit . . .
As for the P90 sounding more like a SC, that's going to be a subjective thing. To the extent that a P90 generally sounds a bit "fuller" (a deliciously undefined term, you'll note) than a SC, and perhaps a bit "bassier", then perhaps a touch of bass cut would indeed mimic a SC. But the tonal differences between the two pickups probably run deeper than what can be accomplished via just a frequency cut.
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Post by simeondavidschaub99 on Jan 27, 2016 3:15:51 GMT -5
Hi newey, Thanks for your quick reply. I'm aware that this isn't going to sound exactly like a strat single coil would. I'm just wondering if you could get in the ballpark of a strat pickup. Thanks!
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Post by JohnH on Jan 27, 2016 11:55:00 GMT -5
Hi newey, Thanks for your quick reply. I'm aware that this isn't going to sound exactly like a strat single coil would. I'm just wondering if you could get in the ballpark of a strat pickup. Thanks! Hello Further up on this thread, I posted some speculative thoughts on this (IE some numbers suggest this could work, but not tested!) It seemed that a very small bass-cut cap like 470pF might do it. So, no guarantees but id suggest volume pot 250k, treble cut pot 250k no load (best, but 500k log if you cant do no load). Bass cut pot 1M. Try differnt bass cut capa too...if you do this..you are the pioneer, so please report back to base with your discoveries!
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Post by ChristoMephisto on Jun 16, 2016 17:04:46 GMT -5
Was thinking of upgrading the low cut switch I have in my Bass VI with a 1M bass cut pot. Actually it's on a dpdt center off switch that I want to connect to the bass cut pot and that way can shunt it when I want to turn it off, or have two different cap values. Altho not understanding why the volume pot has to be a maximum of 250k. My bass has a 1M volume pot at the moment. It's a CTS pot from '66 and has that 'vintage taper' and sounds great with it. How is that going to effect the operation of the bass cut pot with a 1M volume pot? How does the volume pot factor into the rc frequency equation?
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Post by JohnH on Jun 18, 2016 20:53:13 GMT -5
Was thinking of upgrading the low cut switch I have in my Bass VI with a 1M bass cut pot. Actually it's on a dpdt center off switch that I want to connect to the bass cut pot and that way can shunt it when I want to turn it off, or have two different cap values. Altho not understanding why the volume pot has to be a maximum of 250k. My bass has a 1M volume pot at the moment. It's a CTS pot from '66 and has that 'vintage taper' and sounds great with it. How is that going to effect the operation of the bass cut pot with a 1M volume pot? How does the volume pot factor into the rc frequency equation? You use a 1M volume pot, but with a 1M bass cut pot, the range of bass reduction would be less. Here is a rough comparison, worked out for a bass guitar: The red and dark blue lines show predicted response with 1M and 250k volume pots, with no bass cut. You can see how the red line with 1M volume gives you a bit more high end (no treble cut modelled). Turning down a 1M bass-cut pot, with a 0.0022uF bass cut cap, is shown in green and pale blue. There is less bass-cut available from red down to the green line with 1m volume, than there is from dark blue to light blue using a 250k volume. To get more out of the 1M volume with bass cut, maybe a 2M pot for bass-cut could be found (or make one using both sides of a 1M dual-ganged end to end), with a smaller bass-cut cap. A 2M bass-cut with a 0.001uF cap looks like it might give a couple of db more range.
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Post by ChristoMephisto on Jun 22, 2016 16:44:54 GMT -5
Thanks for the reply on this. I have an empty hole for a pot and exploring options instead of posting the usual 'tell me what to' thread.
So it may or may not work depending on the cap values I use. Might have to play around with it as I have a staight .0033 or a .0066 (2x.0033 caps) and like the sound with just a switch, no extra fiddling with knobs.
Even came up with away to add the pot to the switch to be able to turn it off by shunting it, and included a Free Woman Tone to work with it.
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Post by ChristoMephisto on Aug 18, 2016 16:40:23 GMT -5
So I worked in a 3M reverse audio pot to act as a bass cut that can be switched in or out. Also had two cap values to play with. It worked pretty well on by Bass VI, even had less volume loss compared to the straight cap. But found once I had a spot I liked the pot, I left it there, so may go back the the original sound without the pot. The pups seem to interact with just a series cap anyways.
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axedoctor
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Post by axedoctor on Feb 7, 2017 10:00:25 GMT -5
a related question : I am considering the idea of modifying a dual humbucker guitar with stock tone/volume/3-way to add coil cutting for both pickups and bass tone control my thought is to combine two of the controls using a concentric dual shaft pot and implement the third control plus the coil cutting feature with a DPDT push/pull pot the difficulty I am facing is obtaining parts to accomplish this while also ending up with at least a 2-to-1 ratio of the bass control pot to the volume pot to achieve a decent amount of bass cut effect one arrangement that I have been able to locate would result in a 250k push/pull for the volume control & coil cut switch along with a stacked 500k/500k for the treble & bass tone controls here is a view of the schematic as described : this would seem to be sufficient as long as the 250k volume control will be work okay with the humbuckers??? I tend to convince myself that it can be fine, given a treble bleed and the ability to "unmuddy" the humbucker with the new bass control. Also, a 250k volume might actually work better when the humbucker coils are cut than a 500k. what sayest thou???
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Post by JohnH on Feb 7, 2017 15:19:22 GMT -5
I think that is a sensible package.
The load on the humbuckers from using a 250k volume is not too bad, given that you also have 500k for the treble pot. You could go for 500k volume but then the bass cut wouldnt be so effective since it is the vol pot that loads the bass cut to make it work.
500k for bass cut pot leaves a bit of bass-cut range missing as compared to 1M for bass cut, but not much.
You can try different bass-cut caps to see which sound best at minimum. The nice thing about bass cut is that there is no penalty or tonal comprimise at max bass.
Presumably you will have to use linear or standard log for the tone pots? Theres a practical issue there. Both treble and bass cut will work much more smoothly with log pots than with linear. But when appropriately wired, max treble is at 10 and max bass is at 0. Can you get your head and fingers around that when they are both on the same shaft? You could think in terms that both will be 'brighter' at 10, ie max treble and min bass. Or, you can use linear pots so both bass and treble are max at 10 (reverse bass pot wires), but then the treble range will feel like it all happens from 0 to 2. Not a problem unless you think it is one.
Possible icing on the cake could be if you could make the treble pot no-load. Probably not possible on a dual pot but maybe consider further when you see the pot.
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axedoctor
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Post by axedoctor on Feb 7, 2017 17:00:43 GMT -5
good to hear from you, John
so, maybe I messed up my schematic ... the treble tone pot wiring intends to create maximum series resistance (minimum treble cut) at full CCW while the bass tone pot wiring intends to create minimum parallel resistance (minimum bass cut) at full CCW ... if this is so, then we rotate clockwise to engage the tone control function in each case, no???
thanks for explaining why you think 250k will function reasonably ... I had been thinking that the 500k treble tone pot sizing would be an advantage as well, but your confirmation encourages me that perhaps I am beginning to properly internalize some of the key aspects of this guitar circuitry stuff
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Post by JohnH on Feb 7, 2017 18:35:13 GMT -5
I hadnt reviewed the CW and CCW on tbe diagram. I was just talking about options. But usually max is clockwise, so your tones are max (ie no cut) CCW? Designers choice! But my point was to highlight issues of pot taper versus smoothness vs direction of turn.
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Post by reTrEaD on Feb 7, 2017 18:51:34 GMT -5
the treble tone pot wiring intends to create maximum series resistance (minimum treble cut) at full CCW This is the reverse of normal practice. A standard treble-cut tone control cuts most when the control counter-clockwise. If you want your treble control to work in the direction you described, you should use a reverse-log pot or at the very least, a linear. Else the control will be very slow at the CCW (no cut) end and be very abrupt at the CW (full cut) end. This works well with a standard log-taper pot. The taper suits the function.
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axedoctor
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Post by axedoctor on Feb 7, 2017 19:33:07 GMT -5
thanks for the feedback, reTrEaD so you are saying that the treble cut functions significantly better when changing resistance from 0% to 90% with 0-to-5 and then 90% to 100% with 5-to-10, rather than 0% to 10% from 0-to-5 and then 10% to 100% with 5-to-10? I can see there being a difference with a volume control voltage divider, but less so with a variable impedance shunt like the treble cut path. but perhaps this is why I am merely a resident MD
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Post by JohnH on Feb 7, 2017 19:51:04 GMT -5
On a mormal treble control, turning clockwise (looking from front) from 0 (max cut mun resistancw) to 10 (full treble max resistance), if it is a log pot, most of the changes happen 0 to 5 and a smaller but still useful amount 5 to 10. With a linear pot, the same is transferred to 0-2 and then 2 to 10, so less smooth.
The same is true with bass cut, but now min resistance is no cut and max reistance is max cut.
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Post by reTrEaD on Feb 8, 2017 12:46:22 GMT -5
I can see there being a difference with a volume control voltage divider, but less so with a variable impedance shunt like the treble cut path. Actually it's more so with the shunt than it would be if the pot functioned as a divider. The reason is: We still have a divider. But the top half (the internal resistance and inductance of the pickup) is fixed. It doesn't change as we rotate the pot. A small change in resistance is virtually meaningless at the high resistance end. But it can make a HUGE difference at the low resistance end. 240k to 250k means almost nothing. Zero ohms to ten thousand ohms is very significant. 10k is in the same order of magnitude as the internal impedance of the pickup. So we want very small changes in resistance in the early part of the rotation starting from zero resistance and very large changes in the later part of the rotation when we approach maximum. A standard log taper gives us that, if zero resistance is at the CCW end. A reverse log pot does the same if zero resistance is at the CW end. R.G.Keen wrote a useful article a few decades ago entitled "The Secret Life of Pots". I'm very keen on it. Pun intended. About halfway down the page there is a graph of the resistance vs rotation for linear, log, reverse log, and most importantly, the "straight line audio taper" which is the real-life substitute that we actually get when we think we're buying log taper. It does a reasonable job of approximating a log taper so I wouldn't lose any sleep over it. www.geofex.com/article_folders/potsecrets/potscret.htmHe includes a section which examines changing the taper of a pot with external resistors. The benefits and pitfalls. You might find that useful somewhere. Believe it or not, IF STUCK with two linear pots and two log pots and wanting to put together a LP configuration of two volumes, two tones, Bridge, Both in parallel, Neck scheme, I'd probably use the linears on the volume controls and the logs on the tones.
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Post by sumgai on Feb 8, 2017 16:51:32 GMT -5
Believe it or not, IF STUCK with two linear pots and two log pots and wanting to put together a LP configuration of two volumes, two tones, Bridge, Both in parallel, Neck scheme, I'd probably use the linears on the volume controls and the logs on the tones. I believe that this configuration is what Gibson used on most of their early guitars, excepting that they specified 300Kohm pots instead of the more standard 250K units. It seems to me that with linear controls, a more-quickly responding blend would be achieved, and for stage use, this might be desirable. For ultra-fiddley settings (i.e. players with extreme anal proclivities), I could see substituting log pots into the volume control position - better resolution, at the expense of speed and ease of use. But then again, I'm not a Gibson (ab)user, so whaddoe I know. sumgai
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Post by reTrEaD on Feb 8, 2017 18:23:58 GMT -5
That's a big part of it. A linear pot is poorly suited as a volume control. Even more so as a tone control in the treble-cut shunt scheme. So in a single volume and tone configuration, you make a choice. A proper acting volume control and touchy tone control, or better control of the tone and a volume control that does little as you roll back from maximum an has most of the change shoved toward the CCW end of the rotation. I'm not a big fan of treble-cut tone controls anyway, so I personally might opt for the former in the one volume, one tone configuration and one pot of each flavor. But with two volume controls (and a parallel configuration), blending tips the balance in the opposite direction. It might be helpful to look at the parallel arrangement in two parts. What the Bridge pickup contributes and what the Neck pickup contributes, given the loading each pickup sees. When both pickups are selected and both volume controls are at maximum, the signal created by the Neck pickup has the Neck pickup's internal impedance in series with it. And it has the Bridge pickup's internal impedance shunting that to ground. As well as both volume control elements. But those are still quite large compared to the internal impedances. Flip the script for the signal from the Bridge pickup. So each pickup has a modest loss compared to being used alone. And their contributions are relatively equal. Now, let's leave the Bridge control at maximum and rotate the Neck control counter-clockwise by just ten degrees. With a 300k linear pot that represents 30k in series with the Neck pickup and 270k shunt to ground. The decrease from 300k to 270k does represent a very slight increase in load that the Bridge pickup will see. But that's dramatically offset by the effect offered by adding 30k in series with the Neck pickup. Instead of having the 10k-ish impedance of the Neck pickup loading the Bridge pickup, that part of the load just got a LOT lighter. That part is now more like 40k. So the Bridge pickup breathes a little easier and contributes more now, than it did with both volumes at maximum. Meanwhile, the additional series resistance in the Neck circuit coupled with roughly the same shunt (which is mostly dominated by the 10k-ish load of the Bridge pickup, results in a very noticeable reduction of the contribution from the Neck pickup. Whereas previously, the parallel combination resulted in the signal from the Neck being reduced to approximately half voltage, we now see a reduction to something like 20%. The net change is something like a reduction to 40% of it's previous contribution (in terms of voltage). So we'll estimate the Neck's contribution to be something like -8dB, using the full parallel as a reference. This is slightly quick but certainly manageable. Now let's look at what a 10% rotation does with log pots. With the "straight line audio taper" 10% rotation from fully CW gives us a ratio of roughly 35:65 So with a 300k pot, that would be something like 100k in series with the neck, 200k for the shunt. Our Bridge pickup breathes a little more easily than the previous example. It's getting a lot closer to the voltage it would produce if selected as Neck-only. And the contribution from the Neck pickup is more seriously removed. I'd estimate it's reduced to something on the order of something like -15dB compared to what it contributed when both volumes were at max. And since the Bridge pickup has a greater contribution, we're looking at something approaching -20dB when we compare the Neck pickup contribution to the Bridge pickup contribution. That's really quick. Our Neck pickup is playing a very small role in this blend and we've only rotated 10% from maximum. It's too abrupt to satisfy most people. So it's a very reasonable tradeoff to get a slower and manageable action when attempting to blend, at the cost of having a volume control that has its action pushed somewhat toward the CCW end when one pickup is selected by itself. FWIW, a "real" log taper is even worse for blending. We're at a 50:50 ratio at 10% rotation from max.
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Post by sumgai on Feb 8, 2017 19:13:34 GMT -5
'TrEaD,
Your articulations are spot-on, as usual. I could only wish that I could think, and type, nearly so eloquently and quickly - it probably took you about a third of the time it would've taken me. Kind of why I'm so gung-ho on the KISS thing, doncha know.
sumgai
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Post by Ro_S on Mar 17, 2018 20:46:30 GMT -5
Reverend brand guitars often have a "bass contour" control. How does that differ to the bass cut in G&L style passive PTB circuit, or is it exactly the same?
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Post by sumgai on Mar 17, 2018 20:53:20 GMT -5
Ro_S, Without looking at any diagrams, I can say first that in the audio world, the descriptor "contour" means a compensated control of some sort. IOW, it's not a simple shelving structure, it actually changes the curvature over a specified frequency range, as the shaft is rotated. Now, does that means anything to us guitarists? No, not at all. So, I'll have to dig up a Reverend schematic or two. Please stand by..... And I'm back! OK, I have to report that all of the diagrams I saw were simple shelving types, just like we've been discussing these past few weeks. For whatever reason they call 'reasonable', they use a 500K pot (taper un-specified) with a 0.0022 mfd cap. I personally can't see that as very wide-range of control, but that's their business, not mine. And to put paid to the account, on their very own website they call it a Bass Contour ' that cuts Bass frequencies' so as to give you 'different pickup voicings'. Marketing hype, to be sure, but then again, they've been around for what, 20 years, maybe longer. I'm certainly not gonna say that they're doing it wrong.... just different. sumgai
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pj
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Post by pj on Mar 18, 2018 4:18:47 GMT -5
I've played around with this idea a bit and though I really like it I've run into a couple of interconnected issues.
Depending on choice of values, and how severe your bass cut is, the reduction in load caused by turning down the volume (thereby reducing the effect of the parallel loading of the input impedance of your amp or first pedal) can cause some defeating of the the bass cut. I was running 2n2 and 500k with some pearly gates and found that turning down (I'm a volume rider) would cause the lows to return. At gigging volume the combination of this and the increase in output impedance lowering the low pass point with the cable capacitance, made for a significant shift in tone.
So this led me to try putting the bass cut on the output node rather than before the volume pot (hagstrom did this with the swede I believe although the bass cut was preset caps on a switch). This was far better in terms of being consistent as the guitar is turned down but... (on to my second issue which is the other side of the coin from the first really)
As a fanatic of vintage effects with wildly different input impedances I started to get driven mad by the frequency of the low cut moving around depending on what I was running into. I eventually built a buffer with the facility to let me adjust the output impedance so I could present a constant load to the guitar and not load down input biased bjt effects with the usual low impedance buffer output. Some pedals liked it some just didn't play, but it was certainly better than having the situation where I'd be on full bass cut strumming and singing (amps high input impedance reasonable cut), then hit my lpb2 for a solo (much lower input impedance hence the shelf jumping right up high) and find that I was slicing through the wallpaper and sending the audience running.
This probably says more about my mental state than the practicality of the ptb. I just thought I'd throw down these elements so that others could mess with them if they fancied.
All the best
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