Multi-capacitor tone control

[Angel LaHash]

Originally Posted by ricobasso

I love all this enthusiasm. Don't forget to always use the same guitar lead for any comparisons. Different leads have different capacitance.

With the guitar Volume control at max and the Tone at minimum resistance, any guitar lead capacitance is directly in parallel with your tone control capacitor. If your guitar cord has a capacitance of 1000pF, don't expect to hear any difference when switching between a 47pF and a 100pF! Both will be swamped by the cord.

A cable is Just copper, and there for just a Resistor
3m Cable 1.1Ohms Earth side
1.7Ohms Tip side

just put a Cap meter on the same cable and its giving me -7uF and -9uF on the same setting on the Earth

45uH on the Earth and 48uF on the Tip

[Stealth]

Originally Posted by bumperbass

Please enlighten me, but if you use flatwounds on a P-bass, how come you can't get an authentic Jamerson tone from an EQ, or maybe a variable mid-scoop control (called a contour control on some new heads).

The sound of the tone control rolled down is the sound of a flattened resonant peak, a frequency spike that happens when an electronic circuit is tuned just so that the frequencies right before the cut-off point (that is, before it begins to cut highs) are boosted, sometimes massively (especially with high-value pots such as 1M). Rolling down the tone brings down the resonant peak, sometimes enough that there's no more resonant peak to speak of, and instead the frequencies all just start getting dampened the higher you go. To get that you'd have to get your EQ to be centered exactly on the resonant peak and it'd have to be just wide enough to dampen the peak and its surroundings, which is a tough thing as no two basses are alike. The scoop/contour control goes even further because it takes away some of the mids (which are usually lower than the resonant peak), more than you'd normally roll down with a tone pot.

Originally Posted by Angel LaHash

A cable is Just copper, and there for just a Resistor
3m Cable 1.1Ohms Earth side
1.7Ohms Tip side

just put a Cap meter on the same cable and its giving me -7uF and -9uF on the same setting on the Earth

45uH on the Earth and 48uF on the Tip

A cable is a copper wire insulated with rubber tubing around which is a copper shield, which is again surrounded by rubber. It's basically a long, flexible cylindrical capacitor with the sandwiched rubber layer acting as a dielectric. It behaves as an RC circuit (the length of the cable giving it the resistance and the coaxial structure providing for the distributed capacitance). So unless it's being driven by an active circuit (a preamp), yes, a long cable might negate enough highs to even defeat the tone control.

[bumperbass]

Originally Posted by Stealth

A cable is a copper wire insulated with rubber tubing around which is a copper shield, which is again surrounded by rubber. It's basically a long, flexible cylindrical capacitor with the sandwiched rubber layer acting as a dielectric. It behaves as an RC circuit (the length of the cable giving it the resistance and the coaxial structure providing for the distributed capacitance). So unless it's being driven by an active circuit (a preamp), yes, a long cable might negate enough highs to even defeat the tone control.

^ ^ ^
This guy knows what he's talking about. Well put, Obviously, you have some electronics training/experience.

[kurosawa]

Originally Posted by bumperbass

I love it, too (the enthusiasm, that is). Never have I used the tone control. Mine's always on 10, with a 500K pot. Maybe it's me, but I figure a tone control is -- 10 = normal, less than 10 = take clarity away.
I understand wanting to get an authentic old school rolled off tone, though. IMO, a tone control isn't the way to do it. I am not bashing you guys. I always use EQ settings to get my tone. Please enlighten me, but if you use flatwounds on a P-bass, how come you can't get an authentic Jamerson tone from an EQ, or maybe a variable mid-scoop control (called a contour control on some new heads).
I used to use the parametric EQ on an old Peavey Mark IV I had (and still have). You could dial in exactly where you wanted the scoop and how much of a scoop or boost you desired. Sorry to say, this circuit isn't in most new amps. Maybe it's because it's too much to mess with nowadays.
Like I said, I read all the posts and enjoyed them, because I'm a tinkerer, too, but to all of you guys that use tone controls, please enlighten me. Maybe I'm missing something.

Jamerson kept his tone knob dimed, too. And if it's the recorded tone you mean, he recorded direct. From what I'm reading, maybe all you need is a '62 AVRI, LaBella 760M, and a REDDI.

[bumperbass]

Oh well. I don't hear any resonant peak that you describe being there, at least I don't think that peak is some gigantic spike. Either way, I guess to each his own.
Thanks for the explanation, though.
Kind of reminds me of a bassist I knew way back in the Kustom tuck and roll days, who would turn his treble all the way down, bass all the way up, and his tone turned down a bit.
All he provided was this rumbling sound and he could hit any note he wanted, and nobody knew the difference. In this way, he never made an audible mistake.
In my situation, I need all the bite I can get with suitable low end, because I'm in a rock trio that plays a variety of stuff and we'd sound too empty if all I added was thump. In a multi-guitared band with a keyboard and maybe horns, I could get away with a jamerson tone more, but not now.

[khutch]

Originally Posted by Angel LaHash

just put a Cap meter on the same cable and its giving me -7uF and -9uF on the same setting on the Earth

45uH on the Earth and 48uF on the Tip

Those meter readings are no where near correct so your meter is unsuited to this job, or perhaps you are using it incorrectly. For a 3m cable I would expect a few hundred pF at most and maybe a few tens of nH. The capacitance and inductance of an instrument cable are as real as the resistance. An instrument cable is a cheesy kind of transmission line. The capacitance is far more important than the inductance or resistance to a passive bass. None of it matters much with an active bass, the output impedance is too low to be bothered by these values.

Ken

[khutch]

Originally Posted by bumperbass

I understand wanting to get an authentic old school rolled off tone, though. IMO, a tone control isn't the way to do it. ...
Like I said, I read all the posts and enjoyed them, because I'm a tinkerer, too, but to all of you guys that use tone controls, please enlighten me. Maybe I'm missing something.

The old school rolled off tone came from a typical passive bass tone control so that is the perfect way to get it. The simple EQ controls on many amps have a defined limit on the boost and cut. A passive tone control rolls off indefinitely so an amplifier EQ control is not going to give you exactly the same result as a passive tone control. Plus at some settings of the tone control you get a boost in the frequencies just before the roll off which a simple EQ will not give you.

A switched cap or "tonestyler" control gives you a boost at every setting. The frequency of the boost and cutoff varies with the cap setting. So it is a bit different from a traditional passive tone control. I recently got a Fender Reggie Hamilton Standard Jazz Bass which has a passive/active switch. However the Standard, unlike the custom shop version, does not have a passive tone control. I'm about to put a switched cap tone control into mine just to have an on bass tone control. I really could not find a dual pot with the right element values to build a traditional tone control on the same shaft as the midband EQ control so I decided to use a 2P12T switch to give me both the midband "pot" and a switched cap tone control.

You can do a lot of things with the EQ settings on your amp. In fact the three band EQ on my active basses is no better or worse than the simple EQs on a lot of amps and it will give you a very wide range of tonal choices. But a lot of people covet the "passive sound" and I don't think you can really get that in all its glory without a passive tone control, unless the only tone you like is the dimed setting. So I think it will be a welcome addition to my Reggie Hamilton.

Ken

[Stealth]

Originally Posted by khutch

You can do a lot of things with the EQ settings on your amp. In fact the three band EQ on my active basses is no better or worse than the simple EQs on a lot of amps and it will give you a very wide range of tonal choices. But a lot of people covet the "passive sound" and I don't think you can really get that in all its glory without a passive tone control, unless the only tone you like is the dimed setting. So I think it will be a welcome addition to my Reggie Hamilton.

Indeed, the passive sound is an animal of its own species.

The active EQs on basses usually work as either shelvers (boosting or cutting above or below a certain frequency) or peaks (boosting or cutting around a certain point) or a combination. Rare few try to emulate a more flexible variant of the passive tone control (such as the Alembic SVF, or its clone, the cAMPus). Those that do basically act as an infinitely variable Tonestyler, as if you had a variable capacitor hooked up to a regular tone control, so you can pick both where the peak and cutoff are (what changing the capacitor would do) and how high the peak is (what turning the tone knob would do).

[Angel LaHash]

So i cant get my head around a Cable being a CAP
Cap is Two plates every side with a Liquid inbetween
and what dose -0.7uF mean.. i didnt know it could go in to - figures

NOW, as for the Electicals, I was a Electronics Tech for 3 at two compairs
2 Years as a Design and 1 as a bod
I stuided Electronics for 3 years at college, mainly Mathmatics
SO IF YOU THINK I DONT UNDERSTAND ELECTRONICS Please do tell me so i can add up the sums for myself.. yes i found one of the comments a bit upsetting and a bit of a put down, im not sure if it was just aimed at me (dyslexia can make you feel that way after so many years) Ive done DC on Electronics, AC on electical installtions. But ive got a currect form that is well Random

[Stealth]

Originally Posted by bumperbass

Oh well. I don't hear any resonant peak that you describe being there, at least I don't think that peak is some gigantic spike. Either way, I guess to each his own.

Oh, it exists, and it brings what's commonly called clarity or brilliance of the bass sound. If you have a passive bass you don't mind tinkering with for an afternoon, here's an experiment. Change the volume pot with its normal value (250K or 500K) for one with a much lower (for instance, a 50K). When you solder it back and turn up the volume, you'll hear the sound has become very dull and lifeless. Feel free to change it back for the original pot immediately, unless you dig that sound.

I didn't mean to offend, directly or indirectly. You've asked over PM for a clarification, but I'll post the similarities between a capacitor and a cable here. Below is an image of a cross-section of a multi-layered electrolytic capacitor that has layers of metallic foils and insulator material, so it's basically like a flat capacitor was rolled into a tube or cylinder.



Then there are photos of a guitar cable being unraveled. Before the cable is cut up, you can see going from the center out that there's a metallic signal wire, an insulating layer, then the metallic ground wire wrapped out like a cylinder around that, and the another insulating layer. Again, layers of metal-insulator-metal-insulator, just like a cylindrical capacitor.

[bumperbass]

Originally Posted by khutch

A switched cap or "tonestyler" control gives you a boost at every setting. The frequency of the boost and cutoff varies with the cap setting. So it is a bit different from a traditional passive tone control. I recently got a Fender Reggie Hamilton Standard Jazz Bass which has a passive/active switch. However the Standard, unlike the custom shop version, does not have a passive tone control. I'm about to put a switched cap tone control into mine just to have an on bass tone control. I really could not find a dual pot with the right element values to build a traditional tone control on the same shaft as the midband EQ control so I decided to use a 2P12T switch to give me both the midband "pot" and a switched cap tone control.


Ken

There is no such thing as 'boost' on a passive circuit. The only way to produce a boost a certain frequency or frequency band is to cut all others out.

As far as a peak, hogwash. The tone control rolls off the highs at a certain point, which is determined by the value of the pot, the cap, and the reactance of the pickup. This is a rolloff from a certain frequency. A rolloff. The only way you're going to tame a peak is to use a passband filter, consisting of a cap and an inductor, much like a midrange crossover.

[Stealth]

There's always some amount of boosting, thus the name resonant peak, implying there are certain frequencies that get amplified by the resonating circuit.

As far as the peak being hogwash, I point to this as my source of info about the peak. In a circuit with known pickups, the peak (and thus cutoff) frequency is changed by the Tonestyler (or any cap-swap), while the resonant peak height is altered by the setting of the tone control - to be more exact, the resistance that gets left parallel to the output (picture 14 on Lemme's page).

[khutch]

Originally Posted by bumperbass

There is no such thing as 'boost' on a passive circuit. The only way to produce a boost a certain frequency or frequency band is to cut all others out.

You can in fact boost with a passive circuit. You get maximum power transfer from a "generator" to a "load" when the load matches the internal impedance of the generator. A magnetic bass guitar pickup (our generator) has a very different internal impedance than the 1 MOhm input impedance of a typical amplifier (our load) so the power transfer from pickup to amp is severely crippled. This leaves the door open to boosting both the output voltage and the power transfer using completely passive components. The boost that you get from a tone capacitor is a result of the capacitor and the pickup inductance forming an impedance matching circuit over a narrow range of frequencies. With the switched cap tone circuit the wide range of capacitance values available allows you to put the boost at a wide range of frequencies. This is a well known effect that any circuit simulator will demonstrate. Of course there is a steep roll off at frequencies right above the peak of the boost but this is not a fundamental limitation, just a result of the details of this ad hoc matching circuit.

It is in fact possible to provide a much better impedance match at every frequency the bass is capable of producing by using a transformer. None of this violates any circuit analysis laws or the laws of thermodynamics. The reason is that we are not transferring more power to the amp than the pickup is generating, which is impossible, we are just turning a very inefficient power transfer mechanism into a much more efficient one. The difference between this kind of passive output boosting and an active booster is that the active booster can provide more output power than the pickup is generating, as your 300 W stage amp so vividly demonstrates. It does that by drawing the extra power from a nuclear power plant located conveniently nearby.

Ken

[khutch]

Originally Posted by Angel LaHash

So i cant get my head around a Cable being a CAP
Cap is Two plates every side with a Liquid inbetween
and what dose -0.7uF mean.. i didnt know it could go in to - figures

What you are describing is an electrolytic capacitor but there are many kinds of capacitors. A very great many capacitors use a solid material (plastic, ceramic, etc) as the dielectric between the plates. The "breadslicer" capacitors you find in the tuners of older radios and TV sets used a gas (air) as the dielectric between the plates. The capacitors used in high power radio transmitters use nothing (a vacuum) as the dielectric between the plates because a vacuum cannot break down and arc over at high voltages and power levels.

The concept of a "plate" is also unnecessary in a discussion of capacitance. Any two conductors located anywhere in the universe will have some capacitance between them. You increase the capacitance considerably by moving the conductors as close together as the applied voltage differential allows. You increase the capacitance considerably again by flattening the conductors into thin metal plates with a large area facing each other. You increase the capacitance considerably a third time by putting a high dielectric constant material into the volume between the two plates. But none of this is a requirement to produce a capacitor. A typical coaxial, shielded audio cable has a native capacitance between the inner conductor and the shield. The cables we use are fairly small in diameter so the two conductors are fairly close together. The space between them is filled with a plastic insulating material that has a higher dielectric constant than air. So even though the two conductors are not in the optimum facing plate configuration, the other two factors are present and generate a fair amount of capacitance per foot, or meter.

Oh, as I mentioned before the capacitance reading you are getting from your meter is bogus. You are doing something wrong, or the meter is not capable of reading cable capacitance for some reason, but the reading is bogus so ignore it. A 3 m cable will not have anything even close to a micro Farad of capacitance and the capacitance it does have will be positive, not negative. If you want to know what the capacitance of your cable is your best bet is to try to find the pF/foot or pF/meter specification for the wire it uses or a similar wire. If you can, this information may not be published unfortunately.

Ken

[bumperbass]

Originally Posted by Stealth

There's always some amount of boosting, thus the name resonant peak, implying there are certain frequencies that get amplified by the resonating circuit.

As far as the peak being hogwash, I point to this as my source of info about the peak. In a circuit with known pickups, the peak (and thus cutoff) frequency is changed by the Tonestyler (or any cap-swap), while the resonant peak height is altered by the setting of the tone control - to be more exact, the resistance that gets left parallel to the output (picture 14 on Lemme's page).

Good stuff, Stealth. Healthy dialog, too. First, I know a typical pickup (any pickup, really) never has had a flat frequency response. I don't think a P-bass pickup has any 12 dB peak, but I can't say for sure, because I haven't measured it.
Amplifiers from the beginning of time have designed their tone controls (think the typical tone controls that Leo used in most of his designs, which were taken from the RCA tube handbook) to correlate to the pickup's design.
I still say there's no BOOST in a pickup. True, the resonant peak is a boosted part of it's frequency response. I read the article from your link and if you keep the variables that most tech's know about, such as cable capacitance and pickup loading, you're getting what the pickup puts out. When you change the cap value in a tone pot, you're changing the location of the peak. You're not boosting it.
Furthermore, as stated in the article, this resonant peak can be anywhere from 2,000 to 5,000 Hz in a guitar pickup. There's not much of this range coming out of a typical setup in a bass. Those using a single 15" speaker will rarely have the opportunity to hear much (if any) above 2,000 Hz anyway, and back in the day, 99% of all bass players were using 15's. Those playing through 10's? Maybe 2,000 to 3,000 Hz. Again I'm not exactly sure but that's close.
People who play Strats and Teles (especially Teles) LOVE this peak.
You make some valid points and it's been fun. HOGWASH might have sounded rather rude as I re-read my post. Don't want to be your enemy. I was meaning NAH! Not, "you're crazy and stupid".
I haven't studied the preamp response curves in typical bass amps so I cannot say how they deal with this peak, but I imagine most circuits take it into consideration in their designs. Just because a pickup has a 12 dB peak at 4,000 Hz does not mean it's going to be a 12 dB peak at the power amp output to the speakers.
So, having said all this, yes, I think the cap variation isn't such a bad idea overall. I guess my problem is, I LIKE HIGH END and I always do the taming and shaping at my amp.
Thanks for the excellent link. I enjoyed it very much.

[bumperbass]

Originally Posted by Stealth

There's always some amount of boosting, thus the name resonant peak, implying there are certain frequencies that get amplified by the resonating circuit.

As far as the peak being hogwash, I point to this as my source of info about the peak. In a circuit with known pickups, the peak (and thus cutoff) frequency is changed by the Tonestyler (or any cap-swap), while the resonant peak height is altered by the setting of the tone control - to be more exact, the resistance that gets left parallel to the output (picture 14 on Lemme's page).

Good stuff, Stealth. Healthy dialog, too. First, I know a typical pickup (any pickup, really) never has had a flat frequency response. I don't think a P-bass pickup has any 12 dB peak, but I can't say for sure, because I haven't measured it.
Amplifiers from the beginning of time have designed their tone controls (think the typical tone controls that Leo used in most of his designs, which were taken from the RCA tube handbook) to correlate to the pickup's design.
I still say there's no BOOST in a pickup. True, the resonant peak is a boosted part of it's frequency response. I read the article from your link and if you keep the variables that most tech's know about, such as cable capacitance and pickup loading, you're getting what the pickup puts out. When you change the cap value in a tone pot, you're changing the location of the peak. You're not boosting it.
Furthermore, as stated in the article, this resonant peak can be anywhere from 2,000 to 5,000 Hz in a guitar pickup. There's not much of this range coming out of a typical setup in a bass. Those using a single 15" speaker will rarely have the opportunity to hear much (if any) above 2,000 Hz anyway, and back in the day, 99% of all bass players were using 15's. Those playing through 10's? Maybe 2,000 to 3,000 Hz. Again I'm not exactly sure but that's close.
People who play Strats and Teles (especially Teles) LOVE this peak.
You make some valid points and it's been fun. HOGWASH might have sounded rather rude as I re-read my post. Don't want to be your enemy. I was meaning NAH! Not, "you're crazy and stupid".
I haven't studied the preamp response curves in typical bass amps so I cannot say how they deal with this peak, but I imagine most circuits take it into consideration in their designs. Just because a pickup has a 12 dB peak at 4,000 Hz does not mean it's going to be a 12 dB peak at the power amp output to the speakers.
So, having said all this, yes, I think the cap variation isn't such a bad idea overall. I guess my problem is, I LIKE HIGH END and I always do the taming and shaping at my amp.
Thanks for the excellent link. I enjoyed it very much.

[Stealth]

Originally Posted by bumperbass

You make some valid points and it's been fun. HOGWASH might have sounded rather rude as I re-read my post. Don't want to be your enemy. I was meaning NAH! Not, "you're crazy and stupid".

No need to fret. I know this dialog's all in good fun and for sharing the knowledge. I know my eyes also popped wide open when I first read that article.

Originally Posted by bumperbass

I haven't studied the preamp response curves in typical bass amps so I cannot say how they deal with this peak, but I imagine most circuits take it into consideration in their designs. Just because a pickup has a 12 dB peak at 4,000 Hz does not mean it's going to be a 12 dB peak at the power amp output to the speakers.

The preamps don't deal with the resonant peak specifically - they apply their own curve upon that signal which may lower it or boost it further (making the bass sound shriller, for instance), so you may end up with a different peak at the power amp output. And if there's anything nonlinear in there (and there will be) you might get even more peaks than you started with.

Anyway - back on the topic of the multi-cap tone control. One of the cooler things about the Tonestyler-type controls is that you don't necessarily have to use capacitors in all switch positions. You can drop a diode into one of the branches, or two diodes in anti-parallel (facing opposite sides), or combine those with capacitors.

[Southway]

I found a slightly cheaper source for the on-on-on type of switch used by the OP (tax and shipping charges may negate the difference on small orders).

http://www.newark.com/jsp/search/pro...og&sku=95M4609
This in a Multicomp brand and may be slightly different than the OP's switch, but it operates the same according to the datasheet.

[Bassamatic]

Here's the switch wiring I used - a little different than the OPs. Works great! The values I used were different than the diagram.

[Angel LaHash]

i had to use a On-Off-On, 100-50p a unit and they were asking like £4 (400p) for a on-on-on
the On-Off-On 1P2T mm wont give the SAME effect totaly as it will be 3 Caps
On-Off-On (End & Middle summed together, Middle, Other End & Middle summed together)

-----------------------

Cable Cap, i should of remembed this. Im also doing electical Installions and was warned what would happen just having Live cables only all going one way makes a magnetic field (my spelling is getting worse) so would more of a SPRING like Cable be better, Like Hanging up Curtins (Net in front of the window) normaly (in the uk) has a Metal Ribb Effect, what i would guess that it going around its self would MAKE a LOT more resistance but Lower the Capacitance.

-------

So far ive added 100nF, 47nF, 22nF, 12nF, 3n9nF and a 1nF, with a 470pF to come
means i got 4 more spaces on this switch ..

-------

I got a lot of reading to do on this web page so will take me a while to read it all (not that great of a reader)