Hi,
I'm looking for a clean booster circuit with eq, to built it inside a guitar. It should work with two pots: a) Gain, unity gain when it's set fully ccw. b) a tone control that's completely neutral in middle position, going into a treble&bass boost on one side and a mid boost on the other. Does this already exist?
Maybe a variation of a baxandall or James tonestack, with a stereopot instead of separate treble and bass pots?
IMHO, you're looking for too many features in relation with control pots availiable..
A stereo pot can be wired to simultaneously cut/boost bass and treble for 2 band EQ but you'll need another pot for the 3rd band..
edit: On a second thought, by cutting bass AND treble you actually "boost" mids.. :icon_wink:
Quote from: roseblood11 on June 19, 2022, 02:21:38 PM
Hi,
I'm looking for a clean booster circuit with eq, to built it inside a guitar. It should work with two pots: a) Gain, unity gain when it's set fully ccw. b) a tone control that's completely neutral in middle position, going into a treble&bass boost on one side and a mid boost on the other. Does this already exist?
Maybe a variation of a baxandall or James tonestack, with a stereopot instead of separate treble and bass pots?
There are plenty of designs of mid-boost / mid-cut circuit that are totally flat in the centre position. Ok, mid-cut isn't *exactly* the same as treble&bass boost, but if you turn the volume up, it is!
A Baxandall mid circuit would be one option, or you could look at gyrator mid controls. THere's a ton of stuff (probably) more than you need) looking at different options on my page about the Hard Bargain pedal:
https://electricdruid.net/designing-the-hard-bargain-distortion-pedal/ (https://electricdruid.net/designing-the-hard-bargain-distortion-pedal/)
In the end, I went with the Baxandall design, as you can see here - you could nab the "Mid Boost/Scoop control" section pretty much as-is:
(https://electricdruid.net/wp-content/uploads/2019/01/HardBargain5SchematicPg2.jpg) (https://electricdruid.net/wp-content/uploads/2019/01/HardBargain5SchematicPg2.jpg)
The gain stage from unity gain to more gain is a simple non-inverting op-amp application. There's one of those on the front of the Hard Bargain too, acting as a buffer-with-gain.
HTH,
Tom
Cutting bass and treble is the same as boosting mids, that's how a baxandall works... The Boss FA-1 uses 50k linear pots for bass and treble, it would be quite easy to replace both with a dual ganged pot. But it might require some adjustments, and maybe a better circuit already exists?
The Blade VSC preamp is more complex, but with a similar approach: a mini switch for t&b / off / mid boost, with three internal trim pots for the gain of each band. But that way, you only get two presets, none of them being completely linear.
Thanx Tom, that's exactly what I was looking for.👍
Tom.. :icon_smile:
Hard Bargain implements 3 (three) pots where OP calls for a single one.. :icon_wink:
(OK.. IC3.1 may be wired as booster, but still we have a surplus pot..)
Quote from: antonis on June 19, 2022, 02:47:18 PM
Tom.. :icon_smile:
Hard Bargain implements 3 (three) pots where OP calls for a single one.. :icon_wink:
(OK.. IC3.1 may be wired as booster, but still we have a surplus pot..)
What I meant was that:
The Mid Boost/Cut circuit does all the tone control elements the OP wanted - that's one pot. Then they need some gain too, so add a non-inverting op-amp with gain control - that's another pot.
There, that's just two pots, right? :)
Here is something, simpler, exactly one knob, morphing from boost at extremes to boost in the middle.
(https://i.postimg.cc/G8DMvcSS/roseblood11-a-42.gif) (https://postimg.cc/G8DMvcSS)
I fear it highlights the physical difficulty: blending from a / slope to a \ slope mean large phase shift, cancellation, unexpected curve.
But it would not cost a buck to try.
It will sure need a buffer/boost in front because a passive pickup can't drive the EQ impedances. Some of the makeup gain could be moved before the EQ. Some very clever Tee networks in NFB loops might drop the opamp count to two, but I can't bust my brain over a 9-cent part for a one-off. We have not discussed DC power and bias so that is left to the builder. Also the unity-to-boost goal which is trivial (might give an excuse for a fourth opamp).
(https://i.postimg.cc/9rd5xZ6v/20226K03.png) (https://postimg.cc/9rd5xZ6v)
It's very difficult to fully satisfy the required specifications.
(https://i.postimg.cc/SXKBN5nh/20226K04.png) (https://postimg.cc/SXKBN5nh)
(https://i.postimg.cc/pyjgTKLp/20226K06.png) (https://postimg.cc/pyjgTKLp)("Flat" position is 1 o'clock)
The Baxandall Mid control has such a low Q at low boost/cut, it almost acts like a volume control in most of the middle of pot's travel,
Only developing some decent Q towards extreme of pot travel.
Quote from: m4268588 on June 20, 2022, 02:47:07 AM
(https://i.postimg.cc/9rd5xZ6v/20226K03.png) (https://postimg.cc/9rd5xZ6v)
It's very difficult to fully satisfy the required specifications.
(https://i.postimg.cc/SXKBN5nh/20226K04.png) (https://postimg.cc/SXKBN5nh)
(https://i.postimg.cc/pyjgTKLp/20226K06.png) (https://postimg.cc/pyjgTKLp)("Flat" position is 1 o'clock)
Please tell me more about this kind of tone circuit. What is its name ?
What are the extra components trying to achieve ? Increase the Q ?
Where can I read more about it ?
Thanks
Quote from: Vivek on June 20, 2022, 05:04:31 AM
The Baxandall Mid control has such a low Q at low boost/cut, it almost acts like a volume control in most of the middle of pot's travel,
Only developing some decent Q towards extreme of pot travel.
My hard bargain page starts off with a Constant-Q Mid design, if that's important. For my purposes, I decided it wasn't and used the much simpler Baxandall Mid. But the OP might feel differently.
The trouble with the constant-Q design I used was that it uses three op-amps to do the cut/boost part, plus one more for the bandpass filter. That's not too bad if you're doing a whole EQ (just add one more filter per-band) but for a single band, it's a pretty big overhead. The design came from here:
https://sound-au.com/project75.htm (https://sound-au.com/project75.htm)
Tom,
Are Gyrator mids any better than Baxandall Mids in terms of higher Q ? Like the MT-2 Mid that you had analysed.
What is the best mid control with regards to high Q ?
Thanks
Quote from: Vivek on June 20, 2022, 06:21:27 AM
Tom,
Are Gyrator mids any better than Baxandall Mids in terms of higher Q ? Like the MT-2 Mid that you had analysed.
What is the best mid control with regards to high Q ?
Thanks
Yes, you can get a much higher Q with a gyrator. The trouble with the gyrator mid control is that it doesn't really do anything until the extremes of the pot range. It was partly because of this that I went with the Baxandall in the end, plus I wasn't convinced that a high Q was what I needed. High Q's often give you that "peaky" co
cked-wah sound, which is ok if that's what you're after, but it's pretty much just one sound.
For higher Q's checkout the musicman circuit
https://www.diystompboxes.com/smfforum/index.php?topic=128906.msg1243513#msg1243513
In order to choose a particular Q and amount of boost-cut you will need to change the part values.
It's not a straight forward process unless you churn through the equations.
What Tom said:
BAX MIDs
(https://i.imgur.com/8ATRF1P.jpg)
(https://i.imgur.com/PHAG4fD.jpg)
GYRATOR MIDs Q pot (RES2)
(https://i.imgur.com/FaWEayP.jpg)
(https://i.imgur.com/u1eOYIh.jpg)
Quote from: Vivek on June 20, 2022, 05:21:31 AM
Quote from: m4268588 on June 20, 2022, 02:47:07 AM
(https://i.postimg.cc/9rd5xZ6v/20226K03.png) (https://postimg.cc/9rd5xZ6v)
It's very difficult to fully satisfy the required specifications.
(https://i.postimg.cc/SXKBN5nh/20226K04.png) (https://postimg.cc/SXKBN5nh)
(https://i.postimg.cc/pyjgTKLp/20226K06.png) (https://postimg.cc/pyjgTKLp)("Flat" position is 1 o'clock)
Please tell me more about this kind of tone circuit. What is its name ?
What are the extra components trying to achieve ? Increase the Q ?
Where can I read more about it ?
Thanks
I don't know the name. I came up with the analogy from "BAX." And "tilt" control.
Removing R25, 26 and C26 does not provide a flat position.
Dear Antonis,
Could you please also post sweep of tone controls a noon, 25%, 50%, 75% and full, in both directions.
For Bax or Gyrator..??
Quote from: Vivek on June 20, 2022, 08:34:30 AM
Dear Antonis,
Could you please also post sweep of tone controls a noon, 25%, 50%, 75% and full, in both directions.
Here's the gyrator, every 1/10th of the control's travel:
(https://electricdruid.net/wp-content/uploads/2018/11/TiltAndGyratorResponse.jpg) (https://electricdruid.net/wp-content/uploads/2018/11/TiltAndGyratorResponse.jpg)
As you can see, it only really does anything between 0-20% and 80-100%. The middle 60% is pretty subtle. The Bax gives a more even response around the knob travel.
.
"Here's the gyrator, every 1/10th of the control's travel: As you can see, it only really does anything between 0-20% and 80-100%. The middle 60% is pretty subtle. "
Would a W-taper pot, like on Boss and old DOD pedals, work more evenly? I ask in general, not just to the topic project.
Quote from: Kennt82 on June 20, 2022, 09:51:38 AM
"Here's the gyrator, every 1/10th of the control's travel: As you can see, it only really does anything between 0-20% and 80-100%. The middle 60% is pretty subtle. "
Would a W-taper pot, like on Boss and old DOD pedals, work more evenly? I ask in general, not just to the topic project.
Yes it would. That is exactly the reason why they are used in these situations. It is also worth noting that the uneven pot response problem scales with total range. Meaning, if you only want to do ±9 db, it's not great but mostly fine. At ±15db it is already quite annoying. To me, ±12 db seems to be the absolute maximum range where gyrator EQs with linear pots are usable. Above that, W (or G or S) type are a must above that.
IMHO, +/- 12dB should be the upper/lower limit of anything system balancing..
(if more is needed, system is essentially inadequate and needs redesign..)
QuoteIMHO, +/- 12dB should be the upper/lower limit of anything system balancing..
(if more is needed, system is essentially inadequate and needs redesign..)
What's often not realized with first-order equalizers is more dB can only be achieved by stretching the span of frequencies. You either shift starting point or the ending point to make the hill higher. There's no point going from 12dB to 18db if the difference is a boost 6dB between 10Hz and 20Hz.
This one moves the upper frequency of the bass (more or less) to get more boost but then it starts affecting the mids.
(https://1.bp.blogspot.com/-ksA4b3-OuJM/UoL4X7nwCSI/AAAAAAAAF8U/xdHh0PZFu5s/s400/Figure+10+Top,+Frequency+Response+of+Circuit+as+Shown.+Bottom,.jpg)
If you get 12dB boost from *two* 6dB boosts the slope is faster and the range of affected frequencies is more narrow.
(https://i.postimg.cc/FfnP2Mnf/20226L00.png) (https://postimg.cc/FfnP2Mnf)
But, this may increase noise.
You sometimes can get away with linear pots on gyrator circuits if you make the value of the pot 4 times (or less) the value of the feedback resistor. (For the TS-9 values of pot = 20k and feedback R as 1k the ratio is 20:1 and you really need a G taper pot to prevent the control cramping at the ends.)
When compared to a larger pot value, the smaller pot value does affect the response to some degree. You may need to tweak the gyrator values a bit to make the response similar to what it was before. It depends what amount of boost you want to match them at as well.
Quote from: antonis on June 20, 2022, 05:07:54 PM
IMHO, +/- 12dB should be the upper/lower limit of anything system balancing..
(if more is needed, system is essentially inadequate and needs redesign..)
+1
Quote from: antonis on June 20, 2022, 05:07:54 PM
IMHO, +/- 12dB should be the upper/lower limit of anything system balancing..
(if more is needed, system is essentially inadequate and needs redesign..)
While this might be true for "system balancing" like in a hi-fi system where the original point of tone controls was supposed to be to help correct for room responses (lots of heavy curtains? Turn up the treble a touch) I don't think this is true for "tone shaping" applications at all. We're not trying to balance some existing response - we're creating one. For that job, we can make it as extreme as we like - although going crazy rarely leads to fantastic results in my experience.
This is fairly true for guitar pedals, although in that situation we do have some other tonal responses to consider (the guitar itself, the amp) but they are highly variable and unknown to the designer, so it's basically impossible to "design them in". Where it's even more true is for synth designs where you're creating sound from scratch and there's no previously-existing tonal response at all until you put it in.
So...depends what you're doing and why, I'd say.
Quote from: ElectricDruid on June 21, 2022, 08:40:21 AM
We're not trying to balance some existing response - we're creating one.
So it is if you think so.. :icon_wink:
Quote from: ElectricDruid on June 21, 2022, 08:40:21 AM
Quote from: antonis on June 20, 2022, 05:07:54 PM
IMHO, +/- 12dB should be the upper/lower limit of anything system balancing..
(if more is needed, system is essentially inadequate and needs redesign..)
While this might be true for "system balancing" like in a hi-fi system where the original point of tone controls was supposed to be to help correct for room responses (lots of heavy curtains? Turn up the treble a touch) I don't think this is true for "tone shaping" applications at all. We're not trying to balance some existing response - we're creating one. For that job, we can make it as extreme as we like - although going crazy rarely leads to fantastic results in my experience.
This is fairly true for guitar pedals, although in that situation we do have some other tonal responses to consider (the guitar itself, the amp) but they are highly variable and unknown to the designer, so it's basically impossible to "design them in". Where it's even more true is for synth designs where you're creating sound from scratch and there's no previously-existing tonal response at all until you put it in.
So...depends what you're doing and why, I'd say.
+1 to that, too! However, I find that beyond 12db, controls with a standard pot get too coarse for most tone shaping applications. It's really more "tone remodeling" at that point. Also useful but a different application in my mind. If I want something more drastic than 12 db boost/cut, I like to add a 3-way switch to add or subtract another 24db. Total ±36 db with quite fine grained control should cover a lot of use cases.
Quote from: Fancy Lime on June 21, 2022, 01:04:37 PM
I find that beyond 12db, controls with a standard pot get too coarse for most tone shaping applications. It's really more "tone remodeling" at that point.
That's partially what I was meaning.. :icon_wink:
But Tom took it into heart, viewing my comment as personal debasement regarding Hard Bargain.. :icon_mrgreen:
Quote from: antonis on June 21, 2022, 02:40:47 PM
Quote from: Fancy Lime on June 21, 2022, 01:04:37 PM
I find that beyond 12db, controls with a standard pot get too coarse for most tone shaping applications. It's really more "tone remodeling" at that point.
That's partially what I was meaning.. :icon_wink:
But Tom took it into heart, viewing my comment as personal debasement regarding Hard Bargain.. :icon_mrgreen:
Awww, no, Antonis, it's not personal and I didn't take it as such!
I think we basically all agree here, but perhaps we each have our own personal terminology?!? I like "Tone shaping becomes tone remodelling" though - very descriptive.
Quote from: ElectricDruid on June 21, 2022, 02:54:13 PM
I think we basically all agree here,
Unfortunately, Yes..!! :icon_mrgreen:
(no room for a meaty spat..) :icon_mad:
Quote from: antonis on June 21, 2022, 03:12:26 PM
(no room for a meaty spat..) :icon_mad:
LOL!! We should try harder!!
Quote from: ElectricDruid on June 21, 2022, 06:17:17 PM
Quote from: antonis on June 21, 2022, 03:12:26 PM
(no room for a meaty spat..) :icon_mad:
LOL!! We should try harder!!
NEVER! ONLY WIMPS TRY HARDER!!!! AND COMMUNISTS!!!!!!!1!!!1!!¹11!!
Damn, I'm not good at this. Who would've thought that it could be this hard to start a senseless shouting match on the internet ;)
on the topic of tone shaping with filters, i was doing some mid control experimentation a month ago, and came up with this circuit:
(https://i.postimg.cc/jW5ys4vN/not-a-chainsaw-filter.jpg) (https://postimg.cc/jW5ys4vN)
it boosts and cuts midrange inspired by the classic Swedish Chainsaw tone, but my own interpretation/weird version. i designed it and tinkered with it to have a perceived constant volume, while drastically changing the midrange character, this balancing of the perceived volume resulted in two different depths, and how 'fast' they react to the increased rotation of the pot (the boost lowers quicker than the cut). it cuts 16dB around 400-ish Hz, and boosts 27dB around 1100-ish Hz, but their overlapping bands make it less extreme as it may seem. best results with a anti-log pot, or a log pot in reverse.
its part of a very minimal-ish-t chainsaw inspired distortion.
Quote from: Fancy Lime on June 21, 2022, 01:04:37 PM
I find that beyond 12db, controls with a standard pot get too coarse for most tone shaping applications. It's really more "tone remodeling" at that point.
i agree with this very much. this is one of the few ''common'' applications of a boost/cut way above 12dB. i would generally keep any band boosting under 6dB and any band stop under 9dB for most ''conventional'' sounding pedals.
cheers
edit: wrong image
Quote from: iainpunk on June 22, 2022, 07:57:36 AM
on the topic of tone shaping with filters, i was doing some mid control experimentation a month ago, and came up with this circuit:
(https://i.postimg.cc/6y5QnvhM/not-a-chainsaw-filter.jpg) (https://postimg.cc/6y5QnvhM)
I presume it's designed for dual symmetrical supply, Iain.. :icon_wink:
Nevertheless, it should still need a bias resistor (path to GND), which should interact with 4.7 nF cap..
it was designed to tack onto a drive circuit without a coupling cap. its just a snippet of a circuit, a way to convey a basic idea without muddying it with the bias, coupling and power supply situation. kind of like how they do it in my textbooks from school, nice and uncluttered.
i'd think people would know by now that most of the time i put ideas out like that. :icon_wink:
cheers
Quote from: iainpunk on June 22, 2022, 08:24:01 AM
i'd think people would know by now that most of the time i put ideas out like that. :icon_wink:
People would also know by know that you leave the all the dirty job to them.. :icon_wink:
Quote from: antonis on June 22, 2022, 08:38:44 AM
Quote from: iainpunk on June 22, 2022, 08:24:01 AM
i'd think people would know by now that most of the time i put ideas out like that. :icon_wink:
People would also know by know that you leave the all the dirty job to them.. :icon_wink:
''''dirty jobs'''' meaning the Ctrl-C and Ctrl-V functions? its not like its different in many cases.
here is the ''dirty'' version... still no biassing, as its based around a half wave rectifier for more distortion with less gain. uses single supply. the opamp is LM358 for operation near 0v and its crossover distortion adds to the sound.
(https://i.postimg.cc/9wGQQxLF/straight-razor-distortion.jpg) (https://postimg.cc/9wGQQxLF)
cheers
edit: Aron should add a symbol / marker so that moderators can mark a thread as 'de-railed'/'solved'/etc...
Quote from: iainpunk on June 22, 2022, 03:51:37 PM
here is the ''dirty'' version... still no biassing,
But now it IS biased..!! :icon_smile:
(via diode - 22k - 22k ..)
P.S.
Iain, I
think you have to present integraded circuits..
(not all forum members are able to readily implement a "main idea" circuit into a working effect..)
BTW, you could obtain half wave rectification without amp_1 out diode..
(just maintain GND bias and single supply..) :icon_wink:
Quote from: antonis on June 22, 2022, 04:12:43 PM
Quote from: iainpunk on June 22, 2022, 03:51:37 PM
here is the ''dirty'' version... still no biassing,
But now it IS biased..!! :icon_smile:
(via diode - 22k - 22k ..)
is it considered bias if its at 0v?
Quote
P.S.
Iain, I think you have to present integraded circuits..
(not all forum members are able to readily implement a "main idea" circuit into a working effect..)
fair point
Quote
BTW, you could obtain half wave rectification without amp_1 out diode..
(just maintain GND bias and single supply..) :icon_wink:
i found it wouldn't really cut at the middle of the wave, when guitar volume dialed back it would even clean up... its the input bias current, generating a voltage over the 100k input grounding resistor, setting the bias just a smidge above 0v, letting through part of the bottom wave. the diode reduces the 'loss' of the rectifier
cheers
Quote from: iainpunk on June 22, 2022, 05:01:02 PM
is it considered bias if its at 0v?
Only when 0V means Ground.. :icon_wink:
BTW, you can maintain de-railed depiction but, at least, connect 100k bias resistor at some Vref point..
(and, if you do so, place a cap in series with 1k gain resistor)
precision rectifiers NEED their feedback loop DC coupled to the same bias as the signal, otherwise they will charge up a capacitor and cut out or do other unorderly things you don't want it to.
cheers
Absolutely true & correct..!!
But for DUAL supply and signal INVERTING input.. :icon_wink: