Hi All,
Here's something I've been playing with. I've been thinking for a while that when you're adjusting the response of a dirt pedal, you're generally trying to do one of four things:
1) Smoother - more bass, less treble
2) More cutting - more treble, less bass
3) Mid boost to cut through the mix more
4) Mid cut for that classic scooped tone
Now, 1+2 and 3+4 are mirror images of each other, so this should be possible with two knobs. And it is, but I haven't got a *simple* way to do it. The circuit's a beast!
This is the response:
https://electricdruid.net/wp-content/uploads/2018/09/TiltMidCutBoostResponse.png (https://electricdruid.net/wp-content/uploads/2018/09/TiltMidCutBoostResponse.png)
(https://electricdruid.net/wp-content/uploads/2018/09/TiltMidCutBoostResponse.png)
This is the circuit
https://electricdruid.net/wp-content/uploads/2018/09/TiltMidCutBoostSchematic.png (https://electricdruid.net/wp-content/uploads/2018/09/TiltMidCutBoostSchematic.png)
(https://electricdruid.net/wp-content/uploads/2018/09/TiltMidCutBoostSchematic.png)
R15/R17 and R3/R4 are just a way of simulating a 100K linear pot - those are the two controls.
I shall have a go at building a distortion with this in it. Four knobs: Drive, Tone Tilt, Mid boost/scoop, Level. We'll have to see how it sounds...
Hope you like it!
Tom
BTW, I'd be very interested to hear if anyone can see any simplifications for that circuit.
It feels to me like the inverting gain stage (R14 10K / R2 39K) followed by the inverting bandpass MFB filter could be combined, since you can redesign the filter to include the gain, but then it finishes up inverting overall, and I haven't worked out how to get around that yet.
Thanks!
Page 6, Figure 9, that would simplify it quite a bit http://leachlegacy.ece.gatech.edu/ece4435/f02/equalizer.pdf
It would, it's true. It's not quite the same though - I was going for a Constant-Q equaliser, rather than the standard one.
Still, I should give it a whirl in the Sim and see what it look like. Might be close enough.
Thanks Scruffie.
It's true it's not perfect but I recall the Q is pretty steady compared to some popular EQ types and it's flat at the centre position, a little imperfection to save 3 Op Amps ain't bad ;)
I have used the tilt combination with it in the past (I've been searching for the combo you're after for a long time) and while it's a pain to tweak, it was a nice combo, better than a straight big muff control any day of the week.
Another variant I've always thought would be useful was a tilt EQ with a boost/flat/scoop mids toggle but I've not thought of an elegant way to achieve it yet.
Another way to make mid control is by combining fixed mid cut/boost from bandaxall into big muff style mixing thingy, might save some parts. Or, perhaps even easier would be to simply take notch/peak filter from basic 3 band active eq with fixed bass/treble. Mid controls are surely fun to play with. I like to experiment with tone controls myself, sometimes i spend hours just tinkering. ;D
AMZ Presence Control works great for me. (Just change the values to get the mid cut/boost frequency and amplitude you desire.)
http://www.muzique.com/lab/tone3.htm (http://www.muzique.com/lab/tone3.htm)
Ok, I've rejigged this using a baxandall type mid cut/boost instead. It's not quite as peaky as the original version, but that may be a good thing, who knows. I also tried a gyrator based design (thinking that I could get variable resonance to experiment with like that) but the trouble with the gyrator is that all the action is at the ends of the pot. It needs a pot with a X^2 response!
https://electricdruid.net/wp-content/uploads/2018/09/TiltAndBaxMidPlot.png (https://electricdruid.net/wp-content/uploads/2018/09/TiltAndBaxMidPlot.png)
(https://electricdruid.net/wp-content/uploads/2018/09/TiltAndBaxMidPlot.png)
https://electricdruid.net/wp-content/uploads/2018/09/TiltAndBaxMidSchematic.png (https://electricdruid.net/wp-content/uploads/2018/09/TiltAndBaxMidSchematic.png)
(https://electricdruid.net/wp-content/uploads/2018/09/TiltAndBaxMidSchematic.png)
You can indeed make it more peaky https://www.diystompboxes.com/smfforum/index.php?topic=24359.msg192007#msg192007
That 'looks' pretty nice though, actually not too dissimilar from a big muff sweep.
Quote from: Scruffie on September 17, 2018, 11:09:56 AM
You can indeed make it more peaky https://www.diystompboxes.com/smfforum/index.php?topic=24359.msg192007#msg192007
Thanks, but you'll notice I've already gone beyond their recommended 10:1 "narrow" ratio for the caps. I fiddled about with various combinations, but it looks like there's a limit to how narrow a band you can get out of this arrangement. But that's only an educated guess based on some experiments. I'd be interested to hear if it's possible to get high Q peaks or notches out of it somehow - not for this circuit necessarily, but just for curiosity.
Quote
That 'looks' pretty nice though, actually not too dissimilar from a big muff sweep.
Yeah, the Tilt control is pretty much the Big Muff lowpass versus highpass type of thing. The difference comes with the Mid Boost/Scoop control. With the tilt set neutral, you get a notable mid hump or mid scoop. With a bit of tilt, you can get a mid notch or resonance, and with a bit more tilt, you can extend or reduce the range that you hear by putting back or removing more of the centre.
Overall, I hope the second control adds enough extra options to make it worthwhile.
Oh yeah I get that the tilt is basically a big muff without the scoop but I meant the general sweep shapes were comparable but obviously with more flexibility and the ability to go totally neutral by centring each control now.
I guess the only problem now would be if it offers too much control and the interaction feels unnatural. To the breadboards :)
How difficult would it be have variable Q (should one wish to go down that road)?
Quote from: Ben N on September 17, 2018, 04:28:57 PM
How difficult would it be have variable Q (should one wish to go down that road)?
Not very difficult. You'd replace the baxandall stage at the end with a gyrator-based mid EQ instead, and you could have variable Q and a reasonably variable frequency too (about 4.5:1 IIRC).
The downsides are that the resonance changes as the frequency is shifted (although if you've got a resonance control you could compensate that, at least at one end of the pot) and that as I mentioned, the boost/cut tends to happen mostly at the ends of the range and there's not much action in the centre of the pot.
It's a swings/roundabouts type of thing, as they often are. You choose which compromises you make.
I really like the idea of this two-knob tone control. I always loved the tilt-EQ in my Diamond compressor clone. It does not give the accuracy like a graphic equalizer but is a great tool to make effective adjustments just with one knob. Additionally it's great to have the opportunity to just leave the response flat.
I would like to include your idea in a project I'm tinkering with. I'm aiming for some kind of transparent overdrive with a nice tone control section.
However, can you lead me to some more detailed information on how to design the baxandall mid-control? I've tried several different resistor- and cap-values in Spice to see what they do, but are there any "design-rules" one should follow? Most of the information I find is about Treble-Bass Baxandall tone controls.
What would you guys suggest would be a good center-frequency for the mid-control? Something around 700 Hz maybe? And the same question I'm wondering regarding the tilt eq. I'd be happy about some further input.
Thanks!
Sorry iefes, I don't know of any handy "rule of thumb" type information for how to calculate the values. It would certainly be nice to have. I've done this just by experimentation in LTSpice, and if you've got Spice too, that's the course of action I'd recommend.
What I do know is that increasing the ratio of the two caps (I've got 33/2.2=15, but 10 is good too) gives a more peaky/narrower band and more equal values does the reverse. Beyond that, double the values to go down an octave, or halve them to go up an octave. Then pick the nearest thing that is realistic (e.g. 4n7 not 5n if you're looking for half a 10n) and try it in the sim. Rinse, repeat.
I think 700Hz sounds like a good centre for mids, yes. Rod Elliot of ESP makes an argument that 640Hz is the geometric "centre" of the human hearing range, based on octaves from 20Hz to 20KHz. Certainly a bit lower than the typical 1KHz is better. I used 800Hz in the design above, which might still be a bit high but we'll see when I get to build it.
Are you familliar with this: http://www.muzique.com/lab/tone3.htm
The title might be a bit misleading. It basically describes a method to add a mid-control to BMP style tone control... It actually just changes the cutoff of the treble side, but in practice when combined with the bass side it becomes a mid control.
The controls might be more interactive than what you are looking for... And the mid control might not be narrow enough (it might be more musical that way though... And as a passive circuit it technically offers only cut (you can always add a gain stage to it). But anyway it's so simple it's probably worth checking out.
@ Elektrojänis: Yes, that's a great tone control and I know this one. There's a reason why it's included in so many effects. However, I'm trying to find a tone control that offers completely flat response and very predictable tone shaping, i.e. no strong interaction between the controls. And I'm just curious :D
@ Tom: Thanks heaps! Some very good information, indeed. In the meantime, I found the 1980 National Semiconductor Audio Handbook which has some information on Baxandall type mid controls. This might also be interesting for you or others, if you don't have it already. They use a wider Q with the capacitor on the wiper being larger than the bridging capacitor.
I'm wondering if the ratio of 15 isn't a bit too much.
The Handbook can be downloaded here: https://ia800604.us.archive.org/9/items/bitsavers_nationaldaAudioRadioHandbook_17034677/1980_National_Audio_Radio_Handbook.pdf (https://ia800604.us.archive.org/9/items/bitsavers_nationaldaAudioRadioHandbook_17034677/1980_National_Audio_Radio_Handbook.pdf)
A lot of experimenting to do :D
" no strong interaction between the controls."
That's a tough one.....
First off, this is a reply to the firts post, the rest was tl;dr.
1+2+4 are encompassed by the big muff tone stack. You could add a quite aggressive mid boost to counter the mid cut. Would be quite do-able with 2 pots... Ill draw something up in a bit, when im home... Maybe even the "inverted bmp tonestack" (with set resistors instead of the pot) panned against the conventional one...
Ow yeah, ill ask a teacher of mine for advice, he's also an audio freak
Quote from: iainpunk on September 26, 2018, 07:14:35 AM
First off, this is a reply to the firts post, the rest was tl;dr.
1+2+4 are encompassed by the big muff tone stack. You could add a quite aggressive mid boost to counter the mid cut. Would be quite do-able with 2 pots... Ill draw something up in a bit, when im home... Maybe even the "inverted bmp tonestack" (with set resistors instead of the pot) panned against the conventional one...
Ow yeah, ill ask a teacher of mine for advice, he's also an audio freak
Owkay, tis was a bad-ish idea, the problem is that , when all knobs are in neutral, you have 2 notches which are cut quite violently, this wil probably sound odd/unique. Ill draw up the schematic in 20 minutes, when im home, and a crude amplitude response sketch
Crude drawing:
(https://i.postimg.cc/m1PFDxH2/IMG_20180926_145405.jpg) (https://postimg.cc/m1PFDxH2)
The values A,B,C,D, are up to taste, however, i recommend the big muff values.
This is a crude amplitude response a teacher of mine drew:
(https://i.postimg.cc/D43KWLWJ/IMG_20180926_145341.jpg) (https://postimg.cc/D43KWLWJ)
If you are owkay with cutting notches around the 500 and the 1300, this is good-ish. The 1000 hz is not affected. The notches exist because of the phase difference between the 'inverted' and the normal bmp filter.
Quote from: iefes on September 26, 2018, 06:27:49 AM
@ Tom: Thanks heaps! Some very good information, indeed. In the meantime, I found the 1980 National Semiconductor Audio Handbook which has some information on Baxandall type mid controls. This might also be interesting for you or others, if you don't have it already. They use a wider Q with the capacitor on the wiper being larger than the bridging capacitor.
I'm wondering if the ratio of 15 isn't a bit too much.
The Handbook can be downloaded here: https://ia800604.us.archive.org/9/items/bitsavers_nationaldaAudioRadioHandbook_17034677/1980_National_Audio_Radio_Handbook.pdf (https://ia800604.us.archive.org/9/items/bitsavers_nationaldaAudioRadioHandbook_17034677/1980_National_Audio_Radio_Handbook.pdf)
That National book is very helpful, thanks. Finally a proper reference, instead of just the usual circuits regurgitated.
Quote
A lot of experimenting to do :D
Yes indeed! You might very well be right that the ratio of 15 is too much. I suspect that beyond ten it doesn't actually make much odds, but we'll see. I've run up a PCB to test out this idea, and I'm going to experiment with the values a bit once I get the board.
@iainpunk: That's a pretty interesting little circuit, and a quirky response. Would give something a character of it's own, for sure. Bookmarked for future reference!
Quote from: ElectricDruid on September 26, 2018, 09:12:16 AM
... I've run up a PCB to test out this idea, and I'm going to experiment with the values a bit once I get the board.
Definitely looking forward to the results. I'll as well try to play around with the values a little bit on the breadboard.
Got something:
(https://i.postimg.cc/fJDnpkyw/IMG_20180926_164927.jpg) (https://postimg.cc/fJDnpkyw)
It has 3 parts:
A)
Standard big muff tone stack
B)
A rather wide notch filter in the feedback loop of an opamp, making it a booster. The bandwidth is from 400 to 1500 and the boost is 20db. This counter acts the intrinsic mid cut from the bmp tone control and even boosts the mids with 6db
C)
Buffer and mixer for amount of mids boosted.
Hope you like it. Im gonna test it tomorrow around this time. Ill keep you updated
Quote from: iainpunk on September 26, 2018, 10:57:42 AM
Hope you like it. Im gonna test it tomorrow around this time. Ill keep you updated
Yeah, 'tomorrow' became the day after tomorrow, which is today. It does work, i haven't checked simulations, but it works irl. It does a good mid boost, the mid scoop leaves something to be desired, maybe change up some capacitor values there, but over all, it works quite well.
I tested it after a simple fuzz pedal that i build a few years ago and a jfet distortion, it works best on the distortion, but the fuzz really benefits from a mid and trebble boost.
Just found this in the wild. It is the tonestack for Wampler sovereign. Its response is not necessarily like the first post, but is a simple way of getting a tilt + mid control.
(https://www.dropbox.com/s/dqjbm9c4v2njlwx/sovereigntone.png?raw=1)
Here's what I've got so far - a fairly basic high gain distortion with these tone controls:
https://electricdruid.net/wp-content/uploads/2018/09/HardBargainSchematicPg1.jpg (https://electricdruid.net/wp-content/uploads/2018/09/HardBargainSchematicPg1.jpg)
(https://electricdruid.net/wp-content/uploads/2018/09/HardBargainSchematicPg1.jpg)
https://electricdruid.net/wp-content/uploads/2018/09/HardBargainSchematicPg2.jpg (https://electricdruid.net/wp-content/uploads/2018/09/HardBargainSchematicPg2.jpg)
(https://electricdruid.net/wp-content/uploads/2018/09/HardBargainSchematicPg2.jpg)
This is test platform as much as anything. I expect to tweak the values (particularly the cross-over point of 800Hz for the Tilt and Mid controls). You'll also see I've left the option of asymmetric/symmetric clipping open, and not decided how much volume and top-cut to apply. With tone controls set flat, I don't think you want all the high-end fizz, so some roll-off is probably required, but I don't know how much yet. There's some in the drive stage already, so apply to taste.
The variable part of the gain goes from x2 to x102, but given that there's a x4.3 gain on the way in, that's really x8.6 to x438! That's pretty serious gain. In fact it might even be too much, we'll see. The main point is that the parts are in the right places and the values can be tweaked once I've got a board to play with. It also breaks an unwritten rule of mine and uses an odd number of op-amps. If you're going to use three 8-pin chips, you might as well use six op-amps as five. But I can't see much benefit in adding a sixth, so I've left it as-is. Suggestions welcomed if you think it would benefit from one more.
Thanks,
Tom
Buffered V.Ref could be helpful for the layout with that much gain or a buffered volume pot never goes amiss, neither adds any parts and well, why not.
Quote from: ElectricDruid on September 28, 2018, 06:33:48 PM
The variable part of the gain goes from x2 to x102, but given that there's a x4.3 gain on the way in, that's really x8.6 to x438! That's pretty serious gain. In fact it might even be too much, we'll see. The main point is that the parts are in the right places and the values can be tweaked once I've got a board to play with. It also breaks an unwritten rule of mine and uses an odd number of op-amps. If you're going to use three 8-pin chips, you might as well use six op-amps as five. But I can't see much benefit in adding a sixth, so I've left it as-is. Suggestions welcomed if you think it would benefit from one more.
Thanks,
Tom
Hi, Tom. Is the input buffer really necessary? Maybe it could be skipped, with appropriate changes made to a drive stage gain. For example, VR1 can be 500k, R9 can be 6.8k, making the gain from 7.8x to 501x. Without a buffer, there are only two TL072 to be laid out.
Watching this thread with interest, this tone control looks promising. Can't wait to hear the demos.
Quote from: Scruffie on September 28, 2018, 06:59:22 PM
Buffered V.Ref could be helpful for the layout with that much gain or a buffered volume pot never goes amiss, neither adds any parts and well, why not.
Thanks Scruffie
I did wonder about buffering after the volume pot for the reasons you give, but buffered Vref hadn't occurred to me. Do you think it might help keep noise down?
Probably only so that Dougal would notice :D But it's nice to over design sometimes.
I do recommend a buffered vref. or as some manufacturers call a buffered vref., "Phantom Ground". But i usually use a type of opamp with a Phantom Ground output pin already embedded in the ic: the TS925.
(https://i.postimg.cc/v1P0MX4s/l010120-14.jpg) (https://postimg.cc/v1P0MX4s)
I would almost suggest a single wave folder stage, it really gives a distortion pedal a 'grindcore' tone and feel, if you are in to that kind of stuff.
(https://i.postimg.cc/hQ8x4P2d/Screenshot_20180911-233451_2.png) (https://postimg.cc/hQ8x4P2d)
Putting a switch parralel to the diode pair negates the wave folding effect. I recommend a gain of 5 to 10 before the folder for the best effect.
Im sorry if my post is kinda/partially off topic, but this thread really ties in with my preamp project.
God speed,
Iain
Quote from: iainpunk on September 29, 2018, 01:27:00 PM
I do recommend a buffered vref. or as some manufacturers call a buffered vref., "Phantom Ground". But i usually use a type of opamp with a Phantom Ground output pin already embedded in the ic: the TS925.
(https://i.postimg.cc/v1P0MX4s/l010120-14.jpg) (https://postimg.cc/v1P0MX4s)
In thirty years, I've never come across one of those! Just goes to show that there's always stuff to learn!
Quote
I would almost suggest a single wave folder stage, it really gives a distortion pedal a 'grindcore' tone and feel, if you are in to that kind of stuff.
(https://i.postimg.cc/hQ8x4P2d/Screenshot_20180911-233451_2.png) (https://postimg.cc/hQ8x4P2d)
Putting a switch parralel to the diode pair negates the wave folding effect. I recommend a gain of 5 to 10 before the folder for the best effect.
That's an interesting little snippet too. Compare and contrast with the typical allpass filter stage from your favourite phaser.
Thanks Iain.
Quote from: iainpunk on September 29, 2018, 01:27:00 PM
Putting a switch parralel to the diode pair negates the wave folding effect.
Wouldn't that also invert the phase? Not always a problem of course but worth mentioning.
That Op Amp type is a new one on me too, rail-to-rail to boot but digikey at least is listing all versions as obsolete, that was a fun new part for 30 seconds.
Wave folding always does stuff with the phase, and even the frequency. It blurs the line between in phase and put of phase since it is amplitude depending where the peak of the wave lies.
Ow, i only know of the parts existance because i discovered 2 of them in a pile of electronic components i inherited from my grandpa. They work good, but im not basing any designs on that opamp because its obsolescence. I'll try to find a suitable replacement one day, but ill keep using this one on my breadboard for convenience. Most of my prototype pedals never make it off of the breadboard anyway. (Although i regularly use my prototypes at gigs or jam sessions)
But let's not go to far off topic.
I made a mistake in this comment:
Quote from: iainpunk on September 28, 2018, 09:23:52 AM
Quote from: iainpunk on September 26, 2018, 10:57:42 AM
Hope you like it. Im gonna test it tomorrow around this time. Ill keep you updated
Yeah, 'tomorrow' became the day after tomorrow, which is today. It does work, i haven't checked simulations, but it works irl. It does a good mid boost, the mid scoop leaves something to be desired, maybe change up some capacitor values there, but over all, it works quite well.
I tested it after a simple fuzz pedal that i build a few years ago and a jfet distortion, it works best on the distortion, but the fuzz really benefits from a mid and trebble boost.
It should say "it does a good mid scoop, but the mid boost leaves something to be desired" in stead of the other way around :icon_redface:
> I've never come across one of those!
Because generally, a 14-DIP plus two resistors beats a 16-DIP pack.
Although the TS925 does not seen to come in any sort of DIP.
NO stock at Mouser. DigiKey has some in-stock, but Two Bucks each, yowsa! All listed as "obsolete".
I can buy TL072 for 19 cents (SMD; DIP has risen to a buck at DigiKey). Two '072cp and two 2-cent resistors *may* come to the same price as a TS925, but better layout flexibility.
The TS925 does add a Vref buffer and high output current. Interesting part. But I've obsoleted several chips already. ATM a '07x seems like a better long-term bet than something ST introduced 6 years ago and is already rare.
I tried yours out Tom, the interaction was good in that it offered several different tones but wasn't so interactive as to be a pain to set but I would say it's better for shaping a sound than tailoring it, the best analogy I could give would be good for a muff, bad for a screamer, uninspired for cleans.
It might be preferable as a more universal tone control using a Klon style shelving filter.
Ok, that doesn't sound entirely negative! That's a good start!
What do you mean about the "interaction"? In theory, these controls shouldn't interact much, but in practice it will feel like that because the mid control boosts or cuts the centre region that the tilt control also affects. Is that how it comes across? Anything else you can tell me before I get a chance to play with it? Did it make you feel that the mid peak/scoop should be lower/higher? Is the boost/cut range reasonable? Or totally way over the top?
I guess the question is: "Could you do better with only two knobs if they were somehow otherwise arranged?" You could have simple Bass and Treble knobs and leave a gap in the middle for an apparent mid-boost or mid-cut, for example. Would that be an improvement? To me, I doubt it, but I haven't played with it much yet. Or you could have a simple parametric EQ, with a frequency control and a boost/cut control, and leave it at that. That offers some different possibilities, but in some ways isn't so versatile. It's a difficult question, with no right answers I suspect.
I had an email today that the boards for this have shipped, so I might have something to report shortly...ish. Usually it takes them weeks to get through customs, but that's normal, if tiresome.
I only had 15-30 minutes to try it so I can't offer a huge amount of insight yet, they were just the first feelings I got running it through an low gain overdrive design I had.
That is precisely how it comes across in terms of interaction, actual placing of the scoop etc, well it depends what you're going for, from what I remember I wouldn't say the mids were placed well if you wanted a scooped mids boosted bass metal sound and the Q could have been a bit wider at the peak for a more screamerish response but they weren't out of place. The cut and boost was very pleasing actually, from playing with these before they can be a bit OTT but the range was where I'd want it.
Two knobs is always difficult as there's always going to be that little something missing. I do think it would be more practical with the Klon style where you've got a fixed response up to 700hZ and can then cut or boost the treble just because it's rare you want to remove all the bass or all the treble and as long as the circuit has ample of both already you're in to tailoring territory which I would say with the restricted control is probably the best use of this sort of set up.
Certainly not a write-off though, it just depends what it's stuck with and what you're hoping to achieve in the individual circuit, which is true of any design.
I've got a "background project" in mind for this too, which is a multi-voice drive pedal. The idea is; take the input, split it three ways, add a variable drive to each channel, then run it through one of these tone stages, followed by a short (chorus-ish) delay.
I was hoping that the tone controls would be enough to give two or three significantly different drive responses, such that if they were mixed together with slightly different delays they would give the effect of multiple guitarists playing *very* tightly! So one more bass, one mid-scooped, one more peaky, perhaps. Dunno which of those should be un-delayed, and which should be later. Haven't tried that yet, either. But I reckon there's room for a really FAT drive sound with multiple separately tuned drives all working together. I may yet be proved completely wrong about this, we'll see. It's happened before...;)
Hi all! Any new insights gained from breadboarding/prototyping?
I got the idea to implement the two tone-controls just using one opamp (+ input buffer), similar to the baxandall style circuitry. Spice says it should work, but is there any disadvantage to do it like this?
The frequency response seems to act a bit strange close to maximum settings. E.g. with the tilt control rolled fully back and the mid-boost cranked, there's no pronounced mid-hump observable. But the extreme settings are probably not being used anyway. Or maybe with some fine-tuning we could work out good values.
What do you think of this? I'll try to put it on the breadboard this weekend.
Btw: I breadboarded the mid-control and found that using 15n for the wiper-cap and 4n7 for the bridge cap yielded more like a volume-control because the band was to wide. I've now values of bridge: 10n, wiper: 4n7
I've read that the cap on the wiper should be bigger than the bridged cap and that's how it's done commonly in baxandall style controls, but in my case I couldn't really get a nice mid-range control out of it.
(https://i.postimg.cc/KKv91wWT/Bildschirmfoto-2018-10-20-um-10-28-46.png) (https://postimg.cc/KKv91wWT)
Quote from: iefes on October 20, 2018, 04:31:08 AM
I got the idea to implement the two tone-controls just using one opamp (+ input buffer), similar to the baxandall style circuitry. Spice says it should work, but is there any disadvantage to do it like this?
No, I don't think so. The magic of op-amps is such that it should be equivalent to doing it with two. And who
doesn't like to save an op-amp?!
Quote
The frequency response seems to act a bit strange close to maximum settings. E.g. with the tilt control rolled fully back and the mid-boost cranked, there's no pronounced mid-hump observable. But the extreme settings are probably not being used anyway. Or maybe with some fine-tuning we could work out good values.
With the tilt control all the way to one side or the other, the mid peak just brings the level of the centre up to the boosted level of the tilt, so you don't see a hump although it's still there. What you do get is a choice about whether the centre is boosted or not, effectively changing the centre point for the tilt.
Quote
Btw: I breadboarded the mid-control and found that using 15n for the wiper-cap and 4n7 for the bridge cap yielded more like a volume-control because the band was to wide. I've now values of bridge: 10n, wiper: 4n7
I've read that the cap on the wiper should be bigger than the bridged cap and that's how it's done commonly in baxandall style controls, but in my case I couldn't really get a nice mid-range control out of it.
Keep experimenting, I guess. The values I used gave me +/-14dB for the mid boost/cut.
Quote
(https://i.postimg.cc/KKv91wWT/Bildschirmfoto-2018-10-20-um-10-28-46.png) (https://postimg.cc/KKv91wWT)
Look into ".step" for stepping through parameters if you don't use it already. Being able to see a range of responses on one graph is invaluable for things like this. There's examples of using this to "fake a pot" on my LTspice screenshot from 17th sept.
Thanks for your thoughts! I've used the .param command before but not in a more complex way like you did for the potentiometer simulation. Thanks for the tip. Attached is an updated version of the circuit together with the frequency response. This gives me roughly +/- 6dB of tilt control and +/-8 dB of mid control. I think this should be enough range for my purpose. I loved the tilt-control in my Diamond Compressor and the +/- 6dB it provided were plenty.
The center frequency of the mid-control seems to shift a bit depending on the position of the tilt-control so this will need some tweaking on the breadboard.
(https://i.postimg.cc/8F5TRhP0/Bildschirmfoto-2018-10-20-um-12-00-42.png) (https://postimg.cc/8F5TRhP0)
Looks good!
T.
Lots of interesting ideas here! Thanks to everyone!
I need to add, that the response with both circuits sharing one opamp does not give the same response like with two individual opamps. I suspect the parallel resistances of both parts influence each other. Have a look at the attached screenshots. One with the mid-control parallel to the tilt-circuit and one with the mid-control disabled.
Any ideas how to achieve the same response with this setup?
Without mid control:
(https://i.postimg.cc/CBkccGrq/tilt-no-mid.png) (https://postimg.cc/CBkccGrq)
With mid control:
(https://i.postimg.cc/XBWQmrtD/tilt-w-mid.png) (https://postimg.cc/XBWQmrtD)
Sorry, but I'm not yet convinced that what you're seeing is down to interaction between the two parts of the circuit.
I notice you've got "50k * (1+Rm*mp)" and "50k * (1+Rm*(1-mp))" for the values of the two halves of the Mid pot. The "50k" isn't necessary, since that's the value of Rm (Rm for "resistance of mid", mp for "mid position"). Whether that causes any problems, I don't know.
I guess I should try sticking the two pieces together in my own LTSpice sim and see what happens...
Yea, the "50k *" is used to fix those resistor values for the moment. The "*" just disables the equation. I did it like this to see just the tilt-equalizer working and leaving the mid-control centered.
However, let us know what you find :-)
Ok, I get it, thanks.
But in that case, you've got 50K for the value of the pot in the first case, and 50+50K =100K in the second case.
Again, dunno if that makes any difference.
Ok, I tried it.
Looking at the mid control on its own, the combined version loses some resonance (the mid isn't so peaky, and the response shifts higher as you turn it away from centre. And the maximum boost/cut drops from about +/-14dB to +/-4dB.
Looking at the Tilt control on its own, it's not as badly affected, but the control loses symmetry between low and high (less highs) until you turn it up to maximum.
So I agree that the tilt network interferes with the baxandall mid control. The two networks seem to step on each others toes.
Thanks for confirming! Have you tried it on the breadboard or "only" simulated it?
However, in the meantime I tried out the mid control together with a low-gain OD I have on the breadboard at the moment and I really liked it. I used 4k3 resistors on pins 1 and 3 of the mid pot (50kB). 15n for the bridge cap and 3n3 on the pot wiper. Like this the center frequency is somewhere around 800 Hz. I tried it through my highly modified Mesa Subway Blues, which is now more of an EL84 AB763 with Master-Volume (GREAT tone!). With the mids boosted slightly I could definitely get some marshally tones out of the otherwise pretty transparent overdrive. On boost-settings above 3 o'clock the OP275 started to distort (any advice on that? I already ran it on 18V). The scooped settings are nice as well, but the overall volume seems to be lower with scooped mids. This could be improved with a narrower bandwidth. However, it is probably just "normal" that it appears more quiet to a human ear with less mids involved.
I have the tilt-control hooked up as well now, but didn't get around trying it out. My 1-year old daughter is keeping me busy :D
Attached is the schematic of the mid-control how I used it. Any tips on how to reduce distortion at higher boost settings?
(https://i.postimg.cc/87zSt1kL/Screen-Shot-2018-10-25-at-09-43-45.png) (https://postimg.cc/87zSt1kL)
Quote from: iefes on October 25, 2018, 03:45:04 AM
Thanks for confirming! Have you tried it on the breadboard or "only" simulated it?
Only simulation. But in my experience, if it doesn't even work in the sim, there's no way it works in reality. Sometimes you can get stuff that works in the sim but won't work in reality (the models not being perfect) but it rarely if ever seems to go the other way, at least for me. I realise that isn't that logical, but that's just how it goes!
Quote
However, in the meantime I tried out the mid control together with a low-gain OD I have on the breadboard at the moment and I really liked it. I used 4k3 resistors on pins 1 and 3 of the mid pot (50kB). 15n for the bridge cap and 3n3 on the pot wiper. Like this the center frequency is somewhere around 800 Hz. I tried it through my highly modified Mesa Subway Blues, which is now more of an EL84 AB763 with Master-Volume (GREAT tone!). With the mids boosted slightly I could definitely get some marshally tones out of the otherwise pretty transparent overdrive. On boost-settings above 3 o'clock the OP275 started to distort (any advice on that? I already ran it on 18V). The scooped settings are nice as well, but the overall volume seems to be lower with scooped mids. This could be improved with a narrower bandwidth. However, it is probably just "normal" that it appears more quiet to a human ear with less mids involved.
Yes, I'd guess so. The human ear is most sensitive to that frequency range, so we'll notice the lack of it disproportionally.
Quote
I have the tilt-control hooked up as well now, but didn't get around trying it out. My 1-year old daughter is keeping me busy :D
Attached is the schematic of the mid-control how I used it. Any tips on how to reduce distortion at higher boost settings?
(https://i.postimg.cc/87zSt1kL/Screen-Shot-2018-10-25-at-09-43-45.png) (https://postimg.cc/87zSt1kL)
You say you're running the op-amp on 18V, but you don't say what the signal level is. There's a decent amount of gain in that stage for some frequencies, so you need to keep the signal level sensible. +14dB is x5 gain, so with 18V, you might get 15V max output before clipping, and that implies a 3V max input before clipping. If you're feeding in significantly less than that, something else is going on.
Thanks for that info. I think I'll have time to test the whole of the circuit tonight.
Attached is the current schematic of the overdrive I'm working on. It's a MOSFET boost running into a JFET stage, so there is probably a quite large voltage entering the tone-section. What voltage swing should I expect on the output of Q2 if I'm running it on 9 or 18V?
First tests show that the circuit seems to work nicely except the clipping op-amps with high boost-settings. I'm still not sure if there are some parts that I don't need (e.g. R9?). So if you see anything which is not necessary or otherwise if I missed something important let me know please.
(https://i.postimg.cc/3k9j13L5/draft-schematic.png) (https://postimg.cc/3k9j13L5)
Ok, I've made some progress with this. I finally got my boards back:
(https://electricdruid.net/wp-content/uploads/2018/11/DSCN6774.jpg)
And I build one up and tested it. Apart from a few very minor stupidities on the PCB, it all works fine. And I'm pretty happy with the tone controls.
(https://electricdruid.net/wp-content/uploads/2018/11/DSCN6771.jpg)
I'd hoped to be able to go from a heavy mid-scooped sound to something very forward and in-your-face. And the Mid control does pretty much do that. At maximum cut, it gives a heavy scooped sound, and you can darken it or lighten it a bit with the Tilt control. I found a little bit of treble tilt helped sharpen it up.
With the Mid right up, you get a very clear sound that I associate with the sixties. That bright crunchy very forward sound, almost a cocked wah sound. Like that, I found I was happy leaving the Tilt neutral, but you've got more bass or more treble if you need it. You can also back the gain off smoothly to give a much softer overdrive sound.
Ignoring the Mid control for a minute, you've got the basic Big Muff range of tones on the Tilt control, but without the slight mid-scoop, unless you put it back with the Mid control. So...it's not half bad, and probably more interesting than "Bass" and "Treble" controls, which is the other obvious two tone control combo.
By now, you probably want to hear what it sounds like.
Here's some funky chops with lots of mid and plenty of gain:
https://electricdruid.net/sounds/hardbargain/HardBargain1.mp3 (https://electricdruid.net/sounds/hardbargain/HardBargain1.mp3)
Now a really dirty fuzz sound with a sixties edge to it:
https://electricdruid.net/sounds/hardbargain/HardBargain2.mp3 (https://electricdruid.net/sounds/hardbargain/HardBargain2.mp3)
Something heavier and more doom-laden. This sounds a bit rubbish on laptop speakers but kicks a$$ in reality:
https://electricdruid.net/sounds/hardbargain/HardBargain3.mp3 (https://electricdruid.net/sounds/hardbargain/HardBargain3.mp3)
The "Sunshine" riff with a softer, more overdrivey sound:
https://electricdruid.net/sounds/hardbargain/HardBargain4.mp3 (https://electricdruid.net/sounds/hardbargain/HardBargain4.mp3)
Enjoy!
Tom, you rock, man.. !! :beer: :beer: :beer:
<Apart from a few very minor stupidities on the PCB>
Could you plz elaborate..?? :icon_cool:
Quote from: antonis on November 07, 2018, 07:43:27 AM
<Apart from a few very minor stupidities on the PCB>
Could you plz elaborate..?? :icon_cool:
I generally use a 0.3" footprint for caps, as you can see on the silkscreen/PCB. This lets me add an extra pad in the gap in-between and then I can fit either 0.2"/5mm or 0.3"/7.5mm spaced caps, depending on what I've got handy. Makes the board more versatile.
On this one, I added all the extra pads, but there are four of them I forgot to connect up to the 0.3" cap footprint. I had to bend the cap legs over on the solderside to make a connection to the 0.3" spaced pad. A nuisance, but not serious.
I noticed this on one cap before I started building, and then buzzed them all through and discovered I'd forgotten several.
Apart from that it fired up first time perfectly, so that's a success.
Great stuff Tom. My Overdrive is still on the breadboard but I'm also quite happy with the tone-controls on it. What are the center frequencies you settled with? And how much boost/cut do you have available for each the mid and tilt-control?
Quote from: iefes on November 08, 2018, 03:21:50 AM
Great stuff Tom. My Overdrive is still on the breadboard but I'm also quite happy with the tone-controls on it. What are the center frequencies you settled with? And how much boost/cut do you have available for each the mid and tilt-control?
It's centred at 800Hz, and it has 14dB cut/boost on the Tilt control and a bit less on the Mid (maybe +/-10dB)
(https://electricdruid.net/wp-content/uploads/2018/09/TiltAndBaxMidPlot.png)
It's basically the circuit from the simulation I posted back in September, now actually built in reality. I posted the schematic too:
https://electricdruid.net/wp-content/uploads/2018/09/HardBargainSchematicPg1.jpg (https://electricdruid.net/wp-content/uploads/2018/09/HardBargainSchematicPg1.jpg)
https://electricdruid.net/wp-content/uploads/2018/09/HardBargainSchematicPg2.jpg (https://electricdruid.net/wp-content/uploads/2018/09/HardBargainSchematicPg2.jpg)
I built the first one as per the schematic. I used 47K/470pF for R12/C8, which gives a 6dB roll-off above 7.2KHz after the clipping. That prevents things getting fizzy. I left out R13 (so no volume reduction after clipping) and I included the one-diode-vs-two-diodes asymmetrical clipping for a little bit of harmonic interest. It'd be easy to add a SPST toggle around one of those diodes to give a Symmetrical/Asymmetrical Clipping switch, and I might add pads for that on the final PCB, but I'll tack a couple of wires on mine to see if it adds anything first.
I haven't messed with the centre frequency yet (it needs a bit more working out, since you have to re-jig both stages) but I'd like to try one with a lower centre. Maybe that 640Hz geometric centre that Rod Elliott talks about. I'll probably build another board up with different values and see which I like best.
I'm also going to add a buffer after the volume control as per Scruffie's suggestion because needing two types of parts bugs me, and it'd be a neater design with three dual op-amps rather than two duals and a single.
Quote from: iainpunk on September 29, 2018, 01:27:00 PM
I would almost suggest a single wave folder stage, it really gives a distortion pedal a 'grindcore' tone and feel, if you are in to that kind of stuff.
(https://i.postimg.cc/hQ8x4P2d/Screenshot_20180911-233451_2.png) (https://postimg.cc/hQ8x4P2d)
Putting a switch parralel to the diode pair negates the wave folding effect. I recommend a gain of 5 to 10 before the folder for the best effect.
What do you mean with 'a grindcore tone and feel' ? Middle-of-the-road Napalm Death, wall-of-mush Insect Warfare or tight-and-precise Obligatorisk Tortyr? Or more towards a mid-heavy-hm2-grind? Or maybe all-of-the-above?
Quote
Im sorry if my post is kinda/partially off topic, but this thread really ties in with my preamp project.
Please elaborate on your preamp project, I'm interested :)
Separate topic, if necessary.
Catching up to this topic - has anyone else tried the "Bone Ray" tone stack a la Merlin B? Seems like it goes in this direction. It's not totally flat in the neutral setting though.
https://books.google.com/books?id=9kMDBAAAQBAJ&pg=PA206&lpg=PA206&dq=%22bone+ray%22+tone&source=bl&ots=Oz5oUrvdgC&sig=ACfU3U1fwRtWWjE7xveWgxEKetiIeCdbqQ&hl=en&sa=X&ved=2ahUKEwi2-pvJ_ermAhUST98KHVXrCOMQ6AEwBHoECAoQAQ#v=onepage&q=%22bone%20ray%22%20tone&f=false (https://books.google.com/books?id=9kMDBAAAQBAJ&pg=PA206&lpg=PA206&dq=%22bone+ray%22+tone&source=bl&ots=Oz5oUrvdgC&sig=ACfU3U1fwRtWWjE7xveWgxEKetiIeCdbqQ&hl=en&sa=X&ved=2ahUKEwi2-pvJ_ermAhUST98KHVXrCOMQ6AEwBHoECAoQAQ#v=onepage&q=%22bone%20ray%22%20tone&f=false)
> the "Bone Ray" tone stack .... https://books.google.com/books...........
Those Amazon "Look Inside!" pages go in and out of view at random times and places. There's a dozen+ pages of tone controls, of 300 pages (aimed at tubes but much is universal) and you SHOULD buy the book.
But meanwhile here's a snip for thread reference:
(https://i.postimg.cc/QHrNNGVF/Bone-Ray-Tone-Stack.gif) (https://postimg.cc/QHrNNGVF)
Mid ctrl with automatic level adjustment.
(http://mrotqch.web.fc2.com/stomp/Other/2022C611.png)
(Simplified from previous circuit (https://www.diystompboxes.com/smfforum/index.php?topic=129283.0#msg1248796).)
Coexistence with tilt ctrl.
(https://i.postimg.cc/3d0bwxP7/2022C903.png) (https://postimg.cc/3d0bwxP7)
Tilt and Mid are not completely independent.
(https://i.postimg.cc/hhYQrDhX/2022C903.gif) (https://postimg.cc/hhYQrDhX)
Thanks to Druid for bringing me afflatus.
[fixed img link]