a different kind of low pass filter

[bdplaid]

It's not a LPF, it's a BPF. (or a band-reject filter, if you are cutting of course.)



A wah is also a BPF. But with an even higher resonance.



If you need a LPF with a fairly decent slope, and a sweepable frequency, I believe teh state variable filter is the best choice.

Yes, the vari-mid is a BPF (hence the "mid" part in the name). My comment was musing that if the freq range could be extended higher in frequency, then it affects enough of the high freg range to make it useful for what i want to do. But alas, it does not.

I'll have a look at state variable filters, thanks.

 

[esa372]

I'm looking for a different kind of onboard bass guitar LPF...

Anyone know of such a thing?

You need to talk to Alembic.

 

[bdplaid]

I discovered that I am looking for a bandstop filter.
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In full-on setting, imagine a bandwidth from 300Hz (or lower) to 10KHz (or higher) that could be notched out; but the bottom of the bandwidth is tuneable upwards to 10K. In it's "off" mode, the notch would be a super-narrow Q in a freq range that doesn't affect bass guitar.


I was looking at it as a LPF because it stops all frequencies above a certain point. But i think the engineers look at it differently.

 

[RobbieK]

"Super Tone Control"

Yep, that's exactly what I was saying. A state variable filter. And you're right, that circuit will need modding to work in a bass. The input Z is too low, there's controls that need to be removed, and it needs a voltage divider to provide a virtual earth from a single 9volt battery. Also the quad opamp shown is probably not the best choice, if it's even still available. And it looks like the pin out for that opamp is not the standard as well if you go with a modern and easily available quad like a TL074. But I'd use a pair of modern dual opamps with better noise spec and lower current draw.

A wah is a variable notch filter.

No it's not I'm afraid. It's actually the opposite. It's a band-pass filter. A notch filter is band-reject. Notches are great for dipping out feedback in PA's or onboard acoustic guitars. It's also how phaser pedals work, with several notches being swept up and down. But as far as I can tell, that's really not what the OP seems to be asking for.

 

[RobbieK]

I discovered that I am looking for a bandstop filter.
[Invalid or Expired Link Removed]

OK, clearly, there's some work ahead. But that's a good thing! You should get yourself a breadboard and a 'scope and a multimeter.

Also I'd recommend recording some bass, and using the flexible eq's in protools/logic/ableton etc etc. The ones that let you see the frequency response as a line.

This way, you can understand frequency, Q, and what you need to design to get close to the response you like the sound of.

Also I strongly recommend learning to use one of the free spice programs that are out there. This way you can actually model filters such as the simple passive ones in your link and see just how they will compare to the digital representations you see and hear in ableton/protools etc.

In full-on setting, imagine a bandwidth from 300Hz (or lower) to 10KHz (or higher) that could be notched out; but the bottom of the bandwidth is tuneable upwards to 10K. In it's "off" mode, the notch would be a super-narrow Q in a freq range that doesn't affect bass guitar.


I was looking at it as a LPF because it stops all frequencies above a certain point. But i think the engineers look at it differently.

In that case the word "notch" is not the right one. Because that means, well, a notch, literally. What you are suggesting is going to take two filters working in parallel. One is a high pass filter at 10khz, and the other a variable low-pass filter that you can sweep from 300hz to 10khz.

Again, I would definitely try this in some recording software first to see if it really is the sound you are going for.

 

[bdplaid]

OK, clearly, there's some work ahead. But that's a good thing! You should get yourself a breadboard and a 'scope and a multimeter.

Also I'd recommend recording some bass, and using the flexible eq's in protools/logic/ableton etc etc. The ones that let you see the frequency response as a line.

View attachment 597713

This way, you can understand frequency, Q, and what you need to design to get close to the response you like the sound of.

Also I strongly recommend learning to use one of the free spice programs that are out there. This way you can actually model filters such as the simple passive ones in your link and see just how they will compare to the digital representations you see and hear in ableton/protools etc.



In that case the word "notch" is not the right one. Because that means, well, a notch, literally. What you are suggesting is going to take two filters working in parallel. One is a high pass filter at 10khz, and the other a variable low-pass filter that you can sweep from 300hz to 10khz.

Again, I would definitely try this in some recording software first to see if it really is the sound you are going for.

OK, clearly, there's some work ahead. But that's a good thing! You should get yourself a breadboard and a 'scope and a multimeter.

Also I'd recommend recording some bass, and using the flexible eq's in protools/logic/ableton etc etc. The ones that let you see the frequency response as a line.

View attachment 597713

This way, you can understand frequency, Q, and what you need to design to get close to the response you like the sound of.

Also I strongly recommend learning to use one of the free spice programs that are out there. This way you can actually model filters such as the simple passive ones in your link and see just how they will compare to the digital representations you see and hear in ableton/protools etc.



In that case the word "notch" is not the right one. Because that means, well, a notch, literally. What you are suggesting is going to take two filters working in parallel. One is a high pass filter at 10khz, and the other a variable low-pass filter that you can sweep from 300hz to 10khz.

Again, I would definitely try this in some recording software first to see if it really is the sound you are going for.

Thanks for all that, however I know what I want. If i could combine these 2 things, I'd be good:

 

[ctmullins]

Erm, ACG filter pre.

ACG EQ 01 Preamp - Best Bass Gear

 

[Bob_Ross]

I'm looking for a different kind of onboard bass guitar LPF... [snip]... I'm looking a tone circuit, preferably passive, that has fixed slope, but that slides a fixed cut (downward) slope of 12 or 18dB/octave upward and downward in the frequency range.

After 2 pages I'm pretty sure someone has already mentioned this but being Mr. Pedantic I gotta just point out that what you're looking for isn't "a different kind of onboard bass guitar LPF" ...what you describe is a LPF ("fixed slope, but that slides a fixed cut (downward) slope of 12 or 18dB/octave upward and downward in the frequency range")

And I know the TB Crowd has already mentioned Alembic, Wal, and ACG/East as fine purveyors of onboard LPFs for bass guitar.

 

[bdplaid]

Erm, ACG filter pre.

ACG EQ 01 Preamp - Best Bass Gear

saw it. way over the top for what I'd like. thanks.

 

[ctmullins]

saw it. way over the top for what I'd like. thanks.

Could you elaborate on "way over the top"? Is it simply too many features? Is it too expensive? Because based on your description, the LPF portion of the circuit sounds to me like exactly what you're looking for. The predecessor to the EQ01 was (ironically named) the EQ02, which only had one LPF section (and one HPF section). I have one in a fretless, and it does what you describe. Sounds like what you're really looking for is the LPF half of the EQ02. Not sure if anybody sells just the LPF section, but it might be worth emailing Alan Cringean and/or John East; I know both have been known to make custom versions of existing designs on request.

 

[bdplaid]

After 2 pages I'm pretty sure someone has already mentioned this but being Mr. Pedantic I gotta just point out that what you're looking for isn't "a different kind of onboard bass guitar LPF" ...what you describe is a LPF ("fixed slope, but that slides a fixed cut (downward) slope of 12 or 18dB/octave upward and downward in the frequency range")

And I know the TB Crowd has already mentioned Alembic, Wal, and ACG/East as fine purveyors of onboard LPFs for bass guitar.

Actually I didn't know that Wal/Alembic were what I was asking for, but it doesn't help me in that I can't add it to an existing bass. Not sure if they even sell such; Alembic's website has some nonsense about electronics costing a grand or two. Mere mortals fart in that general direction (apologies to Monty Python).
The ACG/East info wasn't clear that that's what is does (still not sure from what i read.) But damn it's expensive. And does much more than what I want.
Nor can I build the tone control, apparently. I was hopefully looking to build/buy a tone control with a sliding stop frequency to put in an existing bass that replaces a reg'lar ole pot with a cap bled to ground. I guess this is a lot more involved than I imagined.

 

[bdplaid]

Could you elaborate on "way over the top"? Is it simply too many features? Is it too expensive? Because based on your description, the LPF portion of the circuit sounds to me like exactly what you're looking for. The predecessor to the EQ01 was (ironically named) the EQ02, which only had one LPF section (and one HPF section). I have one in a fretless, and it does what you describe. Sounds like what you're really looking for is the LPF half of the EQ02. Not sure if anybody sells just the LPF section, but it might be worth emailing Alan Cringean and/or John East; I know both have been known to make custom versions of existing designs on request.

over the top = yes, too many features. just looking for an LPF tone control that works like (what I think could be called) a sliding stop band control.
And what you suggest is right - looking for just the LPF part of it. And $350 - 360 is a lot of money.

 

[ctmullins]

No argument about them being pricey. The earlier version was both simpler and cheaper. I got mine used from the Classifieds.

 

[bdplaid]

No argument about them being pricey. The earlier version was both simpler and cheaper. I got mine used from the Classifieds.

...and the more I look at the ACG stuff, it's just complicated on top of complex. I know ACG was trying to make something that was super-versatile, but in my experience that's a fool's errand. If one plays a P-bass, but needs a modern sound, it's ain't going to happen. If I need it to sound like a Modulus, I bring my Modulus. If I need a P-bass, that's what I bring. If I need a Jazz, I bring a jazz... MusicMan.. and on... Those sounds won't be gotten from the same bass no matter what pre is in there. I know - I've tried. Do studio work and you'll learn this quickly.

 

[mbelue]

So what's so difficult about a variable LPF? Seems like these things would be more common?
I know allot of us would like an anti-Fdeck if it were available.
Personally my Tonestyler is excellent in this regard but it's not intended for low impedance or piezo pickups.
An active circuit that is reasonably priced would certainly suit many people.
Is there a patent or something halting progress or is it just a problem of low demand?

 

[RobbieK]

If i could combine these 2 things

Sorry I thought you wanted the high treble (10Khz) still intact. I didn't mean to confuse you.

If you just want a low pass filter with a decent slope that you can sweep around, then surely the boogieman is the way to go.

you can buy them on ebay

They aren't super expensive.

Or if you want to build one yourself, the craig anderton supertone control will be fine with some mods.

If your pickups are passive, then you'll need a higher input Z. So change r13 and r14 to 220K. Leave the highpass and bandpass pots out all together, plus their summing resistors - r4&5.

To run with 1 battery, you need a voltage divider. Leave out C6&7 and those two diodes. A couple of 10k resistors and a 10uF cap will be fine. This will be your virtual earth, so anything that is connected to earth in the circuit (except R6) should instead be connected to the junction of the voltage divider (4.5V).

Connect the input from the blend pot of your bass and instead of r6, use a 10K pot as a master vol.

Oh, and as I said before, I'm not sure this opamp even still exists. If you use a more modern quad opamp, its pinout will be different.

 

[khutch]

A traditional tone control is an ad hoc low pass filter that is formed from the tone pot and capacitor as well as the pickup(s) in the bass. So you don't have a lot of freedom to make it do specific things. The best way to do what you want to do passively is to use an actual StellarTone ToneStyler or clone it yourself. According to StellarTone their circuit gives a critically damped response where most DIY versions are underdamped. If you have not used an actual ToneStyler and are basing your dislike of it on the underdamped versions then you should give the actual ToneStyler a listen.

The state variable filters we have been discussing lately will do what you want. I am really not familiar with the ones available commercially for bass guitars and I am quite surprised to hear that they sell for as much as a kilobuck. I mean, really, even if you used Cadillac components I think you would be hard pressed to put much over $50 into a DIY version. The ones that some vendors are selling apparently have a Q or peaking control as well as a frequency control. If you were to roll your own you could just use fixed resistors for the Q control and leave just the frequency knob. The state variable filter is quite a nice tool for a filter designer to use as it is completely flexible in terms of what transfer functions it can provide and straightforward to design. But if you just want a constant Q filter then you probably do not have to use a state variable approach which requires at least a quad opamp. You may be able to find another filter that will give you the frequency control you want from a dual opamp. It would take more time than I have right now to make sure of that.

For what it is worth the plots below show a traditional tone control response compared to an active LPF response using the state variable circuit in this case:

 

[bdplaid]

A traditional tone control is an ad hoc low pass filter that is formed from the tone pot and capacitor as well as the pickup(s) in the bass. So you don't have a lot of freedom to make it do specific things. The best way to do what you want to do passively is to use an actual StellarTone ToneStyler or clone it yourself. According to StellarTone their circuit gives a critically damped response where most DIY versions are underdamped. If you have not used an actual ToneStyler and are basing your dislike of it on the underdamped versions then you should give the actual ToneStyler a listen.

The state variable filters we have been discussing lately will do what you want. I am really not familiar with the ones available commercially for bass guitars and I am quite surprised to hear that they sell for as much as a kilobuck. I mean, really, even if you used Cadillac components I think you would be hard pressed to put much over $50 into a DIY version. The ones that some vendors are selling apparently have a Q or peaking control as well as a frequency control. If you were to roll your own you could just use fixed resistors for the Q control and leave just the frequency knob. The state variable filter is quite a nice tool for a filter designer to use as it is completely flexible in terms of what transfer functions it can provide and straightforward to design. But if you just want a constant Q filter then you probably do not have to use a state variable approach which requires at least a quad opamp. You may be able to find another filter that will give you the frequency control you want from a dual opamp. It would take more time than I have right now to make sure of that.

For what it is worth the plots below show a traditional tone control response compared to an active LPF response using the state variable circuit in this case:

View attachment 598521

awesome, that second graph of the state variable filter is exactly what I'm after. I could live with it in steps, but sweepable is what I'm thinking.

thanks!

 

[bdplaid]

and I've only heard the Tonestyler on YouTube, and basing on that it does not impress. to me just sounds like the same old muddy tone control with different caps.

 

[bdplaid]

Just looked at the boogieman pre. not sure it's going to get it done. I'm leery of anything that uses the word Alembic in it; had one, not a fan. But, if there were more info, particularly a graph of what it does, that might be the huckleberry. I just can't tell.