built a boost with a 15.5kHz LPF... thoughts on frequency?

[Passinwind]

that is really cool i read it for a bit.

i am set on what i am doing at the moment, just adjusting it to a different frequency. its just a few minutes of math, and some soldering when i get around to it.

what i am seeking is a heavy dB boost that takes out the 'attack' and 'pop' although some may like that. i am just bored and entertaining myself with this.

OK, but what order LPF filter are you using (i.e 1st, 2nd. 3rd, 4th, etc.)? It matters a bunch as far as what frequency corner you'll want/need to use. The one in the thread I pointed you at is second order and probably dosn't go low enough for what you are shooting for. 2-3 K is getting warmer iMO, but I think you may easily want to go at least another octave lower.

 

[Skullsuicide99]

OK, but what order LPF filter are you using (i.e 1st, 2nd. 3rd, 4th, etc.)? It matters a bunch as far as what frequency corner you'll want/need to use. The one in the thread I pointed you at is second order and probably dosn't go low enough for what you are shooting for. 2-3 K is getting warmer iMO, but I think you may easily want to go at least another octave lower.

I am going to shoot for 1550hz because the math is really quick compared to running the equation again and I can just test it real quickly.

 

[Rip Van Dan]

Huh. I will do some tweaking for sure then maybe 1.5kHz would be good, as the math is quicker.

How do you guys feel about 30dB of boost? I can tweak that too while I am at it.

Just an FYI about 1.5KHz...that is not highs, that is high-mids. You will lose a lot of any upper frequency clarity, sparkle, or whatever you want to call it if put it that low. If your EQ is the shelving type, then up it just a bit. The treble EQ on my Eden amp is at 2K (which really is a high-mid frequency) but boosting it or cutting it boosts or cuts everything above it. Setting a Low Pass Filter there at 1.5KHz would stop all the frequencies above it.

In conjunction with my bass and treble shelving EQ's, my amp has three semi parametric controls that let you select what frequency you want to boost or cut. A true "parametric control" will boost/cut in a spike with just a little influence to the frequencies directly above or below it. A semi-parametric is more of a mountain shape with a more gently approach-to and departure-from the targeted frequency. It's what I would consider a more musical adjustment to deal with.

30db of boost or cut is really way too much. 15db would sound like 1½ times as loud or as soft as the other frequencies. 30db is overkill and makes your finer adjustment of boost/cut from that control much harder to achieve because just a little movement will make a gig difference. Again to my Eden amp, it has 15db boost/cut on all its EQ controls. They also have click controls on the pots. A "two click" change in the EQ makes a noticeable difference in your sound. At 30db, that would be a 1-click change or less. So, in my opinion, a 30db cut/boost is too much.

 

[sunbeast]

What is the boost intended for? If it is to push some sort of drive circuit, then a roll-off of low-end would probably be more useful. With my tube heads (and most drive pedals), I personally prefer boosters that boost highs and cut highs which helps tighten up the drive tone. YMMV

 

[mcnach]

i designed/ tweaked a boost for bass (about 30db variable), and i put a ~15.5kHz LPF on it. I haven't had the best amp to try it on, i am just curious to see what you think of a ~15.5kHz LPF regarding bass signal.

i will happily take all thoughts, opinions, and critique.

cheers!

edit: typo

I think it's too high a frequency to make much of an impact. I use an adjustable LPF sometimes and I never set it higher than 2-3 KHz, and often I go for a LOT lower (I can go down to 145 Hz).

What are you trying to achieve, why did you choose that frequency?

If you just want to remove/enhance finger string noise, it may be better to go down to 8-10 KHz, but even then the effect is going to be moderate in practice. What speakers do you use? Unless you use tweeter/horns there may not be a lot being reproduced above 6-8 KHz anyway. My current favourite cabs roll off treble at 6-7 KHz... and they have plenty of treble.

 

[mcnach]

OK. I just wish I could put it through a decent rig to see. It totally neuters a guitar (which is obvious). Maybe drop it to 12kHZ? I just want to darken it up a bit.

It's all experimental at this point. Until I can try it on a solid rig, I will leave it as is but may add a HPF @ 40hZ. That could be interesting.

At 15.5 KHz it cannot 'neuter' a guitar... are you sure your frequency measurement is correct? It'll remove some of the extreme zing of new strings and some finger noise but that's about it.

For HPF, 40 Hz will barely be heard, but it's a good frequency if you want to protect your speakers and make the amp not work quite so hard. If you want to set a hard set frequency, can you make/use an adjustable LPF/HPF so that you can find out exactly what works best for your purposes?

 

[Skullsuicide99]

I think it's too high a frequency to make much of an impact. I use an adjustable LPF sometimes and I never set it higher than 2-3 KHz, and often I go for a LOT lower (I can go down to 145 Hz).

What are you trying to achieve, why did you choose that frequency?

If you just want to remove/enhance finger string noise, it may be better to go down to 8-10 KHz, but even then the effect is going to be moderate in practice. What speakers do you use? Unless you use tweeter/horns there may not be a lot being reproduced above 6-8 KHz anyway. My current favourite cabs roll off treble at 6-7 KHz... and they have plenty of treble.

It's a variable boost. I am going for a hard cutoff that is not variable relating to the boost level. I want to kill anything treble or bright, and have a massive thunderous low end. It would not be an always on or anything, purely a low, dark accent for a few occasions. I doubt I will use near 30db, but I left myself some extra room. I am going to experiment between 1.5kHz - 3kHz. No need or desire for parametric. Just kill the top and still just figuring out where to kill it.

Again I am bored and experimenting and I guess I will see what it does. Single knob for boost, the frequency will always be on unless the pedal is bypassed. The LPF is fixed, and that is fine with me.

I am going to learn either way, sink or float. Give me a few days and maybe I will have a clip. It's just a mental exercise to ease boredom.

 

[mcnach]

Huh. I will do some tweaking for sure then maybe 1.5kHz would be good, as the math is quicker.

How do you guys feel about 30dB of boost? I can tweak that too while I am at it.

30dB boost is LOTS! But that won't hurt as long as you can adjust it to taste when needed.

1.5 kHz is a much better threshold frequency for a LPF. It will definitely take out the top end in a noticeably but musical way... but I'd want lower probably. To give you an idea, the VLE filter on MarkBass heads goes down to 250Hz, and even at this lowest setting the effect is not extreme. It is VERY noticeable, but it's a very usable sound. That's why I wanted an LPF that goes lower and ended up getting one that goes down to 145Hz. Now THAT is pretty low and I don't often go that low, but down to 300-500 Hz? Very often.

 

[Skullsuicide99]

At 15.5 KHz it cannot 'neuter' a guitar... are you sure your frequency measurement is correct? It'll remove some of the extreme zing of new strings and some finger noise but that's about it.

For HPF, 40 Hz will barely be heard, but it's a good frequency if you want to protect your speakers and make the amp not work quite so hard. If you want to set a hard set frequency, can you make/use an adjustable LPF/HPF so that you can find out exactly what works best for your purposes?

OH, trust me it neuters a guitar signal. Frequency is gotta be pretty close to 15.5kHz, as I tested the components to make sure it was accurate. If I did not disassemble it earlier I would have happily showed you a demo. I know my numbers were correct. I actually wish I had recorded it.

 

[mcnach]

It's a variable boost. I am going for a hard cutoff that is not variable relating to the boost level. I want to kill anything treble or bright, and have a massive thunderous low end. It would not be an always on or anything, purely a low, dark accent for a few occasions. I doubt I will use near 30db, but I left myself some extra room. I am going to experiment between 1.5kHz - 3kHz. No need or desire for parametric. Just kill the top and still just figuring out where to kill it.

Again I am bored and experimenting and I guess I will see what it does. Single knob for boost, the frequency will always be on unless the pedal is bypassed. The LPF is fixed, and that is fine with me.

I am going to learn either way, sink or float. Give me a few days and maybe I will have a clip. It's just a mental exercise to ease boredom.

I think that's a reasonable range for what you say you want, although the sound is quite different by thresholding at 1.5 or 3 KHz. Since you're not trying to go for a 'vintage' type of tone anyway, then I'd lean more towards 2-3 KHz...
I know about what these things sound like but not about the electronics behind them: how easy is it to try it at one frequency, and then modify to get a bit higher or lower depending on what you thing of the results?

It's a cool idea for sure, it's just that getting the right frequency may be the difference between great or meh.

Really curious to hear how you get on please let us know!

 

[sawzalot]

There are some frequency generators out there on the internet. 15.5 k is quite high, inaudible to many people over a certain age. You probably want to look more around the 4-6 k range or even lower.

 

[mcnach]

OH, trust me it neuters a guitar signal. Frequency is gotta be pretty close to 15.5kHz, as I tested the components to make sure it was accurate. If I did not disassemble it earlier I would have happily showed you a demo. I know my numbers were correct. I actually wish I had recorded it.

Our definition of neutering must be different I'm playing guitar these days with a speaker cab that rolls off at around 5 KHz and it sounds great. It tames a bit the harshest tones of single coil pickups (this is with a Stratocaster) and sounds pretty sweet (shrug).

 

[AudioTaper]

I built a buddy a +20db boost pedal (single BJT) for guitar and it's a lot of boost. Why 30db?

 

[MDBass]

i designed/ tweaked a boost for bass (about 30db variable), and i put a ~15.5kHz LPF on it. I haven't had the best amp to try it on, i am just curious to see what you think of a ~15.5kHz LPF regarding bass signal.

i will happily take all thoughts, opinions, and critique.

cheers!

edit: typo

The LPF set that high will do essentially nothing to a bass signal.

Record a bass signal in your DAW and move an LPF around while it plays back: you’ll see what I mean.

 

[Skullsuicide99]

I think that's a reasonable range for what you say you want, although the sound is quite different by thresholding at 1.5 or 3 KHz. Since you're not trying to go for a 'vintage' type of tone anyway, then I'd lean more towards 2-3 KHz...
I know about what these things sound like but not about the electronics behind them: how easy is it to try it at one frequency, and then modify to get a bit higher or lower depending on what you thing of the results?

It's a cool idea for sure, it's just that getting the right frequency may be the difference between great or meh.

Really curious to hear how you get on please let us know!

I will let you know how it goes when I get around to it. Could be great or meh. Sink or float, I am going to do what I am. Again, just intellectual exercise.

 

[74hc]

My amp has a LPF and a treble set at 10khz. Both are too high for bass. 15.5khz for bass? That's like measuring 2 grams of sugar, one grain at a time.

 

[thetragichero]

why do the math for simple rc filters?
Guitar Pedals: R-C Filter Calculator

 

[monsterthompson]

Can you utilize a DAW with a VST pass filter to model the effect for a rough idea of the result? That would be my first step, but then that’s what I’m most familiar with.

 

[Real Soon]

Whoop whoop! @ the energy of the responses thus far. I like it haha

Me personally, I'd get a lot of use on bass out of a low-pass filter with, say, two settings: 4 kHz and 8 kHz. A third setting, actually: ability to disable it in case I wanted to either piss off the neighborhood dogs or get the coloration of a cabinet's inherent rolloff.

Those settings aren't arbitrary, mind you; with a 12dB/oct rolloff, you can get lots of midrange punch and sparkle at 4 kHz, with the rolloff helping get extra frequencies out of the range of the presence band of most human voices (between 4 and 7 kHz, roughly), so it's highly functional (no pun intended) for ensemble purposes just in case the house PA isn't rolling off highs. Arguably, that point could be set at 3 kHz or so to be honest, but the difference is minor unless you're running a Rickenbacker or a super treble-set active bass or something into it.

And 8 kHz adds a lot of extra soloist & FX pedal bandwidth while controlling the really shrill stuff that some untethered chorus & drive pedals, et al etc etc can produce. It's almost akin to being off, but again, really helps manage what's going out thru the house system. Also again, could probably set it at 7 kHz with the 12dB/oct rolloff, but eh

 

[Skullsuicide99]

why do the math for simple rc filters?
Guitar Pedals: R-C Filter Calculator

Shoot. Didn't think of THAT. I am old school. Lol. I guess now the math will be faster LMAO.