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High Pass Filter (HPF) and Low Pass Filter (LPF) Mega Thread

#201
K-2 said:
Hey guys,

Probably didn't do my homework with search properly, but though I would give it a shot.

After reading a lot of about HPF/LPF, and listening to my sound, came to a conclussion that HPF (or both in one pedal) would be great for my applications.

I see mostly positive reviews for 3 products - Broughton HPF/LPF, Fdeck and Omni Cabsim (not HPF by itself, but would give me added benefits).
The problem is - all of these pedals are made in USA and could only find a dealer in Europe for Omnicab sim (which has none in stock, and no date for restock). I am not to keen ordering from USA, paying significant amount on shipping and then getting duties/taxes applied as well (21% from value+shipping in my country).

Any good HPF products that are made/distributed in Europe? Or mentioned products are top of the line and I should just save up some extra money for shipping , D/T?

Thanks in advance guys!
Click to expand...

Broughton Audio is in Canada. (The link to Broughton = [Invalid or Expired Link Removed])
 
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#204
K-2 said:
My apologies.
What I meant is "international".
No offense intended to Canadians, Americans, Chileans etc.

Anyway, these great pedals come from overseas and I would like to avoid big shipping cost plus dutis/taxes if possible.

Will investigate the Thumpinator. That looks interesting!
Click to expand...

For Broughton, International shipping is US$40.00, which is reasonable. I cannot comment on duties :-(
 
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#205
K-2 said:
My apologies.
What I meant is "international".
No offense intended to Canadians, Americans, Chileans etc.

Anyway, these great pedals come from overseas and I would like to avoid big shipping cost plus duties/taxes if possible.
Click to expand...

Have you considered just building your own, or having someone local to you do that? @fdeck has a schematic for at least one of his earlier versions posted on his website, and there are plenty of pro audio implementations you can look at schematics for with a little effort.
 
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#206
Bassbeater said:
It would be great to have a mixer style "low-cut" hpf toggle button on my DI.
Click to expand...

I have a prototype tube DI/Preamp on my bench right now that has switchable HP and LP filters. Not so much for speaker protection as for a bit of tone shaping though they would offer some protection. Out, 60Hz and 120Hz for the HP and Out, 5k and 2k for the LP. They're basic first order filters so the rolloff is pretty gradual. Setting the HP at 60 and the LP at 5k gives a reasonable facsimile of the Ampeg 810 frequency response. I included the higher setting for non-bass instruments (the DI is not bass-specific). I may drop it to 100 but I have some testing and listening to do before I make that decision. Without the HP filter the output transformer starts to roll the response off at right around 20Hz.

NKBassman said:
I'd just like to add that, while I'm not experienced in circuit design in any way, from reading on the topic I know that even the most basic tube preamp circuits have high pass filtering built into the circuit by design, and have had for decades. It's part of "good design practice" and helps to eliminate a myriad of potential issues in the circuit.

If you ask me, there is absolutely no reason to try and pass 20 Hz signal content in a musical instrument amplifier. In any industry, optimizing a design is all about making compromises, and in the case of musical instrument amps, chopping off inaudible signal content that requires gobs of power to amplify into cabs that can't reproduce that content anyway... seems like a no brainer.

Getting back to the marketing aspect of it, I don't think there's a need to market it as a "feature" of the amp, because it's almost a necessity as part of the circuit optimization during design. But if you tell most bass players that you're intentionally chopping off the lowest part of their signal, you can bet that will raise a horrendous stink and turn a lot of people off, simply because the understanding of why you're doing it isn't there.
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Any amp/preamp that isn't DC-coupled will have high pass filtering in between gain stages because they couple stages with series capacitors. It's not hard to design those such that the rolloff frequency is very close to DC so they are often not useful as signal filters. I ran frequency response curves on my MB500 a few years ago and I think it's pretty rolled off by the time you get down to 20Hz. Can't remember exactly. Audiophiles love DC coupling but I honestly don't think it has a useful place in audio at all.
 
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#208
Taustin Powers said:
So I just looked at my speaker's specs (Eden 410 XLT), and the frequency response is 50Hz-14KHz.

After reading this thread, I would try setting my variable HPF (which I do not yet own) at around 50Hz, and then "follow my ear" from there?

Also, should I assume that an amp with a fixed 30Hz cutoff HPF would not be the ideal match?
Click to expand...
I wouldn't make that assumption, it depends on the filter alignment and slope.

For example, I typically use 4th order filters (24dB/octave) and somewhere between a Butterworth and Chebychev alignment (knee response). A 30Hz HPF will be -3dB at 3u0Hz and maybe -8dB at 25Hz (this is less than 25% of the average power compared with the average non high passed response.
 
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#210
agedhorse said:
I wouldn't make that assumption, it depends on the filter alignment and slope.

For example, I typically use 4th order filters (24dB/octave) and somewhere between a Butterworth and Chebychev alignment (knee response). A 30Hz HPF will be -3dB at 3u0Hz and maybe -8dB at 25Hz (this is less than 25% of the average power compared with the average non high passed response.
Click to expand...

As an example, these filters would behave very differently than the first order ones I'm using in my DI circuit. In my application, I don't want to overcomplicate the circuit so I'm sticking with very basic/gentle filters. If I was designing a mixing desk style HPF or one primarily aimed at speaker protection I would use an active filter implementation similar to what @agedhorse is describing here. Mine are gentle tone shapers.
 
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#211
K-2 said:
To be honest, I would really like to do that, but my experience with electronics is - soldered two wires 15 years ago...
On the other hand - I guess I think it is harder than it really is.
Still, will have to get some basic knowledge where to start.

But damn, thank you @Passinwind , this might be a kick that I needed to start something!
Click to expand...

There's quite a bit of good info to get you started in the TB Amps Forum FAQ: AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links

There are also many dedicated effects builders' forums online that cater to less experienced builders, and another great place to start is this website: Link Removed

And finally, a little bit of shameless self promotion: I have hopes that someone here will take the lead on an open source HPF project along these lines, which coincidentally happens to feature a variable LPF section, albeit in a different format from what we'd typically be talking about in this thread. I just may do that eventually if no one else steps up, but my plate is currently quite full and I still have a lot of fleshing out to do on the builder's WIKI for the current project.
 
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#212
agedhorse said:
I wouldn't make that assumption, it depends on the filter alignment and slope.

For example, I typically use 4th order filters (24dB/octave) and somewhere between a Butterworth and Chebychev alignment (knee response). A 30Hz HPF will be -3dB at 3u0Hz and maybe -8dB at 25Hz (this is less than 25% of the average power compared with the average non high passed response.
Click to expand...
I would also suspect that where one sets a HPF might differ slightly if the purpose is only speaker protection and/or amp headroom preservation versus as a re-voicing tool to either create an effect or deal with an acoustically challenging venue.
 
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#215
Studios with tube equipment used to filter to remove line hum. At Motown they used a 70Hz brick wall filter to deal with hum.

According to Bob Olhsson who worked at Motown:

At Motown we had passive high and low pass filters that we could patch in. In the newer studio, there were 18 dB/octave 40, 50, 60, 70, 80, 90, 100 and 150 Hz. high pass filters that were part of each of the mike preamps for tracking. I never saw that many filters elsewhere.

 
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#216
The last time I changed a tone or volume setting after sound check was also the first time, and the only time a sound person tried to kill me. :D
I learned early on that getting the sound person usable easy to work with signal is the key to sounding good live. That's why a PB HPF is such an attractive idea to me. One less problem if the sound person is new or non existent, plus better loud band mix at high volume with no PA.

Alas in France VAT and shipping are really a deterrent for the obvious choice Broughton Audio. 60 extra euros is a slap for a pedal. At that price I can look for a boutique shop.
I'll probably look for a French boutique pedal maker if I play live again this summer. If I find someone in Europe making them I'll post links here. Please do the same if you find one.
Thanks Y'all!
 
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#217
Bassbeater said:
If I find someone in Europe making them I'll post links here. Please do the same if you find one.
Thanks Y'all!
Click to expand...

As has already been mentioned: [sfx]:home

@Silent Fly is a Talkbass member, perhaps he would care to check in to this thread.
 
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