I have to be missing something (DIY HPF)

[chadface]

I started doing some research on building a DIY HPF and I must be missing something. It seems like this is way too simple....

I'm considering putting it in the effects loop of a Fender Bassman 100 combo. The manual says the effects send is 1kΩ. Using the RC High Pass Filter Calculator, I can use a 4.7uF capacitor to cut around 33hz.

So I can simply solder a $0.59 capacitor in the middle of a patch cable and join the HPF club? It sounds too easy.

 

[/\/\3phist0]

HPF-Pre, updated December 16, 2018 - hpftechllc

https://redirect.viglink.com/?key=1...9/?amp=1484445725&ref=https://www.google.com/

https://redirect.viglink.com/?key=1...9/?amp=1484445725&ref=https://www.google.com/

 

[Passinwind]

I started doing some research on building a DIY HPF and I must be missing something. It seems like this is way too simple....

I'm considering putting it in the effects loop of a Fender Bassman 100 combo. The manual says the effects send is 1kΩ. Using the RC High Pass Filter Calculator, I can use a 4.7uF capacitor to cut around 33hz.

So I can simply solder a $0.59 capacitor in the middle of a patch cable and join the HPF club? It sounds too easy.

Yep, there's no free lunch. First off, that's a 1st order filter and you typically want third or fourth order. And a higher order passive filter will be quite lossy, so an active solution is generally preferable. The schematic for the fDeck v3 linked above has a few features you can probably do away with for your application, but it'll give you a pretty good idea of what's actually necessary to "join the club."

 

[Stumbo]

Yep, there's no free lunch. First off, that's a 1st order filter and you typically want third or fourth order. And a higher order passive filter will be quite lossy, so an active solution is generally preferable. The schematic for the fDeck v3 linked above has a few features you can probably do away with for your application, but it'll give you a pretty good idea of what's actually necessary to "join the club."

Charlie knows his stuff.

 

[mmbongo]

Yeah not really that simple, but on the other hand if you do that you might make a DIY distortion pedal!

 

[Groove Doctor]

How hard can it be....?

 

[chadface]

Yep, there's no free lunch. First off, that's a 1st order filter and you typically want third or fourth order. And a higher order passive filter will be quite lossy, so an active solution is generally preferable. The schematic for the fDeck v3 linked above has a few features you can probably do away with for your application, but it'll give you a pretty good idea of what's actually necessary to "join the club."

Thank you so much! I appreciate someone with a brain helping an idiot like me out

 

[Passinwind]

Thank you so much! I appreciate someone with a brain helping an idiot like me out

Idiots don't tend to ask good questions like you did, at least in my experience. And the whole HPF thing is quite non-intuitive for a lot of people. Even though I've been using them for a very long time in other applications, and even for bass, when I included one in my first modern era bass amp build I still wasn't quite sure I was doing it right.

 

[Haroldo]

Thank you so much! I appreciate someone with a brain helping an idiot like me out

Dunno about the idiot part.....

Curiosity and willingness to learn go a very long way.

 

[silky smoove]

I think Fender voices their bass EQ at 80hz.

I believe their bass EQ is a shelving control rather than a bell, so it’s affecting everything from 80hz and below. I could be wrong though as Fender EQs have often been very unintuitive (ie 2-10-2 being flat on some models).

 

[Mushroo]

I believe their bass EQ is a shelving control rather than a bell, so it’s affecting everything from 80hz and below. I could be wrong though as Fender EQs have often been very unintuitive (ie 2-10-2 being flat on some models).

Theoretically I suppose you could make it more of a "bell" shape by boosting 0-80hz with the shelving Bass control, while also cutting below 33hz with a HPF?

 

[silky smoove]

Theoretically I suppose you could make it more of a "bell" shape by boosting 0-80hz with the shelving Bass control, while also cutting below 33hz with a HPF?

Yep. It would be a bell with a pretty wide Q.

 

[Passinwind]

Theoretically I suppose you could make it more of a "bell" shape by boosting 0-80hz with the shelving Bass control, while also cutting below 33hz with a HPF?

Yep, that's actually my favorite sort of application for a variable HPF. It's an old trick, Pultec EQs are one venerable example.

 

[Passinwind]

Yep. It would be a bell with a pretty wide Q.

Yep. Here's a model from one of my DIY amps, bass at 6/10 and HPF swept across its full range, which is roughly 25-120Hz:

And then bass control cranked to 10/10, HPF fully swept again:

 

[Jaygetsreal]

Invalid Link Removed
Variable HPF. Board or kit.
This supplier will post internationally and their service is excellent.

 

[Honkey tonk]

Invalid Link Removed

Cheap but do they do the same thing ?

 

[Haroldo]

Invalid Link Removed

Cheap but do they do the same thing ?

Nope. It'll only provide what's known as a "6 dB / Octave slope at the corner frequency". In this instance the corner frequency is fixed at 80 Hz. A good HPF will have a much steeper slope and usually a variable corner frequency. Particularly for speaker protection, the idea is to have as much of a signal decrease as possible as quickly (in terms of frequency) as possible. The car wants to stop hard and fast.

 

[SoulReflection]

Hey, this one is fun...

Why did you start playing bass?

Come on over. I would love to hear your stories...