High pass before Power amp

[gregoire1]

I was lurking here this morning and read a thread about a very cool preamp someone had made with an integrated high pass filter (I think it was called Thumper?), and thought, "what a great idea, eliminate excursion probs with your cab AND add headroom to your amp!" "Why haven't I heard of this before!"

So, now the thread has vanished, but I think it was a UK product offered by a TBer here. My question is, can I make a high-pass filter like this myself to go BEFORE the power amp? (I do own a soldering iron but no very little about electronics).

Does anyone know what that thing was called? And are there any similar products available in the U.S.?

[Whisper]

While this doesn't directly answer your question, many power amps have a HPF that can be switched on.

[gregoire1]

Originally Posted by Whisper

While this doesn't directly answer your question, many power amps have a HPF that can be switched on.

I guess my vintage Peavey M3000 doesn't. It just has one BIG knob on front.

[bongomania]

The thread hasn't vanished, you just have to look for the right word: "Thumpinator". Yes you could make your own, but doing it well is a whole 'nother question, and that's why I recommend buying one that is already known to be well-designed and well-made.

[gregoire1]

Originally Posted by bongomania

The thread hasn't vanished, you just have to look for the right word: "Thumpinator". Yes you could make your own, but doing it well is a whole 'nother question, and that's why I recommend buying one that is already known to be well-designed and well-made.

Ahhhh Thumpinator!

[aBoMoFo]

Some preamps have this lil' feature built into it as well. Sometimes they will be referred to as "Rumble Filters".

[bongomania]

True, but bear in mind that most rumble filters start their cutoff at 50, 80, or 120 Hz.

[Pat C.]

I run a high-pass at 32hz, but it's built into the PIP card in my Crown power amp. Before I had the Crown I ran a Rane Parametric EQ between my pre and power amp, set the lowest band for shelving and dumped everything below 25hz or so. There are a couple of those Ranes on Ebay right now: here and here. (Not my auctions)

As far as building a high-pass for use before the power amp, I'm sure it could be done. I personally wouldn't attempt it without having some knowledge of electronics, though.

Originally Posted by gregoire1

I was lurking here this morning and read a thread about a very cool preamp someone had made with an integrated high pass filter (I think it was called Thumper?), and thought, "what a great idea, eliminate excursion probs with your cab AND add headroom to your amp!" "Why haven't I heard of this before!"

So, now the thread has vanished, but I think it was a UK product offered by a TBer here. My question is, can I make a high-pass filter like this myself to go BEFORE the power amp? (I do own a soldering iron but no very little about electronics).

Does anyone know what that thing was called? And are there any similar products available in the U.S.?

[steveksux]

http://www.amazon.com/FMOD-Crossover.../dp/B0006N41BU
Here's a cheap alternative I've used before. Need some adapters to get the connections made.

Randy

[yamaha]

I used to have a 31 band EQ with a variable low cut filter before my poweramp. Worked great as a shelf, and could Isolate an unwanted resonnant frequency in specific rooms.

[aBoMoFo]

Originally Posted by bongomania

True, but bear in mind that most rumble filters start their cutoff at 50, 80, or 120 Hz.

Ah, yup you are right. On my lil' SWR Grand Prix the cutoff is at 30Hz which I don't mind loosing in higher power situations to save the cab from too much effort with too little payout (I use a 6x10). If that was up above 50Hz or higher I would think twice about this approach though.

[remo]

or just whack one of these inline (as I used to when I ran a pre-power setup).

http://store.hlabs.com/pk4/store.pl?view_product=13

[bongomania]

12 dB/octave is way too shallow of a slope to be effective in this application.

[gregoire1]

since those products aren't effective, is there a simple, in-line product (like the mini-thumpinator) available in the U.S.? Oh, it has to be cheap too, I wish I could just solder a capacitor (or inductor) somewhere but apparently that isn't realistic.

[BassmanPaul]

If you can build SS electronics it's a simple thing to do. One dual OP-amp is all you need + a handful of components.

http://sound.westhost.com/project99.htm

Paul

[aborgman]

Originally Posted by bongomania

12 dB/octave is way too shallow of a slope to be effective in this application.

Define "effective"...

They won't prevent as MUCH wasted energy/over excursion as a steeper filter, but they will help.

If you're talking the 30Hz filter, it's probably -3dB at 30Hz and -12dB at 15Hz.

That is half as much power at 30Hz, and ~1/10th as much power at 20Hz.

[rpsands]

The problem is if you're -3db @ 30hz and you turn up the bass SHELVING +6db on your preamp, you're at a net of +3db @ 30hz if your pre does not have some sort of shelving...which most of them don't seem to (maybe 20hz or so).

The problem is those shelving eq's on most preamps, combined with too shallow a slope.

[bongomania]

Originally Posted by gregoire1

since those products aren't effective, is there a simple, in-line product (like the mini-thumpinator) available in the U.S.? Oh, it has to be cheap too, I wish I could just solder a capacitor (or inductor) somewhere but apparently that isn't realistic.

Is the Thumpinator too expensive for you? (Be honest.) Because he ships to US customers all the time, if your concern is really about whether it's available in the US. If it's too expensive, that's a legitimate issue for you.

[UncleFluffy]

DIY calculator:

http://www.beis.de/Elektronik/Filter...eHPFilter.html

Pick your filter type, cut-off frequency and number of stages.

[bongomania]

Oh, and : FS: PFMOD low-cut (highpass) filter for speaker protection
Two 12 dB/oct filters in series.