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fdecks HPF, Part II

#721
a bit of confusion for me re HPF configuration/use. Maybe some of you more experienced users can help me out.
I generally understand that an HPF limits/cuts frequencies below a certain setting.
FDecks v3 HPF is more or less a 2 band HPF .. with a fixed freq as well as a user selectable freq point.

But if the HPF is in line between the bass and the amp, isn't it just cutting the low low end from your bass signal as opposed to doing that in the preamp section of the amp ?

And then, what about user adjustable HPF built into an amp like the Mesa Subway 800+. Do these just cut the frequencies the amp will reproduce/amplify or are they somehow way up front in the circuit path so they just cut the low low frequencies coming from the input/bass ?

kind of confused, but still interested
 
#722
pfschim said:
a bit of confusion for me re HPF configuration/use. Maybe some of you more experienced users can help me out.
I generally understand that an HPF limits/cuts frequencies below a certain setting.
FDecks v3 HPF is more or less a 2 band HPF .. with a fixed freq as well as a user selectable freq point.

But if the HPF is in line between the bass and the amp, isn't it just cutting the low low end from your bass signal as opposed to doing that in the preamp section of the amp ?

And then, what about user adjustable HPF built into an amp like the Mesa Subway 800+. Do these just cut the frequencies the amp will reproduce/amplify or are they somehow way up front in the circuit path so they just cut the low low frequencies coming from the input/bass ?

kind of confused, but still interested
Click to expand...
My FDeck is in the FX loop, so it cuts the frequencies after the preamp. You can put it wherever you'd like.
 
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#724
pfschim said:
a bit of confusion for me re HPF configuration/use. Maybe some of you more experienced users can help me out.
I generally understand that an HPF limits/cuts frequencies below a certain setting.
FDecks v3 HPF is more or less a 2 band HPF .. with a fixed freq as well as a user selectable freq point.

But if the HPF is in line between the bass and the amp, isn't it just cutting the low low end from your bass signal as opposed to doing that in the preamp section of the amp ?

And then, what about user adjustable HPF built into an amp like the Mesa Subway 800+. Do these just cut the frequencies the amp will reproduce/amplify or are they somehow way up front in the circuit path so they just cut the low low frequencies coming from the input/bass ?

kind of confused, but still interested
Click to expand...
Add to this, a lot of bass amps already have a fixed HPF built in, like the Genz Benz Shuttle series. When you add an outboard, HPF device, you are doing what Agedhorse described as " cascading ". Long story short, you may not be getting the results you think, or want. I own the Subway 800+, which has a changeable HPF, initially set at 30 hz, ( like the Fdeck ). I also own an Fdeck. I tried using the Fdeck in between the bass, and in the effects loop, in my Shuttle, without noticing much difference. Then I was told that my amp, ( Shuttle 6.2 ), already had a fixed HPF built in. It gets confusing.
 
#725
kleinenenten said:
My FDeck is in the FX loop, so it cuts the frequencies after the preamp. You can put it wherever you'd like.
Click to expand...
good insight, thanks.
this makes more sense to me - cutting the sub 30hz info from the preamp - rather than simply cutting/significantly reducing the low frequencies coming from your bass. It makes total sense to me to keep useless frequencies (i.e. 30hz and below) out of the amplification process to save the amps power for those frequencies that we really want and our cabs can actually meaningfully reproduce.

I am not a tech by any means, and I have not measured how much sub 30hz signal info actually comes from any of my 4 string basses.
I would guess its not very much, but I could be totally wrong about that.
 
Last edited:
#726
pfschim said:
... I have not measured how much sub 30hz signal info actually comes from any of my 4 string basses.
I would guess its not very much, but I could be totally wrong about that.
Click to expand...
There can be a surprising amount, depending on your playing style. A strong attack on a note can have a lot of subsonic content. Thump on your lowest string while damping it with your fretting hand, and watch your speaker cones, you'll probably see a huge excursion (assuming your amp doesn't already filter this out). Given a serious subwoofer and a lot of power you might be able to feel it, but usually it just wastes amp headroom without any musical benefit.
 
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#727
pfschim said:
good insight, thanks.
this makes more sense to me - cutting the sub 30hz info from the preamp - rather than simply cutting/significantly reducing the low frequencies coming from your bass. It makes total sense to me to keep useless frequencies (i.e. 30hz and below) out of the amplification process to save the amps power for those frequencies that we really want and our cabs can actually meaningfully reproduce.

I am not a tech by any means, and I have not measured how much sub 30hz signal info actually comes from any of my 4 string basses.
I would guess its not very much, but I could be totally wrong about that.
Click to expand...
First, I'm not sure you'll find any full range bass cab manufacturer who will tell you that you need (or really want) frequencies below 30-35Hz going to their cabs - IME some even focus their strongest, most prominent low end voicing in the 60-80 Hz range with less concern about capability below that.

My experience with the HPF-Pre Series 3 includes use in the effects loop on my SWR SM400S and between the bass and regular input on a number of more recent amp designs including GK MB's, Mesa Carbines, Walkabout and D-800, and an Aguilar TH500.

For starters, I recognize that the SWR literally needs the HPF and the results there were excellent - old SWR owners/users know exactly what I mean. When I tried the HPF in the effects loop and then between the bass and regular input I couldn't tell any difference - which doesn't mean there wasn't any.

The Carbines and to some extent MBs sounded much better, specifically tighter and more focused with it. It helped the Walkabout bloom a bit less and actually felt like I had more headroom. On the D-800 the HPF really helped me get dialed in when playing in a huge aircraft museum that was built like a hangar. In these applications I only used the HPF between the bass and regular input on these heads.

The TH500 has the drive control and it is essentially a HPF/LPF combination voicing control that gets you a more vintage sealed cab voicing (and yes I know I oversimplified that). With the drive control off, I found the HPF to be nice in terms of tightening the low end while leaving my upper register (which isn't exactly crispy or sparkling to begin with) alone.

At the end of the day I really couldn't tell a lot of difference between effects loop and regular input placement. While the D-800 has a built-in 30 Hz HPF, the additional variable HPF didn't seem to affect anything adversely. In fact it really helped me deal with too much low bass in an acoustically challenging room where EQ alone couldn't get the job done. When you think about it, having two HPF's shouldn't be any more of a challenge than having multiple EQ's (on your bass, pre-amps, effects pedals, head preamp, etc.) in a typical set-up. There will be times when you get some unwanted artifacts/side-effects, but to me it's not a lot different than being aware of what you're doing when you start layering voicing/EQ controls on top of each other...which most of us do even without complex pedal boards.
 
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#728
Al Kraft said:
First, I'm not sure you'll find any full range bass cab manufacturer who will tell you that you need (or really want) frequencies below 30-35Hz going to their cabs - IME some even focus their strongest, most prominent low end voicing in the 60-80 Hz range with less concern about capability below that.

My experience with the HPF-Pre Series 3 includes use in the effects loop on my SWR SM400S and between the bass and regular input on a number of more recent amp designs including GK MB's, Mesa Carbines, Walkabout and D-800, and an Aguilar TH500.

For starters, I recognize that the SWR literally needs the HPF and the results there were excellent - old SWR owners/users know exactly what I mean. When I tried the HPF in the effects loop and then between the bass and regular input I couldn't tell any difference - which doesn't mean there wasn't any.

The Carbines and to some extent MBs sounded much better, specifically tighter and more focused with it. It helped the Walkabout bloom a bit less and actually felt like I had more headroom. On the D-800 the HPF really helped me get dialed in when playing in a huge aircraft museum that was built like a hangar. In these applications I only used the HPF between the bass and regular input on these heads.

The TH500 has the drive control and it is essentially a HPF/LPF combination voicing control that gets you a more vintage sealed cab voicing (and yes I know I oversimplified that). With the drive control off, I found the HPF to be nice in terms of tightening the low end while leaving my upper register (which isn't exactly crispy or sparkling to begin with) alone.

At the end of the day I really couldn't tell a lot of difference between effects loop and regular input placement. While the D-800 has a built-in 30 Hz HPF, the additional variable HPF didn't seem to affect anything adversely. In fact it really helped me deal with too much low bass in an acoustically challenging room where EQ alone couldn't get the job done. When you think about it, having two HPF's shouldn't be any more of a challenge than having multiple EQ's (on your bass, pre-amps, effects pedals, head preamp, etc.) in a typical set-up. There will be times when you get some unwanted artifacts/side-effects, but to me it's not a lot different than being aware of what you're doing when you start layering voicing/EQ controls on top of each other...which most of us do even without complex pedal boards.
Click to expand...
thanks Al, I think we are in agreement re cab frequency handling.
I have used parametric EQ to cut lows in the past (with my Walkabout for example). I know it's not quite the same, but its similar in concept.
I have toyed with picking up an Fdeck v3 but other stuff usually comes first
 
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#729
pfschim said:
thanks Al, I think we are in agreement re cab frequency handling.
I have used parametric EQ to cut lows in the past (with my Walkabout for example). I know it's not quite the same, but its similar in concept.
I have toyed with picking up an Fdeck v3 but other stuff usually comes first
Click to expand...
I own way too much gear, but the one thing I would never give up is the HPF-Pre Series 3 (and I actually own two of them - one is with my Mesa big-rig/big show gear bag and one is in my general gig bag). As an engineer I intuitively knew it would be useful, but I've been surprised at just how useful in terms of voicing and dealing with acoustically challenging venues. Best money I ever spent, and TB'er fdeck builds a very nice product that I would have been willing to pay more for.
 
#731
gregmon79 said:
fdk.jpg
Just wondering if he's been gone for a while or not.
Click to expand...
 
#733
On an amp like the MB200, where there is no effects loop, the only application would be to plug the bass into the HPF, and then into the amp, correct? ... I guess I don't understand the pre-amp portion of the HPF, if my only interest is to high pass the low frequencies? thanks in advance ..
 
#735
tjh said:
On an amp like the MB200, where there is no effects loop, the only application would be to plug the bass into the HPF, and then into the amp, correct? ... I guess I don't understand the pre-amp portion of the HPF, if my only interest is to high pass the low frequencies? thanks in advance ..
Click to expand...

Yeah I plug mine in last right before my amp as well. There it catches anything that can be an issue. And I use mine as a straight HPF, not as a preamp. That's how I treat it anyway.
 
#740
tjh said:
On an amp like the MB200, where there is no effects loop, the only application would be to plug the bass into the HPF, and then into the amp, correct? ... I guess I don't understand the pre-amp portion of the HPF, if my only interest is to high pass the low frequencies? thanks in advance ..
Click to expand...

It is called a preamp primarily relating to piezo equipped (upright) basses where it helps match impedences with an amp.(?)
 
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