SF-2 Superfilter questions

[djmay]

I currently use the SF-2 as a preamplifier in mono mode. I have had the unit for many years. I have read the manual and looked at the diagrams, however, I am unclear on how the filter affects the bass direct signal. My questions follow.

1. I use the HPF at about 80hz to limit the frequencies that get sent to the amplifier and speakers, as well as for the nice sound. I have had the direct gain at 0 because I thought that turning up the direct gain would add uncut frequencies to the signal. Is this how it works, or am I mistaken? It would be nice to keep the direct sound of the bass.
2. Related to 1 above, I am thinking about using the filters in series (stereo mode with a jumper output A to input B). I would use CH A for low pass or band pass, with direct gain up and CH B for high pass with direct gain at 0.
3. In general, how is filters in series different than filters in parallel?

I appreciate any help in understanding this.

[jazzyvee]

Check out this these threads in FAQ
https://club.alembic.com/index.php?topic=295.0

Read Dave Houck's entry as that sounds like what you are trying to do.

[djmay]

Either my unit is not functioning or I cannot have Direct Gain on only one channel in stereo mode series operation. That is that Channel B is filtering the output of Channel A.

When in stereo mode, each works as expected independently.
When I jumper CH A Out to CH B In,
1. there is no sound on Filter A unless Direct Gain B or Filter Gain B is up. Neither Direct Gain A nor Filter Gain A produce any sound independently.
2. there is no sound on Filter B unless Direct Gain A or Filter Gain A is up. Neither Direct Gain B nor Filter Gain B produce any sound independently.

Another possibility is that this is intended operation in a counterintuitive way, but I am confused as to which channel is affected by the Direct Gain control.
If I have the HPF on Channel B, I turn up Direct Gain on Channel A. This works, but I do not know if the HPF is filtering out the frequencies from Direct Gain A. This is important to keep the amp and speakers from dealing with unwanted frequencies.

I would be surprised if I am the first person that has tried this. I hope someone from Alembic is reading this.

[jazzyvee]

Try this.

plug into the front, set the mode switch to mono, then take output B to your power amp. Set the two channels the way you want keep the input gain  A to full and adjust the others to taste. That's how i used to run mine as a stand alone preamp.

[djmay]

Try this.

plug into the front, set the mode switch to mono, then take output B to your power amp. Set the two channels the way you want keep the input gain  A to full and adjust the others to taste. That's how i used to run mine as a stand alone preamp.

That is how I currently do it, except with direct gain at 0. I do not want very low frequencies hitting the amp. It is a cleaner sound and preserves power for the amp and speakers. I was hoping the series configuration would allow direct gain on the first filter and no direct gain on the second (hpf). I will try the series configuration at my next big band rehearsal and see if the amp and speakers are working harder.

[StephenR]

I use mine in mono, have never tried in series mode or as a standalone preamp. For mono I run from either the sidechain or effects loop on my preamp into the channel A input in the back then out from channel B to the sidechain or effects return.  In mono the direct gain for channel A has to be used since it supplies the raw signal. I set channel A mode to low-pass, and adjust frequency and damping to taste. Channel B is set to band-pass and then I adjust the frequency and damping. In this mode if you leave the channel B direct gain on zero you will only send the filtered signal to your preamp/amp (in mono of course). If you want to add the direct sound of the bass to the output you turn up the channel B direct gain to control the amount.

There seems to be no right or wrong way to use the SF-2 but there are a lot of options. Try setting it up the way I described, set the filters the way you like but leave the channel B gain at zero and you should only hear the filtered signal. If you are not using an effects loop with your SF-2 plug your bass directly in the rear input not the front and it should still work the way I described.

[jazzyvee]

I hope you find  satisfactory setup. 👍🏾🎶🎵

[djmay]

There seems to be no right or wrong way to use the SF-2 but there are a lot of options. Try setting it up the way I described, set the filters the way you like but leave the channel B gain at zero and you should only hear the filtered signal. If you are not using an effects loop with your SF-2 plug your bass directly in the rear input not the front and it should still work the way I described.

I use it in mono now . I am trying to find a way to add the raw signal without the low frequencies. I can add an external hpf, however I prefer to minimize the gear.

[cntrabssn]

When in stereo mode, each works as expected independently.
When I jumper CH A Out to CH B In,
1. there is no sound on Filter A unless Direct Gain B or Filter Gain B is up. Neither Direct Gain A nor Filter Gain A produce any sound independently.
2. there is no sound on Filter B unless Direct Gain A or Filter Gain A is up. Neither Direct Gain B nor Filter Gain B produce any sound independently.

It's been a while since I've used my Superfilter, but I'll take a stab at this one. I'm pretty sure I got it right, and you won't hurt anything.
The behavior you described is correct. Since everything is in series, there won't be a way to operate the two filter sections independently.

Based on what I think you're after, try setting things as follows in series mode:
Direct Gain A: This would be the dry (unfiltered) sent to input B. Set it to "0".
Filter Gain A: This will set the level of the (high-pass) filtered signal you send to input B. You don't want to risk over-driving the channel B input, so try setting this to "5" or so.

Keep channel A set this way, making minor adjustments for Output A -> input B level if needed.

Since everything is in series, Output B becomes your main output. Output B will be the mix of Direct Gain B and Filter Gain B. Try the following:
Direct gain B: This becomes your new "dry" signal level, which is just the high-pass filtered signal from "A" in your case. Set it to taste.
Filter Gain B: This is your total (i.e. series) filtered signal level, think of it as HPF + (x)PFb, where "x" is the mode of filter B. Set it to taste.

So by changing the Direct and Filter B control settings, you can have no output, all HPF, all "HPF + (x)PFb", or a mix. And for an added twist, if you set Direct A to "10" and Filter A to "0", you can disable your input HPF.

I hope this helps. If not, I'll delete this post in a hurry!
-nate.

[djmay]

When in stereo mode, each works as expected independently.
When I jumper CH A Out to CH B In,
1. there is no sound on Filter A unless Direct Gain B or Filter Gain B is up. Neither Direct Gain A nor Filter Gain A produce any sound independently.
2. there is no sound on Filter B unless Direct Gain A or Filter Gain A is up. Neither Direct Gain B nor Filter Gain B produce any sound independently.

It's been a while since I've used my Superfilter, but I'll take a stab at this one. I'm pretty sure I got it right, and you won't hurt anything.
The behavior you described is correct. Since everything is in series, there won't be a way to operate the two filter sections independently.

Based on what I think you're after, try setting things as follows in series mode:
Direct Gain A: This would be the dry (unfiltered) sent to input B. Set it to "0".
Filter Gain A: This will set the level of the (high-pass) filtered signal you send to input B. You don't want to risk over-driving the channel B input, so try setting this to "5" or so.

Keep channel A set this way, making minor adjustments for Output A -> input B level if needed.

Since everything is in series, Output B becomes your main output. Output B will be the mix of Direct Gain B and Filter Gain B. Try the following:
Direct gain B: This becomes your new "dry" signal level, which is just the high-pass filtered signal from "A" in your case. Set it to taste.
Filter Gain B: This is your total (i.e. series) filtered signal level, think of it as HPF + (x)PFb, where "x" is the mode of filter B. Set it to taste.

So by changing the Direct and Filter B control settings, you can have no output, all HPF, all "HPF + (x)PFb", or a mix. And for an added twist, if you set Direct A to "10" and Filter A to "0", you can disable your input HPF.

I hope this helps. If not, I'll delete this post in a hurry!
-nate.

Thank you! Your explanation makes sense. However, if I want dry bass signal included, I need Direct Gain A up and HPF on Filter B, which then cuts the low frequencies. If I have Direct Gain A at 0, there would be no dry bass signal in the chain.

The SF-2 is a really nice device.

[cntrabssn]

What you described is not much different than using a single channel in HPF mode with the Direct Gain set to "0". But I think (i.e. hope) I now have a
better understanding of what you want to do.

I was thinking about running the HPF first in the chain, then doing additional filtering later. But that won't provide the overall low frequency protection you're
looking for. Sorry about that.

So (still running channels in series)...

Try keeping channel B in high-pass mode, with Direct Gain B set to "0". That gives you the low frequency cut at the end of the chain.
Then you can use Direct Gain A and Filter Gain A to provide a mix of dry and filtered (LP, BP, or even HP) signal as desired to input B. Filter Gain B would be your usual master output. You probably won't want to turn up Direct Gain B, but I think you know what you'll get if you try it.

[djmay]

What you described is not much different than using a single channel in HPF mode with the Direct Gain set to "0". But I think (i.e. hope) I now have a
better understanding of what you want to do.

I was thinking about running the HPF first in the chain, then doing additional filtering later. But that won't provide the overall low frequency protection you're
looking for. Sorry about that.

So (still running channels in series)...

Try keeping channel B in high-pass mode, with Direct Gain B set to "0". That gives you the low frequency cut at the end of the chain.
Then you can use Direct Gain A and Filter Gain A to provide a mix of dry and filtered (LP, BP, or even HP) signal as desired to input B. Filter Gain B would be your usual master output. You probably won't want to turn up Direct Gain B, but I think you know what you'll get if you try it.

Yes, that is my intent. Use Channel A filter for band pass or low pass. Thanks again.

[rv_bass]

This is how I set my SF-2, low pass on the first band and high pass on the second.  In this photo I am using the F-1X with it, not the F-2B. 

[lbpesq]

Do you place the SF-2 before or after the F1-X?

Bill, tgo

[rv_bass]

After the F-1X, but Big Brown and Mission Control both have one channel of an SF-2 for each pickup that then went into an F-2B, so next time I use it I will try the SF-2 before the F-1X or F-2B.