Wal and other filter-based preamps

[Snert]

That's a parametric EQ. Not the same thing and summing the two pickups onboard is not how the filter was designed or intended to be used by Alembic, and I assume Wal.

 

[Arjank]

That's a parametric EQ.

It can also LPF/HPF

Not the same thing and summing the two pickups onboard is not how the filter was designed or intended to be used by Alembic, and I assume Wal.

Agreed, but can be fixed by putting seperate outputs on your bass (the EQ2 is stereo and both channels can be programmed seperately)

 

[SteveCS]

That's a parametric EQ. Not the same thing and summing the two pickups onboard is not how the filter was designed or intended to be used by Alembic, and I assume Wal.

Indeed - the Wal filters, 1 per pickup, are applied before the blend/balance control. The Pick Attack is applied to the post-blend mix.

 

[Snert]

Indeed - the Wal filters, 1 per pickup, are applied before the blend/balance control.

So they're both standard non peaking (Q<=0.7 or so) LPFs?

The Pick Attack is applied to the post-blend mix.

Then there's a fixed frequency peak narrow band peaking EQ applied?

Never seen a Wal schematic, but that is contrary to some of what I've been told before. Unless I see a schematic or can do a measurement suite, I'm really not sure what to believe at this stage. No offence meant, but too much I've read is contradictory at this stage.

 

[SteveCS]

So they're both standard non peaking (Q<=0.7 or so) LPFs?

Then there's a fixed frequency peak narrow band peaking EQ applied?

Never seen a Wal schematic, but that is contrary to some of what I've been told before. Unless I see a schematic or can do a measurement suite, I'm really not sure what to believe at this stage. No offence meant, but too much I've read is contradictory at this stage.

Both filters have switchable resonant peaks via push/pull pots. The pick attack is push/pull on master volume and is a preset high frequency portion added in. I have a feeling it is siphoned off from the bridge pickup regardless of the selected blend, but can't recall for sure. The actual amount switched in is preset via a trimpot inside. I don't have a schematic but did play several back in the mid '80s and had conversations with Ian about it.

 

[garfoid]

There is also this one from Noll: NOLL TCM 3P Vpp/Bl - T/T - B/B - M/M - Best Bass Gear

I don't think this qualifies as on topic, but, it does look good.

 

[ctmullins]

I think having a dedicated filter for the neck pickup, with a conventional passive tone for the bridge with a conventional bass and 3-way selectable mid, I think, would be a really nice configuration.

That does sound delicious. I think I have the right units on hand to try that out; might have to break open the toolbox and get modding!!

Well I did it!

Or something similar at least.

I’ve been trying to find the right electronics for my homemade multiscale (the one that gave me fits during the build, still looks like crap close up, but is amazingly comfortable to play). It has a pair of Nordstrand Big Blades, Warm & Wooly, mounted in the traditional Rick positions. Fan is 32” - 34”. Strings are LaBella RX stainless rounds.

The original circuit was passive, with a selector switch and a 500kOhm master volume. Tone was good. The Nordstrands have an amazingly healthy output. But the overall tone was darker than I wanted.

Then I added a JTEX Distiller after the master volume. More flexibility, some good tones, but still too dark.

Then I replaced the Distiller with a John East BTB-01, a really nice, compact concentric two-band unit with some cool features: the bass control is boost-only, the treble control cuts at a lower frequency than it boosts, and it has a pull Bright for top-end sheen. This is a comfort zone for me, as I have these units in several other basses. Again, plenty of flexibility, but the overall tone was still too dark.

I realized that the passive mixing of the pickups with the selector switch was probably contributing to the dark tone, especially the middle position, where the insertion loss was sucking out a bunch of mids too. So I replaced the selector switch with a Richter MX2 active buffered blend, and replaced the 500kOhm master volume with a 25kOhm unit wired after everything else. Huge difference! Instead of losing mids in the center position, the active blend actually emphasized them, which was quite welcome! And having each pickup routed straight into its own buffer really helped preserve the treble frequencies. I was actually thinking of swapping out the W&W Big Blades for a pair of Clean & Clear, but the buffers made that unnecessary. Now we’re getting somewhere!

After a while I became dissatisfied with the taper of the active blend - it seemed like the middle 80% all sounded essentially the same, with either end sounding different, but either end also had less output than the middle section. Maybe that’s a quirk of the Richter? I don’t know. I don’t really like blend controls anyway.

So the final iteration, and the one that I think is a keeper, is this: the neck pickup is wired directly to the JTEX Distiller, the bridge pickup is wired straight to the East BTB-01, then those outputs go to the selector switch, then to the 25kOhm master volume. Holy Crap! This bass is an absolute beast now! Wiring each pickup straight to a buffer preserves so much high end, the neck pickup with the filter does all kinds of vintage and deep/dub tones, the bridge pickup with the East does all kinds of grindy and full rock tones, and running both together gets me that scooped pseudo-Jazz tone, but with loads of clarity and loads of output, and - this is the cool part - twiddling with the knobs lets me dial in the mids. With the East at a neutral setting, I can sweep the neck pickup through the filter and hear how it combines with the bridge going through the East. Since they’re both buffered, the two signals sum instead of cancel, and the filter emphasizes a certain band of mids - high mids, hi-mid mids, lo-mid mids, low mids, or deep dub lows. It’s a whole ton of fun!

Now I’m trying to come up with ways to independently buffer the two pickups on my other five-strings…

 

[sunbeast]

Well I did it!

Or something similar at least.

I’ve been trying to find the right electronics for my homemade multiscale (the one that gave me fits during the build, still looks like crap close up, but is amazingly comfortable to play). It has a pair of Nordstrand Big Blades, Warm & Wooly, mounted in the traditional Rick positions. Fan is 32” - 34”. Strings are LaBella RX stainless rounds.

The original circuit was passive, with a selector switch and a 500kOhm master volume. Tone was good. The Nordstrands have an amazingly healthy output. But the overall tone was darker than I wanted.

Then I added a JTEX Distiller after the master volume. More flexibility, some good tones, but still too dark.

Then I replaced the Distiller with a John East BTB-01, a really nice, compact concentric two-band unit with some cool features: the bass control is boost-only, the treble control cuts at a lower frequency than it boosts, and it has a pull Bright for top-end sheen. This is a comfort zone for me, as I have these units in several other basses. Again, plenty of flexibility, but the overall tone was still too dark.

I realized that the passive mixing of the pickups with the selector switch was probably contributing to the dark tone, especially the middle position, where the insertion loss was sucking out a bunch of mids too. So I replaced the selector switch with a Richter MX2 active buffered blend, and replaced the 500kOhm master volume with a 25kOhm unit wired after everything else. Huge difference! Instead of losing mids in the center position, the active blend actually emphasized them, which was quite welcome! And having each pickup routed straight into its own buffer really helped preserve the treble frequencies. I was actually thinking of swapping out the W&W Big Blades for a pair of Clean & Clear, but the buffers made that unnecessary. Now we’re getting somewhere!

After a while I became dissatisfied with the taper of the active blend - it seemed like the middle 80% all sounded essentially the same, with either end sounding different, but either end also had less output than the middle section. Maybe that’s a quirk of the Richter? I don’t know. I don’t really like blend controls anyway.

So the final iteration, and the one that I think is a keeper, is this: the neck pickup is wired directly to the JTEX Distiller, the bridge pickup is wired straight to the East BTB-01, then those outputs go to the selector switch, then to the 25kOhm master volume. Holy Crap! This bass is an absolute beast now! Wiring each pickup straight to a buffer preserves so much high end, the neck pickup with the filter does all kinds of vintage and deep/dub tones, the bridge pickup with the East does all kinds of grindy and full rock tones, and running both together gets me that scooped pseudo-Jazz tone, but with loads of clarity and loads of output, and - this is the cool part - twiddling with the knobs lets me dial in the mids. With the East at a neutral setting, I can sweep the neck pickup through the filter and hear how it combines with the bridge going through the East. Since they’re both buffered, the two signals sum instead of cancel, and the filter emphasizes a certain band of mids - high mids, hi-mid mids, lo-mid mids, low mids, or deep dub lows. It’s a whole ton of fun!

Now I’m trying to come up with ways to independently buffer the two pickups on my other five-strings…

Definitely with the J-Tex filter you’d want to put it before a volume control(s) in a passive bass if possible as it will act as a buffer and retain as much possible high-end that way (with volume control before it you are losing signal before you hit the preamp).

As far as a simple dual buffer, Bartolini makes the AGDB that you could place before volume controls to help minimize loading losses: Adjustable Gain Buffer - AGB & AGDB - Bartolini Pickups & Electronics

Or you could make your own: Buffer – IC | General Guitar Gadgets

 

[winegamd]

I'm running each pickup to its own passive tone (no load pots) into an AGDB, then into a 3 band Audere classic. Each pickup has a different value cap to tune the peak where I want it for each pickup. I have the neck with a .047uf and the bridge with a .015uf. There are so many tone options.

 

[winegamd]

Now technically you could put a tone styler on each tone pot in my set up and would sort of have dual passive high pass filters, they would just have a fixed peak. You could maybe put some resistors on switches for each tone pot and have switchable peak levels. But that's going to start to get to be a busy control layout.

 

[Jerry Catanescu]

Wiring a buffer/preamp straight after the pickup(s) and adding a low value volume pot (25k or even 10k) after the pre is the best way to go. Especially if you want to extract all the brightness you can out of your pickups. You can always dial it down if you want to, but it's hard to put it back in if you stifled it at the source by loading the pickups with pots straight across them. Pickup impedance is very frequency-dependent. It can easily peak at well over 100kOhm at a few kHz, and a 250k pot will load that down quite audibly.

 

[mrperkolator]

Buffering is cool, but man has this been a good read on filter preamps.

 

[jazzyvee]

Buffering is cool, but man has this been a good read on filter preamps.

I do use alembic filter basses and this thread has added to my understanding of filter based tone controls in general.
The alembics i have use filters that operate in the range 350Hz-6KHz. So for playing a lot of reggae, i can't push or emphasise the bottom end directly from the bass where I need to which is usually around 80 - 120Hz depending on the room. So I use an alembic superfilter as my preamp for those gigs which gives me access to control the lower frequencies and also band and high pass filtering if i need to.

 

[Chickenwheels]

I know for me I use filter on the bridge pickup and keep the neck pickup pretty much full range with no boost point. I blend the neck pickup in more when I want a fuller "conventional bass" sound and less for my usually snottyburpy tone.

Not far off what I do with my Wal.
Once you get the hang of filters, it’s incredible what you can achieve. But it’s a very different ball game.

 

[David Mochen]

Hi all, very nice and interesting thread. Just wanted to humbly show my take on a filter based preamp, with both variable frequency and resonance AND a treble boost via push-pull (a la "pick attack"). Currently working on a dual version. Cheers!

 

[Kinkh]

Sounds very nice!
Any chance of sharing a schematic to see how you did it? Or maybe telling which filter topology you used, or how you did the treble boost, etc. I'm all interested for the details of how people make these things

 

[David Mochen]

Sounds very nice!
Any chance of sharing a schematic to see how you did it? Or maybe telling which filter topology you used, or how you did the treble boost, etc. I'm all interested for the details of how people make these things

Thanks, Kinkh. I am making and selling these preamps as a small manufacturer here in Argentina. Basically it is a variable LPF with a very narrow BPF (treble) working in parallel and then both get into a mixer. LPF is always "on", whereas the BPF can be switched on and off, there is an internal trimmer for the gain of the treble boost as well.

Best,

 

[Clark Dark]

I have a ACG EQ-01 filter which is a concentric control that allows freq. variation but lately I have been looking at Lusithand because it's a tone filter that's more like Wal and Alembic.

 

[David Mochen]

Sounds very nice!
Any chance of sharing a schematic to see how you did it? Or maybe telling which filter topology you used, or how you did the treble boost, etc. I'm all interested for the details of how people make these things

BTW, I am using a Sallen Key implementation rather than a SVF for economy. Similar, yet different to what @Passinwind has implemented in his design (which I find great, stumbled upon it after having designed my own Filtrum 1 preamp shown in the video).

 

[pbass888]

I have a ACG EQ-01 filter which is a concentric control that allows freq. variation but lately I have been looking at Lusithand because it's a tone filter that's more like Wal and Alembic.

About 20 Years ago I was lucky enough to be in the UK and try two Wal basses (both fretless) . I got to use one wal mk2 (?I think)fretless for a set for one show for a fusion project I was involved with.

During the pandemic I put together a fretless warmoth and used the lusithand filter below for really pleasant tones that I remember from those basses . Perhaps not a complete wal tone but pretty close to the “Wal-ish “ sounds that I remember .

The pre I added to a fretless bass with lollar blade style jazz pickups (lo pass filter)
Lusithand Single NFP Preamp - Best Bass Gear