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Filter Preamps - anyone compared ACG, Lusithand, Passinwind, Underhill?

Bump to an old thread, but if anyone is interested I have three basses arriving soon with different filter preamps.

Two four strings (one fretted, one fretless) with Turner Multicoils. One has the Lusithand NFP Special Mk II and one with the Underhill "The Full English".

The third bass has Nordstrand PolyVox pickups and the Underhill "Cali Dub" with a push/pull treble boost added.

I also owned a fretless for years that had the ACG EQ02. It was the first commercially available ACG/East preamp with a single filter.

And I owned two ACGs with the EQ03 preamps, one with Multicoils and one with the FB pickups.

I've played a few Wals, including recording an album with one owned by the studio, but that was over 20 years ago now.

If anyone is interested I can give my thoughts on any or all of these preamps.

@Jared Lash great to hear from you! Hope you're well. Your thoughts would be appreciated by many, I think.
 
@Jared Lash great to hear from you! Hope you're well. Your thoughts would be appreciated by many, I think.

Will do. The first to show up will be my fretless with the Underhill preamp. It ships out tomorrow.

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Bump to an old thread, but if anyone is interested I have three basses arriving soon with different filter preamps.

Two four strings (one fretted, one fretless) with Turner Multicoils. One has the Lusithand NFP Special Mk II and one with the Underhill "The Full English".

The third bass has Nordstrand PolyVox pickups and the Underhill "Cali Dub" with a push/pull treble boost added.

I also owned a fretless for years that had the ACG EQ02. It was the first commercially available ACG/East preamp with a single filter.

And I owned two ACGs with the EQ03 preamps, one with Multicoils and one with the FB pickups.

I've played a few Wals, including recording an album with one owned by the studio, but that was over 20 years ago now.

If anyone is interested I can give my thoughts on any or all of these preamps.

I would definitely appreciate hearing your impressions of the different preamps, and also how you think the PolyVox and Turner pickups compare. I have a lot of experience with Wal (and some with ACG), so I'd definitely like to know how the next generation of preamps and pickups stack up!
 
My first of the three basses with filter preamps is out for delivery, so I thought I'd start out with some of my existing thoughts on multicoils and filter preamps.

Wal bass: I've briefly played a fretted MkII but the majority of my experience was recording with a fretless Mk I. I absolutely loved the sound of that bass. It was boat anchor heavy and the slight v shaped neck to a little bit to get used to, but the sound was fantastic. Powerful, mid focused, and clear. Very horn-like IMO. The studio was willing to sell it, but I couldn't scrape together the money at the time. Now, it'd sell for probably 5-6 times as much. It had a slight grit to it, but not as much as I was expecting. Overall, when set relatively "flat" it had a naturally big, warm sound.

I say "flat" with quotations, because even with both tone knobs fully open the Wal seemed to roll off in the 3-4k range. And the pick attack was seemingly voiced significantly higher than that. So there were always some missing frequencies in the 4-7 k range which helped emphasize the mid focus of the bass.

Just for reference, I like Tool, but Justin Chancellor's sound has never been "the Wal tone" to me. My favorite has always been Flea on Blood Sugar Sex Magik, but I'm also a fan of Power Windows era Geddy, Bruce Thomas with Elvis Costello, Mick Karn, and Kristian Dunn from El Ten Eleven, who sounded massive with his Wal when I saw them live.

The ACG/East EQ02

The first bass I played with a filter preamp was my old Stambaugh fretless which had EMG Jazz pickups and an ACG/East EQ02. It's on the left here:

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That preamp had volume, blend, a high pass filter and a single low pass filter for both pickups with a control for resonance/overshoot peak.

This bass sounded amazing and the filter preamp was a huge part of that. It really let me dial in a deep, mid focused tone with some boost and then let in some highs to balance the sound. I still miss that bass.

The ACG/East EQ02 and ACG Multicoils

I loved the ACG EQ02 so much that it led me to getting a full ACG bass from Alan and then later a second one. The first was a multiscale 6 string that was a bit of an experiment for Alan and me. It had the ACG FB pickups and the 5 knob EQ03 with an added tone knob. It also looked amazing with flamed redwood top & back, a sycamore fingerboard, 7 piece (I think) neck etc. I unfortunately don't have any photos (they were in my long defunct Photobucket account) but it was a superbly crafted bass.

That bass was phenomenal. Rich, clear, and really piano like. It was hi-fi in the best sense of the term. The EQ03 was incredibly versatile. One low pass filter and resonance stack per pickup, a Treble stack with a HPF and gain control, a passive tone, and the bass stacks could even be pulled up for low mid and high mid boosts. It is a clean, clear and super flexible preamp that could create a HUGE range of tones.

In fact, the only issue I had with this preamp was that it was maybe TOO versatile. Even with the 41 detents on the LPF stacks it was very hard to quickly replicate amazing tones that I'd discover. Between the LPFs & resonance, Treble stack, passive tone and switchable mid boosts you could tweak for hours finding (and often losing) great sounds. Which is why Alan worked with John East on the DFM pre which keeps all the good stuff but limits the range of the LPF sweep to make it (I assume) easier to dial in.

After that ACG, Alan introduced his MC (Multicoil) pickups. Looking for more of a Wal tone, I had to have one. So I ordered a singlecut Finn 5. Here's the build thread for that bass. Neither the EQ03 nor the MC pickups were really an attempt to copy the Wal tone and I think Alan would say that himself. But customers kept asking for Multicoil pickups and so they were created through collaboration (like the other ACG pickups) with Aaron Armstrong. IIRC, the bridge has ceramic magnets and the neck alnico (or vice versa?) and the bridge pickup is given a bit more resonance via the electronics to make it more "bridge" sounding. @Skelf can correct me where I'm wrong, and I'm sure I am somewhere.

The pickups and filter preamp put that bass roughly in the same ballpark as a Wal, but it is really it's own thing. Less gritty and aggressive, more clean/refined and percussive. To get closer to a Wal you have to close the filters a fair amount because the ACG's filter have more Treble extension when fully open.

It was an awesome bass, and Alan is incredible to work with. I highly recommend him. For my tastes, I actually preferred the FB pickups. I believe they are sidewinder pickups where each coil uses the same blade to create a narrow aperture and make them more single coil like. Set flat the MC pickups had more "character" but the FBs (at least to me) were more of a blank canvas that allowed a HUGE range of sounds while the MCs felt like the filters were making tweaks to a baked in (but very cool) sound.

Assuming my bass shows up as scheduled today, I'll experiment with it and give my initial thoughts on how the Underhill preamp compares to the Wall and ACG and how the Turner multicoils compare to the Wal and ACG MC pickups.

Cheers.
 
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I look forward to your comparison. My only experience is my bordwell with Turner multicoils and an Underhill Cali Dub preamp. I have another set of Turners that have the brittish voicing and am going to swap them to compare. I love this bass and the tonal varieties, but like you Flea on BSSM is my favorite wal tone, and I'm not quite getting that with this set of pickups (I htink that is the problem). The other set would be more mid focused. I'll be swapping them after we move. Right now were buying and selling houses. It is a time suck and stressful.
 
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I look forward to your comparison. My only experience is my bordwell with Turner multicoils and an Underhill Cali Dub preamp. I have another set of Turners that have the brittish voicing and am going to swap them to compare. I love this bass and the tonal varieties, but like you Flea on BSSM is my favorite wal tone, and I'm not quite getting that with this set of pickups (I htink that is the problem). The other set would be more mid focused. I'll be swapping them after we move. Right now were buying and selling houses. It is a time suck and stressful.

FWIW, both sets of Turner multicoils I ordered have the "English" Voicing.
 
Initial thoughts on the Underhill preamp ("The Full English"):

When my new bass arrived there was no sound from the A string when rolled to the neck pickup. A quick email to @bowthing (and a VERY quick response) and things were sorted out. Just a loose connection that was quickly fixed. So before I even get into the sounds, I think it's worth pointing out that you'll get excellent customer service from Underhill.

As for the preamp, it's very Wal-like. The biggest differences are that it's not as inherently aggressive and that it has a lower noise floor. When wide open the filters have a bit higher cutoff frequency than Wals, but a slight twist of the filter knobs (to about 8.5 on my numbered knobs) gets me to about the same place.

I haven't adjusted the trimmers yet, but the Underhill gives the option to tweak the Q boost both with the knobs pushed in and with them pulled out. I think I'll bump the pushed in boost a touch and the pulled out boost a bit more.

The Underhill's treble boost is voiced at around the same frequency as the Wal "pick attack" but it seems a bit smoother to me and less ice picky. I'm not quite sure why. Maybe less gain? Or maybe it's a broader boost? That's not good or bad per se, just different, but on a fretelss I definitely prefer it.

I'll add more thoughts when the Lusithand NFP Special MkII arrives with my next bass.
 
When my new bass arrived there was no sound from the A string when rolled to the neck pickup. A quick email to @bowthing (and a VERY quick response) and things were sorted out. Just a loose connection that was quickly fixed. So before I even get into the sounds, I think it's worth pointing out that you'll get excellent customer service from Underhill.
The upside of that is you now have undeniable proof that it's a true multi-coil system!
 
The Underhill's treble boost is voiced at around the same frequency as the Wal "pick attack" but it seems a bit smoother to me and less ice picky. I'm not quite sure why. Maybe less gain? Or maybe it's a broader boost? That's not good or bad per se, just different, but on a fretelss I definitely prefer it.
The treble gain can be turned up another 3dB from the "factory" setting (or turned down, of course). Also, the treble signal has a blend trimmer on the blend module. The Wal circuit takes the treble signal from the neck pickup only, so if you pan the treble blend all the way to the neck, and turn up the gain, it should be very close to the same sound (it's the same filter under the hood).
 
The treble gain can be turned up another 3dB from the "factory" setting (or turned down, of course). Also, the treble signal has a blend trimmer on the blend module. The Wal circuit takes the treble signal from the neck pickup only, so if you pan the treble blend all the way to the neck, and turn up the gain, it should be very close to the same sound (it's the same filter under the hood).

I purposely haven't made any adjustments to the preamp yet. I want to make sure I have a very good feel for the bass as it is before I do too much tweaking. Especially since I put new strings on it and they haven't fully settled in yet. But I think I may slightly bump the gain on the treble and boost the pushed in Q very slightly for both filters and the pulled out Q a bit more.
 
Bass #2 arrived yesterday and it is fantastic.


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Stambwal2.jpg


Initial thoughts on the Lusithand vs the Underhill. The Lusithand has a bit more built in aggression. I'm not sure why. Maybe the filters aren't as wide and fully open they just extend into that low treble area? I'll have to compare the specs when time allows. But also, I had to dial back the attenuation pretty much all the way because my neanderthal right hand was forcing the preamp to clip until I did.

Both preamps are fantastic.
 
Bass #2 arrived yesterday and it is fantastic.


View attachment 7301923

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Initial thoughts on the Lusithand vs the Underhill. The Lusithand has a bit more built in aggression. I'm not sure why. Maybe the filters aren't as wide and fully open they just extend into that low treble area? I'll have to compare the specs when time allows. But also, I had to dial back the attenuation pretty much all the way because my neanderthal right hand was forcing the preamp to clip until I did.

Both preamps are fantastic.
The Lusithand is probably the most aggressive of the aftermarket filter pres I’ve tried. I don’t ever leave mine wide open so I don’t think it has to do with the available frequency range, though the 2-pickup model with the Attack boost option doesn’t go as high as the single pickup models (and I’ve only personally had the single pickup model). I’ve found mine to have pretty decent headroom at 9V (I’ve used one in an external pedal box with all sorts of different instruments going into it, both active and passive and rarely experienced obvious clipping though it is possible that some light clipping is part of what I like about them), but I believe they can safely be run at 18V too for more headroom of you need it.

I suspect some of these filters are using different topologies that give the potential for more mellow or more aggressive Q boost, and the implementation of a continuous Q boost control (on a pot) vs a Q-switch may have some effect as well. I’ve personally found the ACG filter pres to sound the most clean/polite of the ones I’ve tried even with the resonance maxed. They are still great pres though!
 
The Lusithand is probably the most aggressive of the aftermarket filter pres I’ve tried. I don’t ever leave mine wide open so I don’t think it has to do with the available frequency range, though the 2-pickup model with the Attack boost option doesn’t go as high as the single pickup models (and I’ve only personally had the single pickup model). I’ve found mine to have pretty decent headroom at 9V (I’ve used one in an external pedal box with all sorts of different instruments going into it, both active and passive and rarely experienced obvious clipping though it is possible that some light clipping is part of what I like about them), but I believe they can safely be run at 18V too for more headroom of you need it.

I suspect some of these filters are using different topologies that give the potential for more mellow or more aggressive Q boost, and the implementation of a continuous Q boost control (on a pot) vs a Q-switch may have some effect as well. I’ve personally found the ACG filter pres to sound the most clean/polite of the ones I’ve tried even with the resonance maxed. They are still great pres though!

Your experience largely matches mine. Even closing both filters a bit the Lusithand has an aggressive character. I love the East/ACG pre, but if there's a range from clean/polite to colored/aggressive for filter preamps the Lusithand and ACG are on opposite ends. Which isn't bad for either. My new bass sounds fantastic with the Turner Multicoils and Lusithand NFP Special Mk II, but it doesn't work for everything. The ACGs I've had (especially with the sidewinder humbuckers vs the multicoils) were much more chameleon-like and able to to fit in anywhere vs this bass and it's very distinct voice that works for some things incredibly well and for other things not at all.


As far as clipping I have a VERY heavy right hand on fretted basses. It probably wouldn't clip for most people. I've learned to play with much more feel (on guitar and fretless in particular) but my default is super aggressive.
 
Bass #2 arrived yesterday and it is fantastic.


View attachment 7301923

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Initial thoughts on the Lusithand vs the Underhill. The Lusithand has a bit more built in aggression. I'm not sure why. Maybe the filters aren't as wide and fully open they just extend into that low treble area? I'll have to compare the specs when time allows. But also, I had to dial back the attenuation pretty much all the way because my neanderthal right hand was forcing the preamp to clip until I did.

Both preamps are fantastic.

Taking a Quick Look at the specs, it seems that the frequency range on the Lusithand is 100hz - 2.5KHz (neck) and 200Hz 2.5KHz (bridge), while the Under hill is 130Hz - 5.3KHz. So, the Lusithand top frequency is a lot lower than the Underhill, which (to my mind) would put it more in that aggressive upper midrange/low treble area.
 
"The Full English" preamp from Underhill has a stock frequency range of 200-5300 Hz for both filters, but Tim tweaked the neck filter for me and it now goes from 135 Hz to 5000 Hz. So fully open they are definitely wider. But even if I roll back the Underhill filters to what sounds like the same frequencies of the Lusithand fully open the Lusithand is more aggressive to my ears.

But I've also got the Underhill in a fretless and the Lusithand in a fretted, not to mention they're built from different woods and have different strings. So it's not exactly an apples to apples comparison.

Having not tried either before I wasn't sure which one to put in which bass, but for what I want tone-wise each preamp is absolutely in the right bass. They both sound tremendous, but the wider, cleaner sound of the Underhill is perfect for the fretless tone I want and the more aggressive sound of the NFP Speciall Mk II gets me the clank I want in the fretted.
 
Final bass showed up yesterday.

MC5a.jpg
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This one has the Underhill "Cali Dub" filter preamp with an added FT module for a fixed treble boost when I pull up on the volume knob. The full controls are:

Volume (pull for treble boost at 4700 Hz. I believe it is factory set for 9 dB of boost but is adjustable from 0-13 dB)
Blend
Neck filter stack (200-5300 Hz filter with an adjustable resonance boost of 0-13 dB)
Bridge filter stack (200-5300 Hz filter with an adjustable resonance boost of 0-13 dB)
Bass control stack (lower ring sets frequency between 30-200 Hz, top ring boosts or cuts bass by 0-7.5 dB)
 
So for anyone curious, here are my thoughts on the Underhill Cali Dub preamp:

As I mentioned earlier I assumed it would be much closer to the ACG/East preamp than the Wal preamp, but once it got here I realized it's actually pretty similar to the Underhill "The Full English" preamp that's in my four string fretless. Which makes a lot of sense. @bowthing can correct me if I'm wrong, but they are the same filters in both preamps, with the only difference being that the Wal style (The Full English) preamp has a fixed Q boost on a push pull control and the Cali Dub has a variable boost.

Both are very low noise and super clean/transparent sounding. Of the two, The Full English is much easier/simpler to use and easy to dial in while the Cali Dub is significantly more versatile. The PolyVox pickups have a very distinct voice (very thick, clear, midrange heavy, and authoratative) but the filters and adjustable boosts allow you to revoice them significantly. And most interesting to me, the bass control is super useful to both boost AND cut bass. On most active basses I either leave the bass control flat or boost it. I almost never cut bass unless there's an acoustics issue. But with these pickups sculpting the bass to either add heft or lean out the tone can yield a lot of tones.

How would I compare it to the ACG? So I had an ACG EQ02 in an old Stambaugh fretless (just one filter for both pickups) and two ACGs that both had the EQ03 preamp. Both were very clear, hi-fi preamps. The ACG's treble control introduced a bit of hiss but otherwise it was very quiet. The Underhill is VERY low noise.

The ACG was hands down the most flexible preamp I've ever used. The filters were SUPER wide. I believe from 70 Hz to 7000 Hz with an adjustable 0-10 dB boost. It also had a high pass/treble control from 1.5k Hz to 10K Hz and a LOT of boost on tap (0-18 dB). And then there were fixed low and high mid boosts on a push/pull AND a passive tone knob.

It was infinitely tweak able. But that also made it difficult to recall specific tones. The filter knobs had 41 different clicks, but that was still too hard to keep track of. So while I absolutely loved that preamp, it wasn't all that easy to tweak on the fly. Alan seemed to agree, as soon after my builds he and John East released the DFM preamp which narrowed the range of the LPFs (from 70 Hz to 3.5 kHz), tweaked the treble control to be a mid/treble control (500 Hz to 5000 Hz) and added an attack boost at 8000 Hz. I think the Wal "Pick Attack" is at 7,000 Hz.
 
And finally, here's a general note I've found with filter based preamps and different pickups. I had an ACG Uber spec with the ACG/Armstrong multicoils, an ACG with a pair of Alan's FB pickups, and now my two pseudo Wals (Stambwals?) and my five string with the Poly Vox pickups and Cali Dub preamp.

What I've learned from this is that the ACG MC pickups and the Turner Multicoils have VERY distinct voices. Alan uses a "resonance board" to give the neck and bridge multicoils a bit more of a different tone from one another, but they are still fairly similar in tone and have a particular sound. Same thing with the Turner Multicoils. And that sound is awesome. But it means the filters can definitely sculpt the tone, but the pickups always have that characteristic voice.

On the other hand, the PolyVox are a bit more of a chameleon and can be tweaked for a wider variety of sounds.

But the MOST versatile setup for me was the ACG with the FB pickups and EQ03 preamp. Those FB pickups are sidewinders where both coils use the same steel blade running through the middle of the pickup. So it has a narrow aperture and a very clear, focused single coil type sound while being humcancelling. They are some of my favorite pickups ever. Very hi-fi in all the best ways. And being so clear and hi-fi, they worked amazingly with the filters to really sculpt the sound.

The Wal sound is the Wal sound and I absolutely love it. My Uber ACG was in the ballpark of a Wal, but with it's own distinct sound. My new bass and my old ACG with the FB pickups are/were more versatile and did their own thing. All just different flavors of awesome.
 

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