Charlie, @Passinwind, could for the right price I'm sure. His open source pre can be configured in many ways as well.
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Wal and other filter-based preamps
- Thread starter burgerdj
- Start date
I’m still working it out.
Essentially, the very nearest clone to Wal preamps are the Lusithand ones, at least IMO.
However, Nuno will not consider a pick attack (treble boost) switch for now, and he has tweaked his range of frequencies for the filter preamp as a result. It works, but clearly his own pre now as opposed to something closer to the original Wal.
I also wonder if the Wal has a master HPF in operation cutting some of the lows in its design. Not something I have seen mentioned before. I’m still working it out.
@Passinwind is already following my thread over on Basschat about the ‘Wal-ish’. I’m just planning ahead a little as I contemplate trying to have something that may be closer to the Wal than even what Nuno is making at Lusithand.
The pick attack switch, according to what I see when I borrowed a Wal and looked at the output with a frequency analyser, appears to give a band pass frequency boost centred around 6kHz of 5-6 dB. It sounds great. And it compensates for the fact that the low pass filters in the circuit seem to cut off around 2.5 - 3.0 kHz.
The state variable filter design of the circuit, for that is what it appears to be, seems to allow a lot of flexibility. I’m not hugely au fait with it but that is what a friend who is looking at it says the design is.
Filters, onboard instruments themselves, or on the amp or a rack mount device like Alembic's SuperFilter, I think are too different for most people. We see them now in amps and preamps for shaving the 20 and 30hz off the bottom of bass guitar rigs, but you can do a lot more than that with other options.
I got very used to them on my Alembics and while you dial in a perfectly wonderful tone, you're essentially leaving big tone changes to the amp, which is not a bad thing. Alembic 'gave in' and offers a cut boost treble and bass circuit for those that just have to have it, but to me, that's like one of those Jaguars with a Chevy V8 transplant.
For guys that have never used them or been around a bass that runs them, it occurs to me the closest equivalent in a way would be the 'cut only' graphic EQ's you sometimes see in recording studios or serious FOH sound reinforcement.
As an adjunct to pickups like Alembic or Wal and a few others use, it's by far the cleanest and most honest tone off a bass guitar there is. Period.
I got very used to them on my Alembics and while you dial in a perfectly wonderful tone, you're essentially leaving big tone changes to the amp, which is not a bad thing. Alembic 'gave in' and offers a cut boost treble and bass circuit for those that just have to have it, but to me, that's like one of those Jaguars with a Chevy V8 transplant.
For guys that have never used them or been around a bass that runs them, it occurs to me the closest equivalent in a way would be the 'cut only' graphic EQ's you sometimes see in recording studios or serious FOH sound reinforcement.
As an adjunct to pickups like Alembic or Wal and a few others use, it's by far the cleanest and most honest tone off a bass guitar there is. Period.
I know what an SVF is and how it works. I just wanted to find out if the 'pick attack' was something more than the LPF of the filter being set for high Q or if it was something more exotic.
You mean reliable, doesn't leak and weighs several hundred ponds less?
So true in many respects. Although, I will disagree about the cut/boost bass and treble circuits. I can see how they might be wanted. Especially as they are generally easily available in nearly all active instruments...
The big factor in my view is the range of frequencies chosen for the individual pickup low pass filters. You can end up with basically two very fancy/interactive mid controls that need a lot of fiddling and can be finicky to get right. And depending on how they are set you then may not have much control of the low end from your bass, or lack treble after you have low-passed both of your pickups significantly.
I can see the Wal preamp as being an excellent and relatively simple way to tackle some of these issues. The filters go down to around 80-100Hz from my testing, so you can use one pickup as your 'bass boost' by rolling it off all the way, kicking in the resonance boost as desired, and then blending in the other pickup for your mids. Then deciding to engage the 'pick attack' to add back in treble if desired. It's really clever, I think, as it allows adjustability but is still usable. It also adds a bit of distortion to the sound, imparting its own sonic character.
I can see ACG's EQ-01 preamp as being an excellent way to try and tackle these issues, as well. I have not tested it as fully as I should have, but ACG decided to go as low as the Wal preamp (I think his initial preamps went even lower) and he included a circuit to blend treble back in from your choice of pickup. So you can use one pickup to control amount of low end, and decide how much treble to add back in. The bit that makes the ACG finicky is that the resonance boost for each pickup is variable as opposed to fixed, so 2 more knobs to twiddle, and the treble is variable in the range of frequencies affected and the amount you blend back in, so that gives another 2 knobs to tweak as well. If you can handle some of the extra adjustability, it's an incredible preamp. It also is extremely clean, and does not impart any harmonic distortion, which can be good or bad depending upon your point of view.
Alan's EQ-03 version I think refines his vision even further - http://www.acguitars.co.uk/wp-content/uploads/2017/05/ACG_EQ03.pdf
Nuno's Lusithand preamp splits the difference here a bit. His frequency range for the LPFs goes higher than the Wal (up 4.5kHz) but not as low (down to 150 Hz). So you do end up with more treble in the system to start off with, but if/when you cut those frequencies on both pickups, there's no way to bring it back. Equally, since his controls go to the low mids only, there's no way to really control the amount of perceived bass. So you're going back to the amp or pedals to tweak treble and bass.
I'm not familiar with Alembic preamps as I haven't used them.
Might be helpful about the pick attack response. There is this schematic of an older version of Wal electronics that's floating around the internet, which has a "Attack" function:
https://www.talkbass.com/attachment...e2889d805d-5000-0000074733c4bbba-gif.2309486/
Now, whether or not the new version uses the same topology or has the same functionality, I really don't know. But just for reference this it the frequency response when the "Attack" function is enabled and disabled:
Like I've said, I've no idea if it's the same on the new (current) Wal preamp, but it might help to get an understanding what the circuit does
On a side note, I'm amazed that no one has so far managed to trace the original preamp and share the schematics. You'd think that at least one Wal owner is electronics savvy and got the idea to do it
https://www.talkbass.com/attachment...e2889d805d-5000-0000074733c4bbba-gif.2309486/
Now, whether or not the new version uses the same topology or has the same functionality, I really don't know. But just for reference this it the frequency response when the "Attack" function is enabled and disabled:
Like I've said, I've no idea if it's the same on the new (current) Wal preamp, but it might help to get an understanding what the circuit does
On a side note, I'm amazed that no one has so far managed to trace the original preamp and share the schematics. You'd think that at least one Wal owner is electronics savvy and got the idea to do it
Attachments
Might be helpful about the pick attack response. There is this schematic of an older version of Wal electronics that's floating around the internet, which has a "Attack" function:
https://www.talkbass.com/attachment...e2889d805d-5000-0000074733c4bbba-gif.2309486/
Now, whether or not the new version uses the same topology or has the same functionality, I really don't know. But just for reference this it the frequency response when the "Attack" function is enabled and disabled:
View attachment 4679129
Like I've said, I've no idea if it's the same on the new (current) Wal preamp, but it might help to get an understanding what the circuit does
On a side note, I'm amazed that no one has so far managed to trace the original preamp and share the schematics. You'd think that at least one Wal owner is electronics savvy and got the idea to do it
I’ve seen that Wal Pro schematic floating around. That ‘pick attack’ model you have from it looks very much like what I observed in the Wal Mark 1.
That's a great idea and good luck with the project!
There are lots of photos of the electronics cavity of Wal basses, but none are usable for tracing. By the looks of the electronics though, it shouldn't be a problem to trace them. So it's a good thing you got to take quality photos and are able to work on that!
Passinwind
I know nothing.
- Dec 3, 2003
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- Designer/Toaster Tech @ Passinwind Electronics
Might be helpful about the pick attack response. There is this schematic of an older version of Wal electronics that's floating around the internet, which has a "Attack" function:
https://www.talkbass.com/attachment...e2889d805d-5000-0000074733c4bbba-gif.2309486/
Now, whether or not the new version uses the same topology or has the same functionality, I really don't know. But just for reference this it the frequency response when the "Attack" function is enabled and disabled:
View attachment 4679129
Like I've said, I've no idea if it's the same on the new (current) Wal preamp, but it might help to get an understanding what the circuit does
On a side note, I'm amazed that no one has so far managed to trace the original preamp and share the schematics. You'd think that at least one Wal owner is electronics savvy and got the idea to do it
A well known Wal collector handed me one of his basses at a TB GTG a few years ago and offered to let me take it home to study and/or reverse engineer it in whatever fashion I felt like doing so, but neither one of us had a case for it and getting it back to him would've been a medium grade hassle, so I passed. I'm not really into cloning products that are still in production, but I sometimes do learn a lot from making Spice models of them.
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A well known Wal collector handed me one of his basses at a TB GTG a few years ago and offered to let me take it home to study and/or reverse engineer it in whatver fashion I felt like doing so, but neither one of us had a case for it and getting it back to him would've been a medium grade hassle, so I passed. I'm not really into cloning products that are still in production, but I sometimes do learn a lot from making Spice models of them.
Yeah, I can understand not wanting to clone stuff that's in production. But you're also right, you do learn a lot when analysing, disassembling, simulating or reverse engineering products that you like
I’ve never played a Wal, and likely will never be able to afford to, but I have compared the general filters of the Lusithand and ACG:
I currently have both an ACG EQ-01 and a single Lusithand NFP, and for my needs I do prefer the Lusithand for my general use filter pre (enough that I actually have it mounted in an external box and have been using it to tweak the tone with all my basses since picking it up in the classifieds here)- however I now have the ACG mounted in a fretless where it really excels. I also previously had an ACG EQ-02 that I had mounted in a box as well, but also didn’t like that one as much as the Lusithand for that purpose. Having the higher sweep on the Lusithand filter really allows me to get that cutting bite that my old Alembicised PJ got that I fell in love with. I actually wasn’t aware that the Wal filters didn’t go up as high, and that is my main issue with the ACG in a fretted bass- that the filters when fully open don’t go as high as I’d like, and the HPF section doesn’t give the same kind of peaky boost as the Q control on the LPF filters (it sounds more like a shelving boost). The resonance of the ACG in general also isn’t as aggressive or “honky” sounding (I consider the “honk” a positive in this case as it cuts through so well) to me as either my old Alembic or the Lusithand (could be a matter of harmonic distortion as you mentioned, but I think the Q of the filter may somehow not be as sharp either). In a fretless the ACG excels for me as it has a generally smoother tone to it and I don’t need the same kind of hi-end bite, but for more aggressive fretted tones that cut through a mix I prefer the Lusithand/Alembic with their higher frequency sweeps and more aggressive resonance.
In any case I feel like the Lusithand filter with the boost engaged and turned up most of the way for one of the two pickups in a dual pickup instrument would get a pretty similar tone as I would go for with that Attack switch. If you were to use both of the filters in a dual filter preamp to boost in the lows or low-mids you’d be leaving a hole in the mids below the attack switch frequency, which isn’t a tone I could personally see using. With my ACG pre I tend to leave one of the two pickups with the filter close to or all the way open then get a resonant low-mid or mid boost with the other pickup to taste, the HPF is always the harder part to get where I want it though. I will probably build up a bass with the dual Lusithand NFP pres at some point as it really seems like it would do exactly what I would want from a dual filter pre in a fretted bass.
Fantastic feedback on this thread. Just wanted to say thanks and it is really helpful to compare our experiences/thoughts. Brilliant write up @sunbeast
I've never played a Wal. I have noodled on a used Alembic at Guitar Center. I thought the Alembic had an interesting preamp. I didn't really understand it (this was long ago before I really knew anything) but it sure sounded nice. Heavy though (and expensive) which is why I think I've stayed away from them all these years.
This sounds interesting. I know on my Sadowsky I rarely boost the treble. I do boost the bass, and I use the passive tone to make any other adjustments. I could see liking your preamp.
One could essentially wind a brighter pickup with a low resonant peak, impedance match or use a buffer to negate the peak, and have really wide even response pickups. Then combine that with a stereo preamp with one channel LPF and the other HPF. Then blend the two channels back together with a stereo mixer. That should allow for all of the cuts and boosts of a normal pre, plus some crazy combinations unique to itself. This would be easy to play with in a DAW. Just go direct in from a pickup and use a parametric to account for the natural resonance.
This is kind of the basis for the Broughton Resonant Filter Equalizer pedal if I’m understanding you correctly. I haven’t tried one, but I want to
I know this thread is about filter based pre-amps build into the instrument but is the programmable EQ2 pedal from sourceaudio not the perfect tool for basses without such a pre-amp?
EQ2 Programmable Equalizer
EQ2 Programmable Equalizer
