Kinkh

@funkle Hey! I haven't been reading this thread for quite some time, so I'm not sure what I'm missing here. I just got a notification 😅 Your question was whether the filters have different cut off frequencies, right? Yes they do. The maximum frequency is very close on both filters, but the minimum frequency is around 100Hz for one, and around 150Hz for the other. And yes your ears were right

Yep, now I remember how it was done. All that remains are two things: some samples to try out on, and time to do it

I remember that there was a way to take a .wav file as an input in LTSpice, pass it through the circuit, and record the output as a .wav. I may have done that once more than 10 years ago, so I currently have no clue how to do that anymore... But, it might be the "best" way to see how something sounds when passed through one of these circuits.

I like the word threatened At one point, I'm going to try this schematic and build something of it. But be warned, I'm interested in copying these graphs, so I probably won't copy the schematic 100%. I'm just going to use it as a starting point. I have done a filter based preamp based on this particular filter topology, but not this exact implementation, and with some different ideas. So far it worked nice But when I start working on this, I'll start from there and use this as a guide, as I hate copying other people's work 😇

Might not be the method by which you can tell what component comes from where, but it could help when comparing two different instruments.... If you could record a note plucked from each string (from each of the coil pairs) directly from the pickup, and then plot a spectrogram ("3D" plot, with frequency, time, and intensity). Assuming the multi coil pickup is "transparent" in that it can pass all the frequencies produced by the vibrating string, you would get an actual idea of what sound is being produced by the bass itself (strings, neck, material, all those factors). Then start comparing that info with other known basses. And this is where a LOT of testing would need to be done... You would probably need to fit the original Wal pickup into other basses for testing consistency. One other interesting example would be to fit a random "known" pickup into the Wal, record a spectrogram, then record a spectrogram from another bass with that same pickup. Then compare the differences, and start guessing where they come from. This would be a big project, and pure physics related at that. But it might give some interesting insight if done properly. Just a food for thought... 😇

Hello everyone! I have been provided with the preamp photos by @funkle and been asked to share my findings here. it took a while due to various personal reasons, but here are the results. From the photos provided I have drawn this schematic. I'm sure it is about 90% accurate. Some parts were hard to trace by just looking at photos, and some values are approximate. The opamp used here is a generic opamp, since the original is not produced any more. Also, due to the obsolete opamp, the schematic doesn't include 4 resistors used to set the quiescent current of the opamp. Wal MK2 Trace.pdf What is interesting here is that the filters are tuned to different frequencies. The most interesting thing is how the Attack function is implemented. The signal from the Neck pickup is taken directly after the summing amp (which sums all the individual coil pairs), and put through a high-pass filter to leave only the high frequency content of that pickup. Then, that filtered signal is ADDED to the maim mix of the bridge and neck pickups after they have been filtered by their individual filter controls. I have also made a SPICE simulation of the circuit to better show what is happening here. Due to the transistors and opamp being obsolete, I replased them with generic ones, and put a normal summing stage at the input. When trying to build this circuit, the transistors can be omitted if a modern low noise opamp is used. This kind of stage was used in back in the day when low noise opamps were not readily available, and a simple transistor differential amp could make up for that by being added in front of the opamp. A logical question remains: do the outdated components contribute to the sound characteristic of this preamp? Maybe, maybe not. The opamp has limited bandwidth, and the overall stages might produce some distortion. As there is no definitive datasheet info on these parameters, it's up for debate and experimentation to answer that question. Anyways, here are the graphs from the simulations. Pickup_01 is neck, and Pickup_02 is bridge. Now the Attack gives off some strange results depending on how you set the Attack trim pot inside. So here are a few results. That's about all I can think of that's worth mentioning at this time. IF you guys have any more questions, feel free to ask Cheers!