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Building a Wal....ish


funkle

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8 minutes ago, MrDinsdale said:

Звучит великолепно, я бы с радостью вставил эти звукосниматели и предусилитель в свой Jazz! Впечатляющая работа 🙌

Thanks a lot!  I am very pleased to receive such feedback!  In fact, the pickups play a very mediocre role here.  The whole point is for the pickups to be able to have a frequency response of at least 7kHz.  If the pickups have a lower response, the sound will be muddier and the pick attack will not produce the same sound.  In the wal circuit, the pickups are fed to a Zobel filter to filter out low frequencies at the input.  I took a different path and developed my own input stage, which creates conditions under which the pickup does not have a load, and its maximum frequency spectrum can be obtained.  This allows the wal clone to run with most pickups on the market.

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10 minutes ago, MrDinsdale said:

I’m not going to pretend I really understand most of that but it sounds like it’s excellent 😂

Thanks a lot!  I plan to make some circuits in the near future to send out to musicians for testing.  I have three prototype boards, but they are large enough to be used without problems.  Perhaps I could send you one of them for testing, but I need some time to finish my personal affairs and fully finish soldering them.  You and I have different units of measurement, so I’ll attach a photo on a sheet of squared paper.  If this topic is relevant to you in the near future, then I think we would do it without any problems.

IMG_20240518_184459.jpg

IMG_20240518_185011.jpg

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10 hours ago, Mark Dixon said:
10 hours ago, Mark Dixon said:

TI TL064 Op Amp substitute for the TAB1043? How much current does it draw? Care to share your schematic pls?

 

Tl064 is not a complete analogue of Tab1043. Current consumption of the whole circuit is about 500mA, if my memory serves me right) to be specific, the op amp model does not play a key role, except for the noise level. This circuit does not require high fast action, so I put TL06x. With the same success I could have put LF44x, and the result would have been the same. Half of the circuit is a copy of the original circuit, except for the input stages, which are my commercial development, which of course I can not share with you. But I am ready to answer your questions regarding the original circuit, timbre formation, no problem. Sorry for my English, it is not my native language

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11 hours ago, Stas said:

Continuing with the post, let me share the sound options. Which sound did you like?

All sounded great for different situations.  My personal preference was 3...I'm really curious about how it might make my Status bass sound.

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4 minutes ago, Kiwi said:

All sounded great for different situations.  My personal preference was 3...I'm really curious about how it might make my Status bass sound.

Thanks for your attention! It will take a little more time, and I will be able to supply them as a complete set. In my opinion, it would be interesting to make a complete set of pickups. Now I am developing a prototype of a pickup.

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18 minutes ago, Stas said:

Thanks for your attention! It will take a little more time, and I will be able to supply them as a complete set. In my opinion, it would be interesting to make a complete set of pickups. Now I am developing a prototype of a pickup.

I would expect that the best pickups would be as flat response as possible to allow the filters the greatest flexibililty. It would mean there is greater dependency on construction and materials for anyone chasing a specific timbre.

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25 minutes ago, Kiwi said:

I would expect that the best pickups would be as flat response as possible to allow the filters the greatest flexibililty. It would mean there is greater dependency on construction and materials for anyone chasing a specific timbre.

That's right - if you move the resonant peak beyond 7 kHz, the controlled range will be flat.

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To help answer the question "what is the source of the Wal tone?", I have designed a drop in TAB1043 replacement, using a surface mount TL064 SOIC 14 quad op amp soldered onto a DIP16 sized PCB .. I'm just waiting for the PCBs to arrive, then I can try it out..

 

I suspect it will prove that the TAB1043 is not the source of the Wal sound, but we will see!! 

 

And this will also mean that all Wal basses can live after the supply of TAB1043s have disappeared..

Screenshot 2024-07-15 at 11.58.36.png

Edited by SquiddlyDiddly
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3 minutes ago, SquiddlyDiddly said:

I suspect it will prove that the TAB1043 is not the source of the Wal sound

The interesting thing about the TAB1043, esp in low power mode, is the super low slew rate. My suspicion that I have no ability to prove either way is that given how many ppl have copied the circuit and ended up with “almost but cleaner” outcomes is that the combination of super low slew rate and the phase delay of the filter make the filter sound. 

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Yes, I wondered that too, the slew rate for the TAB1043 is 0.02 V/us for +/-9V with a bias current of 1uA, which would imply that it the TAB1043 is slew-limiting and thus partly the source of the Wal sound.

 

But there are other factors in the Wal circuit that could contribute more, which is why I wanted a drop in replacement to make it easy to measure and compare..

 

Plus there are other quad Op Amps with a similar slew rate to the TAB1043 which I can try..

 

I started down the path of cloning the preamp to make it easier for me to measure, I have created a schematic for the version of the Wal preamp which came with my Mk II 4 and MkII 5 string Wal basses, these preamps are different to the Mk I 4 string, the latter only supports 4 string pickups. I don't know which version of the preamp comes with the Mk III Wal bass or the 6 string Wal.

 

It's easier in a lot of ways for me to do it this way, as I know I haven't transcribed the circuit incorrectly..!

 

Later, when I have more time to check it, I will share my version of the Mk II schematic, which is absolutely complete and doesn't miss out any parts..

Edited by SquiddlyDiddly
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9 hours ago, LukeFRC said:

The interesting thing about the TAB1043, esp in low power mode, is the super low slew rate. My suspicion that I have no ability to prove either way is that given how many ppl have copied the circuit and ended up with “almost but cleaner” outcomes is that the combination of super low slew rate and the phase delay of the filter make the filter sound. 

The low slew rate of the op amp will realize the roll-off at high frequencies, but it will not give you the desired sound color. For the sake of experiment, you can put a capacitor in the feedback circuit of the output op amp, and I doubt that you will get wal.

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The wal preamp does indeed have distortions, but they are not caused by the slew rate :)

Here is the frequency response of the non-original, my clone, and below is the frequency response of the original wal preamp. The top graph is single jazz bass pickups, and the bottom is the given diagram of the wal pickups.

IMG_20240718_083256_edit_1248079265502005.jpg

Edited by Stas
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I suggest going even further and let's look at the waveform? :) The first picture shows the input signal. The second picture shows the signal at the distortion control point. The third picture shows the output signal. The fourth picture shows the output signal with peak attack enabled.

IMG_20240715_084155_edit_1070059723590010.jpg.67d64e470e4fbf87e4ac06ca7cd618ac.jpg

IMG_20240715_084241_edit_1070102755810089.jpg.1954fa32a080929c68c8f90655589592.jpg

IMG_20240715_084325_edit_1070148933625092.jpg.75e7be36228d1536860c15c335c4a2ad.jpg

IMG_20240715_084836_edit_1070455613270726.jpg.9b12cdc2fece7c70d895a93f731f35de.jpg

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Dear friends, I just now quite by accident noticed that the signal on both channels is simply perfectly distorted! Now I understand why both channels were processed with different filters! This is simply an ideal mix of two signals into a common sine! Blue bridge pickup, green neck pickup

IMG_20240718_141044_edit_1265037398145478.jpg

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2 hours ago, Stas said:

Dear friends, I just now quite by accident noticed that the signal on both channels is simply perfectly distorted! Now I understand why both channels were processed with different filters! This is simply an ideal mix of two signals into a common sine! Blue bridge pickup, green neck pickup

IMG_20240718_141044_edit_1265037398145478.jpg


What is the significance of this Stas? I’m not quite as expert as you are at understanding the deeper electronics side of this…

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4 minutes ago, funkle said:


What is the significance of this Stas? I’m not quite as expert as you are at understanding the deeper electronics side of this…

In simple words, in guitar limitation, symmetrical limitation is pleasant. When both half-waves have the same limitation. If you compare several limitations, such as a lamp, or a jfet, or a bipolar transistor - they will differ in the smoothness of this limitation. That is, ideally, the sine should be smoothly pressed from above, if you speak figuratively :) in the case of wal, both channels with the maximum open tone knobs give the maximum possible distortion, and in this case, both channels add up to form a very soft, and at the same time growling sine wave.

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7 minutes ago, funkle said:


What is the significance of this Stas? I’m not quite as expert as you are at understanding the deeper electronics side of this…

That is, mentally draw a line between these two colored sinuses, and you will see that the resulting signal will be neatly flattened at the maximum :)

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9 hours ago, Stas said:

The wal preamp does indeed have distortions, but they are not caused by the slew rate :)

Here is the frequency response of the non-original, my clone, and below is the frequency response of the original wal preamp. The top graph is single jazz bass pickups, and the bottom is the given diagram of the wal pickups.

IMG_20240718_083256_edit_1248079265502005.jpg

Great work Stas! This is the best, properly measured, analysis of the Wal preamp I have seen shared online, well done!!

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8 minutes ago, SquiddlyDiddly said:

Great work Stas! This is the best, properly measured, analysis of the Wal preamp I have seen shared online, well done!!

Thanks a lot!😃

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Question to Funkle - are you happy for Stas and myself to keep posting our documentation and analysis of the Wal preamp to your thread, or should we start a separate thread? -

 

I don't want to be accused of hijacking your thread..

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