ZON bass preamp  [schematic]

Pickups, wiring schemes, switch techniques and onboard active electronics for guitars and basses
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Yun_Suki
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Post by Yun_Suki »

I don't remember which one...

But...however, I have made a copy that works fine.
875276590348dd41b40c61e691ca565.jpg
b7926fa2e2d80863e8cb8cec6c519f5.jpg
63f5549eaed2fadf4ffd520a69f18a7.jpg
8d160049f2afacbc94714173bf45e65.jpg
————————————————————————————————————————

The progress of the reverse engineering will be updated again after a while...
60163d4eae5a0b96788345b085ccf34.jpg

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darmstat
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Post by darmstat »

Is there a schematic?

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george giblet
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Post by george giblet »

The preamp is the one with the Magnetic + Piezo pickups (ZP-3).

Any chance to get the cap values and pot values?

I've traced 99.9% of the schematic but there are very few caps values and no pot values.

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Post by Yun_Suki »

This is the value of the component as well as the model number.
ZON 贝斯内置主动电路_2022-12-20.pdf
(231.83 KiB) Downloaded 175 times
PCB_ZON 贝斯内置主动电路_2022-12-20.png
ZON-pre-BOM.txt
(859 Bytes) Downloaded 113 times

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Yun_Suki
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Post by Yun_Suki »

george giblet wrote: 20 Dec 2022, 00:16 The preamp is the one with the Magnetic + Piezo pickups (ZP-3).

Any chance to get the cap values and pot values?

I've traced 99.9% of the schematic but there are very few caps values and no pot values.
Hi,All potentiometers and trim potentiometers are 100KΩ

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george giblet
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Post by george giblet »

Thanks a lot for all that detailed information.
Awesome, stuff!

The schematic appears below. I've tried to match the part designators on the your PCB.

I've also added the EQ curves.

It is interesting how much the Mid switch frequency affects the bass control even though
the mid control is set flat.

The treble controls are not symmetric, there is more cut than boost.

The 100k's on the first stage of the magnetic preamp and the 470k/220k's on the
second stage are going to be adding a lot of noise. I suspect replacing
the second stage with a non-inverting amplifier like U3b would lower the noise.

The circuit and parts values are very similar to the National Semiconductors
applications notes and datasheets! (11k, 3k6, 100k pot)
zon ZP-3 V1.0.png
Attachments
zon ZP-3 - EQ - Treble (cut).png
zon ZP-3 - EQ - Treble (boost).png
zon ZP-3 - EQ - Mid.png
zon ZP-3 - EQ - Bass.png
Last edited by george giblet on 22 Dec 2022, 03:10, edited 2 times in total.

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george giblet
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Post by george giblet »

FYI, here's a pic of a 4-string (Zon Legacy Elite 4). You can see how the Piezo is wired.
Attachments
Zon Legacy Elite 4 - ZP-3 Preamp.JPG

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Post by Yun_Suki »

george giblet wrote: 20 Dec 2022, 23:26 Thanks a lot for all that detailed information.
Awesome, stuff!

The schematic appears below. I've tried to match the part designators on the your PCB.

I've also added the EQ curves.

It is interesting how much the Mid switch frequency affects the bass control even though
the mid control is set flat.

The treble controls are not symmetric, there is more cut than boost.

The 100k's on the first stage of the magnetic preamp and the 470k/220k's on the
second stage are going to be adding a lot of noise. I suspect replacing
the second stage with a non-inverting amplifier like U3b would lower the noise.

The circuit and parts values are very similar to the National Semiconductors
applications notes and datasheets! (11k, 3k6, 100k pot)

zon ZP-3 V1.0.png
Wow, very detailed! Thank you for your contribution to the forum! (a Big Hug~)

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george giblet
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Post by george giblet »

No problem. Thank you for all your efforts.

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Post by george giblet »

I've managed to trace the ZP-2 as well.

Unfortunately this tracing doesn't have the accuracy of the ZP-3 schematic.
As far as I know, the ZP-x preamps are the polyfusion preamps and the ZB-x preamps
are the Bartolini preamps.
zon ZP-2 V1.2.png
pcb front - ZP-2 1997.jpg
pcb back - ZP-2 1997.jpg
Last edited by george giblet on 22 Dec 2022, 23:05, edited 2 times in total.

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Post by Yun_Suki »

george giblet wrote: 21 Dec 2022, 10:50 I've managed to trace the ZP-2 as well.

Unfortunately this tracing doesn't have the accuracy of the ZP-3 schematic.
As far as I know, the ZP-x preamps are the polyfusion preamps and the ZB-x preamps
are the Bartolini preamps.

zon ZP-2 V1.0.png
pcb front - ZP-2 1997.jpg
pcb back - ZP-2 1997.jpg
————————————————————————————————————————————————
I've also got this board from a friend before.
But unfortunately, I lost it before I could collect the component values of the capacitor...

These are the photos that my friend provided me:
3be6cfee8c54b6c969bd9f662ae4bd6.jpg
1ca366acc39188ae0483d88ae8683d1.jpg

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george giblet
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Post by george giblet »

Thanks for the new pics. They were very useful.
Since the one of the pots is removed I could confirmed the circuit around C5 and R7.
I also made a better guess of the circuit around U1a - still not confident it is correct.
Added better guesses for the tone control caps.

I updated the ZP-2 schematic in the previous post to version 1.1

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Post by george giblet »

OK I've updated the ZP-2 schematic to V1.2
- fixed one error on U1a
- added more notes
- added trace info for older Rev A PCB

ZP-2 Rev A PCB (1995):
1995 Zon Legacy Standard 4 String.jpg

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