Mike Pope - Flexcore

[difesa98]

Hi!
i bought an used Mike Pope Flexcore and i want to obtain the schematic in order to simulate it via spice and see the frequency response. Here it is some high quality photos, i've already traced it (red=upper layer, blue=bottom layer) and i tried using fiverr for the "EQ section", the pcb where is located the quad-opamp (there is an error in the fiverr schematic: seeing the 6 holes the guy thought of a stereo pot but in reality the EQ pcb is used either with the bass control or a concentric bass/treble pot).
The low-Mids module is exacly the same as the Hi-Mids in the photos and the name for the exact same location resistor and capacitor are:
Hi-Mids PCB-->Low-Mids PCB
C19-->C23
C20-->C24
C21-->C25
C22-->C26
R21-->R28
R22-->R29
R26-->R33
R27-->R34

The blend pot is an MN250K; all EQ pot are B100K. I will measure the capacitor on the PCBs as soon as the multimeter arrives. From the flexcore website you can see how everything is wired together.
Maybe someone is interested to help me draw a schematic of the most expensive bass onboard preamp?

https://imgur.com/gallery/cDzIWNu

[difesa98]

Here it is every value for resistor and capacitor:

[difesa98]

I tried to re-draw the Fiverr EQ PCB schematic and it turns out to be a baxandall filter for treble and bass. I used a standard voltage divider for the V/2 but probably this preamp uses a different method since on the blend PCB (where I believe the power supply is managed) there are a mosfet 3055 and a TL062.
I'm using the TL1112 instead of the LF444 because is already in LTSpice.

[lietuvis]

Here you go, I think I ever did simulation in SPICE and mid frequencies correspond preamp specs.

[difesa98]

Here you go, I think I ever did simulation in SPICE and mid frequencies correspond preamp specs.

OMG! Thanks Man, it's a really good schematic
I will simulate it and i will share the frequency response if anyone Is interested

[difesa98]

Here you go, I think I ever did simulation in SPICE and mid frequencies correspond preamp specs.

Here it is my SPICE simulation, everything seems good exept for one low-mids frequency: without the switching option it is centered at 900Hz instead of 500Hz-ish; it works in the same area of the first hi-mids frequency.
From the manual:
Treble: +/- 15dB at 6kHz or 10kHz
Hi Mid: +/- 15dB at 1kHz or 1.8kHz
Lo Mid: +/- 12dB at 330Hz or 473Hz
Bass: +/- 12dB at 46Hz or 90Hz

There isn't any infomation abour the overall gain (which is a 100K) but is works pretty fine. Do you have your SPICE simulation? maybe i did something wrong

[difesa98]

Found the error! There are 2 cap in the reverse order! The 15nF and the 3.9nF. This is the corrected simulation and finally everything seems to be right

[LuisMerino]

Hello there, some notes to consider after my testing



The gain trimpot is 100k, i verified with an actual mike pope flexcore preamp, 20db gain, wow

I modified the capacitor that goes to ground after the trimpot to 2.2uf, to prevent it from cutting the low frequencies so much at the beginning, change the 220pf to 22pf to avoid filter the high frecuencies too.


I hope the recommendations are useful to you, excellent work you did.

thank you

[vahid_m]

can i have pcbs picture without ic soldering on it ? Then I can make the pcbs and schematic