Hi all,
I'm looking for the value of the parts needed on the Accuphase frequency board being used in the F20/25 active crossovers.
Have a 180Hz card but need 250Hz (or 290Hz).
So far by looking at the pictures of the FB-250 card I found:
The PCB itself (115-0690-14) and R17-R18 look to be the same across different models.
Attached are a few pictures I of the FB250 I could find on the internet, on one I added the part number for the sake of convenience.
I'm looking for the value of the parts needed on the Accuphase frequency board being used in the F20/25 active crossovers.
Have a 180Hz card but need 250Hz (or 290Hz).
So far by looking at the pictures of the FB-250 card I found:
- C1-C12 120nF (124)
- R1-R8 19.6k 1%
- R9-R10 12k 5%
- R11-R12 960R 5%
- R13-R14 36k 5%
- R15-R16 68k 5%
The PCB itself (115-0690-14) and R17-R18 look to be the same across different models.
Attached are a few pictures I of the FB250 I could find on the internet, on one I added the part number for the sake of convenience.
Attachments
Last edited:
That's the best kept secret in audio industry.
Jokes aside, I doubt anyone has the schematics of the F-20/F-25 besides Accuphase themselves (which is probably why the cards are stupidly expensive). I know there are clones but I want to keep the original Riken/Amtrans through hole resistors and silver mica caps.
Jokes aside, I doubt anyone has the schematics of the F-20/F-25 besides Accuphase themselves (which is probably why the cards are stupidly expensive). I know there are clones but I want to keep the original Riken/Amtrans through hole resistors and silver mica caps.
Last edited:
Did you run across this thread? I didn't download the zip file, but it appears someone else has been through this exercise.
https://www.diyaudio.com/community/...-crossover-board-mod-help.279073/post-4454742
https://www.diyaudio.com/community/...-crossover-board-mod-help.279073/post-4454742
Last edited:
Without reverse engineering, there is no way to properly change the parts values or frequency,
unless someone has a board with those frequencies and can give you that information.
Some would say just scale the capacitors smaller, or the resistors smaller, but that won't necessarily be correct.
It's probably a case of reverse engineering or finding a mathematical formula, assuming Accuphase's filters aren't something unique.
@mattstat,
Just checked that thread, shame it ends up as usual, with one saying he has the service manual and everyone else asking for it over the years 😀. Sadly I don't see any option to send @2SA991 a private message. I hope he can chime in.
I can order another F-20 from Japan, with 290Hz card but that's not the most wallet friendly option, to say the least.
@mattstat,
Just checked that thread, shame it ends up as usual, with one saying he has the service manual and everyone else asking for it over the years 😀. Sadly I don't see any option to send @2SA991 a private message. I hope he can chime in.
I can order another F-20 from Japan, with 290Hz card but that's not the most wallet friendly option, to say the least.
Last edited:
dch53 apparently measured multiple boards and has the service manual. That's another person you could try to contact.
The devil is in the fact that I need the capacitor and resistor values for the needed frequency to modify the card from 180 to 250Hz and the values are not publicly known, unless taken from picturers of a 250Hz card but it's still a bit of guesswork as you cannot clearly see the values of all capacitors.
Anyway, I bought a second F20 with the 290Hz (Altec/JBL) card.
I will gladly post the values and photos of the card when it arrives.
Anyway, I bought a second F20 with the 290Hz (Altec/JBL) card.
I will gladly post the values and photos of the card when it arrives.
I mean that once you recreate the actual schematic, you can pick out C1/C2/C3, R1/R2/R3 etc and recalculate for new frequencies:
https://sound-au.com/project08.htm
https://sound-au.com/project08.htm