I have plenty of bc550/560, so I am using those
today i started putting power transistors on heatsinks, and I hit first road block those 2SK725 which I want to try have much smaller holes than IR, so I started to drill them larger, that was not very successful
holding transistor in hand is almost impossible, that black stuff is hard
eventually i found smaller screws and started fiddling with it
it will take much longer time to adjust, settings for F1 do not match
anyway, small progress, but I am just tempted to put original F1 transistors in it
It's alive!
I had to reduce R7/R8. It works with 2SK725 just as well as with IRFP240.
one thing i need to address is small hum with volume control in the middle
its weird, there is no hum at zero or at max volume wiper, just around middle
may be grounding, because so far its all the big mess on the floor
but it works!
I had to reduce R7/R8. It works with 2SK725 just as well as with IRFP240.
one thing i need to address is small hum with volume control in the middle
its weird, there is no hum at zero or at max volume wiper, just around middle
may be grounding, because so far its all the big mess on the floor
but it works!
BOM Correction
The BOM from Post 31 incorrectly shows R29 and R30 as 47ohm in the part number and description columns. They should be 0R47 ohm. The updated parts list in this post has the error corrected. Sorry for any trouble you may have experienced because of this error.
Note: the .zip file below contains and excel version of the BOM.
The BOM from Post 31 incorrectly shows R29 and R30 as 47ohm in the part number and description columns. They should be 0R47 ohm. The updated parts list in this post has the error corrected. Sorry for any trouble you may have experienced because of this error.
Note: the .zip file below contains and excel version of the BOM.
Everything looks great! 
There are 9 sets of amp boards and 7 power supply boards available, but without placing another order I would like to sell the power supply boards and amp boards together as a set to maximize the number of amps that can be built. There are plenty of bridge rectifier boards and LED boards so those are available independently in any quantity that is desired.
Hi bubasan, I do have a set of F1 boards, but shipping prices have gone up since 2021. Cheapest option is USPS Priority Mail @ $41.70. I learned the hard way in the F3 group buy that at this price there is effectively no shipping insurance and tracking often disappears when the package is handed off from USPS to the delivery service in the destination country. I can ship it this way if you want, and I will provide you with proof of shipping. I am not making money on these boards, I just want to help other diyer's, but I can't invest hours corresponding with USPS if you package doesn't arrive or runs late (some packages took 8+ weeks in the last group buy). Shipping will be at your own risk. If I haven't completely scared you off, send me a PM with exactly what boards you want and I will get you a full price.
Hi csample,
back in 2015 I made Fidelio boxes with Lowther EX3 drivers, tried various amplifiers, but the problem of poor response remained. Made an ACA amplifier from the Pass workshop and I hope it's correct because without the F1 I can't solve the broadband driver problems. Maybe I'm wrong?
bubasan69, 1 pairs of amp boards, 2 power supply boards, 2 pairs of bridge rectifier boards, 2 pairs of led mounting boards.
To Croatia.
I have the following boards available:
qty(1) Pair of Amp Boards
qty(2) Power Supply Boards
qty(0) Pair of Bridge Rectifier Boards (sorry none left)
qty(2) Pair of LED Mounting Boards
Cost is 15 + 2*6 + 2*1 = $29 for boards
Shipping to Croatia via USPS Priority Mail International is $40.45, Total is $69.45. Please let me know if you are interested or want any changes. If you would like to proceed, please PM me the email address associated with your PayPal account and I can send you an invoice. Thanks