'ceci est un Cube' amplifier from JM Plantefeve

About ten days ago I finally returned to my hobby. The first task was to improve the existing regulators in the amplifier. The references were replaced with improved versions with tantalum resistors, also in the regulator itself all the important resistors around the op amps were also replaced with tantalum resistors. The new references were made with 0805 SMD components. The PCB size is only 18x14mm.
 

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very simple, in the original schematic instead of R8 put a 100R trimmer in series with a 68R resistor, that way you will be able to adjust the current of the output transistors
Hi grunf,
Thank you for your reply.
Yes, I have fully understood this. What I was referring to was the the trimmers connecting to the sources of the 2SK170s. In ZoltanChivay's schematic, I can see that he uses just one trimmer on the source of the upper JFET and a fixed resistor on the source of the lower JFET. In your implementation, I guess that you have used a combination of resistor/trimmer (R4 and R5 in the original schematics) on the sources of both JFETs.
According to what ZoltanChivay says in post #8, R16 adjusts the DC offset at the output and R15 adjusts the bias of the output MOSFETs. So, in that case, is the trimmer on the source of the lower JFET necessary?
Regards,
Evangelos
 
Hi kenev
You can also put R5 fixed, without a trimmer if you know in advance what value is needed for a current of 1.2mA through J2.
I would still put a trimmer, it is better to leave the possibility of adjustment as in the original schematic.
 
Hi kenev
You can also put R5 fixed, without a trimmer if you know in advance what value is needed for a current of 1.2mA through J2.
I would still put a trimmer, it is better to leave the possibility of adjustment as in the original schematic.
Hi grunf,
Thank you once more for your reply.
I'm in the process of designing a new PCB (mainly, based on the original PCB published by JMP, but with a few modifications) and wanted to be sure about this issue.
Regards,
Evangelos
 
olives harvested, processing finished, we got 105 liters of extra virgin olive oil, an excellent result considering that the last 6 years were bad due to drought
I still have to paint the wooden boat and then I'm back to DIY
Beautiful trees. They look like they were around since ancient Roman times.
We "only" got 47L. 🙂
Interestingly i was looking at google maps recently, and somewhere between Zadar and Šibenik is the closest foreign city in the world to Vatican. Excluding Italy of course, which is technically a "foreign country" to Vatican.

Coincidentally good news to see on the high current WJ SR, i wasnt following for a while but i know i was interested in your progress last year. Well at least i will instantly make this one the day its released. Be it whenever