Dear schultzsch,
if i had found that MOSFETs yield better results than BJTs i would have used them as VAS.
I tested those tiny gm small laterals (j77 and k216) as well as nice pi-MOSFETa (j313 and k2013) but BJTs took the cake.
The behavior of MOSFETs and BJTs is too different so you can't just use them as drop-in replacement in this design.
So, if you don't know what are you doing, you either revert to original, proven design (post #1) or you start from the scratch...
Good luck, have fun
if i had found that MOSFETs yield better results than BJTs i would have used them as VAS.
I tested those tiny gm small laterals (j77 and k216) as well as nice pi-MOSFETa (j313 and k2013) but BJTs took the cake.
The behavior of MOSFETs and BJTs is too different so you can't just use them as drop-in replacement in this design.
So, if you don't know what are you doing, you either revert to original, proven design (post #1) or you start from the scratch...
Good luck, have fun
At this point I can try them all and see what I like the most.
You are right, some compensation caps on the vas did the job.
Thanks juma!
Today (finally) I finished The Cubie 3 amplifier!
I installed both channel into the final enclosure. It is a keeper amplifier that is sure.
Thank you Juma for your knowledge and for sharing with us!
I have 37 to 38 VDC rail voltage, I set up the bias 520 mA. Heatsinks get comfortably warm like 45-50 C degree.
I can keep my hand even more than 10-15 sec.
No smoke, this time no problem at the set up.
Thank you Prasi for the PC boards and designed!
I installed between the main Gr and signal Gr a 3.1R resistors.
Some pictures.
The enclosure will need some cleaning, maybe painting.
Yesterday I ordered a brass color know from Ali-express to match the front of the amplifier.
I encourage all those who has the PCBs or populated but never finished it to finish it. It is a good sounding amplifier! It worth to be finished.
Greetings to all
I installed both channel into the final enclosure. It is a keeper amplifier that is sure.
Thank you Juma for your knowledge and for sharing with us!
I have 37 to 38 VDC rail voltage, I set up the bias 520 mA. Heatsinks get comfortably warm like 45-50 C degree.
I can keep my hand even more than 10-15 sec.
No smoke, this time no problem at the set up.
Thank you Prasi for the PC boards and designed!
I installed between the main Gr and signal Gr a 3.1R resistors.
Some pictures.
The enclosure will need some cleaning, maybe painting.
Yesterday I ordered a brass color know from Ali-express to match the front of the amplifier.
I encourage all those who has the PCBs or populated but never finished it to finish it. It is a good sounding amplifier! It worth to be finished.
Greetings to all
Attachments
Jfets available here-
https://www.ebay.com/itm/2560703159...UXBIsOrjmGP4g2IWvkYEFpYQgk|tkp:Bk9SR9rtkOiBZQ
https://www.ebay.com/itm/2560703159...UXBIsOrjmGP4g2IWvkYEFpYQgk|tkp:Bk9SR9rtkOiBZQ