I have been a diyAudio member for about 1 year; mostly interested in Pass Labs threads. I find it amusing that the words bjt and Class AB appear rarely in them; as if they are forbidden. DIYers are exclusively interested in using and speaking of "FET" devices in strictly Class A designs. The selection of acceptable FETs is nowhere as extensive as for bjts. Unfortunately this limits the DIYer's "degrees of freedom" to experiment and diy. Maybe in your design, a Darlington is truly a better cascoder than a MOSFET. I find it interesting that F6 is based on a Classic design which used bjts and operated Class AB.
The concept drawing was a cut / paste job with the Zen 9 Cascode added to the F6 replacing the JFET outputs. And I learned something from it. If I build it, I will try it both ways.
If you want to play with BJT and Class AB, the larger Solid State Forum is ideal.
Nelson's interests are in class A and FET, so that is where this board is focused.
The more focused scope makes for a more collaborative experience.
Doug
If you want to play with BJT and Class AB, the larger Solid State Forum is ideal.
Nelson's interests are in class A and FET, so that is where this board is focused.
The more focused scope makes for a more collaborative experience.
Doug
Thank you for your well put insights and direction. Other DIYers [I hope] and I look forward to your concept amp.
Best regards.
what's up , Dodos ?
On vacation with the in-laws.
Oh, maybe this wasn't directed just at me?
Rush
she is who must be obeyed
so - in-laws are closest kin
enjoy ........ you're excluded from Dodos
so - in-laws are closest kin
enjoy ........ you're excluded from Dodos
visiting the grandkids in Seattle 😀😀😀
When Tea Bags boards arrive I will compare Jensen's and Oneticcs. Maybe this year somebody will release some SITs - think that will be the next step !!!
Also on the bench top is a AlephJ Jango. Boards are stuffed - waiting for PSU parts
Happy holidays to all you great guys here on the DIY forums
Best
Bob
When Tea Bags boards arrive I will compare Jensen's and Oneticcs. Maybe this year somebody will release some SITs - think that will be the next step !!!
Also on the bench top is a AlephJ Jango. Boards are stuffed - waiting for PSU parts
Happy holidays to all you great guys here on the DIY forums
Best
Bob
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Started mine today. Also got some Sit parts for complimentary F6, kudos to Rush
Really? That's awesome! I have all the pieces, except for a couple small resistors. I need to get my chassis to a decent machinist for a bit of modification, and then it goes to the top of the list.
What PCB are you using? And do you have any spare R100's ? 😉😛😛😛😉🙂🙂🙄
Using the Peter Daniels boards - when I'm back in CA I'll post a pix in the Jango thread
Sorry I don't have any extra R100s
In fact if I screw up the project goes away
Sorry I don't have any extra R100s
In fact if I screw up the project goes away
LOL.
I get it. 😉
My delay for my Jango project is chassis - I need to have the UMS drilled into the chassis I am using. (As well as the holes for Peter's boards.) That chassis will be made modular, and serve as the test bed for my F6 and the 'normal' Aleph J.
I am working with Generg to get distortion figures off my F6. Got the probes and software, just brain in the way now!
I have searched but not found the input level requirements for maximum output. Is it 2 vrms? If so, does it mean that the negative feedback to the transformer primary is mandatory in order to get the smaller Vgs range to stay in class A?
Must be.... I received some SJEP120R125's and ran one thru my home made curve tracer. I think the curves are very close and gives me an op point very close to what Pass talks about. Max Vgs swing is around .6v to .7v to remain in class A. It is quite cold in Los Angeles today and I was not able to get the transistor to go above 35 degrees Celsius. Tried heating it further with a small shrink wrap gun but it did not make a difference on the Id. I have the transistor on a large heatsink.
I did not capture the effect on the below curves, but going above 2 on the Vgs make the upper curves look bad as my tracer can't provide the required incrementing Ig.
I did not capture the effect on the below curves, but going above 2 on the Vgs make the upper curves look bad as my tracer can't provide the required incrementing Ig.
