Cubie - small F5 variant with GR grade JFETs and LatFETs

[juma]

Aber gerne !
Looks good although if I had to make it again I would put MOSFETs on shorter sides of PCB to add some more space between them, like this (post #963 and #972) :
http://www.diyaudio.com/forums/pass-labs/121228-f5-power-amplifier-20.html#post1525502
Anyway, it's not critical here because power supply voltage is +/-16V and the Id is about 0.8A, so Pd per MOSFET is 13W only.

 

[JPS64]

well... done!

Will build it for a friend (2SJ74GR, 2SJ162, 2SK1058 Reichelt, 2SK170GR Dönberg).

Ok, let make the power supplies...

JP

 

[juma]

 

[JPS64]

Power supply. I´ll go mono and 2 versions: with CMC (WE) or resistor (SMQ). Schottkys are FSV1045V.

JP

 

[wengtech]

Hello Juma,
Is it possible to make BA3 output with latfet?
would you share the schematic please?

Thanks.

 

[juma]

This is not the thread about BA3 - please post your question in appropriate thread.

 

[marconi118]

well... done!

Will build it for a friend (2SJ74GR, 2SJ162, 2SK1058 Reichelt, 2SK170GR Dönberg).

Ok, let make the power supplies...

JP

are you sure that they aren't fake?
especially the j74 and k170

 

[vizion]

Hi Juma,

Is it possible to reduce power even further ? An output of 3w Class A / 6w Class AB would be nice. I already have a 3w SE Mosfet. Cubie push pull would be a nice addition.

What is the output impedance ?

Thanks.

 

[juma]

Hi vizion,
lowering the PS voltage to about +/-12V is the obvious way to do it.
Zout is less than 0.1 Ohm

 

[wengtech]

hello Juma,
if i want to build this cubie for 50watt output power
how many pairs do i have to pararel the output TR?
is it still the same voltage rails and bias settings?

thanks.
peter

 

[Dennis Hui]

Peter, you might want to have a look at Juma's Cubie3 design:

Cubie3

 

[wengtech]

Peter, you might want to have a look at Juma's Cubie3 design:

Cubie3

hello Dennis,
i am thinking of common source topologies, while cubie3 is common drain.
in my opinion common source has a magical sounding, like F5 amp.

 

[juma]

hello Juma,
if i want to build this cubie for 50watt output power
how many pairs do i have to pararel the output TR?
is it still the same voltage rails and bias settings?

50W @ 8R means higher voltage power rails and cascoding JFETs at least, so it would be practically a new design.
Just adding more output pairs would take you to 50W only if you use very low Z speakers (1-2 R)

 

[coolnose]

Wondering if I could try with a single transformer 2x15 transformer only, PSU is 25mF - 2.2mH - 25mF per rail ? Trying to put a finished amp case I have around to use... Thanks

 

[juma]

Sure, 2 secondaries for stereo version are OK - with 2 x 15V AC you'll get about +/-20V DC and that's all right too.
But if you already have input JFETs and output LATFETs you'd be much better of building Cubie 2: Cubie2

 

[coolnose]

Thanks Juma, I'll look into cubie2 ...