Hi Biju,
For me, if I want a pushpull amp, I will considered to build F5T.
Because to my newbie ear, common drain complementary output much better.
But other people may have a different taste. 😉
For me, if I want a pushpull amp, I will considered to build F5T.
Because to my newbie ear, common drain complementary output much better.
But other people may have a different taste. 😉
I am using both the BA-3 preamp AND a complete BA-3 Power amp. Plenty of gain!
Russellc
What are people using for the N and P MOSFET outputs on the FE boards? I'm having a hard time finding either the right part or the alternate parts on the BOM.
P: 2SJ313 or FQP3P20
N: 2SK2013 or FQP3N30
P: 2SJ313 or FQP3P20
N: 2SK2013 or FQP3N30
Mouser has thousands of the Fairchilds -
FQP3P20 Fairchild Semiconductor | Mouser
FQP3N30 Fairchild Semiconductor | Mouser
FQP3P20 Fairchild Semiconductor | Mouser
FQP3N30 Fairchild Semiconductor | Mouser
That's bizarre. I did a Google search on them earlier and the Mouser result never came up. If I don't have the means to match these myself, who on here sells them?
EDIT: I PM'd Buzzforb. Let's see what he has.
EDIT: I PM'd Buzzforb. Let's see what he has.
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the BA3 has no paralleled active devices.
Therefore
Only where paralleled active devices are used, does it become necessary to do some selection/matching.
Pass has a webpage describing how they recommend that you do this, if needed.
Therefore
as stated by 6L6 applies.
Only where paralleled active devices are used, does it become necessary to do some selection/matching.
Pass has a webpage describing how they recommend that you do this, if needed.
Hi 6L6,
I 'd like to build 2 x BA-3 Balanced mono blocks. Will you point me to the right direction please ( thread?)? I suppose I don't need complimentary boards.
Zz
I 'd like to build 2 x BA-3 Balanced mono blocks. Will you point me to the right direction please ( thread?)? I suppose I don't need complimentary boards.
Zz
So this leads me to believe the only matched pieces on my whole SE BA-3 are the IRFP240's? Can I forgo matching the input JFET's as well?
So, I haven't heard from buzzy yet. Would it be safe if I just went and bought the output mosfets from Mouser w/o matching, and then sourced the matched JFETS online or whatever?
I'm confused on why the JFETs would need to be matched, but not the output MOSFETS. Doesn't the signal run through both of them?
I'm confused on why the JFETs would need to be matched, but not the output MOSFETS. Doesn't the signal run through both of them?
If the Jfets are in the same general area of Idss, say within 10-15%, then they have fairly equal self-bias, letting the bias pots (P1, P2) have enough adjustment for the mosfet to get in balance and keep the DC offset (before the output cap) in good trim.
The two jFETs are in series. The upper NjFET passes the same current as the lower PjFET.
The difference between the actual Id and the Idss determines the Vgs of each device. This can be estimated from the graph in the jFET datasheet.
The difference between the actual Id and the Idss determines the Vgs of each device. This can be estimated from the graph in the jFET datasheet.
Thanks guys. I have 12 matched IRFP240's coming, and am compiling some last remaining items. Then all I need is the transformer and chassis.
I'm putting some effort into the front panel too. I'll be turning some giant aluminum knobs myself and then I'm going to make a bird's eye maple front panel with blue backlit knobs. Stay tuned.
I'm putting some effort into the front panel too. I'll be turning some giant aluminum knobs myself and then I'm going to make a bird's eye maple front panel with blue backlit knobs. Stay tuned.