Boards
Hi Juma,
All the boards are going to snap apart at the yellow line between them. I'll be mounting the PS board on one heatsink, and running wires off to the two channels, each of which would be on a separate heatsink.
I just did the B1 board for fun, since I had a few square inches of PCB left. I'm allowed 60 sq. inches, so I might as well use it! I'll be putting it in a separate box with a 23 position stepped ladder attenuator. If I like it, then I might just run straight from my Aleph Ono, into the B1, then into the F5. My current speaker project is going to come out between 99 and 100 dB @ 1W, so I think it'll be more than sufficient gain-wise.
I suppose if you had a truly giant heatsink you could leave the whole board as one piece and mount it, but I think the fets would be too close together for good heat dissipation.
Estman,
I've used the IRFP244, and I saw the specs for the SFH9240. I'm not convinced a fet optimized for switching is a bad thing really, so long as you can find two that match. Lower gate charge and capacitance is always good, better power dissipation is good, and the transfer characteristics remain pretty similar.
Patrick,
Thanks for the links, and good work with the measurements! I skipped a few pages in the middle of this thread, and completely missed that part.
Did you happen to check any other devices while you were at it, or did you stick to the FQA parts?
Thanks for the comments, and I'll keep everyone posted on the testing once my boards get here.
Cheers,
Owen
Hi Juma,
All the boards are going to snap apart at the yellow line between them. I'll be mounting the PS board on one heatsink, and running wires off to the two channels, each of which would be on a separate heatsink.
I just did the B1 board for fun, since I had a few square inches of PCB left. I'm allowed 60 sq. inches, so I might as well use it! I'll be putting it in a separate box with a 23 position stepped ladder attenuator. If I like it, then I might just run straight from my Aleph Ono, into the B1, then into the F5. My current speaker project is going to come out between 99 and 100 dB @ 1W, so I think it'll be more than sufficient gain-wise.
I suppose if you had a truly giant heatsink you could leave the whole board as one piece and mount it, but I think the fets would be too close together for good heat dissipation.
Estman,
I've used the IRFP244, and I saw the specs for the SFH9240. I'm not convinced a fet optimized for switching is a bad thing really, so long as you can find two that match. Lower gate charge and capacitance is always good, better power dissipation is good, and the transfer characteristics remain pretty similar.
Patrick,
Thanks for the links, and good work with the measurements! I skipped a few pages in the middle of this thread, and completely missed that part.
Did you happen to check any other devices while you were at it, or did you stick to the FQA parts?
Thanks for the comments, and I'll keep everyone posted on the testing once my boards get here.
Cheers,
Owen
> Did you happen to check any other devices while you were at it, or did you stick to the FQA parts?
I built two versions of my balanced circuit, based on Toshiba's and Fairchild's. Results of both have been published. You just need to go back to those pages.
As to which is better, I guess you would ask...
It is well known that I like Toshiba's, so I am afraid that my opinion would not be neutral.
But since most of you are here to build DIY Pass amps, I can always recommend you to adhere to original schematics from Nelson. The added bonus is that the Fairchild parts are much less expensive than the Toshiba's.
Regards,
Patrick
I built two versions of my balanced circuit, based on Toshiba's and Fairchild's. Results of both have been published. You just need to go back to those pages.
As to which is better, I guess you would ask...
It is well known that I like Toshiba's, so I am afraid that my opinion would not be neutral.
But since most of you are here to build DIY Pass amps, I can always recommend you to adhere to original schematics from Nelson. The added bonus is that the Fairchild parts are much less expensive than the Toshiba's.
Regards,
Patrick
Hi Juma,
I was running the Ono straight into a 25K stepped attenuator, and then into a pair of Aleph 2's, and it did that no problem, so I would imagine the F5, at 101K input impedance, would also be an easy thing to drive.
As for the B1, I'm mostly curious just to try it. I'll probably wire it into a passive source selector with a ladder attenuator, and then add a switch to either add the B1 or remove it from the circuit as needed. I'm not a big fan of running the signal through unnecessary parts, so it will probably spend most of its life unused.
Calvinhpk:
The F5 will still run in class A with a 4 ohm load, but you'll only get half the power available into the 8 ohm load before the amp leaves class A. Just plug a 4 into the equation in place of the 8 - you get 13.5 watts.
Cheers,
Owen
I was running the Ono straight into a 25K stepped attenuator, and then into a pair of Aleph 2's, and it did that no problem, so I would imagine the F5, at 101K input impedance, would also be an easy thing to drive.
As for the B1, I'm mostly curious just to try it. I'll probably wire it into a passive source selector with a ladder attenuator, and then add a switch to either add the B1 or remove it from the circuit as needed. I'm not a big fan of running the signal through unnecessary parts, so it will probably spend most of its life unused.
Calvinhpk:
The F5 will still run in class A with a 4 ohm load, but you'll only get half the power available into the 8 ohm load before the amp leaves class A. Just plug a 4 into the equation in place of the 8 - you get 13.5 watts.
Cheers,
Owen
> I built two versions of my balanced circuit, based on Toshiba's and Fairchild's. Results of both have been published. You just need to go back to those pages
Patrick,
would you mind sharing the schematic of your balanced F5 Toshiba version ? I think i have not seen it some in the thread ...
thx
Mathias
Patrick,
would you mind sharing the schematic of your balanced F5 Toshiba version ? I think i have not seen it some in the thread ...
thx
Mathias
Just a shortish update. The F5 clone I've built went through a few cosmetic changes, got a pair of (unbalanced) XLR connectors at input, added a few 1uF block capacitors over the filter cans and went through some extensive listening in the meantime. I measured the output DC offset which is to my surprise at three zeros @200mV range still... No need to adjust anything... So... Time to start building something new...
You will most likely have to change a couple of values of elements to be able to set it up properly. With +/-25, no additional fiddling is required, so my guess is that even with the extra 6 volts it wouldn't be a huge problem, but the dissipation will most likely increase... I really have huge heatsinks and it maybe is the way to go, (that definitely is) and maybe you'll find out if you try it.
in case of 2sj74/2sk170 as input devices , +/-28V is pretty close to their voltage limits ...... at least during setting procedure , where they could likely see full rails .........
with that rails - you can use mosfet cap multipliers , with benefit ........
that way , you'll loose exactly what's needed - ~ 4V on each rail , with miniscule dissipation increase
with that rails - you can use mosfet cap multipliers , with benefit ........
that way , you'll loose exactly what's needed - ~ 4V on each rail , with miniscule dissipation increase