A number of posts have been removed while the Moderation team decides what action(s) to take. Please take all personal discussions to somewhere other than the forums.
Thank you.
Last edited:
BF862
Does anybody have LTSpice model for BF862? Or is there something else that is reasonably close?
Does anybody have LTSpice model for BF862? Or is there something else that is reasonably close?
I just used ElFishi's model for this BF862 preamp. Change R4 to 50k to get it to work without clipping.
http://www.diyaudio.com/forums/pass-labs/146310-bf862-preamp-48.html#post4925674
The BF862 makes a nice headamp. 4 in parallel has good driver capability.
http://www.diyaudio.com/forums/head...f862-based-se-class-headamp-without-heat.html
I guess you know there is a build thread.
http://www.diyaudio.com/forums/pass-labs/283387-f5-ha-build-thread.html
And a private forum.
Please use those for the build.
Thanks,
Patrick
http://www.diyaudio.com/forums/pass-labs/283387-f5-ha-build-thread.html
And a private forum.
Please use those for the build.
Thanks,
Patrick
i built the vero board version on post 1 but with 2sk246 j103 pair and the mosfets do not heat up at all.
i get good sound but nothing to be excited about.
the mosfets are not being biased properly for sure.
how can i fix this?
i get good sound but nothing to be excited about.
the mosfets are not being biased properly for sure.
how can i fix this?
Referring to :
http://www.diyaudio.com/forums/group-buys/271926-f5-headamp.html#post4282959
Note the different feedback network.
Increase the value of R3 & R4 until you measure about 0.5V across R7, R8 (3.3R) to 0.5V.
Then you will have about 150mA bias at the output stage.
The 2SK246 / 2SJ103 based circuit, as already mentioned, has much higher noise and higher distortion.
About 10x.
Patrick
http://www.diyaudio.com/forums/group-buys/271926-f5-headamp.html#post4282959
Note the different feedback network.
Increase the value of R3 & R4 until you measure about 0.5V across R7, R8 (3.3R) to 0.5V.
Then you will have about 150mA bias at the output stage.
The 2SK246 / 2SJ103 based circuit, as already mentioned, has much higher noise and higher distortion.
About 10x.
Patrick
Yes i built your suggested circuit and it works fine, as does the original one with k170, and they both sound wonderful!
My problem was with turning the bias knob the wrong way.
However i do have a problem with turn on thumps with mine. Im using mr evil's cap multiplier, 17v +/-.
My problem was with turning the bias knob the wrong way.
However i do have a problem with turn on thumps with mine. Im using mr evil's cap multiplier, 17v +/-.
Last edited by a moderator:
I have turn on thump with mine. Everything's star grounded, dead wuiet at all volume...
The only difference from the original is that the gate stoppers are 2k ohm on mine. And once again, using mr evil cap multiplier at 16v +/-.
I also have turn off thump. Little quieter than turn on thump.
How can i trouble shoot this?
The only difference from the original is that the gate stoppers are 2k ohm on mine. And once again, using mr evil cap multiplier at 16v +/-.
I also have turn off thump. Little quieter than turn on thump.
How can i trouble shoot this?
That means your power supplies are likely to be powering up asymmetrically.
One is up fast than the other.
How to solve this, you'll have to ask the guy who design your power supply circuit.
We don't have that problem with ours.
Patrick
One is up fast than the other.
How to solve this, you'll have to ask the guy who design your power supply circuit.
We don't have that problem with ours.
Patrick
PS A slow-start relay as in our headamp protection circuit will only save your switch-on thumb.
It won't solve your switch-off thumb.
Patrick
It won't solve your switch-off thumb.
Patrick
But you can add loss of AC detection circuit for this. Rod Elliot has a very nice one which works well.
Project 33 (c) Rod Elliott
But this has to act before (one of) his supply goes down during turn off.
No idea whether that is the case.
Patrick
No idea whether that is the case.
Patrick