moving swiftly
Tekko, Tekko, Go Go Go 😀 . I see you have decided to test the formula. All the best, awaiting data. Hope she drips chocolate for you.
Tekko, Tekko, Go Go Go 😀 . I see you have decided to test the formula. All the best, awaiting data. Hope she drips chocolate for you.
Well no such luck.
I tested it on 2x35VDC but it does not work, goes up to +20V ou the outputs, with a full line level signal it starts jumping between 20V and the positive rail.
I dunno if its a board error or a misplaced resistor value. When touching the board in strategic locations i can get it to swap to the negative rail and/or make it oscillate.
I tested it on 2x35VDC but it does not work, goes up to +20V ou the outputs, with a full line level signal it starts jumping between 20V and the positive rail.
I dunno if its a board error or a misplaced resistor value. When touching the board in strategic locations i can get it to swap to the negative rail and/or make it oscillate.
Turned out to be the input transistors, forgot that BC557 and 2N5400 has reversed pinout.
I still have a problem though, i cannot bias the amp with the proposed 6.8k resistor, i have to add another 12k across it to get in range, but when i add any bias, the amp starts to oscillate :/
Did yoiu actually build this irl to make sure it works of did you rely on ltspice only ?
I still have a problem though, i cannot bias the amp with the proposed 6.8k resistor, i have to add another 12k across it to get in range, but when i add any bias, the amp starts to oscillate :/
Did yoiu actually build this irl to make sure it works of did you rely on ltspice only ?
A video: SYMEF by OnAudio - YouTube <-- without those two bodge resistors, it just goas straight up to around 1A bias no matter the pot position.
And as you can see, adding any kinda bias maes it oscillate and sound generally bad.
And as you can see, adding any kinda bias maes it oscillate and sound generally bad.
Oscillations cured!!
The 39pF caps on the predrivers are miswired, they are supposed to go between B and C of the predrivers, not between B and GND.
I solved this by scraping off the traces that went to GND and instead replaced them with a short piece of wire going to the rails, that fixed it, no more oscillations!!.
The fix on schematic: http://i.imgur.com/KIaAM.png
The 39pF caps on the predrivers are miswired, they are supposed to go between B and C of the predrivers, not between B and GND.
I solved this by scraping off the traces that went to GND and instead replaced them with a short piece of wire going to the rails, that fixed it, no more oscillations!!.
The fix on schematic: http://i.imgur.com/KIaAM.png
Last edited:
Hi Tekko,
Thank you for all you have put in making it work. Could you send me close ups of top and bottom.
kind regards,
Harrison.
Thank you for all you have put in making it work. Could you send me close ups of top and bottom.
kind regards,
Harrison.
I hope these are good enough:
Top: http://i.imgur.com/A8tqb.jpg
Bottom: http://i.imgur.com/kQLlC.jpg
Top: http://i.imgur.com/A8tqb.jpg
Bottom: http://i.imgur.com/kQLlC.jpg
Doubtful, the zobel only catches stuff on the speaker outputs that can make the amp unstable suich as long speaker wires and complex crossovers.
If the amp itself is unstable, the zobel has no effect at all.
If the amp itself is unstable, the zobel has no effect at all.
Hard to judge with just one channel, i'll build the second channel and setup a test in stereo. However despite the dinky little test psu consisting of two 2x12VAC 80VA transformers wired up for 2x24VAC, the amp still goes louder than i can stand without clipping.
Keep us posted and thank you for the contributions that you are making in improving the state of the art. 
Congratulations, Tekko!🙂
I envy you because I hadn't got free time yet to assemble my boards.
So, how does it sound?
I envy you because I hadn't got free time yet to assemble my boards.
So, how does it sound?
- Status
- Not open for further replies.