It may not be super critical, but it is a challenge! Those pots are extremely sensitive, but if you meditate and take up deep breathing exercises for three days prior, give up coffee and drink herbal tea, and learn to bend blades of grass with your mind, you can in fact get that bias at 12 volts. Don't give up so easily!
About fine tuning the pots: once you get close to the mark, stop trying to 'turn' the screwdriver, and do little 'taps' (like a chisel-type tap). Wait a couple secs for it to stabilize, then tap again.
Eventually, it reaches the value. Turning them will overshoot every time.
Hope this helps, best regards,
Rafa.
Eventually, it reaches the value. Turning them will overshoot every time.
Hope this helps, best regards,
Rafa.
When I first built the ACA, (2012) I would just tweek the pot to get symmetrical clipping. I noticed I wasn't getting consistent THD @ 1W numbers. Only after I started tweeking to a specific Voltage, did I get more consistent measurements. Slight changes in quiescent Voltage affect THD above 1KHz (ver 1.0) as I documented in post 576 of this thread. I used 10 turn pots on all my builds.
How does the raise in THD above 1KHz affect the sound ? I have ask the question a couple of times and never got an answer.
How does the raise in THD above 1KHz affect the sound ? I have ask the question a couple of times and never got an answer.
Regarding stability?
Don't know…...but maybe some has experience from real use of both types.....
Maybe one like heat better then the other etc.....
The single turn is cheaper but if a "steady hand" can adjust it.....then it should be OK I guess. Think it was just that conclusion I was after….or hoped for
Don't know…...but maybe some has experience from real use of both types.....
Maybe one like heat better then the other etc.....
The single turn is cheaper but if a "steady hand" can adjust it.....then it should be OK I guess. Think it was just that conclusion I was after….or hoped for
Yes, it is working although I do not have a pair of speakers set up that I can easily integrate this into. So no idea on sound but through my test setup good so far. After I get the second built I'll know for sure.
Thanks for all the replies and assistance all, much appreciated.
Getting a start on my ACA
Milled board using engraving bit on rotary tool in small drill press to set depth. Board in pic not yet fully stuffed - got some terminals to put on and standoffs so that all weight not carried by IRFP240s.
4x heatsinks 80x80x100mm - they are salvaged off thyristors left over in a industrial transformer(?) case that my father is repurposing for the control box of his solar array.
All in all bit of an experiment - hopefully the heatsinks will be big enough. Originally was trying to configure the heatsinks like V-Twin motorbike because they look like little cylinder heads but that was just getting too complicated.
Will report more as it comes together.
Milled board using engraving bit on rotary tool in small drill press to set depth. Board in pic not yet fully stuffed - got some terminals to put on and standoffs so that all weight not carried by IRFP240s.
4x heatsinks 80x80x100mm - they are salvaged off thyristors left over in a industrial transformer(?) case that my father is repurposing for the control box of his solar array.
All in all bit of an experiment - hopefully the heatsinks will be big enough. Originally was trying to configure the heatsinks like V-Twin motorbike because they look like little cylinder heads but that was just getting too complicated.
Will report more as it comes together.
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Excellent!! Congratulations on your ingenuity. I'm sure you will be extremely pleased with the end result.
Yes, I’ve been thinking it might be fun to repurpose an old dead BGW 250 I’ve had for years.
I might be able to achieve 24 V by using the 220 Volt primary wiring at 120 V.
Lots of heat sink area available in these oldies.