building a couple of v1.8s
looking at the wiring picture... don't understand where the two, black, twisted wires go from center of ground bus :-/
looking at the wiring picture... don't understand where the two, black, twisted wires go from center of ground bus :-/
A couple hundreds of volts off won't matter at all. Just make sure are setting the bias when the amplifier is at thermal equilibrium which won't happen until about an hour after its turned on. I use the same process Nelson has set for the other Firstwatt projects: set bias pots to min up on initial power on, let it warm up for a few minutes and set the bias "close" but on the lower side. Then return in an hour and set it again.
...But it's not Bias. It's DC midpoint, and won't effect the total heat or operating point in the same was as an adjustable bias will.
That said, setting it warm is a good idea. Rechecking once everything is totally to temp is also a good idea. Set to approximately 1/2 of the rail voltage. Close is good enough, micrometer not required. 🙂
That said, setting it warm is a good idea. Rechecking once everything is totally to temp is also a good idea. Set to approximately 1/2 of the rail voltage. Close is good enough, micrometer not required. 🙂
both ACAs are now down at work 🙂
connected as Balanced monos:
- no power ON thump
- extremely clean sound
- very good detail
- "quite (more than) a tad" on the cold side of neutral (compared to... my beloved SIT 3
)
- good bass. on the lean side but definitely there (Cornwall III speakers)
- one, *maybe*, plays a little louder than the other one ("image" is slightly off center). but never played this album before so... who knows?
in conclusion... I'm very happy (and proud 😉 )
... oh... both powered by an LPS (underneath the left ACA) I built a couple of years ago while waiting for the kits to arrive
connected as Balanced monos:
- no power ON thump
- extremely clean sound
- very good detail
- "quite (more than) a tad" on the cold side of neutral (compared to... my beloved SIT 3
)- good bass. on the lean side but definitely there (Cornwall III speakers)
- one, *maybe*, plays a little louder than the other one ("image" is slightly off center). but never played this album before so... who knows?
in conclusion... I'm very happy (and proud 😉 )
... oh... both powered by an LPS (underneath the left ACA) I built a couple of years ago while waiting for the kits to arrive
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ok... swapped ACAs left/right and one definitely plays *slightly* louder
(things get better, difference being veeeery small, once they are fully warmed up)
then tried bridged mono and... "the quietest" one is almost dead quiet 🙁
guess I have a wiring issue, right?
(things get better, difference being veeeery small, once they are fully warmed up)
then tried bridged mono and... "the quietest" one is almost dead quiet 🙁
guess I have a wiring issue, right?
Try one ACA at a time as a Stereo amplifier. Not bridged or balanced. Do they both play properly? I.E. are all four modules working.
Did you fit new 3 position switches on your build?
Pictures of the internals please.
Did you fit new 3 position switches on your build?
Pictures of the internals please.
... for stereo I must use SE inputs, right?
yes: using a three way ON-OFF-ON switch (or is/was it the other way around? :lol: ). anyway... the kind jim told me to use 😛
pictures... tomorrow. I'll try stereo now
yes: using a three way ON-OFF-ON switch (or is/was it the other way around? :lol: ). anyway... the kind jim told me to use 😛
pictures... tomorrow. I'll try stereo now
Yes one input to the Red RCA and one input to the White RCA. Switch in the middle (Off) position.
... and a speaker to each pair of output connectors of course.
... and a speaker to each pair of output connectors of course.
ok, tried stereo on both ACAs: one is fine one is not 🙁
on the "quiet one" one channel doesn't work
not working channel follows the output: right channel if connecting right speaker to right outputs, left channel if connecting left speaker to right outputs
swapping SE inputs left/right doesn't change the above
on the "quiet one" one channel doesn't work
not working channel follows the output: right channel if connecting right speaker to right outputs, left channel if connecting left speaker to right outputs
swapping SE inputs left/right doesn't change the above
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both LEDs are lit and when I did set DC midpoint everything was looking the same on both boards
so... some bad connection to in/out "ports" and, I guess, issue is with right outputs
so... some bad connection to in/out "ports" and, I guess, issue is with right outputs
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btw... the good ACA, in stereo mode, sounds... wonderful!
image is perfectly centered, coldness is gone and bass is fully there 🙂
image is perfectly centered, coldness is gone and bass is fully there 🙂
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Sorry I do not understand the statement.
On the 'bad' side check the input resistance and output resistance.
Meter on 20k range, check the centre to outside ring of the RCA, should be about 50k ohms.
Meter on the 2k ohm range, check the resistance from the red to black speaker terminals. Should be 500 to 1000 ohms.
Compare to the good example.
Then we need to see pictures. Will be something simple.