Are they two separate isolated power supplies? Or is it one power supply with two 0V connections
it is a single transformer with two secondaries, each has its own rectifier and CRC filter. the 0v output of the supplies are connected together through two CL60 thermistors, with the chassis connected between the thermistors
cheers
mymindinside
cheers
mymindinside
Hi
I've been away for a few days, so haven't made any progress.
p.s Thanks Rob for posting the photos 🙂
Im going off day after tomorrow for two weeks, and was hoping to have it sorted before i left....🙁
keep the thread updated with your progress!
cheers,
mymindinside
keep the thread updated with your progress!
cheers,
mymindinside
The RCA's are isolated from the case. what i meant was that the preamp/source has the left and right RCA ground connected together and that is the only direct connection between the grounds of the two channels.
the other connection is the one from each 0v rail to the chassis through a CL60 (nominal 10 Ohm) thermistor.
hope that is clearer
cheers,
mymindinside
the other connection is the one from each 0v rail to the chassis through a CL60 (nominal 10 Ohm) thermistor.
hope that is clearer
cheers,
mymindinside
Once upon a time I drove trucks for a second job which required tying down loads with ropes etc, a wise fellow once told me "If you can't tie knots, tie lots".
So what I am saying here is try absolutely everything (ie process of elimination). Then once you solve your problem, try and understand the problem.
So what I am saying here is try absolutely everything (ie process of elimination). Then once you solve your problem, try and understand the problem.
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That's good advice, i have tried a few possibilities. the most successful was to tie the signal grounds of both channels together at one star, and have a wire going from this star to each channel's pcb. the 0v rail went directly to the channel pcb. this left a much quieter hum which bothered me only in quiet passages during critical listening but every time i heard it i felt that i needed to fix it and do a proper job on my amp!
does my wiring scheme look ok to you?
if i remove the input cable from the preamp, there is absolutely no hum.
if i remove the connection to safety earth (i know this is not safe as a permanent solution, i was just trying it to see if it fixed the problem) the hum remains unchanged.
any ideas?
cheers,
mymindinside
does my wiring scheme look ok to you?
if i remove the input cable from the preamp, there is absolutely no hum.
if i remove the connection to safety earth (i know this is not safe as a permanent solution, i was just trying it to see if it fixed the problem) the hum remains unchanged.
any ideas?
cheers,
mymindinside
As far as I can tell you have wired it up exactly like the F2 is wired up.
Maybe the problem is your preamp.
Maybe the problem is your preamp.
Are you saying, chassis earth remains but each individual star ground is floating independantly of each other.
Yes, chassis remains earthed but the circuit is floating. it didnt help the hum so i re-connected the 0v's to chassis via thermistors
will try using a mini to rca input cable and my ipod as a source without the pre and see if it helps
cheers,
mymindinside
will try using a mini to rca input cable and my ipod as a source without the pre and see if it helps
cheers,
mymindinside
Good thinking
Just one more thing. Are you sure that all your mosfets are isolated from the heatsink?
One more thing what type of rectifier diodes are you using (some of them need silpads to be isolated from the chassis)?
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mosfets are isolated with mica washers. the rectifiers are 35A bridges, not discrete diodes but the square package with 4 tabs on top and a mounting hole through the center. i havent isolated these 🙁
Just tried it with an ipod. there is no hum with the mini-2xRCA cable attached but the (loud) hum returns as soon as i plug in the ipod...
im baffled.
im baffled.
i think i posted as you typed, the hum remains when using just the ipod but is quiet if the ipod is disconnected but the cable plugged into the amp. this cable has a miniplug at one end, which has just one terminal for ground so it connects the grounds together even without the ipod being plugged it. shouldn't the amp hum with just the cable connected?
EDIT: with the ipod connected, if i disconnect one of the RCAs from the amp the hum goes away. As i understood, the loops were formed in the ground connections of the components. the miniplug has one terminal for ground, and it is plugged into the ipod; how can removing one channel's input get rid of the hum?
EDIT: with the ipod connected, if i disconnect one of the RCAs from the amp the hum goes away. As i understood, the loops were formed in the ground connections of the components. the miniplug has one terminal for ground, and it is plugged into the ipod; how can removing one channel's input get rid of the hum?
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If i connect one channel to my pre+cdp and the other direct to my ipod i get clean hum-free music in both channels. now i need to work out how to get clean sound with one source 🙂
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