Hello,
I recently started working on a hafler DH 500.
I was planning on upgrading the power capacitance from the stock twin 20k uF capacitors with four 20k uF capacitors.
I was wondering if anyone could give me an idea on the proper wiring for this modification. I don't want to get the polarities mixed up.
Also,
Would a 40amp 600v rectifier bridge be sufficient for that much capacitance? (total of 80k uF)
Or would a 40amp 1000v rectifier bridge (block) be better?
I want to be careful with the start up surges and turn off pops.
I am planning to bypass each of the large cap with a 10-50uf capacitor / thinking Mylar film or elect. And a parallel resistor to assist with voltage drain.
Would doing all this add to much ESR? I think that's what someone mentioned in another post.
Any advice or thoughts will be greatly appreciated.
I recently started working on a hafler DH 500.
I was planning on upgrading the power capacitance from the stock twin 20k uF capacitors with four 20k uF capacitors.
I was wondering if anyone could give me an idea on the proper wiring for this modification. I don't want to get the polarities mixed up.
Also,
Would a 40amp 600v rectifier bridge be sufficient for that much capacitance? (total of 80k uF)
Or would a 40amp 1000v rectifier bridge (block) be better?
I want to be careful with the start up surges and turn off pops.
I am planning to bypass each of the large cap with a 10-50uf capacitor / thinking Mylar film or elect. And a parallel resistor to assist with voltage drain.
Would doing all this add to much ESR? I think that's what someone mentioned in another post.
Any advice or thoughts will be greatly appreciated.
The two existing electrolytics will have a +ve/-ve identification, somewhere.
You can check that ident using a voltmeter when the amp is powered ON.
You just need to maintain the same polarity when you fit the extra capacitors.
The voltage only needs to be high enough to prevent charge passing back through the rectifiers.
What voltage are your capacitors?
A bridge rectifier with slightly higher than double the cap voltage is sufficient.
i.e. for 63V, 75V & 80V capacitors use a 200V, bridge rectifier.
For 100V & 150V capacitors use a 400V bridge rectifier.
80mF total capacitance is OK for 25A bridge rectifier. 35A may run a tiny bit cooler.
BTW, a ClassA Power Amp will probably need a rectifier heatsink. Your Hafler is ClassAB.
Therefore I would buy the cheapest 25A 400V bridge rectifier I could find.
I bought about 50 off, about 6 years ago and I am down to my last dozen.
I use 3, or 4, in each power amplifier build.
Use a soft start to limit start up current.
Use a speaker isolator to delay speaker connection @ start up and instant off when power fails. No odd speaker noises !
Do not fit low esr caps across your electrolytics. They cannot do any good and may make things a lot worse.
Instead, look carefully at how your amplifier uses local supply rail decoupling.
You can check that ident using a voltmeter when the amp is powered ON.
You just need to maintain the same polarity when you fit the extra capacitors.
The voltage only needs to be high enough to prevent charge passing back through the rectifiers.
What voltage are your capacitors?
A bridge rectifier with slightly higher than double the cap voltage is sufficient.
i.e. for 63V, 75V & 80V capacitors use a 200V, bridge rectifier.
For 100V & 150V capacitors use a 400V bridge rectifier.
80mF total capacitance is OK for 25A bridge rectifier. 35A may run a tiny bit cooler.
BTW, a ClassA Power Amp will probably need a rectifier heatsink. Your Hafler is ClassAB.
Therefore I would buy the cheapest 25A 400V bridge rectifier I could find.
I bought about 50 off, about 6 years ago and I am down to my last dozen.
I use 3, or 4, in each power amplifier build.
Use a soft start to limit start up current.
Use a speaker isolator to delay speaker connection @ start up and instant off when power fails. No odd speaker noises !
Do not fit low esr caps across your electrolytics. They cannot do any good and may make things a lot worse.
Instead, look carefully at how your amplifier uses local supply rail decoupling.
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