I plan to add capacitance to the PS of my amp which is a Parasound New Classic 2125 model. the caps in it now are two 6800uf 80v. 105 degree rated. it has two bridge rectifiers also which are inline packages rated at 8 amp 200v. and also attached to heatsinks. I have ordered two 10,000uf 80v. 105 degree. I also, ordered 8 15 amp 600v. rated stealth diodes also to use to replace the original rect. should I replace the 6800uf caps or, add the two 10,000uf caps in paralell? also, should the new heavier duty bridges need to be heatsunk again?
http://www.enjoythemusic.com/magazine/equipment/1107/parasound_2100_2125.htm here are the specs and picture. Thanks!
http://www.enjoythemusic.com/magazine/equipment/1107/parasound_2100_2125.htm here are the specs and picture. Thanks!
Adding larger caps does not really have anything to do with the rectifier ratings, unless you go insane with absolutely extreme amounts of capacitance.
That's because rectifier diodes have a continuous current rating, and a surge current rating. This means you can actually put much more than the rated current through a rectifier diode for a short amount of time with no ill effects.
As far as which is going to be better sound quality wise, that I don't know.
That's because rectifier diodes have a continuous current rating, and a surge current rating. This means you can actually put much more than the rated current through a rectifier diode for a short amount of time with no ill effects.
As far as which is going to be better sound quality wise, that I don't know.
Hi, Just a couple of points to bear in mind. Adding more capacitance can significantly increase the peak charging current in the bridge as the conduction angle is significantly reduced. This can increase the temperature the mains transformer runs at due to "copper losses" and there is a risk of the core saturating. 6800mf to 10000mf is probably fine but I would'nt go adding much more. These higher currents can also increase any radiated magnetic field, so if hum caused by induced field is a problem this can actually make it worse. Correct layout and grounding is much more important in my opinion. Just be aware of potential problems, more isn't always better.
Regards Karl
Regards Karl
The photo shows a dual mono construction with two rectifiers and two sets of filter caps. What's strange is one cap per channel looks smaller than the other. Is this a single polarity supply with a cap coupled output stage?
If this was my amplifier, I would get the schematic before going any further (actually I would disassemble it and trace it out myself, but I would still get the schematic for reference).
I would also check the data sheet for the new rectifier's 10mS surge current ratings, fast rectifiers have lower surge ratings than 60hz ones. It would need to be 150A to be safe in my mind with the parallel 6,800 and 10,000 combination.
If this was my amplifier, I would get the schematic before going any further (actually I would disassemble it and trace it out myself, but I would still get the schematic for reference).
I would also check the data sheet for the new rectifier's 10mS surge current ratings, fast rectifiers have lower surge ratings than 60hz ones. It would need to be 150A to be safe in my mind with the parallel 6,800 and 10,000 combination.
thanks for all the pointers fellas! I was just surprised when i opened the amp up and it had the same size PS caps as my Adcom GFP 6500 preamp stock, caps which, i'm driving it with. just seems that Parasound cut corners on the power supply putting that size (6800uf) caps in a power amp with the rated specs? makes me feel like i must, be laking in the bass department? even my Onkyo M-282 100 wpc. amp came stock with 10,000uf Nichicon Gold tunes and much smaller, and lighter tranny with 71v. caps which costed $200.00 vs. the $700.00 (retail) price of the Parasound which also, uses Jamicon brand caps? does this make since? or am i thinking all wrong? maybe the large tranny makes up for the smaller caps? thanks for any help clearing up my confusion LOL!
these are the specs on diodes. if i understand correct, these should handle 200 amp surge yes or no? Thanks!djk said:
http://www.fairchildsemi.com/ds/IS/ISL9R1560PF2.pdf
Here is a 6A standard diode from On Semiconductor, notice how the surge current rating is 400A?
http://www.onsemi.com/pub_link/Collateral/MR750-D.PDF
This is why I worry about fast diodes with their reduced surge capacity, I've had them blow up from turn-on surges.
http://www.onsemi.com/pub_link/Collateral/MR750-D.PDF
This is why I worry about fast diodes with their reduced surge capacity, I've had them blow up from turn-on surges.
fast and ultrafast rectifiers don't usually need high surge ratings, because they're used mostly in switching supplies, which ramp up to full power as the caps in the primary charge. the peak current in the primary side bridge needs to be pretty high, unless something like a NTC thermistor is used for a soft start.
Very appropriate, been saying this for age's Commutation noise ( a burst of R.F ) is a very real problem in line frequency (50/60 hz) rectifiers. 100volt rating, way to low. I know we are talking about the secondary side here but think of this, the maths is the same, mains voltage U.K. 240v rms (230 now officially). Peak to peak voltage equals 240 times 1.414 (square root of 2) times 2. Thats 680 volts, so 1000 volt dc rated cap needed.
Regards Karl
Commutation noise ( a burst of R.F ) is a very real problem in line frequency (50/60 hz) rectifiers. 100volt rating, way to low. I know we are talking about the secondary side here but think of this, the maths is the same, mains voltage U.K. 240v rms (230 now officially). Peak to peak voltage equals 240 times 1.414 (square root of 2) times 2. Thats 680 volts, so 1000 volt dc rated cap needed. Regards Karl
1000v! Is that like the 100 year tidal wave? The best I can find from the suppliers here that isn't bigger in physical dimensions than the rectifier is a 47nF 630 Volt Greencap Metallised Polyester, shall I bother? I'm a bit confused is the amp module exposed to 1000v, I thought it cut out at 52v.
Hi Col, 100 Year tidal wave, no not at all, this is steady state operation. The mains is a very spiky place, peaks of up to a couple of thousand volts or more can occur, but their duration is in the 10's of micro second range and fortunately are infrequent. Think of the 'stat in a freezer, or swithing off a vacuum cleaner, an inductive load like that kicks back. Remember that the example I gave was for 240v rms, work it out for your 30-0-30 transformer and it's not quite so bad. Caps for mains use (where they are connected between live and neutral) are nowadays specially designed for this very use, google "class X" and "class y" type capacitors there must be lots of info around to help you. They are also "self healing" which means if a breakdown within the capacitor occurs i.e. the thin dielectric film ruptures and creates a short, the material vaporises and the short is cleared. Old type caps literally exploded violently when this happened. So back to your caps over the rectifiers, 60 volts rms is 170 volts peak to peak, so a 250volt rating is fine for these but try to choose self healing caps if possible.
Regards Karl
Regards Karl
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