I need some advice from the Gurus and Wizards here on the ballpark amount of Microfarads to power filters I can install on a Sansui au-5500 amplifier. It originally had 4,700uf, 50v power filters. This amplifier has 35v rails. I have some 63v 10,000uf Rubycon MXR caps and Im wondering if they would be Ok to try. Any ideas or suggestions are welcome.
They would work but may strain the power transformer at switch on due to the excess current required to charge them from zero volts to 35volts and to keep them topped up whilst working.
Don't you think Sansui would have used 10,000uF if it was needed?
Don't you think Sansui would have used 10,000uF if it was needed?
According to some things I've read the manufacturers in those days skimped on installing bigger power capacitors to save a few pennies. Back then they were expensive.
The question of whether to oversize caps or transformer hinges on how much noise you want to make. If you seldom exceed 50% of your maximum power rating, you won't get much benefit from upping the capacitance to 10,000uF or just doubling the maximum possible charge. If the venerable old Sansui amplifier were such a penny-pinched design, it would likely have had the more expensive transformer reduced first, leaving you with a more difficult and very expensive, if not impractical problem to contend with. As John explained, the transformer is therefore the real power limiter and the caps just needed to be sufficient to maintain enough charge for each cycle's current peak of the output signal. Yes, it's a lot easier, cheaper and a popular activity to replace old caps but any benefit there with up-sizing is more likely to be that they are just new caps. Still, since caps have shrunk over the years since these old amps were built, it may be expedient to use the next size up in order to fill the mounting footprint or solve an availability problem. However, I suggest you don't overdo that by more than 50% of the original value - let's say 4,700uF increased to 6800uF max.
From past experience, I haven't had problems with bumping up that capacitance by small amounts but my transformers have mostly been overkill for the designs. I did burn out one customer's transformer (or rather the fuse buried in the mains winding) when he insisted I fit 22,000uF caps in lieu of 10,000 uF originals though - You don't forget that kind of blunder because it stains your reputation, regardless of who insisted what about the job.
From past experience, I haven't had problems with bumping up that capacitance by small amounts but my transformers have mostly been overkill for the designs. I did burn out one customer's transformer (or rather the fuse buried in the mains winding) when he insisted I fit 22,000uF caps in lieu of 10,000 uF originals though - You don't forget that kind of blunder because it stains your reputation, regardless of who insisted what about the job.
I'm neither but the answer to your question seems to be quite straightforward.
They should be OK. The transformer would squirm if it has very low leakage inductances, like in toroids.
The amp is rated at 30 or 32 WPC and it's very old - 1970s but it has quite a bit of warmth and sweet sounding distortion, making it the favourite among Sansui amplifiers which were early and very popular Japanese products among "audiophiles". They were actually low cost exports and used a small E-I laminated transformer but all that ended in the 1990s when the brand was used on high end TVs and VCRs then changed to Orion Electric with an expanded range of domestic appliances, heaters, ovens etc.
Thanks for the great info fellas, I have decided to leave the amplifier stock standard for the time being with new 4,700uf, Nichicon, KG, GoldTune, caps and try out some 6.800uf caps later on just to see how different this amplifier may sound in volume, quality, etc... Thanks again fellas, your advice, suggestions and ideas are greatly appreciated.