Agree with the above comments, especially in terms of the priority/order in which things ought to be done. Go ahead and replace that old power cord--but do the other stuff first. Could be a very satisfying project!
- ...
- 34 posts total
Be careful with your acceptance of advice! When choosing the values of a power supply's filter caps, it's important to understand how the supply/circuitry functions. ie: When a DH-120 is switched on: the capacitors initially present (what appears to be) a dead short to the amp's 8A (OEM) rectifier bridge. The greater the filter capacitance: the higher the current necessary to charge the caps. Increasing the capacitance beyond a certain point, in most amps; it's easy to end up with blown rectifiers (possibly: a burnt transformer). Of course: much of the above depends on how well the amp is protected, but: too much capacitance is simply asking for trouble. It's always been my practice, when addressing power amp improvements (50+ years now), to first upgrade the rectifiers/rectifier tube/bridge, as that's always made the most marked/audible uptick in presentation. WHY? Because, in most cases: manufacturers don't use the best/most expensive parts they can find. An increase in filter capacitance can reduce ripple in a power supply, but: going too far can change (decrease) conduction angles, increase peak currents and result in EMI/noise generation, in/from SS rectifiers. The harmonics of that EMI/noise can easily defeat any performance gains, gleaned from ripple reduction. https://electronics.stackexchange.com/questions/217212/how-can-i-observe-rectifier-switching-noise
+1 for the rest of that post, of course. |
So, with a big, heatsinked 35 amp bridge i have put 1/4 Farad (eread that again, yes F) in a DH-200. and if you do blow it up its $3 online for a new bridge. So a giant "meh" to the worries.
That said the comments are true. There WILL be a bigger inrush. I would either build a slow-turn on circuit (series R, parallel relay, 15V trigger for coil) or place an appropriate surge-suppressing NTC varistor in line with it. They will absorb the surge with maybe 5 ohms, then cool back down and drop to near zero. Work great, cheap, easy. There’s an opposite approach possible with a PTC unit. I would insert a link, but every time i try to help out the mods here block my link thinking it must be a way to circumvent Audiogon making money on a sale :-(
realityu note: the 1/4F was a "hero experiment". Way past diminishing returns. But i’d go for 30-50,000 uF ( at as i recall 63V or higher). That ought ot make it sing. Bypass each (across the terminals) witha 100V dc film type which will have dialectic absorption ( the big sonic parameter) of roughly 50-100x better than a typical electrolytic.
|
In my book: informing another on ways to prevent catastrophic failures (ie: upgrading rectifiers, etc), BEFORE they cause them (ie: by installing biggest capacitance possible), is simply sagacious, but- that’s just me. A transformer failure is a real possibility and much more expensive than $3.00. But then: why should YOU have, "worries", about THEIR results, right? ie:
|
- 34 posts total