In article , Dave Plowman (News) scribeth thus
Sounds like an ideal candidate for an upgrade. Not only do you put new caps in they have higher capacity the 2200 mfd goes to 4700 in the series output, and now its 9400 mfd in the power supply but even the small caps on the boards its worthwhile to change them too!...
80 volts is the *peak* voltage, at the top of the waveform. The wattage delivered to the speakers depends on the 'RMS' (root-mean- square, a sort of average), which is 0.707, (for design purposes; it varies with the waveform) of the peak.
If it ever goes wrong I'd consider that upgrade. But at the moment it does its job adequately.
That's still 400w average power.
There are life issues too, derate working voltage to 60 or 70% of spec and they last 10x longer. Similar issues with temp, 105degC caps last forever when derated.
Spec'd life at max temp and voltage on an electrolytic is rarely impressive.
foolish strategy.
I see HDMI doesnt contain analogue output :/ Trouble with using hardware to keep up with digital standards is they keep changing.
NT
draw =A0an "equivalent" circuit of any amplifier, you will see that the po= wer supply shows as being in series with the load.
r supply. This means that you should choose ps components as carefully as y= ou would for example speaker crossover components or any other component in= the signal path.
t your theory. Hang the cheapest on temporarily.
Actually for a sine wave the mean power is half the peak power. It is the voltages that are in the ratio of 1/root(2).
Not seen the initial postings in this thread as it has only just started being xposted to uk.rec.audio. However, the above depends on details like if the amp is single-rail or dual-rail.
For example, for 100wpc (mean for sinewave) into 8 Ohms you'd need +/- 40V rails as absolute minimum in a dual-rail design. If it were a single rail then you'd need 0V and a 80V rail as absolute minimum. In practice a real-world design would need headroom to drive the devices, so 0 - 80V single rail would get you somewhat less than 100 wpc (sinewave mean). Then if you also take into account that the PSU will probably 'sag' under sustained load you'd find that 80V single rail would be much less when you are trying to get sustained sinewave power from both channels of a stereo amp.
So in practice you might find that 0 - 80V single rail ended up giving you far less than 100wpc mean sinewave stereo. (Although peak levels for music could be somewhat higher.)
And as I see someone else has pointed out. You also would be safest choosing a cap whose spec voltage was well above the actual rail voltage when the amp isn't sagging the voltage. Hence an 80V cap would be sensible for use with a somewhat lower rail voltage.
Slainte,
Jim
Otherwise its about - with PSU sag and a safety margin the square root of two times half the voltage minus about 15v, so 24v rms Or in power terms about 132W into 4 ohms
Unless its split rail with two 80V caps, or an H bridge..in which case yes, its abut 400W.
?
wrong:
Oh dear. I guess the 16 years i spent designed audio power amps was completely wasted?
Fairly ordinary domestic power amps run with +/- 40 or 50 v rails.
80v rated caps would not be unreasonable.The full rail voltage won't appear on the output ( unless the one of the Output Devices have gone S/C ).
on
Youre fond of asuming too much
"fred"
** That is complete nonsense.Electro life is not related to DC operating voltage, unless the rated limit is exceeded then it is VERY short.
** Also complete nonsense - there is little increase in expected life using 105C types unless the local ambient is over 75C.Electro lifespan is all about the quality of the airtight seal in the end of the cap - cos the end of life occurs when most of the electrolyte has escaped as vapour through an imperfect seal. The rate of loss of electrolyte is a function of the local ambient temperature and ripple current ( if any) heating the electro.
105C types can operate at higher temps, that is their only advantage.Long life electros come in both 85C and 105 C types - all that is different is the quality of that seal.
..... Phil
"The Natural Philosopher"
** That is a bit optimistic.
Adding this up we have:
74 - 9 - 2 - 5 = 58 volts peak.So the "rms" power on sine wave into 8 ohms will be 210 watts.
..... Phil
No. 58 volts peak TO peak.
No, slightly over 50W.
Ok I see you are talking about split rails. I read the above too quickly. I don't think the OP mentioned that he had split rails.
So your analysis is correct for what equates to a +-60V supply.
However I have yet to see that sort of power and arrangement outside some pro audio kit.The semiconductor cost is pretty high above 100V.
?
wrong:
To be a pedant - its not a strategy, it was a heuristic ;-)
When you think that an amplifier is in its simplest analysis a voltage (or current) modulated variable output power supply, you appreciate the PSU is a fairly critical part that is actually in circuit with the load.
Fairly NON critical part actually. Since the feedback that controls the output is taken from across the load, not the power supply.
That is the trouble with 'simplest analyses'..
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.