Yes, and that's how I interpret/know it also.
There have been/are plenty of consumer amps with 'under rated' power supplies.....IOW supplies that sag like hell when delivering higher duty cycle signal.
This brings a bunch of cost benefits for the typical consumer, ie lower cost through lesser transformer, lesser heatsinks, lesser output stages, lesser shipping costs, lesser power rated loudspeakers, etc.....
This under rating of supplies causes significant difference between short term and long term power ratings.
Manufacturers tout this behaviour as advantageous by speccing this as 'dynamic headroom'....high dB figure looks good to the novice !.
For the reasons of cost and neighbours annoyance, this 'dynamic headroom' can indeed be viewed as beneficial.
Dan.
Maybe your definition of 'effective' differs from mine.
The above suggests that two power amp channels in BTL deliver four times the output power level.
Distortion for a 4 ohm load will be much higher at the same output voltage.
Compared to single ended drive, 'effective' continuous output voltage in BTL mode will be a lot less than twice as high.
I'd think it will be a lot higher than that, for this reason => Total Output Power at 1%THD+N : 140-W Stereo into 4 Ω in BTL Configuration, 175-W Stereo into 3 Ω in BTL Configuration
This discussion is about a Class-D amplifier IC which does not suffer the same extent of losses inherent in linear stages.
In the cases of Class-D and linear, if the loadings are say 100R, for BTL the power quadrupling would be very close to ideal/theoretical.
In any case Steve was confused about SE/BTL/PBTL vs load resistance....overview explanation is sufficient in this case.
Dan.
In the cases of Class-D and linear, if the loadings are say 100R, for BTL the power quadrupling would be very close to ideal/theoretical.
In any case Steve was confused about SE/BTL/PBTL vs load resistance....overview explanation is sufficient in this case.
Dan.
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Decent, golden or what?
For a real thrill, put appropriate value resistors between the power supply and the amp circuit to simulate a good amp with a very weak power supply. Do a few DBTs to factor your obvious prejudices out of the outcome as well as you can. and live and learn.
Right and that's why power supply rejection is one of those things that good amps do.
Not so much. I've tried it, and learned.
(1) The power supply voltage wandered all over #&!!.
(2) No audible difference unless at or beyond clipping, which was reduced a few dB. Since most power amps are run well below clipping, no audible difference.
So what amplifier make/model ?.
What value resistors ?.
Where exactly in the circuit were the resistors fitted ?.
Dan.
I did the experiment well over a decade ago, and I don't remember the details.
It would be interesting know a little more detail....surely you can remember something ?.
Dan.
Compare the plots (including the Nyquists) with resistors replacing the drivers. Same LC but quite different results. The impedances with and without baffle show the high frequency loading increases.
It looks to me as if the HF is above the value of the dummy resistor and I don't see lots of extra phase shift on the Nyquist to account for the drop in impedance.
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Exactly, Andrew. People buy a cheap amp rated for 8 Ohms loads when in fact they own 4 Ohms speakers and then wonder why they have no "ooomph" with known demanding music. And let's be honest about it, PSUs are inside the box, they cannot be seen, and thus various designs prefer to invest money into shining LEDs rather than into unseen transformers.
I have retouched only a few amps in my life, but I am happy when I discover there's still enough room inisde for a new bigger transformer. Myself, I'd never use a 150 VA trafo in a nominally 2*50W/8 Ohms amp, but that's what the industry does (at least some of it). And they are none too generous with filter caps either. All this makes the amp run out of steam when it suddenly needs to drive lower impedance loads at prodigious power levels.
Regrading Arny's comment on ideal voltage sources, I beg to disagree. It is quite possible to achieve a true doubling of power in terms of watts, but ti always does come at a cost and a bit of cheating. For a nominally 50/100/200W into 8/4/2 Ohms, it's wise to make what is really say 60/100/180W into 8/4/2 Ohms, as some output voltage drop is only to be expected. The point is the amp will not be ambushed by decreasing load impedance too much.
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The choice of programme material is of importance here also, as per the Amcron music type/duty cycle sheet I posted.
Dan.
Dan.
Arny, our exepriences are obviously different. In my experience, quite a few otherwise fine sounding amps into 8 Ohms loads will lose quite a bit of sound quality even when connected to more nasty 4 Ohm speakers when they are called upon to deliver serious peak power bursts (but within their nominal rated power outputs). The fact is that quite a few designs in fact take into account PSU sagging, and allow for what I feel are criminally high PSU voltage drops. This may make the product more cost effective, but wil do its sound no favors. Kill the quality of the burst and you kill the dynamics of the music. If you hve a feelig of PSU based congestion, as I see it, you lose all around.
Which goes a long way in explaining why audio shows are far too often demonstrated with easy going relatively quiet chamber music. Replace that with say Blue Man Group first CD, which is VERY dynamic, and things change no end. Trust me, I tried it often enough.
That's just far too convenient in the context of this discussion.
Bob Cordell has done a few demos (at RMAF IIRC) where he showed that at realistic listening levels and with a fairly representative speaker, quite big amplifiers clip more than one would expect.
In this scenario, I would find it hard to accept there would be no audible difference between an amplifier that delivered 90 W at 8 Ohms and say 120 or 130 into 4 Ohms vs another exemplar that doubled power into 4 ohms.
I am not saying amps should double power into half the load Z - they should however be able to handle difficult loads. In the first example I quoted above, I would not consider that amp very capable.
Yeah, chamber music is pansy music....proves nothing.
I have a few tracks (eg AC/DC, REM) where old true VU meters stay motionless for long periods...but the music has texture, involvement but no medium/long term dynamics.
This music sorts out the weak amplifiers from the real ones.
Andrew, that's just far too polite.... see post 4639691
Dan.
Anyone interested in listening tests on the effect of power supply should see Jack Walton's excellent article in volume 4 of Linear Audio. This is for preamps rather than power amps, but still has relevance.
The key to getting a significant difference is, unsurprisingly, using a circuit that has poor power supply rejection. Use a circuit which is better engineered to ignore these effects and the criticality goes away.
The key to getting a significant difference is, unsurprisingly, using a circuit that has poor power supply rejection. Use a circuit which is better engineered to ignore these effects and the criticality goes away.
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