I would be verry verry surprised if they used the same supply voltage.
Typically when you double the power you will need to use a supply voltage
about 1.4 times as high and in the case of a class A amp you would also
need to use a bias that's about 1.4 as high too.
Typically when you double the power you will need to use a supply voltage
about 1.4 times as high and in the case of a class A amp you would also
need to use a bias that's about 1.4 as high too.
- If we look at the specs for the 30.8 and 60.8 we can see that the 30 is half the rated output of the 60.
- We also know that the 60 is internally bridged since its mono and use two output cards in series/Chn while the 30 is a stereo amp and use only one output card/Chn.
- The 30.8 use 20 power FETs/Chn while the 60.8 use all 40 power FETs/Chn
- Both the 30 and 60 have rated power consumption of 370W (374W in some documents).
- Class A envelope for the 60.8 is 122W and 61W for the 30.8 in 8 ohm. 61 is exactly half of 122
>>> While doing so, the power supply can remain the same with the same supply voltage <<<
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Well, I used a tool which is available to anyone and that is Ohm's law and by using Ohm's law together with the rated output power, of any amp, we can arrive at current and voltage at any given resistance and when I do that, I have to conclude with that the XA30.8 and XA60.8 does not use the same voltage supply.
I'd toss in one more assumption. You would need to assume that the limiting factor for rated power into 8R is voltage clipping for both amps. That's a fair assumption, but it should be mentioned. If you back calculate from specs, you can determine (as you mention) Vrms at the max power rating (and assume that is at the PSU voltage limit).
30W / 8R - ~15.5Vrms => ~22Vp
60 / 8R - ~22Vrms => ~31Vp
31/22 or 22/15.5 => ~1.4 ... See post #2
Class A envelope is generally a function of quiescent current. I don't think it's relevant to your original question of voltage supply, but it's fun to talk about. All you really needed was #1 in your list to make a good guess as to the answer.
I think you have it sorted, but in summary...
Since you also have the dissipation, and you can assume that the voltage output is 1.4x different, you can make a few other assumptions... based on your points 2-4.
30 - 370W / 15.5Vrms => ~24A
60 - 370W / 22Vrms => ~17A
One perhaps could assume that the Iq per device in the 30.8 is 24/20 and in the 60.8 is ... 17/40
I didn't look up the specs of the amps, nor do I know how they're constructed or their topology. I was just using your numbers above.
Fun stuff.
As always... I participate to learn. Above may not be correct. I'm batting about .501, which for DIY ... means I should probably read more.
30W / 8R - ~15.5Vrms => ~22Vp
60 / 8R - ~22Vrms => ~31Vp
31/22 or 22/15.5 => ~1.4 ... See post #2
Class A envelope is generally a function of quiescent current. I don't think it's relevant to your original question of voltage supply, but it's fun to talk about. All you really needed was #1 in your list to make a good guess as to the answer.
I think you have it sorted, but in summary...
I would tend to disagree. They 'could', but it's not likely. If the 30.8 used the same higher voltage supply as the 60.8, it could still be rated at 30W, but then the assumption of voltage being the limiting factor at 8R would be incorrect. Who knows? We have to make some logical assumptions.
I would tend to agree.
Since you also have the dissipation, and you can assume that the voltage output is 1.4x different, you can make a few other assumptions... based on your points 2-4.
30 - 370W / 15.5Vrms => ~24A
60 - 370W / 22Vrms => ~17A
One perhaps could assume that the Iq per device in the 30.8 is 24/20 and in the 60.8 is ... 17/40
I didn't look up the specs of the amps, nor do I know how they're constructed or their topology. I was just using your numbers above.
Fun stuff.
As always... I participate to learn. Above may not be correct. I'm batting about .501, which for DIY ... means I should probably read more.
Thanks for shimming in @ItsAllInMyHead, its appreciated. I'm learning at a distance and its fun to poke at stuff. Since these amplifiers have been out for a decade or so, one would be free to actually measure the amps, at the supply and at the rail, which I am sure some have. But I don't have access, so kinda have to speculate.
Now, using 8 ohm ratings for both amplifiers:
XA30.8 delivers 90W according to Desmond at PASS. Ohm's law dictate that we need 26.83Vdc and 3.35A.
XA60.8 delivers 150W according to Stereophile. Ohm's law dictate that we need 34.64Vdc and 4.33A.
Using the 1.414 conversion + diode forward voltage drop to reach the Vac supply voltage, we get:
Tran SEC Vac for XA30.8 = 26.83Vdc / 1.414 + 0,6V = 19,54 or around 20Vac
Tran SEC for XA60.8 = 34.64Vdc / 1.414 +0.6 = 25Vac.
These numbers are without any losses in the system and is purely mathematical
Now, using 8 ohm ratings for both amplifiers:
XA30.8 delivers 90W according to Desmond at PASS. Ohm's law dictate that we need 26.83Vdc and 3.35A.
XA60.8 delivers 150W according to Stereophile. Ohm's law dictate that we need 34.64Vdc and 4.33A.
Using the 1.414 conversion + diode forward voltage drop to reach the Vac supply voltage, we get:
Tran SEC Vac for XA30.8 = 26.83Vdc / 1.414 + 0,6V = 19,54 or around 20Vac
Tran SEC for XA60.8 = 34.64Vdc / 1.414 +0.6 = 25Vac.
These numbers are without any losses in the system and is purely mathematical