Can this really be Class A & SE?

WithTarragon · 2nd June 2008, 05:27 PM

I was looking at the Monarchy SM70 amp. This is a stereo amp that is claimed to be 40watts, Class A and Single Ended. Those last two features would be two strikes against it being efficient

However what confuses me is that the heat sinks are at most only about 4 by 11 inches (each on a side). There is no fan.

When I look at the good work that is being done here, I see much more massive heat sinking for much less output. Is this manufacturer playing a "numbers game" about the performance and design. I am asking in this forum, since the responses are more knowledgeable and honest.

Thanks for your thoughts

peufeu · 2nd June 2008, 05:43 PM

I see it specced @ 2x 25W RMS in 8 ohms and something like 40W RMS in 4 ohms, so are you certain it really is single-ended ?

analog_sa · 2nd June 2008, 05:58 PM

Quote:

Originally posted by WithTarragon
This is a stereo amp that is claimed to be 40watts, Class A and Single Ended.

Who has made this claim? It appears to be neither class A nor single ended and the Monarchy site certainly makes no such claims.

WithTarragon · 2nd June 2008, 06:15 PM

Let me clarify. I am referring to the SM70 (not the SM70Pro).

You are correct, the output is 25watts/channel at 8 Ohms.
Printed on the amplifier cabinet it clearly reads "Pure Class A"
The Single Ended claim I can no longer find on the website; however, they do list magazine reviews where the reviewers refer to it as "single ended". The Monarchy website has these reviews , but perhaps they are not responsible if the magazine got it wrong.

In either case, even at the claimed 25 watts, the heat sinking seems small. That is what I am confused about.

Thanks

peufeu · 2nd June 2008, 06:18 PM

The very large "Pure Class A" on the front plate would be an indication

But for the single endedness, yeah, I doubt.

Well 25 WRMS in 8 Ohms is 35W peak, so this gives 2A peak and 17V peak, a pure class A amp with 2A idle current and (say) +/- 20V supplies would dissipate 80W per channel... you'd need a 0.5°C/W heatsink which is compatible with the dimensions you quote (9 cm * 30 cm). I have a heatsink in my supplier catalog which is 10cmx30cmx4cm and listed as 0.3 °C/W.

Stefano · 2nd June 2008, 09:45 PM

Hi folks!
The monarchy is single ended in the input stage but it uses a push-pull topology in output stage as you may read in an old (1999 I think) issue of Audio Electronics written by G. Galo

2nd June 2008, 06:15 PM	#4
WithTarragon diyAudio Member Join Date: Jun 2007	A clarification Let me clarify. I am referring to the SM70 (not the SM70Pro). You are correct, the output is 25watts/channel at 8 Ohms. Printed on the amplifier cabinet it clearly reads "Pure Class A" The Single Ended claim I can no longer find on the website; however, they do list magazine reviews where the reviewers refer to it as "single ended". The Monarchy website has these reviews , but perhaps they are not responsible if the magazine got it wrong. In either case, even at the claimed 25 watts, the heat sinking seems small. That is what I am confused about. Thanks

2nd June 2008, 09:45 PM	#6
Stefano diyAudio Member Join Date: Jun 2002 Location: Cagliari, Sardinia	SE Hi folks! The monarchy is single ended in the input stage but it uses a push-pull topology in output stage as you may read in an old (1999 I think) issue of Audio Electronics written by G. Galo __________________ Let's make something special

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2nd June 2008, 05:43 PM	#2
peufeu diyAudio Member Join Date: Mar 2001 Location: Lyon, France	I see it specced @ 2x 25W RMS in 8 ohms and something like 40W RMS in 4 ohms, so are you certain it really is single-ended ?

2nd June 2008, 06:18 PM	#5
peufeu diyAudio Member Join Date: Mar 2001 Location: Lyon, France	The very large "Pure Class A" on the front plate would be an indication But for the single endedness, yeah, I doubt. Well 25 WRMS in 8 Ohms is 35W peak, so this gives 2A peak and 17V peak, a pure class A amp with 2A idle current and (say) +/- 20V supplies would dissipate 80W per channel... you'd need a 0.5°C/W heatsink which is compatible with the dimensions you quote (9 cm * 30 cm). I have a heatsink in my supplier catalog which is 10cmx30cmx4cm and listed as 0.3 °C/W.

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