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Power Rating: Onkyo vs Yamaha

Hi, everyone!

I am browsing for an integrated amplifier and I stumbled upon the Onkyo A-9150, that meets all my requirements (budget, good sound, discreet class AB design, internal DAC, pre-out, phono, the whole package), but I am really curious by its power rating.

Looking at the specs, it is rated as 60W/4-ohm and 30W/8-ohm with 0.08% THD from 20 to 20,000Hz. Okay, but the manual also states that it weighs 9.2 Kg, almost the same (even heavier) as the Yamaha A-S301, that weighs 9.0 Kg. Only the Yamaha is rated as 60W/8-ohm and 70W/4-ohm with 0.019 THD from 20 to 20,000Hz. Upon inspection of pictures over the internet, their transformers are pretty much identical, just like their chassis, and 

How come is this difference in power so big? Any ideas?

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PS.: If you look in their service manuals, I guess you will find that their topology is the same and that the Onkyo A-9150 amplifier transistors are even more powerful than the Yamaha A-S301's.
rafapb
kosst_amojan
2,095 posts
 
The Yamaha is clearly the superior unit. If that’s the distortion it makes driving 60 watts into 8 ohm, it’s certainly less at 30 watts. Probably half the distortion in fact. That’s the general behavior of push-pull topologies. And if you’re driving an 8 ohm load at 30 watts, you’ve got 70 watts of overhead into impedance low points instead of just 60.
The lower capacitance reserve in the power supply may be justified if it’s being regulated in some fashion. The significantly lower distortion does suggest a better engineered power suppy. They Yamaha clearly operates higher voltage rails and provides more current.
A more critical analysis is required beyond the observation that an amp can double it maximum output power.
secretguy
199 posts
 
My experience with Yamaha is that they have the weakest "watts" of anything I’ve ever owned. I avoid at all costs now. Coincidentally, I bought an Onkyo 9110...the littlest brother of their line...for a budget system for my wife. The thing sounds better that it has any right to at anywhere near the price,
rafapb OP
5 posts
 
Sorry, I made a mistake! Actually the Yamaha is not rated for minimum RMS power for 4-ohm, but for 6-ohm (and 0.038% THD).The numbers for 8-ohm are alright.

The lower capacitance reserve in the power supply may be justified if it’s being regulated in some fashion. The significantly lower distortion does suggest a better engineered power suppy. They Yamaha clearly operates higher voltage rails and provides more current.

I am definitely no expert, but for what I have seen in the service manual (very superficially), the power supplies seemed very similar to me. And the voltages indicated in the power amplifier section were 40 V for the Yamaha A-301 and 37.5 V for the Onkyo A-9150. I don't know if that difference is significant to that point.

Is it possible that the Onkyo has some kind of gain adjustment to leave current headroom on purpose?

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PS: I also noticed that the idling current adjustments are different: the Yamaha asks for 1-10mV on the emitter resistor, while the Onkyo asks for 20-30mV. Maybe there's something in that, but I just don't know enough to make something of this.
mesch
1,679 posts
 
What speakers are you going to pair this integrated with? I suspect that these integrateds are similar in there ability to drive speakers, and neither are meant for speakers difficult to drive. I am not familiar with the Onkyo, only the Yamaha which I think to be very good at it's price point. Both are full function integrateds.
rafapb OP
5 posts
 
What speakers are you going to pair this integrated with?

I intend to pair them with Tekton Lore References. They should work great, but knowing they can handle so much more power, it is tempting to try and squeeze something more out of this Onkyo unit. I feel it should be able to output more than that, but I don't know why it can't.

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