Panasonic SA-XR10 vs SA-XR45/70

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With all of the hype surrounding the new Class T amplifier technologies ive decided that I want to purchase a unit that I can compare against my other systems (loudspeaker & headphone).

Would it be a good bet to buy something like the Panasonic SA-XR10 as a starter item and go from there? or am I wasting my money on the SA-XR10 and should just get an SA-XR45 or 70?

As an aside, I know that the headphone jack on most receivers is derived from the main output channels but with electronics in place to change the impedance and output. Does anybody know if the above mentioned units will carry their supposed good sound quality to the headphone jack also?
 
Well I have a xr10, and can tell you that the differences between each of the amps is minimal . Here's my breakdown of the differences. Most of this stuff is correct, and someone can reply if I'm wrong to any of it.

Power supply
Differences between the xr10 and the 45 on the powersupply side are slim, I think the xr10 lacks one small transformer near the power cord that the 45 has. Also, xr10 uses two smaller main transformers, while xr45 uses only 1 bigger one. Xr70 is similar to the 45, but main transformer and smaller one right next to it is bigger and there are protection relays (which apparently degrade sound) for the speakers are on the p/s board as well according to wayne from Boulder cables on audiocircle. xr25 and 50 power supplies lack the extra filtering that the 10/45/70 have, and the 50 still has the protection relays for the speakers.

Amp section:
45 and 25 use identical amp sections; headphone and subwoofer are handled through a dac i believe (found if you search through one of the old xr10 posts), xr10 uses straight from front channels for headphone, and not sure on sub-out. only difference for 25/45 to 50/70 is that for the front two channels there are different ti power chips used. From what I've read on avsforum and audiocircle, headphone out on the 45/25 and 50/70 are not good. I have the 10 and I don't think it sounds bad at all, better than my Rio Karma (which sounds similar to an Ipod because they use the same DAC/headphone amp chip). JRC makes the headphone op-amp on the xr10, not sure what is used on the other units. Oh yeah, there is also copper grounding inside the xr10, I don't know whats in the other amps.

Analog/digital in's:
nothing special about this, I know that the xr10 is rated 5db higher for analog s/n ratio, 90 instead of 85 for the rest of them. there is no digital out on the 10, but there is on the rest of the series. The 50 and the 70 add another coax out and the 70 adds hdmi.

If I had my choice on what to buy right now, I'd still choose an xr10. This is because they can be had for less than $140, and I feel they're better built than the 25 and 50 mostly because of the more robust p/s section. The 45/70 are better, but good luck trying to find the 45, they are not making them anymore and are still in demand, so probably won't get one for less than $250. the 70 is over $340, but new.

Another reason to get the xr10 is that digital amplifiers are fairly new, and only a handful of manufacturers sell them. I'd say get the xr10 now and ride the wave until these products mature in a year or two. Plus by then hdmi standard will have been finalized, one of the things debated about the 70 (it does 1.1 hdmi input, but only 1.0 output, so it can only pass-thru video, not sound and video.) If you really wanted to go all out and get an amp to last you a while, get this fancy sharp digital amp which cost a couple thousand.:

Sharp SM-SX100
 
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