The verdict is in - VFET amplifiers are terrible

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#61
Careful listening continues. After trying the Victor with four different Oppo players I've noticed an overall veiling and a high frequency distortion. Since I promised it wouldn't be modified I did a lot of soul-searching about getting the iron out, but it was annoying me enough to do something about it.

The two signal carrying 22uF 25V electros on the plugin amplifier board have been replaced, and things are now right with the world.
 
#64
haiqu said:
Extended listening continues. I'm pretty sure that in the days of vinyl with its inherent backround noise this amplifier would have seemed perfect, but on most low-res digital source material the overlay of the amplifier's character becomes annoying, even if it does sound sweet. I prefer something more accurate myself, but for that I'll have to personally design something better, which is a tall order.

I've also discovered that there's a channel disparity and I've had to push the right channel volume preset about 20 degrees further than the left. I've eliminated all else, it's definitely the Victor. It probably needs a good alignment, but of course there's no data on how to do that anywhere online.

On hi-res sources (24/96 and better) or on low-res sources at reasonably high levels it is as good as anything I've heard. Definitely a keeper, this one.
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An update on the channel level disparity:

I've been using the JM-S7 daily for watching videos and the other night (well early morning really) I had almost nodded off and suddenly the right channel came good. It was so loud it scared the cr4p out of me. I readjusted the volume presets and now have a perfectly balanced amplifier.

My guess is that one of the speaker protection relays was a bit dirty and it finally broke through the oxide layer, but whatever happened there has been no recurring fault, nor is the fix intermittent. So I finally have what I paid for, a perfect working JM-S7 as a daily driver.

I'm surprised at how little needed fixing, given the age of this amplifier.
 
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