Low output gain amplifier for ZU 101db Efficient speakers


I am thrilled with my new Rogue RP-5 preamp. However, like I mentioned before, the tube Hiss is really loud (I can hear back of room). It’s a smooth, non noisy hiss. I chatted with Rogue and they are sending replacement tubes but guess it’s due to my Nuforce STA200 amp with output gain of 34db. I was told that was quite high for having such efficient speakers. Rogue told me they test their equipment on high efficiency Klipsch speakers and the RP5 is quiet.

Anyway, I have attenuators coming today to help until I now find a power amp. I would love to have an Atma-Spere amp, however, they are too pricey for my budget (even used). Maybe a used Firstwatt f3 or these Quicksilver monoblock amps that are made for high efficient speakers http://quicksilveraudio.com/products/horn-mono/

The lower priced Decware amps look nice, plus they have gain settings.

For those who own high efficiency speakers with a tube pre, any other options? I really hate to switch out the RP-5 because it has all the functions available on the remote and it sounds great.


aberyclark
"   One thing I could also do is go to a high end passive preamp. "

which I offered to you to try and sent you a message, but you never got back to me.     would have been really no money out of your pocket except for return shipping.....


With speakers that are over 98dB there's really no advantage in having a preamp with gain, as you've found it's a diadvatage, you'll find many now are starting to go for passive preamps as per this Nelson Pass quote:
George I heard Nelson say basically the same thing in an interview but then he qualified it by saying that his amps sound better with an active preamp. He basically said that it’s an unexplained phenomenon. 
Honestly, with that much gain in the pre-amp, all you really need is an impedance converting amp. You don't need an amp that provides ANY voltage gain given the extreme sensitivity of those speakers. You're close to getting away with running the output of the pre-amp straight into transformers and right into the speakers. The amp I'd be looking for would be one, maybe two, stages at the very most. It would have a mediocre damping factor of 15 or 20. 20 watts through those speakers would literally deafen you in very short order. It's not hard at all to get VERY respectable distortion out of a single ended design with the kind of power you need. Speakers like those are EXACTLY the kind of speakers Nelson Pass had in mind when he designed the F4. The problem with the F3 is it has a low input impedance that might not mate well with a tube line stage and it's got a weak damping factor. But, it does have some modest gain you might want. The problem with all the old First Watt amps is Nelson only builds 100 of them. They're like hen's teeth to find and they tend to find homes they never leave. The upside is you can build you an F3 or F4 for about $1000, and if you don't like either, it's a very small investment to just yank the amp boards and mount new ones; like maybe $200-250. That's a hell of a deal for a totally different amp. The J2 is still for sale and that's well known as being an excellent amp for Zu speakers. In any event, it would be worth looking over the specs for those amps at the First Watt page and maybe reading through the owner's manuals. Those are the kinds of specs you're going to be wanting to look for. Modest power, mediocre damping factor, decently high input impedance, possibly single ended, low noise. I wouldn't sweat crazy low distortion numbers because you're not going to be needing so much power that the distortion will rise much. 
I have read a couple of faverable reviews with the J2 paired with ZU speakers. RENO hi fi has a couple demo j2s for sale
He qualified it by saying that his amps sound better with an active preamp. He basically said that it’s an unexplained phenomenon.

Of course he did, that’s one of his bread and butter items, he’s not going to shoot himself and his company in the foot, left himself an "out" by saying "an unexplained phenomenon" BTW Where is this quote?

Cheers George