2. amps-preamps
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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

Showing 4 responses by georgehifi

georgehifi's avatar
georgehifi
10,312 posts
 
Some of his amps have very low input impedances.

Yes granted, this is the reason why an active pre is needed, if they were >50kohm then a low impedance active pre is not needed, remember the Industry Standard for input impedance was 47kohm or higher, but sometimes if the input stage is bi-polar this not achievable, but it is with fet input, then it’s up to the designer to make it so.

Classic example of a high end poweramp here in Australia having only 1kohm input impedance, only their own preamp with 10ohm output impedance would drive it, all others especially tube sounded like crap, so no need to say they also sold many premaps with that poweramp.
But here the crux, inside that poweramp was a secrete link that when pulled made it 68kohm input impedance, which I exposed online, then owners were free to use all different preamps with it including passive. It’s called shady marketing, good if you get away with it as it makes sales for their preamps.

Cheers George
georgehifi's avatar
georgehifi
10,312 posts
 
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
georgehifi's avatar
georgehifi
10,312 posts
 

Look at things logically, a horn speakers worst friend is noise, and you have too much gain from the pre and the amp, maybe even the source.

Get rid of the one you think has more noise, the tube pre or the ss amp.
And replace it with a lower or zero gain item that is quiet.

Or you could be back where you started, if you replace a quiet high gain item with noisy low gain item.

Cheers George
georgehifi's avatar
georgehifi
10,312 posts
 
aberyclark
 Low output gain amplifier for ZU 101db Efficient speakers

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:

We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.

Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.

Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.

What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.


You could always trial a Schiit Freya preamp it has virtually no gain (unity gain) itself, in all of it’s modes tube, solid state, or passive output, got remote 3 inputs and balanced or rca, and sounds from reports very very good.

Cheers George
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