2. amps-preamps
  3. 131822-10803

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
hifiron
102 posts
 
:+1: on the Decware amps for high efficient speakers. They're dead quiet (especially the Torii/Torii Jr/MiniTorii) and sound amazing!
aberyclark OP
1,355 posts
 
Last week one buddy loaned me his First Watt M2, another loaned me his Schiit Freya preamp. Using both now on my Zu. Dead quiet. And I can open the volume all the way (with some quiet ditties) with the louder gain tube option, ergo has a built in governor of sorts. The combo btw sure is tasty.



Can you compare and describe the sound characteristics of both amps with your zu's?
aberyclark OP
1,355 posts
 
My RP-5 arrives at Rogue today. Hopefully, they can fix the super loud white noise (plus buzzing in headphone section). My goal is to keep the RP-5

I'm updating my power amp by the end of the year regardless how quiet the RP-5 comes back. I'm keeping my ZU omen defs. I really want a tube power amp. I also understand the firstwatts are fantastic.

Anyway, here are the specs for the RP-5:

- Tube complement: 4 x 12AU7/ECC82 tubes
- Frequency response: 1Hz – 100KHz +/- 1 dB
- THD: <0.1%
- Gain line stage: 10 dB
- Rated output: 1V
- Maximum output: 27V RMS
- Output impedance: 500 Ohms
- Gain phono stage: 40dB, 50dB, 55dB, 60dB
- RIAA accuracy: +/- 0.1 dB
- Dimensions: 18.5 ”W X 4.5 ”H X 14.5” D
- Weight 30 pounds
- Shipping weight 45 pounds
- Power requirements 115/230V – 50/50Hz


For reference, the specs of my current amp:

-GeneralPower output80W x2Ch @ 8 Ohm
-Input impedance51k Ohm
-Output impedance30m Ohm*
-Gain34.8dB
-Frequency response20Hz - 80kHz
-Sensitivity0.45Vrms
-Signal to noise ratio100dB
-Total harmonic distortion<0.03%
-Power supply115 / 230V
-Power consumption3.15A/ 1.57A
-Nominal input level0.6V

Now, with the above specs in mind, along with buying blind (I'll make sure there's a good return policy). What amp specs should I be looking at for low noise and good matching with the RP-5 and Zu's? I'm not looking for brands...just specs where I can at least narrow down my choices. I'm not worried about having high power. The 80 (SS) watts I currently have is more than enough for my speakers. 

I know my current amp does have high gain (34.8) for my system, however, with my old Peachtree Nova, the amp hiss was only audible if I placed an ear on tweeter.

Here are the Nova Pre specs:
Variable RCA Stereo Output: 7V rms/11.2V peak •
Pre Out 1 Output Impedance: 50 Ω (discrete class A) •
Pre Out 2 Output Impedance: 15 Ω •
S/N at the Variable Analog Output: 96db •
Jitter Measured at the Master Clock: < 3.0ps •
Power Supply: 8700µF of filtering •
Stereo Separation: 94db • Maximum Power Consumption:
60W, standby less than 1W


Thanks for your help. Looking forward to responses. Once I hear back from Rogue, I will report their findings



addyson815
240 posts
 
"   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.....


seanheis1
619 posts
 
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. 
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