Killers of Class AB (STA-9 review)
(Saga in 3 parts)
Cultural shock of Diophile
As preambule I will explain one simple rules. If you didn't understand few words in my review - take a look in Remarks in the end. I'm sure it will help.
It's not correct to call STA-9 Power Amp as "digital". Yes, it's Class D, but more corrective way to call it as "switching" amp.
You may find plenty information regarding ideology, theoretical basements and constructional features of NuPrime products on their site, I am not going to duplicate it here.
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Can you imagine Power Amp in Class D with tube-like sound? Total control over the speakers, nice tubey sound,
small weight, catching price (in comparison with convinient Power Amps). If you can - my congrats! I couldn't. That why I decided to arrange audiotion of STA-9 in my Room with my Equipment.
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I received only 1 unit in the beginning and it was my epical fail. I spent 3 days in vain later, because we had
long term holidays and my dealer couldn't contact to distributor matter to add fuel in my fire-chamber.
The second amplifier should acted as added fuel. I've rited like shaman to my dealer using Skype:
"Just give me another brick in the wall!!!"
Do you know what I had on my face almost 3 weeks during audition of STA-9? Radiant smiling from ear to ear.
Everything what I want from this Amp - I'll get it immediately and without standard sound collateral damage!
But let's brake my running before the steam train and start from the beginning.
My first familiarization with Class D Power Amp happened in Mykolayv City a month ago when I made visit to one my fellow,
also music lover. 3 small frameless electronic plates with size like box of matches each lay on table and demonstrate total
control over the old speakers of Sansui brand. Dominic Miller from album 2003 "Shapes" (Decca 475-479-2) confidently laid out things in their right places, positions and orientation.
I've been quite impressed after 3 minutes of audition and decided to dig deeper in this matter. Further gathering of information and a combination of circumstances led me to the products of the NuPrime brand.
Ability of STA-9 to obtain endless new layers from musical records, which you guessed properly stored in memory
already many years, is absolutely amazing. I discovered so many things, I have to rewrite all files in my brains now and
even to start the defragmentaion because I'm possessed by perfectionism.
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Peter Gabriel 2002 "Up": I never heard such bass from my Audio Physic Avanti in this room. And even more -
I never heard the resonance of my room in low band! I always suspect that my Power Amp T+A (model A1500) is not able to control
my speakers properly. Situation is dangerous for old T+A 'cos I am living on 8th floor and Power Amp doesn't have
wings. Gothic joke.
Gabriel's songs compilation 1990 "Shaking the Tree": it's quickly becomes clear for me - this feathery amp can
develop the phenomenal sound spaces. You don't need to strain your ears to hear, Gabriel with Levin sing in 2 intervals on "Mercy Street". This unison's singing usually seems as one vocal only on the entry level Audio Systems.
Texture of bass from the Renaud Garcia-Fons 2001 Navigatore: delicious, like home cooked Ukrainian https://en.wikipedia.org/wiki/Borsch t" target="true">borscht.
This record contains many various acoustic instruments, which grounding on famous quality of ENJA recording label,
reveal another typical feature of STA-9 - never do the squash in sound.
Vocal localization - another firm feature of amp. Vocals never will stick in the speakers or be mixed up with music,
it will occupy position in the audio space, exactly where recording engineer or sound producer ordered to place.
On epical record of Johnathan Elias 1999 The Prayer Cycle, track 7, where singing of Nusrat Fateh Ali Khan and Ofra Haza supported by The English Chamber Choir I could easily find singers' positions: Ali Khan - on left side, Ofra Haza - on right side.
My T+A Power Amp couldn't do it in same unerring manner. And this feature - one of the biggest between Amps in Classes AB and D. You may see how sound producer or recording engineer located vocals in space, nerve-endings of your hearing apparatus never will be overloaded by useless calculations, only sound pleasure will be supplied into your relaxed brains.
I've never heard the album of brazilian Lenine 2006 (no album's title) on such level of comfort. That's made really crazy!
If any new appliance increases the resolution - bad quality records become less comfortable. Not here. Do gentlemen from NuPrime brand become proficient in black audio magic or I've suddenly got the portion of puriest audiophilic electrones and should pray my electrical company like a hell?
Soundstage is moved backward on distance 2-3 feet thus if you keep Audio Rack with appliance between speakers I
advise to make audition of STA-9 at your home before purchase.
The pair of STA-9 almost totally controled my Audio Physic Avanti. Keep in mind, these speakers are not
ease loading - 86 dB/W/m and 4 Ohms! But this little baby with weight 3.80 kgs (there is mistake on NuPrime site -
4.75 kgs are appointed) and dimensions 235 (W) x 281 (D) x 55 (H icluding feet) mm kept Audiophysics in
iron gloves and didn't permit any kind of wheeze.
STA-9 can work in bridged mode, power jumps to impressive 290 Watts on 4 or 8 Ohms! It's not mistake, it's feature of Class D. Reconnection of speaker wires and change of position of proper switcher on the rear panel will be required.
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Difference in sound between stereo and bridged modes:
- temperature of amp's body is much less in bridged mode;
- LF band comes deeper, overtones of string instruments become full-bodied;
- dynamic increases radically, I could listen music at night time using speakers without ear to disturb neighbours;
- tube-like coloration of sound is higher, good discernible in LF band.
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Very special LP (special because it's an Analogue Productions) Roger Waters 1994 Amused to the Death (2LP)
just launched me on Heavens.
RCA: Un-Balanced input x 1
XLR: Balanced input x 1
Stereo Speaker Out x 1 or
Mono Speaker Out x 1
Power: 2 X 120W / 1 X 290W @ 8 & 4 Ohms
Peak Output Power: 2 X 280W / 1 X 320W @ 8 & 4 Ohms
Input Impedance: 47k Ohms
Input sensitivity: 232.8mV, 1W @ 8 Ohms
Gain: x 22
Signal to Noise Ratio: < -95dB at 1W, 10W, 100W
THD+N: 0.02% (Stereo) / 0.01% (Mono)
Frequency Response: 10Hz to 50kHz
Worldwide AC voltage: (115 VAC / 230 VAC) with Voltage Select Switch
AC Fuse: Slow-blow, 3A, 250VAC
Dimension: 235 mm W x 281 mm D x 55 mm H (including feet)
Weight: 4.75 kg
Color: Black or Silver
In a 110V outlet, the idle-power consumption is below 14W. In a 230V outlet, the idle-power consumption is below 16W.
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- weight. It's comfortable. Just imagine how easy to visit your lovely Fellow. Don't forget to fix his jaw before audition. Medical plaster will be ok;
- power and ability to control heavy loading;
- bridged mode;
- ratio "sound quality/price tag" goes to Infinity and falls in the black hole of
my present review Revelation in the end;
- beautiful tube-like coloration. Old fashioned music lovers who posessed by tubes in amps will be mind-blowed;
- all that - from youngest model. I'm already jumping on coach only thinking about audition of ST-10 and Ref 20. (This review was writtem before Nuprime's release of STA-6).
There is plenty material on NuPrime's site, I highly recommend to read it all.
- Unfortunately I could not connect 2 pairs of speakers wires (types spikes) even after connectors from 1 pair were removed.
Sizes of STA-9 speakers connectors are too small. Probably it ca be done using "spades" on 1 pair of wires;
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- Reading of manual for people with weak vision will be not comfortable, almost all drawings are pale.
Actually it will be quite enough to read again the name of my saga. Amplifiers in Class AB will follow the path of dinosaurs.
And let me end on an such optimistic note.
- - -
Remarks regarding few neologismes:
1) Diophile - it's shortening from word "Audiophile".
2) Congrats - congratulations.
Original review with many photos are here.