Pre-Amps - Classic 100 Series

Model no:   QA-115-Mk4 / QA-115-Mk4-Super
C$2,480 Untitled Document [US$ 1984] / C$2,980 [US$ 2384]




line stage full balanced pre-amplifier (super version built with IR+BT remote volume)

Using the 6SL7/6SN7 tubes as the amplification, and 6L6G tubes as the output buffer section, this unit is also built with a 5U4G tube rectifier and enhanced power supply, (which gives you the best price-performance in a fully balanced pre-amplifier). All hand-wired to the highest possible standard. With the flexible capability of over 600 different tube combinations, you can easily fine-tune the tonal quality of this pre-amp to adapt it to the rest of your system.

This pre-amplifier has a special HD (high definition) selector, it simply transform the internal circuit designs, and can give you a very high adaptability to different types of music. When HD is "ON" , it is good for dynamics Rock, Pop , Symphony and Jazz, while "OFF" is good for soft Blues, Vocal and Chamber music. It can also use to match different system characteristic and give out most natural musical performance. Even though this switch can change the dynamics and pace of the music reproduction, the alternation can't be detected by any existing measuring instrument. The specifications will not be altered, the changes are only detectable by the human ear.

This MK4 version are newest design with our special "micro-dynamics extraction" (MDE) circuit , which can achieve super quiet background with exceptional instrumental separations which we believes no others can offer, and let very weak music information effortlessly surface out right in front of you. So details, high density with texture and vivid. You can hear the movement underneath the throat of the singer, and the fingers of those violinist or guitarist touching the strings as in real life performance.

Standard chassis is a plexiglass+Aluminum hybrid design, which can balance between asthetic, reliability and tonal quality. Optional chassis of all aluminum or MDF with same price. Super heavy aluminum or solid-oak chassis option with additional cost. (Super version built with solid aluminum enhanced chassis)

This version also equipped with the compatibility of NOS EL32(VT52/CV1052) and their compatible tubes, which can let you experience the wonder sound of this exotic tube without any adapter or modification.

(Super version is EL32, KT120 and KT150 ready with enhanced power transformer upgrade, infra-red and bluetooth remote controllable volume pot, rectifier tube upgraded to 274B )

Space-Tech Lab. blue-tooth remote volume App for Android phone.

Customer feedback: (from Stephen)

Received preamp this past Friday, and have been enjoying the music immensely!
I am very pleased that the dynamics and live quality are exactly what I was looking for.
The gain is very powerful, and there is that beautiful tube warmth similar to my boutique tube guitar amp.
I still don't have the spatial depth I seek but after moving my speakers to a more ideal
placement, this aspect was much improved. I just have to revamp the rest of my system, and work
on even better speaker placement. The digital PS Audio sounds much improved, more open but still compresses the music too much...

I have been listening to a Ted Leo album a lot this summer, but now I hear all the subtleties of his
use of the Echoplex effect in his guitar playing. I have played around 25 cds the last few days
and am hearing new details and information which I have never heard. My old Denon mastered
Charlie Parker Cds have been brought to life! My Van Morrison Universal Japan SHM CDs sound sublime...
played Veedon Fleece twice and the musical poetry brought me to tears. This preamp begins to
bring back the emotion to the music which I have been missing

QA-115-Mk4-RM-1 QA-115-Mk4-RM-1

Now also available are super rectifier tubes up-grade STR-104 , STR-1001 and STR-1002, which can greatly enhance the dynamics, high and low frequency extension, and bass punch. A stand-by switch for pre-heating of the rectifier tubes ensures the longest operation for the lifetime of the tube. Rectifier tubes are replacable with high quality ceramic sockets installed.

STR-104 super rectifier C$880

With this super rectifier adaptor, you can use 300B, 2A3 , 45 , 50 , 80, 83, 1616 , 3B28 or 866A as rectifier tubes option.

No. of inputs 2 sets of  RCA inputs and 1 set of XLR balanced inputs
No. of outputs 1 set of RCA and 1 XLR balanced pre-amp outputs
Freq response 1Hz - 60Khz (-3db)
S/N > 90 db ( max. output level)
Input impedance 86Kohm (option: from 10Kohm to 1Mohm)
Gain x3- x6 depend on tubes
Phase 180deg inverted (option: non-inverted)
manufacturing hand-wired point to point

2 x 6SL7(Alt: 6SN7/6SU7/ECC32/ECC33/ECC35/6188/5691/5692 or equiv)

+ 2x 6L6G (Alt: 6V6/6K6/6G6/6F6/EL34/5881/6550/KT66/KT88/KT99/KT100 or equiv )

+ 5U4G (option:5AR4/5V4G/5R4/274B/53KU/STR-101/STR-104/STR1001/STR-1002)

(Super Version comes with 274B rectifier, and can use KT120 and KT150)

(Note: The upgrade price below is a special deal for new orders only, due to more works are needed for disassemble of the original circuits, modification of previously built unit will be around $300 higher than the following prices, )

Level 1 upgrade : (+ C$200)

Special designed "Super-Drive" circuit, output impedance lowered to 200ohm (can drive any power amp inputs from 600ohm up to infinity) with better bass control and punch , better definition and improved in overall tonal quality. By adding this upgrade, it sounds like the output with 10 pieces of power tubes being installed .


1 year parts and labor warranty under normal operation conditions
standard chassis : plexiglass + Aluminum hybrid chassis

(optional chassis : Mirror steel, black piano , solid-oak , MDF ..etc )

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Save the earth and save yourself, be a vegetarian and keep enjoying music for a long long time !!