General Asylum: REVIEW: Space-Tech Laboratory QA112sp Preamplifier (Tube) by Branwell

Model:	QA112sp
Category:	Preamplifier (Tube)
Suggested Retail Price:	$610.00
Description:	Tube Preamplifier
Manufacturer URL:	Space-Tech Laboratory
Model Picture:	View

Review by Branwell ( A ) on March 25, 2002 at 17:17:11
IP Address: 207.172.109.148

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Hello,
For those interestedâ€¦â€¦â€¦â€¦.
A while ago, I read on these forums about a little preamp from a less them well known company from Canada called Space Tech. Being in the market for another preamp, and not really wanting to spend silly money, I ordered a model called QA-112sp.
This pre has a larger power supply than the standard QA-112 and only has a pair of input and output's, i.e. no selector switch. ( space tech will built you a pre to what ever spec you want ).
The preamp is basically a simple tube design that uses the 6SL7GT tubes for amplification and comes with Sovtekâ€™s. Its also has a tube rectifier, the 6X5GT. The one supplied is a Sylvania.
After break-in, the sound was very impressive for a $650.00 preamp. Certainly better then many of the higher priced units available.
Saying that, I like modifying things and this pre just felt like it had all sorts of potential.
Mod timeâ€¦â€¦
There are several capacitors in the design, some in the signal path and others not.
So, out came the stock caps and in went a variety of quality caps.
Signal path capacitors:
I played with various makes, like Hovland, VTV, Jenson, North Creek Crescendo, SRC and Auricap.
While other preamps I have liked a mix, I ended up with Auricaps everywhere.
Power supply caps:
The power supply, like most has several large value electrolytic filtering caps. These I bypassed with 1uf Auricapâ€™s and then bypassed again to the active device with .1uf Auricaps.
Sound:
At this point, things where dramatically improved. All areas where substantially cleaner, better focused and tonally correct.
Still more mods:
While I had done everything I could about most caps, I still had the cathode bypass cap that was a large value electrolytic. I tried to bypass this with a small value polypropylene cap, a .1uf and while it was improved, there was still a little grunge in there.
Again, coming back to the forums, I read about using a rechargeable battery in place of the caps and resistors that bias the tube cathodes.
So, out came the stock setup and in went a Sanyo 600ma SCRC NiCad cell. One per output tube.
Sound:
I have had this setup for 48 hours now and am just delighted.
Over the past two years I have had the following preamps in the system.
From Audio Reserch the SP-9 and SP-11. The P.S. Audio 4.5, a Bottlehead Forplay with all the mods and a Transcendent Grounded Grid.
Non of them can come close to the transparency, delicacy and speed of this pre.
Soundstage:
The soundstage is fantastic. Its as wide tall and deep as the music demands. It expands way outside the speakers, goes back through the rear wall and even projects images behind the listener.
In past experience, most preamps seem to have a soundstage limit they place on the music. Basically, the preamp has only so much room to cram all the instruments. If itâ€™s a big band, things get squished. With the modified QA-112, the bigger the band, the bigger the soundstage.
Detail:
The interesting thing about this pre is how it can maintain detail on each instrument regardless of how many instruments are being played. Again, it does this better than any pre I have heard to date.
Tone:
Tone really is an area where many system are let down. To me, most systems give them selves away on human voices and wind instruments. Again, the little QA-112 gets these textures exactly right.

Conclusion:
I have heard many systems, used to sell hi end hifi gear in England, used to have a small company that built monitors for recording studios and can honestly say, with the exception of several very expensive custom made specials, I have not heard a commercially available preamp that can touch the little QA-112 with mods.
My advice, if you have a Space Tech, get out your soldering iron.
If you arenâ€™t into modifying things, the stock QA-112 is still very satisfying and great pre for not much money.

Branwell

Product Weakness: For me, non.
Product Strengths: Good performance stock, amazing performance modified.

Associated Equipment for this Review:
Amplifier:	Altivista NP-100 power amp
Preamplifier (or None if Integrated):	QA-112
Sources (CDP/Turntable):	Norh CD-1 cd player
Speakers:	North Creek Rhythm Revelator
Cables/Interconnects:	Vandenhul D-102mkIII interconnects, Alphacore Me 1 & 2
Music Used (Genre/Selections):	All
Room Comments/Treatments:	None
Time Period/Length of Audition:	1 month
Type of Audition/Review:	Product Owner

Product Weakness:	For me, non.
Product Strengths:	Good performance stock, amazing performance modified.