Hugh R. Dean's 
System
Date of "Visit":
27 September 1999


the system and its master


Glass Harmony power amp


close-up


water cooled (!) Glass Harmony


Libra Audio

e-mail to:
Hugh R. Dean


I have been fascinated by electronics since early childhood, and frustrated by an inability to penetrate the science of circuit design until quite recently.  After a military career I resolved to learn audio design, and spent nine months in a repair facility working with a highly experienced guru who guided me in the design of tube and SS amplifiers.   He had been a roadie with Pink Floyd and knew most of the ropes, his experience was extraordinary and wide ranging.   Sadly he did not hold hifi in great esteem!

My 28W rms monoblock Glass Harmony amps were designed over a three year period.  Voltage amplification is handled by an octal 6SL7 twin triode, while current amplification is by a single-ended mosfet output stage.  Each channel dissipates 150W of heat continuously.  No global feedback is used;  frequency response is 3dB down at 25Hz and 75KHz.  The interface between the tube and the output stage was a particularly difficult technical problem and easily consumed two years.  The amp has vanishingly low output impedance, and sounds very powerful, but has stunning resolution and refinement.  It is quite possible to distinguish different samples of the same tube from a short listen.  I believe it is this detail which brings out the emotion in the music;  this is an amp which makes you weep, particularly on female vocals.  These amplifiers are now a commercial product, built to order.

Recently I designed and built up a dual mono water cooled version of the Glass Harmony, dissipating a total of 600 watts of heat and producing 55W rms per channel.  This amplifier is visible in the picture, and delivers an even more effortless performance with no loss of detail or refinement.  However, the cooling system is more akin to a hospital than a home, and while this is my "benchmark" amp, it is not practical.

The speakers were developed by a friend in the Melbourne Audio Club;  they are three way with a passive radiator, a second order crossover.   They use a Scan tweeter, a B&W midrange with Al 160 micron spun aluminium cone, and a Scanspeak 170mm woofer with excursion modified to +/- 7mm.  They are 3dB down at 32Hz and 22KHz, of 90dB/watt/metre.  Their bass is astonishing.

The unmodified Denon CD Player  is now the weak link in the chain.   I do have a Lux glass platter turntable with a Stax arm and a Grace cartridge but am not using it at present.   I recently designed a transformer coupled, differential analogue output stage for a recently acquired Crystal CS4390 evaluation board, and hope to complete it by year’s end. 

I enjoy a wide variety of music, ranging from classical through modern jazz to popular.  I particularly enjoy orchestral music, Northern European jazz and acoustic rock.  I believe that a hifi system is approaching nirvana when it makes you weep. 

System's Components
 

Turntable:

None in present use

CD Transport:

Denon CDP-1015

Line Preamp:

None

Power Amp:

Glass Harmony 55W single ended hybrid, with liquid cooling

Speakers:

Libra Audio 3 ways with passive radiator

Interconnects:

Neutrik RCAs, 6 stranded 24SWG teflon coated silver wire (self made) 

Speaker Cables: 

Stax 

Accessories:

Large Sofa

Hugh's comments about his System:

AA: "Hugh, how would you describe your system's sound?"
HD: "The system sounds very large, very involving, and sensuous.  I realise this is sonic colour, but it is conferred by the tube and absolutely no-one seems to object.  In fact, they like it very much, and all want to sit down and spend time listening to their favourite music."
AA: "Do you think there is room for improvement?"
HD: "But of course!  This is my personal art form, and there is always room for improvement, even when I cannot tell you where it needs improving!" 
AA: "Have you got plans for upgrading?"
HD: "Yes.  A tube output stage (6SN7) for the Crystal DAC, a refit of the room (it is very "live") and in time a good MC preamp for my turntable."

 

 

Hugh Dean's
ASPEN AMPLIFIERS
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