Hafler DH-220 with Musical Concepts PA-6 Ultra mod NEW PICS!

Musical
Concepts modded Hafler DH 220 Amplifier (125WPC)

 

Classic David
Hafler creation, DH 220 amplifier modded in 2017 by John Hillig of Musical
Concepts.  The PA-6 Ultra Modification is
Musical Concepts top of the line mod. It turns this classic amp into a
remarkable amp. From the Musical Concepts site:

http://www.musicaldesign.com/Haf_pwrmods.html

  

Our new PA-6
raises the bar in every aspect of stunning musical performance. It has new
levels of transparency, openness, an unfettered sense of big power, seriously
excellent bass power and timbre. Big bass passages are powerful yet defined and
very tuneful/taut. The light, delicate touch when appropriate says ‘tubes’.
You’ll feel confident challenging any amplifier.

  

The Design:
John Hillig, our designer, worked a very long time to achieve enhanced clarity
without brightness or ‘etching’ of the upper octaves. Finally he chipped away
and a new level of excellence emerged. Design simplicity remains a trademark
for Musical Concepts.

  

The PA-6 is
an enhanced, effective tweaked-by-ear amplifier circuit with a single-ended
differential amp front-end called a LTP(long tail pair). The LTP pair are PNP
transistors unlike all our previous boards which used an NPN architecture. A
dual transistor circuit relying on transistor Vbe characteristics for reference
voltage is used for the current source. This type bias source is also used for
the VAS driver stage. It is a completely separate current source which does not
rely on the first stage for its reference voltage.

 

 

 

An enhanced
front-end power supply design, called CRC, inherited from PA-5 series with four
front-end power supply caps provides a much cleaner, quieter voltage for the
critical front-end circuitry.

 

Because
MOSFETs are very easy to drive a traditional higher current driver is not
required so a simpler Class-A transconductance stage can do a great job. We use
high-performance low capacitance video transistors.  Also since MOSFETS don’t experience ‘thermal
runaway’ there is no need for volt-amp limiting circuitry further simplifying
the design and enhancing clarity. Your ears will agree that ‘simple is good’.

 

 PA-6! What’s
important to your listening?

 

Superior RFI
reduction at the input circuit in our RFI noisy world > Smoother, sweeter
more open stagePNP
audio-grade transistors in LTP(input stage) > new levels of fullness, proper
weight to lower end of instruments

NPN VAS
driver transistor with low Cob spec > minimal non-harmful load for first stage.
Big sound, dynamics.

CRC power
supply design > smoother, cleaner, anchored sound stage, ‘unshakable’
quality

Superb
Vishay/Dale 1% metal film resistors > -35dB noise, 5ppm/V voltage
coefficient, sense of a quieter, darker background, smoothness.

Improved
bias implementation > more open sound, big soundstage, potent dynamics
without stress.

New design
has lower open-loop gain hence reduced feedback > sweeter, warmer, more bold
quality. 

 

The PA-6
Sound: This is not a mere Hafler, not to demean this great basic amp design!
No, this is a great amplifier in a Hafler chassis. You get a sense of a clean,
clear response to the most intense transients/crescendos. It has an ‘endless
power’ feel to it. The sense of dynamic range, bass solidity and consequent majesty
is striking. Overall delicacy is remarkable. The high frequency extension has a
lucidity, liquidity and naturalness that makes you think you are listening to a
vacuum tube amp. Then along comes bass detail and overall clarity that makes
you reconsider.

 

 The word
fidelity is a really big word. It is more than a marketing term. You feel a
connection to the instrument in a way that is striking. Why? Because you are
hearing so much more of the true tonal structure and timbral clarity of each
instrument. Voices are so clear, full-bodied and intelligible that emotion is
conveyed in the performances at a new level. You feel the mood, the intensity
of the performer. Many will hear new background vocals singing along with the
lead vocal or the multi-layered vocals of the performer simulating background
vocals. There is a sense of gut solidity, simple majesty and air-moving power
that must be heard. If your speakers play deep you’ll be thrilled. PA-6
modified Hafler amps will easily compare to the finest sounding amplifiers
available today.

 

PA-6 Ultra
Modification

 

Our PA-6
Ultra mod is truly State of the Art and beyond State of the Art as it is
practiced by so-called high-end manufacturers. Although we at Musical Concepts
have modified many expensive well known amplifiers we've never seen build
quality even remotely close to the Ultra. The superb Takman resistor is used in
nearly all slots for all Ultra driver boards. For all amps the Ultra also
includes a new high in-rush current, silver-alloy power switch and a
Rhodium-plated IEC power cord socket with hi-current cord. Just imagine what
this incomparable product might sell for if it had some fancy over-hyped
manufacturers name on the front panel. This is the finest mod we have to offe

PA-6! What’s
important to your listening?

 

Superior RFI
reduction at the input circuit in our RFI noisy world > Smoother, sweeter
more open stage

PNP
audio-grade transistors in LTP(input stage) > new levels of fullness, proper
weight to lower end of instruments

 

NPN VAS
driver transistor with low Cob spec > minimal non-harmful load for first
stage. Big sound, dynamics.

 

CRC power
supply design > smoother, cleaner, anchored sound stage, ‘unshakable’
quality

 

Superb
Vishay/Dale 1% metal film resistors > -35dB noise, 5ppm/V voltage
coefficient, sense of a quieter, darker background, smoothness

 

Improved
bias implementation > more open sound, big soundstage, potent dynamics
without stress

 

New design
has lower open-loop gain hence reduced feedback > sweeter, warmer, more bold
quality

 

The PA-6
Sound: This is not a mere Hafler, not to demean this great basic amp design!
No, this is a great amplifier in a Hafler chassis. You get a sense of a clean,
clear response to the most intense transients/crescendos. It has an ‘endless
power’ feel to it. The sense of dynamic range, bass solidity and consequent
majesty is striking. Overall delicacy is remarkable. The high frequency
extension has a lucidity, liquidity and naturalness that makes you think you
are listening to a vacuum tube amp. Then along comes bass detail and overall
clarity that makes you reconsider.

 

The word
fidelity is a really big word. It is more than a marketing term. You feel a
connection to the instrument in a way that is striking. Why? Because you are
hearing so much more of the true tonal structure and timbral clarity of each
instrument. Voices are so clear, full-bodied and intelligible that emotion is
conveyed in the performances at a new level. You feel the mood, the intensity
of the performer. Many will hear new background vocals singing along with the
lead vocal or the multi-layered vocals of the performer simulating background
vocals. There is a sense of gut solidity, simple majesty and air-moving power
that must be heard. If your speakers play deep you’ll be thrilled. PA-6
modified Hafler amps will easily compare to the finest sounding amplifiers
available today.