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Sugden Super Mod


We can modify your vintage amplifier to suit your requirements

You might wish for different connectors (e.g. RCA in place of DIN sockets) or improve the electrical safety.
Maybe you love the look of your amplifier but want to take the sound to greater heights.
Whatever your requirement, contact us on 044 01905 821737 and we will advise.
The Sugden A21 mod discussed below is unfortunately, no longer available but is an excellent example of what can be done.

Premium amplifier modifications

By popular request we can carry out major modifications to your amplifier. In this Sugden A21class A example it raises this lovely vintage amplifier
to much greater heights with an improved sonic performance. Putting it on par with today's greats.  Many Sugden fans love
the wooden case and black and silver front panel but want that extra ounce of musical clarity and separation. After this mod, they
have it all!

See the features below:

New ripple free PSU Assembly,

 New Power Output and Rear Heatsink Assembly,

Inside view of a modified A21

Inside view of original A21

Rear view of the modified A21

Front view  of the modified A21


bulletRob our electronic design engineer has totally redesigned the PSU and output stage with a vastly improved performance.

Power Amplifier PCB

bulletFrequency response 10Hz to 100kHz.
bulletDistortion @ 1kHz and 10kHz. less than 0.005% THD at 15W rms
bulletMax Class A RMS output power per channel 20 W rms into 8 ohms
bulletUses specially chosen  high quality ROHS semiconductors and components (output devices 2SC5200 and 2SA1943)
bulletThe 'direct/normal' switch when set to 'direct', removes the tone control stage to allow you to use an alternative pre-amp.
(In the direct mode the volume control functions as normal, the balance and tone controls are bypassed.)
bulletTwo operating modes 'cool and 'hot' allow you to switch from class AB to  Class A* 
bulletThe class A section includes Improved DC feedback current stabilization  


bulletNew rear aluminium panel with extra large heat sinks and extra room for improved socket spacing

bulletNormal/Direct switch to switch the Sugden tone control stage in or out
bulletClass A/B selector switch. This allows reduced heat dissipation (particularly useful in the summer months)
bulletHigh quality gold plated conformal** loudspeaker binding posts
bulletGold Plated RCA sockets for Radio, Aux and Phono inputs
bulletIEC Mains input with fused and DPST on-off switch
bulletTwo massive 0.7 oC/W heat sinks, one for each channel
bulletTwo single layer output stage PCBs nest between the heat sink shields
bulletUK hand built throughout including  the PCBs, metal work and wiring.
bulletOption for a totally new high performance phono stage and tone control unit


bulletTwin power supply (separate rectification,  smoothing and ripple reduction circuits for each output stage
bulletIn the case of the early serial number Sugden A21s a new Toroidal transformer is used  for reduced magnetic field and extra power handling

* The word 'mainly' is used to signify the grey areas in the A/B classification. A class B amplifier needs a small amount of bias to remove cross over distortion, so at very low signal
 levels the amplifier works in class A.  Class A amplifiers work in class A for signal currents up to the set class A current typically up to an amp or so, and then reverts to class B on larger current peaks.

** According to the  ROHS and LV directives the original 4mm loudspeaker sockets and 4mm banana plugs must not be used for loudspeaker connections on new equipment, due
 to exposed metal contacts and risk of electric shock.         

This is a major unique hand built modification through and through. Prices start at 600.00.   Phone 044(0)1905 821737 for specific pricing and lead times.



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Last modified: Monday, 27. April 2015 12:57