Control Unit pre-amplifier upgrades.


Work required Sonic Models
6DE7/6DR7/6EM7 conversion This conversion involves changing the 5687 audio circuit to a new circuit using the 6DE7/6DR7/6EM7 family of triodes. A new circuit board and filament transformer is required. These tubes sound great! Big, lustrous, clean, rich and full. All 5687 Control Units
EXT1 conversionAddition of an external PSU. The PSU uses the low distortion power transformer configuration used in the Control Unit EXD but with much larger transformers. A much larger choke (the same size as in the power amp PSU's) is also used.BorderPatrol users will be familiar with the affects of oversized power supply units. It improves all aspects of dynamic performance but not in a crash-bang-wallop way, unless the music asks for it.
Composure, headroom, bass, solidity, resolution and tonality are all improved. It easily digs captivating tunes out of almost any recording.
All Control Units
EXT 2 conversionAddition of dual external PSU's and re-configuration to dual mono. This takes the Control Unit to the ultimate. It builds upon the EXT1 modification and gives the superior stereo and composure that only dual mono design can bring. All Control Units
EXDA 2nd power transformer is added to the PSU to create the low distortion PSU topology.
Custom made polypropylene PSU capacitors are fitted together with a superior selector switch and volume control.
Numerous other details and refinements are installed which brings the Control Units up to latest spec.
Removes background noise and grain which improves resolution and lowers the noise floor.
It widens and deepens the sound stage and makes the pre-amp sound much more fluid and free. The overall result is a pre-amp that sounds much more natural.

All Control Units

Pack 1
Brings old Control Units up to the latest specification. Involves fitting different resistors and capacitors, superior volume pot, superior selector switch and numerous small tweaks and refinements.The very first Control Unit's could sound etched and less than relaxed in some systems. Whilst this made for a revealing listen it could be fatiguing. The latest specification is considerably more relaxed and refined whilst being equally dynamic and revealing.

All Control Units prior to 2006

Amplifier upgrades.
UpgradeWork requiredSonicModels
EXD PACKComplete strip down and re-build of the amplifier into copper chassis parts.
Changing the inter-stage and output transformers to cryogenically treated ones.
Re-building audio the circuit with our preferred carbon film resistors.
Any tweaks and detail changes required to bring up to the latest spec.

The amps become clearer and easier listen to with much finer dexterity and flow coupled to a much more relaxed and natural tonality. The noise floor is much lower improving resolution and clarity

The copper chassis parts impart a richer, more lustrous tonality with a cleaner background and less hash and grain. The carbon film resistors are more natural and uniform sounding than the metal film/wire-wounds used previously making for a more relaxed, less edgy sound and the cryogenically treated transformers have superior resolution and micro-dynamic capability coupled to a lower noise floor. The overall effect is a much more natural and relaxed sound with much better clarity, resolution and fluidity.

SE300B, S10, P20, P21, S20

High sensitivity configuration to low sensitivity configuration.Changing the CV4068/E182CC input/driver circuit to the current specification low sensitivity 6C45pi configuration. * -see below.The 6C45pi input stage has  sounds cleaner and 'simpler' than the CV4068/E182CC and the lower input sensitivity allows active pre-amplifiers to be used without noise and gain issues which results in a much more alive and dynamic sound.

SE300B, S10, P20, P21, S20

Convert to Dual Mono:

P21 to P20

SE300B to S10

The addition of a 2nd PSU and 2nd set of power supply capacitors and re-configuring the circuit to dual mono.Adding the 2nd PSU greatly improves the dynamic capabilities of the amplifier in the same way as moving from a stereo amp to mono-blocks. Stereo separation, image placement, dynamic headroom are all improved. SE300B, P21
Power Supply upgrades


 Work required



Conversion to MB specification

Change power transformer and choke of the BorderPatrol PSU to the high performance MB specification units.

Lowers the noise floor and improves micro-dynamic resolution.
Improves the dynamics. Bass is even better defined with additional control. Greater sense of solidity and headroom. Takes the improvement brought by the standard supply to another level.

All PSU's