BorderPatrol makes a range of tube power amplifiers that use the ever-popular 300B triode in single-ended, parallel single-ended and push-pull configurations with power outputs ranging from 9 to 20W/channel. All models use inter-stage transformers to couple the driver tube to the 300B’s and have no negative feedback to maximise resolution and preserve signal integrity. The audio chassis are composed of non-magnetic materials and the higher priced EXD versions use copper chassis parts and inter-stage and output transformers that have undergone deep cryogenic treatment.

Central to the BorderPatrol designs and philosophy are the large and heavy external power supply units (PSU’s). The parallel single-ended S20, push-pull P20 and single-ended S10 are dual mono designs that feature two PSU’s, one for each channel. Mounting the PSU’s externally not only keeps the weight and size of the amplifiers manageable, it keeps the hard working iron and its electric fields away from the sensitive audio circuitry. It also allows a degree of power supply elaboration and sophistication not found in other tube amplifiers.

Each PSU contains three independent tube rectified, choke input filter high voltage supplies to independently feed the 300B’s, the input/driver tubes and the negative bias supply, together with filament supplies for the 300B’s and small signal tubes. The use of choke input filtering is a critical difference and is unique to BorderPatrol power amplifiers. Other brands use tube rectification and choke smoothing but do so in the cheaper, smaller and easier to implement capacitor input filter configuration. A choke input filter design has far superior voltage regulation (stiffness) and noise rejection. The PSU’s stiffness explains why the BorderPatrol amplifiers have bass performance and dynamics unlike any other 300B amplifiers.

In a BorderPatrol amplifier, all aspects of the design have been taken into consideration: audio circuit, power supply, tube complement, materials and component quality. The solutions have been chosen after many hours of listening. The result is the most complete sounding range of tube amplifiers available today and a rare combination of dynamics, integration, resolution and musicality.

‘The SE300B is packed up for shipment back to BorderPatrol, and I’ll miss it a lot. I was impressed with its great bass coupled with soundstage definition that is so hard to achieve.

Mark Blackmore, The Audio Beast

Superb amplifier with bags of power and genuine resolution, one of the best music appreciation devices available.

Jason Kennedy, Hi-Fi Choice - EDITORS CHOICE

‘There are no rose tinted specs, slurred and rolled off frequency extremes or over stuffed harmonics here.  In fact, for the first time in my experience, I’m listening to an amplifier with the linearity and directness that are supposed to be single-ended’s great virtues.

Roy Gregory, Hi-Fi+ issue 8

What I heard was a thoroughly modern-sounding amp that just happens to use antiquated tubes and just happens to produce a mere 8 watts. You should hear this amp, especially if you think you know how a 300B-based amp sounds.

Mark Blackmore, The Audio Beast
Patrol S20 parallel single-ended amplifier


The BorderPatrol S20EXD gives 18 Class A watts per channel from a pair of 300B output valves in parallel single-ended configuration, and can drive a wide variety of loudspeakers.

The combination of extended bandwidth married to excellent dynamics and a magic mid-range make the S20 both capable and musically communicative whilst the twin external power supply units give mono-block like sound staging and complete channel independence.

Clear, clean, fluid, extended, tonally rich and natural are all adjectives used to describe the performance of this fine amplifier.

Marrying finesse and sophistication to dynamics not usually found in SET amplifiers, the BorderPatrol S20EXD is a fine musical transportation device.

Recommended loudspeaker efficiency >90dB/watt for best performance.

The BorderPatrol S20 EXD features inter-stage transformer coupling, twin external power supply units (PSU’s), hard wiring, a chassis made from copper and wood, and cryo treatments to the amp and PSU’s. Each PSU contains three independent tube rectified, choke input filter supplies, for 300B H.T. driver tube H.T. and 300B bias. It is also available with the EXS power supply units.


The BorderPatrol S10 and SE300B continue to redefine the capabilities of 300B single-ended amplifiers. Using a single 300B output triode for each channel, the amplifiers surprise critics not just with their resolution but with dynamics and control which are thought to be beyond single-ended designs. The poor bass and weak dynamics that are associated with designs of this type are removed by the sophisticated external power supplies and the amplifiers are models of sweetness, clarity and vibrancy together with extended bass and dynamics.

The S10 and SE300B feature a single-ended output stage which is the simplest and purest circuit topology available. The SE300B is a stereo amplifier with an external power supply unit that uses tube rectification and choke input filtering whereas the S10 is  dual mono design with an external power supply unit for each channel.

The S10 and SE300B can be ordered with EXD specification where copper chassis parts, cryo-treated transformers and upgraded components serve to further increase the resolution and improve the tonality of the amplifiers. The S10 is also available with the EXS power supply units.

BorderPatrol S10 and SE300B single-ended amplifier
Border Patrol P20 push-pull amplifier


The Border Patrol P20EXD has carved a solid reputation for fine sound quality, serious musical enjoyment and ability to drive loudspeakers that were thought to be beyond the capability of 20W valve amplifiers. Featuring two 300B output triodes per channel in push-pull configuration giving 20W/channel, the P20EXD handles all music with finesse and aplomb and injects a serious dose of energy and excitement. The natural timbres of instruments are superbly portrayed with fine resolution and detail retrieval whilst floor-shaking bass can be delivered should the music demand it. The dual external power supply units are once again in evidence providing a super quiet, black background and a solid bass foundation. Single-ended all the way up to the inter-stage transformer the P20EXD takes advantage of this supposedly antiquated technology to split the phase in a more accurate and time consistent way than the much more common active phase splitters resulting in a purer sound with better resolution and leading edge definition. Described by one hi-fi reviewer as ‘one of the finest musical enjoyment devices available’ the Border Patrol is sure to illuminate and extract maximum enjoyment from any music collection.

Also available is the BorderPatrol P21EXD. The is the stereo version of the P20EXD and uses a single PSU to power both channels.

Recommended loudspeaker efficiency >87dB/watt

Both P20 and P21 amplifiers can be ordered with EXD specification where copper chassis parts, cryo-treated transformers and upgraded components serve to further increase the resolution and improve the tonality of the amplifiers.

The P20 is also available with the EXS power supply units.