BorderPatrol makes a range of tube power amplifiers that use the popular 300B triode in single-ended, parallel single-ended and push-pull configurations with power outputs ranging from 9 to 20W/channel. All the designs 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 300B's are used in fixed bias and the bias is applied through the secondary of the inter-stage transformers. The audio chassis are composed of non-magnetic materials and the high 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 single ended SE300B and push-pull P21 are stereo designs that have a single external PSU whilst 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 (each PSU weighs 35lbs and the S20 EXD audio chassis weighs over 60lbs), 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 no less than 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: Power supply, tube complement, materials, component quality and circuit topology and 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. |
BorderPatrol SE300B and S10 single-ended amplifiers. |
The 1st Border Patrol amplifier, the SE300B continues to redefine the capabilities of 300B single-ended amplifiers. Using a single 300B output triode for each channel, the amplifier surprises critics, not just with its resolution but with its 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 supply unit and the amplifier is a model of sweetness, clarity and vibrancy with fine, extended bass and dynamics. The SE300B features a single ended output stage which is the simplest and purest circuit topology available. An external power supply unit feeds both channels and each power supply unit contains three independent valve rectified high voltage supplies that feed different parts of the amplifier together with additional supplies for the tube heaters. The internal components have been selected after exhaustive empirical testing. Different brands of 300B output valves can be used to subtly tailor the sound of the amplifier. The SE300B is often seen at hi-fi shows driving large horn-loaded loudspeaker systems but the amplifier is equally comfortable driving more real world designs. The recommended efficiency for partnering loudspeakers to extract the maximum performance needs to be greater than 93dB/watt but in smaller rooms loudspeakers with efficiency down to 89dB (8ohms) can be used. One reviewer was staggered to find the SE300B driving a loudspeaker (B&W Nautilus) that had defeated everything but his 400W channel transistor amplifier though this is not something we generally recommend. '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 ' ...the Border Patrol might have dipped out on the syrupy sweetness part of the single-ended deal, but it delivers the “real sense of power” with consummate ease, another area in which most of its compatriots fail to live up to their billing. Instead of lush and overblown, the 300B SE (WE) is wonderfully (and correctly) rich. Instruments have a natural weight and colour, and voices, especially tenors, have tremendous authority and a real sense of substance.Roy Gregory Hi-Fi+ issue 8 'Passion, grace and fire.' Jason Kennedy Hi-Fi Choice Jan 99 Hi-Fi Choice EDITORS CHOICE'Uncommonly capable single-ended design with less colouration and more grunt than any of the alternatives- resolution guaranteed.' Jason Kennedy Hi-Fi Choice Jan 99 EDITORS CHOICE' ....., I went back to my transistors. ....there was a congested quality, as though the system had picked up sinusitis.'Paul Messenger Hi-Fi Choice Jan 98 |
From $8995 |
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| The BorderPatrol S10 takes the SE300B design to another level by the addition of a second PSU and dual mono configuration. Stereo separation, dynamics, stability, headroom and control are all improved compared to the SE300B. Any owner of a high efficiency loudspeaker system should strongly consider this amplifier. |
From $13750 |
'Another atypical aspect of this amp is its response. Valves are famous for having a glorious mid-band and a tendency to emphasise this above all else. The S20 while phenomenally transparent in the mid-band has a remarkably flat response. You don’t miss out of the frequency extremes with it: This is a wide band amplifier!' 'The mid-band is proper SET stuff though, voices are superb and you can hear all the words all of the time. This is a fluid and revealing amp that combines a delicacy that lets you hear micro dynamics clearly with an ability to swing real energy when it’s required.' |
From $13750 |
'Superb amplifier with bags of power and genuine resolution, one of the best music appreciation devices available.' 'In the right company this amp delivers transparency, fluidity of timing and grunt like few others out there...... if it's the musical essence you're after it's a tough act to follow.' 'Here, the authority shape, pacing and tactile presence that the P20 brought to the nether regions of these physically modest speakers (Reference 3A and Living Voice Avatar OBx-R) imbued them with a scale and sheer unflappable stability totally at odds with expectations. Tonal colour and separation were superb, with none of the qualitative sameness that collapses the individual character and texture of instruments (and performers).' 'The P20 is a mightily impressive amplifier and one that explodes the triode myth. Once again, it proves that it's not what you use but how you use it that counts. Good engineering will win out. I've listened long and hard to the push-pull Border Patrol and still haven't got its full measure.' |
