It's not very often that I endorse a product this strongly, but I have been very impressed with the build quality and sound of the amplifier that was loaned to me by Gary Dews of BorderPatrol Audio Electronics for both of the audio shows that Volti Audio attended in 2011.  Gary builds amplifiers that I want for my own system at home, and that's the best endorsement I can make for a product.   If you're in the market for a high-quality, great sounding tube amplifier, you should definately check out what Gary has to offer.  Here's a quick rundown of some of the key features of BorderPatrol amplifiers, along with a few pictures.   For the complete story, click on the link above to Gary's website and have a look.

BorderPatrol Audio Electronics makes a range of 300B based triode amplifiers in single-ended, parallel single-ended and push-pull formats with power outputs ranging from 9 to 20W/channel.

I asked Gary to give me some technical tidbits on his amps:

"All the designs use inter-stage transformers to couple the driver tubes to the 300B's and have no negative feedback.   The 300B's are used in fixed bias and the negative bias is applied through the secondary of the interstage transformer.  In low sensitivity format, only two active gains stages (the 6C45pi input driver and 300B's) are used and there are no coupling capacitors in the audio circuit.  The chassis are comprised entirely of non-magnetic materials - aluminum and wood construction as standard - with copper and wood on the more expensive EXD versions.   The EXD versions also have inter-stage and output transformers that have undergone deep cryogenic treatment.   Audiophiles will be familiar with the deep cryogenic treatment of tubes and cables but it's application to audio transformers is unique to BorderPatrol."

The BorderPatrol amps all use large and heavy external power supply units (PSU's).   Gary makes two stereo amplifiers that use single PSU's and several dual-mono designs that use two PSU's, one for each channel.  I put a bug in his ear a few weeks ago about building true monoblocs with one PSU for each, which is the topology I would be most interested in myself.

Mounting the PSU externally from the main chassis not only keeps the weight (each PSU weighs 35lbs) and size of the amplifiers manageable, but keeps the hard working iron and its associated electric fields away from the sensitive audio circuitry inside the main chassis.   Gary also points out that separate power supply units "allow a degree of power supply elaboration and sophistication not found in other tube amplifiers".  It's a very smart design!

At RMAF 2011, I was in Gary's room and overheard him explaining the type of input power supply he uses for his amplifiers.  It went something like this:

"Unique to all my amplifiers is the use of choke input filtering, a feature of critical importance not found in other tube amplifiers.  Each PSU contains no less than three itube rectified choke input filter high voltage supplies to independently feed the 300B's, the small signal tubes and the negative bias supply, together with filament supplies for the 300B and small signal tubes."

"Other manufacturers choose the more common capacitor type of input power supply because of lower price, smaller size, and ease of implementation.  This uniquely designed choke input filtering topology has far superior voltage regulation (stiffness) and noise rejection properties.   And this is why BorderPatrol amplifiers have bass performance and dynamics unlike any other 300B amplifier.  It's much more difficult and expensive to build an amplifier this way, but it's definately worth it."

Gary's choice of materials, his power supply design and circuit topology are all the result of a unique way of thinking about the technical design, coupled with many hours of listening.   It is important to him that music sound good through his amplifiers.  This is something that I can certainly relate to, since it's the same approach I take with speaker design.  After the technical aspects of the design have been worked out, there's just no better way to ensure a superior end result than to make final adjustments as you listen to music on the equipment you've created.  I can attest to the results, which are nothing short of outstanding.