Price Paid:  $999.00 from Tonbridge Audio Cons

Summary:
Beautiful, glare free, detailed treble, detailed mid range and tight, accurate, tuneful bass. The performance of this amp does diminish with age and it should be serviced at least every 5 years - although that mostly entails revalving, which you can do yourself. I haven't heard a better sounding amp in this price range. The Sugden A28 comes close. Input switches and volume/balance pots are not of the highest quality and when the time comes for an extensive service it is a good idea to replace them. I don't know much about valves, but I'm told by Boarder Patrol that the standard ones can be improved on considerably. The amp has been in daily use since 1988 and has broken down once. Fixed and serviced promptly by the makers - now sadly defunct. In the process of upgrading other components over the years, I have listened to may amps, some much more expensive and have never wanted to part with my 500. It may not have any big strengths but it does everything well and has a knack of just disappering, leaving only the music. In its 15th year (with two services in the interim), the addition of a higher quality front end (Naim CD5 with Hi Cap) has exposed slight raggedness in the top end, some lack of bass control and a sligh L/R imbalance. As I write this, it's at Boarder Patrol being refurbished to 1996 spec, having the volume pot changed, and they'de talked me into an external power supply. In a week's time I will likely be set for another 15 years. Although rated at 25W, this amp has balls. And it looks beautiful. Highly recommended if in good working order. Don't be put off by the way some valve amps sound. This one is a belter.

Strengths:
Transparent, musical and very untiring to listen to. Very critical of source components but will sound louder than 25W (without the glare) with well matched speakers.

Weaknesses:
Needs TLC, but will always reward your efforts to keep it in tip top condition.

Similar Products Used:
None.

Price Paid:  $400.00 from Off a friend.

Summary:
this is my first valve amp and i think i hit it lucky,i have a pair of kef 105s purchased of another friend for £200 and used a pair of quad transistor mono blocks sounded good but then purchased the ai 500 could not belive the differance in sound,extended bass and a stereo image and transparence like i had never heard,betterd when a invested in some qed silver speaker cable.love it!!! intrested in any mods?

Strengths:
sounds great.

Weaknesses:
noisy pots and phone plug are loose.

Similar Products Used:
none

Price Paid:  $1000.00 from de jong systems

Summary:
every one likes a different sound

Strengths:
i am very happy with the sound that it produces.they have put in other condensators(blackgates)this is a very good improvement to the 500 model.and it looks great

Weaknesses:
the buzz from the transformators but a couple of rings will do the trick.

Similar Products Used:
a couple of transistor amps.

Price Paid:  $0.00

Summary:
Just a followup to my review below. I have since added a Borderpatrol power, changed the coupling caps to auricaps, and the cathode electrolytics to Blackgates. The sound is truly remarkable. I've compared it to amps in the $3-$5000 range with outstanding results. Before the changes this amps weaknesses were its mushy bass and its inability to remain articulate during complex passages. No longer. Now the bass is tight and textured, imaging is holographic, and the amp is infinitely more musical. My recommendation for somebody who doesn't have the cash to pay for the Borderpatrol(amazing!) is to change the cathode electrolytics to Blackgates. It's cheap, and in my case it provided the next biggest improvement.

Similar Products Used:
Rogue Audio Tempest, Rogue Audio M120's, Manley Stingray, Audiomat Solfege, Conrad Johnson (yuck! can't remember the model), Krell & Levinson (too hi-fi and artificial sounding)

Price Paid:  $400.00 from net

Summary:
In stock form this amp does suffer from soggy bass and mediocre dynamics as the reviewer mentioned below. However with a few modifications the difference in performance is like night and day. Tweaks I suggest are: ---> change all linestage and phonostage tubes to quality NOS - I use Telefunken and Siemens ---> change output tubes to Svetlana or JJ Tesla el34 - I use Svetlana ---> use an aftermarket power cord - I use the asylum cord at diycable.com ---> replace the cheap pots and switches - I use a DACT CT2 attenuator and I will soon be replacing the balance pot and switches as well ---> use some kind of isolation device - I built a diy seismic sink and it looks almost exactly like the Brighstar product. The sound I have achieved with these modifications is very gratifying. A midrange like butter with crisp and extended highs. A broad and transparent soundstage with excellent imaging. The bass does''nt have the slam of of solid state but for jazz and acoustic this amp really sings. Also, in a couple of weeks I''ll be fitting a Border Patrol power supply which is supposed to ameliorate the bass issues while simultaneously improving dynamics and tonality. Can''t wait - It appears I''ll be the first in the US to take the Border Patrol leap. Yikes! An attractive and musically coherent second hand purchase. Definitely five stars.

Strengths:
with a few modifications this amp strikes a perfect balance of detail retrieval and musicality.

Weaknesses:
cheap pots and switches, difficult to work on