[AR amplifier: headphones, Delrama]

2. On page 2 of the original tech sheets for the AR amp, at the bottom there is mention of a NYC company called Delrama International. Who are they, and how were they involved with Acoustic Research?

To the best of my knowledge, the official AR "Specifications and performance curves for the AR Amplifier" and "Specifications and performance curves for the AR Universal Amplifier" information sheets were identified as L-1609 and LIT 1610 respectively (this being printed on the lower left corner of the sheet showing the curves). There is no mention of Delrama on said documents.

It is possible that the Delrama branded (product announcement) tech sheets are not, per se, the sole 'original' AR literature — in that they may have been prepared specifically for (or by) Delrama, with reference to their own distributive/publicity purposes.

Robert_S

[AR amplifier: headphones, Delrama]

1. Regarding the headphone issue, did AR produce a later release of the amplifier with the headphone jack and switch, as suggested by the attached pic? It sure looks factory original to me.

I have two examples of the AR Amplifier, both are the Universal model.

Of these two, the version with the lower serial number (A0227xx) does not have an output for headphones, whereas the later one (A0254xx) is replete with front panel spkr/phones selection switch and headphones jack.

Another difference between the two amplifiers in question is regarding the AR logo printed on the front panel. The unit with the headphones jack has just "AR", the other one has "AR INC." (I have, however, also seen photographs of regular models with the plain "AR" logo, see here for example.) The pictures below are not mine, but are included for reference:

One further external variation I've noticed is that some units have a more elaborate perforated enclosure for the rear heat sinks, as shown below:

Robert_S

[AR 18 B restoration]

Bonjour Philippe,

If you decide to replace the tweeters, or wish to acquire spares, the following link might be of interest:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...em=280208539544

Regarding the AR 1.25" liquid-cooled cone tweeter, my guess is that the 200038-0 and the 200034-0 are the same (except for the '34s addition of the plastic front-plate, and mesh); both would be correct for the AR-18B. The earlier 200014-3 may have lower power handling capabilities; it lacks the S-shaped leadouts, described by AR as giving "added protection during peak power surges".

For (polypropylene) capacitors matching the original 5 uF value, here are two possible sources:

http://www.cricklewoodelectronics.com/Cric...ome.php?cat=155

http://www.iplacoustics.co.uk/ipl_crossover_components.htm

Hope that helps.

Robert_S

[AR 18 B restoration]

The 18s was pretty much the same, save for some slight cosmetic differences, and is also highly recommended.

The 18B had a bull-nosed vinyl cabinet , the same 1 1/4" cone tweeter, 2000Hz crossover, but the tweeter was now centered on the baffle above the woofer, instead of being offset as in the earlier 18's.

A minor AR-18/18s information supplement/correction!

The tweeter placement change, from offset to centred, was seen in the transition from the AR-18 to the AR-18s.

Also, the capacitor value changed: 6 uF for the 18, 5 uF for the 18s. The 18s used the 200038-0 tweeter (featuring S-shaped leadouts for "added protection during peak power surges"), the 18 had the 200014-3 (also seen in the AR-7x).

Incidentally, having both UK and USA assembled models of the AR-18s, I was surprised to see a difference in the cabinet width: USA made are 255 mm wide, UK are 244 mm.

The AR-18s remains a 'cult classic', here in the UK, and is still much sought-after for use as a near-field studio monitor, by those 'in the know'.

Robert_S