Audio Research D-115 MKIII tube amp..

I owned one for a couple of years. Very balanced and smooth tone but not overly warmish (by early 90's standard). Tonally it was much like the SP10 pre-amp that came out at the same time. Soundwise it was a very good amp.Its got a lot of tubes in it and frankly its hard to maintain. Biasing the tubes is difficult and time consuming. Additionally there are no fuses to protect the bias resistors if a tube shorts out - unless you are a good tech yourself you'll have to haul it into the shop for repairs.

Mk III? This status must be due to some rebuilding by ARC since this amp's discontinued production in the mid 80s. To my knowledge, the D70, D115 and D250 only got a Mk II status with the D250 then getting a "Servo" update. The D250 had many reported reliability issues but I do not think this plagued the 70 or 115 models.

As for these three amps, it was the end of all tube designs that only returned with the VT150 mono blocks 10 years later; these were phenomenol! The D series were excellent but lacked the refinements at the frequency extremes compared to designs of today. But I much prefered these models to the Classic series that followed them in the late 80s and early 90s. The Classic series were just too analytical sounding and lacked the magic of the all tubed D amps and the SP-10.

One problem with ARC amps, even the later models like the VT amps was that resistors will often be destroyed when tubes fail. I went through this hassle a few times with the VT130 amp.

For $1000 or so on the used market, I think you will not find much better sound than this but perhaps the headaches and maintenance of this old design might not be worth it in the long run. If you want an ARC amp, I see the VT130 up for sale from time to time in the $1500-1700 price range and this is an outstanding value....always was a sleeper in the ARC line. But it only has balanced inputs so this may be a limiting factor to you.

John

Jsujo.
Go to www.arcdb.ws for info on any ARC component current or old production.Jafox is right there is only MK 2 revision on that amp.
George.

I had an ARC D115 mk II for four years in the late 1980s and early 90s. It was used to power a pair of Martin Logan CLSes and was preceded by a Beard P101, and then a Spectral DMC10-Delta.
This amp had a very clear and clean midband with that liquid ARC way with soundstaging that is so compelling. It was not particularly defined or extended in the bass, but not unpleasant. It's upper range performance was pleasant, but not particularly extended or powerful. The upper harmonics that allow you to determine what certain instruments are in an orchestra were MIA. Of course, the CLSes are particularly difficult to drive, so I am certain your results would differ from mine. I had no service issues with my unit during the time that I owned it.

Yioryos is right there was no mkIII.

I am currently using the same D-115 mkII that I purchased new in 89 or 90. I have had a few tube failures, but have just soldered in new resistors I got from Leonard at ARC. It is not that big a deal.

I don't really care for burning my fingers when biasing the tubes, but it is also not that big a deal. However, you will need a good (~$150) multi-meter to do so.

I am driving ML CLS's from an AI 3A. Still love the sound of this amp.

I owned one and really liked it a lot, great staging, a lot of umph in the bass but as noted by Silab, not as controlled as what you can currently find albeit at a price. The upper frequencies in comparison to the better tube amps out there currently is also not extended and I always noted a glare I couldn't completely eliminate. It uses a lot of power, about 400 watts at idle, is a royal pain to bias, you need a long probe to get between the cluster of 4 outputs per channel and the bias is quite high at 65ma. As far as I'm concerned for 1K you aren't going to find a new tube or ss amp that will touch this level of performance at this power rating cause the bottom line is it makes music and can power quite a few speakers out there.

It cost 3k new and production stopped in 1989, right before introduction of the "Classic 60". I like the D-115 Mk 2 better myself, the Classic had a bite that the all tube D-115 didn't. Maintenance could be an issue but it is a good design and of course you always have the support of ARC. I sold it about 4 years ago to a friend that still has it along with an SP-10 Mk 2. I always enjoy listening to his system.

I like only to add that this amp is really a lot sensitive to tube rolling.The first great improvement is to get 3 real nice nos 6 dj8s in V1, V2,V3 pos.(I have Amperex globe logo early '60) ,these tubes in this position can share a lot or their sonic,well known virtues.The amp gets completely to another league, no hint of glare at all! In my ex. kt88 EH can controll the bass well enough that mids and highs from Amperex are really shining, staging is great, music flows.
I tried VT 130 SE, then VT100 mk2,both with stock tubes,simply no contest.
Sorry for my poor english.