What are your go to LP's for evaluating new gear or new tubes?

To @billpete, good for you. I like AR9s quite a bit and their history.  As you may be well aware, known as the "inspiration of future audio products" in its era. While I’ve never owned a set myself, a local dealer had a set a few months back to admire. I suspect with the right amplifier(s) handling them and those two parallel-wired 4-ohm woofers, i.e. the "electronic automatic transmission" as I recall, can sound really cool.

Not to sidetrack too much, yet Audioholics did an updated editorial review in 2023 on your AR9s. Just have to love all the speakers made back when. I enjoyed seeing them back then, not too often though. Not sure if you saw this before but thought i’d mention it - https://www.audioholics.com/editorials/acoustic-research-ar9

I have read that article. Always makes me smile. They were a reference of their day. They are still pretty damn good in my book. They don't do everything perfectly but they were designed around classical music and they do a wonderful job with classical music, orchestra, organ, piano, any acoustic strings, horns and percussion. They were very well thought out for the purpose of listening to classical music. Any acoustic stuff is really good. Not as great for loud rock concert listening but I'm OK with that too. Not terrible at rock, just not what they were made for.

Lots more AR3's out there than 9's but there is a fair following for the 9's with many still in use today. The 9's like power and I biamp with two 250 X 2 @8ohm SS A/B amps. The difference between single amp to biamp is night and day. I've been listening to them for over 20 years and I do not get tired of them. Getting the Linn and a different cartridge into the system yesterday brought some new life back to the old classics. Most enjoyable. More improvements to make but having fun for now. Next up will be the SLP98, another classic to add to my system. Looking forward to it.

I'll have to watch for Opus 3's. I'm not sure I have any but I might. I have a fairly extensive collection and I often find things that I don't recall even buying. Getting old has it's advantages as well as disadvantages. :)

I know what you mean! I happen to be listening to one of their finest this morning, Cyndee Peter's Black Is The Color (1977, Opus 3 77-06). (Which is quite a change from the one I played before it—Quadrophenia!) I would not normally think of myself as a candidate for gospel singing, but It's impossible not to love this woman's voice!

dogberry

I can completely identify with that. I certainly have Quadrophenia, have not heard it in a long time but that doesn't mean I won't ever hear it again. I also have some Amy Grant somewhere, another beautiful voice. Last night I was going through some of my collection that I don't normally look through and found 3 albums by Joni Mitchell that I didn't remember having. Court and Spark was one that someone had mentioned so I put it on and was very pleasantly surprised. Very well recorded and her voice was better than I remembered. My son had never heard it before and he enjoyed it. I probably hadn't heard it in close to 50 years and it was far better than I remembered. Even my wife commented on how good her voice was. Joni did the cover art herself. I believe that Cat Stevens used to do some of his as well. Art work was a good part of having albums and I collect some for the art as much as the music. Fun stuff.

The overture of The Who's Tommy. Japanese pressing. Mostly for Townsend's acoustic guitar work and Moon's drums.  

Who's Next, Japanese pressing: Behind Blue Eyes. For the vocals and Townsend's Electric guitar.

Court and Spark 1980 Nautilus half speed remaster. Mainly, because I am so familiar with the album.

Anything from the Louis Armstrong/Duke Ellington sessions: 1999 Classic Records remaster. For the detail, Armstrong's voice, and the heavenly sound of the clarinet.

Karajan conducting the Berliner Philharmonica: Beethoven's 9th, 4th movement. 1963 pressing. Mainly for the extreme dynamics. And the cello/double basses near the beginning of the movement.

Cat Steven's "Where do the Children Play" from Tea for the Tillerman. Mainly because it is such a beautifully recorded song with great dynamics and very large lows.

The Pretender's unplugged "Isle of View". Broadcast live on BBC television in 1995. An incredible performance. Chrissie Hynde is at the top of her game. And the recording is superb. The inclusion of The Duke String Quartet iin the arrangements works very well. Although getting your hands on a vinyl pressing can be challenging. Since it was only released on vinyl in the UK. My vinyl copy did not come cheap. But CDs are readily available.

And anything that has well recorded cellos. Elenor Rigby comes to mind.