Upgrade Nakamichi PA 7All power amp with mono blocks

@yyzsantabarbara thanks for asking. The Benchmark LA4 worked out great. The PS Audio M700 mono amps not so much. The Acoustat 1+1 speakers get down to 0.5 Ohm at high frequency. The M700s had a screeching sound at 85db and above indicating a hard clipping. I sold them and tried a pair of Schiit Tyr mono blocks. They had a hard clip and actually shut down at the same point in the music. Quickly returned them to Schiit.

In the mean time I had sold the Nak, so I had to put my old NAD 2700 in. The NAD has a soft clipping feature so I monitored it with the same music passage. It actually flickered at the same passage and if I listened closely there was a bit of muffling. The soft clip NAD marketed way back when actually worked. I just never noticed because the Acoustats rarely draw 0.5 Ohm (I think it only occurrs with a signal above 17k).

I reached out to Nelson Pass and asked if there were any plans for a dual mono XA25 in the future. He had a pair custom built for himself, but none were planned for release. He said the XA25 would handle the 0.5 Ohm signal without a hitch, but that high volume might be an issue if I drove the speakers very loud. On his recommendation I purchased one and it is amazing.

I then decided to upgrade the PS Audio Direct Stream Mk1 DAC. I noticed better detail from friends systems. I tried several including a Chord Dave with an M-Scaler, a HiFi Rose M130, and I borrowed a Tambaqui. I ended up with a Bricasti M1S2 DAC which is amazing in detail and sound (multiple filter choices depending on music type). A benefit I did not expect was it sent a ’louder’ signal to the LA4 which passes the increase along to the XA25. Hi volume is not longer an issue. I am very happy.

I am just starting to explore other pre-amp options, but I am not certain that I will be able to find a suitable upgrade to the LA4. For now I am definitely enjoying the music.

@thriftyaudio Thanks for the response. I now remember reading your take on the m700 in another thread (late night reading yesterday). I think I am going to take a chance on the m700 since my office Magnepan Mini does not drop as low as your speakers.

With regards to your LA4. It is a keeper. I had the LA4 and the HPA4 (2x) and it is not something I will replace. I have 2 systems, and I bought the Holo Audio Serene preamp instead of a LA4 since I had the HPA4 and wanted to try out something else. It is an excellent preamp too and sounds and measures like the LA4. It is just a bit warmer and a lot of people like that over the LA4. In retrospect I should have gotten the LA4. First world problems.

If you want to go for an even more powerful XA25, I am going to be selling my CODA #16 amp in a week or 2 along with my Audience FrontRow speaker cables I use with it. I need to raise funds for a headphone and new speaker. I think we are both in Southern California if you want to have a listen.

How did the Schiit Tyr mono blocks sound when they did work on your speakers. I am thinking of getting a used pair to hold me off until I raise fund for the CODA #16's replacement or just do not use the speaker connected to the #16 until I get a proper replacement. The new speaker (second speaker I will keep) will work with 8 watts.

@yyzsantabarbara The M700 did a great job of separating the channels.  Very good stage left to right.  The Tyr improved the stage L-R slightly and also had a boost in the high bass (over 80 hz).  I felt the Tyr didn't quite handle the treble as well as the M700, but the hard clipping might be influencing my judgement there.  Both sets of mono blocks were good.  

I am set with the XA25 until a mono block version is released.  I tested a CODA #8 and was not impressed.  I was comparing it to the Schitt Tyr at the time.  The #16 was out of my price range so I did not consider it.

I also took a look at the Coda 07.x but liked the LA4 better.  Mostly due to the quiet sound floor on the LA4.  There was just a slight sound out of the speakers with the 07.x with the volume turned up, but nothing playing.  The LA4 was dead quite.

Have you looked at the following pre-amps relative to the LA4?

• Pass Labs XP 22 or 32
• Luxman C 900 U
• Bricasti M20
• Townshend Allegri Reference Mk2

Thanks

@thriftyaudio I also owned the CODA #8, and it is not as good as the #16, but the #8 was pretty good to my ears, just not reference level. The CODA 07x is too noisy for my LA4 + Serene perspective. Once I heard the hiss I could not unhear it even in louder passages. My brain would focus on that and annoy me to no end, so I sold it. I sold my HPA4 to buy the 07x and that was a mistake. I repurchased the HPA4.

The only preamp I heard on your list was the C900u. It was too warm for my tastes. I heard it with the Luxman m900u which I loved. I was planning on getting a m900u to use with the LA4 or HPA4 but got the more powerful CODA #16 instead. The new Luxman M10x sounds more like my #16.

For me, the LA4 + HPA4 is exactly what I want in a preamp. That is add nothing to the sound. I have my sources and amps for the coloring.

A friend of mine in Ventura, CA is building an open baffle speaker that I recently heard and loved. He ran it with Class D on the bass and an 8-watt headphone amp for the top. It was incredible. I expect to listen to this speaker in the Livingroom a lot and will park my Yamaha NS5000 after I will sell my #16. I need a low-cost amp for the NS5000 and the Schitt Tyr or maybe the new Schitt Wotan came into my mind. The PS Audio M700 thoughts were for my office Magnepan Mini, if I sold my Sanders Magtech amp, to raise even more funds.