Nakamichi CA-7A Preamp

 I shut off the use of my Western Electric 300 B tubes on my SET amp, for ballgames. ( trying to save tube life… I wish I knew at my age of 70, how many years of life they had, using them 4-6 hours at night only… any idea?)

yeah the making of the NAK is amazing  I got interested when I saw the Sky Hi Fi video on YouTube  

Those tubes might outlive us... I'm 74.

@uncleang  nice!!!!

Great thread! I have a Nakamichi CA-7A that I bought at Paris Audio in Torrance, CA in 1985/1986, along with the matching PA-7 amplifier and ST-7 tuner. Not the PA-7A -- this was earlier. Still have the sales receipts -- paid $1935 for the CA-7A. I just dug these out of my closet and they're playing right now behind me in my office. I don't see a way to upload a photo, so here's a link to a photo at my email provider.

In the early 1990s, I moved to Texas, got a much larger house and built out my dream system with a pair of Apogee Duetta Signatures (full range ribbons) that I first heard at Paris Audio and could now afford. Sigh. They produced the best sound I've heard before and since. The PA-7 did a nice job of driving those until we decided all the AV stuff should be in the family room where surround sound would eventually go (also, my wife wanted her living room to actually be a living room after 7 years). No room for the Duettas which have to be at least four feet from the walls, so I regretfully sold them, and I got a pair of more wife-compatible B&W 801s. The PA-7 drove those speakers for years as well, first with the CA-7A and later, by various surround sound receivers, but just 2-channel sound because I never quite got around to choosing and installing surrounds. I retired earlier this year and finally have some time -- finally have a true surround system with a Denon 8100HA and use a Parasound A21+ to drive the 801s. Yep, I'm old now and my hearing isn't what it used to be, but that combination sounds absolutely terrific even in 2-channel mode and surround music can be stunning. So the PA-7 joined the CA-7A and ST-7 in the closet.

With more available time, I recently reconnected the CA-7A (not used for probably 15 years) and the PA-7 (not used since 2022) in my office, hooked them to a pair of B&W bookshelf speakers and they sound... well, stunning after I let them warm up for a few hours (that made a big difference). In keeping with the 80s theme, right now "The Pretender" by Jackson Browne is playing and... goosebumps.  Literally.  One thing I remember that's still true is that these components take time to warm up, and the sound improves over a period of time. I used to just leave them on all the time for this reason. They run pretty warm (almost hot) to the touch, so not a good long-term thing to have in my home office in the summer. 

Part of me finds it hard to believe that these 37-year old components still work. Out of curiosity, I took the top off the CA-7A and it's incredibly clean inside (Nakamichi CA-7A guts). Except for the dubbing and volume, the bypassable equalizer and balance knobs go into boxes. I mention this because I noticed exactly the same thing described @uncleang described with the balance knob: in the center position, the audio is shifted to one side but rotating it shifts the balance as expected. I found that gently pulling/pushing on the knob a little bit fixes that, but it sounds like it's an endemic problem. The three equalizer knobs may have the same issue, but when enabled with the front panel switch, the effect is subtle anyway.

The way the volume is handled is cool: the remote (which I was happy to see I had taken the batteries out of, so no leakage) mechanically rotates the volume knob with a motor. That still works perfectly, as does switching the inputs. I also have the separate Nakamichi power strip that the CA-7A can control (it connects with a DIN-like cable and turns on the PA-7 and other components when the CA-7A is turned on with the remote), but I dimly recall that there was a problem with that strip, like a relay got stuck. 

Because I'm too lazy to move my BluRay player (only CD player left in the house), I hooked my old iPad up to it and have been enjoying lossless Apple Music with the iPad doing the D2A conversion. Probably not ideal, but as I said, it sounds fantastic. I still need to connect my turntable to it and see if the phono stage still works, though. That'll be even better!

After I finish playing with these components and I finish determining the condition, I'll probably finally part with it and put the whole kit-and-kaboodle on EBay. Still need to take the top off the PA-7 and make sure none of the caps are leaking, but it certainly sounds great right now. And the ST-7 AM/FM tuner display is a little borked -- some segments in the display are brighter than others (although the tuner sitll works), so that'll probably be a free bonus.

Anyway, thanks for the memories. I don't think they make 'em like this anymore.

@invaderzim : It would be a real shame for you to get rid of your NAKs.

Your PA-7 which is now almost 40 years old is pretty much bullet proof.

The main things that wear on it are the bias trim pots, some smaller caps and a few transistors mostly related to the negative feedback circuit. Yes, it has NFB but very little. The main caps are of very high quality and if the bias has been kept around the factory recommended 40 mA they should last pretty much forever.

All of the above have been serviced in my MKII version, cost was around $750 to get it all done.  Given that an equivalent new amp of this quality cost  $5K plus, I saw it as a worthwhile investment.

I too noticed that if one pushes the 'balance' knob in and out on the CA-7A it may restore contact on both channels.  Ironically, mine has been working great for almost a year in the center position.

From a brochure on the CA-7A....

"Discrete Balance Control uses 20 precision metal-film resistors and a 21 position switch to ensure precise repeatable settings.  The switch introduces less noise than a conventional control and, in the normal position, all resistors are out of the circuit".

Hence 'straight wire with gain' at the 12 o'clock position.

As a Nakamichi fan - when I was specifically looking for the right CA-5 preamp instead for other reasons, simplicity, sonically - I had scoured CA-7s out there and spoke with many owner-sellers who enjoyed them a lot.

For a secondary SS system, I ended up going a different direction searching for some of Nelson’s other brand/lines and designs for preamps. Its fun to compare under the hood of these units to see how they were designed and built back then.