Nakamichi CA-7A Preamp

@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.

@decooney :

The NAK - CA series preamps were not designed by NP, but as I stated earlier the circuitry in these pres are very NP like in form and function.

The PA & CA Naks were built when Nakamichi was at its zenith, so much so that they didn't mind paying to use some one else's stasis technology as opposed to the 'not invented here' approach of many corporations. 

My tech tells me that the parts and assembly were superior to just about anything else on the market at the time regardless of cost. 

BTW: he works on Thresholds also, and he states that they're no match quality wise to the NAKs.

@uncleang yeah I never said that, but do test other units he did design.  My local tech did work at Threshold, lives down the road, and cautioned about the boards in those older units, so I don't run an of that in my primary system for that reason.

For my secondary system I do have some upgraded Pass/Forte' gear, and it's fairly simple inside, and no need to keep a bunch of spare boards and bits around. My main system is all tube, point to point wiring, so thankfully I don't have to worry about aging, brittle or warped boards, or anything like that.