Nakamichi CA-7A Preamp

I have a NAK PA-7A MKII amp and a CA-7A pre. They are a phenomenal combo. The phono section in the pre is in a league of it’s own. I use an AT33PTG/II cart and it’s hard to describe how utterly clean the sound is.

The one weakness the pre has is the balance control may lose contact with the left or right channel when set in the mid position. Even after proper cleaning it only lasts about 6-9 months before the problem reappears.

Both units were manufactured in 1990; I purchased them used in 1998 for $2500.

BTW: The CA-7A is not a Nelson Pass design (the amp is) but it is based on Pass technology.  From the sales brochure for the CA-7A .... We developed a direct coupled output stage using a complimentary-symmetry emitter follower with a current bootstrap.  Same principles as in Stasis amplification.

Best money I ever spent.

@moose89 

The CA-7A has two torrodial transformers, so one would think that they're for left and right channels respectively.  They're not. One transformer is for line inputs and the other for phono; each transformer has separate windings for left/right channel.

There's trim pots to adjust MM, MC and line inputs which should be done periodically or after shipping.

Yes, the buttons are very fragile (use remote whenever possible); I've broken two but glued them back on so they're all there.

This pre will easily reveal the weakest links in your system, but when you've addressed them all the rewards are sublime.

 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.

@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.

@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.