Bryston 7B versus Nakamichi PA7 amp

autoconsortium

I currently have two Lexicon 501 (they are actually Bryston 7B's made for Lexicon with their logo on them) amps. They are 800watt mono-blocks. I paid quite a bit for them, almost $3,000 used. If I could sell these on the bay, and pick up a couple of Nakamichi PA7's instead (about 6-800 a piece), would I get the sound quality I have become accustomed to with the Bryston? They sound excellent, but I've heard the PA7's are great as well. The PA7's are not monoblock circuitry...is the monoblock design better sound quality?

heiney9

The PA-7's IMO, are a very musical amplifier. STASIS developed by Nelson Pass is really the feature that sets this amp apart. It's essentially a class A design so it gets very hot just idiling. These typically can benefit from service if they have never been in. The bias tends to drift as they get older (may or maynot be a problem) the bias pots usually need to be replaced, they tend to be difficult to set.

One other small area of concern if you are driving very difficult speakers is the 1st generation PA5 and PA7 would trip the protection circuit prematurely. They came from the factory set a bit on the cautious side (not sure why). There was a simple factory fix and many were fixed. Look over at DIYAUDIO.COM to see the fix. Many of the guys there (old service techs) love these amps.

Output tranny's and parts for the bridge rectifiers are hard to find but not impossible. Overall even if abused they are built like tanks. Many of the concerns mentioned above are not typical but something to be aware of. Like any nice vintage piece they are on the higher end to repair. But should be virtually trouble free.

I've almost pulled the trigger on either the PA5 or PA7 several times, just didn't. A nice PA7 with all documentation, box and original owner will run you in the neighborhood of $800-1000 and the rarer PA7 II $1000-1200.

They are a very smooth sounding amp with wonderful midrange. Bass is full but probably not the last authority in slam. Top end is very good and grain free.

H9

unc2701

Yeah, the Nak sounds and acts kinda like a class A and it's going to take some maintenance to keep it in top form. You will probably never need to do any repairs with the Brystons. Ever.

So, see if you can find the Nak to audition and see if you like it. Personally, if I were going that route, I'd get some true Class A amps like the Nelson Pass Alephs, which have a very simple layout, rather than the Nak.

heiney9

unc2701 wrote:

Yeah, the Nak sounds and acts kinda like a class A and it's going to take some maintenance to keep it in top form. You will probably never need to do any repairs with the Brystons. Ever.

So, see if you can find the Nak to audition and see if you like it. Personally, if I were going that route, I'd get some true Class A amps like the Nelson Pass Alephs, which have a very simple layout, rather than the Nak.

Well, it really is class A. It's just that STASIS uses a cascode configuration. Essentially it's 2 amplifiers driving each channel. I really can't be called True class A in the strict sense, it's a very slick deriviative that behaves just like a true class A config. Really it's not any more prone to maintenance than anything else. These were manufactured 1985-1987 so as with anything that age it may or may not work absolutely perfectly.

I have no doubts the PA7 would compete with the Bryston and may even be a smoother amp. Many Pass-ophiles knock the Nak series and perhaps compared to a true N. Pass design like the Aleph would better it. But I'm not 100% convinced. Certainly if you can get the real thing for about the same cost in the same cond (Aleph) go for it. But they tend be much higher priced.

YMMV

H9

unc2701

Oh, you'd come nowhere close in price for the power the Nak has. It'd take the Aleph mono's at about $2500 or so to match the Nak's 200 watts. Still, I thought that stasis design had a neg feedback loop??? Maybe I'm thinking of something else.

As for the maintenance, nothing is going to beat a bryston... which is what he's used to and like you said the Nak is starting to get up there in age. The Anthem dealer here had one in his shop (as well as some badass Mcintosh gear, go figure) and he'd had to tweak around with the bias on it, too. Just something to be aware of.

heiney9

unc2701 wrote:

Oh, you'd come nowhere close in price for the power the Nak has. It'd take the Aleph mono's at about $2500 or so to match the Nak's 200 watts. Still, I thought that stasis design had a neg feedback loop??? Maybe I'm thinking of something else.

As for the maintenance, nothing is going to beat a bryston... which is what he's used to and like you said the Nak is starting to get up there in age. The Anthem dealer here had one in his shop (as well as some badass Mcintosh gear, go figure) and he'd had to tweak around with the bias on it, too. Just something to be aware of.

That's one of the benefits of STASIS is no global feedback. In corresponding with N. Pass he stated Nak did virtually nothing to change the circuit. Like I mentioned the bias pots can be trouble some, but once replaced with modern attenuated pots (fairly inexpensive) there should be no other troubles. Perhaps at it's (PA7) current age it may need some tweeking after 20 years or so. Bryston is certainly top notch in build quality. I just feel they would compare favorably. But as always, it's up to the individual to decide which works best in their own system. Good discussion

H9

unc2701

Agreed, you gotta listen to the gear and figure out what you like

I wasn't able to put it back to back against an Aleph, so it's hard to give the final word, but the sound was very similiar. In comparison, the brystons have a somewhat different signature, or lack thereof. Kinda like drinking distilled water.

Did Nak pay Pass for the design or was it a rip off?

heiney9

Here's a basic description of STASIS.

An amplifier circuit having two identical inverting folded-cascode amplifier stages coupled together through a coupling resistor at the positive terminals of the respective stages. Each stage includes an input gain transistor whose gate forms the negative input terminal of the amplifier stage coupled to receive an input signal through an input resistor, whose source forms the positive input terminal of the amplifier stage, and whose drain is connected to the source of a level-shifting cascode transistor. Both transistors are supplied current from a constant current source also connected to the source of the level-shifting transistor. The drain of the level-shifting transistor forms an output terminal of the amplifier stage. Each stage feeds its amplifier output negatively to the positive input of the other stage, while at the same time feeding its distortion and noise contribution positively, via input gain transistor conduction, to the other stage. Balanced amplified outputs are produced from either balanced or unbalanced inputs, and distortion and noise components are produced in common on both outputs for differential cancellation. Complementary-symmetry and power amplifier versions of the basic single-ended line-level amplifier are also provided.

If you are really adventurous here's the link to the patent, with full explaination

http://www.patentstorm.us/patents/5376899-fulltext.html

Posted just for fun

FWIW

H9

heiney9

unc2701 wrote:

Did Nak pay Pass for the design or was it a rip off?

In the words of Nelson Pass himself "they paid me quite handsomely to use STASIS"

H9

autoconsortium

I've been doing some reading today...seems the Bryston's have a 20 year warranty? Goodness, they must be built well. They really are marvelous amps, and the reviews I've read are very good. They were about $5,000 new, for the pair, so I think I did ok paying the $2,700 I did for both. Some of you have stated the PA7's need service here and there...and I am not in the mood for more problems. I have a large stereo system made up of all old school stuff, and I am about sick of reparing stuff. I love stuff from the 80's...and most everything I have is from that time period. I just recently got my Polk SDA SRS's to replace Carver ALIII plus speakers...I had a bad ribbon, and getting those fixed...well, that's a whole story in itself. I opted not to fix them because they sorely lack in bass. My Nakamichi Dragon had to be serviced less than a year ago. One of my old Adcom amps blew up for no reason. My Nakamichi OMS7 is now inoperable, and I'm sourcing a laser. It just never ends with this old stuff...but, I love it.

heiney9

autoconsortium wrote:

I've been doing some reading today...seems the Bryston's have a 20 year warranty? Goodness, they must be built well. They really are marvelous amps, and the reviews I've read are very good. They were about $5,000 new, for the pair, so I think I did ok paying the $2,700 I did for both. Some of you have stated the PA7's need service here and there...and I am not in the mood for more problems. I have a large stereo system made up of all old school stuff, and I am about sick of reparing stuff. I love stuff from the 80's...and most everything I have is from that time period. I just recently got my Polk SDA SRS's to replace Carver ALIII plus speakers...I had a bad ribbon, and getting those fixed...well, that's a whole story in itself. I opted not to fix them because they sorely lack in bass. My Nakamichi Dragon had to be serviced less than a year ago. One of my old Adcom amps blew up for no reason. My Nakamichi OMS7 is now inoperable, and I'm sourcing a laser. It just never ends with this old stuff...but, I love it.

I feel for you. I have a dead Nak cdp as well....no trouble with Adcom or my other Nak stuff. As far as the Dragon that's just regular maintenance. Just like a high performance sports car. I got rid of my Dragon quite a few years ago as I had no use for it. I used mine a lot since day one and never had an issue.

We've discussed the OMS-7 before. I hope you don't pay an arm and a leg for the laser and repair. Sonically, it's really not worth it. Many mid-level players will beat it today. My OMS 4 is just sitting here taking up space. If I ever feel inclined to repair it, it will be for sentimental reasons only. Those (OMS 4 & 7) use Burr Brown PCM-54 Dac chips and the newer PCM-63 is so much better and there is even a newer version of that, PCM-1502, I think. But ya gotta do what ya gotta do. You must have some reason for fixing it.

I wouldn't purchase a PA7 with the idea it is going to be completely trouble free and perform like new since it's about 20 years old. Although once put back into spec (if it's out of spec) it should give many many years of service. A 20 year Bryston warranty is hard to beat.

H9

fredv

autoconsortium wrote:

... Carver ALIII plus speakers...I had a bad ribbon, and getting those fixed....

Me, too; unfortunately.
Just curious, who fixed the ribbon, and what was wrong with the ribbon?

autoconsortium

Didn't do it. I repairmed them myself, but there are still issues. The Carver ALIII has a long ribbon. This part is not available anywhere, and only one guy has them, out of New York. He charges quite a bit to repair them, he used to work for Carver, one of the chief designers/elec engineers. One of my ribbons is old and stretched, and has a hairline fracture. I pulled the speaker apart and found some broken magnets. I repaired these myself, and it was quite a ****. Took four guys holding things together while I bolted it back up...they say you can't repair these yourself, you can. I like the midrange from these speakers, but they just don't cut it overall, like my SDA SRS do. They weren't worth me spending about a grand to have repaired to like new condition, so I went with the SDA's.

F1nut

Here's the info on Carver ribbon repairs, http://www.carveraudio.com/ribbonrepair.htm

Dave Sauter is a great guy to deal with, no worries. As stated above, repairing them yourself is a PITA.

New 48" ribbon units were available at one time from Parts Express, not sure if they still are.