Review - sony ta-n7b power amplifier

The Fez

Well-Known Member
Sony TA-N7B

- 1977
- 160,000 yen
- 100w + 100w 8ohms
- 21kg
- Two independent monaural amplifiers
- Harmonic distortion .01%

First stage – Voltage amplifier. Dual FET input, a differential cascode amplifier, current mirror output circuit at the first stage and a bipolar transistor cascode amplifier at the next stage.

Drive stage – Fully complimentary push-pull power amp. – Sony V-FETs 2SJ18 & 2SK60 plus bipolar transistors in cascode configuration. Triple dual output configuration per channel.


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The TA-N7B is considered a statement product from Sony. Just looking at the rather small footprint of the N7B tells you it’s built extremely well. Designed and built up to a standard, a standard in the late 1970’s that was very high.

Sony’s aim in designing and building the N7B was to produce a state of the art audio amplifier employing the very latest and best audio engineering possible at that time.

Some 37 years later, those experienced with this amplifier and technically qualified may look now and see the flaws in the designs. I’m no audio engineer; I don’t claim to be of any technical expertise. But I do like listening to music, and this amplifier was no doubt built to reproduce music to the highest fidelity level possible.

Aesthetics, design, look? – It’s a matter of taste. I’ve had someone tell me the amp looks like a dorm refrigerator they had in college! – joking?, perhaps. When in the listening position and looking at the face, it is a very nice simple design. The backside, aint that flash in my opinion. It is unique that is the fact.



Restoration

The amplifier has undergone an extensive rebuild. Over 180 parts have been replaced.

Also, some discrete enhancements or modifications have been done to make the amplifier more stable and to sonically take it “up” to another level. The alterations were researched, tested, re-tested, applied, then re-tested, to exacting standards (as the N7B demands) to ensure the highest level of integrity, and sonic purity.

All replacements parts and substitues used are absolutely appropriate and precisely matched wherever required across all circuits.



Listening to the Sony TA-N7B

Plugged in and allowed to idle along at low volumes for a good hour before putting the foot down. It’s a bit like having a classic car restored, and you’re taking it out for a drive. You know it’s good, you know it’s been restored very well, but you just want to treat her gently.

Once warmed up the Sony delivers a beautifully balanced sound, with what I describe as -- elegant power.

A stupendously articulate and detailed delivery. Tonally, very refined and nuanced, nothing but the music is heard, in front of a completely silent background. But it is not cold or clinical. You will hear instruments and detail never heard before. You will hear a wavering in a voice or a backing singer, you never heard before. The layering and purity of the sound is quite amazing.



Source and recording quality is therefore an even more important element when running the N7B. Critical of source is the TA-N7B no question. Transient speed and dynamics are wonderful. It’s a “quick” amplifier this Sony, very quick.

Bass / low frequency is also superb. Mid bass, upper bass, low bass it’s all in there. The amplifier goes so low and with wonderful definition and control. Midrange and highs are also excellent. In particular vocals and piano is where the Sony excels. Voices and instruments seem to leap into the room with you.

The only “weaker” aspect perhaps is the stereo separation. Not as good as expected or doesn’t seem to be in the same class as the other aspects of the amplifier. It’s very good, but not exceptional. Certainly the Sony ESPRIT TA-N902 (the best soundstage I’ve heard in an amp) & the Yamaha B2 seem to have better sound staging and separation.

Speaker choices need to be considered. You want an excellent full range speaker that has excellent grip and control on the bass, images really well. I have developed an immediate case of – floorstandis speaker-upgradeitis. Speaker placement as always is critical. Set up precisely to get the best from the Sony.

Put a decent preamplifier with the N7B, one with reasonably high outputs. The N7B, as a result of the wonderful design, and sonics is a low gain amplifier. But that’s just the way it is.

A beautiful highly accurate, linear, low noise (no noise!) and dynamic amplifier. You’ll really enjoy listening to your music with the Sony



Equipment
- Sony TA-N7B Stereo Power Amplifier
- Emotiva XSP-1 Balanced Differential Preamplifier
- Squeezebox Touch (EDO)
- Audio-dg NFB1.32 ES9018 Sabre DAC
- Krix Apex Floorstanding Speakers – 4ohms
- Quad 12L2 Standmount Speakers – 6ohms
- Grave Science interconnects

Music
- Eagles - Hotel California – 192khz
- Rick Braun – Sessions II
- Tim Finn, Bic Runga, Dave Dobbyn – Together In Concert
- Steely Dan – Gaucho – 96khz
- Supertramp – Crisis What Crisis?
- Il Sogno – Elvis Costello
- Amy Winehouse – Frank[/SIZE]
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Give time for the new electrical components that have been installed in your N7B to 'bed-in'. The sound will change(for the better).
 
Bedding-in isn't so much applicable to this circuit. There are no electrolytic capacitors anywhere near in the signal path; there are actually very few at all. The filter/buffer capacitors of the secondary power supply were replaced, but that is a low power consuming circuit (for input stage and relay drive only), having a series voltage regulator on each rail, hence completely isolated from the PSU capacitors. Improvements were made in those voltage regulators though, as Sony's original design isn't exactly low-noise against today's standard. Fez' testimony above confirms that the amp is dead-quiet now.

There are, however, a number of film capacitors directly in series with the signal path as AC (signal) bypass capacitors across fusible resistors which are there for DC level setting. These film capacitors were replaced in this amplifier by polypropylene film capacitors, as these capacitors are truly distortion-free (referencing to various studies/publications by Douglas Self). He also measured that polypropylene has no reforming effect, and hence no bedding-in effect (as opposed to polyester film caps). I am using polypropylene (Panasonic ECQP) capacitors for many years, and they truly did very well in all repairs/rebuilds. Indeed, not the cheapest, and they are larger, but triple worth the price and effort.

If only I could have changed these fusible resistors by high-grade audio resistors, I would have, but in this map they are there for very good reasons and one should not fool around with them. The original ones don't like heat (and warm it is inside) and drift miles off their nominal value, slowly making the amp fading away. The new ones should hold better, much better tempco, and lower distortion (the AC signal goes around them anyway).

The only applicable bedding-in would be the reforming of the original large can power supply filter/buffer capacitors. The amp had clearly not played for many years. The ESR test (before reforming) at 100 Hz, 1 kHz and 10 kHz was nevertheless very good, and they were therefore not replaced. The rebuilt amp played around 3~4 weeks at my place prior to return, and indeed... the first week or so the lower frequencies are a bit blurry and not as sharp/crisp/dry as you would like it to be. After a good 3 weeks (say 200 hours), the reforming was clearly completed, and the sound was crystal clear across the entire (audible) frequency spectrum.

I am not sure if transistors do bedding-in, in general (to me) they sound best when new. Perhaps the sharp edges went off a little after 200 hours.

And when the amp was returned, the sound was absolutely superb. On the scope, while loaded, the risetime (after rebuild) at 30 kHz was still around 90 mV/usec, which is VERY respectable. All FETs and BJTs in the input and VAS stage where replaced (after 4 months research as Fez' mentions above), and the bandwidth at unloaded condition (constant gain without visual distortion at scope on triangle signal) was up to 300 kHz, and while loaded up to 180~200 KHz.

On the other end, the linear gain was dropped back to 10~15 Hz (originally around 40 Hz), before dropping off. Which explains the 'very low' as Fez says. Nice? Well, only if your recordings aren't boosted-up in the low end, an evil ever more often seen due to the bloody poor home cinema sets these days (Bose terror), and as such many recent recordings are a pain to listen to (unless you use tone controls).

The bandwidth and risetime are really good figures, and indeed this amp is bloody 'fast', and the dynamics are really impressive (from the absolutely quite background). The smallest detail in a recording is revealed, as I have not heard before. A finger touch on a cord, the bass drum as if in your living, separation between two very near voices, it's amazing.

It results in a very intimate sound, connecting yourself with the musicians. Downside: 3/4 of all your recordings are now in the bin....

But true quality and un-boosted recordings (all old quality vinyl) will come alive in your room as never before (if the CD player or turn table are up to it of course).
 
I'm wondering how much of the sound is due to the preamp vs the amp. I'm not familiar with the Emotiva, but the dual-mono design of this amp should not lessen the soundstage. Do you have access to some other preamps to try?
 
Not trying to speak for Fez, but he is comparing the N7B against the N902 ... which is another league (yet the N902 is also a dual-mono design). I had the same question back to him, and it is not that the N7B soundstage is bad, it's a little bit less, still very good :) Personally, I find the N7B sound slightly more 'spatial' over the N902 (I own both, like Fez).

Indeed, the N7B is a bit picky concerning pre-amp, as it is so accurate and non-colouring. The quality/sound of the pre-amp is therefore quite important.
 
Ha!!! Stereo imaging depth width and separation is brilliant its just not super brilliant like the other aspects...more listening is required. A tough gig but I gotta do it:) get other guys opinions too...

Sent from my XT925 using Tapatalk
 
I'm wondering how much of the sound is due to the preamp vs the amp. I'm not familiar with the Emotiva, but the dual-mono design of this amp should not lessen the soundstage. Do you have access to some other preamps to try?
Yes in terms of preamp I have commissioned a gentlemen in Melbourne to build me a very simple tube preamp with jfet buffer. I am looking forward to that one.

The XSP-1 is a great preamp and does sound bloody good. I'm still interested in trying a Sony TA-E88 with this amp too. [emoji6]
 
Thanks for your review Fez! Sounds about right ;)

I just put the TA-N7B back in my system, after having fiddled with a Yamaha C-4/M-4 combo for about 1.5 years.

The Yamaha's sound nice, but the TA-N7B coupled with a TA-E88B, the PS-X800 and SS-G333ES, well I have to say I had forgotten how great these all sound together. It might just be a Sony set, but damn...

So tight, so natural, it just flows. But I do have to say I somewhat agree with your reservations regarding stereo imaging seperation. Does not really bother me though, I have become less of an analytical listener throughout the years.

So, any additional comments after all these months ? I read you have been shuffling around with pre's in another thread, making the B-2 much easier to listen to ?

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I agree with Ozzie. Spatial is the word for the N7b. Remember this amp underwent a total rebuild. So its getting better the more it is played.
 
Recently I aquired a full working, unrestored TA-N7B. I would like to restore the amp. I am looking for a list with all the suitable replacement parts. Would anyone be willing to help me out here?
 
Another Sony TA-N7B review....

I have been fortunate to have Oilmaster restore my TA-N7B to his exact and meticulous standards. Similar to Fez, over 160 components have been tested, retested, and replaced for optimal audio synergy. The weak, dull sounding pre-restoration TA-N7B has been replaced by an amplifier that can sonically compete with modern day contemporaries.

My point of reference is an Accuphase A-60 receiving balanced inputs from an Accuphase C-290V preamp. For comparison purposes, I used the C-290V to drive the TA-N7B through the direct inputs (rather than c-coupled).

Listening

Oilmaster's rebuilt TA-N7B is by far the most detailed/ high resolution amp I have owned. I am discovering new details in tracks I have not heard before! The experience is similar to being retold a familiar story with new information. Music has an expansive, holographic- like sound stage, with vocals on some tracks that seemingly float in the air in front of me. Audio details are presented clearly against a black background. The TA-N7B does not have the "fullness" or warmth in the mids of the Accuphase but seems to be more balanced with its presentation, overall offering more detail to the listener.

Bass is fast, tight, and accurate. It seems double bass notes are reproduced more accurately than the A-60. Overall, I hear bass that is better defined with less bloat and boom.

I am sensitive to sibilance, yet the Sony's treble seems to be just right for me at my normal listening volumes (<60 db), however at higher volume levels on certain material it may be unforgiving (though this can vary from setup to setup). The amp demands high quality source material, and will not disguise it in any other manner.

Searching nearly two years for the TA-N7B, and realizing my own expectation bias, I can say the sonic payoff was well worth the effort. Much thanks to Oilmaster for his input and brilliant work! :beerchug:

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Equipment

- Sony TA-N7B Vfet Amplifier
- Accuphase A-60 Class A Amplifier
- Accuphase C-290V Preamp
- Lenovo X200 Thinkpad Streaming Tidal (Lossless)
- Uptone Audio USB Regen
- Luxman DA-06 DAC
- Tannoy Kensington (on loan)
- KEF LS 50

Music

- Tsuyoshi Yamamoto Trio - Misty
- The Beautiful South - Let Love Speak Up Itself (BBC Sessions)
- Air - Modular Mix
- Dusty Springfield - Son of a Preacher Man
- Soundgarden - Fell On Black Days
- Beethoven Triple Concerto, Archduke Trio, Storioni Trio (DSD)
- Keep Shelley in Athens - In Love With Dusk
 
Well that would be like comparing coffee and tea.
Both are hot beverages and exist in many flavors, each person his/her preference, but comparing based on what?
 
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