Bryston 7BST 600 Watt Monoblock Review

[MAB]

That sort of stuff can happen when the grounding scheme is, let's say, less than perfectly starry.

The little Yamaha Pianocraft receiver I gave to my parents for their PC has a buzz behaving the opposite way, so I presume the wiring coming from the pot may be picking up interference electrostatically from the adjacent display unit.

Side note, the noise we're seeing in the Bryston is really suggesting some sort of inductive pickup. There must be a loop that's coupling to the transformer wiring.

Thanks Steph. I'll keep you posted. I always suspect relay contacts too. They were the prime culprit of the mains noise in my Mitsubishi preamp. I cleaned them and eliminated the majority of the noise.

I am going to replace, but need to make a header to adapt the replacement relay to the old pinout. Cleaning seems only temporary measure in most cases.

I also suspect the edge connectors to the amp modules, simple removal and insertion with some contact cleaner to help.

My amp is a bit more tidy compared to the earlier picture.

I haven't even checked the bias yet.

 

[MAB]

No one will know those current “miracles” like LA90, PA5, B100, B200 and similar little boxes 30 years from now. They will be forgotten.

So true. And none of them have the ability to drive extremely difficult loads. As you know, a few of those you mention can barely drive even reasonably low impedance speakers.

 

[PristineSound]

No one will know those current “miracles” like LA90, PA5, B100, B200 and similar little boxes 30 years from now. They will be forgotten.

100%

They were intentionally made to be disposable and forgettable.

And unintentionally designed to be unreliable.

 

[daniboun]

No one will know those current “miracles” like LA90, PA5, B100, B200 and similar little boxes 30 years from now. They will be forgotten.

Forgotten because they will not have resisted the ravages of time or forgotten because they will have aged badly?

 

[Timmeon]

Totally unrelated to sound quality, but I have always been bothered by Bryston’s cartoonish logo.

The logo is the first reason I was drawn to this brand. It's perfect.

 

[sceptical1]

The logo is the first reason I was drawn to this brand. It's

Edited for off topic content.

 

[sceptical1]

Some misinformation here about the history.

Stuart Taylor redesigned the Bryston amplifier line which is called the ST series. The ST amps are different than older, not rehashed. The schematics are different. They perform and measure differently, the older amp about 4x higher distortion than the ST, although still awesome. Stereophile has a good interview I linked in my previous Bryston review. Of course, a rehash of the 1978 design is quite a compliment, and actually reason to buy older models with confidence.

Stereophile did measure the SST they are roughly equivalent to the ST series, with a few incremental improvements here and there. All of these various generations have performance that exceeds most any high power amp offered today.

Used isn't for everybody... But for those who are shopping for used gear, to exclude the older Bryston models from consideration one would have to ignore this review with some remarkable measurements from a 36 year old pair of amps, from a manufacturer with legendary reliability reputation, with a matching after-sales reputation for ongoing support of their gear.

Not exactly.

 

[sceptical1]

No one will know those current “miracles” like LA90, PA5, B100, B200 and similar little boxes 30 years from now. They will be forgotten.

I don't know about you. I would take a Boxem 4216 over any amp past or present. For $1200 it's a no brainer.

 

[EJ3]

Not so bad for a 1993 amp

Mine are 9 years older & (through the LAB inputs) have a SINAD of 95
(one of my personal ones was tested here on ASR [some of these old amps do pretty dang good]):

NAD 2200 Vintage Amplifier Review​

 

[RogerSmith]

Nice to see that a company which produces solid and nicely designed gear with 20 years warranty also measure very good. Thus swalling the price tag even becomes almost bearable.

 

[Bob101]

Bryston amps will always have a special place in my heart.
Warning: long story going nowhere in particular ahead.
In what I can unapologetically call a previous life as an aspiring recording engineer, I had the opportunity to work in a lot of recording studios. It was hard work, and getting paid was not part of the job. Instead I was let loose in control rooms with more knobs and buttons than I could count, all of which I was actually allowed to turn/push/pull. The studios ranged from little more than a room with a mixing console in a corner with a Tascam MSR16 in the closet, all the way up to 24-track Protools (three 888 interfaces!). Outboard gear was king, and plugins were only just starting not being frowned upon. The best studio I worked at was run by a drummer who, after a very serious car crash, designed and built a recording studio from scratch on a plot of land next to his house.
Entering any control room in 1999, the only surprise awaiting you was the size of the ubiquitus Genelecs. But on that morning what I saw were the then top-of-the-line PMC studio-monitors, tri-amped by Bryston monoblocs (six total). I had never heard of Bryston, nor PMC for that matter.
My sound-engineering career never really took off, and now being just a humble audiophile, I still dream of owning a pair of PMC speakers coupled with Bryston amps.

 

[pma]

Thanks Steph. I'll keep you posted. I always suspect relay contacts too

Yes. I have similar photos of power relay deteriorated contacts in my archive. For such reason I moved to solid state relays with 90A MOSFETs (own design) more than 10 years ago. Not a single problem with them.

 

[daniboun]

My sound-engineering career never really took off, and now being just a humble audiophile, I still dream of owning a pair of PMC speakers coupled with Bryston amps.

PMC are expensive and don t measure well...
You have many other speakers that are really better for half of the price....

PMC Twenty.21 Bookshelf Speaker Review

This is a review and detailed measurements of the PMC Twenty.21 Stand-mount Speaker. It is kindly loaned to me by a member and costs US $2,000 but member purchased it used for much less. Professional Monitor Company (PMC) is a UK company so keep that in mind when looking at pricing. Their...

www.audiosciencereview.com

PMC result6 Monitor Review

This is a review, listening tests, EQ and detailed measurements of the PMC result6, active professional monitor (speaker). It is kindly sent to me by a member and costs US $3000 for a pair. I have to confess: this is one ugly looking monitor! Let's hope all the accents are functional. The...

www.audiosciencereview.com

 

[AudioSceptic]

I recently reviewed a stack of classic Bryston gear, including a 3BST amplifier. I was pleasantly surprised at the good results. I have the big brothers of that 3BST amp, the 7BST monoblocks. I also recently built a resistive load with enough capacity to test such a powerful amp. Here is a test of this classic amp.
View attachment 480210

I got the amps used years ago. They have powered a range of speakers. They have been reliable. Mine were manufactured in 1999 according to the date code. I have never opened them. I have no idea what the previous owner did with them, except they appeared well-cared for when I bought them 12 years ago.

It has balanced inputs using TRS or XLR, and unbalanced RCA. It also has 'parallel' and 'series' modes. The amp is actually two modules, which can be operated bridged, or in parallel. It can drive very difficult loads in the parallel mode.
View attachment 480203

5 Watt 1 kHz Performance Dashboard
Following usual ASR practices, using the amps' balanced inputs with a QA403.
4 Ohm Parallel Mode
View attachment 480191
96dB SINAD lands it at the bottom of the excellent category. This is a pretty good result despite the mains noise. I wonder if that is age-related.

4 Ohm Series Mode
View attachment 480192
SINAD degrades to ~90dB in series mode. Much of it is increased noise. Which makes sense since the amp is bridged in this mode.

8 Ohm Parallel
View attachment 480193
8 Ohm Series
View attachment 480194
Again, excellent performance with degradation in series mode compared to parallel. We will later see how much power is available in each configuration.

Lastly,
2 Ohm Parallel
View attachment 480195
2 Ohm Series
View attachment 480196
Excellent performance at this moderate power level into 2 Ohms.

Power Output
Here is the THD+N vs. Power for 8, 4, and 2 Ohm loads. Parallel and series modes were measured except for 2 Ohm load which I only measured in parallel. I also didn't quite make it to 1% distortion on each run, call me a chicken!
View attachment 480156
In any case the amp exceeds the following power figures at 1% distortion:
2Ω Parallel: 775 Watts
4Ω Parallel: 475 Watts
8Ω Parallel: 250 Watts
4Ω Series: 850 Watts
8Ω Series: 610 Watts

I didn't want to redo the runs to 1%, suffice to say they have a ton of power.

The amp has clipping meters incorporated into the faceplate's LED:
View attachment 480201
Onset is about 2% THD, the LED start turning amber. By 3% distortion the meters are lit up solid red. I tested a second amp and it has the same clipping threshold for the LED. They provide very useful feedback. They look tasteful, yet appropriately urgent when they turn red.

Here is the THD alone across power for the various loads and mode:
View attachment 480157
The amp did get warm doing these high power sweeps, but didn't complain, protect, or blow a fuse.

Distortion and Nose across frequency
Looking at THD+N at 4Ω in serial mode across a range of power from 130mW to 200W, the amp shows little dependence of distortion and noise across frequency.
View attachment 480166
4 Ohms in parallel mode, even better performance.
View attachment 480170

Here is THD alone into 4 Ohms in parallel mode, the amp is well controlled across frequency:
View attachment 480172

IMD / Multitone distortion
Here is the intermodulation distortion at 5 Watts, 19 + 20kHz
First into 4 Ohms in parallel mode:
View attachment 480173

And into 4 Ohms in series mode:
View attachment 480174
Both are great results. I can see some noise at 35kHz that goes away in series mode. Looking at Bryston's description from the owner's manual:
View attachment 480175

View attachment 480178
Is this out of band noise at 35kHz getting nulled in bridge mode? Or did something get turned off in my house? Not sure, I can't hear it, but interesting.

Here is multitone into 8 Ohms, parallel mode:
View attachment 480179
19 bits of distortion margin, 16 bits including the noise.

And serial mode into 8 Ohms:
View attachment 480180
18 bits of of distortion margin, and 14 bits of noise margin. The amp is noise limited, still excellent performance.

Frequency Response
Here is the frequency response into the three loads, in parallel and series modes:
View attachment 480182
-3dB down at 60kHz or higher depending on load and mode. The parallel mode has the most extended response at a given load resistance, which isn't surprising.

Matching
Here is the performance of the second 7BST compared to the one I just tested.
View attachment 480189
Except for some slightly questionable noise the second amp (right channel, red trace) is matched to the first, after 35 years of use.

I'm glad I measured these, and didn't blow anything up. I now have a better understanding of the parallel and series mode. I also wondered if the amp was as clean as I thought it was into low impedance loads, which it is. I've driven Infinity Kappa speakers years ago, and even more difficult speakers with the previous version of the 7B, and it worked well never overheating or shutting down, sounding great. This confirms my impressions of it's performance.

I hope this is interesting, and encourage questions and suggestions.

Bryston has always had a good reputation and it's good to see it fully justified.

 

[AudioSceptic]

I was just about to write the same thing. I got these amps used, Bryston encourages that with the transferable warranty and the fact they still support all of their gear.
Also, the 7B is fairly unique in that it can legitimately drive ultra-low impedance speakers. Infinity Kappa and IRS, Apogee, etc. The only competition at the time that could do that were well over twice the price of the Bryston. And likely not close to the reliability and serviceability. And all of those competing brands are gone or sold to aggregated companies that don't support the original products.

I also personally don't like unreliability and unserviceability, so am willing to pay more up front.
Three of my four Adcom pieces are gone due to reliability, the GDA-600 DAC being the only remaining unit that still works.
I am pretty sure I have wasted enough money on Topping's unreliability to buy a used 7B off of eBay.
So putting aside my dislike of unreliability, I probably saved money compared to any other 600-800 Watt.

This hobby isn't really about saving money though... If so, I would probably stick to Miles commercial amps. Dirt cheap, unbreakable, and able to drive absurdly low impedances and still sound good.

Yes, but best is probably to forget all about "separates" and instead get pro powered monitors from Genelec, Neumann, etc.?

 

[Billy Budapest]

I've never owned any Bryston gear but I never thought their logo to be cartoonish.
On the other hand, I like G.A.S. and SUMO gear (I never owned any of it, either).
I guess that you could consider their labels "cartoonish".

I don’t think the G.A.S. and Sumo logos are cartoonish. Just the Bryston logo.

 

[MAB]

Yes, but best is probably to forget all about "separates" and instead get pro powered monitors from Genelec, Neumann, etc.?

I use these to power a pair of JBL M2 monitors that I built. So yes!
That being said, I still enjoy passive speakers, I've owned a couple models that are difficult to drive, this amp is ideal for that too. There are still passive speakers that I desire.

 

[sceptical1]

The quad complementary circuit was Chris Russell's design.

The sst series have the mjl type transistors in a to-264 case, far superior to the old to-3 types used in pre sst units.

As far as 4x less distortion, there is no less distortion even in the current amps compared to the 1983 models when an additional compensation network was added to the input pairs to reduce hi frequency thd to mid band levels. The thd was below .005% then and it is virtually the same now.
Every circuit update in the past 40 yrs. addressed noise levels until the cubed Salomie circuit and even that reduced thd by only 6db. An amp that makes the benchmark look like a topping pa5, btw.

Even the split gain configuration was Chris' idea, carried over from his two stage phono amp. Not exactly genius when 100x=40db and 10x + 10x=40db it's just that nobody thought of it before and it took 20 yrs. for the guy who proposed it to implement it somewhere else. Maybe Otola was still taken seriously years after he speculated that doing that would increase TIM.


Even so, speaking to the level of refinement associated with the amps you need to look no further than a photograph of this 7B and a 20 yr. old 4BSST, there is no comparison. That includes longevity, those mjl devices reduced failures from some to none. Finding someone who has had to service his pre sst amp is easy, for sst and newer almost impossible. Still, if you want to buy a pre sst amp you go right ahead.

A 'star' grounding method is a myth carried over from the hardwired, tube days. No amp with a pcb has one or needs one and I have never seen it done.

 

[PristineSound]

An amp that makes the benchmark look like a topping pa5, btw.

You mean from a power perspective?

 

[Waxx]

I'm not surprised with these results at all. They were long the cleanest amp i knew from subjective side, and without sounding cold like many older class D amps did. They were also the standard in amps for music studio monitoring (before all went active) for a reason. So the results are what i expected.