Re-imagining "Class A" Amplification

lscangus

Industry Expert
Oct 23, 2018
164
157
130
36
Questions posed by the Members above are commonly raised questions from our customers and distributors.

We really wish we are the first ones to have cracked it! But we are not the first one using the idea of dynamic bias on the market, i.e. in the past, Krell was using a similar kind of technology for some of their products.

The heat dissipation of an amplifier depends on a lot of factors while many people usually consider only the BIAS ( class A, AB ). Some manufacturers decided to tune the bias much higher than required to classify an amplifier as Class A ( I guess mostly for sound tuning purposes ). Surely higher bias results in more drained current, energy losses, and heat.

But one important factor always being missed is the rail voltage. The higher the voltage the more heat is dissipated as the bias is draining. Because of the higher efficiency (impedance ) of modern speakers, we have designed the Rei to have a lower rail voltage compared to many amps on the market. A lower rail voltage will result in much less heat when the bias current continuously drains. For users who need more voltage ( bigger room or listening at very high volume ), we designed the Rei to be able to run in bridge mode to address those demands. Of course, a single pair of Rei will power a majority of today's top-class loudspeakers under normal operating conditions. That said, I enjoy the extra power of the Rei's in bridged mode when powering my Giya G1.

Then we may also think about the number of output transistors. Let’s say if two amps tuning both bias as 1A, holding all other factors constant. 10 transistors in total will be hotter than 5 transistors ( more or less twice at hot ). You may think the output power delivery of the 10 transistors amp will be higher, this is not necessarily true as different transistors have different current delivery patterns. We have chosen a transistor with a higher (compared to more typical ones) current delivery. By limiting the number of output transistors, and combining with the advantages we have with lower rail voltage as stated, together with the utilization of dynamic bias, the final result is much less heat dissipation than usual for Class A amplifiers.

The rated output is also one of the key points too. Using your example, Accupahse A75 designed the output at 60watt so as to double down to 1 ohm at 480 Watt. A choice we made very early in the design stage was to consider the majority of modern loudspeakers rarely dip down to 1ohm, and for the ones who do ( i.e. ribbon ), the impedance does not fluctuate that much. We do not need the Rei to double down to 1ohm, which allows us considerably more room to tune for higher power at 8,4,2 ohms.

The power supply is actually quite big in the Rei, as it only supplies to one channel of the Amp. Also for the performance of a heatsink, it depends on a lot of things. i.e. the airflow dynamic, material, material density, profile design, surface finishing, etc. It is not that a bigger and heavier heatsink must do better than a smaller lighter heatsink. For us, it's all about optimisation and choosing the right approach to all aspects of the design in concert with our design priorities.

Addressing the question concerning weight, if you want, there are lots of ways to increase the weight of an amplifier such as encasing the transformer, using steel rather than aluminum alloy, etc. Let’s say just by swapping out the top and the bottom cover of the Rei from Carbon to Aluminum and changing the main chassis to steel, the unit will be 5kgs heavier. But we have to do it this way for good reason.

We don’t know if the Rei will overturn some common concepts and ideas about Class A amplifiers, and, of course, we cannot make it overcome the laws of physics. That said, we just don’t want to make a usual or expected product - we want to advance the state of the art and at the same time produce, beautiful, simple products that will stand the test of time.

Rei is a real Class A amplifier

Sincerely, Angus
 

lscangus

Industry Expert
Oct 23, 2018
164
157
130
36
Yes, good explanation, but I want to know how ambient sound effects the operation of a heat sink.
pardon me. I didnt mean to say ambient sound will affect the thermal properties of the heatisnk.
 
  • Like
Reactions: Steve Williams

yyzSB

Well-Known Member
May 14, 2017
117
39
158
Does the REL Class A implementation have any similarity to the great sounding KRELL iBias Class A tech found in their new amps?
 

lscangus

Industry Expert
Oct 23, 2018
164
157
130
36
Si
Does the REL Class A implementation have any similarity to the great sounding KRELL iBias Class A tech found in their new amps?
Similar concept, but different execution.
 

Kingsrule

VIP/Donor
Feb 3, 2011
1,432
681
1,430
What is the US price of the Rei?
 

gleeds

Industry Expert
May 29, 2018
754
1,207
235
Thanks for inquiring. US price for the Rei monoblocs is $28,900 for the pair. We have a set of demonstrater amplifiers, as well as a range of Westminster cabling for those interested in a local audition. WBF Members feel free to DM me for further information.
 

gleeds

Industry Expert
May 29, 2018
754
1,207
235
You bet Steve! Appreciate you asking.

While Angus is putting more of the use and innovation details together I thought it would be fun to post Angus's home system.

Needless to say, with strapped Rei Monos (two per side) outputting approximately 500+ watts into his Vivid Gaya G1 at their nominal 6ohm impedance the sound must be impressive. What you may not notice is the two Quest pre-amplifiers run as mono L/R control units into each side of the strapped Rei amplifiers.

Apparently, Angus created this configuration at the request of a Japanese retailer. According to Angus while the result of strapping Rei amplifiers was well known, running the Quest pre-amplifier this way was not and the result was surprising. I'll let Angus comment since I have not yet had the pleasure of hearing our stateside Westminster gear arranged in this all-out fasion!

All cables are designed and hand-built by Westminster Labs. Source components are MSB DAC and Lumin X-1 streamer.

IMG_2171.JPG
 

gleeds

Industry Expert
May 29, 2018
754
1,207
235
Seoul Audio Show

In good company: the "small and mighty" Westminster Labs Rei mono amplifiers and Quest pre-amp with Aires Cerat, AlysVox, and Pink Fawn.


IMG-20220310-WA0003.jpg
 

microstrip

VIP/Donor
May 30, 2010
20,806
4,698
2,790
Portugal
Gary

Forgive my ignorance but is strapping the amps the same as bridging

Not forcefully, but in this case it seems to be so.

But strapping sometimes means connecting the input and output in parallel, or a more complex connection.

Bridging increases voltage, but not current. Strapping input and output increases current, but not voltage. Usually, bridging does not increase the class A power rating - but we get more power in class A/B.
 

gleeds

Industry Expert
May 29, 2018
754
1,207
235
Thanks for asking about this Steve. As you know, nothing is "usual" about Westminsters' approach. Rather than provide an incomplete or inaccurate answer on how Angus accomplishes this I'll defer to him. Of course, it's 3:30 am HK time so we won't wake him just yet:)
 
  • Like
Reactions: Steve Williams

lscangus

Industry Expert
Oct 23, 2018
164
157
130
36
Gary

Forgive my ignorance but is strapping the amps the same as bridging
There are two ways to scale the output of the Rei. The first way is bi-amping, so using 2 units to power a single channel with 2 pair of speaker cables ( only compatible with speakers which has two or more sets of binding posts at the back.) The second way is by bridging 2 units together, one unit responsible for the + phase and one unit responsible for the - phase. A special cable XLR cable and an additional ground cable ( connect between the + and - Rei ) is needed for this configuration.

This configure will double the voltage output when compare to the standard Rei. The Rei has been specially designed for this use and therefore it has the needed current to increase the power supply with bridging. There are quite a few amplifiers on the market which does this within the same box ( i.e. Accuphase A75 and Soulution 701 ), bridging across two boxes I think we are the first. Usually bridging amplifiers will results in higher audible distortions ( sometimes much higher ) , but with Rei, the difference is negligible.

This allows uses to scale the Rei in quite a few ways. 2 pairs in bi-amp, 2 pairs in bridged mode, or even 4 pairs in bi-amp-bridged mode. This is also the same for the Quest, a mono card can be inserted into the expansion card slot and the Quest will become a single channel dual mono output pre-amplifier, it is totally another level of performance. This makes it very easy for the user to upgrade their WetsminsterLab system by simply scale it up and reconfigure it, and one need not to go through the hassle and worry about selling the gears or what to do with the existing gears before the upgrade. More time to spend listening to music and "rediscovering your music".
 

skids929

Well-Known Member
Dec 31, 2020
202
98
93
54
These are Class A biased Amps, they are NOT "Pure" Class A in the true sense. At this wattage they'd burn a hole in your equipment rack.
 

lscangus

Industry Expert
Oct 23, 2018
164
157
130
36
These are Class A biased Amps, they are NOT "Pure" Class A in the true sense. At this wattage they'd burn a hole in your equipment rack.
#21 reply on this thread explains what we have done from the ground up to avoid this from happening. Is a different kind of approach compare to the rest of the industry.
 
Last edited:

lscangus

Industry Expert
Oct 23, 2018
164
157
130
36
I began my audiophile journey at 12. Fascinated by music and electronics I immediately jumped into DIY. Next, I worked in one of the top audio repair shops in Hong Kong, taking apart some of the world's best amplifiers from notable brands such as Krell, FM Acoustics, Accuphase, and Western Electric. It was there that I formed my concepts on amplifier design, ones that ultimately became WestminsterLab products. I was formally educated in the UK as an architect and worked in that field while my ideas for audio design continued to grow. I have come to understand that my architecture training has been a true asset in my approach to creating WestimisterLab products.

WestminsterLab formally began in 2015 with UNUM, an ambitious prototype amplifier project we used to showcase our technology at High-End Munich. Unum’s purpose was to create a technical tour de force and testing platform to demonstrate what the Company was capable of. Conceived as a solid-state Class AB amplifier, Unum displayed the power, speed, transient performance, and dynamics of much larger and more established designs.

As we looked ahead we did not think we could accomplish those same parameters with Class A but still believed in its promise and wanted to try. In the ensuing years, our team created the architecture needed for a Class A amplifier capable of satisfying these same parameters. As a completely original design, each aspect of the amplifier was adjusted until we the product was finally ready for production in 2019.

One area requiring great study was the consideration of building the amplifier with high- bandwidth (in the megahertz territory) that some manufacturers implement in their amplifiers. To achieve this bandwidth, we found an increased number of component parts and filters was unavoidable. Naturally, there were other parameters not yet taken into account. While jolly all good in a perfect world, unfortunately, in the real world components are not ideal. Simply put, no matter how good a component is it introduces distortions, colorations, and impurities into the music. The solution is to optimize the bandwidth of the design to perform up to around 40,000kHz, allowing us to achieve our low parts count and amplifier stability goals, as well as other objectives I have spoken to in an earlier post.

By using the noted bandwidth optimized for music reproduction we have also successfully addressed issues of power and heat generation from the initial creation of the schematics, selection of the finest quality, tight tolerance parts we successfully avoided using a more complex circuit and reached 100% of our goals. The result is Rei, a Class A amplifier having the transient, speed, dynamics, and control of a Class AB amplifier fused with the warmth, texture, and harmonics properties of Class A.

Rei’s presentation, however, cannot be simply characterized by a stated amplifier class. Instead, our proprietary design results in a nearly see-through quality described by top reviewers in Europe and Japan. The Rei is certainly not the typical Class A amplifier offered by the market. If you're intrigued I invite you to have a listen for yourself. WBF members in the US and Canada interested in experiencing our products may contact:

Gary Leeds

Hear This LLC

1 + 949-467-9808

gary@hearthis.us



In conclusion please allow me to share a quote from our website:

“The truth was a mirror in the hands of God. It fell and broke into pieces. Everybody took a piece of it, and they looked at it and thought they had the truth.” ? Rumi

We long for the whole, the complete.

The complete experience of music.

One may ask for one or several segments of the music experience - details, treble, bass, sound-stage, clarity, low distortion, emotional connection, etc. As life is good or bad, we are born or we die, laugh or cry, up or down, war or peace, love or hate.

One may choose either side.

At Westminster Labs, we are not choosing any such singular aspect - we hope as a result the whole reveals itself.

Angus.
 
Last edited:

skids929

Well-Known Member
Dec 31, 2020
202
98
93
54
#21 reply on this thread explains what we have done from the ground up to avoid this from happening. Is a different kind of approach compare to the rest of the industry.

Ok, so I will correct myself, it's Dynamic biasing. It's still not PURE Class A, Pure Class A is a linear circuit and not biased with any alternative technique. I am not doubting your circuit sounds great or has incredible genius in the design, but it's not Pure Class A. Nelson Pass has spoke alot about alternate Class A designs over the years. Again, I'm sure it sounds wonderful.
 
Last edited:

About us

  • What’s Best Forum is THE forum for high end audio, product reviews, advice and sharing experiences on the best of everything else. This is THE place where audiophiles and audio companies discuss vintage, contemporary and new audio products, music servers, music streamers, computer audio, digital-to-analog converters, turntables, phono stages, cartridges, reel-to-reel tape machines, speakers, headphones and tube and solid-state amplification. Founded in 2010 What’s Best Forum invites intelligent and courteous people of all interests and backgrounds to describe and discuss the best of everything. From beginners to life-long hobbyists to industry professionals, we enjoy learning about new things and meeting new people, and participating in spirited debates.

Quick Navigation

User Menu

Steve Williams
Site Founder | Site Owner | Administrator
Ron Resnick
Site Co-Owner | Administrator
Julian (The Fixer)
Website Build | Marketing Managersing