Westminster Labs REI Amp Eval

Audire

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In case you are not familiar, Westminster Labs REIs are mono amps.

https://www.westminsterlab.com/rei

The are relatively small and light weight Class A amps. Into 4 ohm speakers, such as our Magico M3s, they deliver 200w of Class A and if I bridge another set they will deliver 800w of Class A.

We will hopefully begin our demo eval this coming Friday. We will have them for app a week. We will post pics when they are delivered.

After this eval we are doing one more demo eval. That eval will be for the brand new model of BAT amps (solid state). We will only have a stereo amp in for eval, but if we enjoy them “more” than Pass and the REIs then we will be purchasing the mono version.


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Audire

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These speak of quality. From the non-magnetic screws that are used to put them together to the Aerospace Grade 6063 Aluminum of the chassis. It’s of the highest quality. The carbon fiber on top of the amps matches the sides of our M3s. It’s beautifully done. Nice touch.

From what I was told the warranty is reportedly 5 years. Their online manual is rather extensive - https://www.manualslib.com/manual/2184446/Westminsterlab-Rei.html?page=23#manual

They are light weight, which is unusual for most amps of this caliber - esp. in Class A. They get warm (but not as warm as our Pass 260.8s), but definitely not hot.

Set up is rather elementary. They are ready to play Class A out of the gate. Initial warm up time is seconds, but you have to wait 45 minutes to an hour or so to begin to get the full impact of what these amps can deliver. Having a second set bridged (800w Class A into 4 ohms speakers) would be very nice!

Our listening impressions will come later. But they are sounding very nice.

Pictures of Installation and Final Placement. Some pics with the Pass 260.8s reveals the size of these “small” Class A amps.

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Audire

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Initial Listening Impressions

They’ve only been on for 8 hours, but Westminster Labs REI Mono Amplifiers are the best amps we have ever heard. I didn’t think such was possible with such a light weight small Class A amp, but apparently it is.

We’ve pretty much all witnessed speakers disappearing, and even amps doing the same. However, with REIs even your walls disappear. These amps are absolutely amazing.

REI’s are very accurate, while retaining musicality. They have it all; presence, smoothness, texture, and immediacy. Play whatever you desire there’s no strain on these puppies. Love the way they control the low-frequency info (takes app 6 hours to come into full bloom - we leave the amps on). The music sounds deep and wide; they present a soundstage that’s off the charts. Excellent.

The REI’s have their own Class A signature sound. It’s unique. I’m not sure which other high end amp, that I’ve heard, they sound most similar too - perhaps Soulution 701s plus a touch of tube goodness. One audiophile has reportedly replaced their MSB amps with the REI’s. And another their DarTZell’s.

They produce a powerful beautiful Class A sound. Two audiophiles visiting today we’re also amazed.

I’m not sure yet if these are “the” ones for us, but they are exceptional. This said, we still need to hear the competition = BAT. This is their brand new amp that we will be hearing in about a week. We are also considering Audio Research 160M monos.
 

Audire

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I was really skeptical when I first read about these amps. But they are very special. My album collections have new life. I'm hearing what the Magico M3s are truly capable of. And WOW!

As a seed grows up to be a huge tree, these small amps allow the music to really blossom to new heights. I can’t think of a better word then “transcendent.“
 

Steve Williams

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I was really skeptical when I first read about these amps. But they are very special. My album collections have new life. I'm hearing what the Magico M3s are truly capable of. And WOW!

As a seed grows up to be a huge tree, these small amps allow the music to really blossom to new heights. I can’t think of a better word then “transcendent.“
As I've said several times, these are giant slayers
 
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Audire

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These amps are under serious consideration for purchase. They continue to sound amazing. The best sound we’ve heard to date. But if we purchase these it will probably be two sets - not just one.

At this time, we’ve eliminated the Audio Research 160M monos from any further consideration. This leaves the new model BAT monos (the stereo version should be here later this week) and the Soulution 501 monos left to consider.
 

Steve Williams

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Yes, 700w of Class A into our 4 ohm Magico M3s. If one set of REIs sounds this “perfect” what would two sets sound like? We’ve had a number of people over now. Their mouths are dropping in awe at the sound. I’m not sure it can be beat - esp at this price!
You’re hearing exactly what I heard. Pretty amazing for the size and the price. I know there are several members who have sold their Uber expensive amps and replaced with REI
 
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Steve Williams

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I’m betting that several owners will move up to a bridged set. At the price it would be difficult to avoid temptation
 
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Ron Resnick

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I may have missed the answer to this comment, but an amplifier that is automatically varying bias is not true Class A.
 

Steve Williams

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I may have missed the answer to this comment, but an amplifier that is automatically varying bias is not true Class A.
You missed it. Yes
 

Audire

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I may have missed the answer to this comment, but an amplifier that is automatically varying bias is not true Class A.


lscangus puts it this way:

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.
 

Audire

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I get the feeling that this thread has had a predetermined outcome since it began.

The only predetermined thing is that I think I’m getting new amps.

I have already had some other evals (EMM MTRX2 - it’s here somewhere). I have a new BAT model coming in as well later this week (I hope). I’ll post pics when it (new stereo amp) arrives. Then there is also the Soulution 501s. Both of these amps and the Pass 600s were mentioned above, along with Audio Research 160Ms.

I don’t know much about BAT except they are appreciated in the high end community. But I’ve already heard Magico and Soulution and this combo has real synergy. I believe the 701s were at High End Munich 2022 paired with Magicos. I wish to explore the 501s closer.

Lots of listening to do before we make a final decision.

If you do a home eval of the REIs I believe you would see why I’m so excited about them. But things are always subject to change.

Please see, Re-imagining "Class A" Amplification
 
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Ron Resnick

Site Co-Owner, Administrator
Jan 25, 2015
11,378
6,679
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Beverly Hills, CA
lscangus puts it this way:

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.
Thank you!
 
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