Ray Samuels Audio B-21 Raider
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Ray Samuels Audio B-21 Raider
Ray is a veteran amp designer who has introduced numerous celebrated headphone amplifiers under his brand, Ray Samuels Audio. A former military electrical engineer, Ray has been applying his circuit design knowledge, fused with passion for music, building tube and solid state, as well as dynamic and electrostatic amplifiers. If it drives headphones, he’s done it.
The first time I met Ray Samuels was at CanJam Chicago 2023. Based in nearby Skokie, Ray made a rare appearance at CanJam to present his then-prototype of the upcoming B-21 Raider headphone amplifier. My demo of that prototype left an indelible impression on me. I shared those impressions back then in my show writeup. I was therefore thrilled when Ray reached out to me to be his first reviewer for his new amp. I received the first production unit earlier this year and had it in my chain for three months before sending it back to him, with a pang of regret. I am happy to report that the final product is just as good as I remembered. This amp is remarkable!
Like all RSA products, the B-21 Raider is named after a military aircraft. It is a singularly unique dual-purpose product: a solid-state Dynamic AND a solid-state electrostatic amplifier. Allowing up to 5(!) input sources, and blessed with endless reservoirs of clean power, the Raider is designed to be the first, last, and only headphone amplifier one would need for any headphones. Priced at $12,500, it is clearly aimed at the higher end of the headphone market. Its build and sound quality are equally impressive.
SPECS
Design Philosophy
The B-21 Raider comprises two equal-sized stacked components (which can also be placed side-by-side). At the bottom is the power supply, and above it is the amplifier (gain and output stages).
The fact that half the form factor is the power supply is neither surprising nor coincidental. I’ve come to appreciate that Ray’s secret sauce is his power supply design. The power supply, a separate component, shapes the sound. It includes 6 regulated power supplies. Ray uses the capacitors in the power supply to control the amp’s tuning, bringing more bass or brightness based on the level of capacitance. There are no capacitors in the signal path.
One of Ray’s goals was to build an electrostatic amplifier that will deliver warmth while keeping the mids and highs clear without making them bright. As he put it to me, “Who says that estats could not have a great bass?” His tuning reference in designing the amp was the Stax SR-X9000 headphones. To achieve his goal, he increased the capacitance in the Raider’s power supply to 470 µF (up from 330 in the earlier prototype, for those that may have heard it). There are a total of 8 capacitors in the power supply section: 4 on the positive side, and 4 on the negative side.
Following the power supply is a shared preamp section. Next is the output stage, which comprises of two separate amps: a dynamic amplifier (with 8 buffers) and an electrostatic amplifier (with 4 buffers). When the dynamic amp is in use, the electrostatic amplifier is put into sleep (goes to ground), and vice versa. The dynamic amplifier uses op amps from Burr-Brown and Linear Technologies.
There is no global negative feedback. Feedback resistors are used locally in the gain stage and as part of the op amps.
Power
Dynamic amplifier
The voltage rails of this amp swing 60V from +30V to -30V. The Raider easily drives the most power hungry headphones, the Tungsten; and, with a mind-bending calculated 15 watts into 60 ohm load, it has tremendous headroom in driving the Susvara OG.
The dynamic amp can safely handle loads as low as 5 ohm and can be paired with any dynamic or planar headphones (for the rare ribbon headphones edge case, a more qualified answer would be required).
Electrostatic amplifier
Bias is set at a standard 580V. The estat has its own separate, full regulated, power supply.
Power cable
Uniquely, rather than the customary cheap courtesy cable, the B-21 Raider includes a medical grade, high quality power cable that was selected for optimal synergy.
Components
Military-grade circuit-boards (which cost $500/piece) and military-grade components are used throughout to handle the level of power delivered. RSA uses custom transformers. The volume control is a precision DACT attenuator (which costs $600/piece). Clearly, much attention was paid to sourcing the components with quality in mind.
Break-in
RSA breaks in both amplifier and power cable for approximately 100-150 hours of continuous running before shipping them out. Nice!
BUILD & FEATURES
Build
This is a very well-built amplifier. I personally find its black-and-red design striking, with a nice balance between its anodized black chassis and red accents. It feels like a high-end sports car, and it is quite fitting.
For maximum isolation and esthetics, both components are fitted with metal spikes that sit securely on top of small metal discs (with felt at their bottom to protect your shelving).
The volume knob is large and smooth, providing very nice control.
Even the view from the top offers a satisfying contrast between the black chassis and the red hit sinks, as well as a nice touch of branding.
What’s What
Back
A supplied umbilical cord connects the power supply and amp components. One can connect up to 5 audio sources to the amplifier section: 2 single-ended via RCA, and 3 balanced via XLR. Perhaps you have a vinyl preamp, a reel-to-reel player, a CD player, a DAC, and a DAP that you wish to connect simultaneously?
Regardless of source, the amplifier internally is fully balanced.
Front
The front reveals a large and satisfyingly smooth red volume control to the left, and a red source selector knob to the right.
Two small switches in the middle play two big roles:
- “phones” – toggles between the dynamic and electrostatic amp sections.
- “gain” – selects a low gain of 11 dB or a high gain of 21 dB (a gain selector isn’t common on electrostatic amps as far as I can recall).
Headphone outputs
On the right, we have the estat amp outputs: two electrostatic “pro” headphones outputs can be used simultaneously.
On the left are the dynamic amp outputs: a 4-pin XLR output, as well as a dual 3-pin XLR output. I have nothing but compliments for this amp’s design, except here: in my humble opinion, the dual 3-pin XLR is vestige of times long passed and needlessly wastes space that could have been much more conveniently used for a 4.4mm or another 4-pin XLR output.
More importantly, this amp has no single-ended output. Please note that if your headphones or cable choice requires a single-ended output, this amp does not currently support that.
Customization
Ray will be happy to work with you in case you would like to make certain adjustments to fit your needs or tastes. Specifically:
- Tonal shaping – a measure of tonal control can be achieved by adjusting the capacitors in the power supply unit. Increasing capacitance (microfarads) will produce a warmer and darker tuning. This applies to both the electrostatic and dynamic amp sections. For example, if you have the Stax SR-009 or 009s, which are a little brighter, you may wish to add a bit more bass. If you look to pair the DCA Corina, which are bass heavy, you may prefer to brighten up the amp a bit to optimize synergy. And perhaps leave the default tuning as is with a Hifiman Shangri-La Sr. As a reference, to my taste, the default tuning works great with the Stax SR-X9000 headphones.
- Gain – there are 4 resistors used to control the gain (plus and one minus for each channel). In low gain, even at its lowest volume setting, the amp outputs a significant level, which is near the threshold for higher sensitivity headphones. There is no noise floor limitation, but if you plan to use high sensitivity, low impedance dynamic headphones, you may want to ask Ray to lower the default gain setting. He will be happy to do that.
- HE 90 output – if you are one of those rare individuals who owns the celebrated vintage Sennheiser Orpheus HE 90 headphones, Ray can convert one of the electrostatic headphone outputs to the appropriate connector and provide a 500VDC bias into it.
Packaging
I must complement Ray for the remarkable secure packaging of this hefty unit. Receiving it in this custom-cut, heavily padded, ruggedized case was confidence inspiring.
The total shipping weight is about 75 pounds, and it features wheels and a retractable handle similar to those on a large suitcase. I walked two blocks to FedEx to ship it back to Ray. It was a breeze..
SOUND!
Chain Used
Roon Nucleus+ streaming / NuPrime CDT-10 CD transport ➤ CAT 7a ➤ Audioquest Cinnamon RJ/E ➤ Bricasti M3 DAC (power cable: Cardas Reflection) ➤ Moon Black Dragon XLR ➤ Zynsonix switchbox (silver cabled) ➤ Moon Black Dragon XLR ➤ RSA B-21 Raider headphone amp
Dynamic Amplifier
I listened to the B-21 Raider with a wide variety of headphones, from low sensitivity planars to high-impedance dynamic headphones. The Raider can drive them all with massive power overhead and a quiet noise floor.
To my taste, I most enjoyed the dynamic amp with planar headphones. It is a bit over damped with high impedance headphones (there isn’t an available spec for its output impedance, but it’s evidently quite low as one would expect from a solid-state amplifier). That said, I find most solid-state amplifiers over damped for high-impedance headphones, so if that tends to work well for you, then it should work well here too.
The B-21 has gobs and gobs (and gobs) of power. It drove both my Hifiman Susvara (OG) and Modhouse Tungsten (DS) without breaking a sweat. I’ve spent most of my listening time with the Susvara and Tungsten, as well as with my ZMF Caldera (open) and Kennerton Rognir (planar).
The Raider creates a magical combination of a spacious sound along with a crisp and impactful bass. It is an uncanny combination that feels both airy and grounded. The sound stage is spacious with a great sense of clarity in which instruments are wonderfully layered. At the same time, bass is tight and punchy and not overly textured. If I indulge and wax poetic for a moment, the music washes over you like pristine snow water from a waterfall above, keeping you refreshed and alert.
In terms of voicing, the B-21 reminds me most of my prior CFA3 amplifier. If you are familiar with it, it’s a great reference point for what the dynamic section delivers in terms of both power and presentation. The CFA3 I had may have been tuned a hair brighter.
Listening with the Caldera to Aaliyah’s cover of “Got To Give It Up”, bass is tight and very satisfyingly snappy. Moving on to the Susvara, Mary J. Blige’s “Good Morning Gorgeous” sounds outright thunderous. These headphones can have a tremendous bass when driven with a great, powerful amp and, with the B-21 Raider, it’s a real treat. That song also showcases the instrument separation achieved in this pairing, with deep bass, lead female vocal, backup vocal, and occasional strings layered with clarity.
Moving to classical music, in Bach’s “Keyboard Concerto No. 5” performed by pianist Simone Dinnerstein and the Berlin Court Orchestra, the Susvara’s superior timbre really shines through. I had the privilege of hearing Simone Dinnerstein perform this piece live in NYC last year and this recording sounds so true to life. It is a great case of an amp getting out of the way and letting the headphones perform to their full potential without a chain limit.
Switching to jazz, I moved on to the Tungsten and played “On The Sunny Side Of The Street”, a wonderful track that showcases two powerhouse tenor saxophonists at their very best, Sonny Stitt and Sonny Rollins (as well as Dizzy Gillespie on trumpet and Ray Briant on piano; if you love jazz, I can’t recommend this entire album enough). On this particular track, the Tungsten excel in detail resolution and imaging. Every member of this jazz band is very clearly laid out in space, making one feel present at the very jam session.
My favorite synergy with the B-21 Raider’s dynamic amp was the ZMF Caldera. It may be the best solid-state amp on which I’ve heard them (including the Holo Bliss, CFA3, and Violectric V281; with the caveat that these comparisons are based off memory as I did not have these amps at hand contemporaneously).
Electrostatic Amplifier
I used three headphones with the Raider: Stax SR-X9000, Stax SR-007 mk1, and the Sennheiser HE 60 (aka ”Baby Orpheus”).
The HE 60 requires a 540V bias. While my unit does not react well to my Mjölnir Carbon amp’s 580V bias, it worked perfectly well with the B-21. I’m not quite sure why, but that definitely furthers the overarching usability of the Raider. As to the SR-007, these headphones require a powerful amp to reach their potential; The Raider drove them with ease.
However, my favorite pairing with the amp was with the X9K. That is not surprising, given the B-21 was developed and tuned with these headphones in mind. Ray’s primary design goal was to offer and amp that will drive the X9K with a great bass presentation while avoiding the more common brighter estat voicing.
I found the X9K on the Raider retained its excellent speed, air, and expansive sound stage, while becoming more grounded. The X9K have more bass elevation than most estats, but on some amps it can bleed over with a bit of a smear. The Raider’s crisp and snappy bass is tightly controlled, more of a “bite” if you will, making this pairing very synergistic.
Saxophonist Gerald Albright’s cover of “Winelight” has an arrangement with heavy bass guitar notes that can sound less than tight. With the B-21, the X9K manages to separate these notes successfully. In “Gasoline” by The Weeknd, there are bass notes that border on the sub-bass. The Raider manages to resolve them well, an otherwise challenging fit for most estat headphones.
A great reference for comparison is the Mjölnir Carbon, another powerful and highly resolving solid-state electrostatic amplifier, which I’ve had in my chain for the past few years. These two amps are distinctly different. When using the K9K with both, the differences were most notable to me along two key dimensions: mids are presented much more forward on the Carbon, while they are more laid back on the Raider; and the Carbon has a tighter center image, while the Raider is more open and spacious. They are otherwise similarly resolving, making the choice between them genuinely a matter of taste.
CONCLUSION
Ray Samuel’s latest creation brings to the market a uniquely positioned product: a Swiss-army knife that offers versatile utility coupled with sharp performance edges. The B-21 Raider uniquely offers both dynamic and electrostatic solid-state amplifiers in a single unit. It is intended to be a “one-and-done” component for those who want a headphone amplifier that will connect to every imaginable source and drive all available headphones.
One would wonder whether such a design results in compromises. What we have here, simply put, are two outstanding amplifiers packaged into a single product. Along with its stackable power supply, it offers tremendous utility in a relatively small footprint.
Priced at $12,500, the B-21 Raider is an expensive premium product. But when taking into account it would replace two high-quality amplifiers, say at $4-6k each with a small premium for connectivity, the rationale of its purchase may appeal to a wider market than the total price initially suggests. In terms of availability, RSA is now taking orders and expects to ship this amp over the summer.
Why might this amp NOT be for you?
I can think of two reasons. First, you may only be interested in dynamic headphones. While the power calibration of this amp can be tuned by Ray to your needs (see “Customization” section above) and the Raider will do a fine job driving your dynamic headphones, you would not benefit from the Raider’s main advantages and this amp may be an overkill for your needs. Second, you are committed to a path of separate chains in optimizing your dynamic and electrostatic chains and have the space (and spouse) to allow you to do so.
Why SHOULD you get this amp?
If you want a headphone amplifier that will let you connect any source you may have today or in the future, and drive any headphones you have today or may get in the future, this is your one-and-done. And, oh boy, does this amp sound great. Both its dynamic and electrostatic amp sections share a similar DNA, presenting a very spacious sound stage coupled with a grounded, snappy bass. The Raider has what seems like an unlimited reserves of power, delivered pristinely. This solid state creation provides simplicity in operation. In addition, you have the peace of mind of Ray backing up his products over their lifetime in case of any need. Finally… I think this amp looks really cool
I had the pleasure of spending three months with this amplifier in my home chain. During that time, it became an integral part of my daily music life, so much so that I sometimes feel like I am missing a limb in its absence. I cannot recommend it enough!
Jimmyblues1959
@goldwerger Yes, 19 years is a great run. Bought mine used several years ago and continue to enjoy it.
There's nothing better than the military spec components Ray uses in his amplifiers, to stand the test of time.
The durability and longevity of his products is proof of this.
There's nothing better than the military spec components Ray uses in his amplifiers, to stand the test of time.
The durability and longevity of his products is proof of this.
Syan25
I'm a Ray customer. Love his amps. I own 2
19 years.. that's a great run! and not surprising..