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Push-Pull or Single-Ended Triode?


Our physical characteristics and our preferences, our tastes, determine many important aspects of our lives, affecting our choices in a wide variety of ways. For example, we all hear and listen differently, and we all have our music preferences, and these personal, music listening-related capacities, traits, likes and dislikes, send us one direction or another when selecting audio gear. Some most like solid-state, while others prefer vacuum tube-based circuits. Among the latter, where we are when we’re talking about Allnic products, some prefer the sound of one kind of power tube and circuit, others something different.

M-2500 Push-Pull Monoblocks (300B version)

Fortunately, KS Park of Allnic understands all of these, and over more than 30 years in the industry has produced a wide range of products among the best of their types, giving us an outstanding number of superb choices. In the last couple of years, Allnic introduced two models of both Push-Pull and Single-Ended Triode (SET) monoblocks that not only give us the choice between those two types of circuits, but also among a range of power tubes.

 A-2500 SET monoblocks (845 version)

Regardless of which appeals to an individual, one can be certain that what the amplifer of one’s choice will do is make REAL MUSIC at home.

The power amplifiers under discussion here and shown above are the A-2500 SET and M-2500 Push-Pull monoblocks.

You probably noticed some similarities in appearance between the A-2500 and M-2500. Most obviously, the A-2500 and M-2500 monoblocks share the same chassis – to which the number “2500” refers. The casework and size are the same, and the monoblocks of each pair are mirror images of each other. So, what do the “A” vs. “M” designations signify? Allnic uses the “M” to designate “push-pull” circuit designs, while “A” has been the designation for SET amps. In short, then, the M-2500 and the A-2500 share the same chassis, but the M-2500 is a push-pull amplifier while the A-2500 is a SET amplifier.

They look similar. Are there other similarities? What are the differences?

M-2500 Monoblocks:
Push-Pull with choice of 300B, PX25 or KT150 power tubes


I have owned many tube amplifier designs over the years, and historically the push-pull type has never been my favorite. Each design approach has its strengths and weaknesses. The “power-tube flexible” M-2500, though, has hit the sweet spot between SET and typical push-pull amplifiers: it maintains the micro detailing, textural and overall finesse across the midrange that SET designs are known for while providing the dynamics, slam factor and extended and focused bass of a push-pull amp.

M-2500 - rear panel view

Bass control with a pentode push-pull presents with optimal accuracy. I suspect the SET characteristics can be attributed to the direct-heated vacuum tube rectification. In the M-2500, an NOS 5U4G or 5U4GB full-wave rectifier tube replaces the semiconductor diode in the rectification circuit used in the M-3000 MKII and Allnic’s other traditional push-pull amplifiers.

What the M-2500 provides is the power and dynamism of the Push-Pull amplifier combined with more than just a touch of the spaciousness, and 3D solidity and imaging typical of SET amplifiers – maybe not quite so surprising with the 300B or PX25 power tubes one can choose (30 and 20 watts output, respectively), but more so with the KT150 option – at 100 watts output!

I’m not alone in my assessment:

The M-2500s passed all tests with flying colours. Simply, they allowed the components upstream to sing & play with abandon.

Read the complete review to discover why Audiophilia’s Anthony Kershaw awarded the KT150 version of the M-2500 monoblocks a Star Component Award.

A-2500 Monoblocks:
Single-Ended Triode (SET) with choice of 845 or 211 power tubes

The A-2500 possess all the positive, well-loved, sound quality characteristics of the SET amplifier, a 3D and almost tactile soundstage, with a very spacious, airy, detailed, and outstandingly musical and emotionally engaging presentation. Unlike many SET amps, however, the A-2500 has incredible drive – a feature of KS Park’s circuit design which pairs tubes (input, driver, and output – and in the case of these two models, rectifiers) and Allnic factory manufactured permalloy-based output transformers to perfection. With either of the classic 211 or the 845 (both with 20 watts output) combined with an NOS 5R4WGA rectifier, the powerful, articulate, and detailed bass presentation in no way leaves me wanting. The 845’s low-frequency robustness is on par with my favorite power tube’s, the PX25 (an option for the M-2500).

A-2500 with 211 power tube

As the M-2500 exhibits a good dose of the “magic” of SET amps, the A-2500 has speed, dynamics, and rhythmic propulsion more than just a bit reminiscent of what is commonly associated with Push-Pull amps only. With the A-2500, prepare to be surprised by the excellence of the expected SET sound - and the unexpected benefits of real power-drive.

A-2500 – rear panel view

The A-2500 and M-2500 each have all the typical positive qualities of the type of circuit they employ but with sound quality characteristics that in many ways give us the best of both. They differ in many ways, but as I noted at the beginning of this post, what they can both deliver is exceptional musicality.

Which kind of musical “reality” do you prefer? The choice is yours!

I should add that Allnic also makes the A-5000 Direct-Heated Triode (DHT) 300B monoblocks.

A-5000 DHT monoblocks

A-5000 DHT features Allnic In-house manufactured HL2 and RS242 triodes!  300B by Allnic in 2023!

These 10 watt output SET monoblocks have a different chassis from the A-2500/M-2500 (hence the “5000” designation), but what really “sets” the A-5000 apart is the use of all DHT tubes, some quite rare. Consequently, it is a unique, very “purist”, and exquisite sounding product, the very best of the SET sound. 

To ensure supply, Allnic is now producing - in-house - stable, reliable and beautiful sounding HL2 and RS242 tubes, the input and driver tubes in the A-5000.

Yet another choice...

Here is a summary of the differences between the M-2500 and A-2500, and of the range of tube type/output power available for each.
M-2500 Monoblock Amplifier (Configuration at the factory only):
PX25 - 1st Stage 5654, 2nd Stage 12A4, 5U4G/GB Rectifier and PX25 x 2 power tube.  20W Continuous. Triodes in Push-Pull configuration.
300B - 1st Stage 6485, 2nd Stage 12A4, 5U4G/GB Rectifier and 300B x 2 power tube.  30W Continuous. Triodes in Push-Pull configuration.
KT150 - 1st Stage 5654, 2nd Stage 6S4, 5U4G/GB Rectifier and KT150 x 2. 100W Continuous. Pentodes (Beam-tetrodes) in Push-Pull configuration.

A-2500 Monoblock Amplifier (Configuration at the factory only):
211 - 1st Stage 6CM7, 5R4WGA Rectifier and 211 x 1 power tube. 20W Continuous Pure SET design.
845 - 1st Stage 6DR7, 5R4WGA Rectifier and 845 x 1 power tube. 20W Continuous  Pure SET design.
With the individual tube biasing, pairing is not necessary. Allnic circuit designs do not overdrive their tubes, and they tend to last a very long time. The M-2500 and A-2500 amps appear to retain this benefit.
To give you at least a rough idea of which of the “2500” monoblock amps might suit your requirements for output power, you can find a handy calculator for amplifier power requirements for various speaker sensitivities and SPL at:
Whatever choice you make, I am convinced you won’t be disappointed. Both monoblock amplifiers are available with approximately a two-week lead time to delivery.


A-2500 SET:     $19,500 USD.

M-2500 Push-Pull:
          300B/PX25: $19,500
          KT150: $18,000 (Sale!)

Since options are always great, if the M-2500 and A-2500 monoblocks are not exactly what you’re looking for, perhaps this is:

A-2000 25th Anniversary SE (Special Edition)

We still have a few of the special, “hot-rodded” edition of Allnic’s fantastic 100 watts/channel KT150 based stereo power amps available. This has to be one of the finest power amps available at anywhere near the price: $5,900!

The A-2000 25th Anniversary is a 100 watt/channel powerhouse and paragon of clarity and finesse. With the modifications it sounds even better, and for the price, we think nothing will be able to touch it. It’s a great way to end the A-2000 25th Anniversary’s production run, and a great opportunity, limited by number of course, for anyone wanting a brand new Allnic power amp, one that can drive virtually any speaker, “for a song”, so to speak.

Allnic Audio A-2000 25th Anniversary/SE is a 100 watt (KT150 beam tetrode) push-pull, stereo power amplifier. Like its integrated amplifier brother, the T-2000, the A-2000 25th Anniversary/SE is pentode/triode switchable “on-the-fly”, providing more than 50 watts in SET sounding triode mode. The A-2000 25th Anniversary/SE offers stable, resolute power in the proverbial velvet glove, along with amazing, revelatory clarity, incredible dynamics and drive, articulate and powerful bass, and standard setting low noise and distortion.

Review and award for the standard, not SE, A-2000 25th Anniversary – July 2021!

Part-Time Audiophile names the A-2000 an Editor’s Choice!

“It’s rare for me to review a product like this which is just so thoroughly sorted, and at what I find to be a very fair price…

If you’re in the market for an amp that does what the modern 100W per channel solid-state stereo amplifier purported to do; power anything big or small, do so quietly and with great character and flat frequency response, I’m here to tell you that you can do one better, and even get those magical glowing vacuum-sealed bottles while you’re at it. If you have an opportunity to lay ears on this amp—don’t miss it.”

-Grover Neville

For more details, please see the previous blog post just below this, and:

To discuss purchasing any of the above products, or any Allnic product, for the first time or to move up the Allnic product line, don’t hesitate to get in touch with me, John Ketcham, at Kevalin Audio.

If you’re in Canada, please contact Don Corby at Corby’s Audio.


And please, remember: quality trades are always welcome.

Kevalin Audio
Corvallis, Oregon

Website link: Kevalin Audio
Email or call John Ketcham:
Tel: +1 503–292–5592
Corby’s Audio
Freelton, Ontario

Website link: Corby’s Audio
Email or call Don Corby:
Tel: +1 905.689.1976
Toll free: 1.877.689.1976

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