SPEC RPA-MG3000 Stereo Power Amplifier

My first encounter with a SPEC is now from about 6 years ago, at the Munich High End audio show , where we bumped into the Audiotweaks booth and soon had a fascinating conversation with Piet de Vries. We exchanged tickets and agreed that I could try a SPEC in my audio rack one day. And that later turned out to have far-reaching consequences....

In English they have the beautiful all-embracing term: 'gamechanger'. The
SPEC RPA-W7 EX power amplifier was such a game changer for me. It came, saw and conquered. And then it never left? Yes, it did... But not before a replacement came along in the form of the next SPEC, the RPA-M99. Which until today, and hopefully for a very long time to come, provides juice to the speakers on a daily basis.

But what if the opportunity arose to play with big brother, the SPEC RPA-MG3000 stereo power amplifier, for some time? I'm certainly not going to let that pass!

Big Brother

The RPA-MG3000 is the second largest amplifier in the stable of this extraordinary Japanese firm.
SPEC has set itself the goal of building amplifiers that can compete with the finest tube amplifiers. The makers of SPEC are themselves lifelong fans of (single ended) tube amplifiers.

SPEC RPA-MG3000 stereo eindversterker

Class Stugge?

Here you'll find a great story about the origins and pre-history of SPEC Corps. SPEC amplifiers operate on the Class-D principle. But you can immediately forget that again. Soundwise, it could be any amplifier: A, B, AB, tube (!), and there the best of their class.

A SPEC is definitely not a stereotypical Class-D amplifier. I myself sometimes jokingly call SPEC a gender-neutral amplifier, which if it had a passport would have a check mark next to the 'X' in its operating principle.

RPA-MG3000 Stereo Power Amplifier

The RPA-MG3000 consists of two large enclosures, one for the power supply, the other for the amplifier electronics. The amplifier combo is quite larger than I suspected from the pictures. I was given two huge boxes to carry in my car.

The dimensions, 45 x 18 x 45 cm (W x H x D), of the enclosures are identical to the manufacturer's flagship, the RPA-MG1000. But this one even has four cabinets. Where the left and right has its own amplifier and power supply housing.

Big but manageable

The weight of the power supply cabinet is considerable at 27 kg, but still quite manageable. The enclosure with the amplifier electronics is less heavy at 18 kg. Little chance of a hernia this time....

The amplifier and power supply are connected with two XLR cables. Errors are excluded here by using XLR terminals and plugs with different number of pins.

Front

On the front of both cabinets you will find no switches or controls. Only a light indicator bar, which on the amplifier is a lot wider than on the power supply.

back

SPEC RPA-MG3000 stereo eindversterker

On the back of the amplifier we see the 3-pin XLR terminals for balanced connection and cinch terminals for single ended use. The SPEC has very solidly built speaker terminals, suitable for either loose wire ends, spades or banana connectors. And of course we see the already mentioned two XLR terminals for connecting to the power supply.

Then there are three rotary switches. One of which is for setting the:'gain', or input sensitivity. An input selector switch, for the choice between XLR/ cinch, whether or not using the SPEC volume control module discussed later. And another rotary switch to switch the amplifier to stereo, mono or mono bi-amp mode.

SPEC RPA-MG3000 stereo eindversterker

There is also another somewhat mysterious switch with caption: Soundmode '1' and '2'. The difference between the two modes is subtle but audible.

My own preference turned out to be slightly with the switch on position 1. But as I wrote: it remains (fortunately) subtle.

What does SPEC itself say about this?

Stant 1: Neutral: very close to the actual sound of the instruments
Stance 2: Refined: Artistic quality that goes beyond the actual sound

It is a very different method than that of a conventional tone control. The frequency response does not change at all. Both modes depend on the adopted parts themselves.

But isn't that a job for a preamplifier? No! The Class D circuit has a very sensitive point.
In the post-stage of Class-D, musicality can be effectively changed.

We don't change the frequency characteristic. We only change the resonance characteristic of special components in the post-stage of Class-D.

Power Supply

SPEC RPA-MG3000 stereo eindversterker

At the back of the power supply cabinet, things are less exciting. Besides the IEC AC input and power switch, there are only the 4 and 5 pin XLR jacks to be found.

And a sliding switch for the light indicators on the front: on/half/off. I must say that I can quite appreciate the beautiful diffuse long light bars. Looks pretty classy on the otherwise empty front.

The top cover is heavy and very solid with the sandwich construction that I know from other SPEC amplifiers.

Typical SPEC

The wooden base and device feet in the red-brown color are a typical feature of SPEC. Several types of wood were used: Maple, Spruce and Hickory for the feet.

SPEC claims that the wood contributes a lot to the overall sound experience. I think it's especially beautiful. It gives the SPEC amps a timeless look of their own that makes them stand out from the grey masses from a great distance.

Inside the box

SPEC RPA-MG3000 stereo eindversterker

In the power supply enclosure we find a large 800 VA R-Core power transformer. The rectifier diodes are screwed against the bottom plate. Two thick power supply electrolytics of 15,000 µF provide voltage smoothing. A smaller power supply PCB takes care of powering the pre-stage and volume control electronics.

How does it work?

I thought the RPA-3000 was a power amplifier, right? Yes, in the main it is. But SPEC has also built in a capability to control the output volume. For this purpose, a box with a built-in volume control is connected to the amplifier via a long cable. There is even a choice of a sober cabinet and a luxury one. 

SPEC RPA-MG3000 stereo eindversterker

Volume Controller?

Yes, how does it work? This beautifully built H-VC1000 volume controller? It will come as no surprise that turning the rotary knob allows you to control the output volume. But connecting more sources also requires a box with inputs and channel selection.

And then that long wire connection(!) from the amplifier to the H-VC1000... Well, the first thing that comes to mind is "how can you think of this?". Apart from the fact that the volume control is a pretty pricey thing too!

SPEC RPA-MG3000 stereo eindversterker

The H-VC1000 volume controller

Pure Direct Connection

SPEC calls its own volume control method the: Pure Direct Connection, as you can see in the picture below. As so often, a picture says more than a hundred words. Let me put it this way: I find it, especially in view of the experiences that can be read further on, all a bit of sought-after hassle.

Surely an 'ordinary' preamplifier is much more convenient to use? Yes, it certainly is. When using a preamplifier, the control electronics in the RPA-MG3000 for the volume are put out of service with a switch on the back of the amplifier housing to turn it into a real power amplifier. We'll get to work on it....

SPEC RPA-MG3000 stereo eindversterker

Integration

I got to live with the SPEC amp in my living room for quite a long time, before it was moved to Marco's audio rack for a few more weeks.

The MG3000 set can also only just fit on my audio rack in terms of depth. After some moving and shifting of equipment, the amplifier set got a nice spot on the top of the audio rack.

In addition to being used with the H-VC1000 volume control, the SPEC also connects to the Bespoke Audio Co. control 'amp' via Townshend Fractal XLR cables. This allows me to compare the two methods nicely. The speaker wiring is the Shunyata Python. With the ToneMasterXL speaker systems on the other end.

SPEC RPA-MG3000 stereo eindversterker

The back of the H-VC1000 volume controller

The sources are the Audio Creative BerryStreamerXL for audio streaming, Garrard 401 with Audio Creative GrooveMaster III tonearm and DS Audio DS-01 cartridge/ EQ combo for the analog delights. And tape and cassette decks from Pioneer (the 707) and Nakamichi (Dragon and 700ZXL). Only the SPEC M99 amplifier has been exchanged in my normal daily used music set. In order to be able to make a real comparison between the amplifiers.

With the exception that last week that the RPA-MG3000 amplifier was in my audio rack the PS Audio Stellar 3 PowerPlant also came in.

Listen

The amplifier runs on 230 volts 24/7. I don't have to feel guilty about that with these amplifiers. I listen to music at different times throughout the day. I usually get up early with coffee, a sandwich and some music. Coffee time? Just a record under the needle! After work? A few hours of relaxed music enjoyment. A day without music is a day not lived!

SPEC RPA-MG3000 stereo eindversterker

The SPEC H-VC1000 volume controller at the listening position. The connecting wire is just visible.

It is nice that I can immediately compare the daily used M99 with this big brother. It is a feast of recognition. The typical beautifully smooth, spatially generous character that I know so well from the other SPEC amplifiers is so ear-pleasing....

After a few days it is clear to me that the guys from SPEC managed to stretch the upper limit of the RPA-MG3000 a bit further. The all-important midrange is as natural as it gets, and sweet as honey. Already a strong point in every amplifier from the SPEC stable I have experienced, but here it all goes a bit further.

In a direct comparison, however, this is most striking. The whole spectrum, from low to high is sublime. The room placement, the transparency, everything is right. I've never heard it better here at home. And I don't remember it that way outside the house either... 

Bespoke

Could it be any more beautiful? Listening with the volume control unit in front of the nose goes beautifully. But compared to the using the MG3000 as a pure power amplifier and the Bespoke Audio Co. as a preamplifier, the SPEC way of controlling volume has quickly fallen off.

It turns out that the Bespoke Audio Co. TVC combines downright magically with the RPA-MG3000. When I use both on the fly side by side and interchangeably, I permanently put the SPEC volume control back in the box after a few hours. After all, with an amplifier of this caliber staying in my audio rack for a limited period of time, I want the maximum listening experience for my ears...

SPEC RPA-MG3000 stereo eindversterker

The beautiful Red Cactus capacitors, a familiar sight in SPEC amplifiers.

Considerably more pleasant

Besides the point that I find the amplifier set with Bespoke Audio Co significantly more pleasant to use, I get the very best listening results with the RPA-MG3000 power amplifier. What a wealth to have an amplifier like this in my audio rack. And what a wealth to the luxury to use it with the Bespoke Audio Co. as well. I fully realize what a privileged person I am..:-)

In addition, I also dare to make the somewhat bold statement, "If the guys at SPEC only listened to the MG3000 through their HC-V1000 volume control, they never fully experienced how sublime their amplifier really is." The SPEC/ Bespoke combo propels the MG3000 to a level I have never experienced myself.

SPEC RPA-MG3000 stereo eindversterker

The SPEC volume controller in the foreground and the Bespoke Audio Co. on the left above it.

Not exactly new

So is the SPEC volume control that bad? No, of course not! After all, between black and white there are many shades of gray. The Bespoke Audio Co. is stupidly that good. That was clear from day one that it came into the house. No active preamplifier or volume control can match this. There, we've said it anyway....


This, as usual with the opinion culture of our time, is bound to generate some commentary. But that, as always, fascinates me three times: 'Not now, not then and not ever'. 

SPEC RPA-MG3000 stereo eindversterker

De Klasse-D eindtrap met laagdoorlaatfiltering.

SPEC RPA-MG3000 stereo eindversterker

Red Cactus en de Ruby Mica condensatoren.

SPEC RPA-MG3000 stereo eindversterker

Measurements

The output power in an 8 Ohm load I measure at 122.1 watts. In 4 Ohm it is 223.8 watts.

For maximum output power 912 mV is needed. This can be attenuated by means of two switches at the back of the amplifier with -6 and -12 dB, respectively, as desired. Very practical! This makes it easier to match the power amplifier with a connected pre/control amplifier. With my Bespoke Audio Co. TVC, the -6 dB setting proved to be the most ideal in my situation. Also considering the high efficiency of the used speaker system.

Thus, on average, the volume control can be used very practically around the 10:00 position. Which gives a pleasant control range. It is so annoying when a volume control has all its control range in the lower part of it's rotation range.

For 1 watt of output power, 84 mV is needed. 201 mV and 369 mV (with the different positions of both switches mentioned above). Very nice. With these options the MG3000 can be partnered with any preamplifier.

The THD+n distortion was measured with a low-pass filter so as not to let the figures be unduly affected by the modulation frequency used in class-D operating amplifiers. The SPEC may not sound like a typical class-D power amplifier, which of course it is.

The distortion I measured at the time with the M99 was extremely low. It is no different with this RDA-MG3000. The Audio Precision shows 0.0009% THD+n at 1 watt/8 Ohm. 10 watts of output power gives 0.0044% on the meter and 100 watts 0.095%.

SPEC RPA-MG3000 stereo eindversterker
SPEC RPA-MG3000 stereo eindversterker
SPEC RPA-MG3000 stereo eindversterker

The frequency response shows the -3 dB point at 45 kHz. Almost identical to the measurements on the other SPEC amplifiers. Whereby it should be noted that the frequency response is somewhat influenced by the height of termination resistance/impedance. Purely for a better sound experience SPEC chooses not to use the low-pass filter in the output in the loop of the feedback.

SPEC RPA-MG3000 stereo eindversterker

Big amplifier, big energy use? Not so. With the volume control turned all the way down, or no music playing, the SPEC RPA-MG3000 sips 14.3 VA from the wall outlet. You won't find it much greener. And no matter how loud you listen, the amplifier always stays cool. This predicts a very long life for the electronics used. And a long life of maximum listening pleasure.

With the current rapidly rising energy prices, amplifiers such as those of SPEC earn themselves back faster and faster, compared to the still beloved big class-A power supplies or fat tube amps...:-)

Anything else to wish for?

Yes, or rather, more of an idea. The first thing that occurred to me upon unpacking was: why such absurdly large enclosures? After all, SPEC amplifiers do not require large heat sinks.

For the even more exclusive RPA-MG1000, I can imagine it. You want to radiate prestige and you do that with large cabinets. Men who want to look important also drive big S.U.V. cars.

But for the RPA-MG3000, in my humble opinion, with enclosures that are roughly two-thirds the size of the current one would be much more manageable. Especially in terms of placement in or on an audio rack. The electronics would still fit in plenty. Oh well, one must always leave something to be desired....

Epilogue

Where the SPEC RPA-MG3000 is certainly even more beautiful than my own M99 is in the oh-so-important midrange, which has pure magic in it. So beautifully smooth and organic. I never get tired of this.

In particular, this is where it simply goes one or two steps further than with my daily used SPEC. And it should be, with a price tag that is by no means uplifting anymore, conservatively speaking. But let's be honest: I'd be disappointed if the MG3000 wasn't better!

In one sentence? The SPEC RPA-MG3000 is the very best amplifier I have ever had the pleasure of experiencing in or outside my home.

No, I'm not going to warmly recommend the MG3000. After all, there are only a very limited number of lucky people who can pull this off financially. But if you have the opportunity to listen to this amplifier set? Do not hesitate!

I can live perfectly with the smaller brother from the SPEC stable. But should the national lottery be calling at my door any time soon? Gooooood evening Dick! Then I won't hesitate for a moment!


SPEC RPA-MG3000 price: 34.990,00 euro

Links:
Audiotweaks
SPEC Corps

SPEC RPA-MG3000 stereo eindversterker

The SPEC RPA-MG3000 set at Marco in his audio rack

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Dick van de Merwe

Dick van de Merwe is een echte buizenveteraan. Zijn Triodedick zelfbouw projecten worden wereldwijd door hobbyisten gebouwd. Reeds vanaf 1997 deelt hij zijn kennis via geschreven en on-line media.

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