Arcam Alpha 9P Amplifier
by John Stafford
My favorite demonstration of the 97 Montreal Show was by Gary Nicholson of Emerald Audio Resources, the Canadian distributor for Arcam. He was demonstrating Arcams strategy of biamping to get further performance out of their highly successful Alpha-series amplifiers. I had inquired about my older Alpha 6 Plus and using this technique, and Gary replied that there was a pre-out mod for the Alpha 6 Plus that could be done to take advantage of this strategy. If I didnt like it, I could at least use my integrated amp as a preamp. All Arcam amps have the same gain, and any integrated/power or power/power amp (with any preamp) combination in the Arcam lineup can be used together. If youre unfamiliar with gain or input sensitivity, think of it as the percent that the amp boasts the signal it receives. You can have two amps with different wattage ratings, but have the same gain, the amp with the lower power rating will start to clip at lower volume levels than the other.
I managed to get my hands on the mod kit, which would normally go to the dealer for installation. It retails for approximately $100 USD and it is not difficult to install if you can read a circuit board and are moderately handy with a soldering iron. I would rank it as harder than a Parts Connection DAC-2, but easier than the associated upgrade kit. The installation requires soldering five lead wires to various locations on the circuit board, the most difficult is to the lead at the base of a small JFET. A heatsink will help ensure you dont damage the JFET. With modified amp on hand, I was now ready to try this biamping thing out for myself.
For biamping duties, I received the Arcam Alpha 9P. The Delta series has been merged into the Alpha series, so if youre keeping track, this amp replaces the D290. It is a 70Wpc amp with a monstrous toroidal transformer, two switched speaker outputs, and it even has a headphone jack. I found this odd because in the amp/preamp combo world, it is the preamp that will usually have the headphone jack. While the headphone amp is not as good as the one in the Anthem Pre 1L, (which is designed by Headroom) it is quite respectable, and I found it to be a pleasant addition to an already worthy amplifier.
The one thing that concerned me was the thin sheet-metal shell the amp uses, with the big transformer and internal heatsink I was a little worried about the durability of the amp. However, even when I was really cranking out the tunes, the amp stayed cooler than most. The placement of the heatsink is unique on this amp. It is fairly large, internal and centrally placed with grilles that make an oval pattern on both the top and bottom and only where the heatsink is. This way, you get top-to-bottom air flow through the middle of the amp.
Opening up the unit, you get the feeling that you are listening to a toroidal transformer and heatsink wrapped in aluminum foil. The two are very large in comparison to any of the other components. I say this only because I had difficulty placing it on my home-brew vibration sink. I use a Therma Rest inflatable camping cushion under a slab of 3/4" MDF under each of my components to help with isolation. You might call this a more attractive variant on the inner-tube isolation that so many people use. With the transformer off to one side and the unit being quite light otherwise, I found that I had to use a few sand-filled freezer bags to balance the unit effectively. I guess this is what I get for being cheap when it comes to isolation.
I used a Rega Planet CD player alone, or an NAD 514 CD player as both an integrated player and a CD transport to provide bits to an Audio Alchemy DDE v1.2 DAC. These fed the Arcam equipment, or Anthem Pre 1L / Amp 1 or Blue Circle BC3 preamp / BC6 amp combinations. These in turn drove either Ruark Crusader II or Gershman Avant Garde speakers. Cables were Stager silver interconnects, Canare Quad Star, Cardas Quadlink, or XLO Pro.
Listening to the Alpha 9P
On its own, and used with a variety of preamps, I found the Alpha 9P to sound very nice, with fast, lean bass if somewhat lacking in extension. This made for great pace and rhythm, but on speakers that go down to the 35Hz region or lower, there was a lack of detail in the lower registers. I found this particularly on tracks with abundant bass detail like "You Look Good To Me" on Oscar Petersons We Get Requests [Verve 810 047-2]. Of course, there was plenty of slam and drive, particularly in the midbass. This made for great reproduction of tracks with lots of drums and electric bass. I actually preferred the Arcam over amps worth quite a bit more when it came to pop and rock tracks. One particular winner was "Money," on Pink Floyds Dark Side of The Moon [Capital C2 46001]. Roger Waters bass line was full of attack and rock solid at some pretty extreme volumes. Its fun when the wife and kid are out of the house on a Saturday afternoon!
The mids were detailed and quite smooth for amps in this price range. This amp is certainly leagues ahead of the Alpha 6 Plus integrated amp, but when stacked up against some of the more pricey tube amps, you will know that you are listening to transistors. On stringed instruments like violin or cello, you get the heart of the instrument, if not the soul. The highs are quite good as well with plenty of sheen and very little grain. If I were to complain, I would prefer a little less splash. I guess I am a tube guy at heart after all.
All of the above relates to listening to the amp on its own with either the pre-out on the Alpha 6 Plus, the Anthem Pre 1L, or Blue Circle BC3 preamps, but what about all of this biamping nonsense? The basic premise is that if biwiring can improve the overall sound of you speaker, why not keep the bass driver(s) from interacting with your mid-range and/or tweeter at all by using a separate amp?
Lets quickly review why we biwire in the first place. We do it to keep the bass driver from creating a signal back through the crossover and messing up the signal going to the midrange/tweeter. I saw an experiment at the Science Centre here in Toronto that demonstrates the phenomenon quite well. At one end, there is a handle with an electric motor, with wires leading to the other end of the display which has an electric motor that is also attached to a handle. The experiment shows that a generator is just an electric motor that you move by using an external force. Thus, you can spin the handle at either end and make the opposite handle turn using electricity that you create.
OK, but werent we talking about biwiring speakers? Well if you think of a speaker driver as a generator, and you push the driver in and out with your hand, you are creating signal back through the circuit the same way as the handle in the Science Centre. Bass drivers are big and heavy and have inertia of their own, so they tend to move more or less than the signal that the amp is generating, and that, in itself, can create a small signal that interferes with the audio signal going to the tweeter and midrange. The theory is that if you biwire, it keeps that signal from the inertia of the woofer far enough away from the other drivers to keep the audio signal "clean." I find it works on some speakers better than others. The next logical step after biwiring is to keep the signal completely separate by biamping.
The whole is greater than the sum of the parts
After messing around with the Alpha 9P alone, I was ready to try biamping. The difference is quite large and very easily heard by even the most uninitiated music lover. I even demonstrated it to my mother-in-law. (I know, get a life, John!) The point is that this is not something you need to listen carefully for. The difference is immediate and quite apparent.
So what happens? The improvement is right across the board. Better detail, smoother mids, cleaner highs, and more extension on the bottom end. You even get better imaging and soundstaging to boot. Is it better than everything else in the world? No, its just better than any of the individual components can do on their own. I would consider it equivalent to multiplying the value of the amp and preamp individually by 1.5. Hows that for an arbitrary number?
Lets paint a more concise picture of the tonal improvements with the different combinations.
The largest difference is going from the Alpha 6 Plus operating as a preamp and the Alpha 9P as power amp. Lets face it, this is a budget integrated getting an add-on preamp section; its not going to be the most competitive preamp in the world, but the combination beats the integrated on its own, with cleaner mids and a more authoritative bottom end.
What is interesting is that the biamped combo beats the quality preamps used with the power amp only. This is a case of a less expensive combination sounding better. The differences are more subtle, but the bottom end gets more extension while keeping that great pace the Arcam was already providing. The imaging is the other department that really improves, with the image coming into much better focus and going deep into the soundstage.
Arcam suggests that you use the bigger amp to drive the woofer, but I found that the opposite worked better for me. The older 6 Plus has a bit more grain in the mids than the 9P, so I actually preferred the 9P driving the top end and the smaller amp handling the woofer. You get a little less grunt, but I always prefer to improve the midrange first and then look after the rest.
I had a chance to play with some cabling between the integrated and power amp. I found that the combination was quite sensitive to interconnects, and particularly the length of interconnect. I had two pairs of Stager interconnects available, 1m and 2m pairs. By far, the best combination was to put the 1m in between the two amps. Also, I found that if I had a better 1m interconnect than a .5m interconnect, the improvement was reduced when the shorter cable was used between the two amps than when used between the CD player and preamp. Based on this, go with a half meter of your favorite interconnect, if possible.
Its at this point I have to fess up and provide you with a couple of warnings about biamping. Never change the cabling with the amps turned on or you could be sending them to the repair shop. You also need to be sure you take the jumpers out from between the binding posts. Youd be surprised at the number of people who think they are biwiring, even though they havent taken the jumpers out. If you touch any of the speaker cable connections with both amps on, you will be changing fuses at a minimum, and causing serious damage to both your amps and speakers in the worst-case scenario. Much to my embarrassment, I had to send both amps in for repair once and one amp in twice. Gary at Emerald Audio Resources told me that I wasnt a record holder in this event, apparently another reviewer did it three times, so Im vindicated to some extent. It is easy to get lulled into a false sense of security swapping cables in and out with one amp, but you need to be downright paranoid when you are biamping.
Repeating our top story
Ive covered a fair bit of ground here, so Ill recap what I discovered.
The pre-out mod is an easy upgrade to your older integrated amp. I would go for it to biamp, but I would hesitate to recommend it to turn your integrated amp into a preamp. The newer Arcam integrated amps all have a pre-out now, so this is only for those of you with the older models.
The Arcam 9P is powerhouse budget amp that excels at pop and rock. The biamping strategy takes two budget amps and propels them well beyond their price points. Two amps are better than one.
Copyright © 1998 SoundStage!
All Rights Reserved