Forward: Lyle Cook was kind
enough to conduct the following PRX150-Pro review and send it to ARACOM
Amplifiers. I do not personally know
Lyle and I have never met Lyle in person, but I have talked to him on one
occasion by phone, when he was considering purchasing an amplifier from
ARACOM. Since our initial conversation,
Lyle has purchased an amp from us and recently, the PRX150-Pro
power attenuator. We sincerely
appreciate Lyle’s business.
Jeff Aragaki – ARACOM Amplifiers (August 09)
Now on to Lyle's Review:
I have had a chance to try out my PRX150-Pro a number of times with a number of different set ups. Although I have not tried all the attenuators out there, I suspect that you have created the best attenuator so far for playing electric guitars through tube amplifiers. Congratulations on developing a technology that makes sense from an electrical engineering standpoint, while also meeting the only test that really matters: the attenuators affect on the sound of the amplifier and speaker.
Mainly I used three amplifier/speaker set ups for testing, from low-power to high they are: (1) An Emery Superbaby through a Weber 10" BluePup, which is a good speaker for this amp. This runs at 6 to 12 watts depending mainly on the power tubes used. (2) A VRX22 (22/10 watt amp) through a Jensen PN12 12" speaker. I kept it on high mode for about 22 watts. (3) A Mesa Boogie 5/50 Express through the stock speaker for the combo. I kept this at the 50 watts setting. I compared the PRX150 against four other attenuators: (1) an Ultimate Attenuator (UA) with the bedroom switch and plexi-switch options. (2) A Weber Micro-Mass rated at 15 watts. (3) A Weber Mini-Mass rated at 25 watts. (4) A Weber Mass rated at 100 watts. I compared the Weber attenuator suited to the power level of the amp against the UA and PRX150 for each of the three amplifier/speaker set ups. I compared all the set ups in various ways, but below I describe what I found to be the most meaningful comparison for each of the different set ups.
Set Up (3) High Attenuation Test:
This high powered set up (Mesa Boogie 5/50 Express) was useful to run the high gain channel with the gain and master levels both set way up. This meant that all the attenuators had to be at very high levels of attenuation, which is a challenge for any attenuator. I took them down to conversational levels and also what I think of as bedroom levels. The PRX150 still seemed more transparent and was better able to preserve whatever dynamics are left at this level of attenuation. This set up was also useful for testing bedroom levels which is where a cranked tone from a powerful amp is capable of sounding very good if the attenuator is very good. Again at high (but not crazy high) levels of attenuation, the PRX150 was more transparent and the dynamics were noticeably better, than the Weber Mass and the UA. The idea of this test was to take a really cranked tone from a powerful amp and see how the different attenuators performed at high levels of attenuation. The classic circumstance of late night or apartment playing when you still want to play high gain stuff. I think each of these attenuators was acceptable, but on the two main criteria, transparency and dynamics, the PRX150 was the clear winner.
Set Up (2) Medium Attenuation Test:
This medium powered set up, the VRX22 (22 watt amp) was useful to get a really nice bluesy overdrive tone (Channel 2 at about 4/5) and use a great master volume control to have it has loud as I was willing to listen to. This amp is really good for this test because the master volume allows for a wonderfully natural tone. From this point I could attach each attenuator and go from the bypassed or unconnected sound down through the steps and/or dial. It is a really good way (per your suggestion) to see how the attenuator is affecting tone at high and low levels of attenuation. The UA to my ear has the greatest affect on tone throughout the ranges and is not as dynamic. The (UA's) tone coloring is not bad, but is like a very slight effect. You may even like the (UA's) tone more than what the amp/speaker is producing (I found it different and pleasing), but it is indicative of less transparency. The Weber MiniMass was in the middle, with again the PRX150 being the most dynamic and transparent.
Set Up (1)Low Attenuation Test:
This low powered set up is great for testing a cleaner sound with very little attenuation and then seeing what happens when more attenuation is dialed in. The Emery Superbaby (6-12 watts) is a very direct circuit and the tone control can be disabled. I can also disable the tone control on my guitar (it is one of the Stellartone settings). With a single ended amp this makes for very lush, harmonically rich, cleans. All attenuators do better (it seems to me) when they have less to do, but it is still an important test to make comparisons at slight levels of attenuation. Again I started at about as loud as I could comfortably stand and then played around a lot with slight attenuation. The PRX150 is jaw-droppingly good at steps A-C. With these steps you can get the volume down just a bit or bring the volume down a fair bit and the tone preservation and dynamic preservation is just outstanding. I love it for big cleans, which are still too loud for bedroom playing even with a low-powered amp. What it allows you to do with a single volume control amp like the Superbaby, is get the preamp and power tubes involved enough to really add some depth and then bring the volume down with what seems like complete transparency. The other attenuators also work pretty well at low levels of attenuation, but the PRX150 is amazingly good at this aspect of attenuation.
As you can tell, I am very impressed with your attenuator. It is better under all the conditions I tested. I will say that the Weber Micro-Mass at $70 with the ability to separately attenuate low mids and mid highs on two dials is a really good product at that price point. It works very well with the Suberbaby and all the Weber attenuators do better until they are pushed to their maximum attenuating levels, where they start to drag the tone down more noticeably. The UA is better at high levels of attenuation on its regular dial, but the bedroom switch, which can go really low has a very noticeable affect on tone, the plexi-switch can liven it up a bit, but is coloring the tone a lot. The UA does do a good job of attenuation, despite the somewhat negative comparisons above. If someone was less concerned with transparency and dynamics, it is very capable of producing good tone with a high degree of attenuation. To my ears it (the UA) does not suck tone, but does change it a bit. The UA is active with a fan and requires defeating the circuit protection at start up so it is not as user friendly as the Webers and the PRX150. The PRX150 and the UA are both larger units for attenuators. I like the amp-head-like configuration of the PRX150 more. The ability of the PRX150 to dial in the impedance going in and out is a real big plus because it means it can be used with just about any amp/speaker configuration and could even be used as a tool kit for impedance matching when attenuation was not needed (that's another reason the "A" step with slight attenuation and virtually no affect on tone or dynamics is useful because it allows for the PRX150 to be used for its impedance matching capability with very little attenuation thrown in. This is another exceptionally well designed product from ARACOM Amps.
PRX150-Pro Product Page
The PRX150-Pro's Advantages
UNDERSTANDING POWER ATTENUATORS FOR GUITAR AMPLIFIERS