Ray advised 100 to 200 hours of burn-in time, but I just got the Protector a few hours ago. I do think that the sound quality out of the box is good enough for initial impressions, but we’ll hold the final review until the amp has been properly burnt.
I really haven’t done much listening in the single ended, since that beats the purpose of having the Protector in the first place. But when plugged in to the single ended jack, the effective gain is lower and you need to crank up the volume higher than if you plug it in to the balanced jack. (In single ended, the effective gain would be half of that in balanced drive) Still, you can get the Protector to drive the HD650 loud enough through the single ended connection, though power wise it’s not as impactful as what you’d get through the balanced drive.
Moving to the HD800, driven balanced through the Protector, I found that again it was able to drive the Sennheiser to extremely loud levels. But loudness is not equal to properly driven, and so I find the Protector to be a weak combination for the HD800, which is not exactly designed to be driven from a portable amplifier. Also, the HD800 is extremely revealing of the source you’re using, and the Ipod’s DAC is far from what I would call a high end source.
Now, let’s go back to the HD650. The HD650 is legendary for having the biggest improvement when driven balanced. As a matter of fact, one of the biggest reason that makes me built my balanced Beta22 was to be able to feel the HD650 on a balanced drive. When driven balanced, the HD650 improves on just about every aspect, probably the biggest improvement you can find when moving from single ended to balanced. But that “transformation” has only been witnessed on big high end desktop amps, because balanced drive was never available on lower end amplifiers, let alone portable ones. So, I really wanted to see if the Protector got what it takes to transform the HD650.
At the same time, I pitched the Protector against the Lisa 3, just to see how the Protector compares to the most powerful portable amplifier on the market even today. The Lisa is humongous for a portable amp, but it also comes with quite a lot of power and a smooth, analog sounding sound, so it was worth carrying around the bulk. Keep in mind that the Protector has only been burnt for roughly 6 hours, and while I feel some harshness on the lower treble, I will wait until the amp is fully burnt before making any final judgments.
I’ve had the Lisa 3 for a few months now, and it has always been a very potent amplifier with a smooth and warm sound signature. The Protector has a lot of disadvantages than the Lisa, both in components (Like all newer portable amplifiers, the Protector uses SMD resistors, as opposed to the metal-film resistors used in the Lisa) and in size. The Lisa does sound more analog and smoother than the Protector. Bass punch on the HD650 was also stronger with Lisa, though the Protector has better control of the bass due to its balanced drive. I don’t know how far the burn in process can improve the Protector, but that’s not my main concern for now.
While the Lisa has enough power to drive the HD650, the HD650, out of the Lisa 3 still sounds like a single ended HD650. But the Protector, with the help of balanced drive, really takes the HD650 to another level. Gone is the boomy bass that’s often prevalent in the HD650, even with the Lisa 3. The soundstage widens, the imaging becomes clearer, and the ambiance more real when the HD650 is driven balanced from the Protector. So, while the refinement level of the Protector is still inferior from the Lisa, I do find that the changes brought by the balanced drive offers sonic improvements that the Lisa was not able to provide.
In order to be able to drive a headphone in balanced mode, the amplifier needs to be fed a balanced signal that consists of 3 lines for every channel: Signal (+), Inverted (-), and Ground. Unbalanced sources only output the Signal (-) and Ground for every channel, thus lacking the Inverted (-) signal needed. The Protector overcomes this problem by using a phase splitter chip, so it takes the Signal (+) from your DAP and generate the Inverted (-) signal (exact same signal but inverted 180 degrees), and so come up with all the necessary signals. There were some concerns about the phase splitter chip becoming a weak link in the system. Though theoretically those concerns might be valid, I didn’t feel any noticeable degradations in the implementation of the phase splitter in the Protector. On the contrary, as I have mentioned, the transparency, sound stage, imaging, and ambiance is improved through the Protector’s balanced drive. I think we can be satisfied with this solution, until someone designed a portable balanced DAC that can take the digital data from the Ipod.
While the Protector is far from the ultimate HD650 amplifier, I do feel that the Protector does a very good job of driving the HD650. Nothing feels really lacking from this combination, and if I need to be stuck with just one amplifier, I would be very happy with the HD650 and Protector combo. But of course, the Protector was designed to drive your custom multi driver IEMs (such as the JH13 and the UM Mage) to levels never heard before, and so that’s when the real review will come in.
In the mean time, while I’m waiting for the UM balanced cable to arrive, I’ll use this opportunity to put burn in the Protector to the recommended 200 hours mark. Stay in tune!
System for auditioning:
Headphones: HD800 with APureSound cable, HD650 with stock cable.
Source: Ipod Classic, ALAC files. Cowon D2
Amplifier: RSA Protector, Lisa 3 Standard
Interconnects: DIY Blue Dragon LOD. Kimber cable XLR to Protector adapter.