Phoenix Gold S400.4 Amplifier
I would like to first thank Morgan and Kevin with AAMP for setting me up with this amp to review. There are pretty much no PG dealers in my whole state, so I have a better chance of seeing aliens in a cornfield than I do seeing one of these amplifiers in a store display. Getting a product out to someone like me for a review of it says a lot about commitment to their fans, and I really appreciate the opportunity to pick this product apart. I am a big fan of "old school" PG products, and have had mixed feelings of the company and its products during the turmoil of the past several years. Since AAMP acquired PG last year they have put a lot of effort into getting the company back on track, and hopefully by the time you finish reading this review you can form your own opinion of how far they have come, or if they have succeeded.
Packaging:
This amp is packaged in the same box as the S1000.1 amp I reviewed previously. Using the same box for two amps cuts costs, and I am all for any cost cutting on things not directly related to the amp when it is installed. There is a mistake on the box, the photo of the power supply is not from an S series amp. Having gone over both the S1000.1, and now this S400.4, the photo is not from either amp, and is actually of a lesser amp which uses only a single sided circuit board. Sure, a mistake on the box is really not a big deal, but since it is of a lesser amp, I think PG is ever so slightly shooting themselves in the foot by not showing the correct guts, which are far more impressive. Like the other new PG amps I have reviewed, the box is sealed, and has final quality sign off information on it.
As with the other PG amps, this has one heck of a great warrantee (three years). It is pretty hard to find manufacturer confidence like this these days. A set of wrenches and two high level input harnesses are included in the box. The manual is universal between the S1000.1 and this S400.4, again, a cost savings I am glad to see.
Cosmetics / Features:
Like the S1000.1, this amp has clean and effective cosmetics. At a bit less than an inch longer than the S1000.1, it is still very small. Pretty impressive PG can pack 4 Class A/B channels into such a small size.
It has nice set screw terminals for solid and reliable connections. A power LED, and a protect LED as well. You may notice in the below photo one of the feet is bent slightly. Mounting the amp should bend it back, but I still was just a bit surprised to see a bent foot, when none of the other feet were, nor were any on the S1000.1.
On the configuration end are 4 RCA inputs, 4 high level inputs, bass boost for the rear along with an LPL control, the crossover frequency controls, crossover configuration switches, and the gains. I am a bit disappointed to find there is no 2-4 input switch, so you are stuck using "Y" cables if you only have a stereo pair of RCA lines to the amp.
I don't think this amp should have the high level inputs, and I have a few reasons for this. One, they take up space which should be used for a 2-4 input selector switch. Second, a -12db pad on the input (via switch) would allow for running high level inputs directly to the RCAs. I have not come across a lot of DIY people doing high level inputs, this is most often done by installers at shops, doing some sort of factory integration installation. In these cases the installers could use RCA pigtails and the -12db pad to hook the amp up for high level input. A good installer should know they need to engage the -12db pad to run higher voltage into the RCAs.
I have one small gripe with the crossover, it is only 12db/octave (second order). On its own this is no big deal, but with the S1000.1 having an 18db/octave (third order) crossover, I would have liked to see them match for blending purposes when installed. In the real world this probably won't be a big deal, but it is a detail worth mentioning.
On the bottom of the amp is a fan and some vent slots in the sheet metal.
I am very confused as to how the fan can do anything. When the amp is mounted to a flat surface, the heatsink sits against the mounting surface along with the slightly bent ends of the sheet metal bottom. There is no place for the air to flow anywhere. PG has informed me simply moving air around inside the amp is sufficient to keep it cool during power tests.
Build:
This amp packs a lot of "stuff" in a very small space. Here are some of the highlights...
The fan is a simple and thin model.
There are four power supply switching MOSFETs and a big enough transformer for the power rating of this amp. Two dual diodes are more than enough for power supply rectification.
This amp uses TO-247 outputs. Yes, you read that right, TO-247 outputs in an amp only the size of a few stacked DVD cases!
Plenty of capacitance for the rails and the inputs.
Here are those heavy duty speaker terminals.
The preamp section is dense, but organized. There is a separate board for the second crossover.
There is one tiny daughter board with surface mount components on it, related to the LPL control.
The bottom line here is the amp has plenty of parts to meet its rated specs, and they are well organized.
Performance:
I was quite skeptical as to what the S400.4 could do on paper. After opening it up I was confident it would perform. Here are its RMS ratings...
At 14.4V...
40W x 4 into 4 ohm each channel
55W x 4 into 2 ohm each channel
110W x 2 into 4 ohm bridged
I first tested the amp with one channel loaded at 4 ohms (no other channels loaded). I used a 1kHz tone and ramped up output to max unclipped voltage.
13.81V is good for about 48W of output. I next did the same thing except with a 2 ohm load.
11.42V is good for about 65W of output. Finally, I loaded the whole amp with two 4 ohm loads and the amp bridged into them.
20V is good for 100W of output. This is plenty, considering my input voltage is only 13.8V from my power supply, and the amp is rated at 14.4V which will increase these numbers.
This leads me to believe the amp will produce its rated power levels with no problem.
Next while keeping the amp bridged, I stressed it to get the fan to kick in. The fan on this amp does not run until a high enough temperature on the heatsink is reached, then it will slowly start spinning up. I found an issue with the fan on my amp. It made an awful noise when running, and I found it to be rubbing against the sheet metal bottom of the amp. After PG became aware of this they came up with a fan riser block idea within a day and were going to implement it into production. This makes PG very proactive in my opinion and I am quite impressed. I must say it is a pretty rewarding experience to find a flaw in a product and have the manufacturer actually jump on the issue and resolve it in so little time. This is just more evidence the "new PG" has high customer satisfaction as a target.
I have to mention another unique aspect of this amp. It draws almost zero current while idle. Most Class A/B amps have some idle current for biasing, and it can add up to a few amps. This amplifier has almost zero idle current and I am curious as to if it is Class B, not Class A/B. There are no bias controls, which I believe is more evidence of Class B operation. I have seen Class A/B amps with no bias controls which used other methods to keep their bias stable, but I really think this is just a Class B amp. Now, don't let Class B change your opinion of this amp for the worse. A well designed Class B amp with a high amount of feedback can overcome crossover distortion often associated with Class B designs. While power testing this amp, I observed the output on an oscilloscope while under load, and I never found any evidence of crossover distortion.
I am sure you are wondering about sound quality. After all this is a PG product, and SQ is paramount (well, it was until "The One" came along to beat down the door of the SPL universe as well...). I will not elaborate a whole lot on this, but I have listened to or owned nearly every PG amp made at one point or another, and this amp sounds just as good as any of them. What more can you ask for? With PG amps it is not so much about how or what they sound like, it is how or what they don't, as they don't color the music in any way I have ever detected, and for the S400.4 to make the grade, it too has to be just as transparent. And it is.
Suggestions for PG:
Please add stereo bridging, and consider dumping the high level inputs in favor of RCA padding and a 2-4 input switch. These changes would make things easier for those of us wanting to use this amp as a large 2-channel, which would complement the S1000.1 perfectly.
Second, as I stated in the S1000.1 review, this amp is begging for some endcaps. The look of the amp is nice being so small, and a pair of endcaps would complete the package in style.
Final Thoughts:
This is a great little amp which will fit a lot of people's needs well. It can fit just about anywhere due to is small size, and it provides far more power than just a head unit would provide. It is an excellent match for its big brother, the S1000.1 and together the pair of them would make a high power yet compact installation in nearly any car out there. With a MSRP of $399, you don't get a ton of power, but you get a lot of power in a lot less space then most others can provide. For many, this fact alone seals the deal.
As always, if you have any thoughts, complaints, or suggestions, please feel free to email dr.fosgate@gmail.com and I will take them into consideration.
EMD (2010)