Starke Sound Fiera4 4 Channel Amplifier Benchmark Test Results

The Starke Sound Fiera4 is a new amplifier and a follow-on to the now retired AD4.320 amplifier. The Fiera4 is a good amplifier for its price. While there is some higher value competition, the overall performance is exceptional, build quality is excellent, and sound quality is good enough for a high-performance home theater. Currently this amp is on a labor day sale for $1,299 which raises its value. Read on to see why.

While you may see me pick some nits here and there I did not find any of these issues to be particularly audible. I recommend you consider the Fiera4 if you are in the market for such an amplifier.

Feature Set:

The Fiera4 is a new take on an old amplifier that was called the AD4.320. The new amplifier appears to be part of an expanding commitment by Starke Sound to Class D amplifiers. Where the old amplifier relied on a heavy linear power supply, the new amplifier uses a switching power supply. One of the biggest advantages of switching power supplies is the ability to have a universal power supply that works in any country. These supplies allow manufacturers to reduce their sku’s to just one instead of two power supplies (which may actually entail several various parts and sku’s). I have long been a fan of good switching supplies because they also allow you to create a “stiffer” power supply that sags less with load (though one net effect of that is that it may create a hard knee or cut-off at which the amplifier power supply simply shuts down from over-current). Switching supplies also often have much lower noise than linear supplies, with the ripple being many times lower. This is an enormous advantage in ultra-low noise amplifiers. Other noted upgrades include:

• Upgraded NS600 amplification module with an extensively redesigned front end
• Improved chassis
• Improved internal shielding
•  Improved wiring paths

Besides the switching power supply and other upgrades, the Fiera4 contains two amplifier modules rated for around 130 watts RMS into eight ohms and 260 watts into four ohms across four channels (2-channels per module). While some may note that this is in the ballpark of a good receiver, I would suggest that few, if any, receivers can achieve those power levels for a sustained amount of time with all channels driven. The Fiera4 will do that power level all day long. A good reason to add any external amplifier, even if it is not substantially more powerful than what is in a receiver, is the ability to achieve those power levels with all channels being pushed. In addition, most receivers are power hungry Class AB affairs. While efforts have been made to improve efficiency, they still remain typically under 65% efficient at full load, and much less efficient at lower power levels. By comparison, Class D amplifiers routinely exceed 90% efficiency at maximum power.

Starke Sound noted that the Class D amplifier module is unique to them and that this allowed them to have the feature set they wanted. It is bridgeable (though the utility of that bridging function is limited, as we will note in the measurement section). Being friends with Bruno Putzey and having reviewed Hypex, Purifi, and Cherry Amplifiers in the past, I was used to that idea meaning a completely ground up from scratch amplifier. I had wondered if that is what Starke Sound did, as I found it surprising they would do that. It turns out I was correct to find that a strange idea. The amplifier is based around the Texas Instruments TPA3255 chipset. While the module itself is custom designed by the Starke Sound engineers for their purposes, using a pre-existing and particularly good chipset provides a much more reasonable means of obtaining superior performance in their product. Once recognizing that the amplifier is built around this TI chipset, its performance makes a lot more sense.

Fiera4 Back Panel

The amplifier contains both single ended and balanced inputs with a switch to choose between the two. Quality of the input jacks is excellent for this price point. The binding posts are a hallmark design of Starke, made of beryllium copper alloy, and again, are of excellent quality (I actually commented to Starke about how much I liked these binding posts). The amplifier is a standard three rack units tall or 5.5 inches, weighs a spritely 19lbs (which I love), and has an aluminum faceplate and backplate with steel chassis. While an aluminum chassis is a more luxurious option, it would have increased cost substantially, and at this price, steel is pretty common. Thermals seemed well controlled in the amplifier as I noticed no heat concerns while testing the amplifier.

Starke Fiera vs the Competition

As a note on price and value, I will start by saying that the price of the Fiera4 is $1499 for a 4-channel amplifier. A companion eight channel amplifier, which is nearly identical with the same amplifier modules, will be available soon at a price of $1999 and clearly represents the better value. My initial reaction is that this is not an exorbitantly expensive amplifier, but that there are other options that may be seen as a better value. For instance, Monoprice offers the ATI built Monolith M8125x (MSRP of $1999.99), which is an 8-channel amplifier rated at 8x100 into eight ohms and using the Hypex NC252MP module. The NCore modules have some performance advantages over the TI chipset used by Starke, but the Starke appears to produce a bit more power when all channels are driven. Noise and distortion are fairly similar between the two by rating. I have measured Ncore modules and found that they do not have the same rise in HF distortion seen in the TI chipsets, have much lower output impedance, and their response does not change with load by any appreciable level. Is any of this audible? I do not know, but these are the technical drawbacks of the Fiera4 compared with this Hypex amplifier. The Monolith amplifiers are an extremely excellent value, but the Fiera4 is a better built amplifier with a nicer chassis of better quality. It is bridgeable, two ohms stable, and so may be preferred by some who may need such functionality. Another high value option would be the Outlaw Audio Model 5000x, a 5-channel amplifier priced at $769 and rated at 5x120 into eight ohms. While this seems comparable, the 5000x has lower current capabilities and so its 4-ohm performance is not as good, only delivering 180 watts per channel, all channels driven. Further, the Outlaw does not have as good noise and distortion, though I would note, it is close. The Fiera4 outclasses the Class AB Outlaw in power, performance, and efficiency. The Outlaw is also not a differential amplifier, and its differential input is created using a THAT Corp chip, while there is no sonic problem with this, it means that the use of balanced cables would have little advantage outside of noise over long runs. In my assessment, while there are a few amplifiers on the market that offer similar features and performance at a similar to lower price, I still think the Starke4 represents a good enough value to recommend. Its performance is certainly not as good as Hypex or Purifi based amplifiers, but it costs less than most, and those that cost a similar amount do not perform massively better. The few problematic performance specs are all likely to be inaudible in practice. Ultimately, you need to decide for yourself if this amplifier represents an excellent value and is something you want to purchase.

Quick Assessment of Sound Quality

This is not a full review. I have not had a chance to thoroughly listen to the amplifier. I did all of my measurements first. A general rule is to never measure an amplifier or speaker before listening, since it may bias your views. While I understand that, it was simply not possible to do so in this case since I just recently moved and still don’t have all of my audio gear and rooms situated for critical listening. I connected the speaker to my Gedlee Abbey speakers. These speakers do not have great bass on their own, so I added a subwoofer temporarily to this setup and did some quick listening. I listened to a variety of music, shorted the amplifier input, and put my ear to the speaker (my speakers are VERY efficient at 95dB at 1w/1m), and drew some quick conclusions. First, as for noise, the amplifier is not as quiet as the Purifi amplifier that Bruno Putzey sent me, but that amplifier is a 2-channel model that would cost retail as much or more than the four channel Fiera4. It was as quiet or quieter than every other amplifier I had around. Since most speakers are not 95dB sensitive, I highly doubt this very minor hiss will be noticeable by anyone. I could not hear it at my listening position, and this was in my newly built sound mitigated theater. After confirming that the amplifier is as quiet as it is specified to be, I put on some music and found it drove these speakers with ease. Since they are an efficient speaker, I understand this is not difficult, but keep in mind the Geddes are still a big speaker capable of absorbing a lot of power. I have clipped high end receivers with them. In this scenario, I again clipped the Fiera4, but it was at painfully loud levels and with an aggressive amount of EQ to get more bass out of the speakers. Outside of that, I found the Fiera4 to behave well and play the Geddes speakers very loud. Switching to the better spec’d Purifi amplifier, it drove the speakers to the same loud levels and, frankly, sounded about the same. The Purifi amplifier is one of the best measuring amplifiers in existence. The Fiera4 is not, with a few problems, but I could not hear evidence of this. The tweeter in my speaker is eight ohms rated, and I had worried that the peak with an 8-ohm speaker would be clear. I did not find it to be audible, but admittedly, I cannot hear out to 20khz anymore, so I would not be shocked that any peaking around 20khz would be inaudible to me. It is also likely that the reactive load of a real speaker mitigated this peaking issue.

I used this amplifier to replace my Pioneer receiver powering my Definitive Technology DI6.5LCR in-wall speakers. There are five of these speakers in my family room as part of a 5.1.2 ATMOS system. I used three of the four channels to power my LCR speakers. I like to turn this system up, it’s a fun room to blast music and dance. I’ve noticed some compression and possible clipping in the past, at least when getting the volume up there. By adding the Starke, there was less compression, suggesting the receiver may have been part of the problem. While the Fiera4 doesn’t put out substantially more power than the Pioneer, the Fiera4 can take a huge load off the receiver and may provide over double the real-world power to each speaker. I haven’t had a lot of time to listen in this arrangement, but overall, I am impressed so far and plan to do the rest of my listening tests in this configuration. 

Measured Performance

Editorial Note on Testing: This amplifier was not measured on Gene’s Audio Precision, but on a Quantum Asylum QA401 with QA451 load box and external load resistors. This device can measure up to a 100dB SINAD value, so any produce with performance worse than that can be measured accurately on the QA product. I can add a QA480 oscillator and notch filter to further improve performance to better than 120dB SINAD but did not use this device for my measurements as the Fiera4 performance does not exceed 100dB SINAD. The QA451 load box includes an amplifier filter for measuring Class D amplifiers but has a knee around 65khz (-3dB). Since the amplifier had been tested by Soundstage and Secrets to Home Theater, I had a point of reference to ensure my own measurements were accurate. 

Fiera4 Gain Structure:

I measured gain as 21.4 dB with a balanced input and 27.4 dB with single-ended input. This gain was apparently chosen as a compromise between the 19-20dB of gain seen in professional amplifiers and the 26dB of gain seen in consumer gear. The advantages of a lower gain are not small, it does actually reduce the system noise by the same amount that gain has been lowered, so in this case, a system SINAD should now improve by 4.5 dB. It also becomes possible that consumer gear would struggle to drive this amplifier to maximum output. It took a 2.0-volt input to drive the amplifier to 108 watts output. As noted, the amplifier is capable of 130 watts. If your receiver cannot provide a clean 2.2+ volt output, you may not be able to drive this amplifier to clipping. In practice, we are talking about less than a 1dB difference in output.

Frequency Response

Fiera4 Frequency response at 8 and 4 ohms

First let me apologize for the scaling. It was not possible for me to rescale this around 0dB, given how I tested it. However, with a little mental math, you can see that we have a line that is hovering around 18.4dBV over most of the range. At 8 ohms, we see the frequency response increase around 10khz, hitting a peak at 35khz by +1.6dB. At 20khz, the rise is like half a dB or so. Just a note, the high-pass filter seen in my measurement is inherent in my measurement device. It is -1dB at something like 7-8hz, suggesting this amplifier is at least that good.

1 Watt FFT

Fiera4 1-watt FFT unweighted

As you can see from the 1-watt FFT, it shows little signs of power supply noise. There are some spurs evident at 180hz, 290hz, etc. THD+N is .00489% or around -86.2dB. The Signal-to-noise ratio at this level is 87.2dB unweighted. This would come to a signal-to-noise ratio, unweighted, of 109.1dB at 130 watts RMS. A-weighting brought this up to 111.4 dB at full power. This is really decent noise performance.

THD+N vs Output  

Fiera4 THD+N vs power sweep at 4, 8-ohm STD and Bridged

Looking at the THD+N sweeps, which show how THD+N changes with power level, we see the amplifier meets the power specs well. Note that the noise was elevated in this sweep below 10 watts because the Class D amplifier noise was preventing an automatic attenuator from engaging like it should have. You can see this in the 4-ohm measurement and bridged measurement at 4 ohms where it kicked in for a brief period and then kicked back off. This attenuation circuit allows for an accurate assessment of THD+N at low levels. This is a common issue with the Quantum Asylum and only affects measurements taken with the sweep. The main interpretation of this graph should really be to identify the point where clipping begins, shown as a knee in the response. The 8-ohm sweep shows a knee around 85 watts rms at .01% THD+N, it is around 158 watts RMS 8 ohms at 1% THD+N. This matches the spec of 130 watts RMS at .1% THD+N. At 4 ohms, we see the knee begin around 210 watts RMS at around .07% THD+N, and hits 250 watts RMS at 4 ohms at 1% THD+N.

I want to make a note on bridging. Here, the value of bridging is only in lower impedance loads. Into an 8-ohm load, this adds no meaningful boost in power and only adds noise. This is because the 8-ohm output is more voltage limited, not current limited. However, into four ohms we double the current and so now we see both a voltage and current limit issue, so the bridge feature seems to give about twenty-five watts more output. Still not meaningfully more, but into two ohms, which I did not test, we would likely see a more substantial increase in power. If you have speakers with a difficult load, it is possible that bridging channels is worth it. Otherwise, I do not recommend using that feature.

Starke Sound Fiera4 Power Measurement Table

Just a note on the self-explanatory power table. I have found that many Class D amplifiers do not show different results with the Dynamic power test compared to what is achieved using a power sweep. The power sweep may be short enough at each power level that is measured to effectively be the same as the dynamic test such that, given how Class D amplifiers behave, we do not see a difference. I have tried to evaluate this by lengthening and shortening how long the sweep goes for and doing a bench-top test, simply running the noise signal continuously. What I can say is that if I test for a fraction of a second at 157 watts or I simply let the noise generator run continuously, I get about the same 1% THD. I did not see power drop or distortion rise. I think the practical take-away is that Class D amplifiers like this do not have a lot of extra headroom and you need to ensure that 150 watts are more than enough to achieve the output levels you desire. It has nothing more to give. It is possible that a linear power supply might give more headroom, but there would be drawbacks in noise, ripple, stability, and the universal voltage ability.

THD vs Frequency

Fiera4 THD vs Frequency (note the inaccurate THDN label, ignore)

Because distortion is controlled by feedback in an error correction loop, the gain bandwidth product limits the range over which you can apply such correction. Modern Class D amplifiers are adding higher order feedback loops, but we see the best of these implementations more in amplifiers from Hypex and Purifi. As Bruno Putzey noted in a recent email exchange, we need to be careful how we use the feedback gain within the usable bandwidth. If we get 1dB of error correction at one frequency, we must have 1dB of error at another. Best to push that error up toward less or inaudible ranges. We also must remember that a harmonic at 10khz is 20khz, 30khz, 40khz, etc. Only one of those is audible and not very. By 20khz, we are talking about harmonics that are well outside the audible range. So, pushing the error outside the audible range makes sense, and it means we should look at how low distortion is within our more sensitive hearing range rather than worry too much about what is happening at or above 20khz. In my measurement, we see that distortion is around .001% between 100hz and 1khz, rising after that. By 5khz, we see that distortion has risen to .005% at 1 watt, but it is a higher .05% at 4 watts. By 20khz, we see distortion has risen dramatically to .1%. I only measured at 1, 2, and 4 watts to show how this rises with doubling in power. I cannot measure at higher power levels without triggering the attenuator, which would then cause noise of the QA401 to rise and make some aspects of this measurement inaccurate. Assuming this rise is linear until clipping, we can get a good sense of how distortion rises over frequency as power goes up. Now you are probably asking, is this satisfactory performance? It is ok, it is not terrible performance, but we know that better is possible. This behavior is consistent with the TI chipset that is being used and it is on par with what we would see from an Icepower or Pascal amplifier (at least in terms of shape, those offer lower absolute distortion levels). In fact, we have seen this same behavior on the best measuring Class D amplifiers, and while they may have lower absolute distortion levels, they still rise dramatically. Having picked this nit, it is unlikely this distortion is horrifically audible, or audible at all. This is a more academic problem than a meaningful sound quality issue. In fact, the engineer behind this amplifier, Dan Wiggins noted at the outset that his design choices were about ensuring an amplifier that sounds best in ways that matter for how it is used and listened to, not purely for academically perfect measurements. Mission accomplished. I would also wonder if the distortion of the speaker would still swamp the distortion of the amplifier here. While distortion rises to as high as .1%, we know a lot of tweeters would be at .5% THD or higher at those same frequencies. I was listening to these on a speaker that uses compression drivers which are known to have generally higher distortion than dome tweeters would have at these lower volume levels. A compression driver typically has around 1% THD at something like 90dB, but it will still be 1% at 100db or even 110dB. A dome tweeter might be as low as .1% THD at 90dB, but it would quickly rise by 100dB and could not even do 110dB. Which is all to say, as a reviewer and in trying to be fair and objective, I do not think this represents state of the art performance and I wish it performed better here. However, I also know why it performs like this and how many other amplifiers show comparable results. Being more realistic though, I also suspect this is not that audible. Those systems where this might be audible probably would also be more expensive and better suited to higher end amplifiers.

Concluding Thoughts

As noted, this is largely a quick take and measurement report. This amplifier has already been measured by others and my results substantially match the results they obtained. As such, I feel confident that my results are as accurate as can be expected. Overall, I find the measured performance to reflect a competent product capable of good sound. While there are better Class D amplifiers on the market, I find the Fiera4 to be a fair product with more than adequate performance. Many of the deficiencies in the amplifier are audibly minor and would not be noticed by the vast majority of buyers. The four-channel model under review represents a reasonable price for it is power level, channel count, and measured performance. However, the 8-channel model that is coming soon is a better value. For just $500 more, you get twice as many channels. In fact, for most home theater enthusiasts, the 8-channel model will be their first or primary purchase, as this will have sufficient amp channels to meet the requirements of most home theaters’ base layer. The four channel makes sense as a companion amplifier for higher channel count ATMOS, DTS-X, or Auro3D setups. In such a setup, I would use the four channels for the LCR speakers and the other amplifier for the surrounds, as it should provide slightly better performance. For those looking to upgrade the power from their receiver, it is likely that this four-channel amplifier would be a good upgrade. While it does not put out substantially more power than most good receivers (at least on paper), it is still a respectable amount of power and will produce that power with all channels driven. In addition, it will take a substantial load off of the receiver. This would be a great amplifier to add on to a receiver for more power or as part of the amplification with a pre-pro when lower power levels are needed. My listening tests so far have shown the amplifier to sound fine with no noticeable noise or audible distortion. While the amplifier has some peaking with an 8-ohm load, I did not notice any audible colorations when driving real speakers. I thought the amplifier sounded clean, dynamic, and provided a clear step up from the receiver it replaced. When compared to a much more expensive Purifi amplifier, I did not feel cheated. The Purifi is noiseless, distortionless, and colorless, a near perfect amplifier. However, going back and forth between it and the Fiera4, I just did not notice an enormous difference. I have connected this amplifier in place of a receiver that was powering my family room surround system and will continue listening and testing, providing a follow-up on my experience at a later date.

In the meantime, the Fierra4 is currently on sale for $1,299 and is worth a hard look for anyone wanting an efficient, good sounding, reasonably high power amplifier that will surely bring new life to your overworked AV Receiver.

Unless otherwise indicated, this is a preview article for the featured product. A formal review may or may not follow in the future.