Affordable stereo integrated amplifiers are by no means common. When it comes to models aimed at audiophiles, there are even fewer. So, let’s look at one of those few: the Burson Audio Funk amplifier. As you will have noticed from the heading above, Burson Audio terms the Funk a “Headphone & Speaker Amplifier”. That could be just a fancy way of saying a traditional stereo integrated amplifier. But I think it’s Burson Audio’s way of saying that the Funk is an amplifier equally competent when it comes to driving loudspeakers and headphones.
And since the headphone output in many stereo amplifiers is clearly an afterthought, that’s an interesting focus.
- The Burson Audio Funk is an integrated stereo amplifier with both speaker and headphone outputs
- Purely analogue
- Class A/B for loudspeakers: 45 watts into 4 ohms, 35 watts into 8 ohms,
- Class A for headphones: 3.5 watts into 16 ohms, 2.5 watts into 32 ohms, 600mW into 100 ohms, 400mW into 150 ohms, 150mW into 300 ohms
- 1 x stereo RCA analogue input, 1 x 3.5mm mic input bypass
- High quality binding posts for loudspeakers at back
- 35mm headphone output at front, 3.5mm headphone/microphone connection at front
- Manual headphone/loudspeaker output switch
- Headphone low and high gain control
- Analogue volume control
- Upgradeable op-amps
- Optional stand for vertical use
- 150mm wide by 57mm tall by 236mm deep (including controls and connections)
- 1.27kg (not counting external 24-volt power supply)
- The Burson Audio Funk integrated amplifier is cleverly thought out and is a good match for quality loudspeakers … so long as you’re not trying to fill a giant room. The headphone section is genuinely audiophile quality. The only real downside is … only one input? That’s inconvenient.
- Price: $999
- Available at fine high fidelity retail outlets, and direct from distributor's retail division here.
More about the Burson Audio Funk
This is a very compact Class A/B stereo integrated amplifier. The sides, bottom and top of the machined aluminium case are fluted, forming a heatsink for the unit. (Inside you can see that the power transistors are bonded to the bottom of the case.) The heatsink treatment is required for the headphone amplifier – being Class A and rated at up to 3.5 watts, it generates a lot of heat even when idle – and for the 35/45 watt Class A/B “Speaker Amplifier” section.
Unlike most loudspeaker amps with a headphone socket, plugging in a headphone does not switch off the speakers. There’s a button on the front panel to switch between the two modes. That makes a lot of sense since, I expect, putting it into speaker mode entirely switches off the headphone section, removing the heat-reduction burden of that. And likewise, in headphone mode the main amp goes off to allow the full use of the heatsink to the headphone amplifier.
And I shall have to stop using words like “main” to describe the speaker amplifier. As we’ll see, the headphone amp is its own thing, a high-performance unit that should not be consigned to second-class status.
Also on the front panel is a button for power or standby, a button to select between the two gain levels for the headphone output, a volume control knob connected to a good old-fashioned analogue potentiometer. That turned out to be an ALPS 8206. The two front-panel connections are the 6.35mm and 3.5mm headphone sockets.
I shall confess to some ignorance here. At the back is a 3.5mm socket for a microphone. At the front, the 3.5mm headphone output is a TRRS type with support for microphone. I image these have something to do with gaming headsets, but lacking a gaming headset, and having not suitable microphones (mine are all either USB or XLR) I couldn’t really explore this. The manual assumes knowledge as to the use of these.
The one significant weakness of the Burson Audio Funk amplifier is fact that it has just one set of inputs. For my final listening, I largely got around this by using as a source, or kind-of source, the delightful Moon 280D stream DAC. I had several digital audio devices plugged into this so I could choose between them or the 280D’s own network audio functions. But earlier in the piece when I was using the Funk with two different DACs plugged into two different computers, I used a cheap plastic Jaycar audio switch to select which computer to listen to.
A word on power
The Funk is powered by an outboard 24-volt switching power supply. Burson Audio says that the Funk uses its “Maximum Current Power Supply”. If I’m understanding its argument properly, it seems to be saying that this switching power supply – it upsamples the power to a 170kHz square wave before conversion – is actually better than a linear power supply. That’s principally because, says Funk Audio, the output resistance of the power supply is at least an order of magnitude lower than that from a traditional supply, allowing it to supply current more responsively.
As is often the case with technical claims of this nature, I’m not quite sure what to make of it. But the general consensus of the high fidelity community would probably be that well-designed linear power supplies are best. That said, I applaud Burson Audio for mounting a novel argument to say that a switching power supply is not just as good, but better!
Me? I just go on what performance things deliver in the real world. So, let’s see what it actually delivered.
Listening using the Burson Audio Funk
I gave the Burson Audio Funk three separate tasks. The first was to operate as my main headphone amplifier for a couple weeks. The second was to drive my desktop speakers – that is, the pair of speakers connected to my computers – for a couple of weeks. And the third was, for a brief time, to drive my main listening loudspeakers.
When it came to headphones, the results were simply superb. I used the Funk with a bunch of them, but primarily with the exceptionally revealing Final Audio D8000 headphones. I have not heard better from any headphone amplifier, regardless of price. There was no background noise. Amplifier control over the headphones was excellent. Volume was unlimited. That was also the case for my old, less than sensitive Sennheiser HD 535 headphones.
On my desktop, the second task was to drive my “computer speakers”. They are a pair of KEF LS50 speakers on IsoAcoustics stands, propped up a little further at the front to ensure that my ears are on-axis. These are high quality, exceptionally revealing speakers, lacking only in really effective bass. Normally I run them with a subwoofer to look after the bottom couple of octaves, but the Burson Audio Funk lacks a subwoofer output, so I just ran them alone.
And the results were excellent as well, apart from the relative lack of bass. Those revealing KEF loudspeakers revealed a lovely performance. Again, there was power to spare with these. But they are actually a fairly easy load to an amplifier.
And, so, to task 3: driving my main listening loudspeakers. This was an unkind task to assign to an amplifier such as this. Those loudspeakers are the Dynaudio Contour 20i speakers (which I reviewed here). They are stand mount models, but reach solidly into respectably deep bass. And with a nominal impedance of 4 ohms and a sensitivity of just 86dB for 2.83 volts input, you’d expect them to need a hefty beast of an amplifier to make them sing. Normally I use the Schiit Audio Vidar power amplifier, which is rated at 200 watts into 4 ohms (confirmed: I’ve measured it at better than 210 watts, both channels driven).
So I kept things reasonable in terms of volume level, but didn’t shy away from seeking to fill my listening room. Which the Burson Audio Funk/Dynaudio Contour 20i combo managed comfortably. And sweetly in the case of Anette Ashvik’s vocals on the album Liberty. The layering of sound on such tracks as “Under the Tallest Tree” was immaculate, with the slightly distant skins delivered with a gorgeously resonant bass.
Hector Berlioz’s Le Francs-Juges Overture is a dramatic piece employing a full symphony orchestra with heavy use of the brass section. I enjoy the Telarc version, featuring David Zinman conducting the Baltimore Symphony Orchestra. Being Telarc, the bass drum is properly captured. I had to rotate the volume control a long way in the clockwise direction because of the fairly low level of the recording. Thus played back, the amplifier kept excellent control of proceedings, providing a wide and fairly deep sound stage. The powerful, deep brass sections ground out with authority. Just before eight minutes, the bass drum provides a lovely rumbling underpinning proceedings. That was deep stuff, yet controlled, with the resonances within the recording venue contributing as much as the drums themselves.
With Ry Cooder’s album Jazz, and the track “Nobody” in particular, at reasonable listening volumes I’d defy anyone to, blinded, tell the performance apart from that of an amp costing ten times as much.
Let’s start with the headphone output. Burson Audio says that it’s good for 3.5 watts into 16-ohm loads. Now, that’s a lot of power. Could it deliver this?
Hell yes. I only test at two impedance loads: 16 ohms and 300 ohms. Into the latter, the Burson Audio Funk delivered “only” 865mW or more at my three test frequencies (it only claims 150mW for that impedance). With all three, that was enough to produce 29dB above the sensitivity rating of any set of headphones. Even high impedance, low sensitivity headphones are going to have more than enough power to work with. With low impedance headphones, I’d suggest that you exercise caution. Into a 16-ohm load, this unit delivered 5.4 watts (compared to the claimed 3.5 watts), or 37dB above the usual sensitivity rating (ie. the output at 1mW input). Have it up too high, and that’s serious hearing damage.
I’m not sure that this in keeping with the times, but I like the fact that this amplifier exceeds safe limits. Yes, you the user should be cautious. But regardless of how weird a set of headphones might be, it’s highly likely that the Burson Audio Funk will support it and deliver what they need.
Oh, also, my measurements revealed that the output impedance of the headphone amplifier was just 1.2 ohms, significant below the upper limit of 2 ohms specified by Burson Audio. No, that’s not the lowest I’ve seen, but it’s certainly low enough that any variation in impedance by frequency of any headphone will be quite irrelevant as to sound quality with this unit.
I measured the frequency response of the headphone output as well. This was kind of interesting. Here’s the graph:
There was a slight roll-off starting at 10kHz, to be down by around 3dB at 30kHz. The average of the two channels had them down by 1.5dB at 20kHz. My hat is off to you if you can hear that. The reason I say it’s interesting is that if you look at the curve as it proceeds into ultrasonic frequencies, it stops curving and becomes a straight line. It looks to me like an intentional 12dB/octave low pass filter with a -3dB point at 30kHz.
Sorry about the nerdy stuff. Impact on sound when considered as a variation from a purely flat response? Nil. Impact on sound when considered as Burson Audio addressing some issue resulting from an unlimited top end? No idea, but it makes sense.
Finally, let’s look at the power output for loudspeakers. Burson Audio claims 45 watts into 4 ohms and 35 watts into 8 ohms.
For 100, 1000 and 10,000 hertz signals, the Burson Audio Funk delivered 25, 26.6 and 30.2 watts respectively into my eight ohm resistive test load. Into a 4-ohm load I measured nearly 48 watts output at 1kHz, and a bit over 50 watts at 10kHz.
I normally test with 100 hertz as well, but when I switched from 1kHz to 100Hz, I briefly noticed a heavily clipped waveform on the oscilloscope. And then the amp stopped working. I pulled the power and let the unit cool down for a while, then plugged it back in, but it remained dead. The online manual didn’t help because it doesn’t talk about any inbuilt protections. Eventually I removed the lid and found a component labelled “fuse” on the printed circuit board. This was a tiny fuse for a surface-mount fuse-holder. Fortunately, a spare had been included with the unit. I went to Jaycar Electronics to grab some more, but it turned out that these were rare enough for Jaycar not the carry them.
I had a lot more to do with the Funk at that point, so I discontinued power output testing lest I render it unusable by blowing the spare fuse.
One note on those power outputs: an amplifier almost doubling its 8-ohm power when driving 4-ohm loads is a rare capability. Maybe there is something in that Maximum Current Power Supply.
Look, if you have a giant room that you’re hoping to fill with masses of doof doof, I’d suggest that the Burson Audio Funk might not be quite the amplifier for you. But it you’re keen on quality sound at good levels in a moderately-sized room with quality stereo loudspeakers, then I’d strongly suggest that you find a retailer stocking the Burson Audio Funk, have a listen and I think you also will be impressed.