KECES HA-171 vs. M^3

Hello,

I have the HA-171 and am also curious how it would compare to the M^3 (or a Millett Hybrid Maxed or MiniMaxed).

This is my first headphone amp and I find it yo be a very well made product with a nice, mostly neutral sound. Besides a slight volume imbalance at the lower range of the volume knob (correctable through internal calibration), I think it is a nice product. It seems to handle both my Senns and Grados equally well (yes, I know, polar opposites).

As for the sound, it comes across to me as pretty neutral (perhaps a sliver on the side of warm) and is very much source dependent. If anything, I think it could be a little smoother on the high end, but, that might be my sources. The bass seems full and controlled as does the midrange. I am wondering if the M^3 (or milletts) would bring anything more to the table.

Keep in mind, I am VERY new to this hobby and have not heard much less compared a whole lot of headphone amps, so, take what I say with a grain of salt. This one looked to be a good value; well made and offering selectable inputs and bypass outputs. A lot for the money.

I can see this whole amp/dac chase is about to explode on me if I am not careful!! ;-)

jk

I know M^3 sounds great and a great design... HA-171 doesn't look very impressive, I'm guessing 2-channel Meta42 style (opamp+BUF634)

I had the Keces DA152 which is basically a DA151 and HA171 combined. I would rate them roughly at the Audiotailor Jade's level. I feel they compete well at the sub $400 level. However, this is only based on my memory as I never had them side by side.

M^3 is the far superior topology by a fair margin, it like comparing apples to oranges (forget about price as a determining factor in this case WRT the M^3).

I would take other cheaper amps ahead of the Keces...but that is just MO.

Peete.

I JUST remember that I had the LD MKIII side by side with the Keces DA152 and I definitely preferred the Keces.

I'll quote myself here: "Quick note on the Keces, I found it to be superior to the Little Dot MKIII with Russian 6Zh1P-EV driver tubes in almost every aspect save for the slightly more spherical soundstage, smoother and warmer midrange of the Little Dot. Two most notable superiority of the Keces are the extension on both ends while giving quite a bit more impact on every note."

I don't intend on slamming anyone's product, but I'd advice checking out specs of both HA-171 and M3 as a partial indicator of each product's performance capability.

You can find HA-171's specs and RMAA results here:
KECES HA-171 Headphone Amp, ready to ship now! (New internal photo added)
Test done with EMU1212M's digital output to DA-131.1 then on to HA-171 and back to EMU1212M

Topology wise, both is actually quite similar in the way that it's a simple Op-Amp driving a current buffer. With one buffer being IR's MOSFET while the other being National Semi's LME49600. The one major difference would be the way that ground is treated, on M3 it uses virtual ground with an additional ground channel while on HA-171 use the traditional split rail power and true electrical ground as the ground for headphone ground.

Which ground is better? Well, it depends on who you ask, but I personally prefer a true ground that is able to sink/source a lot of current. For active ground type of topology, I personally prefer one per channel instead of a shared ground channel, but then again, that would be a rather expensive setup that cannot be used on most headphones except K1000 and ones with independent ground for each channel.

That's a quite different design.

The M3 uses a pair of MOSFETs to create a push-pull output stage, that HA171 uses a monolithic buffer. It's also a LOT easier/cheaper to use a 2-channel design with a passive ground (ground signal goes to PSU). The M3 uses an actively driven ground channel.

You are correct in that there are two camps - 3-channel vs 2-channel. My only argument against the 2-channel design is that the sound REALLY depends on the PSU quality while a 3-channel does not depend on it as much.

It's not really fair to say that they are the "same price" - the M3 is a DIY design that (depending on PSU) can cost in parts almost as much as the retail value of the HA-171. Obviously Keces isn't building it for free, it's a business.

Well, if I may peel open the LME49600 buffer, it does have a push-pull stage at the output IIRC. If we compare them in a block diagram sorta way, the two will have a fair bit of similarity. (well, most amps on the market are like that anyways... :P)

Since the transformer, power supply circuits, regulator circuits and the whole works are in our control. We basically implemented a very low noise split rail power that works very well with our DACs and headphone amps. The difference between DAC's power and headphone amp's power is the size of the regulator's transistor. DA-152/HA-171 use higher powered TO-220 Toshiba transistor while the DACs use a medium power transistor that I can't recall the model number at the moment. As a personal preference, I prefer to use a big burly power supply when I have the room that is available on most desktop amps.

I personally have nothing against virtual ground, but I feel it is better suited to portable application when it is not feasible to build a power supply with a ground that can sink and source like ones on desktop units.

Some may say that virtual ground will almost always guarantee near-perfect split of the rail voltage, yes that is true. However, what is the point of absolute perfect split when a manually adjusted rail comes within 0.1V difference? The difference in the rail does not produce any output bias on a properly functioning amp, and does not really do much other than having one side of the output transistor/mos to dissipate more heat/power due to the voltage drop. But that point is also irrelevant if the rail difference is very small and the two side of the output device is in the same package (as is the case with LME49600).


As for M3's power, I'd say it IS really dependent on the power, I've actually built two M3s myself. One planned with moderate parts cost and high input capacitor value (I think in the order or 20000uF, but that was a while back) and powered by a traditional transformer power supply. I initially plan to use a run of the mill switching power, but the noise and interference generated by the power just wreck the sound of the unit, and introducing a LOT of noises into the system (Yes, I did try all kind of filtering techniques, none came even close to acceptable). Being unemployed at the time, I need to sell some toys for cash, so I basically drop the switching power and use a traditional transformer power supply.

The second one was built with higher priced parts and lower input cap size (BC 118 AHT, total 6600uF I think), this time I paid about 10 times the price for a supposed high quality switching power (well, I got a job when I was building the second one). Lo and behold, it was one of the cleanest sounding headphone amp/M3 that I've heard up til then.

How does those two M3 compare to HA-171??? Well, I have NO IDEA Since both units are long sold to my friends before HA-171 was ever materialized.

I also have built two Mini3s, with identical parts except the op-amps... Interestingly I find the lower power/lower performance National Semi op-amp version to sound better than the supposingly high performance AD op-amp version... Anyone felt the same about the Mini3?

Has anyone else heard the HA-171 to be able to comment on it's sound relative to other products?

So, how does the HA-171 measure in RMAA with a 330 Ohm load, with 38 Ohm load and with 8 Ohm load? (as in M^3's amb site)

 

And how about those measurements Maniac regarding the HA-006+?

Forget the HA-171. It looks like a pretty low-end amp compared to the M^3. I had the Sheer Audio HA-006++ and while it was pretty good for the price, it fell well short of the M^3 I had.

Out of interest, is there anything that's really usurped the M^3 in value at the $300-500 range in the last few years? 

 

Preferably the low end that is.

 

Unfortunately they seem much harder to find and more expensive to build than they used to be.

At the moment, we are working to procure a new set of EMU 1212M for testing purposes, as the previous setup is no longer available to us at the moment.

 

This setup will be integrated into my Thinkpad's "Advanced Dock" (I guess when the dock weights more than most notebooks, it could be called "advanced") and hopefully have a lower noise environment than most desktop computers.

 

 

I'll update the info as soon as I can get the test setup.

Might want to note that the M^3 does have some dependency on quality of power supply, don't expect to throw in a cheap switching supply and expect it to work wonders.

Edited by FallenAngel - 8/9/10 at 9:20pm