ecp audio L-2 Parafeed Headphone Amplifier

Addendum, May 2015: Since writing this review in late 2013, I purchased two other headphone amps, both considerably more expensive than the L-2.  One of these amps is the Apex Teton.  It deserves 5 stars for sound quality, as it is hands down the best amp I have ever heard.  The other amp is the Eddie Current 445, which deserves 4.5 stars.  Both the Teton and the 445 are better sounding amps than the ECP Audio L-2.  The transitive property means the L-2 deserves less than 5 stars, my original rating.  4 stars seems about right to me.  The L-2 is a great sounding amp that beats a lot of the competition, it is a bargain if found used, and I think it is worth its original sales price.  But, yes, $5,000 amps sound better than the L-2.          
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I have owned the ECP Audio L-2 for about 2 months now.  I also own an Eddie Current Super 7 with NOS tubes, including Tung Sol BGRP driver tube.  I have previously owned the Woo WA22, the Luxman P-1u, the DNA Sonett, and the Singlepower Extreme Platinum.
 
I can honestly say that of all the amps I have owned, I only really liked three right out of the box: the Super 7, the Singlepower Extreme, and the ECP L-2.  That already puts the L-2 in rarified company, since my first impressions ended up being lasting ones and led me to eventually sell the WA22, the Luxman P-1u, and the DNA Sonett after trying but failing to like them.
 
The Singlepower Extreme will always be close to my heart for its warm sound signature.  But it had horrible build quality and ultimately failed.  The ECP L-2 has stellar build quality in comparison.
 
So, what do I like about the L-2?  Here my short list of two prized attributes:
 
(1) It has all the positive musical attributes of a good tube amp -- it is slightly warm and full-sounding, not at all dry or boring.  Although Doug Savitsky of ECP Audio is a no-nonsense builder, this amp is not a "straight wire with gain".  It is really immersive and musical. I also don't find it to be at all bright, as Skylab found. I am sensitive to bright, fatiguing sound.  I only could only listen to Grados for about 15 minutes before I needed to take some Advil and return them.  The L-2 is good for hours of fatigue-free listening.  The amount of mid-range and treble detail this amp offers is also really impressive.
 
(2) It has none of the negative attributes of tubes -- it is extremely quiet and barely gets warm.  I really like using my JH16s with full-size headphone amps.  The JH16s offer sound quality that rivals the best dynamic open headphones I have owned or demo'd, but they also isolate really well.  The one drawback of IEM's is that they are highly sensitive with very low impedance.  If there is any noise in the circuit or from the tubes, you will hear it with the JH16s.  When I use the JH16s with the L-2, I hear absolutely zero noise.  This amp is as quiet as the solid state Luxman P-1u.  Also, unlike some tube amps, the L-2 is not a space heater.  You won't risk burning your children or pet with this amp.
 
Comparing the L-2 to the Super 7: the Super 7 is a great amp, but in my book it gets edged out by the L-2 in every respect except one.  The L-2 is quieter and offers slightly better resolution and detail than the Super 7.  The Super 7 sounds a tiny bit rolled off in comparison to the L-2.  The L-2 also seems to drive my LCD-2s better than the Super 7 does -- offering better dynamics than the Super 7.  The L-2 also has significantly lower gain than the Super 7, allowing me to use much more of the volume pot than the Super 7 does (a particularly nice feature with the JH16s).  The only aspect of the Super 7 that beats out the L-2 is in the area of bass quantity and depth.  Simply put, the Super 7 has really authoritative bass, easily the best of any amp I have owned.  Bass-shy CDs tend to sound better through the Super 7 than on the L-2.  Overall, I am finding that I am listening to the L-2 about 80% of the time, switching back to the Super 7 20% of the time.
 
Yes, the L-2 is an expensive amp.  But so are the WA22 and the Luxman P-1u, neither of which compete with the L-2.  The Super 7 is a cheaper amp, although when you figure in the cost of finding NOS tubes for it, the spread between the cost of the two amps falls quite a bit.  Although I have no intention of parting with either amp, if forced to I would sell the Super 7 before the L-2.
 
Summing up: it's a shame that ECP Audio is somewhat overlooked as an amp manufacturer on Head-Fi.  My guess is that this is a result of ECP Audio's (i.e. Doug Savitsky's) approach to marketing, which is to completely avoid it as far as I can tell.  He does not frequent this forum very much, let alone attend a lot of meets.  As a result, there is not a lot of buzz around his amps.  I have owned a lot of high profile amps in the last 7 years and the L-2, in my opinion, easily competes or beats all of them in terms of sound and build quality.

Intro and Background
 
[size=11.0pt]Doug Savitsky, founder of ECP[/size] Audio, was nice enough to come over to my house and deliver a loaner unit of his L-2 tube amplifier.  Doug also lives in the Chicago area, so this was much safer and easier than having him ship it.  And it was fun for me - Doug is a very smart guy, and i enjoyed hearing about his amplifiers from him.  He told me a lot about the L-2.  He also told me he thinks his solid state amp, the DSHA-1, is the better sounding amp. Oh well.  I'm a tube guy, mostly, and I wanted to audition the L-2.

Doug's amps are very well made, and very nice to look at:
 






 
The topology here is quite interesting.  I was kind of surprised, and initially a bit put off, that it used balanced inputs, since it is a single ended amplifier.  But there is a very good reason for that, which is that the L-2 uses an input transformer, according to Doug: “The balanced connectors take advantage of the input transformer. With XLRs, the input signal is not connected to ground which helps eliminate noise.” Fair enough.

Further, the L-2 uses a “Parallel Feed” topology.  I was not familiar with this, so I asked Doug about it, and he said:
 
Quote:

In traditional transformer coupled tube amps (often referred to as "series feed"), such as the Trafomatic, Balancing Act, or Donald North's stuff, the transformer is in series with the DC (direct current) feeding the tube. This means that the DC flows through the transformer. DC saturates transformers cores (making them unable to pass a signal) so in order to accommodate this, the transformers must be altered. Specifically, they need to have an air gap in them, they need to be larger, and they need to be made from a material that does not saturate easily (M6 steel). All of these things lower the fidelity of the transformer.

Parallel feed (parafeed for short) changes this topology a bit. Instead of running the DC through the transformer, you instead use a different load for the tube (a choke, a resistor, or a constant current source (CCS)) and capacitor couple the transformer to the circuit. This allows transformer that are not air gapped, are made from better core material (nickel in the case of the L-2) and that are smaller, all of which increase fidelity.  Neither parafeed nor single feed are necessarily "better," but there are times when one option is a better choice. The reason to use single feed is that a transformer is an energy storage device. This means that a transformer loaded tube (single feed) can swing higher than B+ in voltage. So, for a power amp, this makes sense. For instance, a 300B based power amp with a 300V power supply can swing several hundred volts below and above that 300V supply. To do this with a CCS loaded parafeed might require a 500V supply which would mean an extra 30W of heat to dissipate making an already inefficient amplifier much more so. (a choke loaded parafeed can do the same thing as a single feed amp, and in that case, it is just a preference of one topology over the other -- Bottlehead amps are generally parafeed done this way.)

The tradeoff to the above is lower fidelity. That is, the gapped transformer that can swing the volts much be large, gapped, and steel. In headphones, where we only need a quarter watt, this efficiency need drops away. The L-2 wastes less than a watt across the CCSes loading the tube, which seemed OK. And, the advantage is the ability to use a better transformer.

Two more notes -- one oft mentioned con to parafeed is that the transformer is capacitor coupled to the circuit, that cap being in the signal path. This can be an issue in that this can form a resonance circuit (typically resulting in a bass hump) but sizing the cap appropriately eliminates this. Moreover, the parafeed cap as it is called is typically ~5uF in size (small enough to allow the use of a high quality cap -- I use V-Caps) where as with single feed, the final power supply cap is in the signal path, and this is generally a large electrolytic. So, this is really not a downside.

Second, and this is the real advantage of parafeed, as the name suggests, AC and DC current paths are in parallel, rather than overlapping. This means that the AC signal current loop is well controlled in parafeed, travels through less components which tend to be of higher quality, and does not interface with the power supply.

Click to expand...

 
 
There is even more information on this here, for those interested.  http://ecpaudio.com/pdf/parafeed_basics.pdf
 
[size=11.0pt]I present the above information purely as background and FYI.  I’m not taking on faith that any of that really makes the amp sound better.  It’s well reasoned, of course, as Doug knows what he is talking about from a technical perspective, but every amp maker has their own biases.  What matters to me is how it SOUNDS.

I auditioned the L-2 using a variety of my sources, analog and digital.  I ended up using mostly the Ultrasone Edition 8 and Audio Technica W3000ANV, mostly because  the L-2 only outputs about 250 mw, and my other two headphones are the Audeze LCD-3 and Hifiman HE-6, which require more power than that in my opinion.[/size]
 
Sound Thinking

The ECP L-2 is definitely not what people probably imagine tube sound is going to be if they have not heard a lot of tube amps.  It has a very smooth sound, yes, but it's also very neutral and detailed, and not in any way overly warm, lush, ripe, or plump.  In fact, it is much less of all of those things than many tube headphone amps I have heard.  It is much closer totally to my RedWine Audio amp, for example, than it is to my Leben or Decware.  It's quite far from the very lush Decware. 

None of that is meant to be any sort of indictment of the L-2, though.  It has a very enthralling sound that is very nuanced.  Detail retrieval is absolutely first rate, but not due to some shoved forward treble abnormality.  No, it's real detail that comes from suberb transparency, and from a crystal-clean presentation.  As always, this usually works well, but if you are playing a hard, bright sounding recording, guess what? You will get sound that is hard and bright.  There isn't a lot of editorializing going on here.  Play crap, and you will get crap.  Play something well recorded, even reasonably so, and you will get very, very good sound.

I'm not talking here about only being able to enjoy "audiophile approved" recordings.  Yuck.  I was captivated playing "And You And I" from Yes's "Close To The Edge".  I have played that song hundreds of times.  But I actually stopped what I was doing when it came on, shut my eyes, and got lost in it. 

Part of that was definitely a function of the remarkable soundstaging ability this amp has.  The stage is not projected all that far out in front of your head, and yet it has an impressive depth and width to it.  Image specificity was also first rate.  Very nice.

Comparatively Speaking

So an obvious comparison would be with the Trafomatic Experience Head One, which uses the same output tubes.  It's about 2/3 the price, and while also output transformer coupled, with a switchable impedance capability, it is a different topology.  Unfortunately, I no longer had the Trafomatic, so I am going just from memory, but I do think there were some similarities, with the ECP getting the edge in terms of nuance and soundstaging.  I was always very impressed with the Trafomatic, though, and I don't think it is very far behind the ECP.

Slightly more expensive is the Leben CS300, which is my "reference".  The Leben of course is also a speaker amp, and has multiple inputs, a bass control, balance control.  On the other hand, it's transformer coupled with only one winding (32 ohm) for headphones, and doesn't like high impedance cans that much.  It has a lot more output power, though, amd as such, for the LCD-3, ot was a much better choice than the ECP.  And the CS300 also has a more organic, and slightly lusher sound to it.  With the W3000ANV, though, I do think the ECP slightly bests the Leben in terms  of detail retrieval, which is saying a lot, as I think the Leben is excellent in that regard.  The same story for soundstaging - the ECP is just a wee bit ahead.  I slightly prefer the Leben's tonal balance, and its lusher midrange, but for many people, I imagine it will be the reverse. If I had to choose one amp for the W3000ANV, it would be the L-2.
 
And the same for the Edition 8.  The Ed 8 is very efficient, and while I like it a considerable amount with the Leben, I slightly prefered it with the L-2.  The Ed 8 lapped up the L-2's delicacy, and sounded more nuanced than I ever recall hearing it.  That was fun.
 
 
Other musings

Any nits to pick? Well, as I mentioned, the amp does ride the line toward being bright.  It is important to note that the L-2 is NOT bright, and I found it's neutral voice quite alluring.  But it is not lush or warm, and so as always, one should careful what headphones one pairs it with.

Ergonomically, I also have to say I really dislike external power supplies connected with super thick cables that are hard to connect.  That's what you get here.  Worse, the umbilical is on one side, and the power cord the other.  Yuck.  It means there is no good way to place or display the PS, which completely negates the nice looking chassis the PS is in.  I much prefer onboard power supplies.  I'm sure there is a good technical reason for having an external PS, such as a lower noise floor, less hum (and there was blissfully no hum or noise I could hear even with very efficient headphones).  But that said, I still had a very hard time trying to decide where to put what is a fairly compact amplifier because of the PS.

And then, there is the price.  The fact of the matter is this is a terrific sounding amp with the right headphones, but only fairly efficient headphones need apply, given the somewhat limited power output available (averaging 250 mW).  You can use both high and low impedance headphones, which is great - assuming a reasonable sensitivity.  $2,500 is a LOT of money for a headphone amp.  I know that the cost of goods of the L-2 is very high, and when you see it, you understand why.  The price seems justified in terms of the cost to make the product – but that doesn’t increase the number of people who will buy a $2,500 headphone amp that requires fairly efficient headphones.
 
Final Thoughts

But I understand that there are trade offs. And the fact is that I was VERY tempted to buy one just for my W3000ANV, but I cannot justify the expense.  Pity...I will hate to see it go.  For those who have the money, and want a compact, nice looking, well made headphone amp to use with high end, high-sensitivity headphones, the L-2 would be a very good choice.