"If it measures good and sounds bad, it is bad.
If it sounds good and measures bad, you've measured the wrong thing."


3 Tweaks for Cheap!

Posted by kboe on September 20, 2011 at 1:15 AM

October 2011

Tweaks for the HiFiMan EF-5 Hybrid Headphone Amp

Reviewer: Kevin Pope

Transport: 160GB iPod Classic loaded with AIFF

Source: Pure i20

Amp: HiFiMan EF-5

Headphones: AKG K-702

Cables: Power - Bob Prangnell Power cable and Verumecce Interconnects

Rack: DIY rack with solid Maple hardwood shelfs, wood button isolation feet

Power Conditioning: Wall Direct

Review Component Retail: OPA627 opamps/adapter combo - $30.00, EAT Tube Damper - $40.00, Furutech fuse - $48.00. 

I purchased a "Demo Unit" HiFiMan EF-5 hybrid as my new main rigs amp of choice.  It's outputting some serious wattage into my hard as guano to drive Cardas recabled AKG K702s.  Inspired to go Hybrid from past memories of my experience with a Millet Max and some polite prodding from Stuart Crawford of Deep Sounds, this units discounted price from AudioAdvisor caught my eye.  This being Tweak-Fi, what else is one to do with a new amp other than tweak the flying pig snot out of it.  But rather than review a new amp, and then three tweaks, making what would then amount to four combined reviews, I decided to do something different.  I'll only give brief impressions of the new amp, just for reference, and then I'll do the review process in reverse. Starting out with a fully tweaked amp I'll remove one tweak at the time describing it's sonic merit/detriment.  This avoids having to write the initial review and then waiting through three burn in periods for each of the three tweaks.  More to follow in October when I'll for sure know the sonic lay of the land for the new amp and be comfortable writing about this semi colossal task.

I’ve decided to do something different, keep things short! So you wont need a coffee break, am I nice or what!


I’ve only heard two hybrids before, both Millet’s, and loved them both. There is an organic quality to the presentation that is fatigue free. This attribute asserts itself again with the EF5. While it’s looks might not be for everyone, I’d find it hard to believe anyone could listen and not find something they like. Treble extension, bass impact and depth, midrange clarity and bloom, it’s all there. For those of us who like the detail wrought by transistors, there is plenty of that to go around. Fo the tube minded, there is enough, just enough warmth and sweet decay to remind one that there is indeed a tube in the circuit. My biggest fear was that the tube portion of the amp would dominate the soundscape. It does not, but then again neither does the transistor stage. While I have not had a bad experience with a hybrid design, some have, the EF-5 is not a bad experience by any means. For the asking price of $400.00, the EF-5 represents a true value in my mind. A separate power supply is a true audiophile minded implementation. The umbilical is just long enough to put it on the next lower or higher shelf of most equipment racks, which is a good thing because that leads me to my only nit to pick. The power supply has a noticeable mechanical hum which is clearly heard with open headphones and softer music or lower listening levels. More on the solution to that at the end of the review.

OPA627 Mod.

Stocked with the OP275 the sound is quite what one expects from the price. I would not say the EF-5 punches above it’s weight stock, but rather falls exactly where it should given the price bracket of $500.00 or less. A competitor I have experience with would be the Ray Samuels Audio XP-7. This off the grid amp sells for $500.00 and comes stock with the OPA627. On my personal unit I had Ray install the 797 chip instead to bring it closer to the performance of the HR-2. The stock EF-5 competes easily with the upgraded XP-7, and surpasses it in drive and extension. Replacing the OP275 with the OPA627 was clearly a full step up in all departments. Treble extended further and clearer, as did bass. Midrange purity was refined through faster attacks and better decays. Between a upgraded XP-7 and upgraded EF-5, I would pick the EF-5 hands down. The XP-7 brings back a more laid back memory. Slower to react and less incisive, the XP-7 would be a better fit for those who find their source or cans a bit to forward or aggressive. Over all this op amp upgrade will net you the biggest increase in performance out of the three tweak under review. While this is quite the upgrade I would not say it puts the amp into the next class of performance overall, say in the category of the ALO Amphora or the like, but it is approaching that boundary. The next two tweaks will take it not only that far, but in this reviewers opinion even further.

Furutech Rhodium Fuse Mod.

I have since had an informal lesson in the purpose of fuses from Bob Prangnell, but at the time I purchased, received and played with the fuse upgrade I had no idea what they really did. I new it had something to do with power, but that was about it. Upon my first listen I was disappointed. I have read where some high end fuses are directional, but as Furutech’s website mentioned nothing about directionality for my model fuse I didn’t think about it. After a week of not being able to hear not only a improvement, much less any change, I decided to swap the direction of the fuse. Viola, there was my money well spent. Not only was I now able to clearly define what difference there was, there was an improvement as hoped. Back when I had my HeadRoom MicroStack rig I upgraded to the DeskTop Power Supply. This upgrade brought only a small increase in performance, but it was exactly what that rig needed. A touch more organic sound with less fatigue during long sessions. This is what the Rhodium Furutech fuse does for the EF-5. A cleaner, grunge-free sound flows through the amp. Flow is really the apt description here. My previous favorite amp, the Amphora had the quality. A flow with no force. An ease about the presentation that gave way to hours of music with no aural discomfort. How or what the upgraded fuse is doing to make this change I do not know. I don’t have to know nor feel the need to know. I only hear it’s work being done. And what glorious work it is. At nearly $50.00, this upgrade is the most expensive in this review, and the second most felt.

Tube Damper Mod.

Right off the bat I’m going to tell you this is the least noticeable mod. When I first got this damper I was hoping to hear more, alas I never did, but what I did hear is worth the money to me. Your milage may vary. I mentioned that the fuse gave the sound a sense of organic flow, but with no force behind it. If one were to take that description and apply it visually, one could sum up an image of the Nile of Amazon river. It’s massive and organic in it’s calming flow. The tube damper then becomes the torrent of the waterfall at the end. Now neither the Amazon or Nile ends with a waterfall, but imagine the falls at Niagara in North America. Before the falls, (before the tube damper) the river flows and meanders in quite the tranquil setting. When the falls approach, (insert tube damper) the water rushes forward with more force. The tube damper has this effect though it’s quite minor. Because it slides on and off A/Bs are easily accomplished. Without, flow. With, more force, gumption, and grunt. There is a propulsion gained with the damper in place. Again as far as the science or physics is involved, I don’t know. But the result is clear. For $40.00 this is the last tweak one should invest in when considering price to performance.

A Surprise and Addendum.

As I was playing around with these tweaks I also took delivery the lowest model of the MapleShade brass weights and footers. Because I was trying to keep the EF-5 review intact from further upgrades to preserve the integrity of my findings I installed the footers and weights on my almost half as expensive Schiit Asgard. Together the footers and weights cost $94.00. But added to the $250.00 Asgard, I by far preferred the sonic presentation of the cheaper amp. It would seem from this admitted limited experiment that vibration control is the more important issue to address, even than a better amp it would seem.

I promised at the beginning in this write up that I’d address the issue of hum from the power supply chassis of the EF-5. Sticking with the maple wooden buttons as footers, the weights from Mapleshade get rid of about 80% of that annoying hum. Installing the brass surefeet in place of the wood buttons totally squelch the bad vibes. Problem solved.

Happy Tunes,


Categories: Amplification

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Reply kboe
1:15 PM on October 30, 2011 
Review published and finished.
Reply Amine Slimani
3:27 PM on October 31, 2011 
kboe says...
Review published and finished.

That is a very nice review as usual Kevin!

One question though, which one do you prefer: Asgard + Mapleshade or EF-5 + Mapleshade?

Regarding your findings about the importance of the vibration control, I couldn't agree more. Vibration control is one of the most important tweaks (along with power filtration). Although, I suspect that vibration control is most effective on lower end/lighter equipment. I use sometimes the less than $200Little Dot MKIII with the more than $300 Aktyna ARIS footers and the sound quality is amazing. The Aktyna ARIS aftermarket feet lift tremendously the performance of the LD MKIII, well beyond what a $200 amp "should" sound.
Reply kboe
7:21 PM on October 31, 2011 
Amine Slimani says...
That is a very nice review as usual Kevin!

One question though, which one do you prefer: Asgard + Mapleshade or EF-5 + Mapleshade?

Regarding your findings about the importance of the vibration control, I couldn't agree more. Vibration control is one of the most important tweaks (along with power filtration). Although, I suspect that vibration control is most effective on lower end/lighter equipment. I use sometimes the less than $200Little Dot MKIII with the more than $300 Aktyna ARIS footers and the sound quality is amazing. The Aktyna ARIS aftermarket feet lift tremendously the performance of the LD MKIII, well beyond what a $200 amp "should" sound.

It depends on the model of AKG I am using as to which amp I prefer. When using the higher end leaner more lit up 702s, they benefit from the warmer, suppler and more forceful driving EF-5. If my ears fancy the 240s, which happens a lot, then the more white sounding, hyper and leaner Asgard is what helps to caffeinate the softer rounder 240s.

The Mapleshade footers and weights make the most difference on the Asgard.

I would prefer the Asgard/AKG K-240s combo with the Mapleshade footers over the fully modded EF-5/AKG K-702 without the footers. Hows that for wild!

So I would have to agree with your sentiment on the importance and role of resonance control as a major, major player in the final quality of sound.
Reply kboe
12:14 PM on November 7, 2011 
Taken from Amines AP2 Review.


A question that always kept me wondering is how a digital transport (or cable) can affect the perceived dynamics. It is relatively understandable that stronger and better designed power supplies on the analog portions of the signal can make the signal more dynamic (or at least not hinder its dynamics), but how a digital transport can affect such heavily the perception of the dynamics of an audio chain is a lot more difficult to comprehend?
While I don?t haveany clear cut answer, I suspect that it might have something to do with the way impulse signals are handled. Based solely on my listening, it seems to me that low jitter converters generate (in the analog domain after it has passed theDAC) narrow impulse responses, while high jitter converters generate fatter, less narrow impulse responses. The area (energy) in both cases could be the same (so that there would be no difference when measuring the signal in static mode) yet the fastest more narrow impulse response could track more closely in the time domain what happens in the recording signal.

Regardless of the possible causes and explanations of such a phenomenon, the Audiophilleo2 seems to ?turbo-charge?the DAC to which it is connected to.
When listening through my other converters, it seems like the performers are somewhat lazy and tired. When switching to the Audiophilleo2, the performers seem to be better rested, more enthusiastic and alive."

This is better description of what I believe is happening to the musical message with the Tube Damper in place. Is it possible that the combination of mechanical and emi/rfi protection is better preserving dynamic information, thus appearing to give greater drive to the amp? I believe so. I was listening and thinking of Amines comments about this and had a "ah-ha" moment.
Reply Kevin Latta
6:24 PM on May 7, 2013 
Would you happen to know the correct fuse value of the Furutech Fuse? Also, which direction did you place the fuse into the power supply? Thanks.