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Hifiman EF-5 headphone amplifier mods and rolls - Page 7

post #91 of 111
Thread Starter 
Originally Posted by davide256 View Post

The Burson OP amp definitely improved clarity and ease of reproduction. While the EF-5 lacks the sparkle in the highs and crispness of the iFi Micro, it has a satisfying meatiness to the mid range

vs the "diet food" flavor of the iFi MIcro. And its far better than the stock 275 op amp or the 627AU which just didn't convey the same depth of musical detail. I've decided on top of the $70 spent

for the Burson Op amp to try $50 in other upgrade parts to see if the transient "snap" can be improved


(4) avalanche diodes

(1) Alps blue velvet pot

(6) Panasonic FR caps 35v 1000/2200uf values

I suggest you also change the 12V low voltage regulator with a very low noise one. I used one of these:



Burson  OP amps are nice and I used them in my modded Marantz CD-63 CD player.

Edited by inter voice - 7/28/15 at 12:12pm
post #92 of 111

Need to cut some acrylic first

Originally Posted by jaxz View Post

Nice. Picture please 👀

It wouldn't look very pretty right now with the Burson sticking up like a telephone pole. I intend to get some acrylic this weekend and use some PCB board standoffs to build

a cover box about 1/2 inch higher than the original acrylic cover  plate with the Burson folded flat. Will take a picture once that's put together

post #93 of 111
Originally Posted by inter voice View Post

I suggest you also change the 12V low voltage regulator with a very low noise one. I used one of these:



Burson  OP amps are nice and I used them in my modded Marantz CD-63 CD player.

Agree that the discrete regulators help but the challenge is to fit it in the case. Which one were you able to get to fit?

post #94 of 111
Thread Starter 
Originally Posted by davide256 View Post

Agree that the discrete regulators help but the challenge is to fit it in the case. Which one were you able to get to fit?

That is simple, just remove the original 7812 from the PCB.  Drill a small hole on the rear top casing and ensure it is clear of any electronic components. Then fix the new low noise regulator underneath the rear side of the top side casing which also acts as heat sink.  After that solder short leads to connect the 3 legs between the regulator and the PCB.  Job done. (You will find that there is more than enough space to fit a new regulator underneath the rear inside top casing.)  

My advise if you decide to buy SPower ensure buy one with high current output as the current being drawn by all the circuitry is quite high and much heat is generated.

I can assure you that you can hear a big improvement on the SQ of EF-5 after changing the regulator. 

Edited by inter voice - 7/28/15 at 12:57pm
post #95 of 111
Thread Starter 
Originally Posted by davide256 View Post

Need to cut some acrylic first

It wouldn't look very pretty right now with the Burson sticking up like a telephone pole. I intend to get some acrylic this weekend and use some PCB board standoffs to build

a cover box about 1/2 inch higher than the original acrylic cover  plate with the Burson folded flat. Will take a picture once that's put together

Why not pile up 2 IC sockets and then fit the Burson OP amp on top of it.  With that I believe there should be sufficient clearance to insert the OP amp into the original socket without using extension leads.  After that you may DIY an acrylic cover to make it look nicer. That was original in my mind when I had a strong desire to fit two Burson OP amps in but unfortunately until now I have not done that.

Alternatively you may also like to change the entire casing and fit everything including the Transformer into it.  That should not be a big job. With that you may carry out more component changes without the worry of space constraints.  That was also once in my mind.

Edited by inter voice - 7/28/15 at 12:55pm
post #96 of 111

I'd rather not get into swapping out the case, so using the flexible extension to lay the Burson flat across the gold heat sinks seems least effort. I am thinking

about trying a Belleson  12V regulator




last nite tried a power cable I don't normally  like with the Ef-5, a Wireworld Stratus 7. On all my other gear, the filter

effect characteristic to this cable suppresses transients, not a good result,  but with the EF-5 it smoothed out the sound,

made it better.

post #97 of 111

Had parts ordered show up. I'm holding off installing the caps and avalanche diodes; diode leads need to be compressed/thinned to fit the eyelets

and I want to measure the cap board voltages to see if I could get lower voltage ELNA or Nichicons to work/fit. I did install the alps 10K pot tonight.

The alps is easier to operate and the amp's sound is now cleaner to listen to. Decided I'm going to use Inter voices recommendation for doubled standoffs to raise

the cover plate, but for now here's how it looks


post #98 of 111
Thread Starter 

Nice work Davide256 :wink:.  I still  recommend you to change the 7812 with a low noise voltage regulator after you have done all the parts swapping.

For me that was the very last mod I had made after carrying out all the swapping of parts,i.e. the pot, the op amps, diodes and caps etc.  Changing the 7812 with a low noise one makes the sound much much more clear and dynamic. Trust me the change in SQ is very noticeable and is a big step up.

post #99 of 111
Thread Starter 

Today I have changed the two opamps inside my EF-5 from LM4562NA (which replaced the stock opamp) with LME49720HA.  Actually 4562 and 49720 have similar operating specifications but 49720 is made of metal case and has better SQ then 4562.  You can also see from my uploaded photos that heat sinks were used on the two 49720s. You may wish to know that when EF-5 has been running for two hrs or so the opamps run at about 60 degrees C with heat sinks on (measured by thermal couple device).


The following photos are uploaded for the reference of those who wish to carry out some mods on EF-5.  You can see that the the volume control VR, capacitors, diodes, opamps and the low voltage regulator were changed.  Tube used is UK made Mullard 12AU7.


On first hearing with 49720 being inserted, I found the bass department of my music playback is more punchy and tight, there are also improvements in the mid range and HF. The overall sound quality is cleaner with better music separations. I am sure after running in the opamps for some time the SQ should be further enhanced. 











Remark made a day after: After burning in the opamp for just 10 hrs the SQ is becoming better and better :bigsmile_face:.  The decision to change the opamp to LME 49720HA is a right move.  Now I am really happy with my modded EF-5.  I will continue burn in the 49720 until it stabilizes.


One more observation, I noticed that the volume output of EF-5 has now increased after changing the opamp and I suspect it is due to higher gain of the 49720HA.

Edited by inter voice - 8/22/15 at 6:20am
post #100 of 111
Thread Starter 

I owned three different headphones,i.e. Senn HD-800; Audeze LCD-X and HiFiman HE-500 and they all have different impedances. HD-800 has 300 ohms, LCD-X has 20 ohms while HE-500 has 38 ohms.


Though it was claimed by the maker that EF-5 can handle headphones with impedance from 2 ohms to 2K ohms I found that EF-5 pushes low impedance headphones better than high impedance headphone.  In order to make EF-5 matches better with high impedance headphone today I have increased EF-5's impedance by inserting in series a 33 ohm resistor to the headphone socket as shown in the following picture. Now the EF-5 pushes my HD-800 like a charm.

With the additional resistor being inserted I found that there is no loss in SQ when low impedance headphones are played.  The only drawback I can observe is that the volume needs to increase by a bit to maintain the previous level of output when using low impedance headphones but on high impedance headpnones the volume output seems to be the same. As a matter of interest after this minor mod the volume setting are almost the same for my 3 CANs.  When I listen my CDs the volume knob seldom goes over to 10-11 o'clock position and the sound level is more than sufficient to enjoy my music.



In the weekends I tried to find out the sonic performance of my 3 headphones I owned when being driven by EF-5.


My finding based on my personal preference is that EF-5 can drive HD-800 and HE-500 very well.  The Bass and HF are all well presented and with good mid range. (EF-5 is powerful enough to drive these 2 headphones and the volume knob setting at 11 o'clock is more than enough for music listening.) Overall HD-800 is slightly brighter and I can hear lots of minute HF musical instrument playback (this is due to the headphone's sonic signature) while HE-500 gives more balanced presentation but I found it has slightly less clarity and musical separation than HD-800.


However EF-5 and LCD-X is not to my personal taste as the music is too dark and the HF has rolled off too much even though the vocal and LF presentation is exceptionally good. 


Further update

Now the EF-5 has been run for more than a week and I have further auditioned its performance with HD-800 and HE-500. Tube used is RCA Clear Top (later changed to Westinghouse 5963 and eventually to Telefunken ECC82), I am surprised that EF-5 matches wonderfully well with HE-500 and makes this CAN very neutral. The music is very pleasant to my ears though the sound staging is not as good as HD-800. The dynamics is good and the bass is reasonably well presented.  I can only say it is a very good partner.


As to the matching of EF-5 with HD-800 I found that overall the HF is too much extended and is not to my taste unless someone likes to hear all the very minute HFs.  The bass and mid range is a bit lean but it does have good dynamics and impulse. It is still a good match but when compared with HE-500 I still prefer the HE-500.


Lastly same as my previous findings EF-5 is not a very good match with LCD-X as the HF is rolled off by a big margin though the mid range and bass is exceptionally good. 

Edited by inter voice - 9/9/15 at 7:49am
post #101 of 111
Thread Starter 

In the last weekends I spent quite some time to compare the performance of different 12AU7s that I owned and see which one suits my taste most.


I have compared the following 12AU7s using HE-500 as reference:


RCA clear top 12AU7

RCA Gray Plate 12AU7

RCA 5963 Balck Plate with square getter

Westinghouse 5963

Mullard 12AU7 NOS 

Sylvania 6189W Green label

Sylvania 5963 D grid

Full Music gold pin 12AU7

Brimar Long Plate 12AU7 NOS

Tung Sol 12AU7 (re-issued)

Phillips 5963 ECG

Telefunken ECC82


After comparing all of the above tubes one by one with my headphones I found Telefunken ECC82 and Westinghouse both provide very balanced sound signature on all of the frequency spectrum. Apart from that both have very fast response over the other tubes and give very clear music presentation. The music is forward which is also to my preference. Having said I am not saying the other tubes are not as good but they are less favorable to my ears and taste.  Actually Sylvania 6189W, Full Music and RCA Clear Top 12AU7s are also very good tubes and are very closed competitors. 


Among Telefunken and Westinghouse personally I prefer the former as my ears told me that it gives slightly cleaner sound than the Westinghouse. Now I have replaced my RCA Clear Top with Telefunken ECC82 in my EF-5 and I am continuing burning in the tube to achieve its best performance.


I have to stress that the above conclusion is only based on my personal preference using headphone HE-500 as reference and you need to try it out yourself and found the best tube to suit your taste.




Please note that if Telefunken ECC82 or Westinghouse 5963 is used to paired with HD-800, I found the music is a bit too bright for leisure listening.  However if Mullard 12AU7 is used it will tame the HF and makes the music from HD-800 more smooth and pleasant to my ears.  On the other hand if Mullard is being used to pair HE-500 and LCD-X both CANs loose all the very high frequencies and the music becomes dull to me. This confirms the old saying that tubes and headphone needs to be matched to achieve their best performance.     

Edited by inter voice - 9/9/15 at 7:53am
post #102 of 111

so how about installing new VR ? will ALPS RK27 BLUE BEAUTY fit ? is it 2x50K LOG ?


can you show the pictures with wires to the pcb where to solder which wire ? will stock volume knob fit or do I have to buy another one ? ( I guess alps is like 6mm axis) Thanks man

Edited by magicman - 9/22/15 at 11:59pm
post #103 of 111

This amp is seriously something special, got it again almost in non used condition, cant believe how it changed with some time on it (like a few weeks of continous using), especially in details retrieving, lowest bass, slam and punch, out of the box brand new it was lifeless and a bit harsh


might be the tube burn-in too, with some nice dacs like nfb-1.32 results are out of my mind, I have been going to new concert hall recently, tuned by NAGATA acoustics (Japan/Los Angeles) in order to listen unplugged instruments like steinways pianos, cellos, bass, drums, violins, female soprans etc and after a few auditions I can't believe what I have in my home, every single nuance even the smallest one is played like a copy of real life instruments but it's also HE-4 that makes match made in heaven with EF-5 and good source, from tonality to thunderous dynamics through those transients response ... Especially in classical, jazz, metal/rock/gothic


Need to check it out with HE-6 and HE-800, these headphones are very unique to me from everything available on the market right now and worth the price when in great headphone rig ... Heard that even 2-3W per channel from EF-5 can sound really amazing with HE-6 in terms of tonality, punch, soundstage and realism, anyone tried it with HE-6 ?


I am using after some serious burn-in RCA 12AU7 BLACK PLATES :D after choosing from like 20 vintage tubes ...

post #104 of 111

Where should be 7th wire soldered (2x3 pins are L/R channels) ? I guess it's VR grounding and it goes to output jack GND directly from chassis of VR ? Where did you solder it ? to the screw ;) ? and how about mechanical compatibility and its dimensions / axis diameter ?  Does it fit to original volume knob ? what needs to be done to place it there ? Thanks

post #105 of 111
Hey, fellas. I know this thread is dead like Linclon but I was hoping to get a little direction on modding my recently acquired, used EF-5... Hopefully I don't summon any slumbering dietys in the process!😊

So, since the day I bought it, the tube socket has been VERY tight and it's difficult to properly seat the tube. The included Full Music (seller claimed 500 hrs on it) had a pin fall off the first time I even went to roll a new tube. Even when it feels like it's all the way in, a lot of the time I'll lose sound in one channel and have to shift it. I've tried Deoxit5, I've tried using a toothpick; Honestly, I just want to replace it. It looks quite simple but would still appreciate some input.

I'm looking to replace the opa275 with either a Burson SS V4 or V5. If I'm correct it should be a dual and I can just remove the OP275 and install the Burson into the existing DIP8, correct? Now, am I going to have to change anything else for this to work/ will there be compatibility issues? Is the JRC going to fine with the other op amp upgraded?

I would also like to change out the volume pot. It has that sketchy noise when you change the volume and I feel like there is a loose connection because I'll lose my left channel if Im rotating it. Alps blue 10k seemed popular on here but too big? I really wouldn't want to have to "make space" for a new Vol. Pot if theres a highly recommended alternative that fits without any issues.

I sincerely appreciate anyone who is taking the time to read this. I'm sure most of you know this awful feeling im experiencing. Somewhat helpless and not knowing who to turn to or where to look for guidance while your equiptment is damaged. It's literally haunting.


Need advice on changing out the tube socket.
op275 to burson ss v4/5 ok without having to upgrade anything else?
Is alps blue 10k vol. pot difficult to install due to size or does anyone recommend an equal quality, smaller alternative?

Oh, yeah. My DAC is a Modi 2 Uber and the headphone I use are LCD-2's (2016) if that affects anyones suggestions.
Thanks!!! 😁
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