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

post #91 of 101
Thread Starter 
Quote:
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:

http://www.fidelityaudio.co.uk/regulators-144-c.asp

 

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 101

Need to cut some acrylic first

Quote:
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 101
Quote:
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:

http://www.fidelityaudio.co.uk/regulators-144-c.asp

 

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 101
Thread Starter 
Quote:
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 101
Thread Starter 
Quote:
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 101

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

 

http://www.partsconnexion.com/regulator_belleson_spj78.html

 

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 101

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 101
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 101
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 101
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.

 

Remark:

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 headphone 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. 


Edited by inter voice - 8/24/15 at 5:37am
post #101 of 101
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:

RCA clear top

RCA Gray Plate

Mullard NOS 

Sylvania 6189W Green label

Sylvania 5963 D grid

Full Music gold pin

Brimar Long Plate NOS

 

I found RCA Clear Top and Full Music gold pin both provide very balanced sound signature on all of the frequency ranges. Apart from that both have very fast response over the other tubes. Having said I am not saying the other tubes are not as good but they just do not meet my personal taste.

 

Among RCA and Full Music personally I prefer the later as my ears told me that it gives slightly cleaner sound than the RCA clear top. Now I have replaced my Mullard with Full Music in my EF-5. 

 

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


Edited by inter voice - 8/24/15 at 7:54am
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