Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › Hifiman EF-5 headphone amplifier mods and rolls
New Posts  All Forums:Forum Nav:

Hifiman EF-5 headphone amplifier mods and rolls - Page 2

post #16 of 69
Thread Starter 

I have swapped SYLVANIA 6189W by Mullard ECC82 12AU7.

I found the bass is more tight with slightly better mid range.  The HF remains the same.  It seems Mullard has better overall SQ. 


Edited by inter voice - 5/1/14 at 10:17pm
post #17 of 69
Thread Starter 

I have just ordered one RCA clear top 12AU7 which is to be shipped from the US.  I will compare its performance with my other 12AU7s when in hand.

post #18 of 69
Thread Starter 

After comparing all the 12AU7 I got I found SYLVANIA 6189W suits my taste the best.:):darthsmile::L3000:

post #19 of 69

Thanks very much for the detailed modifications to the EF-5, I have wished to replicate this modification as well, but with limited electrical background I do not know what barrier diode values that were changed out.

Is there any way to find this out as i really would like to try the complete modification to this amplifier. Thanks again.

 

Dwayne

post #20 of 69
Thread Starter 
Quote:
Originally Posted by dkp1 View Post
 

Thanks very much for the detailed modifications to the EF-5, I have wished to replicate this modification as well, but with limited electrical background I do not know what barrier diode values that were changed out.

Is there any way to find this out as i really would like to try the complete modification to this amplifier. Thanks again.

 

Dwayne

If you refer to the diodes they are SCHOTTKY DIODES.  

Something like this in eBay:

http://www.ebay.co.uk/itm/1N5822-SCHOTTKY-DIODES-3AMP-STMicroelectronics-/230885510740?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item35c1d94e54

 

If you refer to the valves then any brand of 12AU7 can do but those brands that I used are preferred as they produce better sound.  Search 12AU7 and you can find the valves with different brands you want.

post #21 of 69

can you show what's inside power supply box ?

 

is it only transformer or full linear power supply ?

 

btw I love this amp even in its stock form no matter the price for hifimans

 

main weak point is the pot (resistors ladder) and bad contact in time between different levels of volume, usually cracks, pops when you change it (I checked a few amps and all had the same flaw - I guess oxidation between contacts) - I am gonna buy another one from the newest revision and advice to double check the pot before its shipped


Edited by magicman - 8/19/14 at 1:30am
post #22 of 69
Thread Starter 
Quote:
Originally Posted by magicman View Post
 

can you show what's inside power supply box ?

 

is it only transformer or full linear power supply ?

 

btw I love this amp even in its stock form no matter the price for hifimans

 

main weak point is the pot (resistors ladder) and bad contact in time between different levels of volume, usually cracks, pops when you change it (I checked a few amps and all had the same flaw - I guess oxidation between contacts) - I am gonna buy another one from the newest revision and advice to double check the pot before its shipped

The power supply box contains only a big Toroidal Transformer and nothing else.

 

The stock pot is cheap and useless. I suggest you to change it to an audiophile one as what I had done (see pic. I have posted previously)

post #23 of 69

thank you for your answer - so it's like I thought since there is AC input in amplifier module ...

 

After warranty period I will replace this pot for some alps for sure - is there any alps that matches perfectly its place without any modification (dimensions) ? (I guess it's something about 47-50k ?)

 

btw still this amp just thrills me with transients response (attack+decay), dynamics, ultra clarity and details, I have never heard amp with such amount of texture and speed in the mids with such realism, for instance Lyr or even emotiva x-mini is like a total blur put on the image and you can do anything to bring back blurred informations even using some ultra detailed dac

 

for classical recordings it's pure joy, explosion of emotions, can hear even subtle nuances, bows scraping etc

 

separation of instruments is stunning in my opinion

 

I got amazing results with high impedance phones either like hd600&hd650 and like you said before it's match made in heaven for audezes


Edited by magicman - 8/19/14 at 10:05pm
post #24 of 69
Thread Starter 

You need to make minor modifications to fit the alps pot but that is easy.

 

IMHO the SQ from the stock EF-5 amp. is just average BUT after all the modifications you will be amazed by the great improvement in the sonic quality.  Apart from LCD-X the modified EF-5 can even drive HD-800 (well known to be hard to drive due to high impedance) like a charm without setting the gain to High. I strongly suggest those who own EF-5 to go ahead with the modification and I can assure they will not regret.

post #25 of 69

I like its stock form, dont want to change a thing unless I could listen to your final work and really liked it ...

 

I am afraid driving hd800 is not thanks your modifications, they don't raise max output power of the amp (which is really good even for high impedance HPs and drives them perfectly, very universal amp), just cosmetics

 

sorry but I am always very sceptical about many users modifications

 

tried many interesting 12AU7 even legendary radiotechnique from 60s but I always returned to original full music 12AU7 which brings amazing upper mids, speed and details, especially for instruments like piano, cello or violins

 

the only thing that is real pain in the ass is that crappy pot - I mean as long as it works it's cool but once it starts to crack/pop when changing the volume all you can do is clean oxidation or install some nice alps (I would install legendary alps black beauty but it's even bigger than rk27 so it might be hard to install correctly)

 

anyway love the thread, this amp is totally underrated and unknown among community, such pitty


Edited by magicman - 8/20/14 at 9:14pm
post #26 of 69

A few months ago I started tube rolling out of curiosity (after two years of ownership), and I found the Philco black plates made the amp sound better IMO. Mids are more intimate with no sibilance. For a fairly cheap upgrade I would recommend this tube :). Sadly I have no experience and limited knowledge with soldering and more technical, electrical stuff in general so I have not the balls to open up the amp and do further mods 

post #27 of 69
Thread Starter 
Quote:
Originally Posted by Legi0n View Post
 

A few months ago I started tube rolling out of curiosity (after two years of ownership), and I found the Philco black plates made the amp sound better IMO. Mids are more intimate with no sibilance. For a fairly cheap upgrade I would recommend this tube :). Sadly I have no experience and limited knowledge with soldering and more technical, electrical stuff in general so I have not the balls to open up the amp and do further mods 

Apart from changing the tube why not try changing the opamp which is quite a simple job to do :tongue:

post #28 of 69
Thread Starter 
Quote:
Originally Posted by magicman View Post
 

I am afraid driving hd800 is not thanks your modifications, they don't raise max output power of the amp (which is really good even for high impedance HPs and drives them perfectly, very universal amp), just cosmetics

 

.. this amp is totally underrated and unknown among community, such pitty

You are right that the modification did not increase the output power but I can only say it improves the SQ by a very big margin.  What I meant was that the stock EF-5 is a good amp and it has sufficient power to drive the hard to drive CANs like HD800 etc even at low gain setting.  

 

I agree with you that not so many people is aware of this amp's performance and not too much was said among community. As to the selection and use of tube it is very much on personal preference.

post #29 of 69

I would love to see all photos that show modification of front panel in order to install new pot + some description

 

I will do this for sure in the future unless they changed it to something much better in the newest revision

 

I am afraid of smoothing everything because there is a point when you start losing edge of the amp, transients handling and ultra detailed presentation (high definition) though I agree this amp can be harsh but it depends mainly on recording

 

I just can't stop listening to piano with this amp, so powerful, amazing decay and separation of notes (Lisitsa, Grimaud, Argerich ...)


Edited by magicman - 8/21/14 at 1:14am
post #30 of 69


Just some of my thoughts on the EF-5. I purchased mine 3-4 years ago. I'm guessing it's the first revision since my pcb doesn't have a cut out in the front where the volume control is. My pcb appears to have more parts on it than the one shown here. I tried to install an Alps Blue pot and even a smaller more standard size pot such as Radio Shack sells, but neither will fit due to the pcb coming all the way to the front of the cabinet. I have ordered a small Noble carbon pot to try but haven't received it yet. If you want to check your amp to see which pcb you have you can remove the four screws in the front panel and pull the front panel forward to see if your pcb has a cutout such as the amp shown here. The pot which came in my amp is a small Alps which I think is a plastic conductive model and doesn't have the clicks.

 

As far as changing the OP275 opamp, be aware that some other opamps may not be ideal in this amp (or any other amp). The 'audiophile' opamps all need some form of compensation to work in a specific circuit and just replacing an opamp with another opamp that isn't optimized can cause problems. I tried other opamps in my amp but they all ran hot temperature wise which means they may not be totally suitable for this circuit. If you try another opamp or dual opamps, be sure to check the top of the opamp with your finger to see if it is getting hot. Some heat is probably ok but if it is too hot to keep the tip of your finger on then I personlly wouln't leave it in. I have seen an opamp oscillate in a circuit (not this amp) and get red hot in a matter of seconds and it will burn up if the amp is left on. In other words, just replacing one opamp with an 'audiophile approved' opamp is not always a good thing. Since my amp is an older version it may not 'like' other opamps, so the newer version may be fine, but I would check just the same.

 

As far as tubes go, try a 12BH7 or an E80CC/6085. I personally like these better than the 12AU7. Just like opamps just swapping to a different tube number may mean the amp isn't truly optimized for that tube, but it seems to work fine in this amp and won't cause any problems in use. I agree this is a great amp and not as appreciated as it should have been. Head-Fi is often focused on the latest and the greatest at the expense of older amps that are as good or better than the current models. If you can buy an EF-5 used for $250-$300 I don't think you will regret it. I will try to take some pictures of my older version amp when I finish working on it so you can see the difference between mine and the newer version shown here.

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Headphone Amps (full-size)
Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › Hifiman EF-5 headphone amplifier mods and rolls