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Please help with DIY headphone amp.

post #1 of 14
Thread Starter 

Hy! Here are some things you may need to know before i begin. I'm a complete and utter noob in audio and i only have experience in basic electronics. Like soldering, wire cutting, reading a basic schematic, etc.

 

The idea of building a DIY amp came to me after i upgraded my PC. On my old one i could easily enjoy a movie without hearing anything around me. On the new one I can literally hear a fly buzzing around me at full volume...

 

I'm not an audiophile in the true meaning of the word, i just need some extra boost on my headphones.

 

I have a pair of Philips SHP1900/10 http://www.p4c.philips.com/cgi-bin/dcbint/cpindex.pl?slg=en&scy=it&ctn=SHP1900/10 that i love and worked great on my old PC. I know that the headphones are rubbish but they serve me well. And i know that they aren't broken because they work perfectly on my laptop. Also i know that the problem isn't software related because i tried all the drivers out there and all the players possible.

 

Sooooooo back to the amp idea. I started to look for a complete amp but all of them were really expensive. I live in Romania where the average salary per month is only around 350$ and i only make about 300$ per month. So a 100$ amp is out of discussion. I started looking at cmoy which would cost me around 10 to 20$ depending on the opamp i choose. But all of them were battery powered and i don't want that. I found the crystal cmoy on instructables which was powered by a switching power supply but it didn't have a volume control. I found the JDS Labs CmoyBB but it was also powered by a battery and it has really small caps and i understand that small caps mean poor sound quality (At least that is what i read here: http://tangentsoft.net/audio/cmoy-tutorial/parts.html#req see this annotation below: "* These caps are much bigger than the ones in the photos on subsequent pages, and so aren’t great choices for amps in mint tins and other compact enclosures. In exchange for the bulk, you get better sound. The farther down the list of alternatives you go, the worse the sound gets, with the last ones still being okay, but recommended only when space is at a premium."). Then after a little digging i found out that most Cmoys have a virtual ground  (BTW i also don't know what that means) and that virtual grounds have a poor sound quality also.

 

Now with the part that i need help with.

 

I want a cmoy headphone amp with:

 

- an active ground

- volume knob with an on/off switch in it

- an integrated power supply so i can power it from a 10 - 15 V power supply that i have around the house (just like the crystal cmoy on instructables)

- power LED

- size does not matter. if big caps are the best option than by all means i want them. I will be running it on my desk.

- cheap build. The cheapest, the better.

 

And after reading a little more on the subject (this post in perticular: http://www.head-fi.org/t/243642/best-sounding-cheep-op-amp-for-cmoys-opa2227-opa2228-ad8066-other#post_3032335 by majkel) i would like it to be built around the AD825 opamp which i read that is the best sounding amp around. But because it's a SMD amp i am open to any suggestions for an alternative 8 pin dip amp that is just as good but not too pricey. I had a look at the AD797 but it's way to pricey. If anyone could lend a hand with a schematic and a parts list i would be so happy!  Thanks to everyone that took the time to read my post and know that i appreciate the time and effort! Hope to hear from somebody soon and thank you in advance for the helping hand. I really appreciate it!


Edited by adrianf88 - 11/6/13 at 1:33am
post #2 of 14
Here's a link to a thread where I have shown some wallwart based supplies http://www.head-fi.org/t/572822/headphone-amp-dc-supply

I think the third diagram is most suited to running a simple cmoy.

Here's another link showing a cheap PCB kit for a cmoy with a good opamp included http://www.head-fi.org/t/640006/diy-wooden-amp-enclosure-and-amp-project-all-under-25-tutorial-for-diyers

You won't be able to fit everything in the enclosure shown in the second thread, but you can change the details for yourself.

These 2 threads show the basic requirements for a minimum expense mains power cmoy which should come in under $50.

w
post #3 of 14
Thread Starter 

Hey! Thanks a million for the advice, but i"m not really planning on buying a kit. I already have a pcb and some resistors so i would like to build my own. But at least i really like the casing made out of wood. At least part of my problem is solved. I will also take a look at the power supply, :) Thanks again and i really hope to hear any other opinions to my unique problems. :)

post #4 of 14

The RA-1 kit is a decent little amp, only downside is the lack of power supply protection, and startup/shutdown thumps.  I've built a couple of them from ebay kits and have pretty much replaced every single component on my own out of interest to see how far i could improve it, plenty of fun to be had customizing them.

 

For the power supply i would use a bit of each design in the above link, but use a virtual earth design.  For example here is the Objective2 schematic, http://lh4.ggpht.com/-J75-73v2hYo/Tl1PO1lP6XI/AAAAAAAABYA/PSx1SWm3S5I/s1600-h/nwavguy%252520o2%252520schematic%25252030aug11%25255B3%25255D.png basically copy the top part up to the two .22uf caps after the voltage regulators, that way you have a +/- 12v and a center 0v to connect to the RA1 board. The RA1 board then has two 100uf smoothing caps and two 0.1uf caps which you can play with to clean up the supply.  I also experimented with a LM317/337 based power supply but the simpler 7812/7912 designs worked just as well.

 

Instead of a generic wall adapter a better option is to power it from a small dual tap toroid or r-core transformer.  If you dont fancy going DIY for the supply you can use one of the ready made power supplys from ebay, or use one of the bare PCB's if you want to build your own.  I can recommend the supplies from this seller http://www.ebay.co.uk/sch/m.html?_odkw=&item=151082813897&pt=UK_BOI_Electrical_Components_Supplies_ET&_osacat=0&hash=item232d3cc9c9&_ssn=audiowind-2005&_trksid=p2046732.m570.l1313&_nkw=regulator&_sacat=0&_from=R40 , i build my own PSU using one of their dual supply pcb's with a small toroid for my own build.

 

Listed below are ebay kits listed in order of preference, top most having the better quality parts, but you probably end up replacing everything anyway.

 

http://www.ebay.com/itm/DIY-RA1-Headphone-Amplifier-Kit-Power-AMP-JRC4556AD-C39-/110620088020?pt=US_Pro_Audio_Amplifiers&hash=item19c17896d4

http://www.ebay.com/itm/DIY-RA1-Headphone-Amplifier-Kit-Power-AMP-JRC4556AD/221267088242?_trksid=p2047675.m1850&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D11%26meid%3D2514267658452258608%26pid%3D100011%26prg%3D1005%26rk%3D1%26rkt%3D5%26sd%3D150942801493%26

http://www.ebay.com/itm/RA1-Headphone-Amplifier-Kit-Power-AMP-Kit-DIY/140890002468?_trksid=p2047675.m1850&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D11%26meid%3D2514267658452258608%26pid%3D100011%26prg%3D1005%26rk%3D3%26rkt%3D5%26sd%3D150942801493%26

 

Most important, have fun with it :beerchug:

post #5 of 14
Thread Starter 

Thank you for every piece of advice but as i said, i already have a wall adapter and i believe i also have a bunch of laptop switching power supplies. I just need an amp that can take about 10 - 15V instead of the 9V of a battery. And just in case that the wall adapter is not a switching power supply (i have to look for it around my many boxes of spare computer parts) something to make the amp run good. something simple like in the Crystal Cmoy... 2 caps, 2 resistors and done...

 

My biggest interest is a schematic of a Cmoy that will meet my requirements. Every Cmoy out there comes either as a kit which i don't want or has one or more features that i need missing. If someone could come up with a schematic with the features that i need and eventually a parts list i would be forever in your debt! :D

post #6 of 14

The RA-1 is a cmoy basically, and many of the opamps (default NJM4556) can operate with 4-15v though i find ~12v is the sweet spot.

 

I posted a few RA-1 schematics here http://www.diyaudio.com/forums/headphone-systems/242188-grado-ra1-clone.html , the tangentsoft.net site you linked is a great resource for cmoy designs, and the rest can be found with some googling. 

 

As for the features you want, all you need to do is find a schematic for the bits you want and graft them on.  LED is easy as it only needs wired accross the +/- rails with a suitable resistor, probably ~2.2k but it depends on the voltages and led being used.  I don't know about power switches on volume knobs, never seen one of those.  Active ground is a tricky one as there are many options, suggest you start here http://tangentsoft.net/elec/vgrounds.html , and here http://www.diyaudio.com/forums/solid-state/234665-virtual-ground-regulated-rail-splitter.html

 

To be honest Diyaudio.com is the place you really need to be searching/asking these kind of questions..

post #7 of 14
Thread Starter 

Thank you very much for the suggestions! I will take a look at diyaudio.com. :)

post #8 of 14
Quote:
Originally Posted by mcandmar View Post
 

The RA-1 is a cmoy basically, and many of the opamps (default NJM4556) can operate with 4-15v though i find ~12v is the sweet spot.

 

I posted a few RA-1 schematics here http://www.diyaudio.com/forums/headphone-systems/242188-grado-ra1-clone.html , the tangentsoft.net site you linked is a great resource for cmoy designs, and the rest can be found with some googling.

 

As for the features you want, all you need to do is find a schematic for the bits you want and graft them on.  LED is easy as it only needs wired accross the +/- rails with a suitable resistor, probably ~2.2k but it depends on the voltages and led being used.  I don't know about power switches on volume knobs, never seen one of those.  Active ground is a tricky one as there are many options, suggest you start here http://tangentsoft.net/elec/vgrounds.html , and here http://www.diyaudio.com/forums/solid-state/234665-virtual-ground-regulated-rail-splitter.html

 

To be honest Diyaudio.com is the place you really need to be searching/asking these kind of questions..

 

Why is that?  We were doing headphone amps here a long time before diyaudio thought they were worth the trouble.  They are also a lot less patient with noobs than most people are around here.  If you're specifically referring to the RA-1, that makes sense, because it's in direct conflict with Grado and Head-Fi won't take kindly to that.

 

Anyway, besides continuing to use the search here, there's a wealth of designs available in the library on Headwize.  It's no longer a forum, but Headwize was started by Chu Moy (as in CMoy): http://headwize.com/?page_id=5  Lot's of good history there and general advice on a lot of DIY-circuits.


Edited by tomb - 11/7/13 at 4:19am
post #9 of 14
Quote:
Originally Posted by adrianf88 View Post
 

Thank you for every piece of advice but as i said, i already have a wall adapter and i believe i also have a bunch of laptop switching power supplies. I just need an amp that can take about 10 - 15V instead of the 9V of a battery. And just in case that the wall adapter is not a switching power supply (i have to look for it around my many boxes of spare computer parts) something to make the amp run good. something simple like in the Crystal Cmoy... 2 caps, 2 resistors and done...

 

My biggest interest is a schematic of a Cmoy that will meet my requirements. Every Cmoy out there comes either as a kit which i don't want or has one or more features that i need missing. If someone could come up with a schematic with the features that i need and eventually a parts list i would be forever in your debt! :D


Start here

 

Watch These

 

You can thank me Tangent later...


Edited by Avro_Arrow - 11/7/13 at 5:02am
post #10 of 14
Thread Starter 

@tomb Thank you! You are a life saver! I found the original Cmoy article with everything on it! Powering, volume control, schematics, everything! I'm still waiting on a friend who has one of those to see how it sounds but i'm confident i'll end up building one of those!

 

@Avro_Arrow Thanks for your time, but i already knew tangents site. It's a little bit confusing for a beginner like myself so all  got from there was dead ends after dead ends so i don't think i will be using anything from there.

post #11 of 14
Quote:
Originally Posted by tomb View Post
 

Why is that?  We were doing headphone amps here a long time before diyaudio thought they were worth the trouble.  They are also a lot less patient with noobs than most people are around here.  If you're specifically referring to the RA-1, that makes sense, because it's in direct conflict with Grado and Head-Fi won't take kindly to that.

 

I found them very helpful over there, and some very knowledgeable people. Just seemed a better fit to me, Head-fi's tend to buy gear, DIY'ers prefer the challenge of building it themselves, certainly looking for schematics i would never have thought to search/ask here.

 

The possibility of Head-Fi having an issue with RA-1 Clones never even entered my head, though i cant see why, or is Grado a forum sponsor?

post #12 of 14
Quote:
Originally Posted by mcandmar View Post
 

 

I found them very helpful over there, and some very knowledgeable people. Just seemed a better fit to me, Head-fi's tend to buy gear, DIY'ers prefer the challenge of building it themselves, certainly looking for schematics i would never have thought to search/ask here.

 

The possibility of Head-Fi having an issue with RA-1 Clones never even entered my head, though i cant see why, or is Grado a forum sponsor?

Well, maybe they've changed over the years.  However, keep in mind that this section of Head-Fi is called "DIY (Do-It-Yourself) Discussions."  So, you're making a leap if you think this section is for buying gear.  Yes, we get those requests sometimes, but they're re-directed quickly.  This section has a long and proud history of supporting some of the first headphone amplifier designs available - DACs and power supplies included.

 

As for Grado supporting/sponsoring Head-Fi, perhaps you've heard of the Head-Fi/Grado HF-1 and HF-2? ;)

post #13 of 14
Quote:
Originally Posted by tomb View Post
 

Well, maybe they've changed over the years.  However, keep in mind that this section of Head-Fi is called "DIY (Do-It-Yourself) Discussions."  So, you're making a leap if you think this section is for buying gear.  Yes, we get those requests sometimes, but they're re-directed quickly.  This section has a long and proud history of supporting some of the first headphone amplifier designs available - DACs and power supplies included.

 

As for Grado supporting/sponsoring Head-Fi, perhaps you've heard of the Head-Fi/Grado HF-1 and HF-2? ;)


My bad, don't shoot the new guy :bigsmile_face:

 

I had heard of the HF-1 and 2 but knew nothing about them, now that i have googled it the penny has dropped, i feel like i was living under a rock for not knowing that...

post #14 of 14

No shooting - just trying to correct the record. ;)

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