huangyong 0 Report post Posted November 6, 2003 Calling for all DiYer in SGH. PPA's parts are very expensive, building one can cost up to S$400. my idea is to use the same concept(circuit), replace the expensive parts with equivalent ones( same "spec"ies), and bring down the price to less than S$100. i have post my idea in head-fi, and tangent said it is possible to implement. here is the link: http://www4.head-fi.org/forums/showthread....&threadid=47152 use opa134 instead of opa637.cheap and nice. I will repalce the 12 expensive Intersil HA3-5002 buffer with six JR4556(used in Grado RA-1 amp)dual opamp.( OR other cheaper buffer or opamps ) The dual opamp will be converted to buffer and it will ouput +/-70mA per channel vs HA3-5002 buffer's +/-200mA. ---------------------------------------------------------------------------------------------- Compare (1 channel): Original(buffer): 4 x 200mA = 800mA Moded(opamp): 4 x 70mA = 280mA ---------------------------------------------------------------------------------------------- the output current might be low, and i think you can add more opamps if you like to(JR4556 is only S$2.50 each). the overall circuit(concept) remains the same. except for some rare or expensive parts, where we need to find alternatives. i have finished 1 channel prototype(on copper strip board), but unfortunately i found out that my opa134 is spoilt when i accidentally put my cmoy circuit on a metal plate while power is on.Oh man, i can hear sound "pssszzz", my 4700uF cap had shorted and the whole thing gone.sad, 20 bucks gone. this morning, when i tested my board, using that old opa134, thought still can be used, but the result was anyone wants to join me in developing this amp??? it might not be a high end product, but it's fun and benefitial( gain knowlegde ).Who knows, the amp might sounds nice. SGH has never develope any amp yet, why not we take this chane to explore something new??? Exam is over, i will be free from now to Dec, so will take this time to learn something.hehe..... Share this post Link to post Share on other sites
huangyong 0 Report post Posted November 6, 2003 (edited) Glad that Sijosae came out with his own version of Poorman's PPA. http://www.headphoneamp.co.kr/bbs/view.php..._sijosae&no=161 i am inspired by this: http://www.headphoneamp.co.kr/bbs/view.php...desc=asc&no=154 Edited November 6, 2003 by huangyong Share this post Link to post Share on other sites
N@Z 0 Report post Posted November 6, 2003 Wouldn't that defeat the purpose of utilising the PPA design which is for ultimate sound quallity. Why not just build a META instead? I can understand the Headsave PPA but scrimping to this extent... but if I'm proven wrong & it sounds better than a PIMETA then I'm all for it. I'm surprised Tangent didn't clip you round the back of your ears! LOL! Share this post Link to post Share on other sites
jasonhanjk 0 Report post Posted November 6, 2003 The PPA can still be modded to 4 channel configuration: Left channel Left ground Right channel Right ground The headphone left and right ground should be separate, of course it is called the rich man PPA.... Share this post Link to post Share on other sites
huangyong 0 Report post Posted November 16, 2003 Oohh...yes... my amp works.. Share this post Link to post Share on other sites
huangyong 0 Report post Posted November 16, 2003 (edited) this is my version, using opa134 and jr4556. links: http://sg.f1.pg.photos.yahoo.com/ph/paul_o...view=t&.hires=t Edited November 16, 2003 by huangyong Share this post Link to post Share on other sites
lekguan 0 Report post Posted November 16, 2003 post some impressions? Share this post Link to post Share on other sites
huangyong 0 Report post Posted November 16, 2003 the amp is still in prototye stage, using low grade components like 5% resistor. i will built a good one and then will post the review. Share this post Link to post Share on other sites
Q00 0 Report post Posted November 16, 2003 Oohh...yes... my amp works.. which amp works? the poor man's ppa? how does the lower value compared to the bigger value buffers affect performance? Share this post Link to post Share on other sites
Q00 0 Report post Posted November 16, 2003 oops...misread the first post again so the difference is only the output current right but that can be 'rectified' by adding in more opamps? i wonder if it will affect the sound or speed compared to a dedicated buffer Share this post Link to post Share on other sites
huangyong 0 Report post Posted November 16, 2003 rectified?????? i am not sure whether should use this word or not, expert, help!!! yup, you can add more current by doin that, but don't know whether will change the sound or not, have to try first. bout the speed, dun know?? the slew rate of JR4556 is bout 20V/us. not very fast. but when i compare it with cha47 based on JR4556 alone, it's faster. i think that the opa134 determine the characteristic of the sound. Share this post Link to post Share on other sites
mychew 0 Report post Posted November 18, 2003 hm...another modified PPA on the way waiting for it...work hard. hm...OT a bit..read your post in head-fi Jason. work for u can gain experience but got money or not?lol...at least sponsor me a nice soldering kit la..then i can work for free...haha hmm...wonder huangyong's modified PPA would work fine after he completes it. Share this post Link to post Share on other sites
huangyong 0 Report post Posted November 18, 2003 sorry, the slew rate of JR4556 is only 3v/us , not 20v/us Share this post Link to post Share on other sites
jasonhanjk 0 Report post Posted November 18, 2003 Really like to hear the PMPPA...., drool..... Exam over alredi rite? mychew... Share this post Link to post Share on other sites
