heady 0 Report post Posted July 30, 2004 Just want to share my experience in last few weeks building and experimenting with CMOYs. I am currently listening to Mannheim Steamroller on my 4th tweaked CMOY. 1st CMOY: stock components with OPA2134PA - sounded loud but the sound, especially high frequencies was muddy. 2nd CMOY: used .220uF polypropylene caps instead of specified cap in the Tangent website - the sound was much better as the high frequencies sounded less muddy. 3rd CMOY: added another op-amp for virtual ground driver plus buffer, two 470uF 16V Nichicon Fine Gold and two Wima .56uF polyester caps for power to virtual ground - sounded marginally better than 2nd CMOY but much better performance when battery was running lower than 7 volts. 4th CMOY: Uses two OPA2134PA, one op-amp with half as virtual ground driver and the other half for signal ground. Changed R2 from 100K to 1M. Changed the caps to one 470uF 25V Nichicon Fine Gold and two .56uF Wima polyester caps bypass for power rails only. - After about 30 hours of listening, the amp has finally broken in with superb detail and solid bass. At least that's what my mid-fi Panasonic portable CD player -> Tweaked CMOY -> Sennheiser 490 is telling my non "golden ears". I don't know how to get the schematics I used onto this site but I will post pictures of the amp if there is any interest. All the components are sourced from SLT except the Nichicon and Wima caps from Koba Electronics in Peoples Park Centre. I am now looking for a good volume pot with bushing. I got some Matsush*ta (Panasonic) pots from SLT which sounded ok but had no bushing and was a pain to install. Thanks to the other postings in this forum, I will be trying the Alps pot from Farnell. My next project will be to build a Pimeta clone. Thanks to the guys posting on this forum with info on getting components. Share this post Link to post Share on other sites
Q00 0 Report post Posted July 31, 2004 Oooh....good stuff there! Perhaps you could contribute yer ideas to the sgheadphone amp as well? Glad you found your perfect amp heady! ooh yeah and and enjoy your stay! Share this post Link to post Share on other sites
bpribadi 0 Report post Posted July 31, 2004 Thanks for sharing! Congratulations with your new CMoy Can you give us a more detail of Koba Electronics address? It would be usefull for us , thanks! Share this post Link to post Share on other sites
Sipher 0 Report post Posted July 31, 2004 Koba Electronics Address : 101 Up Cross St #03-06 People's Pk Centre Singapore 058357 Telephone : 6533 1672 would like to see some pics of your 4th amp, heady Share this post Link to post Share on other sites
heady 0 Report post Posted July 31, 2004 Thanks guys, this is the board of my cmoy#4, I am still looking for a pot small enough for my tin. I intend to use two 9V batteries in a Hudson's Eumenthol Jujubes tin. Hope the things will fit. This is my 3rd attempt at casing an amp. Share this post Link to post Share on other sites
heady 0 Report post Posted July 31, 2004 This is close up of board. Share this post Link to post Share on other sites
N@Z 0 Report post Posted July 31, 2004 I just love it when DIYers use heatshrink, looks so tidy. Nice one heady. Share this post Link to post Share on other sites
bpribadi 0 Report post Posted July 31, 2004 Well done heady! I love heatshrink to Metal casing will help to reduce hum in some 'hum'full environment (like my office) Or you can buy aluminum die cast from farnell (Hammond casing), then your CMoy will look more solid Share this post Link to post Share on other sites
bpribadi 0 Report post Posted July 31, 2004 Koba Electronics Address : 101 Up Cross St #03-06 People's Pk Centre Singapore 058357 Telephone : 6533 1672 Thanks Sipher! Share this post Link to post Share on other sites
Sipher 0 Report post Posted July 31, 2004 no problem Share this post Link to post Share on other sites
heady 0 Report post Posted August 3, 2004 Hi all, Just an update, I have reverted R2 back to 100K. The amp suddenly sound very spitty/distorted on the higer frequency. This happened when I first built the amp but when I added an additional cap into the power rails, it sounded ok but now it's back. Any way, with the 100K R2, it sounds typical BurrBrown, lots of bass and too smooth top, need a little sparkle. Well, fated to continue search for the right sound? Any way I am building a Pimeta clone to see what it sounds like, using the AD8620 with the HA3-5002 buffer, only one buffer per channel. This expensive hobby leh. Be back when I get the pimeta up and working. Share this post Link to post Share on other sites
bpribadi 0 Report post Posted August 4, 2004 (edited) Waiting for your comments of Pimeta Just remember to turn off your amp before plug in or out the headphone jack. HA3-5002 doesn't have output protection, so becarefull with it Edited August 4, 2004 by bpribadi Share this post Link to post Share on other sites
heady 0 Report post Posted August 4, 2004 bpribadi, thanks for the tip. Share this post Link to post Share on other sites
Goondu 0 Report post Posted August 5, 2004 Thanks guys, this is the board of my cmoy#4, I am still looking for a pot small enough for my tin. I intend to use two 9V batteries in a Hudson's Eumenthol Jujubes tin. Hope the things will fit. This is my 3rd attempt at casing an amp. Where did you get the tin from? I am looking around for the Fisherman's Friend rectangle tin but can't seem to find it nowadays. Thinking of doing up this CMoy amp at the end of the month when I got more time. Thinking of making it real small and truely portable Are there any other designs that are as ultra compact as this? Share this post Link to post Share on other sites
bpribadi 0 Report post Posted August 5, 2004 Well, the big components will be the caps. IC and resistors are small. But small cap doesn't give good sound, so consider that Share this post Link to post Share on other sites
