heady

Count me in for the browndog clone. How about it?

I am interested in the PPA board and the pot. Not so keen about the other parts though. Not decided on the opamps yet.

Goodu, I've just "retired" my surgery and "resting" until I start work with someone else. You know lah, we all have to be careful about giving out info about where we work or someone may complain we are advertising without permission.

Thanks bpribadi.

Somehow, diy dentistry doesn't seem as fun to me. (btw, I'm a dentist too)

bpribadi, wow! Really cool. Can't wait for you to post your listening opinion.

starushz, Truth is, I did not tabulate how much I spent but I know it wasn't cheap especially since I bought stuff which eventually were not usable, expecially the volume pots. Bought several to try and most cannot be used in the tins. BTW - if at SLT you saw an old man with bad haircut then it's me.

starushz, Fact is, most of the shop people don't know the difference either. That's my experience. You need to do a little research on the web with the brand and see how they label their caps. For RIFA/EVOX which is what I used, their polypropylene caps are blue. Polycarbonate is yellow and polyester is grey. It's not easy to get the polypropylene caps in SLT. I was just there this evening, looking for caps for a crossfeed, could not find what I wanted. If you have to space to accomodate the Solen caps which bpribadi recommended, go for it, the brand is reputed to be good for their audio qualities.

bpribadi, thanks. Photography's my other hobby.

bpribadi, thanks for the tip re: polypropylene caps. Just a little more expensive than the plain normal polypropylene. But they look gigantic.

This is what I understand and what I do: 1. Film caps sound much better than electrolytic caps so film caps are normally use for the audio input. 2. Film caps comes in much smaller capacities than electrolytic so are not so suitable for the larger values required for power supply. However most amps do use a combination of both for the power supply. 3. Polypropylene is preferred over polyester film as they have better sound. 4. The polypropylene caps I buy from SLT are from $1 to $2.50 each. I don't bargain so you may get to pay less. 5. If you are making a CMOY, then the audio input jack's ground is connected to the volume pot and then from that to the virtual ground of the amp. Other amps may have different ways of connecting the input ground to the virtual ground plus a ground driver.

Goondu, if you are planning on two 9V batteries, I don't think so. I prefer the sound with two batteries which is why I am going thru all the possible ways to reduce the size to accomodate the two batteries and also the second opamp for the ground/virtual ground. Once my volume pots come in a few days time, I will case this amp and see how much space is left. I will post the pics then. Actually, with the new 100K R2 resistors broken in after a day, this CMOY doesn't sound so bad after all. The sense of the ambience of the music is back. Any way it sounds better. But restless tinkerers don't ever get satisfied do they.

I was asked to fax my hand-drawn schematic to a member but could not, so here is a small pic of it. Please pardon the horrible drawing. I will fax it when I can get access to a fax or if you prefer, send the full resolution pic to you. Sorry.

Realise there isn't a pic of the tin. This pic is of my second CMOY, since torn apart. Instead of a volume pot, I used a switch to set the gain. Not a good idea, the difference in volume was not as expected.

BTW bpribadi, you are building a PPA right? Did you buy the board from Tangent or rolling your own? Also have you tried your AD8610s yet? I got two of them as samples, wondering if they will give me two more. Thanks for your contribution, bpribadi.

Goondu, Got the red Hudson tins from Shell Select shops but you can also find them in supermart. I know that the NTUC minimart inside Terminal 1 Departure hall has 3 types of this tins, the yellow ones are nice but so far can't find them elsewhere. Oops, I was in the minimart yesterday and forgot to get more yellow tins, must wait for next trip. As per what bpribadi said, you need bigger caps and they have a hard time fitting into the tin with 2 batteries. I am waiting for my volume pot and then I will case this amp, just to see if the cap fit into the tin as I calculated it would. But then, I have been wrong many times.

bpribadi, thanks for the tip.

Hi, I got my opamps (OPA2134PA) from Federal in SLT and the other components from other shops. Why not just get cheap resistors etc and do one first just for the experience. And then go back and source for better components (eg 1% resistors and polypropylene caps) to build the one you want to keep. The OPA2134PA is a dual opamp and so it can amplify both Left and Right channel on the same chip.

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.

Wah, jtfoo, your amp looks nice leh, can share some naked pics or not? TIA.

Good job, bpribadi. Amazing stuff. I have to learn how to get some samples of AD8610 as I would like to build my cheapo version of the PPA. BTW - good photography too.

This is close up of board.

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.

I got two AD8620 from Tangent's site via PayPal. Feel like an idiot now that I read that you can get them free as samples. Cost me about S$60 for both including postage. On the other hand, Tangent had them mounted on the 8DIP adaptor board, I don't think I can do what Jason (is that correct?) did in the other thread. He's got real steady hands.

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.