Questions regarding building the CMoy

[tropicalrips 0]

I remember seeing it at the Belden shop selling cables @ SLT 2nd floor.

thanks jason

for the volume pot, can i use other values? like 20k

found the Blue Alps volume pot in SLS, but its a 20k one, cost about $35

[jasonhanjk 0]

That is one high class son-of-the-b**** volume pot. Only recommend it for veli veli good amp like the PPA, etc.

[tropicalrips 0]

That is one high class son-of-the-b**** volume pot. Only recommend it for veli veli good amp like the PPA, etc.

i'm planning for Meta42/PPA now just looking at the parts

the tangent site says 50k for the meta, so will the 20k work? i remember seeing somewhere that anything from 10-50k will work for the Cmoy

[jasonhanjk 0]

It would work but I don't promise it will not add more hiss.

[augustineRS 0]

If we did make it into a sticky the thread has to be specifically detailing out the work & no other non related discussions.

Concerning insulation using the Mint tin. I believe only the base where the board is placed is required to be insulated. On JMT's (Altoids) amp he insulated the whole of the tin's base with black tape. On Tangent's MINT he didn't insulate it at all since the board was on it's side.

 

Thanks N@Z for the input bout the insulation.

 

I'm the sure the moderators are more than willing to help out aspiring DIYers in cliping the thread?

 

[jasonhanjk 0]

Maybe later we will have our own "DIY CMOY in Singapore"

[tropicalrips 0]

just added in 2 50ohm resistor on the Cmoy, they are on the out-put side just before the headphones.

 

i was hearing some soft hissing sound during the quiet parts of the music when used with low impedance Koss plug, kind of like an old record

 

the 50k did the trick, no more hiss with the plug

it also reduced the volume a little, had to go from mark 22 on the mp3 player to 30, sounds good with the porta-pro. hav to see if this reduced the batt life, the previous setup last abt 3-4hrs from the first charge

[jasonhanjk 0]

Battery maybe about the same, anyway. CONGRATS!!!

[kenshinz 0]

The 50 ohms is for the R5 ??.. that could be the problem for my cmoy hissing sound... when i using higher impedance headphones, the hissing sound is much lower, it gets louder when i'm using earphones

[tropicalrips 0]

The 50 ohms is for the R5 ??.. that could be the problem for my cmoy hissing sound... when i using higher  impedance headphones, the hissing sound is much lower, it gets louder when i'm using earphones

yes R5

 

i think the original design calls for a 40 or 47 ohm resistor, i bought the 50ohm to test something, thought they should work too

 

so kenshinz u change your resistor values yet?

my original hissing problem was not from the headphones, cause with this new board i didn't hear any hiss when used with the porta-pro, only the Plug can hear hissing as they are only 16ohm.

 

now even the cheapo earphones from the mp3 player sound like a sony

 

one more thing...can the Cmoy be bias into class A

Edited November 13, 2003 by tropicalrips

[kenshinz 0]

Ok will try adding in the R5 on my next board... have not done anything on the new board yet, i'm stuck in bed for the next few days, hurted my back in camp....sucks big time man

Edited November 14, 2003 by kenshinz

[jasonhanjk 0]

So you are stuck in your bed with your PC....

Edited November 14, 2003 by jasonhanjk

[huangyong 0]

Cmoy can be bias into class A but i didn't hear any difference. just connect a resistor between the V- and the out put will do. check this out in tangent's web page.

 

and bout volume pot. i think alps blue is overkill. Omeg is sucks, i tried it in three amps all failedl. dun know why?? the resistance will increase a lot for first turn then the rrest almost the same resistance.

 

soi think is it possible to use a lousy pot and a JFET circuit to control volume by biasing the jfet with different voltage and change their impedance....

is it linear??? possible???

[tropicalrips 0]

need to ask the electronics people about this

i'm electrical background just know how to follow the drawings

i'm also using a cheapo volume pot in my cmoy, the blues alps is to prepare for the bigger amps

update on my Cmoy:

change R5 to 43k

bought 2 Elna caps (25v 470uF size 40% bigger then others)

bought 2 0.47uF caps for the input

 

tested the caps on a proto-board, sounds good, more impact (just a little )

 

the 50k R5 had funny effects on different headphones (tried on new philps SBCHS900 it sounded very soft) 43k more optimal i think

[tropicalrips 0]

proto-board with new caps & blue alps