Questions regarding building the CMoy

[jtfoo 0]

Yoour latest creation is really compact... But with just 3 AA, you have only 3.6V. Might not be optimum, and also might not provide enough voltage swing especially for high impedance headphone.

[Q00 0]

jtfoo, i think thats xin's supermini...

[tropicalrips 0]

Yoour latest creation is really compact... But with just 3 AA, you have only 3.6V. Might not be optimum, and also might not provide enough voltage swing especially for high impedance headphone.

sorry not my its Xin's super-mini not my

i'm looking at his design to improve my own

i think it works with the AD823 cause of its low voltage requirement, my cha47 with 2 AD823 op-amps has already lasted longer then the cmoy with 1 OPA2132 on 1 9v batt

 

according to Xin this super-mini will last 75 hrs on the 3 AA , thats very impressive, i'll see how long my CHA47 last

 

anyone knows if the cha47 will work with AD823 as amp with LM6172 as buffer? will be getting my LM6172 after the holiday

Edited November 24, 2003 by tropicalrips

[N@Z 0]

The Supermini Xin uses might not fit your current Mini CMOY circuit board but if you can find the 4xAAA (battery) enclosure it could fit your board (laying sideways) & one 9v battery but you'll need to remove a bit of the internal trim

[jtfoo 0]

Yoour latest creation is really compact... But with just 3 AA, you have only 3.6V. Might not be optimum, and also might not provide enough voltage swing especially for high impedance headphone.

sorry not my its Xin's super-mini not my

i'm looking at his design to improve my own

i think it works with the AD823 cause of its low voltage requirement, my cha47 with 2 AD823 op-amps has already lasted longer then the cmoy with 1 OPA2132 on 1 9v batt

 

according to Xin this super-mini will last 75 hrs on the 3 AA , thats very impressive, i'll see how long my CHA47 last

 

anyone knows if the cha47 will work with AD823 as amp with LM6172 as buffer? will be getting my LM6172 after the holiday

Still I have my doubts with it's low voltage supply. It's not how long it'll last, but whether can it provide the voltage swing. But if you running it with mini earphone or low impedance and high sensitivity headphone, then probably you can get away with a decent sound. But if that's the case might as well run direct from your source which already provides similar voltage swing. This way as least you get direct path from source to earphone without the coloration of a mini headamp.

Edited November 25, 2003 by jtfoo

[tropicalrips 0]

i found the 4xAA case for it, its actually use for charging PDA, it also has a build-in on/off switch & its smaller then a mint box

it can fit 1x9v batt + 1xAA batt + the mini Cmoy

i'm thinking mini cha47, if 1 want to hav the AA & 9v together, should i connect them in series or parallel? the 9v is rechargable

 

i still don't know what rail-to-rail means, anyone can explain

[Firefox 0]

firefox, i'm using a weller 921ZX up to 450 degrees, don't think its not hot enough

I'm sorry. I meant to say higher wattage iron. Somewhere around 60W & above. Either that or use less solder to minimise contact time. Otherwise, you'd not have nice joints.

[jasonhanjk 0]

60W is too high. Sure must have a lot of skill to use such high wattage iron.

Normally 20-30 watt will do.

[tropicalrips 0]

got the LM6172IN today still testing it on the proto-board, this op-amp really is "cranky" got it to work using the drawing by tangent, but it sounds really bad with low impedance headphones lots of hissing & distortion, i got all the components execpt the 2.2uf C2 & 10pF C4 caps

 

made a plug with 2 43ohm resistors, this made most of the hissing go away. going to change the resistors to 50 ohm the plug has a strange effect on the sound...the low frequencies sound up-front, but the rest of the music sounds like they are behind. but i only use this on the cheapo headphones to simulate a high-impedance phones for testing

 

the bass with this op-amp is really heavy, more so then the OPA2132

 

also got the OPA2134PA today, they work in the cmoy & cha47 without any problems and they cost half the price of the 2132

 

guys, still don't know what rail-to-rail means

[Q00 0]

try head fi...got more diy guys there who might be able to help..

[augustineRS 0]

will volume pot and resistors at I/O jacks reduce hissing/volume/distortion?

Finally got noise coming out but is realli loud and alot of distortion.

R5 value is at 43 ohm...

Any help?

[tropicalrips 0]

do u mean hissing AugustineRS ? like its raining outside, i got that on my first cmoy too, are u using the same resistor values i posted?

 

try it with higher impedance headphones, those 16ohm headphones pick-up a lot of noise from the amp, or u can try what i hav above, solder 2 43-50 ohm resistors to the stereo plug to test if its the amp giving problems

 

the Cmoy works really well with high impedance phones like Sennheiser, which can't be driven properly with portable devices, but with cheap earphones

 

the R4 is connected to R5 (op-amp pin 1 > R5 > R4 > R3 > op-amp pin 2)

 

this forms the feedback loop i think the output is connected to 2 resistors - R4 & R5 before going into the op-amp

 

i didn't really hear any different with the volume pot thats why i left it out of my newer amps, but the resistors does make a difference, but thats the wrong way to go, will just end up with a cmoy with lots of components

 

 

[augustineRS 0]

I did follow the values by u.

the problem is these.

1. Think the gain is too much.bloody loud.

2.Alot distortion.Doubt is hissing.is like putting ur cans at maximum blast.

3.Think is pick up alot distortion from surrounding.

 

I'm using KOSS Plug and PX200.

i took out R1 now bcome single channel.

Arghhh...I really regret starting this thing.

When got ound damn happy, troubleshooting is no fun

[tropicalrips 0]

the koss plug sound on the cmoy i tried it, never try the PX200, i think its 32ohm rite? i also thought the gain is too high with my first Cmoy, but it end up being the headphones are too effecient (low impedance) so they pickup lots of noise.

 

u can try

4.7k for R3 which will giv u 10/4.7 + 1 = 3.1 gain

3k = 10/3 +1 = 4.3 gain

i'm using 2k so its a gain of 6

original design is gain 11

 

if the gain is too low, the high ohm cans will get distortion/cliping, they sound like the amps has not enough power

 

"took out R1" do u mean the voltage divider? which op-amp are u using?

if its too loud i guess the op-amp is still alive can still try

Edited November 26, 2003 by tropicalrips

[augustineRS 0]

PX200 is 32ohm.

back to soldering board.

mayb go the mini meet on friday to ask u guys directly and look at a properly fixed up cmoy.

my soldering is terrible