Guide to fix up a Cmoy 2

[klernie0521 0]

hi klernie, welcome to sgheadphone!

Thank you

 

My very first diy project will be charged to newbie experience hehehe.

Im glad that i still have 2 pcb's to work on another project and be sure to clean the flux before testing.

 

btw i have placed an order for another set of parts from RS and hopefully by next week it will be delivered.

I replaced the 0.1uf with 1.0uf as advised by 1bit and op amp LT1077 w/ TLE2426CLP (hope this is ok)

since Lm6171 is not available in RS Phils.

 

I love this forum because you help newbies like me with tips and assistance in assembling our very first diy headphone amp.

[heady 0]

klernie0521, if you use the TLE, it is not plugged into the ground op-amp socket. You need to substitute it for the two resistors which create the virtual ground. And you need to be really careful which of the 3 leads is positive, negative and the virtual ground. I have fried several with wrong connections.

 

[squalle 0]

abt the correct config, you guys ought to download the data sheet/spec sheet of each components, with exceptions of normal resistors, caps etc, which are simple in nature.

 

btw heady, where to get alcohol? been planning to get. is it possible to get those 99% type? I need it to clean my camera stuffs too

 

 

[1bit 0]

you're welcome klernie

always glad to help

 

using 1uF input caps will bring down the cutoff frequency to around 16 Hz, it'll be sufficient

but i was not really happy with 1 uF, i changed them to 3.3uF to give more bass, although i need to bend the lead to accomodate for the bigger size

here's a good article about input cap

 

if you wanna use tle2426clp, you'll need to modify the circuit a bit

refer to tle2426 and lm6171 datasheets

they have different pin configuration

 

tle2426clp is packaged in a 3 terminal packaging just like a transistor so it's still possible to solder it to the pcb with a bit of bending the lead here and there

 

refer to cmoy2 schematic below, in particular the ground channel

 

i think it's still possible to use tle2426clp, but you need to make the following modifications:

1. solder (or push in to the ic socket) the in pin of tle2426 to pin 7 on the pcb, common pin to pin 4, and out pin to pin 6

2. short pin 3 and 6 on the pcb (you can do this by connecting a wire between pin 2 and 3 btw)

3. you don't need R9 and R10 anymore, no need to solder them

 

[heady 0]

For lens cleaning, I recommend Kodak lens cleaning solution which is alcohol plus dunno what. I bought a bottle 20 years ago and I still have not used up half. Supposed to use only a little at a time or the lens get smeared.

 

For cleaning the PCB, I bought the cheap surgical alcohol or spirits they sell in pharmacy or medical hall. This is only 75% pure and not 99% pure but who cares, it works for me...

[squalle 0]

thanks heady

 

for the kodak solution, how much did u buy? hahaha if u can still remember.. 20 years ago LOL

btw, no1 trying the AD8397?

 

[heady 0]

for the kodak solution, how much did u buy? hahaha if u can still remember.. 20 years ago LOL

Man, you are so right. I can barely remember what I had for lunch!!

[klernie0521 0]

I have checked in farnell's website the Tle2426clp, 1bit and heady is correct it is the 3pin version.

I thought it is the 8pin socket. I have checked Rs phils and tle2426id is my only option.

Thanks guys for the heads up have to cancel my first oder and replace it with this one

 

If i will use TLE2426id, do i have to modify the circuit? or is it good as replacement for LM6171?

[heady 0]

klernie, hope the others correct me if I am wrong. The 8pin TLE won't work if you just drop it into the socket. At least that is my interpretation of its pinouts. If you got the 3pin variety, it will work by removing the two resistors for the virtual ground and carefully bending the TLE pins to fit into the 3 holes for positive, negative and virtual ground. In this case, you can omit the ground op-amp.

[1bit 0]

yes, i agree with heady

i hope i didn't confuse you with the long post i made

[Kube 0]

Actually, you can find flux cleaner. It's rather common in SLS. I found FLU fluxcleaner from Electrolube at Sunlight electronics next to Kaishin (or is it? Can't remember). Anyways, you spray this unto the board and wait a few seconds, observing that the flux gets dissolved. Then take a wet sponger and wipe. Repeat if necessery. I think the method should work with normal alcohol, no?

[squalle 0]

TLE2426 is just a rail splitter, which means that if you've got it, then it replaces the two resistors R9 and R10

 

LM6171's function is to lower the impedance of the return line, or the ground channel

 

when you've just built ur cmoy2 up, you can afford not to put the ground channel op-amp. just jumper pin 2 to pin 3. as what jason put in the 1st few posts.

 

I hope these help you klernie

 

Kube: I'll get the alcohol. got more use for it

the flux cleaner is simply too expensive for just a single function LOL

[1bit 0]

tle2426 is a buffered rail splitter, and it has a low output impedance of 7.5 mOhm (typ) according to its datasheet.

 

however as pointed out by tangent, tle2426 lacks the ability to supply higher current needs. its max output current is 80mA, in actual use it could be around 20 to 40 mA

 

lm6171 can output up to 135 mA.

 

klernie, if you want to use the original cmoy2 circuit with 2 resistors and a buffer ic, perhaps you can try ad817an as suggested by tangent. according to its datasheet it "drives unlimited capacitive load, 50 mA minimum output current". and the best thing is that it's available at rsphilippines

 

you can also try to find buf634p, it can drives up to a whooping 250 mA. unfortunately rsphilippines only have the 5 lead version (buf634t). if you can find the pdip version (buf634p), i think it is pin compatible for replacing lm6171 in your cmoy2.

 

another solution is to find lm6171 somewhere else. it looks like farnell has a distributor there. you can try to call them and ask if they can get you lm6171. i got my lm6171 from singapore's farnell anyway.

 

so in conclusion i think you can still use tle2426 and modify the circuit a bit, the output current might be enough for the cmoy2 right and left voltage gain set at 2 (the original cmoy2 settings with 10kohm R2 and R6) see calculation below

 

or the other easier option is to use 2 resistors and find a replacement opamp for buffer either ad817an, buf634p, or lm6171 (get from farnell)

 

addendum:

trying to calculate output current requirement, please give comments and/or correction for this

 

assume typical line output rating from audio source= 250 mV to 10kohm

(i get this number from sharp minidisc mt888 page, not sure if it is max or rms voltage)

 

cmoy2 voltage gain= 2

 

headphone= 16 ohm (worst case)

 

output current required= 250*2/16= 31.25 mA

if the voltage rating is in rms, max output current=31.25*sqrt(2)=44.2 mA

 

so tle2426 with 40 mA output current is at the borderline, it might be enough for some application but not optimal.

[linksix 0]

Quite new here, I was wondering, is there a simple straight forward list of all the parts/values for all the components for the board.

 

Also Does anyone know the difference of using ceramic or tantalum capacators in place of the (5? polyester) smaller Wima ones?

[squalle 0]

linksix: never put any tantalum or ceramic on the signal path

they will distort ur signal very badly

see here for the graphs: http://members.aol.com/sbench102/caps.html

best is of course get the paper+oil caps

 

for C3-C5, I guess you can use any caps that have low ESR (Equivalent Series Resistance, see here http://en.wikipedia.org/wiki/Equivalent_series_resistance). those caps (C3-C7) are there to smoothen the power supply into the op-amps. C1 and C2 are there to block DC offset from your source (see here http://tangentsoft.net/audio/input-cap.html).

 

for the parts, errmm which parts that you're having trouble with?