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jasonhanjk

Guide to fix up a Cmoy 2

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It might. shorter runs are always the best but very hard to do plus it depends on the case you will put the moy in. i'm sure some of the more advance builders here can add to this.

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sounds like what i got too.. i fixed it by using 2 x 9v instead of one. it works with a fresh 9v too, but then after the voltage drops, i get this "whee" sound.. isit just me and starushz ?

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I really wont be able to tell if it only yours till i build this verson on some of the other versions its one the two problems listed. then again you could just have a ground wire thats not soldered good enough.

 

also i have a question is there an alternative to using the LM6171 other than using caps. just wondering if there was another version or maybe another company made one close to LM6171.

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Sounds like RF. do you hear radio stations or any thing other than the music thats playing and this whee sound. other wise it might be oscillation.

I have made many cmoys and other amps and had never had RF picked up. Most of the problems are due to bad contact between some components or poor solder joint or not following instructions correctly.

 

One particular problem is the poor contact of the ground of the input plug and jack. And it can cause the squealing sound you mentioned, due to oscillation of the opamps. If you turn the plug in the jack and it causes this problem, then this is probably it.

 

Sorry, I can't explain better in tech terms cos I am not EE trained.

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Guest starushz

hmm..might be the LM6171 oscillating.Too bad no oscilscope to check. Will try with shorter wire today. Yup all cleaned up. No flux. laugh.gif

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Guest starushz

Guys one thing to ask. If we were to put the cmoy into a tin then the jacks must all be insulated right? If not hte Tin would be at the virtual gnd voltage. Or is it of not a concern?

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Guys one thing to ask. If we were to put the cmoy into a tin then the jacks must all be insulated right? If not hte Tin would be at the virtual gnd voltage. Or is it of not a concern?

One of the gurus earlier in this thread had say there's no problem with the output signal ground in contact with the input signal ground. I think the VG is also connected to the output signal ground under the LM6171 socket. So looks like not a problem.

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To replace LM6171, you must use single opamp IC, like OPA134. Too bad OPA134 does not have enough juice to drive virtual ground.

 

The battery I normally use are alkaline or NiMh. If your amp oscilate, try this.

Connect the input first then power up. Wait for 5 sec then insert the headphone jack.

 

Virtual ground circuit.

post-12-1115428457.gif

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LM6171=90mA

LM6181=100mA

OPA627=100mA

AD8610=65mA

AD8605=cannot use

OPA134=40mA

AD843=50mA

 

I just look through theis datasheet. The next few opamp that you might consider is 6181 and 627. No guarantee they will work though.

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BUF634P works as well biggrin.gif

i just tried it out, i *think* it sounds a little clearer laugh.gif

 

i'm still waiting for my AD8066.. then i'll do some comparison between the AD8066s and the OPA2134s headphone.gif

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can anyone explain the diff between the opa2227 and opa2228? from what i can see from the datasheets, opa2227 bandwidth is 8mhz, 2.3v/µs while the opa2228 is 33mhz, 10v/µs.

 

from my earlier tests with the opa2228's, i reported some bad distortion with the bass esp at higher volumes. i replaced the opa2228's with opa2227's and there is no distortion now. could the distortion be due to the bandwidth of 33mhz? the opa2134 is also 8mhz.

 

anyway, i'm really enjoying the amp with opa2227's. nice! headphone.gif

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