CMoy amp - troubleshooting - Page 4

infinitesymph · 16th November 2007, 07:48 PM

I was reading through Tangent's guide for working with cranky op-amps, and he mentioned that it was possible to use a 1 uF - 10 uF tantalum capacitor from rail to rail. Would this work just as well as the two-capacitor solution (and is the 16V rating enough for a potential 18V power supply)?

Since I'd solved the problem on the first amp, I built a second one last night, so I'm considering trying something different.

infinitesymph · 17th November 2007, 09:07 AM

I'll answer my own question.

I purchased a 10 uF tantalum capacitor and connected it rail to rail, making sure to connect positive to V+ and negative to V-. It didn't decrease distortion; there was no audible change after installing it.

I used another pack of cheap Radio Shack ceramics and they worked perfectly. The heat shrink suggestion worked well too, so thank you for that, Nordic. I used my soldering iron to shrink it, which didn't look or smell so great, but looks were secondary to function in this case.

monkey700 · 3rd August 2008, 06:17 PM

I've been having some distortion problems with a Cmoy I just built. It actually sounds more like the amp is clipping. I've built one before with no problem and I use it all the time. This time I decided to use a different OPAMP and add output caps in the place of R5. The caps I used are 4.7 uF Tantalum Caps. I though this might have been the problem but i removed them and it acts the same. I also have dual micromini Pots to adjust the channels seperatly. The OPAMP i am using is the TI NE5532P. The Cmoy powersup and you can barely hear the music except when it hits certain notes the phones pop very loudly. Any insight?

Pars · 3rd August 2008, 07:52 PM

Why on earth would you use output caps on this? And why tantalum, which are god awful anyhow but really bad for coupling caps. And what are you using the dual micromini pots for? Schematic?

monkey700 · 3rd August 2008, 08:19 PM

The micro minis are on the input in place of the pad switch. I'm using them so i can adjust the left and right channels individually, I have them mounted inside the case so that I can set my levels then leave them set and use my audio device to adjust the actual volume.(I think it pointless to have an external knob that you have to constantly adjust along with the volume from your audio device) The output caps were to act as a filter and block the DC offset. The schematic I am using is here

http://tangentsoft.net/audio/cmoy-tu...angent-sch.pdf

I just replaced the R5 value with the Caps(which I have now removed) and put the pots on the input.

Minion · 4th August 2008, 10:01 PM

Looking at the schematic it doesn"t give clear indication on which ground points go to VR and which go to actual ground (-9v)....

In the schematic only R2 goes to VR ,The ground on the Pot and R3 go to actual ground (-9v)....

If you connected all VR and ground points to the same Point it could cause problems and could be the cause of the problem you are haveing....

Cheers

monkey700 · 5th August 2008, 03:56 AM

After doing a lot of searching I found some info about batches of counterfeit/fake opamps. The batch of op amps i got came off ebay from somewhere in hong kong. I went to radio shack and picked up some generic op amp and they work beautifully! Another side note, I bumped the output caps up to 220uf electrolytics. I've now ordered some burr brown 2227s from digi-key. No more ebayed opamps from now on.

3rd August 2008, 06:17 PM	#33
monkey700 diyAudio Member Join Date: Aug 2008	Distortion I've been having some distortion problems with a Cmoy I just built. It actually sounds more like the amp is clipping. I've built one before with no problem and I use it all the time. This time I decided to use a different OPAMP and add output caps in the place of R5. The caps I used are 4.7 uF Tantalum Caps. I though this might have been the problem but i removed them and it acts the same. I also have dual micromini Pots to adjust the channels seperatly. The OPAMP i am using is the TI NE5532P. The Cmoy powersup and you can barely hear the music except when it hits certain notes the phones pop very loudly. Any insight?

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16th November 2007, 07:48 PM	#31
infinitesymph diyAudio Member Join Date: May 2006	I was reading through Tangent's guide for working with cranky op-amps, and he mentioned that it was possible to use a 1 uF - 10 uF tantalum capacitor from rail to rail. Would this work just as well as the two-capacitor solution (and is the 16V rating enough for a potential 18V power supply)? Since I'd solved the problem on the first amp, I built a second one last night, so I'm considering trying something different.

17th November 2007, 09:07 AM	#32
infinitesymph diyAudio Member Join Date: May 2006	I'll answer my own question. I purchased a 10 uF tantalum capacitor and connected it rail to rail, making sure to connect positive to V+ and negative to V-. It didn't decrease distortion; there was no audible change after installing it. I used another pack of cheap Radio Shack ceramics and they worked perfectly. The heat shrink suggestion worked well too, so thank you for that, Nordic. I used my soldering iron to shrink it, which didn't look or smell so great, but looks were secondary to function in this case.

3rd August 2008, 07:52 PM	#34
Pars diyAudio Member Join Date: Jan 2004 Location: Chicago	Why on earth would you use output caps on this? And why tantalum, which are god awful anyhow but really bad for coupling caps. And what are you using the dual micromini pots for? Schematic?

3rd August 2008, 08:19 PM	#35
monkey700 diyAudio Member Join Date: Aug 2008	The micro minis are on the input in place of the pad switch. I'm using them so i can adjust the left and right channels individually, I have them mounted inside the case so that I can set my levels then leave them set and use my audio device to adjust the actual volume.(I think it pointless to have an external knob that you have to constantly adjust along with the volume from your audio device) The output caps were to act as a filter and block the DC offset. The schematic I am using is here http://tangentsoft.net/audio/cmoy-tu...angent-sch.pdf I just replaced the R5 value with the Caps(which I have now removed) and put the pots on the input.

4th August 2008, 10:01 PM	#36
Minion diyAudio Member Join Date: May 2006	Looking at the schematic it doesn"t give clear indication on which ground points go to VR and which go to actual ground (-9v).... In the schematic only R2 goes to VR ,The ground on the Pot and R3 go to actual ground (-9v).... If you connected all VR and ground points to the same Point it could cause problems and could be the cause of the problem you are haveing.... Cheers

5th August 2008, 03:56 AM	#37
monkey700 diyAudio Member Join Date: Aug 2008	After doing a lot of searching I found some info about batches of counterfeit/fake opamps. The batch of op amps i got came off ebay from somewhere in hong kong. I went to radio shack and picked up some generic op amp and they work beautifully! Another side note, I bumped the output caps up to 220uf electrolytics. I've now ordered some burr brown 2227s from digi-key. No more ebayed opamps from now on.

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