Hello,
I am in the processing of changing op-amps in my modified Marantz CD63.
I have in the past replaced the originals with AD827 and OPA2134 and have had no problems.
I recently tried LM6172 and bypassed the op-amp power inputs to ground with 2.2uf tantalum and .1uf tantalum. When I did this, the sound became very distorted and I lost my display. I removed the bypass caps and the LM6172 and put back the AD827 with no bypass caps and everything was good again including my display.
Just today I replaced op-amps with AD826 and I knew that I would have problems bypassing the power inputs to ground. So what I did was place the same two caps as above between V+ and V- on the op-amp. Upon testing the unit I had distorted sound and lost my display again.
Has anyone experienced this problem in this cd player or other cd players?.
What should I do? I know the AD826 has a very good PSSR so maybe I do not need to use the bypass caps.
Any and all input would be appreciated.
Thanks
KevinLee
T🙂
I am in the processing of changing op-amps in my modified Marantz CD63.
I have in the past replaced the originals with AD827 and OPA2134 and have had no problems.
I recently tried LM6172 and bypassed the op-amp power inputs to ground with 2.2uf tantalum and .1uf tantalum. When I did this, the sound became very distorted and I lost my display. I removed the bypass caps and the LM6172 and put back the AD827 with no bypass caps and everything was good again including my display.
Just today I replaced op-amps with AD826 and I knew that I would have problems bypassing the power inputs to ground. So what I did was place the same two caps as above between V+ and V- on the op-amp. Upon testing the unit I had distorted sound and lost my display again.
Has anyone experienced this problem in this cd player or other cd players?.
What should I do? I know the AD826 has a very good PSSR so maybe I do not need to use the bypass caps.
Any and all input would be appreciated.
Thanks
KevinLee
T🙂
If you have an oscilloscope I would check for oscillation because of the pretty heavy effects you describe.
Are the used caps new ? It could be that they are faulty and shorted the supplies. Try some normal new electrolytics to see if the faults occur again.
BTW The use of tantalum caps in audio is a curse. Nothing screws sound more up than they do. Use electrolytics or the fancier but more expensive BG or whatever as long as it isn't tantalum.
Always use bypass caps ( check datasheets of the opamps ) with opamps and the PSRR of the AD826 maybe good but that is not so relevant here. It is a high frequency device and has to be bypassed to prevent it from oscillation.
Are the used caps new ? It could be that they are faulty and shorted the supplies. Try some normal new electrolytics to see if the faults occur again.
BTW The use of tantalum caps in audio is a curse. Nothing screws sound more up than they do. Use electrolytics or the fancier but more expensive BG or whatever as long as it isn't tantalum.
Always use bypass caps ( check datasheets of the opamps ) with opamps and the PSRR of the AD826 maybe good but that is not so relevant here. It is a high frequency device and has to be bypassed to prevent it from oscillation.
Tantalum capacitors...playing games...
Hi kevinLee
Are you sure that the tantalum capacitors are not shorted???
Tantalum capacitors conected directely to a voltage surce(as the regulated power rails) have a tendency to short!
So cheek them!
Regards
Hi kevinLee
Are you sure that the tantalum capacitors are not shorted???
Tantalum capacitors conected directely to a voltage surce(as the regulated power rails) have a tendency to short!
So cheek them!
Regards
Hello Jean-Paul,
The bypass caps are new. They are not the same ones I used with the LM6172.
It was my understanding that tantalum were ok for bypassing as they are not directly in the signal path.
I am confused as when I replace the op-amps with AD827 or OPA2134/2604 and no bypassing, everthing seems ok.
I do not have a scope. What would you suggest as a next step knowing that I do not have a scope?.
Thanks
KevinLee
The bypass caps are new. They are not the same ones I used with the LM6172.
It was my understanding that tantalum were ok for bypassing as they are not directly in the signal path.
I am confused as when I replace the op-amps with AD827 or OPA2134/2604 and no bypassing, everthing seems ok.
I do not have a scope. What would you suggest as a next step knowing that I do not have a scope?.
Thanks
KevinLee
Hello Tube_Dude,
Thanks for the advice.
Do you mean to check and see if the cap has changed value?
The caps only have a 35volt rating, but the circuit is only 12-13 volts.
Any more suggestions would be appreciated.
KevinLee
Thanks for the advice.
Do you mean to check and see if the cap has changed value?
The caps only have a 35volt rating, but the circuit is only 12-13 volts.
Any more suggestions would be appreciated.
KevinLee
What more suggestions do you need ? Just grab your multimeter and check if they have resistance !
As Tube_Dude explained these inferior ( for audio ) caps have a tendency of shorting so there is a risk your tantalums are shorted...
If the short is intermittent connect the cap to a power supply with a Ampere meter in between and turn up the voltage. If it is shorted sometimes you will see it on you meter. Certainly if you reach the higher voltages ( say 30 V max. ).
For safety reasons: wear glasses/goggles. If your PSU has current limiting adjust it to a low Amperage or use a series resistor although the use of too big resistor can mask the fault.
As Tube_Dude explained these inferior ( for audio ) caps have a tendency of shorting so there is a risk your tantalums are shorted...
If the short is intermittent connect the cap to a power supply with a Ampere meter in between and turn up the voltage. If it is shorted sometimes you will see it on you meter. Certainly if you reach the higher voltages ( say 30 V max. ).
For safety reasons: wear glasses/goggles. If your PSU has current limiting adjust it to a low Amperage or use a series resistor although the use of too big resistor can mask the fault.
A Short track...
No...with your multimeter in low Ohms range see if they are not shorted.(near 0 ohms)...
Ok but if you conect them with the DC voltage on...the surge will break them!
This is your problem!!
No...with your multimeter in low Ohms range see if they are not shorted.(near 0 ohms)...
Ok but if you conect them with the DC voltage on...the surge will break them!
This is your problem!!
If electrolytic caps are old ( you never know how long were they stocked in the store ) it is good practice to format them by putting a low voltage on it with a 1 M resistor in series for 24 hours. It is better if they are flaky to buy others from another brand or from another store.
BTW I don't know your skills so don't take this as an insult please: do you know they are polarized ? Is there a possibility that you reversed polarity ?
BTW I don't know your skills so don't take this as an insult please: do you know they are polarized ? Is there a possibility that you reversed polarity ?
The solid true...
This is not true in the case of tantalum capacitors...they are solid capacitors...no dielectric...no chance to format them!!!
But it can help in the case of electrolitics...!!!
This is not true in the case of tantalum capacitors...they are solid capacitors...no dielectric...no chance to format them!!!
But it can help in the case of electrolitics...!!!
You got me there Jorge ! I edited the text straight away. But they have a dielectric otherwise they wouldn't be caps and there are wet tantalums as well....
But ... I wonder if dry tantalums don't suffer from oxides internally ( when not used for a long time ) but if you say so I believe you.
Had my share with the unreliability of tantalums a long time ago so my knowledge of them is a bit rusty...
But ... I wonder if dry tantalums don't suffer from oxides internally ( when not used for a long time ) but if you say so I believe you.
Had my share with the unreliability of tantalums a long time ago so my knowledge of them is a bit rusty...
I believe you are only partly addressing the oscillation with the LM6172. I could not decipher from your explanation whether you used BOTH decoupling capacitors (e.g., 1000uF with 0.1uF bypass) from V+ to ground and also decoupling capacitors (e.g., 1000uF with 0.1uF bypass)from V- to ground ALONG WITH a 1uF/50v low inductance stacked film capacitor across the V+ and V- on the chip. My understanding is that it will oscillate unless ALL THREE are done.
jean-paul,
Nothing anyone could say on here will offend me. I am very new to diy. I can solder and replace parts with the same value/type etc. but when it comes to modifying circuits I have limited experience. I gain most of my knowledge by reading posting on this site and by using the internet to see what other people have done.
That being said, it may be possible that I had the polarity reversed! I have removed the caps and checked their value with my capacitor meter and they are ok.
This next question will really show you how green I am. I am going to assume that when I bypass V+ to V- I will orientate the polarity of the cap the same way.
When I bypass V+ or V- to ground, do I connect the + side of cap to V+ and the - side of cap to ground and V- to the - side of cap with the + side of cap to ground for the other rail? Or do I have to use a bipolar cap?
Also, what values of caps have people found best for bypassing? I have some 10uf bipolar Nichicon muse electrolytics, would they be any good? I also have some .022 uf Wima MKS2, any good for this application? or are they better for coupling?
Thanks
KevinLee
Nothing anyone could say on here will offend me. I am very new to diy. I can solder and replace parts with the same value/type etc. but when it comes to modifying circuits I have limited experience. I gain most of my knowledge by reading posting on this site and by using the internet to see what other people have done.
That being said, it may be possible that I had the polarity reversed! I have removed the caps and checked their value with my capacitor meter and they are ok.
This next question will really show you how green I am. I am going to assume that when I bypass V+ to V- I will orientate the polarity of the cap the same way.
When I bypass V+ or V- to ground, do I connect the + side of cap to V+ and the - side of cap to ground and V- to the - side of cap with the + side of cap to ground for the other rail? Or do I have to use a bipolar cap?
Also, what values of caps have people found best for bypassing? I have some 10uf bipolar Nichicon muse electrolytics, would they be any good? I also have some .022 uf Wima MKS2, any good for this application? or are they better for coupling?
Thanks
KevinLee
The rusty tantalums....
Yes ...they suffer!
With time they form a crystalline tantalum oxide that eventually breaks through the amorphous oxid layer ...and because the newly formed oxide has a very low especific resistence...a current flow is originated which results in a short circuit...!
Yes ...they suffer!
With time they form a crystalline tantalum oxide that eventually breaks through the amorphous oxid layer ...and because the newly formed oxide has a very low especific resistence...a current flow is originated which results in a short circuit...!
Correct.
10 uF will do in most cases. Please consult the datasheets of the new opamps and check the original values too when in doubt. In my experience 10 uF is sufficient when placed close at the supply pins. Nichicon MUSE has a very good reputation but I never used them so I can't comment on that. They sure will be better than tantalum and normal electrolytics.
The 22 nF MKS are too small, 100 nF is better but an electrolytic is preferred here. Check datasheets of your opamps as they sometimes give other information.
Anecdote: I just modified a DAC that had originally 2 x 100 nF at the left output opamp and 2 x 100 uF at the right opamp. There was a difference in sound of the channels that disappeared after changing all 4 to 10 uF BG.
Won't formatting them as described don't help ??
Thanks jean-paul,
You have been a teacher today and Ihave learned!
One final question,
Will I be better off using the 2.2uf & .1uf tantalums for this task or should I use my 10uf bipolar Nichicon muse & a .022 Wima MKS?
Thanks
KevinLee
You have been a teacher today and Ihave learned!
One final question,
Will I be better off using the 2.2uf & .1uf tantalums for this task or should I use my 10uf bipolar Nichicon muse & a .022 Wima MKS?
Thanks
KevinLee
Mmm I am not sure if I like being named a teacher 😉
Anyhow, skip tantalum for ever. Tantalum resistors are very good so please don't think the material itself is evil.
Oh, I just understood that the MUSE are bipolar. Most bipolars are 2 caps in series and thus their ESR ( resistance ) is higher.
This story is different for some Black Gate bipolar types !
At this spot that's something that will not as good results as we want.
Just use good electrolytics as they are OK on this spot. Normal ones can be bypassed with 100 nF film caps although I never do that anymore. MKP is preferred and MKT is what you probably will find in the store.
Better is to find real good electrolytics as BG or Panasonic FC.
Anyhow, skip tantalum for ever. Tantalum resistors are very good so please don't think the material itself is evil.
Oh, I just understood that the MUSE are bipolar. Most bipolars are 2 caps in series and thus their ESR ( resistance ) is higher.
This story is different for some Black Gate bipolar types !
At this spot that's something that will not as good results as we want.
Just use good electrolytics as they are OK on this spot. Normal ones can be bypassed with 100 nF film caps although I never do that anymore. MKP is preferred and MKT is what you probably will find in the store.
Better is to find real good electrolytics as BG or Panasonic FC.
Mmm I am not sure if I like being named a teacher 😉
Anyhow, skip tantalum for ever. Tantalum resistors are very good so please don't think the material itself is evil.
Oh, I just understood that the MUSE you have are bipolar. Most bipolars are 2 caps in series and thus their ESR ( resistance ) is higher.This story is different for some Black Gate bipolar types !
At this spot that's something that will not give as good results as we want. A too low ESR when using switched PSU caps may not work out either at this spot.
Just use good brand electrolytics ( BCcomponents, Nichicon, Elna, United Chemicon etc. ) as they are OK on this spot. Normal ones can be bypassed with 100 nF film caps although I never do that anymore. MKP is preferred and MKT is what you probably will find in the store. Even better is the use of only quality electrolytics without bypass like polarized MUSE's, Silmic, Cerafine, Panasonic FC etc.
As a sidenote: The sonical quality of normal caps IMO rises from left to right:
Ceramic - MKT/MKS - MKC - MKP - Polystyrene/Styrofoam - exotics/unobtainables as PTFE/Silver Mica's etc.
Ceramic is very useful for RF and the newer stacked types are very usable as decoupling caps in audio so time changes things. MKC and Polystyrene are only found NOS ( new old stock ) as they are not produced anymore. I omitted Paper In Oil as they are practically only used in tube-amps. Better technical properties of cap doesn't automatically imply they will sound better also !!!
I think a lot of people won't agree with this but I don't care. You can find excellent threads with different opinions on the bypassing and cap subject if you use the search function on this forum.
Better is to find real good electrolytics as BG or Panasonic FC if you have the money.
Anyhow, skip tantalum for ever. Tantalum resistors are very good so please don't think the material itself is evil.
Oh, I just understood that the MUSE you have are bipolar. Most bipolars are 2 caps in series and thus their ESR ( resistance ) is higher.This story is different for some Black Gate bipolar types !
At this spot that's something that will not give as good results as we want. A too low ESR when using switched PSU caps may not work out either at this spot.
Just use good brand electrolytics ( BCcomponents, Nichicon, Elna, United Chemicon etc. ) as they are OK on this spot. Normal ones can be bypassed with 100 nF film caps although I never do that anymore. MKP is preferred and MKT is what you probably will find in the store. Even better is the use of only quality electrolytics without bypass like polarized MUSE's, Silmic, Cerafine, Panasonic FC etc.
As a sidenote: The sonical quality of normal caps IMO rises from left to right:
Ceramic - MKT/MKS - MKC - MKP - Polystyrene/Styrofoam - exotics/unobtainables as PTFE/Silver Mica's etc.
Ceramic is very useful for RF and the newer stacked types are very usable as decoupling caps in audio so time changes things. MKC and Polystyrene are only found NOS ( new old stock ) as they are not produced anymore. I omitted Paper In Oil as they are practically only used in tube-amps. Better technical properties of cap doesn't automatically imply they will sound better also !!!
I think a lot of people won't agree with this but I don't care. You can find excellent threads with different opinions on the bypassing and cap subject if you use the search function on this forum.
Better is to find real good electrolytics as BG or Panasonic FC if you have the money.
What a formation!!
Formating????...Sorry!!..But what i was descriving ,was the end of the life of a tantalum capacitor ,sometimes in a early stage of its service life...especially in dinamic aplications...
So not formation...but dead!!!
Formating????...Sorry!!..But what i was descriving ,was the end of the life of a tantalum capacitor ,sometimes in a early stage of its service life...especially in dinamic aplications...
So not formation...but dead!!!
jean-paul,
I did not mean anything bad by calling you a teacher. Only thanks for your help.
I have a few hundred polystyrene caps, but the largest value I have is .01uf. Is this ok for bypassing?
Also, are all ceramics bad? Where would COG/NPO ceramics fit into your left to right flow chart?
KevinLee
I did not mean anything bad by calling you a teacher. Only thanks for your help.
I have a few hundred polystyrene caps, but the largest value I have is .01uf. Is this ok for bypassing?
Also, are all ceramics bad? Where would COG/NPO ceramics fit into your left to right flow chart?
KevinLee
The chiken before the egg...
H kevin...
I recomend you read some books about electronics...
Sometimes can be dangerous to tamper with things .... without knowing how a capacitor is conected to a circuit...or other basic things...
If the maker of your CD hasn't done a good job procteting the power supply from shorts...now you will have a dead CD in your hands...
Practice without theory is not to good...
Theory without pratice...the same..
Add the two...and you are a winner!! 😉
Imagine that people begin to drive in the streets...before some driving lessons...
H kevin...
I recomend you read some books about electronics...
Sometimes can be dangerous to tamper with things .... without knowing how a capacitor is conected to a circuit...or other basic things...
If the maker of your CD hasn't done a good job procteting the power supply from shorts...now you will have a dead CD in your hands...
Practice without theory is not to good...
Theory without pratice...the same..
Add the two...and you are a winner!! 😉
Imagine that people begin to drive in the streets...before some driving lessons...
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