OK, I would like to set up a hypothesis after double Jameson.
1) the generally accepted method: the small resistor in series with large elco, both shunted by high quality small cap. The power supply output impedance decreases with frequency, then becomes constant to resistor value and then decreases again as the impedance of small cap.
2) Carlos method: the small resistor in series with small cap. The power supply output impedance decreases with frequency up to dozen milliOhms, (for 10000uF that minimum is within 1-10 kHz) then started to increase with large cap internal inductance and then becomes constant to resistor value when the impedance of small cap is negligible.
LM3886 has high value of PSRR but only for low frequencies. It decreases with frequency starting from kHz, and for one power supply rail much earlier. To compensate this decrease in CMRR in audio frequency range the power supply impedance should be very low (regulated supply) or should decreased with frequency (Carlos method)
LM3886 is extremely sensitive to power supply rail inductance so the extra small caps are marginal.
Cheers, Carlos
By the way one can simply poke oscilloscope probe into the power supply, observe and compare the garbage for different methods. These DIYers who trust their ears could listen the noise on the supply rail by the extra ac coupled amplifier.
1) the generally accepted method: the small resistor in series with large elco, both shunted by high quality small cap. The power supply output impedance decreases with frequency, then becomes constant to resistor value and then decreases again as the impedance of small cap.
2) Carlos method: the small resistor in series with small cap. The power supply output impedance decreases with frequency up to dozen milliOhms, (for 10000uF that minimum is within 1-10 kHz) then started to increase with large cap internal inductance and then becomes constant to resistor value when the impedance of small cap is negligible.
LM3886 has high value of PSRR but only for low frequencies. It decreases with frequency starting from kHz, and for one power supply rail much earlier. To compensate this decrease in CMRR in audio frequency range the power supply impedance should be very low (regulated supply) or should decreased with frequency (Carlos method)
LM3886 is extremely sensitive to power supply rail inductance so the extra small caps are marginal.
Cheers, Carlos
By the way one can simply poke oscilloscope probe into the power supply, observe and compare the garbage for different methods. These DIYers who trust their ears could listen the noise on the supply rail by the extra ac coupled amplifier.
dimitri said:OK, I would like to set up a hypothesis after double Jameson.
Cheers, Carlos
Just by coincidence, I'm drinkin' a pure malt.
While finishing the montruous unregulated PSU for this amp.
528VA (2x22V at 12A) toroid.
Big caps.
Snubbed.
Small caps on the chips, of course.
This is a christmas gift for someone.
I'll make another one for me after this.
BTW, it's not an LM chip.
And it's not a germanium transistor.
Re: Re: Re: Re: Re: Re: Re: Re: Re: Chip amplifiers
Yes, belive you are quite right.
however, this puppy still needs a chassi, and a preamp, so optimalisations are not qite first priority as of yet.
It lays on my Kenwood casettplayer, besides my monitor and plays music, atatched to a old pentium2 heatsink. not ideal at all, but it does play music, so im content for the moment. a dangerous thing to be, content, but i'l probably be sic of it lying in a pile by next week, and do something about it then.
cheers!
gmarsh said:
Yes, belive you are quite right.
however, this puppy still needs a chassi, and a preamp, so optimalisations are not qite first priority as of yet.
It lays on my Kenwood casettplayer, besides my monitor and plays music, atatched to a old pentium2 heatsink. not ideal at all, but it does play music, so im content for the moment. a dangerous thing to be, content, but i'l probably be sic of it lying in a pile by next week, and do something about it then.
cheers!
carlosfm said:
if we "posit" that some procedure is better in molecular biology, or finance, to gain credibility of the peer review group we have to be able defend the hypothesis, state the assumptions, cite data and collection methodology, and then use old fashioned linear-sequential logic and a bit of guile to better those who hadn't thought up the idea in the first place.
it's difficult to take seriously the statement "I've tested that." when when there are no results, even ABX, (flawed as it may be) with which to compare.
you state that a regulated GS sounds better than a non-regulated version to which I ask: "why?", not to be nasty or hypercritical but small curiousity demands to understand.
Quite frankly, I looked at Peranders circuit, liked it, and would only use a through-hole device for the decoupling resistor/inductor, only owing to the fact that I have millions of these resistors and have to use them up.
...so I ask, if an LM38XX or OPA54X can't deliver the SPL's -- where is all the energy going, and why?
jackinnj said:
How do you know?
Also, if you have a better way of talking english (I'm sure you have), please post for me.
We can talk portuguese, why not?
Sometimes you guys forget that we (non-native english) don't express ourselves as well as you do. And that brings misunderstandings.
I'm sorry if I don't talk the way you like.
But yes, I've tested that.
jackinnj said:
Seriously?
Buy it, build it, listen to it.
And then run away from LM chips, or chipamps in general.
jackinnj said:
Is music only SPL?
An amp that doesn't drive a pair of speakers properly can be detected aven at low volume.
Have you experienced that?
Have you listened to a background instrument to completely disappear when the others come in?
Have you experienced untight bass spoiling all the rest at low volumes?
It can be subtle.
I'm not talking GCs now, I'm talking amps in general.
EDIT: I didn't say these chips can's deliver the SPLs, I just said it can't with low capacitance.
And it can't sound good with high capacitance, even paralleling caps.
I've told you the solution. Try it.
Upupa Epops said:to Carlos : I wash my hands like Pilatus Pontius, my friend
Great, Mr. Experienced Listener.
Take a serious listen to your LM4780 amp with those 22,000uf caps on the PSU.
I know, that's why you say that chip-amps are for kids.
Put a snubber there and cry.
Also, check your schematic again.
For C11 and C15 you recommend 1uf/63v or 47uf/16v.
Very scientific.
Netlist said:
Carlos
Please explain. I don't understand what you want to tell me. Peranders is the owner/starter of this thread.
/Hugo
This file contains a printscreen of the Chipamp forum right now.
Thread starter: carlosfm.
I didn't start this thread.
It was P-A.
I repeat for the third time: Fair play?
Cheating.
peranders said:
Jesus!
Just saw this pearl.
P-A, I had a low capacitance LM3886 amp, after discarding a similar LM3875.
Of course the LM3886 is better and I've been defending people to use it for a long time.
You are not being original. In fact, it seams that you keep repeating my old posts.
But this post of yours is absurd, nonsense, trying to put absurd words in my mouth.
With the low capacitance PSU the LM3886 amp was not enough for my speakers, and they are 8 ohms.
I don't give up so easily.
And I'm very picky, I like and recognize quality when I hear it, I'm not easily satisfied.
I tried every combination you can imagine for using more capacitance.
Bad sound.
Regulated PSU. Oh yes.
Unregulated high capacitance PSU, with snubbers. Oh yes.
How this thread started
roibm, now banned, started a thread about building my SMD Gainclone. Of some reason the thread came to be about something totally different than actually building. Therefore I have made split.
The thing is that some people here claims the LM3875/3886 is plain garbage or very near it.
My claim is that Lm3886 is the entrance for many DIY'ers to the DIY world and you should not look down on those newbeginners. It's a good start to achieve success with good odds.
carlosfm did make the first post here and this post is written afterwards as a explanation.
roibm, now banned, started a thread about building my SMD Gainclone. Of some reason the thread came to be about something totally different than actually building. Therefore I have made split.
The thing is that some people here claims the LM3875/3886 is plain garbage or very near it.
My claim is that Lm3886 is the entrance for many DIY'ers to the DIY world and you should not look down on those newbeginners. It's a good start to achieve success with good odds.
carlosfm did make the first post here and this post is written afterwards as a explanation.
Carlos! I have no words! i'm truly stunned! truly!!
this snubber is actually what makes night and day with my amp, almos cannot belive it myself, i almost sont want to, thinking that the answer was so damn simple! four caps and 4 resistors!
The details suddenly poped up, the warmth from when running 2200+470uf appeared again, and with a vengance!
STUNNED!! the music sounds soo beautiful!! and thats Celtic Bluegrass! The McKrells - Hit the ground Running.. and on MP3!! not the kind of music i would usally listen to, but damn!!! i have no words.. can not recomend this enough!! DAMN!
THANK YOU!!
this snubber is actually what makes night and day with my amp, almos cannot belive it myself, i almost sont want to, thinking that the answer was so damn simple! four caps and 4 resistors!
The details suddenly poped up, the warmth from when running 2200+470uf appeared again, and with a vengance!
STUNNED!! the music sounds soo beautiful!! and thats Celtic Bluegrass! The McKrells - Hit the ground Running.. and on MP3!! not the kind of music i would usally listen to, but damn!!! i have no words.. can not recomend this enough!! DAMN!
THANK YOU!!
Trying to get back on what might slightly ressemble a topic...
Carlos:
Do you have any suggestions on how to easily implement the additional components needed to increase the capacitance of the PSU and include the snubber on the BrianGT/PD gainclone PCBs or Perander's PCBs? This would be very useful to me as I'm going to be starting a 6 channel gainclone project very soon (using BrianGT/PD boards) and I'd like to be able to try this technique. Also anyone (including Perander himself) who has the Perander boards could give it a shot as well...
Has anyone applied this method to either of these boards?
Carlos:
Do you have any suggestions on how to easily implement the additional components needed to increase the capacitance of the PSU and include the snubber on the BrianGT/PD gainclone PCBs or Perander's PCBs? This would be very useful to me as I'm going to be starting a 6 channel gainclone project very soon (using BrianGT/PD boards) and I'd like to be able to try this technique. Also anyone (including Perander himself) who has the Perander boards could give it a shot as well...
Has anyone applied this method to either of these boards?
m0tion said:
Check Peranders' boards here, with the improvements I recommended to roibm:
http://gainclone.com/phpBB2/viewtopic.php?t=546
On pic number 3 you can see the snubbers across the big caps.
Easy...
I think that this entire thing has turned into a ego contest and it doesn't need to be. Look at what we are presented with...
We have two individuals on this forum who have taken the time and initiative to make some PCB layouts, have them produced, and offer them to the public. Both BrianGT/PD and Perander should be complimented for this.
In that same spirit we have another individual who has taken the time and initiative to tackle one of the known problems with chipamps and he feels that he's found a solution. He's also been kind enough to share his solution, present schematics, and answer questions and for that Carlos should be complimented.
I think the problem we're facing is that the two PCBs that are available don't incorporate Carlos's suggestions and to me this is not a problem at all. Carlos says that without his modifications the amps don't perform as they should, maybe he is right, maybe not, that is for debate. Even if he is right and these amps would be better with his modification this does not invalidate what BrianGT/PD and Peranders have done. On the contrary I plan to use some of these premade boards in order to impliment and test Carlos's suggestions.
THIS IS PROGRESS!
We should test given the resources currently available and then discuss. No more shouting about egos! If Carlos is right these changes can still be applied to existing boards, they are still valuable! And if Carlos is wrong all you've lost is a few dollars worth of parts!
We have two individuals on this forum who have taken the time and initiative to make some PCB layouts, have them produced, and offer them to the public. Both BrianGT/PD and Perander should be complimented for this.
In that same spirit we have another individual who has taken the time and initiative to tackle one of the known problems with chipamps and he feels that he's found a solution. He's also been kind enough to share his solution, present schematics, and answer questions and for that Carlos should be complimented.
I think the problem we're facing is that the two PCBs that are available don't incorporate Carlos's suggestions and to me this is not a problem at all. Carlos says that without his modifications the amps don't perform as they should, maybe he is right, maybe not, that is for debate. Even if he is right and these amps would be better with his modification this does not invalidate what BrianGT/PD and Peranders have done. On the contrary I plan to use some of these premade boards in order to impliment and test Carlos's suggestions.
THIS IS PROGRESS!
We should test given the resources currently available and then discuss. No more shouting about egos! If Carlos is right these changes can still be applied to existing boards, they are still valuable! And if Carlos is wrong all you've lost is a few dollars worth of parts!
m0tion said:
Thanks, but at what cost?
Two banned members and 3 sin-binned.
m0tion said:
They will have to talk to me gently.
Very gently.
m0tion said:
Yes, that's my way of doing things.
You don't need to spend big $$$$ on big and expensive BGs.
If you think I'm mad, forget all this, be happy with those amps as they are.
But you would be dumb if you don't try it. What does it cost?
Carlos, please, send me a hand scratch or inform were i can find
The supply schematics you are defending.
I could see that some excesses in supply cause problems in some amplifiers.
Also could see the "magic" of some small cap in parallel with the supply electrolic condensers.
Things you defend make some sense to me, i would be happy to hear them in some circuits i already have.
I know, the case is LM3875 and LM3886 , but this can be applied in others too.
A long time i see you researching those amplifiers.
I have to thank you for that.
regards,
nanabrother@yahoo.com
Carlos
The supply schematics you are defending.
I could see that some excesses in supply cause problems in some amplifiers.
Also could see the "magic" of some small cap in parallel with the supply electrolic condensers.
Things you defend make some sense to me, i would be happy to hear them in some circuits i already have.
I know, the case is LM3875 and LM3886 , but this can be applied in others too.
A long time i see you researching those amplifiers.
I have to thank you for that.
regards,
nanabrother@yahoo.com
Carlos
Re: Carlos, please, send me a hand scratch or inform were i can find
It's here:
http://www.diyaudio.com/forums/showthread.php?postid=534018#post534018
Try it and post your findings on that thread.
It can, it must, and it should work well everywhere.
destroyer X said:
It's here:
http://www.diyaudio.com/forums/showthread.php?postid=534018#post534018
Try it and post your findings on that thread.
destroyer X said:
It can, it must, and it should work well everywhere.
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