Hi Uncle_Leon,
"As to DC blocking - it means simply putting a capacitor somewhere on the input signal wire, right?"
to avoid confusion, and possible error, put DC blocking caps in all individual amp. about the size , I didn't look at your schematic, perhaps somebody could suggest an appropriate size.
Hartono
"As to DC blocking - it means simply putting a capacitor somewhere on the input signal wire, right?"
to avoid confusion, and possible error, put DC blocking caps in all individual amp. about the size , I didn't look at your schematic, perhaps somebody could suggest an appropriate size.
Hartono
Uncle Leon, if you go to the Decibel Dungeon index page and download the Excel file and run it, you will find it can do a lot of useful hi-fi caluclations including telling you the frequency cut off of a resistor/cap (RC) filter.
So if you know the value of the resistor (signal input to ground), you can work out the value of the cap that you need. For bass you should aim for somewhere around 10hz and for your tweeter amp, I would say 1Khz although others may have their own ideas on that!
So if you know the value of the resistor (signal input to ground), you can work out the value of the cap that you need. For bass you should aim for somewhere around 10hz and for your tweeter amp, I would say 1Khz although others may have their own ideas on that!
uncle_leon said:
Skin effect: Tendency of an alternating electric current (AC) to distribute itself within a conductor so that the current density near the surface of the conductor is greater than that at its core.
The skin effect causes the effective resistance of the conductor to increase with the frequency of the current.
Nothing at all to do with "resonance".
Re: Snake Oil and case dampening
I have held a hose for sure. QUITE a difference between water flow and electric current flow. Water flowing through a hose is subject to a few more laws of physics also, such as inertia, gravity, friction.
Your hose analogy is extremely flawed.
Simaudio builds some of the finest amps in the world - also some of the most expensive. When you pay as much for an amp as someone would for a car, it should have all the bells and whistles to keep the audiophools content. Just add your favourite cutting board and brass pucks and the like.
mhouston said:
I have held a hose for sure. QUITE a difference between water flow and electric current flow. Water flowing through a hose is subject to a few more laws of physics also, such as inertia, gravity, friction.
Your hose analogy is extremely flawed.
Simaudio builds some of the finest amps in the world - also some of the most expensive. When you pay as much for an amp as someone would for a car, it should have all the bells and whistles to keep the audiophools content. Just add your favourite cutting board and brass pucks and the like.
MJL21193 said:
I think he's maybe saying resonance is was causes that current density distribution.
Regardless of cause. I don't think it matters one bit at anywhere near audio frequencies.
You can get (electrically) resonant effects in wire (not vibration) caused by the length of wire, and impedance changes at its ends. This is why you would use terminating resistors, or even active termination on a high speed digital line.
Knowing that a phenomenon exists is a far cry from actually saying that it applies to your situation, though. On the contrary, it's good to know about such things so that you know it's NOT applicable.
If you need your treble to be linear into the MHz range, it might matter, in which case you probably need a faster amp anyways.
If, like most humans, your hearing falls off around 20kHz or less, you can probably get away without worrying about any transmission line effects you'll encounter..
-Nick
Re: Effective upgrades
Electrons move through a conductor at the speed of light, slightly faster than a centimetre/second.
Here's an experiment: select a wire 3 metres long, thats 300 centimetres. Apply current to one end, and grasp the other end. See how long it takes before you feel the shock. 300 seconds?
In high school, I learned that electrons in a conductor move from the orbit of one atom to the next, not like a hoard of sperm swimming through a fallopian tube.
A lesson is basic electrical theory is needed here.
mhouston said:
Electrons move through a conductor at the speed of light, slightly faster than a centimetre/second.
Here's an experiment: select a wire 3 metres long, thats 300 centimetres. Apply current to one end, and grasp the other end. See how long it takes before you feel the shock. 300 seconds?
In high school, I learned that electrons in a conductor move from the orbit of one atom to the next, not like a hoard of sperm swimming through a fallopian tube.
A lesson is basic electrical theory is needed here.
Re: Re: Re: Re: Re: Effective upgrades
Done.
I've been following this thread with interest, as I've built a few LM4870 and LM3886 amps. I have noticed the sound to be very good and clean. They do not have the power supply flexibilty of a discrete, but for mid-power apps, they are amazing.
I'm not seeing much room for improvement.
BWRX said:
Let's stop discussing this and get back to discussing the most effective gainclone upgrades
Done.
I've been following this thread with interest, as I've built a few LM4870 and LM3886 amps. I have noticed the sound to be very good and clean. They do not have the power supply flexibilty of a discrete, but for mid-power apps, they are amazing.
I'm not seeing much room for improvement.
AndrewT - The schematic is here (click on user's guide): http://www.audiosector.com/lm3875.shtml
Hartono - you don't need to worry about confusing me, I know basic physics quite well, it's just the electronics-specific bits that I'm not entirely familiar with
As to DC blocking - what can possibly go wrong, if I do it only in one amp? I really don't want to detriment signal more than absolutely necessary.
I thought that on 'tweeter amp' inputs at least I could have some added benefit from use of DC blocking caps - they would act as a kind of passive crossover. Cut-off frequency of 1KHz or so should be ok, I think.
Now, I'm wondering what types of capacitors are generally recomended for such use? (Yeah, I want to do a mod and an upgrade in one sweep )
And does it matter in which section of the input wire is the cap soldered (closest/farthest possible to/from GC inputs)?
Hartono - you don't need to worry about confusing me, I know basic physics quite well, it's just the electronics-specific bits that I'm not entirely familiar with
As to DC blocking - what can possibly go wrong, if I do it only in one amp? I really don't want to detriment signal more than absolutely necessary.
I thought that on 'tweeter amp' inputs at least I could have some added benefit from use of DC blocking caps - they would act as a kind of passive crossover. Cut-off frequency of 1KHz or so should be ok, I think.
Now, I'm wondering what types of capacitors are generally recomended for such use? (Yeah, I want to do a mod and an upgrade in one sweep
)And does it matter in which section of the input wire is the cap soldered (closest/farthest possible to/from GC inputs)?
An ant can kill a giant
If an ant bites a giant on the toe and it gets infected and the giant does not treat the infection, then the toe could turn gangrene and eventually kill the giant. This same process happens inside anything carrying electrical current. Small resonance build and are held in an amp and this has a “killing” or adverse effect on the overall sound. It increase series impedance to the current which started it.
You must treat the resonance (infection) seriously to stop it spreading from source to preamp to power amp to speakers to floor and air to ear. Control it where it starts and it will not bring down your “giantly” good system.
I agree with BWRX lets talk Gainclones. But just for the record An electron moves at 1cm/s thorough a wire but it’s effect is felt at close to the speed of light. Only a photon in a vacuum approaches the speed of light. As an aside electrons travel 7 times faster through a valve (tube) than a transistor. I still like the sound of valves though.
If an ant bites a giant on the toe and it gets infected and the giant does not treat the infection, then the toe could turn gangrene and eventually kill the giant. This same process happens inside anything carrying electrical current. Small resonance build and are held in an amp and this has a “killing” or adverse effect on the overall sound. It increase series impedance to the current which started it.
You must treat the resonance (infection) seriously to stop it spreading from source to preamp to power amp to speakers to floor and air to ear. Control it where it starts and it will not bring down your “giantly” good system.
I agree with BWRX lets talk Gainclones. But just for the record An electron moves at 1cm/s thorough a wire but it’s effect is felt at close to the speed of light. Only a photon in a vacuum approaches the speed of light. As an aside electrons travel 7 times faster through a valve (tube) than a transistor. I still like the sound of valves though.
That's what we are doing. He's explaining what he thinks are the most effective upgrades, and some of us disagree.
It helps to know what's bunk.
I don't get the impression that uncle_leon is confused, except maybe by all this crazy talk of grounding sources.
If you do that, you better remember it whenever you plug in something new that you haven't tried before. The 100k resistor to ground idea is not a bad one, and might help with switching sources, and potentially keeping anything which isn't stable without a load in check.
If you really want to try all the mechanical damping, put your amplifier on the couch, and then put a couple of cinderblocks on top. That should lower your resonance to a few Hz. Test by bouncing it a little. Seriously.. If you don't hear a difference with that, the rest is silly.
If you're the type who thinks it should be coupled instead of decoupled, skip the couch.
I don't think there's a lot of "effective" upgrades to do, aside from things like biamping, maybe working on the power supply, etc. Real changes, not the same circuit with expensive parts..
I've never seen much as measurements go to show any difference, and have yet to see anyone tell the difference in double blind (abx) testing.
I still stand by the suggestion that you should do what you want to make it look nice on your shelf, make it work properly for the purpose, and consider it done. Instead of tweaking for things you can't even hear, look at your speakers/crossovers, or try an active biamp or something. Something you can really improve upon.
As much as people like to think their amplifiers are somehow unique, and sound different than everyone else's, for the most part, we're all just building basicaly what's in the appnote with some minor tweaks. Go ahead, build yourself a nice chassis. Something that looks awesome and keeps your amp nice and cool. Do it because you want it to look awesome. Don't expect it to sound much different though. It's still just a basic appnote chipamp. They sound good, but they'll sound just as good in a biscuit tin as they will in a fancy mass damped chassis, all gold plated and lowered.
-Nick
It helps to know what's bunk.
I don't get the impression that uncle_leon is confused, except maybe by all this crazy talk of grounding sources.
If you do that, you better remember it whenever you plug in something new that you haven't tried before. The 100k resistor to ground idea is not a bad one, and might help with switching sources, and potentially keeping anything which isn't stable without a load in check.
If you really want to try all the mechanical damping, put your amplifier on the couch, and then put a couple of cinderblocks on top. That should lower your resonance to a few Hz. Test by bouncing it a little. Seriously.. If you don't hear a difference with that, the rest is silly.
If you're the type who thinks it should be coupled instead of decoupled, skip the couch.
I don't think there's a lot of "effective" upgrades to do, aside from things like biamping, maybe working on the power supply, etc. Real changes, not the same circuit with expensive parts..
I've never seen much as measurements go to show any difference, and have yet to see anyone tell the difference in double blind (abx) testing.
I still stand by the suggestion that you should do what you want to make it look nice on your shelf, make it work properly for the purpose, and consider it done. Instead of tweaking for things you can't even hear, look at your speakers/crossovers, or try an active biamp or something. Something you can really improve upon.
As much as people like to think their amplifiers are somehow unique, and sound different than everyone else's, for the most part, we're all just building basicaly what's in the appnote with some minor tweaks. Go ahead, build yourself a nice chassis. Something that looks awesome and keeps your amp nice and cool. Do it because you want it to look awesome. Don't expect it to sound much different though. It's still just a basic appnote chipamp. They sound good, but they'll sound just as good in a biscuit tin as they will in a fancy mass damped chassis, all gold plated and lowered.
-Nick
Hum
I have seen a few variations on the100ohm ground resistor. One is the 10ohm ground resistor and another is either of these with a very small cap across it e.g. .033uf You may have to experiment if you have this problem I’ve never had enough hum (in my resonance controlled amps) to have to worry about it.
I have seen a few variations on the100ohm ground resistor. One is the 10ohm ground resistor and another is either of these with a very small cap across it e.g. .033uf You may have to experiment if you have this problem I’ve never had enough hum (in my resonance controlled amps) to have to worry about it.
uncle_leon said:AndrewT - The schematic is here (click on user's guide): http://www.audiosector.com/lm3875.shtml
I thought that on 'tweeter amp' inputs at least I could have some added benefit from use of DC blocking caps - they would act as a kind of passive crossover. Cut-off frequency of 1KHz or so should be ok, I think.
Now, I'm wondering what types of capacitors are generally recomended for such use? (Yeah, I want to do a mod and an upgrade in one sweep
And does it matter in which section of the input wire is the cap soldered (closest/farthest possible to/from GC inputs)?
I would suggest a film cap. General consensus is polypropylene is best of what's commonly available at a reasonable price, but I wouldn't get too hung up on it. If you have any polyester(mylar) caps in the right value, they'll work fine too.
I believe Nuuk posted a link before to one of his pages with a calculator on it. I would make sure the cap is big enough not to have any appreciable effect on the crossover frequency. 1kHz is probably just fine. I'd probably just grab the nearest filmcap that's anywhere in the ballpark and go with it.
I don't think there will be much difference dependent on where you put the cap.
-Nick
uncle_leon said:As to DC blocking - what can possibly go wrong, if I do it only in one amp? I really don't want to detriment signal more than absolutely necessary.
I thought that on 'tweeter amp' inputs at least I could have some added benefit from use of DC blocking caps - they would act as a kind of passive crossover. Cut-off frequency of 1KHz or so should be ok, I think.
Now, I'm wondering what types of capacitors are generally recomended for such use? (Yeah, I want to do a mod and an upgrade in one sweep
You don't really need DC blocking caps for two amps in parallel. I was supplying GC modules for those speakers (passive bi-amping): http://soundfusion.ca/Ariel.htm and everything worked fine without those caps.
As to the caps, BG N work well in coupling.
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