.1uf cap twix pos/neg speaker posts

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I see that the T-amp and other amps have a .1uf cap twix the neg/pos speaker terminals.

Is this a shelving circuit? I've looked in side my solid state amps and I don't see one. Are they omitted from SS amps or are they just relocated on the board somewhere?

I ask because I remember a tweak thread (at another site, a long time ago) concerning putting a low value cap in parallel with the speaker. I forgot what it was supposed to 'improve', but I think I remember it being called a shelving circuit.

The archives at this 'other' site do not go back that far. I would ask them, but they'd prolly be too busy putting green marker around the edge of their CDs.
 
No, it is not a "0.1uF" cap in the T-amp, (I don't recall the exact default value but I'm sure it wasn't 0.1uF as stock on the one I had) and if you are assuming it is, I will wonder if you likewise assume any other small cap is a 0.1uF?

Such a cap essentially shunts HF noise, and is particularly important in Class-D amps because they are prone to having high frequency components inherant in the way they work. If some other amp did not have bandwidth restriction and/or had HF getting into the signal or feedback path somehow, then it too would need such a cap on the output, BUT it would be better to be rid of that HF before this point as much as possible.
 
! said:
No, it is not a "0.1uF" cap in the T-amp, (I don't recall the exact default value but I'm sure it wasn't 0.1uF as stock on the one I had) and if you are assuming it is, I will wonder if you likewise assume any other small cap is a 0.1uF?


mmm....OK....


After looking some more, I've seen two different schematics with two different values, .1ufd and .01ufd

http://www.michael.mardis.com/sonic/images/TA2040.gif

http://i79.photobucket.com/albums/j144/audio1st/TA2024b.jpg

But sorry if I disturbed you.
 
3-LockBox said:



mmm....OK....


After looking some more, I've seen two different schematics with two different values, .1ufd and .01ufd

http://www.michael.mardis.com/sonic/images/TA2040.gif

http://i79.photobucket.com/albums/j144/audio1st/TA2024b.jpg

But sorry if I disturbed you.



Was it not a valid concern? Knowing that mine didnt' have 0.1uF, what can I conclude? Nothing yet until I draw out more info from you, why you are making such a conclusion. The links are not necessarily a T-amp though, are they? One is a reference schematic from it's looks, and the other I was too lazy to look around his site but could be a proposed circuit or mod. Anyway, if either were supposed to be the actual T-amp it looked like the 2nd was but it is the one mentioning 0.1uF which wasn't what the T-amp had.

So, I'm not disturbed but you need to not jump to conclusions based on some other schematic, possibly.
 
The idea is to "tune" the coil using a capacitor in parallell

This produces some ressonance...in a practical way, spikes generated by a coil in movement, inside a magnet (generator) will be "eated" by the capacitor....normally it is capable to work under hi voltages.

People decided to put into the amplifier boards...this was done around the seventies.... in series with 10 ohm resistor, as a low impedance (not to low) drain of hi frequencies..... well, it works avoiding HF oscilations that may born inside the amplifier board...if the oscilation start, in a microsecond, the capacitor will "eat it" and will send it to ground througth the 10 ohms resistor....more adequate is 2,2 ohms (Dr. Graham Maynard), as this may produce a more large "troat" to eat the starting oscilations.... that are not more than a repeating charge-discharge cicle.

Those modern things..... maybe to populate the board, maybe because designers are always afraid of oscilations, as they use much higher frequency components than really needed...so, having the capacity, the capability to oscilate (work) into 100 Megahertz, some transistors having some small capacitances because the board copper lines in parallel.... having some inductances because those copper lines too.... capacitances related the ground...well....all this together start a very good oscilator, and them you can measure 10 or 20 or more volts into the output...all high frequency.... sometimes 10 Megahertz or more...amplifier turns hot, sound turns strange, compressed, poor, with small dinamics, as all transistors are overdriven.

The capacitance in the output is always present, because the wires used, parallell wires, have some capacitance, and depending the length, this capacitance can be very big...but there is resistance too, the coil inductance....well...the reality is a big mess...and the inclusion of a capacitor in parallel with speaker is a very good idea...to use non parallell audio output cables, with low resistance and short length is another good idea....also to keep the damn 0.1 with the 10 ohms resistor is adequated...as transistors are turn faster and faster...and amplifiers are turning more and more "Radio frequency linear amplifiers"...and that care can avoid problems.

Audio is not perfect....never perfect, but it is nice.....but stop to analise deep those things as i use to do, because you will loose half that deep love, because there's a lot of spurious...a lot of spikes and crazy distortions everywhere...starting our own listening place, followed by aging effects and was inside ears....and zillions of distortions and non perfect things.... the challenge is to produce the "nice distortions"...this is the trick.

regards,

Carlos
 
Photo of the beast. His is marked 0.15 K63, my own is marked "L50 154" and '154' is 150,000pF, 150nF or 0.15uF. I've replaced mine with 0.1uF with no apparent change in quality. Not intentional, I just didn't have the 0.15uF values to hand. The SI has undergone a few revisions, I've no reason to doubt the one analysed by audio1st you link had 0.1uF fitted (and they're +/-20% tolerance parts ffs).

It is part of the output filter system to remove Class D supersonics, rather than let them into the speaker cables and the outside world. A 'normal' Class A/B audio amplifier wouldn't/shouldn't have the high level of supersonics there in the first place, so the zobel capacitor is adequate for any traces that are present.
 
3-LockBox said:


You're quoting me from vague memory and I'm quoting documentation,
and I'm jumping to conclusions?

Alllllrighty then! :rofl:


That's just it, the first link you provided is NOT documentation of a T-amp. It is a reference schematic from the datasheet. This alone when provided as evidence is a clear sign you jumped to conclusions.

Similarly, we could look at a (LM3875 for example) datasheet, see a 20K resistor on it and write "Why did Peter Daniel put 20K resistor in his Gainclone", it would be just as wrong, if we only ASSUMED he had used it based on something other than the real amp & corresponding schematic itself.

Was my first post as gentle as possible? Probably not, it was meant to get straight to the point instead of dancing around stroking your ego. Jumping to conclusions will be problematic for you sooner or later, and your attitude when it seems you either don't have or can't be bothered to check an actual T-Amp is a bit bizarre.
 
! said:
Was my first post as gentle as possible? Probably not, it was meant to get straight to the point instead of dancing around stroking your ego. Jumping to conclusions will be problematic for you sooner or later, and your attitude when it seems you either don't have or can't be bothered to check an actual T-Amp is a bit bizarre.


In a few more days perhaps. I ordered one this week, though mine is a SI Super T and may be different altogether.
 

taj

diyAudio Member
Joined 2005
! said:


Was my first post as gentle as possible? Probably not, it was meant to get straight to the point instead of dancing around stroking your ego. Jumping to conclusions will be problematic for you sooner or later, and your attitude when it seems you either don't have or can't be bothered to check an actual T-Amp is a bit bizarre.


Just my opinion, but you're (!) the one sounding more than a tad irrational. Not in your point so much as your delivery. It takes a lot of effort/guts to be amiable/mature when you feel like pouncing on someone. Try it one day.

..Todd
 
taj said:



Just my opinion, but you're (!) the one sounding more than a tad irrational. Not in your point so much as your delivery. It takes a lot of effort/guts to be amiable/mature when you feel like pouncing on someone. Try it one day.

..Todd


How little you understand, me. That was not a pounce, and I will also refrain from pouncing on your implication even if in error. I even attempting to explain, if only briefly, and yet you are still emotional, instead of logical about it.

I state what I consider truth and fact, and when I have to try to reword it because someone is taking an irrational emotional attitude, it does tend to come out odd sometimes. When you emotionally interpreted my reply, you probably took it in a certain context too. I wrote very little, so your mind is now making assumptions.

Being mature means (among other things) conceding when one is wrong and learning from it. It also means not being hypersensitive about mitakes, since everyone makes some, rather than getting right to the core of the matter and moving on.

I aided in that by posting two important things:

1) What was wrong
2) Possible reason why

It is important to know why! Far more important than the specific value of the cap, actually, because the logic that led to the conclusion is prone to be repeated. It was rather unnecessary that the thread took this tangent, because it was a valid question. Are valid questions sometimes offensive? YES! People make mistakes, and they either swallow ego and learn, or get defensive and don't (learn).

Possibly the OP now understands that one can't just read a datasheet schematic and conclude any amp build with the part uses the default values in the schematic, and possibly the OP also understands that when a mistake has potentially been made, it IS REASONABLE to wonder if the same thought process has perpetuated the mistake.

For example, if one thought 3 x 6 = 16,
It is logical to conclude that the same person calculating 3 x 6 x 4, may arrive at a wrong answer for that too. Giving the correct answer one time only is not as important as figuring out WHY, so the next time the same doesn't happen again.

When discussing something scientific, try to think logically not emotionally. We all make mistakes, myself included. Better to quickly point them out, point out possible problems, and move on.
 
I see that the T-amp and other amps have a .1uf cap twix the neg/pos speaker terminals.

Is this a shelving circuit? I've looked in side my solid state amps and I don't see one. Are they omitted from SS amps or are they just relocated on the board somewhere?
No, it is not a "0.1uF" cap in the T-amp, (I don't recall the exact default value but I'm sure it wasn't 0.1uF as stock on the one I had) and if you are assuming it is, I will wonder if you likewise assume any other small cap is a 0.1uF?

That's not a totally uncalled-for supercilious response?

"Being mature means (among other things) conceding when one is wrong and learning from it."
 
Hi,
it's the Zobel as fitted to a ClassAB amp to ensure stability with awkward loads.

The original networks proposed by Thiel showed a single capacitor across the speaker terminals rather than the more normal series cap and resistor that usually gets hung on the amplifier output.
Is there an inductor, with or without a damping //parallel resistor, upstream of the capacitor?

I do not know if a T-amp needs this type of stability network to allow it to operate correctly.
 
cpemma said:
No, it is not a "0.1uF" cap in the T-amp, (I don't recall the exact default value but I'm sure it wasn't 0.1uF as stock on the one I had) and if you are assuming it is, I will wonder if you likewise assume any other small cap is a 0.1uF?

That's not a totally uncalled-for supercilious response?

Wow I was giving some people too much credit, thinking they were mature enough to read something for it's technical value instead of reading through a touchy-feely filter.

1) It wasn't a 0.1uF cap. It was true and directly addressed what had been written previously.

2) I didn't recall the exact value but I am still certain it wasn't 0.1uF. I know because I have tons of 0.1uF and was looking for a higher quality direct replacement to try when I modded my T-amp.

3) "IF you are assuming it is". That's quite relevant. "IF" the OP wasn't assuming, this was an opportunity to write more about why it was supposed 0.1uF. IF the OP was assuming it was, also, why? Relevant.

4) I will in fact wonder, if someone jumps to a conclusion about one thing, if they jump to a conclusion about something similar. It is not only reasonable to wonder about the other values, but appropriate to determine what method is being used as it isn't generating data consistent with what is actually in many T-amps. When a source of data is producing what appears to be erroneous data, the only possible sane thing to do is put the remaining data under more scrutiny that it would normally be subjected to.

Yes, "That's not a totally uncalled-for supercilious response" unless you're a paranoid person who tries to read personal attacks into everything. They make pills to counter that problem now. An idea or a method a person uses can be attacked without it being an attack on the person. Again, nobody is perfect and to pretend otherwise would be folly. It is ridiculous that we should have to write 5X as much just to keep paranoid people from trying to imply something more or other than what was written.

Let me be blunt. I am not an indirect person. If I were trying to attack someone there would be no question whatsoever about it. My interest is factual, including the process of uncovering information and relaying it. That is a very significant thing in a forum like this, and when I report information I go to extra lengths to ensure it's as accurate as possible. If someone points out that it may be wrong, I would completely understand their concern over it, and I would want to know why my data was wrong so I didn't repeat the same mistake again.

If I EVER make a similar mistake, please DO put the rest of my data into question. This should not be about ego but rather a focus on information and the means with which it is obtained.

Now if I were to be judgemental and personal about it as you seem to think is fitting, I would have instead asked "If you don't know why it isn't uncalled-for or supercilious, then should I assume you don't see the problem in having the wrong information and therefore we should subject any info you provide to more scrutiny than would otherwise be prudent?".

When you try to make something an emotional issue, you do a disservice to everyone everywhere that tries to constructively argue towards a common goal of spreading accurate and reliable information.
 
Just to toss my two cents into this trainwrecked thread...

(!), there's a not-so fine line between direct or frank or even curt and being an arrogant jerk. Respectfully, you've crossed it and were pretty close already in your first post.

"...unless you're a paranoid person who tries to read personal attacks into everything. They make pills to counter that problem now."
while arguably factual, is insulting and unnecessary. Your question "I will wonder if you likewise assume any other small cap is a 0.1uF?" was in the same vein. It was clear (to me at least) that the OP had more understanding of electronics than that, i.e. he had more than _no_ understanding.

We can only assume your social customs and standards are different from generally what's demonstrated on this forum. You could easily find a style less caustic without resorting to "stroking your ego" or a "touchy-feely filter" (as you mentioned earlier) and things would go smoother for everybody.

That's just my friendly opinion.

The value for the cap in question has one value on the Tripath data sheet, but Sonic Impact used another. This I remember. Specific values, well crud...can't remember. DIYers have tried both values as well as eliminating those caps in modded T-Amps and found little if any difference.
 
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