I was talking about the resistive load of course. In real world its different, I know that!
However, in every case if you get 80W into 6R load 220VA transformer will not be enough.
Can you get 80W in to 6R with LM3886? Yes you can, with sinus 1KHz and to a resistive load. This is what "overture design guide" says. This is not real world but generally, companies give these type of informations in their manuals.. So comparisons are on this way!
When you buy a Marantz 100W RMS stereo amplifier then will you expect to have 100W into a real 8 ohm spekaer with dynamic signal (real music) or 100W into 8 ohm resistive load with sinus signal? I think this is the main question we should ask!
So,
If a person who willing to make a gainclone and wants to have 80W into 6 ohm speakers, then give him some RMS calculations... I am sure he will be satisfied, its not important if its real 80W or not! In anycase it will be over overkill anyway...
However, in every case if you get 80W into 6R load 220VA transformer will not be enough.
Can you get 80W in to 6R with LM3886? Yes you can, with sinus 1KHz and to a resistive load. This is what "overture design guide" says. This is not real world but generally, companies give these type of informations in their manuals.. So comparisons are on this way!
When you buy a Marantz 100W RMS stereo amplifier then will you expect to have 100W into a real 8 ohm spekaer with dynamic signal (real music) or 100W into 8 ohm resistive load with sinus signal? I think this is the main question we should ask!
So,
If a person who willing to make a gainclone and wants to have 80W into 6 ohm speakers, then give him some RMS calculations... I am sure he will be satisfied, its not important if its real 80W or not! In anycase it will be over overkill anyway...
Hi Dx,
I completely disagree.
If an amp is designed to supply Xwatts and is also designed to sound good driving real speakers (speaker meeting the specification of the amplifier designers) then it performs it's duty as an audio power amplifier.
If it can drive Xwatts into a resistive load, but due to inadequate current capability it cannot drive a real speaker then it fails as good audio equipment.
This inadequate current capability can be due to a poor PSU, or due to excessive losses in the amplifier or due to protection systems triggering and limiting output current into a valid load.
It is very important that it is a real power output claim for driving a real load.
I completely disagree.
If an amp is designed to supply Xwatts and is also designed to sound good driving real speakers (speaker meeting the specification of the amplifier designers) then it performs it's duty as an audio power amplifier.
If it can drive Xwatts into a resistive load, but due to inadequate current capability it cannot drive a real speaker then it fails as good audio equipment.
This inadequate current capability can be due to a poor PSU, or due to excessive losses in the amplifier or due to protection systems triggering and limiting output current into a valid load.
It is very important that it is a real power output claim for driving a real load.
Then which amplifier company gives the real values? And why should we calculate the real values? While theyre "cheating" us?
If I am totally satisfied from my LM3886 amplifier which I was supposing that its 60W or so but in fact it can give only 20W or less... Who cares the "realities"?
I am saying, with 35v (symmetrical) psu, he will need 5.25A (for resistive loads). Do you think he can adjust the volume until SOA get activated? So if you make him totally sure, lets say "design a PSU with 8A rate"... Thats the limit of LM3886!
If I am totally satisfied from my LM3886 amplifier which I was supposing that its 60W or so but in fact it can give only 20W or less... Who cares the "realities"?
I am saying, with 35v (symmetrical) psu, he will need 5.25A (for resistive loads). Do you think he can adjust the volume until SOA get activated? So if you make him totally sure, lets say "design a PSU with 8A rate"... Thats the limit of LM3886!
Dxvideo said:
I wonder how many does actually give the real RMS wattage values.
I would not even want to try and connect a resistive load on to each of the outputs on many of these days "5.1 amplifiers" claiming to give 100W per channel. and doesn't even weigh 3kg's.
Might be 100W per channel , but only one channel at a time or something. And that might be peak power. nmot even rms rating.
The biggest cost cut will probably allways be the powersupply , so you can bet you will get HUGE voltage drops under high loads.
The term Watts in commercial amplifiers is completely misused.
look at the 1000W to 1500W ratings of car amplifiers.
Watt ratings have become a joke.
The watts quoted by me/us are usually real watts into resistive loads.
No-one is cheating us here.
The problem comes from the lack of current capability into reactive loads. Again this is not cheating it simply sounds bad.
The reasons for this lack of current can be manifold and all of them come down to budget or incompetence on the part of the designer/team.
No-one is cheating us here.
The problem comes from the lack of current capability into reactive loads. Again this is not cheating it simply sounds bad.
The reasons for this lack of current can be manifold and all of them come down to budget or incompetence on the part of the designer/team.
AndrewT said:
There's good news too--really good news! Some amplifiers have the "driver command" aspect for tight, high resolution, and very hard hitting dynamics. This is nicer to the ears than a high average SPL. Amplifiers with this aspect are more powerful than advertised, not less.
Oh, and Andrew knows just how to make them do this too.
Thanks again for helping me tune up those little LM1875's until the laws of physics hit the same gray area as the speaker grills--the carpet.
AndrewT said:
So if an amplifier have a "lack of curent capability into reactive loads" Fo example;
- If it cannot handle 4 ohm loads and
- If everybody knows that a 8 ohm speakers imdepance can drop down to 4 ohm,
- And theyre still insist that "our amplifier can drive 8 ohm speakers"
Dont you think its a kind of "cheating"?
- If we should calculate (in fact you have already calculated) that the real current need of a 35W into 6R amplifier is 10A! And if an amplifier company have a lot of design engineer, smarter than me...
- And theyre still manufacturing 50W "hi-end" new brand stereo amplifiers
with just only 200VA transformer..
Dont you think its a kind of "cheating"?
My friend...
Okay,
Lets have a look what I said first;
Dear Anarion,
You can get ~83W into 6R load with LM3886T.. You'll need 2°C/W heatsinks for each chip. The power supply must be 35v symmetrical (35+35) at least. And the current need is 5.25A for each rail. That means you will use 26+26 v secondary 275VA transformer, seperated rectifier bridges and 20,000uF reservoir capacitors for each rail.
And if u use Rf=20K, Ri=680R then your input sensivity will be ~1v RMS for 83W output...
So,
Whats wrong with that? If the companies are on right way....
You hitted me first
Lets have a look what I said first;
Dear Anarion,
You can get ~83W into 6R load with LM3886T.. You'll need 2°C/W heatsinks for each chip. The power supply must be 35v symmetrical (35+35) at least. And the current need is 5.25A for each rail. That means you will use 26+26 v secondary 275VA transformer, seperated rectifier bridges and 20,000uF reservoir capacitors for each rail.
And if u use Rf=20K, Ri=680R then your input sensivity will be ~1v RMS for 83W output...
So,
Whats wrong with that? If the companies are on right way....
You hitted me first
50+50W gives a total output power of 100W.
The usual recommended range for transformer rating is about 100VA to 200VA to match that loading.
If your amp is described as high end then going for the upper end of that range may give better performance and may be used in advertising blurb as a plus.
Similarly 80+80W would require about 160VA to 320VA and I might be tempted to go for 250VA, very close to your 275VA.
The usual recommended range for transformer rating is about 100VA to 200VA to match that loading.
If your amp is described as high end then going for the upper end of that range may give better performance and may be used in advertising blurb as a plus.
Similarly 80+80W would require about 160VA to 320VA and I might be tempted to go for 250VA, very close to your 275VA.
But, you have not justified why this is cheating.
If I may add a small bit of confusion. . .
Some of this power limitation is thermal management (heat). However, on an amplifier overvolted so that it becomes too hot on 4 ohm speakers, a simple 1 ohm resistor is all it takes to cool it off to the same, similar, or less temperature that it would have running 8 ohm drivers.
Well, that part confuses me.
Some of this power limitation is thermal management (heat). However, on an amplifier overvolted so that it becomes too hot on 4 ohm speakers, a simple 1 ohm resistor is all it takes to cool it off to the same, similar, or less temperature that it would have running 8 ohm drivers.
Well, that part confuses me.
AndrewT said:
Why this is cheating?
A question like "whats the meaning of life?"...
If I look at your side, this is cheating... You said that;
Vpk=15.5V
Ipk(resistive)=5.2Apk
Ipk(reactive)<=15Apk.
Why its cheating? Because;
-If you describe an amplifier as 80W then its 80W into resistive load... And it capable to sink or source 5.2A pk.... Not 15A!!! And I believe non of a commercial design that labelled 80W cannot drive 15A anyway...
-If your amplifier is 80W. That means your psu is designed for 80W, means capable to source 5.2A peak... If you consider that even your amplifier can drive 15A to load in this case your power supply cannot source 15A.
I mean, if your amplifier labelled 80W and still cannot source 15A then its "cheating". Because its fake! Of course with your calculations and your looking angle!
However if I look at the other side...
Everybody says 80W is 80W... Its not important if its 80W into resistive load or inductive load. Everybody knows "thats a 80W amplifier" nobody cares its real measurements.
Then with this angle; this is not "cheating" As I wrote first..
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