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大 电 流 设 计 的 功 放 是 什 么 概 念 ？ [复制链接]

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madog
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madog

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发表于 2004-02-12 15:50 |显示全部

SMERT 在 2004-2-12 15:25:01 发表的内容
多谢指正，我是学foreign affairs的，对电路知识仅略知一二。

Dear Mr/Ms Madog,
Many fans are pretty interested in your explanations. If you write in Chinese, it will help more junors to understand technical terms such as Bias, idling current, signal current, high capacity design etc. Some unresponsible manufacturers use coin concepts and terms to mislead entrants.
Anyway, thank you for your contribution.



I am sorry to say, SMERT, I cannot type Chinese and I am too old to learn
that I'd rather spend more time enjoying msic. I will appreciate some guys
like you with good English understanding to translate for me if guys here
strongly request.
Deeply apologised not able to type Chines and this is hurting me always
as a Chinese cannot type Chinese. Luckly, my hand writing is absolutely OK.

Thanks folks, I love you all.
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madog
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madog

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发表于 2004-02-12 12:23 |显示全部

SMERT 在 2004-2-11 15:42:19 发表的内容
大典刘设计并不是你所说的那个意思。你说空闲电流比信号电流大，这种说法是不对的。信号电流非常小，功放管的空闲电流比信号电流大多了。空闲电流的大小取决于设计者的设计。此外，信号大小取决于电压，而不是信号电流的大小，除非信号输出端的内阻非常低，比如后级输出。后级也是推动低电阻的负载，所以输出的电流比较大，但也需要一定的电压来驱动负载。在这个例子里，负载就是音箱。

甲类放大是另一回事。其设计原理是空闲电流调整为满功率输出电流的一半。这就是甲类。

当某人宣称是大电流设计时，他指的是后级理论上可以驱动任何阻抗的负载，比如1至8欧姆。相当于8欧姆可以输出100瓦，4欧姆可以输出200瓦，以此类推。一些功放甚至可以驱动1欧姆的负载，此时的输出功率为800瓦。当然，没有功放可以驱动0负载，此时输出和电流都为无限大。

你的评论会误导一些初烧友，请注意。

我所指的信号电流是晶体管放大的部分，而不是信号源产生的电流，我同意我没有在上一贴中指明。

你所描述的其实不是大电流设计，而是大功率设计，它与输出电压和电流相关。此外，你还要保证一台甲类8欧姆100瓦的功放在4欧姆200瓦时还能保持甲类工作。很显然，只有高空闲电流的设计才能达到这个能力。


翻得比较仓促，不知是否贴切。




It's Ok but the last quote is not quite to the point.
What I wrote Idling current is actually called BIAS, which is a more technical term. Therefore BIAS and IDLING CURRENT are same in electronics
in many case.

To elaborate what is idling current or bias. Class A power output will
biased at half of the peak power output current. Say, for example, when the peak rms power takes 10 Ampere, then, when no signal input, the idling
current should be 5 Ampere. In electronic term, we will say this power
amplifier was biased at 5 Ampere.

Whether or not the power supply would satisfy the power transistor(s)
requirement, it will be another issue.

Truly, the Pass Son of Zen is biased in Class A using 1,000 Watt power transofrmer is of course high current design.

High current capability is the amplifier are capable of driving very low impedance load in an increament of being the lower the loading, the more power it gives. For example, 100 w into 8 Ohm, then it should ne 200 W into
4 Ohm and so on.

However, when you have a high current power supply then you need a really high power ouput transistors to operate. That means, some transistor
ouput design is not ready to drive load impedance even thou the power
supply is several time bigger then it needs.

In the case of the Son of Zen, I didn't take a close look at it's circuit, so I cannot comment if these output devices are capable of driving low
impedance loading thou the power transformer is 1,000W.

To satisfy high current drive, the amp should firstly have output stage designed for low impedance drive (Very costly because you have to parellel
lots of power devices) then with sufficient supply current and this is the job of the power transformer and the capacitors.

Thank you for your translation, you've done a good job.

Cheers buddy.
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madog
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madog

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发表于 2004-02-10 17:37 |显示全部

KENTRYFO 在 2004-2-9 11:02:54 发表的内容
又可拜读大作，甚幸！




Thanks and you are welcome
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madog
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madog

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发表于 2004-02-10 17:35 |显示全部

Gavin 在 2004-2-7 18:17:44 发表的内容
小弟认为, 大电流功放设计是指末级功率管工作点采用大静态电流设计,而不是功放的输出电流. 好处不用多说, A类(甲类)机优势.

NELSON PASS设计理念中一个重要的特点是,晶体管的静态电流要远远大于信号电流.他为DIY土炮党提供过一个叫SON OF ZEN的电路,A类两声道2X10W左右的输出功率,竟然要1000W的电源变压器.是一个很典型很疯狂的大电流功放设计.我和一些DIY好友却非常喜欢.





Something to add to your Son of Zen. This Pass amp design has a very very high reserve so the designer use a power transformer of 1,000 Watt.
Any one can use such topology by replacing his transformer to a more powerful one. Say 2 fold to 10 fold.

This issue is targeted at the internal impendance of the power supply. In
such DIYers can follow easily and there is no secrete or any big deal.

Designing amplifier has another very important issue, that is what we call
VOICING. Even though one may use the top quality parts but may not
result for a musical reproduction. If we look at many of the British design
amplifiers, they use quite common parts but sounds musical. This also true
to British speakers.

However, musical doesn't mean it is necessarily the best to high fidelity.
As I mentioned before in this forum, the best of high fidelity is to abstract
full details from the software.

Hope this had been clearly understood.

Cheers evrybody
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madog
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madog

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发表于 2004-02-10 15:08 |显示全部

Gavin 在 2004-2-9 18:13:37 发表的内容
madog 在 2004-2-9 6:25:15 发表的内容
Gavin 在 2004-2-7 18:17:44 发表的内容
小弟认为, 大电流功放设计是指末级功率管工作点采用大静态电流设计,而不是功放的输出电流. 好处不用多说, A类(甲类)机优势.

NELSON PASS设计理念中一个重要的特点是,晶体管的静态电流要远远大于信号电流.他为DIY土炮党提供过一个叫SON OF ZEN的电路,A类两声道2X10W左右的输出功率,竟然要1000W的电源变压器.是一个很典型很疯狂的大电流功放设计.我和一些DIY好友却非常喜欢.


Large current design topology is not what you mean. When you said, idleing current is much larger than the signal current is incorrect. Signal current
is so small that idleing current of the power transistor is much larger then signal current. Idling current is designed fromthe designer according to his
design. Sometimes related to the power transistors used. Furthermore,
signal is on the issue of signal voltage but not count on how large is the
current unless the signal source is of very low impedance such as the ouput signal from the power amplifier. Then again this is low impedance drive,
it take lots of current but it also need certain high voltage to drive the
current into the loading. In this case, loading is the loudspeaker.

Class A is another matter. The theory is based on the idling current is
biased at half of the full power output current. This is class A.

When one claims that large current design, means the power amp is able
to drive theoritically almost any impedance loading,say from 1 to 8 Ohm
load and when one claims at 8 Ohm load would produce 100 Watt,
then at 4 Ohm, it gives 200 Watt, and so on. Some amp even can drive
down to 1 Ohm. In this case the power output should produce 800 Watts.
Of course, any amplifier cannot drive zero Ohm loading, at this point, the
output become infinity and also the required current is infinity.

Your comment might mislead the juniors. Please be careful.


The signal current I meant is the current that the transistors will amplify, it is not the current from the signal source. I agree that it is not clearly mentioned in my last post.

The situation you describe is not the high current design acctually. It is a designation of high power capacity, which relates to the output voltage and output current. Meanwhile, you have to ensure that a CLASS A 100W@8ohm amp shall remain CLASS A operation when it works at 200W@4ohm. Obviously only high idleing current can do so.



Your latest comment also very confusing. But please note, in you case, the signal current and the biase current are two separate issue. It greatly depands on what class is working on it.

In the case of power amplfier, the first stage is voltage amplifier dominated
by voltage. The second stage is also voltage amplifier, furhter lift the
signal to higher voltage level. The third stage is current amplifier but no voltage gain but oost the current so that they could drive the power transistors that are of quite low impedance.

In your case, you may say, high biase means high current design but this is not a common language that every electronic engineers ot audiophiles
could understand. In our case, high current capability and hign current design are same. It is that only high current design then have the high current capability. One is REASON and the other one is RESULT.  They are
same.

Of course, now I understand what is high current design in your mind and I am soory if my post could have offending you.

Just for your information, I once read about Nelson Pass in an article or forum, he commented that high speed rectifing diode and ordinary diode has not sonical difference in an amplifier. And I doubt that. Personally I very much respect Mr.Pass but would not agree with him at this point.

It' almost saying that, any conductor is same sonically ???

Cheers everybody and have a great week
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madog
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madog

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发表于 2004-02-09 06:25 |显示全部

Gavin 在 2004-2-7 18:17:44 发表的内容
小弟认为, 大电流功放设计是指末级功率管工作点采用大静态电流设计,而不是功放的输出电流. 好处不用多说, A类(甲类)机优势.

NELSON PASS设计理念中一个重要的特点是,晶体管的静态电流要远远大于信号电流.他为DIY土炮党提供过一个叫SON OF ZEN的电路,A类两声道2X10W左右的输出功率,竟然要1000W的电源变压器.是一个很典型很疯狂的大电流功放设计.我和一些DIY好友却非常喜欢.


Large current design topology is not what you mean. When you said, idleing current is much larger than the signal current is incorrect. Signal current
is so small that idleing current of the power transistor is much larger then signal current. Idling current is designed fromthe designer according to his
design. Sometimes related to the power transistors used. Furthermore,
signal is on the issue of signal voltage but not count on how large is the
current unless the signal source is of very low impedance such as the ouput signal from the power amplifier. Then again this is low impedance drive,
it take lots of current but it also need certain high voltage to drive the
current into the loading. In this case, loading is the loudspeaker.

Class A is another matter. The theory is based on the idling current is
biased at half of the full power output current. This is class A.

When one claims that large current design, means the power amp is able
to drive theoritically almost any impedance loading,say from 1 to 8 Ohm
load and when one claims at 8 Ohm load would produce 100 Watt,
then at 4 Ohm, it gives 200 Watt, and so on. Some amp even can drive
down to 1 Ohm. In this case the power output should produce 800 Watts.
Of course, any amplifier cannot drive zero Ohm loading, at this point, the
output become infinity and also the required current is infinity.

Your comment might mislead the juniors. Please be careful.
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