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Old 10th November 2004, 04:57 AM   #1
janusz is offline janusz  Australia
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Default where should driver transistors go?

If a PA is to have regulated and unregulated PS then where should driver transistors go?

Most PAs with dual PS have the drivers bundled together with the output devices on the unregulated but ocassionally - eg. Stochino amp - these are placed on the regulated supply.

So - should the drivers be on the unregulated rails together with the power devices they drive or should these be connected to the regulated supply?

And WHY?
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Old 10th November 2004, 12:29 PM   #2
Mr Evil is offline Mr Evil  United Kingdom
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That depends on the topology. Generally there will be no benefit to hum from using them with the regulated supply. Assuming the regulated supply is of higher voltage than the unregulated, you may get better output swing by using them with the regulated supply, but that may not be necessary and may cause problems if the output devices are overdriven too hard.
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Old 14th November 2004, 11:34 PM   #3
janusz is offline janusz  Australia
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Thanks Mr Evil,

Looks that either not many people give much thought to the output stage design or it is more than obvious to them where the drivers shoud go.

Although I studied engineering and the course even included 2 semesters of electronics it was very long time ago and afterwards I did a completely different course. Anyway, I found my vocation in economics and audio electronics are only a hobby of mine.

Nevertheless, I remember reading once a brief discussion on this topic.. Some of the reasons were these you have just mentioned here but there was also something about output devices tracing better (currentwise) signal voltage form driver transistors if these were on the same supply. I remember it vaguely so I would like to be sure if it might be another reasons. It might be good to know if there were any other reasons for keeping driver transitors and output transistors on the same rails. Alternatively, could there be any benefits of placing them on separate regulated rails. Maybe one day someone will enlighten me in this matter.

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Old 15th November 2004, 01:17 AM   #4
quasi is offline quasi  Australia
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Hey Janusz...long time no hear...(read)

The amp that is the subject of the long post of mine will have regulated supplies for the driver stages (except for the 3rd stage covered in great detail in "power amp under development")

This amp is about a week away from being fired up ...I'll let you know if I notice anything. I have an almost identical amp that uses the same rails all the way through.

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Old 15th November 2004, 06:55 AM   #5
aht is offline aht  Thailand
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Default In my idea

Driver stage don't need regulated power supply because this stage has many difference ratio between signal and noise

In my project 2n5401-2n5551-mje15030-mj15024 with supply +/- 51 V .I measure output with oscilloscope in mV result is 0.01 mVAC there is no hum and transistors doesn't GO...

My idea right or wrong


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