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Author Topic: Can I use 15V +/- Regulators instead of the Zeners?  (Read 1860 times)

exztinct01

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Can I use 15V +/- Regulators instead of the Zeners?
« on: March 29, 2016, 10:32:25 AM »
I'm building this http://sound.westhost.com/project27.htm as preamp for an LM1875 power amp.
Since I don't think this preamp will require current above 1 Ampere, can I use LM7815/7915 voltage regulators instead of the zener diodes?
Also, what other things do I have to change to match the output of the preamp to the input of the LM1875 power amp?
~ Stephen

Enzo

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Re: Can I use 15V +/- Regulators instead of the Zeners?
« Reply #1 on: March 29, 2016, 05:07:00 PM »
You can as long as your V+ and V- supplies do not exceed the input voltage of the 7815/7915.  But what is wrong with the zeners?  They are dirt cheap and effective in their function.

The preamp is a stand alone item, it will feed most anything you connect it to.  Remember, these are guitar amps, not precision lab equipment.

Loudthud

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Re: Can I use 15V +/- Regulators instead of the Zeners?
« Reply #2 on: March 29, 2016, 05:33:52 PM »
7815/7915 regulators are not as bullet proof as the manufacturer would like you to believe. Short +15 to -15, one regulator wins and the other dies. Think they will just shut off if they get too hot? The one that shuts off first will likely be killed by the other one. Just use zeners.

exztinct01

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Re: Can I use 15V +/- Regulators instead of the Zeners?
« Reply #3 on: March 29, 2016, 05:55:15 PM »
well, i just thought the regulators would be better   :loco
but thanks for the info
~ Stephen

J M Fahey

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Re: Can I use 15V +/- Regulators instead of the Zeners?
« Reply #4 on: March 29, 2016, 08:22:50 PM »
Well, they are better, at least have better specs, but acrry along some extra constrainsts:
1) regulators can easily provide up to 1A (if available from transformer that is) while Zeners are practical for up to a few tens of milliamperes (fine for a preamp)
2) regulators have very definite voltage limits (as mentioned above), while Zeners, with the proper resistor, can regulate even if fed hundreds of Volts.
The component which bears the worst load is the resistor, which is stronger than any semiconductor.
3) Zeners are accurate within 5% or so; regulators are better than 1%.
Again no big deal feeding a preamp.
4) regulators are fussy about the load and can oscillate in many cases ... zeners do not.

In a nutshell: to each his own, and in some areas they overlap.

Enzo

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Re: Can I use 15V +/- Regulators instead of the Zeners?
« Reply #5 on: March 29, 2016, 08:58:50 PM »
Then we get into what "better" means.   The regulators might provide a more accurate voltage or even a more stable voltage.  But we are talking small percentages.  The 15v just needs to be more or less.  Imagine your car tires.  One tire pressure gauge reads 34 pounds, while another reads 34.26 pounds.  So it is more accurate, but does knowing that extra quarter pound really mean anything useful?   It doesn;t matter if your 15v supply is 15v or 14.8v.  It just doesn't.  That is what I mean by just a guitar amp, not a laboratory instrument.

 

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