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Old 6th March 2006, 05:59 AM   #1
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Default looking fo good preamp design!!

i am looking for a good preamp fo my 200rms(8ohms) amplifer that could fit into it.
anyone has a design of 4558d I.C that is designed to be a preamplifier..o anykind of preamp that could fit to a certain amp..

thanks in advance..
Ryan Jan..
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Old 6th March 2006, 06:39 AM   #2
lineup is offline lineup  Sweden
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Default Re: looking fo good preamp design!!

Quote:
Originally posted by clovi_kate
I am looking for a good preamp fo my 200rms(8ohms) amplifer that could fit into it.
Anyone has a design using OP-Amp 4558?
First for a good Op-Amp preamplifier
you will need a regulated +15 Volt and -15 Volt power supply.

Schematic below shows such a good supply.
Easy to build and regulated, stable 2x15 Volt output.

It uses 3 transistors.
And one 15 Volt zener diode.
D122 in diagram.
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Old 7th March 2006, 07:25 AM   #3
gerhard is offline gerhard  Germany
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Default looking fo good preamp design!!

Hi,

I don't like this circuit too much.

1. R241 and R244 are up to no good. They just rise the input voltage required and increase the source resistance of the +-Vcc sources. This is against the purpose of a regulated power supply. R241/244 return nothing for it.


2. Having a small capacitor in parallel to a Z diode does not help much. The noise source in the Z diode has a low impedance which means that the low pass filtering works only for high frequencies.
It would help to swap D122 and C162.


3. I don't think that it is a good deal to replace a Z diode by 3 resistors, a capacitor and a transistor. The circuit amplifies the noise of D122, Q118 and whatever makes it from -vcc to -15v before using it as a reference for Q116. The hi impedance divider R247, 248, 249 adds additional noise. The single pole introduced by C165 may help a little bit, on the other hand C163 may go under against the Miller-multiplied C165. Stability of the positive supply may depend on part values.

Methinks it would be better to use the negative half of the circuit for the positive side, too. Less parts, simple regulation loop, trivial to troubleshoot and not a single resistor that couldn't vary +- 50% without consequence on circuit functionality.


4. The nominal -15V output voltage will be -15.7V if D122 is a 15V type. The +15V output depends on R247 to 249 additionally.


best regards, Gerhard

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Old 7th March 2006, 11:31 AM   #4
gerhard is offline gerhard  Germany
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> 4. The nominal -15V output voltage will be -15.7V if D122 is a 15V type.

oohps, -14.3V. I shouldn't post at 4 AM.

Gerhard
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Old 7th March 2006, 01:33 PM   #5
ilimzn is offline ilimzn  Croatia
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Default Re: looking fo good preamp design!!

Quote:
Originally posted by clovi_kate
4558d I.C that is designed to be a preamplifier..
4558 is a rather old OP-amp which has a much more universal palette of applications than just preamps. Since it's introduction (late 70s?) many improved OP-amps have been introduced to the market, some offer increased performance even at a lower price.
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Old 7th March 2006, 02:15 PM   #6
Bazukaz is offline Bazukaz  Lithuania
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Why not use a regulator IC ? 7915/7815s are easy to use, protected from short/overheat.
For an op amp , you need low-noise.For example, - NE5532, LM833 , etc.
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Old 8th March 2006, 06:00 AM   #7
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does anyone have a schematic diagram of NE5532 or 4558 I.Cs? or anything that is similar to this op amp..?
thanks a lot..



ryanjan..
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Old 8th March 2006, 03:18 PM   #8
gerhard is offline gerhard  Germany
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Quote:
Originally posted by clovi_kate
does anyone have a schematic diagram of NE5532 or 4558 I.Cs? or anything that is similar to this op amp..?
ryanjan..
http://www.semiconductors.philips.co...SE5534_A_2.pdf

How to use it:
http://www.semiconductors.philips.co...otes/AN142.pdf

Dual version:
http://www.semiconductors.philips.co...A_SA5532_3.pdf


http://focus.ti.com/docs/prod/folder...t/opa2134.html

www.analog.com

You may find lots of other interesting chips on these servers.

4558, 709 and 741 are really obsolete.

Now don't let us start a new thread on OpAmp sound...

regards, Gerhard
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Old 8th March 2006, 09:07 PM   #9
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http://sound.westhost.com/project88.htm

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