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    NE5534 quad version?

    Is there a quad version equivalent of the NE5534?
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    Re: NE5534 quad version?

    Hi,

    NE5534 is at least 40 years old.
    Why do you look for those old Opamps.
    It was a good audio Opamp, but now there are better ones.

    Klaus
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    Re: NE5534 quad version?

    Quote Originally Posted by KlausST View Post
    Hi,

    NE5534 is at least 40 years old.
    Why do you look for those old Opamps.
    It was a good audio Opamp, but now there are better ones.

    Klaus
    It has been proven a lower noise alternative for my circuit http://qrp.gr/tmaf/
    The Jfet ones I have tries yielded in weird oscillations and other problems and also not lower noise (hiss)
    Professional engineering is the top, but amateur engineering is more fun.
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    Re: NE5534 quad version?

    To the best of my knowledge, there are only duals, NE5532
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    Re: NE5534 quad version?

    It has been proven a lower noise alternative for my circuit http://qrp.gr/tmaf/
    The Jfet ones I have tries yielded in weird oscillations and other problems and also not lower noise (hiss)
    The op-amp stages have virtually no gain so I doubt there is any real advantage in using super low noise amps. Almost all the hiss will be coming from the output stage.

    JFET amps are no less stable than bipolar ones so I suspect any oscillation is down to inadequate decoupling or poor layout.

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    Re: NE5534 quad version?

    There was demand and need for a quad NE5534, but it never happened because of the heat dissipation. One IC alone runs toasty due to high Class AB bias currents and more driving 600 ohm loads or voltage high rails. I think it would end up past the DIP package limit. Some Neve recording consoles used NE5534's at +/-19V using hundreds of them which heated up the room.
    Also not enough pins for compensation caps, so it would have to be a NE5532 and those caps are huge on the die. NE5532 die shot

    Quad OPA1604 is smt SO-14 part so you'd have to do thermal calcs.

    edit:
    The LM383 is fairly noisy and if you are running that directly into headphones, it would be terrible.
    Headphones from an audio power amplifier always get an attenuator to feed them and keep the signal/noise ratio decent.
    I would add at least 100R series for the headphone feed and another resistor to GND to suit the volume. The 1000uF cap could use a charge resistor to stop damaging thumps too.
    Last edited by prairiedog; 18th March 2020 at 18:31.



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    Re: NE5534 quad version?

    Hi,

    NE5532 and NE5534 are not exactly the same. They differ in gain and in stability.
    NE5532 is stable down to gain of 1
    Where NE5534 is stable down to gain of 3 only.

    Headphones from an audio power amplifier always get an attenuator to feed them and keep the signal/noise ratio decent.
    I did a lot of noise calculations and I can't see how a series resistor can improve SN ratio. Please explain with values.

    Klaus
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    Re: NE5534 quad version?

    This is my reasoning, I may have gotten sound dB power and energy mixed up (10*log vs 20*log).

    Take average speaker sensitivity 92dB SPL 1W/1m and headphones 92dB SPL 1mW, and using an 8R speaker at 1m away, verses a 32R headphone with no air loss.
    This means headphones need 1/500th the power of a loudspeaker to make the same SPL at your ears, in this example.
    But the audio amp LM383 hum and noise ends up present at the output regardless of the volume control setting. The way the circuit is right now, a loudspeaker or headphones will see the same voltage, so the headphones make the noise appear much much louder. 1/500 is almost 27dB which is a huge difference.

    It is traditional to attenuate headphone drive with 100-220R in series with each headphone channel. This is done on receivers and other audio gear.
    I assumed OP's noise problem would certainly show up when using headphones. Otherwise, it's upstream of the volume control or oscillations.
    OP's circuit has some component values out to lunch, for example 100uF coupling cap then 470pF feed to the op-amp. So it might be losing all the signal there and trying to get it back with lots of gain afterwards, which makes for poor S/N ratio. I would not have a 0.22uF cap directly across the LM383 output as a capacitive load, there should be a 1-10R resistor in a Zobel network lest the IC go unstable. I had TDA2030/LM1875 oscillate at 13MHz which seemed like high noise and distortion until the scope revealed the output network needed optimization.

    http://www.sengpielaudio.com/calculator-soundlevel.htm

    edit: The original circuit is from 73 Magazine by W6QIF http://n5dux.com/ham/files/pdf/The%2...o%20Filter.pdf
    Last edited by prairiedog; 19th March 2020 at 05:56.


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    Re: NE5534 quad version?

    I agree with Prairiedog regarding the output stage. The data sheet for the LM383 specifically adds a resistor in the output 'Zobel' network to prevent oscillation, they suggest 1 Ohm in series with 0.2uF.

    The 470pF coupling capacitors are necessary though, even if the values seem counter intuitive. If anything it is the 100uF value that is excessive rather than the 470pF being too small. The impedance after the 470pF has to be high in order for the 'gyrator' notch and peak filters to operate and at the correct frequencies.

    I'm not sure about the 0.22uF capacitors across the gain control potentiometers, I can't see any useful purpose for them except to reduce high frequencies. If it needs them I would be inclined to place them across the track instead of the wiper then isolate both from the previous stage with a small (~1K) resistor. Their effect at the moment will be limited and at maximum gain the op-amps will be prone to oscillation.

    Brian.
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