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Power amplifier on NE5532 - ty.ytka

tytka  79 20151 Cool? (+61)
📢 Listen (AI):

TL;DR

  • A stereo power amplifier built from NE5532 operational amplifiers replaces a conventional power stage with an op-amp-based experiment.
  • Each channel uses four op-amps in the voltage stage, 64 op-amps in parallel as the output buffer, and one op-amp for DC-servo control.
  • The supply is stabilized at +/-18 V with LM338 regulators, and speaker protection uses a uPC1237 circuit.
  • The finished amplifier delivers 2×14 W into 8 ohms and sounds detailed, clean, and surprisingly strong in the bass.
  • Cooling matters, because the regulators dissipate a lot of heat and the op-amps reach about 45-50°C during operation.
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It may seem ridiculous, but you can build an interesting power amplifier from ordinary operational amplifiers (with the right amount of them). :)

From this "miracle" I achieve 2×14 W on a load of 8 ohms. Maybe this value is not shocking, but considering what we get it from, it's probably not a little bit.

First things first.
This project was created only as an experiment, made out of curiosity.
The source of inspiration for this project was an article by Douglas Self in the Elektor magazine (issues 10 and 11 of 2010). Whereas the design of my headphone amplifier ( link ) served as a fitting for this very crazy project.

However, my project is not an exact copy of the mentioned article. I simplified it a bit in my experiment. I resigned from balanced inputs and the possibility of connecting both channels into a bridge. I made the security system on uPC1237, and the stabilizers on LM338.

I assembled the whole amplifier on three boards. One containing stabilized power supplies, supplying +/-18 V, and a loudspeaker protection system. The other two contain amplifiers for each channel. Each channel contains 4 operational amplifiers in the voltage amplifier part, 64 operational amplifiers connected in parallel working as an output buffer and one op-amp operating in the DC-servo system.

Tile schemes:



A few photos of the assembled layout:



Now maybe a few words about the impressions of the final effects.
Overall, I perceive the amplifier very positively from the listening point of view. The presented sound is quite detailed, clean without coloration. I was surprised by the quality of the bass, but in my opinion it is due to the quality of the power supply (stabilizers).

For now, I do not plan to use this project for a specific purpose, but I also do not rule it out in the future. However, it is quite interesting in terms of sound.
However, if someone wanted to use something like this for a specific purpose, remember to ensure proper cooling. Unfortunately, the stabilizers have to dissipate quite a lot of heat, and even the operational amplifiers themselves heat up to about 45-50 degrees Celsius during such operation.

Something about parameters.
Output power with simultaneous control of both channels - 2×14W on 8 ohms .
Other parameters are presented in the table below. Values for three different output powers 1W, 10W and 14W .



The author of the article mentioned at the beginning achieved slightly different parameters in his experiment:



The differences in the obtained parameters could have been influenced by the simplification of my system and the fact that I used the cheapest version of NE5532, because " P ".
About Author
tytka
tytka wrote 737 posts with rating 1828 , helped 8 times. Live in city Pabianice. Been with us since 2006 year.

Comments

marweg1967 04 Jul 2023 02:43

I read that article some time ago (although not in Elektor) and I was very interested in it. So much so that I also decided to implement this seemingly crazy project someday. Unfortunately, the word "someday"... [Read more]

rb401 04 Jul 2023 04:12

The concept seems older than 2010 to me. Your performance is very nice. I also like that you managed on a single-sided PCB. Such a curiosity. Recently, on Aliexpress, I also came across several such... [Read more]

mkpl 04 Jul 2023 07:24

Overall nice but for the fan and for fun. What did you measure with? Do you have a card reference measurement? Because you don't know where the measurement limits are. The second thing, do you have... [Read more]

tytka 04 Jul 2023 08:36

I also found similar modules on Aliexpress. Only they break everything into mini-blocks. Those boards that colleague rb401 pointed out are the output buffers themselves. They even offer such little things: ... [Read more]

Urgon 04 Jul 2023 10:54

AVE... This is a very well made design, and an interesting concept, although usually parallel connection of operational amplifiers is practiced in order to reduce noise in ultra-sensitive measuring amplifiers.... [Read more]

katakrowa 04 Jul 2023 19:35

Considering that for 5 USD we can buy 100 pieces of NE5532 in SMD, the project makes quite a lot of sense. [Read more]

Urgon 04 Jul 2023 19:47

AVE... The only question is, are these cheap NE5532 originals or Chinese clones? If they are clones, do they therefore keep their parameters? [Read more]

gulson 04 Jul 2023 20:08

Very interesting design, that's what DIY is for! Write to me in a parcel locker and I will be happy to send you a gift. [Read more]

tytka 04 Jul 2023 22:34

Here is the promised reference measurement of the card used for the measurements: https://obrazki.elektroda.pl/2831165000_1688501807_thumb.jpg And as for the price with the NE5532 used. As I mentioned,... [Read more]

pikarel 05 Jul 2023 15:20

This is real DIY, in an exemplary execution; that's what the DIY department is for. Now we are waiting for posts that will expose "non-compliance of the device made with the standards", buddy @tytka... [Read more]

austriackimalarz 05 Jul 2023 16:04

Who was calling me? ;) I really like this experiment. Generally, connecting several amplifiers in parallel eliminates noise, but ... without exaggeration ;P Maybe it's worth using amplifiers in SOT23-5... [Read more]

lechoo 05 Jul 2023 21:52

Can you reveal what you modified in UMC202HD to get such good parameters? [Read more]

rb401 05 Jul 2023 21:55

I strongly warn against using these cubes and others from the LM321, 358, 324 group in this construction. It's just that in these amplifiers, in applications where the output current changes direction,... [Read more]

tytka 05 Jul 2023 22:09

@lechoo I limited the input path of this card to a minimum, because as it turns out, the factory Midas input amplifiers are a total flop and the reason for the imperfection of this card. I described my... [Read more]

marweg1967 06 Jul 2023 01:36

Will your colleague reveal details about this security? Input diodes? Because this Behringer really hums badly and I'm getting ready to etch the board to use the workaround described by a colleague... [Read more]

kamil.b 06 Jul 2023 14:09

It is conceptually similar to this project: Headphone amplifier based on NE5532 Quite a neat design (both the author's and Phil's from the movie) [Read more]

austriackimalarz 06 Jul 2023 20:29

Thanks for the information, I didn't know about that. I'm thinking... Let's give 4 sets of amplifiers powered from +-22V, let's connect them into 2 separate bridges. This would give 44Vpeak,... [Read more]

rb401 07 Jul 2023 00:20

This cube is basically the same as the LM358 and has the same characteristic of these specific distortions as this whole family. So it is definitely not suitable for this construction. [Read more]

austriackimalarz 07 Jul 2023 00:47

This generally looks like a feature of BJT-based amplifiers. Versions based on JFET transistors do not have such problems. [Read more]

FAQ

TL;DR: A 64-op-amp output stage delivers 2 × 14 W into 8 Ω while “cooling is essential” [Elektroda, tytka, post #20640831] Listeners report detailed, uncoloured sound; chips sit at 45-50 °C during use [Elektroda, tytka, post #20640831]

Why it matters: The project shows how commodity NE5532s can form a practical, if power-hungry, hi-fi amplifier.

Quick Facts

• Output power: 14 W RMS per channel into 8 Ω, dual-mono [Elektroda, tytka, post #20640831] • Op-amps per channel: 69 (4 VAS + 64 buffer + 1 servo) [Elektroda, tytka, post #20640831] • Quiescent temperature: 45–50 °C at ±18 V supply [Elektroda, tytka, post #20640831] • Quiescent current (1000-amp variant): approx. 2.2 A per channel at ±18 V [Elektroda, w3501yyyy, post #20841410] • Parts cost: NE5532P ≈ PLN 1.9 each at TME (2023) [Elektroda, tytka, post #20642244]

Why use dozens of NE5532 op-amps instead of power transistors?

Paralleling many op-amps raises output current, lowers noise by √N, and bypasses bias-setting hassles. The 64-device buffer supplies enough current for 14 W while the voltage-gain op-amps keep distortion low [Elektroda, tytka, post #20640831] "You gain low noise without quiescent-current trim," notes rb401 [Elektroda, rb401, post #20643524]

How is thermal management handled?

All amplifiers mount on a single-sided PCB fixed to an aluminium heat-spreader; stabiliser LM338s and the op-amps reach 45–50 °C. Active cooling is recommended for continuous high-power use [Elektroda, tytka, post #20640831] An edge case shows 1000-amp blocks idling at 60 W and running dangerously hot without a case [Elektroda, w3501yyyy, post #20840893]

How noisy is the amplifier?

At 1 W output, THD+N measured 0.006 % and dynamic range about 102 dB with asymmetrical sound-card measurement; reference card noise floor is −110 dB [Elektroda, mkpl, post #20641108] Parallel op-amps drop equivalent input noise to ≈0.335 nV/√Hz for 2000 devices, though diminishing returns apply [Elektroda, Urgon, post #20654463]

Can I bridge the two channels for more power?

Yes, Douglas Self’s original Elektor design allowed bridging; the simplified build omits it. Re-adding balanced inputs and phase inversion lets you reach roughly 4× the single-ended power, so ≈56 W into 8 Ω using the same ±18 V rails [Self, 2010].

Which op-amps are NOT recommended?

Avoid LM358/324/2904 families; their push-pull stages lack quiescent current, causing a brief output “dead zone” and heavy distortion when paralleled [Elektroda, rb401, post #20643524]

How do I add input-stage protection to a Behringer UMC202HD after modding?

Tytka adds anti-series 5.1 V Zeners across the input to clamp transients, plus 1 kΩ series resistors. He reports no added noise after the fix [Elektroda, tytka, post #20713510]

How can I replicate the 64-buffer channel quickly?

  1. Solder 8-pin NE5532Ps into precision sockets on a single-sided PCB.
  2. Tie all outputs through 0.1 Ω resistors to a common node.
  3. Mount the completed board to a finned heatsink with thermal paste. Keep inter-amp trace lengths equal to maintain phase coherence [Elektroda, tytka, post #20641066]

What happens if I oversize the output capacitor of the LM338 regulator?

Using 2200 µF instead of the recommended 1 µF degrades transient response and may trigger regulator oscillation, as noted by Terminus [Elektroda, terminus, post #20656289]

Could class-D op-amps solve the heat issue?

Class-D monolithic drivers exist, but audio-grade, low-noise duals remain rare and expensive. Expect wider availability and parity pricing within ten years [Elektroda, katakrowa, post #20658155]

Is there a commercial future for this concept?

Participants suggest an SMD SOIC build screwed directly to a heatsink for a compact module. Cost, thermal load, and regulatory testing remain barriers, yet small headphone-amp variants already ship from some Chinese vendors [Elektroda, Urgon, post #20652784]
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