logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

Power amplifier on NE5532 - ty.ytka

tytka 21117 79

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.
Generated by the language model.
ADVERTISEMENT
Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
Report a violation of the law
Reply Cool? Ranking DIY | New topic
Notify about new articles
📢 Listen (AI):
  • #31 20653115
    austriackimalarz
    Level 26  
    Posts: 996
    Help: 83
    Rate: 266
    marweg1967 wrote:
    One channel for about 4 k PLN? Well, Lord, it's almost high-end. Something just in time for another block to the resurrected Unitra.
    By the way, I wonder how it would look during blind listening compared to the work of the author of the topic.

    Unfortunately, the right OP-AMPs are expensive :c
    Without offending other designs of the mentioned author, it seems to me that such a device would work quite well. Think about it - is it better to use single power transistors with medium parameters, but with adequate power, or to use a bucket of small transistors in parallel? Is it better to put one large 10000uF capacitor somewhere on the edge of the board, or instead have a thousand 10uF ceramic SMDs, one per op-amp?
    Is it better to run currents on narrow paths with high inductance, or use copper fields with 20 PCBs with power elements as paths?
    The author's design is stupid, incredibly impractical when it comes to the approach to building an amplifier. This is the extreme of all the principles of building this type of system. But I want one too. I'm at the design stage :) Assuming +/-18V and 120W into 8 ohms :D
  • ADVERTISEMENT
  • #32 20653457
    nyquist
    Level 26  
    Posts: 1240
    Help: 76
    Rate: 192
    austriackimalarz wrote:
    (...) incredibly impractical when it comes to the approach to building an amplifier (...)

    That's right.
    austriackimalarz wrote:
    The author's design is stupid (...)

    But I personally don't agree with that. The unconventional solution used in the project is actually impractical and unprofitable, which makes it rather a curiosity, but by no means stupid.
  • #33 20653467
    austriackimalarz
    Level 26  
    Posts: 996
    Help: 83
    Rate: 266
    nyquist wrote:
    but by no means is it stupid

    It's stupid. But it works. So it's not stupid.
    I ordered 2,000 SOP8 amplifiers yesterday, and 4,000 2.2uF capacitors yesterday. You won't guess why :)
  • #34 20653475
    nyquist
    Level 26  
    Posts: 1240
    Help: 76
    Rate: 192
    austriackimalarz wrote:
    It's stupid. But it works. So it's not stupid.

    Exactly ;)
    Sorry for the little OT, but it reminded me of...
    " When everyone knows something is impossible, someone who doesn't know it comes along and he does it - Albert Einstein
  • #35 20653536
    yogi009
    Level 43  
    Posts: 14693
    Help: 848
    Rate: 2650
    austriackimalarz wrote:

    I ordered 2,000 SOP8 amplifiers yesterday, and 4,000 2.2uF capacitors yesterday. You won't guess why :)


    You'll be making a radio station for a Russian alligator :-)
  • #36 20653537
    austriackimalarz
    Level 26  
    Posts: 996
    Help: 83
    Rate: 266
    yogi009 wrote:
    You'll be making a radio station for a Russian alligator

    Exactly :) I will connect the amplifiers in series to withstand 400V power supply :P

    EDIT:
    Hello hello, stop for a moment. Not in SOP8, just plain SOT-23. I'm going to connect 500 of them in parallel, and then the whole thing into a stereo bridge connection :)
  • #37 20653543
    yogi009
    Level 43  
    Posts: 14693
    Help: 848
    Rate: 2650
    This and the tuning capacitor are made of 300 small air capacitors connected in series :-) About 5 meters of the axis will come out :-)
  • ADVERTISEMENT
  • #38 20653549
    austriackimalarz
    Level 26  
    Posts: 996
    Help: 83
    Rate: 266
    yogi009 wrote:
    This and the tuning capacitor make 300 small air capacitors connected in series About 5 meters of axis will come out

    ABOUT! And I'll pull the whole thing into a plastic hose and fill it with oil. Then I will be able to roll up such a hose-capacitor, I will immediately solve the choke issue :)
  • #39 20653558
    yogi009
    Level 43  
    Posts: 14693
    Help: 848
    Rate: 2650
    austriackimalarz wrote:

    ABOUT! And I'll pull the whole thing into a plastic hose and fill it with oil. Then I will be able to roll up such a hose-capacitor, I will immediately solve the choke issue :)


    I had a different plan. 5 meters of capacitor just enters the alligator and does not interfere with the propellers :-)
  • #40 20653573
    Urgon
    Level 38  
    Posts: 7250
    Help: 197
    Rate: 2630
    AVE...

    Better to take a few hundred 1N4007 diodes and use them as varicaps. acc. notes capacitance 5-~30pF per diode at voltages from 100mV to 100V. It is enough to connect them in parallel in a large enough number. Make a ladder out of it, then fold it into a double helix - it'll be electronic DNA...
  • #41 20653575
    yogi009
    Level 43  
    Posts: 14693
    Help: 848
    Rate: 2650
    Urgon wrote:
    Make a ladder out of it, then fold it into a double helix - it'll be electronic DNA...


    Ba, but how to carve 21 amino acids out of it?
  • ADVERTISEMENT
  • #42 20653704
    dipol
    Level 34  
    Posts: 2598
    Help: 168
    Rate: 259
    Similar wcz modules / cubes are in radio and television transmitters - commercial systems. I think our Program 1 / Warsaw I-Solec Kujawski has such lower power modules that after summing up - the combiner - give power to the antenna / en many / hundred kilowatts. Ease of servicing, automatic shuts down the damaged one turns on the reserve one, etc.
    73!
  • #43 20653708
    Urgon
    Level 38  
    Posts: 7250
    Help: 197
    Rate: 2630
    AVE...

    Standard construction method for high power transmitters. The only "problem" is that you have to assemble the whole thing in such a way that all the power amplifiers are connected "in phase" - the transmission lines, both those going to the inputs of the amplifiers and the output ones, must have the same length. It also works the other way around - in radio astronomy, many smaller antennas are combined into one phase-synchronized assembly - the apparent diameter of such an assembly is much larger than the diameter of a single antenna...
  • #44 20653757
    dipol
    Level 34  
    Posts: 2598
    Help: 168
    Rate: 259
    Urgon - as you write - m/other power adders are used for this, I have a simple solution in my radio/shortwave transceiver.
  • #45 20654167
    marweg1967
    Level 15  
    Posts: 159
    Help: 2
    Rate: 47
    Urgon wrote:
    You can use the SOIC version and do it on a double sided board. All circuits on one side, other components in the SMD variant on the other. Then, grease the amplifiers with thermal paste and screw the entire plate to the heatsink ...

    tytka wrote:
    If a commercial version were to be created, such a solution should be seriously considered.


    All in all, I'm thinking about such a solution (on NE5532, not OPA), although mainly due to the lower cost of ICs, and that it would also solve the cooling problem, so much the better.

    Added after 12 [minutes]:

    austriackimalarz wrote:
    Without offending other designs of the mentioned author, it seems to me that such a device would work quite well. Think about it - is it better to use single power transistors with medium parameters, but with adequate power, or to use a bucket of small transistors in parallel?
    ...
    The author's design is stupid, incredibly impractical when it comes to the approach to building an amplifier. This is the extreme of all the principles of building this type of system.


    Well, in higher power amplifiers, output transistors were quite commonly connected in parallel, both BJTs and MOSFETs.

    I wouldn't call the project stupid by any means. Unconventional - yes. Is it incredibly impractical? On the one hand, the construction itself can, even if so many legs are connected in parallel, on the other - there is no need to regulate the quiescent current, for example :)
  • #46 20654363
    austriackimalarz
    Level 26  
    Posts: 996
    Help: 83
    Rate: 266
    marweg1967 wrote:
    on the other - there is no need to regulate the quiescent current, for example

    And this is a huge disadvantage of this solution. It is true that in a small scale, as in the case of a titty, the sum of the quiescent currents of the amplifiers will not be large, although larger than in the typical AB class;
    NE5532P has Icc with parameters No load, Vo=0, Vcc=+-15V around 8mA (max 16mA). They are connected 64 in parallel, so the total quiescent current of the final stage is as much as half an amp, and a maximum of 1A in the worst case scenario.
    Meanwhile, in my case, one op-amp with the same parameters has catalog currents of 1.4-2.5mA, and since there will be 2,000 of them, we get a beautiful 2.8-5A!!!
  • #47 20654385
    nyquist
    Level 26  
    Posts: 1240
    Help: 76
    Rate: 192
    austriackimalarz wrote:
    Yesterday I ordered 2,000 amplifiers in SOP8 (...)

    Just out of curiosity, also 5532 or something else?
  • #48 20654388
    austriackimalarz
    Level 26  
    Posts: 996
    Help: 83
    Rate: 266
    nyquist wrote:
    Just out of curiosity, also 5532 or something else?

    austriackimalarz wrote:
    Hello hello, stop for a moment. Not in SOP8, just plain SOT-23. I'm going to connect 500 of them in parallel, and then the whole thing into a stereo bridge connection

    We settled on the TL071HIDBVR, which is the well-known TL071 in the SOT-23 housing. On the TI website, 2000 units cost about 100 euros, also bearable.
  • #49 20654398
    Urgon
    Level 38  
    Posts: 7250
    Help: 197
    Rate: 2630
    AVE...

    It's only 150W, don't whine. The stereo amplifier on the GU81M takes more for the glow current alone ...

    By the way, generally parallel connection of op-amps is practiced to reduce self-noise, not for greater current efficiency. From the latter we have transistors...
  • #50 20654409
    austriackimalarz
    Level 26  
    Posts: 996
    Help: 83
    Rate: 266
    Urgon wrote:
    By the way, generally parallel connection of op-amps is practiced to reduce self-noise,

    Meanwhile, in post 12:
    austriackimalarz wrote:
    Generally, connecting several amplifiers in parallel eliminates noise, but ... without exaggeration ;P

    Urgon wrote:
    It's only 150W, don't whine. The stereo amplifier on the GU81M takes more for the glow current alone ...

    150W is enough for one lamp to glow :)
  • ADVERTISEMENT
  • #51 20654463
    Urgon
    Level 38  
    Posts: 7250
    Help: 197
    Rate: 2630
    AVE...

    If you connect N amplifiers in parallel, the noise power of a single amplifier is divided by N, and the equivalent input noise voltage is divided by √N.
    Example: by connecting two TL071s in parallel you will reduce the noise floor from 15nV/√Hz to 10.6nV/√Hz, so by connecting 2000 devices you will gain 0.335nV/√Hz.
    For the audio band, this will give a noise voltage of 47.4nVp-p, bearing in mind that a single TL072 is 2.12µVp-p...
  • #52 20654573
    marweg1967
    Level 15  
    Posts: 159
    Help: 2
    Rate: 47
    austriackimalarz wrote:
    NE5532P has Icc with parameters No load, Vo=0, Vcc=+-15V around 8mA (max 16mA). They are connected 64 in parallel, so the total quiescent current of the final stage is as much as half an amp, and a maximum of 1A in the worst case scenario.
    Meanwhile, in my case, one op-amp with the same parameters has catalog currents of 1.4-2.5mA, and since there will be 2,000 of them, we get a beautiful 2.8-5A!!!

    I didn't say anything about the size of this current, only that it doesn't need to be regulated.
    Are you 5A you say? Well, while I described the whole project as unconventional, I would similarly define the number of cubes in your version of this project as unconventional. That is, such unconventionality squared ;)

    Added after 8 [minutes]:

    austriackimalarz wrote:
    We settled on TL071HIDBVR, which is the well-known TL071


    Why exactly TL071? If not NE, then why not TL074? It would be 4 times cheaper, at least according to Mouser's price list.
  • #53 20654593
    austriackimalarz
    Level 26  
    Posts: 996
    Help: 83
    Rate: 266
    marweg1967 wrote:
    Why exactly TL071? If not NE, then why not TL074? It would be 4 times cheaper, at least according to Mouser's shader.

    You took up the topic of profitability in the topic of building power amplifiers on operational amplifiers.
    I don't think you thought your question through :)
  • #54 20654601
    marweg1967
    Level 15  
    Posts: 159
    Help: 2
    Rate: 47
    austriackimalarz wrote:
    marweg1967 wrote:
    Why exactly TL071? If not NE, then why not TL074? It would be 4 times cheaper, at least according to Mouser's shader.

    You took up the topic of profitability in the topic of building power amplifiers on operational amplifiers.
    I don't think you thought your question through :)

    I thought: since you have already spared the money for the TL071, then by switching to the TL074 you would improve the noise parameters twice for free :D
  • #55 20654604
    austriackimalarz
    Level 26  
    Posts: 996
    Help: 83
    Rate: 266
    Possible.
    But I don't want to redesign the board :P
  • #56 20654612
    marweg1967
    Level 15  
    Posts: 159
    Help: 2
    Rate: 47
    austriackimalarz wrote:
    Possible.
    But I don't want to redesign the board :P

    And who hasn't thought this through? ;)
    I keep my fingers crossed for the success of your crazy... uh, unconventional project :D

    But I will tell you that if I did not consider TL at all, using the TL074 now seems to me an interesting option. Because of course I also want to commit this project, as I mentioned before. But I would rather close myself in dozens of integrated circuits, and electronics in a not very tight housing without transformer oil :D

    BTW: interesting nickname ;)
  • #57 20656289
    terminus
    Level 21  
    Posts: 416
    Help: 29
    Rate: 169
    #20640831
    You should not use such a large capacitance (2200 µF) at the output of linear stabilizers, it greatly deteriorates their parameters.
    In this case (LM338) 1 µF is enough on the output.
  • #58 20657278
    yogi009
    Level 43  
    Posts: 14693
    Help: 848
    Rate: 2650
    austriackimalarz wrote:
    It ended on TL071HIDBVR


    I do not know how with such an application, but listening tests showed a significant qualitative advantage (in terms of sound) of the NE5532 (TI) or even the LM833 over the TL07x series. A separate topic is the quality of the loudspeaker drivers on which we are to make the comparison. It's always the bottleneck in the puzzle that counts.

    Added after 1 [minutes]:

    Urgon wrote:
    paralleling op-amps is practiced to reduce self-noise, not to increase current efficiency


    And that's the essence of these types of projects.

    Added after 9 [minutes]:

    marweg1967 wrote:
    using the TL074 now seems to me an interesting option


    I wouldn't get into quad dice for several reasons. Cooling, crosstalk, the ability to replace the circuit with another (here double opamps give the widest possibilities). From the point of view of the lowest noise, a single circuit would seem optimal, but its application is slightly less convenient, and the surface of the PCB increases. So it seems that compromise dual op-amps are commonly chosen for a reason.

    I also think that you can compare the parameters of such a system with something dedicated and more powerful. In the scale of headphone amplifiers, the LME series from TI is used (e.g. LME49860 + LME49600 buffer - or maybe it is enough to multiply such a buffer?). The lack of capacitors separating the successive stages is tempting ... I am curious about the differences between one and the other approach.
  • #59 20658126
    katakrowa
    Level 23  
    Posts: 902
    Help: 9
    Rate: 854
    To make it modern, it begs to be built on op amps in class D ;-)
    I wonder when these will be widely available and at prices comparable to classic ones.
  • #60 20658137
    austriackimalarz
    Level 26  
    Posts: 996
    Help: 83
    Rate: 266
    katakrowa wrote:
    To make it modern, it begs to be built on op amps in class D
    I wonder when these will be widely available and at prices comparable to classic ones.

    Weak.
    I would suggest converting some polyphase converter from the GPU power supply to the amplifier :)
Reply Cool? Ranking DIY | New topic
Notify about new articles
📢 Listen (AI):
Report a violation of the law

Topic summary

✨ The discussion revolves around the construction of a power amplifier using the NE5532 operational amplifier, achieving a power output of 2×14 W at 8 ohms. The project, inspired by Douglas Self's article in Elektor magazine, is described as an experimental endeavor rather than a commercial product. Participants share insights on the design, including the use of a uPC1237 for protection and LM338 for voltage regulation. Various contributors express interest in replicating the project, discussing the challenges of sourcing components, particularly the NE5532, and the implications of using clones versus originals. The conversation also touches on measurement techniques, noise reduction through parallel connections of op-amps, and the practicality of such designs in audio applications. Some participants suggest alternative components and configurations, while others highlight the potential for high power outputs with larger setups.
Generated by the language model.

FAQ

TL;DR: “It sounds quite detailed,” and the builder measured 2×14 W into 8 Ω from a power amplifier made with parallel NE5532 op-amps. This FAQ helps DIY audio builders understand the topology, measurements, thermal limits, part choices, and why this experiment works despite its obvious inefficiency. [#20640831]

Why it matters: This thread shows how a seemingly impractical op-amp array can become a usable audio power stage, while exposing the real limits in cooling, idle power, measurement method, and device selection.

Option What the thread says Main trade-off
NE5532P Used in the featured build; 2×14 W into 8 Ω; praised for clean, detailed sound Higher chip count and heat [#20640831]
TL07x Considered for very large SMD builds; lower current per amp in some variants Questions about output resistance and suitability [#20654388]
LM833 Mentioned as sonically stronger than TL07x in listening tests Not developed into a full build here [#20657278]
LM358/LM324/LM2904 family Explicitly warned against for this push-pull output use Output crossover “dead” zone harms performance [#20643524]

Key insight: Paralleling op-amps can lower noise and raise output current, but in this thread the limiting factors were not headline wattage. They were idle dissipation, regulator heat, measurement method, and the output-stage behavior of the chosen op-amp family.

Quick Facts

  • The finished amplifier used three boards: one PSU/protection board with ±18 V rails, plus two channel boards; each channel had 4 op-amps in voltage gain, 64 op-amps in parallel as the output buffer, and 1 op-amp for the DC-servo. [#20640831]
  • The builder reported 2×14 W into 8 Ω with both channels driven, and the op-amps themselves reached about 45–50 °C during operation, so cooling was identified as mandatory for practical use. [#20640831]
  • The chosen parts were TI NE5532P devices bought from TME for under 1.9 gross per piece at the project quantity, which kept the experiment financially plausible despite the large chip count. [#20642244]
  • A later large-scale variant showed the thermal penalty clearly: 250 TL072 packages connected in parallel per block drew about 1 A at ±18 V at idle, meaning a 1000-op-amp amplifier could waste roughly 60 W before delivering signal. [#20840893]

How was this NE5532 power amplifier built to deliver 2×14 W into 8 Ω using so many op-amps in parallel?

It used many small op-amp stages to share the output job. Each channel had 4 op-amps in the voltage amplifier, 64 op-amps in parallel as the output buffer, and 1 more op-amp for the DC-servo. A separate board provided stabilized ±18 V rails and loudspeaker protection, and the whole amplifier was split across three PCBs. The builder simplified the original Elektor-inspired concept by removing balanced inputs and bridge mode, then measured 2×14 W into 8 Ω with both channels driven. [#20640831]

What is a DC-servo in an audio power amplifier, and why was an extra op-amp used for it in each channel?

A DC-servo is a control circuit that corrects output DC offset without putting a large capacitor in the audio path. The builder used one extra op-amp per channel for this function, separate from the 4 gain-stage op-amps and the 64 parallel output devices. “DC-servo” is an audio correction circuit that monitors slow DC error at the amplifier output, injects a compensating signal, and keeps the speaker near 0 V without altering normal audio-band gain. That choice fits a design built for direct-coupled listening tests. [#20640831]

Why does paralleling dozens of NE5532 op-amps reduce noise, and how does that differ from using them to increase output current?

Paralleling op-amps reduces equivalent input noise by averaging many uncorrelated noise sources, while also letting many outputs share load current. One commenter quantified the noise effect: with N devices in parallel, noise voltage falls by √N, so 2 TL071s drop from 15 nV/√Hz to 10.6 nV/√Hz, and 2000 devices reach about 0.335 nV/√Hz. The same topology can also raise output current, but another commenter stressed that noise reduction is the classic reason for this technique, not power drive. [#20654463]

What measurement setup was used for this amplifier, and how do asymmetrical and differential load measurements change the results?

The amplifier was measured asymmetrically, not differentially, and that matters. One commenter warned that asymmetrical measurement creates a ground loop through the interface output, amplifier, load return, and interface input ground. He reported that switching configuration improved the noise result from 102 dB dynamic range to 110 dB. A practical check is: 1. measure the audio interface alone, 2. compare asymmetrical and differential load wiring, 3. confirm where the measurement floor sits before judging the amplifier. [#20641108]

How was the Behringer UMC202HD modified to get better reference measurements, and what was wrong with the stock Midas input stage?

The interface was modified by stripping the input path down to a minimum because the stock Midas input amplifiers were described as the main weakness. The builder said those factory input amps were “a total flop” and the reason the UMC202HD underperformed as a measurement front end. After the modification, he also added input protection because he had already burned one AD8694 on the input stage. The thread does not list the full schematic here, but it clearly states the rationale and the failed part. [#20643545]

Where can you buy a working uPC1237 loudspeaker protection IC today, and what risks come with sourcing it from China?

The builder bought a working uPC1237 from China and said that only Chinese sources now seem to produce these chips. He also warned that buying them there involves risk, so the thread treats availability as possible but uncertain. The practical takeaway is simple: you can still source uPC1237-based protection, but expect authenticity and consistency risk when the supply chain is limited to Chinese sellers. [#20641164]

Why do LM321, LM358, LM324, and LM2904-family op-amps perform poorly in this kind of parallel push-pull audio output stage?

They perform poorly here because their output stage can momentarily “die” when output current changes direction. One commenter explicitly warned against LM321, LM358, LM324, and related parts for this topology, and later explained that the problem comes from a push-pull output stage with no quiescent current. That creates a switching interval between the upper and lower transistor, which shows up as distortion. Another commenter then confirmed LM2904AQTH behaves like LM358 in this respect and is therefore unsuitable for this amplifier style. [#20645984]

NE5532 vs TL07x vs LM833 for an op-amp power amplifier: which one makes more sense for sound quality, noise, and current draw?

In this thread, NE5532 is the safest proven choice, TL07x is a scalable experiment, and LM833 is praised mainly on listening quality. The finished amplifier used TI NE5532P and was judged clean and detailed, while one commenter said listening tests gave NE5532 or even LM833 a clear quality advantage over TL07x. For current draw, another large-scale build using TL072 showed the downside clearly: 250 packages per block drew about 1 A at ±18 V at idle. That makes TL07x attractive for packaging experiments, but not automatically for efficiency. [#20657278]

What is damping factor in a loudspeaker amplifier, and why might TL071 or TL072 output-stage resistance reduce it in a parallel op-amp design?

Damping factor is the amplifier’s ability to control speaker motion through low output impedance. One commenter warned that older TL07x-family behavior can add substantial effective output resistance because the final stage includes emitter resistors and another resistor in series with the op-amp output. “Damping factor” is a loudspeaker-control metric that compares load impedance to amplifier output impedance, so a lower output impedance gives tighter electrical control over the driver, especially at low frequencies. In a parallel speaker-driving array, that extra resistance can limit both output power and damping factor. [#20666706]

How do you estimate transformer size, idle power loss, and heatsinking for a large parallel-op-amp amplifier running on ±18 V?

Start with idle current first, because it dominates the thermal budget. In one large TL072 example, 250 packages per block drew about 1 A at ±18 V, so a 1000-op-amp amplifier could waste about 60 W at idle. Another commenter estimated that a stereo bridge design at this scale would need roughly a 400 W transformer, while even a smaller stereo variant could need about 150 W and dissipate up to 90 W in the ICs at idle. That is why the thread repeatedly treats heatsinking and airflow as design requirements, not accessories. [#20841106]

Why did the author use LM338 stabilizers and large output capacitors, and how could 2200 µF on an LM338 output affect regulator performance?

The builder used LM338 stabilizers to create the amplifier’s regulated ±18 V rails and credited the strong bass partly to PSU quality. A later commenter challenged one detail and said 2200 µF on the LM338 output is too large, arguing that it worsens regulator behavior and that 1 µF is enough at the output in this case. So the thread presents both views: the regulated supply helped listening impressions, but very large output capacitance on LM338 may degrade regulator performance rather than improve it. [#20656289]

What is a bridge amplifier configuration, and how would bridging large blocks of TL072 or TL071 op-amps change voltage swing and output power?

A bridge amplifier drives the load from two opposite-phase outputs, doubling voltage swing across the speaker. In the thread, one builder described using two 250-TL072 blocks to form one bridge, then two bridges for stereo. Another commenter estimated about 110 W per channel into 4 Ω in that kind of stereo bridge arrangement and said a transformer around 400 W would then be appropriate. The thread also notes a real limit: output swing loses several volts versus the rails, so bridge power is high but not idealized. [#20841399]

How should you cool a commercial-style version of this amplifier built with SOIC or SMD op-amps on a double-sided PCB?

Mount the op-amps on one side, place the remaining SMD parts on the other, apply thermal paste, and bolt the PCB to a heatsink. That was the specific commercial-style suggestion made in the discussion for a SOIC or SMD version. The idea matters because the original through-hole build already heated the op-amps to about 45–50 °C, and larger arrays showed even worse idle dissipation. The proposed double-sided board turns the whole PCB into a heat-spreading interface instead of relying on free air alone. [#20652784]

What kind of input protection can be added to a modified UMC202HD after burning an AD8694, and how do Zener diodes compare with anti-parallel diode strings or JFETs used as diodes?

The thread points to clamp-style protection, but it does not fully settle the best device choice. The builder said he added protection after burning an input AD8694, then later linked updated information using Zener-based protection. Another commenter said he had expected either anti-parallel strings of 3–4 ordinary diodes or JFETs used as diodes, and asked whether the Zeners added audible noise. The thread records that question, but it does not report a measured noise penalty from the chosen Zener approach. [#20713587]

Which class D op-amp or audio amplifier models already sound indistinguishable from analog in the audio band, as mentioned in the discussion?

No specific class D op-amp or amplifier model was named in the discussion. One commenter claimed such devices already exist today and said they are still single-phase designs switching around 300–500 kHz rather than at megahertz frequencies. When another participant asked for a model number, none was provided in the quoted thread. So the only reliable answer here is that the claim was made, but no concrete product was identified. [#20658147]
Generated by the language model.
ADVERTISEMENT