How to Design and Build an Amplifier With the TDA2050

PCBs for this challenge are out there right here.

Word: This tutorial may even work with the TDA2030 so long as you retain the availability voltage beneath ±18 V.

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The TDA2050 is a good sounding chip amplifier with a lot of energy. On this tutorial, I’ll stroll you by means of the amplifier design course of as I construct a 25 Watt stereo amplifier with the TDA2050. First, I’ll present you calculate the voltage and present necessities of your energy provide, and present you ways discover a correctly sized warmth sink. Then, I’ll present you discover the precise values for all the elements within the circuit. I’ll additionally present you change the achieve, and set the bandwidth of the amplifier. Lastly, I’ll focus on PCB design and wiring the amplifier inside an enclosure. The data builds on itself, so it’s finest to observe alongside so as. However if you wish to leap forward to a specific matter, listed below are hyperlinks to the sections in this text:

BONUS: Obtain my elements checklist to see the elements I used to get good sound high quality from this amplifier. I’ve additionally included the Gerber information and schematic for the facility provide I used.

The datasheet is an efficient reference to have when constructing any amplifier. I like to recommend studying it earlier than beginning on this challenge:

Circuit Basics PDF Icon TDA2050 Datasheet

WARNING!! THIS PROJECT INVOLVES HIGH VOLTAGES THAT CAN CAUSE SERIOUS INJURY OR DEATH. BE SURE TO USE PROPER SAFETY PRECAUTIONS, AND NEVER WORK ON A LIVE CIRCUIT.

You can even watch this video for an summary of the design course of. On the finish of the video I wire up the amp and play some music so you may hear what it appears like:

What to Know Earlier than Beginning

Earlier than you start, you’ll wish to get an thought of how a lot output energy you need from the amplifier. You’ll additionally have to know the impedance of your audio system and the enter voltage of your audio supply. Be sure you verify the TDA2050’s datasheet to search out absolutely the most scores for these parameters, and design your amp to remain inside the protected working limits.

In response to the datasheet, the TDA2050 can output 28 Watts into Four Ω audio system with 0.5% distortion on a 22 V energy provide. I’ll be powering 6 Ω audio system with my amplifier, so I’m going to goal for about 25 Watts output energy. I’ll be utilizing an iPhone because the audio supply, which has a 1 V output voltage.

Step one is to determine how a lot voltage and energy you want from the facility provide to get your required output energy.

Energy Provide Voltage and Present

The TDA2050 will be powered from a break up provide or single provide. The amplifier’s output energy can be increased with a break up provide, in order that’s what I’ll use right here.

Energy Provide Voltage

Your required output energy and speaker impedance will decide how a lot voltage you want from the energy provide. However earlier than we are able to calculate the facility provide voltage, we have to calculate the amplifier’s peak output voltage (Vopeak).

Peak Output Voltage

The height output voltage will be discovered with this system:

V_{opeak} = sqrt{2times R_{L}times P_{o} } R_{L} = Speakerhspace{1mm}impedance P_{o} = Averagehspace{1mm}outputhspace{1mm}power

The height output voltage of my 25 Watt amplifier driving 6 Ω audio system can be:

V_{opeak} = sqrt{2times 6 hspace{1mm}Omegatimes 25hspace{1mm}W} = sqrt{300} = 17.3hspace{1mm}V

So with an output energy of 25 Watts, the utmost voltage on the audio system can be 17.Three V.

Most Provide Voltage Wanted by the Amplifier

Now you can discover the utmost provide voltage (Vmax provide), which is the voltage your amp must get your required output energy. The provision voltage restrict of the TDA2050 is ±25 V, so ensure to not exceed that.

The system to calculate the most provide voltage is:

V_{max supply} = pm( V_{opeak}+ V_{od})(1+Regulation)(1.1) V_{opeak}= Peak output voltage V_{od}= Voltage drop across the TDA2050 Rightarrow 4 V Regulation= Increase in voltage when transformer is unloaded 1.1= Variation in mains voltage (10 %)

Regulation is the rise in transformer output voltage when there’s no load to attract present, which occurs when the amplifier isn’t taking part in music. The precise worth ought to be given in your transformer’s datasheet. The transformer I’ll be utilizing has a regulation of 6%, so my most provide voltage is:

V_{max supply} = pm(17.3 V+4 V)(1+0.06)(1.1) =pm(21.3 V times 1.06 times 1.1) =pm24.9 V

So, my energy provide must ship ±24.9 V for my amplifier to drive 6 Ω audio system at 25 Watts. The ± image signifies that the optimistic rail voltage is +25 V and the detrimental rail voltage is -25 V.

Most Provide Voltage Supplied by a Transformer

The purpose is to discover a transformer that may output a most provide voltage near the utmost provide voltage wanted by your amplifier.

A transformer’s voltage ranking solely tells you its AC voltage output. The DC voltage you’ll get after the bridge rectifiers on the facility provide convert AC to DC will truly be increased by an element of 1.41. You’ll additionally have to account for surges in your mains provide, and the regulation of your transformer.

The most provide voltage you’ll get from a transformer will be calculated with this system:

V_{max hspace{1mm} supply}=(V_{transformer})(1.41)(1.1)(1+Regulation) V_{transformer}=Transformer hspace{1mm} voltage hspace{1mm} rating 1.41=Voltage hspace{1mm} increase hspace{1mm} across hspace{1mm} rectifier hspace{1mm} diodes 1.1= Variationhspace{1mm}inhspace{1mm}mainshspace{1mm}voltagehspace{1mm}(10hspace{1mm}%) Regulation= Increasehspace{1mm} inhspace{1mm} voltage hspace{1mm}when hspace{1mm}transformer hspace{1mm}is hspace{1mm}unloaded

I began with a transformer ranking of 15 V AC to see if that might present the utmost provide voltage wanted by my amplifier:

V_{max hspace{1mm} supply}=(15 hspace{1mm} V)(1.41)(1.1)(1+0.06) =24.7 hspace{1mm} V

So a 15 V transformer will give me a most provide voltage of 24.7 V DC after the facility provide. That’s actually near the 24.9 V most provide voltage wanted for my amplifier, however now let’s calculate precisely how a lot output energy I’ll get with it…

Amplifier Output Energy from a Transformer’s Most Provide Voltage

This calculation is helpful if you have already got a transformer and wish to see how a lot output energy your amplifier will produce with it:

P_{o}=frac{(frac{V_{cc}}{(1+Regulation)(1.1)}-V_{od})^{2}}{2times R_{L}} V_{cc}=Maximum supply voltage from  transformer V_{od}= Voltage drop across the TDA2050 Rightarrow 4 V Regulation= Increase in voltage when transformer is unloaded 1.1= Variation in mains voltage (10 %) R_{L} = Speaker impedance

The utmost provide voltage from a 15 V transformer is 24.7 V, so the output energy I’ll get from my amplifier is:

P_{o}=frac{(frac{V_{max hspace{1mm} supply}}{(1+Regulation)(1.1)}-V_{od})^{2}}{2times R_{L}} P_{o}=frac{(frac{24.7 hspace{1mm} V}{(1+0.06)(1.1)}-4 hspace{1mm} V)^{2}}{2times 6 hspace{1mm} Omega} =frac{(frac{24.7 hspace{1mm} V}{1.166}-4 hspace{1mm} V)^{2}}{12} =frac{(17.2)^{2}}{12} =frac{295}{12} =24.6 hspace{1mm} W

A 15 V transformer will give me 24.6 Watts of output energy into 6 Ω audio system, and that’s shut sufficient to my desired 25 Watts.

Transformer Energy Wanted by the Amplifier

Now we are able to decide how a lot energy the transformer wants to provide the amplifier. Energy is usually given as a VA ranking within the transformer’s specs. To calculate a minimal VA ranking, we’ll first want to search out the overall energy (Psupply) the transformer wants to provide the amplifier.

The overall energy is determined by the most provide voltage you’ll get from the transformer, the amplifier’s peak output voltage, your speaker impedance, and the quiescent drain present (QDC) of the TDA2050 (90 mA):

P_{supply} = 2 times V_{cc}(frac{V_{opeak}}{pitimes R_{L}}+QDC) V_{cc}= Maximum supply voltage from transformer V_{opeak}= Peak output voltage QDC= Quiescent drain current Rightarrow 90 mA (from datasheet) R_{L}= Speaker impedance

So my 15 V transformer wants to provide not less than:

P_{supply} = 2times 24.7 hspace{1mm} V(frac{17.3hspace{1mm}V}{pitimes 6hspace{1mm}Omega}+0.09hspace{1mm}A) = 49.4times (0.92+0.09) =49.4times 1.0 =49.4hspace{1mm}W

Now we’ll use the overall energy to discover a minimal VA ranking on your transformer…

Convert Complete Energy to Transformer VA Score

To discover a minimal VA ranking on your transformer, a basic rule of thumb is to multiply the overall energy by an element of 1.5.

For my 15 V transformer, the VA ranking will must be:

49.4 W times 1.5 = 74.1 VA

That is the VA per channel. For a stereo amplifier we simply multiply by two:

74.1 VA times 2 = 148.2 VA

So something over a 150 VA transformer will provide my amplifier with sufficient energy. This good to know as a result of in case your transformer is underneath powered, the amp may clip or distort the audio at increased volumes.

Discovering the Proper Warmth Sink Dimension

The 2 channels of my amplifier hooked up to a warmth sink:

Complete TDA2050 Amplifier Design and Construction - Assembled PCBs Attached to Heat Sink

The TDA2050 must be hooked up to a warmth sink or it is going to rapidly overheat and get broken. The scale of the warmth sink you want will rely in your most energy dissipation and the thermal resistances in the trail of warmth move away from the TDA2050.

Most Energy Dissipation

The utmost energy dissipation (Pdmax) is the quantity of energy the TDA2050 will dissipate as warmth on the restrict of it’s operation. Pdmax is determined by the utmost provide voltage you’ll get along with your transformer, and the impedance of your audio system:

P_{dmax} =frac{(2times V_{cc})^{2}}{2timespi^{2}times R_{L}} V_{cc}= Maximum supply voltage from transformer R_{L}= Speaker impedance

In response to the datasheet, the TDA2050’s absolute most ranking for Pdmax is 25 Watts. If the Pdmax of your design is bigger than 25 Watts, you’ll have to decrease the provide voltage or enhance the speaker impedance to stop harm.

For the amplifier I’m constructing, the most provide voltage equipped by my transformer is ±24.7 V, and I’m driving 6 Ω audio system, so my Pdmax is:

P_{dmax} =frac{(2times 24.7  V)^{2}}{2timespi^{2}times 6 Omega} = frac{2440}{118.4} =20.6 W

A Pdmax of 20.6 Watts is beneath the TDA2050’s absolute most ranking of 25 Watts, so the whole lot appears to be like good up to now.

Most Thermal Resistance of the Warmth Sink

Now we are able to decide the utmost thermal resistance (in °C/W) of the warmth sink you have to dissipate all the energy the TDA2050 produces. However earlier than we are able to try this, we have to know the values of the three thermal resistances within the path of warmth move away from the TDA2050:

How to Design a Hi-Fi Audio Amplifier With an LM3886 - Thermal Resistance Diagram

θjc: The thermal resistance from the chip’s junction (the die) to the outside of the plastic case.

θcs: The thermal resistance from the chip’s case to the warmth sink.

θsa: The thermal resistance from the warmth sink to the ambient air.

Warmth dissipation can be extra environment friendly when any of those are made smaller. We are able to’t do something to get a decrease θjc, as a result of it is determined by the development of the TDA2050’s package deal. θcs will be lowered through the use of thermal paste between the chip and the warmth sink. The thermal resistance of thermal paste is often round 0.2 °C/W, however verify the datasheet to search out the precise worth for the kind you’re utilizing.

The biggest discount of thermal resistance will come out of your alternative of warmth sink (θsa). Warmth sink thermal resistance is often offered as a °C/W ranking within the datasheet or promoting materials. Warmth sinks with a decrease thermal resistance will dissipate extra warmth.

Use this system to calculate the warmth sink’s most thermal resistance obligatory to dissipate the TDA2050’s Pdmax:

theta_{sa} =frac{[(T_{jmax}-T_{amb})-P_{dmax}(theta_{jc}+theta_{cs})]}{P_{dmax}} T_{jmax}= Maximum junction temperature Rightarrow 150 ^{circ}C (from datasheet) T_{amb}= Ambient temperature theta_{jc}= Thermal resistance from junction to case theta_{cs}= Thermal resistance from case to heat sink P_{dmax}= Maximum power dissipation

  • The θcs of the TDA2050 is 3 °C/W.
  • Tjmax is the utmost junction temperature, or the temperature at which the thermal shutdown circuitry is enabled. Tjmax for the TDA2050 is 150 °C.
  • Tamb is the ambient temperature (in °C) whereas the amplifier is working. A typical worth is room temperature (25 °C).

The utmost thermal resistance of the warmth sink for my amplifier with a Pdmax of 20.6 Watts is:

theta_{sa} =frac{[(150hspace{1mm}^{circ}C-25hspace{1mm}^{circ}C)-20.6hspace{1mm}W(3hspace{1mm}^{circ}C/W+0.12hspace{1mm}^{circ}C/W)]}{20.6hspace{1mm}W} =frac{60.7}{20.6} =2.9hspace{1mm}^{circ}C/W

So I’ll want a warmth sink rated lower than or equal to 2.9 °C/W to make sure it is going to dissipate all the energy my amplifier produces.

Calculating the Amplifier’s Element Values

Now that every one the facility and warmth sink necessities are discovered, let’s discover one of the best values for the elements within the circuit. I’ll use the schematic beneath, which is principally the identical because the one within the datasheet, however with a couple of further elements to assist filter noise:

How to How to Design and Build a TDA2050 Audio Amplifier - Circuit Schematic

For those who click on on the picture you’ll be taken to the EasyEDA schematic editor the place you may modify the circuit and alter part values.

Right here’s a diagram of the TDA2050’s pinout on your reference:

Complete TDA2050 Amplifier Design and Construction - TDA2050 Pinout Diagram

Minimal Acquire

The achieve of the TDA2050 ought to be set above 24 db to take care of stability, however there may be additionally a minimal achieve wanted to get your required output energy. It is determined by your enter voltage, speaker impedance, and desired output energy in accordance with this system:

A_{V} geqfrac{sqrt{P_{o}times R_{L}}}{V_{in}} A_{V}= Gain V_{in}= Inputhspace{1mm}Voltage R_{L}= Speakerhspace{1mm}Impedance P_{o}= Outputhspace{1mm}Power

I’ll be utilizing an iPhone because the audio supply for my amplifier. The iPhone has an output voltage of about 1 V, so to get 24.6 W output energy, I’ll have to set the achieve to not less than:

A_{V} geqfrac{sqrt{24.6 hspace{1mm}Wtimes 6hspace{1mm}Omega}}{1 hspace{1mm}V} geqfrac{sqrt{148}}{1} geq 12.2

That is expressed because the voltage achieve (Vo/Vi), or the issue of amplification. To transform voltage achieve to decibels achieve, use this system:

Gain_{db}=20timeslog_{10}{(frac{V_{o}}{V_{i}})} =20timeslog_{10}{(12.2)} =21.7 db

So setting my achieve above 21.7 db will make sure that I get 24.6 Watts of output energy. However the minimal achieve of the TDA2050 is 24 db, so I’ll have to set it to not less than 24 db.

Set the Acquire

The values of resistors R4 and R5 set the achieve of the TDA2050:

Complete TDA2050 Amplifier Design and Construction - R4 and R5 Set the Gain

Excessive achieve settings will trigger distortion and low achieve settings might not present sufficient quantity. In case your minimal achieve worth permits for it, an excellent achieve to make use of for house listening is round 27 to 30 db. This setting isn’t excessive sufficient to trigger distortion and can give you an excellent vary of quantity.

The perfect resistors for R4 and R5 are steel movie varieties with tight tolerances. A tolerance of 0.1% or much less is excellent. It’s essential to make use of shut tolerance resistors to set the achieve, particularly if you happen to’re constructing a stereo amplifier. If the resistance values between the 2 channels are off by a couple of Ohms, the features can be completely different and one facet can be louder than the opposite.

The achieve is calculated with this system:

A_{V} = 1+frac{R5}{R4} A_{V}= Gain (frac{V_o}{V_i}) R4= Resistance of R4 in Ohms R5=Resistance of R5 in Ohms

I’ll be setting the achieve of my amplifier to round 27 db. I attempted completely different resistor values with the system above, and bought near my desired achieve with R4 at 1 kΩ and R5 at 22 kΩ. These resistances will set my achieve to:

A_{V} = 1+frac{22000hspace{1mm}Omega}{1000hspace{1mm}Omega} =1+22 =23hspace{1mm}frac{V_{o}}{V_{i}} =27.2 hspace{1mm} db

Which will work nice since 27.2 db is above the minimal achieve I calculated earlier, and above the 24 db minimal of the TDA2050.

Stability the Enter Bias Present

After setting the achieve, the following step is to steadiness your amplifier’s enter bias present. The enter bias present is the distinction in currents flowing to the non-inverting enter (pin 1) and the inverting enter (pin 2). This distinction in present must be minimized since it is going to create a DC voltage on the inputs that can be amplified as noise.

The present at inverting enter is set by the resistance of R5. The present on the non-inverting enter is set by the resistances of R2 and R3 in sequence:

Complete TDA2050 Amplifier Design and Construction - Balancing the Input Bias Currents with R2, R3, and R5

So as to make the currents at every enter the identical, we set

R2+R3 = R5

For my amplifier, I already discovered a worth for R5 once I set the achieve. For R3, I began with an arbitrary worth of 1 kΩ then rearranged the system above to discover a worth for R2:

R2+R3 = R5 R2 = R5 -R3 R2 = 22000 hspace{1mm} Omega - 1000 hspace{1mm} Omega R2 = 21000 hspace{1mm} Omega

So a 21 kΩ resistor for R2 and a 1 kΩ resistor for R3 will steadiness the enter bias present.

Set the Low Finish of the Amplifier’s Bandwidth on the Enter

Capacitor C1 prevents DC from the audio supply attending to the amplifier’s enter. If DC is allowed to succeed in the enter, it is going to get amplified together with the audio sign and create noise.

C1 additionally types a resistor-capacitor (RC) excessive cross filter with R2 that defines the low finish of the amplifier’s bandwidth:

Complete TDA2050 Amplifier Design and Construction - Set the Low Frequency Cut Off at the Amplifier's Input

A filter’s cutoff frequency (Fc) is the frequency at which the filter begins to work. In a excessive cross filter, frequencies beneath the cutoff frequency are muted.

The cutoff frequency of this filter will be discovered with this equation:

F_{c}=frac{1}{2 times pi times R2 times C1} R= Resistance of R2 in Ohms C= Capacitance of C1 in Farads

We already discovered a worth for R2 after we balanced the enter bias currents. To discover a worth for C1, we simply want to outline a cutoff frequency. For the reason that decrease restrict of human listening to is 20 Hz, the Fc ought to be nicely beneath 20 Hz in order that audible bass frequencies aren’t muted.

The Fc equation above will be rearranged to search out the worth for C1 at a specific cutoff frequency:

C1=frac{1}{2 times pi times R2 times F_{c}}

I went with an Fc of three.5 Hz for my amplifier, however you should use barely increased or decrease values if you would like. It could take some experimentation to search out the proper worth on your ears, however simply remember to keep nicely beneath the decrease restrict of human listening to (20 Hz), or your amp’s bass response can be weak.

With an Fc of three.5 Hz, the worth of my C1 is:

C1=frac{1}{2timespi times 21000hspace{1mm} Omegatimes 3.5hspace{1mm} Hz} =frac{1}{461,814} =0.0000022hspace{1mm} F =2.2hspace{1mm}mu F

C1 is instantly within the enter sign path, so it is going to have an effect on your amplifier’s sound high quality. For one of the best sound, use a polypropylene steel movie or polypropylene steel movie in oil capacitor.

Set the Low Finish of the Amplifier’s Bandwidth within the Suggestions Loop

C3 and R4 type one other excessive cross filter within the suggestions loop:

Complete TDA2050 Amplifier Design and Construction - Set the Low Frequency Cut Off of the Feedback Loop

The cutoff frequency of this filter ought to be set Three to five occasions decrease than the cutoff frequency of the enter excessive cross filter. If the cutoff frequency of this filter is increased than the filter on the enter, low frequencies can be handed to the suggestions loop filter which are beneath it’s cutoff frequency. This will create a DC voltage throughout C3 that may seem on the inverting enter and get amplified as noise.

Regardless that the enter filter units the low finish of the amplifier’s bandwidth, C3 nonetheless has an impact on the bass response. Smaller values of C3 will lead to softer bass that has much less punch, and bigger values will make the bass tighter, with extra impression.

Use the system beneath as a place to begin to search out a really perfect worth for C3:

C3geqfrac{sqrt{2}times(R2+R3)times C1}{R4}

I already calculated values of R2, R3, R4, and C1, so my C3 ought to be better than:

C3geqfrac{sqrt{2}times(21000 Omega+1000 Omega)times 0.0000022 F}{1000 hspace{1mm} Omega}  geqfrac{0.068}{1000 hspace{1mm} Omega}  geq 0.000068 F  geq 68  mu F

It’s going to be laborious to discover a 68 µF capacitor, so I’ll spherical as much as 100 µF. Let’s see what the cutoff frequency can be with that:

F_{c}=frac{1}{2 times pi times 1000hspace{1mm} Omega times 0.0001 hspace{1mm} F} =frac{1}{0.628} =1.59hspace{1mm} Hz

Now lets verify to see if 1.59 Hz is Three to five occasions decrease than the three.5 Hz Fc of my enter filter:

frac{3.5 hspace{1mm} Hz}{1.59 hspace{1mm} Hz} =2.2

It’s 2.2 occasions decrease, so perhaps we are able to do higher with a 220 µF capacitor. The Fc with a 220 µF capacitor is 0.72 Hz.

frac{3.5 hspace{1mm} Hz}{0.72 hspace{1mm} Hz} =4.9

So a worth of 220 µF for C3 units the cutoff frequency of the suggestions loop filter to 4.9 occasions decrease than the cutoff frequency of the enter filter. This can be simply nice, in order that’s what I’ll use.

Set the Excessive Finish of the Amplifier’s Bandwidth

R1, R3, and C2 type a low cross RC filter on the amplifier’s enter that defines the excessive finish of the amplifier’s bandwidth:

Complete TDA2050 Amplifier Design and Construction - Set the High Frequency Cut Off at the Amplifier's Input

In a low cross filter, frequencies above the cutoff are muted. This filter has two features. One, it units the higher restrict of the amplifiers’s bandwidth, and two, it filters excessive frequency radio and electromagnetic interference from the audio enter.

The cutoff frequency of this filter ought to be better than the 20 kHz higher restrict of human listening to. It also needs to be decrease than any radio broadcast frequencies which may be picked up by the enter wires and traces.

The bottom radio broadcast frequency within the USA is AM at 535 kHz. I made a decision on a cutoff frequency of 350 kHz, which is nicely beneath 535 kHz and nicely above the 20 kHz higher restrict of human listening to.

To search out the worth of C2 with an Fc of 350 kHz, I rearranged the cutoff frequency system to resolve for C2:

F_{c}=frac{1}{2pi (R1+R3)C2}Rightarrow C2=frac{1}{2pi (R1+R3)F_{c}} C2=frac{1}{2times pi times (1000 hspace{1mm} Omega + 1000 hspace{1mm} Omega)times 350000 hspace{1mm} Hz} =frac{1}{4.4 times 10^{9}} =2.27 times 10^{-10}hspace{1mm} F =227 hspace{1mm} pF

227 pF isn’t a typical capacitor worth. Nonetheless, 220 pF would give an cutoff frequency of 362 kHz, so that may work nice as an alternative.

The Zobel Community

A Zobel community helps to stop oscillation that may happen from the parasitic induction of speaker wires. It additionally acts as a filter to stop radio interference picked up by the speaker wires from attending to the inverting enter by way of the suggestions loop.

C4 and R6 type a Zobel community on the amplifier’s output:

Complete TDA2050 Amplifier Design and Construction - The Zobel Network

Since capacitors have a really low impedance at excessive frequencies, radio frequencies are shorted to floor by way of C4. R6 limits the excessive frequency present so there isn’t a direct brief to floor, which might exceed the present restrict of the TDA2050. The comparatively low frequency audio present is blocked by C4, so it’s directed out to the audio system.

The cutoff frequency of the Zobel community will be calculated with:

F_{c}=frac{1}{2 times pi times R6 times C4} R6= Resistance of R6 in Ohms C4= Capacitance of C4 in Farads

The datasheet offers values for R6 = 10 Ω and C4 = 100 nF, which supplies an Fc of:

F_{c}=frac{1}{2 times pi times 10 Omega times (1 times 10^-7 F)} =frac{1}{0.0000063} =159 kHz

159 kHz is above the 20 kHz restrict of human listening to and nicely beneath radio frequencies, so these values will work nice.

If the amplifier oscillates, R6 can be passing excessive currents to floor so it ought to have an influence ranking of not less than 1 Watt. C4 ought to ideally be a steel movie capacitor with a low ESR, and a voltage ranking better than the rail to rail output swing.

Energy Provide Decoupling Capacitors

Complete TDA2050 Amplifier Design and Construction - Power Supply Decoupling Capacitors

C5 to C10 are the facility provide decoupling capacitors. They act as a reservoir of present that may be rapidly equipped to the amplifier when wanted. There’s one set of decoupling capacitors for every voltage provide pin.

The bigger worth decoupling capacitors (C9 and C10) present reserve present throughout prolonged durations of low frequency output. Bigger values will enhance the bass response of the amplifier.

The smaller worth decoupling capacitors (C6 and C5) can provide reserve present quickly for durations of intense excessive frequency output. They additionally filter excessive frequency noise and electromagnetic interference from the facility provide.

Decoupling capacitors additionally compensate for the inductance and resistance of the energy provide wires and traces main to the chip. Inductance and resistance inhibit present move, and for the reason that major energy provide is comparatively far-off from the TDA2050, the impact will be important. Finding the decoupling capacitors as shut as doable to the chip’s pins will maximize present move to the chip.

The perfect varieties of capacitors to make use of may have a decrease equal sequence resistance (ESR) and equal sequence inductance (ESL).

Grounding the Amplifier

Grounding is among the most essential points of amplifier design. A poor grounding format is usually a main supply of hum and buzzing. A superb grounding format retains the low present audio enter and sign grounds separate from the excessive present energy provide and speaker grounds. If excessive currents are allowed to move by means of the low present grounds, a DC voltage will develop within the low present wires that may present up at the enter and get amplified as hum.

To maintain the completely different grounds separate, we’ll create a number of completely different floor networks:

  • Audio enter floor: For the bottom wire of the audio enter cable
  • Sign floor: For the enter circuit: R2, C2, and C3
  • Speaker floor: For the speaker return wires
  • Energy floor: For the facility provide decoupling capacitors and the Zobel community

These grounds will connect with a bunch of terminals known as the principle system floor. The principle system floor is linked to a floor loop safety circuit (I’ll clarify extra about this later), which then connects to the mains earth wire by way of the steel chassis.

The principle system floor ought to be positioned as shut as doable to the reservoir capacitors on the facility provide:

How to Design a Hi-Fi Audio Amplifier With an LM3886 - Grounding Diagram

The bottom networks are linked to the principle system floor in a specific order so that top currents solely move by means of the low present grounds for a really brief distance. As proven within the diagram above, the bottom loop safety circuit connection is closest to the reservoir capacitors and the enter floor connection is the farthest away.

PCB Structure and Design

I designed the PCB for my amplifier utilizing EasyEDA’s on-line PCB design software program. EasyEDA is a full suite schematic and PCB design software program/manufacturing service that’s free to make use of and gives nice costs on customized PCB manufacturing. To edit the format, change part footprints, and order the PCB, click on on the picture beneath:

Complete TDA2050 Amplifier Design and Construction - PCB Layout

The part labels on the PCB match the labels within the schematic

This PCB is for a single channel, so if you happen to’re constructing a stereo amplifier you’ll have to construct two boards. If you’d like some tips about designing PCBs and a tutorial on utilizing EasyEDA, try our article Tips on how to Make a Customized PCB.

PCB Ordering

For those who click on on the “Fabrication Output” button within the PCB editor window, you’ll be taken to a web page the place you may order the PCB. You’ll even be given selections for copper thickness, PCB thickness, colour, order amount, and different parameters:

Complete TDA2050 Amplifier Design and Construction - Ordering the PCB

I ordered 5 PCBs and the associated fee got here to $17.10 USD. Manufacturing and delivery took about 10 days. The boards got here out nice. The traces are routed exactly and all the printing may be very clear. Right here’s one of many boards after manufacturing:

Complete TDA2050 Amplifier Design and Construction - PCB Top

Complete TDA2050 Amplifier Design and Construction - PCB Bottom

PCB Design Suggestions

There are 4 primary ideas I took under consideration when designing this PCB:

  • Present flowing by means of a conductor creates a magnetic discipline that may generate a present in a parallel conductor
  • Present flowing in a conductive loop creates a magnetic discipline, and a magnetic discipline generates a present in a conductive loop. The magnitude of the present is proportional to the realm contained in the loop
  • Inductance inhibits the move of present. Lengthy, skinny traces have extra inductance than brief, thick traces
  • A capacitor in sequence with an inductor creates a resonant circuit

The traces resulting in the non-inverting enter and suggestions loop have been routed far-off from the facility provide and audio output traces to stop excessive currents producing currents in low present traces. If routing a low present hint close to a excessive present hint is unavoidable, run them at 90° angles, however by no means parallel. For those who put the terminals for the excessive and low present circuits on reverse sides of the PCB, will probably be simpler to route them far-off from one another.

Any house between traces of the identical circuit will create a conductive loop that’s vulnerable to receiving or transmitting magnetic fields. To keep away from this, I’ve routed the optimistic and detrimental energy provide traces shut to one another, and used floor planes on the underside of the PCB. When traces are routed over a floor aircraft, the width of the loop is diminished to the thickness of the PCB.

For the reason that energy floor and sign floor must be saved separate, the underside facet of the PCB has two floor planes that aren’t linked electrically. One floor aircraft carries the facility floor, and the opposite floor aircraft carries the sign floor. On the highest facet of the PCB, the facility provide traces, output, and Zobel community are routed over the facility floor aircraft. The enter and suggestions loop traces are routed over the sign floor aircraft.

A capacitor in sequence with an inductor creates a resonant circuit, which might trigger oscillation. Inductance additionally inhibits the move of present. To cut back the consequences of inductance, it’s finest to maintain all traces as brief as doable. That is particularly essential for the energy provide decoupling capacitors, the suggestions loop, and the Zobel community. They’ve all been positioned as shut as doable to the chip’s pins to shorten the hint size.

Constructing the Amplifier

Assembling the PCB is fairly straight ahead. Right here are the elements and PCB earlier than soldering:

Complete TDA2050 Amplifier Design and Construction - Unassembled Amp

It’s often best to solder the smaller elements first, then work your approach as much as greater elements. I exploit a putty known as Sticky-Tac to carry elements in place on the highest of the PCB whereas soldering from the underside facet.

For those who can, use 63/37 eutectic solder as a substitute of 60/40 tin lead solder. Eutectic solder has a smaller melting vary which makes the solder bond set quicker and offers a stronger bond. The melting vary of 60/40 solder is pretty large, and it turn into pasty at on the decrease finish of the vary. If a part is moved within the pasty part, the joint can be weak and should type a chilly solder joint.

It’s additionally a good suggestion to make use of some nice grit sandpaper to take away any oxidation from the part leads earlier than soldering.

Right here’s one channel of my amplifier after I soldered the elements:

Complete TDA2050 Amplifier Design and Construction - Assembled Amp

The Amplifier Enclosure/Chassis

Metallic enclosures are essentially the most generally used as a result of they provide one of the best shielding from fluorescent gentle, radio frequency, and cellular phone interference. It may be laborious to search out one that matches although. I like to recommend the enclosures from Hello-Fi 2000, an organization in Italy that has stunning enclosures out there in a lot of completely different sizes. The web site is in Italian, however you may change the language to English. In addition they do customized printing, engraving, and drilling. I ordered their 330 mm X 280 mm Galaxy enclosure with a 10 mm black anodized aluminum entrance panel and it appears to be like nice:

Complete TDA2050 Amplifier Design and Construction - The Amplifier Chassis

However if you happen to’re on a funds, their financial system line appears to be like actually good too. The Economica 280 mm x 250 mm mannequin would match the stereo TDA2050 amplifier too:

Complete TDA2050 Amplifier Design and Construction - The Chassis

Wiring the Amplifier

The diagram beneath reveals how I wired my amplifier collectively contained in the chassis:

How to Design a Hi-Fi Audio Amplifier With an TDA2050 - Master Wiring Diagram

Click on on the picture to view a bigger model

To keep away from interference from magnetic fields, attempt to maintain the delicate enter and sign wires far-off from the facility provide wires, speaker output wires, transformer, AC mains wires, and rectifier diodes on the facility provide.

To reduce the loop space, the next wires ought to be tightly twisted collectively for as lengthy a distance as doable:

  • AC scorching and AC impartial wires to transformer
  • Zero V and secondary voltage wires from transformer to energy provide
  • V+, V-, and energy floor wires from energy provide to amplifier PCB
  • Speaker output and speaker floor
  • Audio enter and audio enter floor

Three energy provide wires (optimistic, detrimental, and energy floor) run to every amplifier PCB. These wires ought to be thick and as brief as doable to reduce the inductance. I used 14 AWG, however something bigger than 18 AWG ought to be nice.

The audio enter and sign floor wires don’t carry lots of present to allow them to be skinny gauge. Stable core 22 AWG works very well and is straightforward to twist collectively.

For fault present safety, the mains earth wire ought to be secured to the chassis with a bolt, lock nut, and a hoop terminal. Make sure that to scrape off any paint or anodization from the chassis to get a good electrical connection. All steel elements (like the warmth sinks) also needs to be electrically linked to the chassis.

The audio enter floor and speaker grounds are wired instantly from the terminals on the chassis to the principle system floor.

Audio enter cables from the supply can choose up stray electromagnetic interference. To filter this out, you may set up a 1 nF capacitor at every enter terminal, from the optimistic facet to floor.

The Floor Loop Safety Circuit

Complete TDA2050 Amplifier Design and Construction - Ground Loop Protection Circuit Assembled PCB

A floor loop is a present that flows from the audio supply to the amplifier by means of the bottom protect of the audio enter cables. This present can be picked up on the amplifier’s enter and produce an annoying hum. You’ll be able to use an additional circuit positioned between the principle system floor and the chassis connection to interrupt the bottom loop present:

How to Design a Hi-Fi Audio Amplifier With an LM3886 - Ground Protection Circuit Schematic

NOTE: THIS CIRCUIT MAY NOT BE LEGAL IN YOUR AREA. PLEASE CHECK YOUR LOCAL ELECTRICAL CODES OR CONSULT AN ELECTRICIAN BEFORE USING A GROUND LOOP BREAKER

Below regular working circumstances, low voltage floor loop currents move by means of the resistor (R1). The resistor reduces this present and breaks the bottom loop. If a excessive present fault happens, the fault present can move by means of the diode bridge to earth. The capacitor filters any radio frequencies picked up by the chassis.

The principle system floor connects to the bottom loop safety circuit on the “PSU 0V” terminal. The bottom loop safety circuit then connects to the chassis from the “Chassis” terminal. The connection to the chassis will be on the identical bolt the place the mains earth wire connects, or at one other spot.

If you utilize a floor loop safety circuit, remember to isolate all enter and output connectors from the chassis. In any other case, there can be a direct path from the principle system floor to the chassis and the bottom loop safety circuit can be bypassed completely.

The bottom loop safety circuit will be laborious wired, but it surely’s slightly neater to mount the elements to a PCB:

How to Design a Hi-Fi Audio Amplifier With an LM3886 - Ground Protection Circuit PCB Layout

Click on on the picture to edit the format, change part footprints, and order PCBs.

How Does it Sound?

General, the amp sounds nice. The bass, mids, and treble are all very clear and nicely balanced. It additionally has loads of energy. There’s greater than sufficient quantity for listening in my lounge. There isn’t any hum or noise whereas the amp is powered on and plugged into the supply.

Whereas the sound high quality of the TDA2050 might not be as much as par with our Hello-Fi LM3886 amplifier challenge, it nonetheless sounds actually good. If that is your first amplifier construct, I’d counsel beginning with our TDA2003 stereo or bridged amplifier initiatives since they’re fairly a bit simpler to construct.

Be sure you go away a remark in case you have any questions, and be at liberty to share this publish if anybody that might discover it helpful! Thanks for studying…

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