Hello,
I hope there hasn't been too many similiar threads like this before, but I'm looking for suggestions for an power amplifier to build. My own expertise is mainly speaker building, but I want to extend my hobby to amplifiers as well.
I'm not a total novice with electronics, so far I've built Millett Hybrid headphone amplifier, 41Hz AMP6 and Millett SoundCard Interface. All Of these work just fine and I've had very little problems building them. I've been reading about audio electronics from books and internet and I can build devices from good instructions, but I really can't design anything by myself, or even fully understand what happens in the circuits.
At the moment I'm using Pioneer VSX-1015 AV amplifier and naturally I would like to build something potentially higher quality for stereo listening. Later I would also like to make a pre-amplifier with remote controller and D/A converters, but I'd like to begin with the power amplifier as it is probably more simple to build.
Some requirements for the amp:
- It needs to be able to drive easily 4ohm load with no problems.
- Class AB. Class A sounds intriguing, but I guess it will be too expensive to build. A very good quality AB amp should be just fine in my case.
- Transistor, FET/MOSFET, OpAmp, I can't really say anything to this as I have very little knowledge about the differences. Tubes are out of question. Apparently my Pioneer uses MOSFETs.
- I'm living in a single, so I don't need that much power output, although my speakers aren't that sensitive (4ohm 85-86dB/2,83V). I believe 20-80W to 4ohm would be sufficient. It's really hard to estimate how much power is actually even used in my case, probably not much.
- I would also like to order a ready-made PCB and I need clear instructions and preferably pictures of a complete amp to ease the project. This doesn't mean that I'm looking for extremely simple circuit, a huge pile of components doesn't scare me away. Whole point of this project is to make something by my own and learn more. Too simplified circuits aren't that interesting.
I'm hoping for few good suggestions that meets my requirements, so I can take a better look for those designs and choose what pleases me the most. Thanks for anyone who can give suggestions with good arguments.
-Ari S
I hope there hasn't been too many similiar threads like this before, but I'm looking for suggestions for an power amplifier to build. My own expertise is mainly speaker building, but I want to extend my hobby to amplifiers as well.
I'm not a total novice with electronics, so far I've built Millett Hybrid headphone amplifier, 41Hz AMP6 and Millett SoundCard Interface. All Of these work just fine and I've had very little problems building them. I've been reading about audio electronics from books and internet and I can build devices from good instructions, but I really can't design anything by myself, or even fully understand what happens in the circuits.
At the moment I'm using Pioneer VSX-1015 AV amplifier and naturally I would like to build something potentially higher quality for stereo listening. Later I would also like to make a pre-amplifier with remote controller and D/A converters, but I'd like to begin with the power amplifier as it is probably more simple to build.
Some requirements for the amp:
- It needs to be able to drive easily 4ohm load with no problems.
- Class AB. Class A sounds intriguing, but I guess it will be too expensive to build. A very good quality AB amp should be just fine in my case.
- Transistor, FET/MOSFET, OpAmp, I can't really say anything to this as I have very little knowledge about the differences. Tubes are out of question. Apparently my Pioneer uses MOSFETs.
- I'm living in a single, so I don't need that much power output, although my speakers aren't that sensitive (4ohm 85-86dB/2,83V). I believe 20-80W to 4ohm would be sufficient. It's really hard to estimate how much power is actually even used in my case, probably not much.
- I would also like to order a ready-made PCB and I need clear instructions and preferably pictures of a complete amp to ease the project. This doesn't mean that I'm looking for extremely simple circuit, a huge pile of components doesn't scare me away. Whole point of this project is to make something by my own and learn more. Too simplified circuits aren't that interesting.
I'm hoping for few good suggestions that meets my requirements, so I can take a better look for those designs and choose what pleases me the most. Thanks for anyone who can give suggestions with good arguments.
-Ari S
The Leach Amp seems to be a good fit to your bill. It was well designed by Dr. Marshall Leach (R.I.P.) and was well documented. Many people DIY built it with satisfactory result in the past decades, and many of them are still in service. There are ready made PCB designs available, just checkout the group buy from time to time. Since some of the semiconductors used in the original design have become harder and harder to find, people have come up with PCB designs employing modern devices, and have yielded excellent builds, as far as I know. These designs are using more output transisters (at least 3 pairs per channel) than Dr. Leach's design aiming at most difficult possible speaker loads. Do a simple forum search with keyword Leach, and you'll get tons of info.
I built my own version of The Leach Amp myself and have driven a pair of PSB Stratus Gold-i with it for almost a year with nothing but excellent performance. These are 4-ohm floorstanders and have a low-ish sensitivity simmilar as that of yours. I designed my own PCBs and employed 5 pairs of output transistors per channel. I have never tried Dr. Leach's PCB design that employs 2 pairs of transisters per channel on my speakers, but I believe it would handle the speakers of this kind with ease.
I built my own version of The Leach Amp myself and have driven a pair of PSB Stratus Gold-i with it for almost a year with nothing but excellent performance. These are 4-ohm floorstanders and have a low-ish sensitivity simmilar as that of yours. I designed my own PCBs and employed 5 pairs of output transistors per channel. I have never tried Dr. Leach's PCB design that employs 2 pairs of transisters per channel on my speakers, but I believe it would handle the speakers of this kind with ease.
Thank you for your reply.
The leach amp sounds interesting, but the power output seems excessive for my usage. 500VA transformer and huge heatsinks will cost quite a lot, especially here at Finland. I understood that the leach can be made with half the output power which could be an option. Does this modification have any other affects to the performance than the lowered power output?
How does the P3A compare to the leach amp? It seems to be very popular as well.
-Ari S
The leach amp sounds interesting, but the power output seems excessive for my usage. 500VA transformer and huge heatsinks will cost quite a lot, especially here at Finland. I understood that the leach can be made with half the output power which could be an option. Does this modification have any other affects to the performance than the lowered power output?
How does the P3A compare to the leach amp? It seems to be very popular as well.
-Ari S
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Joined 2009
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This question does come up from time to time, the 'what should I build'. This forum has pretty much all the answers you need - but it really needs a 'sticky' thread or a wiki table of the options for people to refer to. It would help a lot of people.
I believe the P3A is a good choice of amp to build and rod elliot has a number of supporting projects like the power supply and speaker protection that you could also add as you enlarge your project.
If you are willing to make your own pcb and it isn't that hard, there are a lot of other good choices such as any of the DX amplifiers.
Be warned - this hobby is addictive !
I believe the P3A is a good choice of amp to build and rod elliot has a number of supporting projects like the power supply and speaker protection that you could also add as you enlarge your project.
If you are willing to make your own pcb and it isn't that hard, there are a lot of other good choices such as any of the DX amplifiers.
Be warned - this hobby is addictive !
Check out the LM60 Mosfet amps from Ampslab. Everything you need in a kit, comes with pictures and assembly instructions. All you need is a power supply and a box. You can easily build the amp in about two hours and get it ready for mounting.
Sounds very nice and puts out about 60 watts into 4 ohms. Oh, do put the transistors on a LARGE heatsink, Mosfets dump a lot of heat as they are not as efficient as bipolars.
Sounds very nice and puts out about 60 watts into 4 ohms. Oh, do put the transistors on a LARGE heatsink, Mosfets dump a lot of heat as they are not as efficient as bipolars.
& for fun!I would recommend the Blame series amplifiers by "Destroyer". 50w 8ohm, 100w 4ohm. Very low distortion. Search for 'Blame ST' or 'Blame Supercharged' if you want twice the power.
Greg's Web Site
Regards
Niss_man
Greg's Web Site
Regards
Niss_man
I've had some time to dig into these suggested amplifiers and any of these should fit my use just fine. Before creating this thread I looked at the earlier posts and Dx Amp, Leach and P3A was often discussed and recommended so I believe these are all fine choices. I just got to pick my own favorite 😀 And then look more into that.
What wonders me, is that the power supplys seem to be un-regulated. Is this typical? I was slightly confused about the PS schematics where output voltage is lower that I first reasoned, but if I understood right, the output voltage depends if the amp is driving a load or not.
For example this schematic:
http://sound.westhost.com/p3a-f2.gif
The transformer is connected to produce 50Vac, right? And the actual DC voltages from the rectifier is 35V when connected to a load? I am still slightly confused about this.
That suggested P3A PS seems very simplified to the comparable Dx PS:
http://www.nabucoeletronica.com.br/dx/files/dx-psu-schematic.pdf
Less is more?
How does the PS output voltage change at no load at all, normal load and heavy load? I understand that the DC voltage isn't flat if the capacitors can't handle the required power, but how does the transformer step into this.
What wonders me, is that the power supplys seem to be un-regulated. Is this typical? I was slightly confused about the PS schematics where output voltage is lower that I first reasoned, but if I understood right, the output voltage depends if the amp is driving a load or not.
For example this schematic:
http://sound.westhost.com/p3a-f2.gif
The transformer is connected to produce 50Vac, right? And the actual DC voltages from the rectifier is 35V when connected to a load? I am still slightly confused about this.
That suggested P3A PS seems very simplified to the comparable Dx PS:
http://www.nabucoeletronica.com.br/dx/files/dx-psu-schematic.pdf
Less is more?
How does the PS output voltage change at no load at all, normal load and heavy load? I understand that the DC voltage isn't flat if the capacitors can't handle the required power, but how does the transformer step into this.
Unregulated power supplies are typical - the power amp circuits have enough PSRR to reject a good deal of the ripple. Instantaneous energy delivery is more important here.
There is *some* benefit to feeding the small signal stages of a power amp from a seperate, regulated supply, but it is a complex affair.
The Dx PSU you link to does include a number of fancy extras - it mainly comprises of a C-R-C filter to improve the supply quality.
There is *some* benefit to feeding the small signal stages of a power amp from a seperate, regulated supply, but it is a complex affair.
The Dx PSU you link to does include a number of fancy extras - it mainly comprises of a C-R-C filter to improve the supply quality.
Hi,
a single secondary with 25Vac when open circuit will charge a capacitor to [25 * sqrt(2) - rectifier voltage drop] at near zero current.
This will be the DC voltage measured at the capacitor when no load is connected.
As you increase the current demand, voltage ripple starts to develop on the capacitor.
The peak voltage stays fairly close to the no current voltage, but the rectifier voltage drop goes from ~1V to ~1.4V. The minimum of the ripple can be many volts below peak. This gives an average voltage at the smoothing cap of 25*sqrt(2) - rectifier voltage drop when delivering current = 50% * the Vripple at the capacitor.
The effect of this is that the 25Vac (opencircuit) does ~34.3Vdc. Increase the current to 100mA and the voltage will drop to ~33.5Vdc with a small ripple voltage. Increase the current to 1A and the voltage will fall to ~32Vdc with an even higher ripple voltage.
A dual secondary 25+25Vac transformer can give a dual polarity DC supply after it has passed through a parallel pair of rectifiers and smoothing capacitors.
That's where your confusion is beginning.
A centre tapped secondary of 50Vac is more often referred to a 25-0-25Vac (a total of 50Vac across the series connected windings). It is capable of creating a +ve 35Vdc supply and a -ve 35Vdc supply. This is referred as dual polarity when the two supplies are series connected to give +-35Vdc
The 25Vac transformer gives a 35Vdc supply
The CT 50Vac transformer gives two supplies each of 35Vdc.
a single secondary with 25Vac when open circuit will charge a capacitor to [25 * sqrt(2) - rectifier voltage drop] at near zero current.
This will be the DC voltage measured at the capacitor when no load is connected.
As you increase the current demand, voltage ripple starts to develop on the capacitor.
The peak voltage stays fairly close to the no current voltage, but the rectifier voltage drop goes from ~1V to ~1.4V. The minimum of the ripple can be many volts below peak. This gives an average voltage at the smoothing cap of 25*sqrt(2) - rectifier voltage drop when delivering current = 50% * the Vripple at the capacitor.
The effect of this is that the 25Vac (opencircuit) does ~34.3Vdc. Increase the current to 100mA and the voltage will drop to ~33.5Vdc with a small ripple voltage. Increase the current to 1A and the voltage will fall to ~32Vdc with an even higher ripple voltage.
A dual secondary 25+25Vac transformer can give a dual polarity DC supply after it has passed through a parallel pair of rectifiers and smoothing capacitors.
That's where your confusion is beginning.
A centre tapped secondary of 50Vac is more often referred to a 25-0-25Vac (a total of 50Vac across the series connected windings). It is capable of creating a +ve 35Vdc supply and a -ve 35Vdc supply. This is referred as dual polarity when the two supplies are series connected to give +-35Vdc
The 25Vac transformer gives a 35Vdc supply
The CT 50Vac transformer gives two supplies each of 35Vdc.
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This amp has received very good reviews - bugger all componentry and low cost...ideal for first timer.
http://www.diyaudio.com/forums/solid-state/2654-digi-125-kit-amplifier-module.html
Eric.
http://www.diyaudio.com/forums/solid-state/2654-digi-125-kit-amplifier-module.html
Eric.
post has a broken link.
That's why we should use DIYaudio for our references. They won't break links to themselves.
That's why we should use DIYaudio for our references. They won't break links to themselves.
mrfeedback, i hope thats a joke 🙂
ESP P3A or one of Destroyer X's amps is a good start. Be warned the hobby is addictive 🙂
ESP P3A or one of Destroyer X's amps is a good start. Be warned the hobby is addictive 🙂
I've got three books about electronics and all of those have only basic information about rectifiers and none of the presented examples had center tapped transformers fully explained. Thanks for clearing this up for me, although I still don't understand, how does the output voltage rise after connecting the capacitor? I understand that it smoothens the DC voltage and the the diodes inside the rectifier lower the voltage, but I can't understand how does it affect the output voltage.
Are the +/- voltages for the amplifier to work in B class, amplifying the positive and negative side of the output?
Are the two voltage outputs in a center tapped transformer in different phase?
I am very grateful that people are so willing to help even though I make quite stupid questions 😛 I work with car interiors and have no education in electronics, but I've been very fascinated with audio electronics for years. This is a great educational hobby and it's also great that even beginners are noticed.
Are the +/- voltages for the amplifier to work in B class, amplifying the positive and negative side of the output?
Are the two voltage outputs in a center tapped transformer in different phase?
I am very grateful that people are so willing to help even though I make quite stupid questions 😛 I work with car interiors and have no education in electronics, but I've been very fascinated with audio electronics for years. This is a great educational hobby and it's also great that even beginners are noticed.
Symmetrical wave containing single frequency, with positive and negative side. (?)
-Ari
I guess the capacitors work like a toilet tank..... you can't hose your toilet very clean as there is only that much water flow out of the supply line, so you store it up into a tank that can put out a huge dump.🙂
Good.
The maximum voltage of the sinewave at the "peak" of the waveform is Vpk.
The heating effect coming from applying that sinewave to a heater is not comparable to the DC voltage heating effect if the DC voltage = Vpk.
We use a special term to define a voltage that has the same heating effect as a DC voltage. We term it Vrms That is a precise methodology applied to measuring any AC waveform to determine it's heating effect.
For the moment stick with sinewaves.
The 10Vdc volt displayed on an oscilloscope will be a flat line that when "measured" looks like 10Volts on the screen.
A 10Vrms sinewave displayed on the same screen will be that wiggle you have seen.
If you "look" at the screen you can "measure" the wiggle. This is the voltage from peak to peak (vertical not horizontal which is a time measurement).
Vpp is the term used.
The height of the peak voltage above zero volts is Vpk and for a sinewave is exactly = Vpp/2. For that same 10Vrms sinewave you will find that measuring the voltage on the screen that Vpk = sqrt(2) * Vrms and that Vpp = 2 * sqrt(2) * Vrms.
DC=10V, AC = 10Vrms, sinewave = 14.14Vpk, sinewave = 28.28Vpp, all describe a voltage that have identical heating effect.
Now back to your enquiry.
The secondary winding gives an AC waveform that is fairly close to a sinewave. It is corrupted by various effects and becomes quite distorted by the time the power is delivered to your home.
Let's for the sake of simplicity, assume your secondary delivers an exact sinewave with no distortion and no interference.
If you have 25Vrms then you now know it has the same heating effect as 25Vdc, and you also know that the top of the waveform is at a voltage of sqrt(2) * 25Vrms = 35.35534Vpk and that will show as 70.71Vpp on the oscilloscope.
The capacitor that comes after the rectifier (one way valve for electricity) gets fed with this wiggly voltage. If the capacitor is at a lesser voltage than what comes out of the rectifier, the capacitor will charge up, not instantly, but over a very short time period. Because of the rectifier, the capacitor cannot discharge back into the secondary when the wiggly voltage drops.
The capacitor stores the charge.
Next time the voltage rises to near the peak of the waveform, current will flow through the rectifier to charge the capacitor some more, for as long as the supply voltage is higher than the capacitor voltage. This repeats over a few cycles of the waveform.
The first half wave might charge up the capacitor to 80% of Vpk, the next half cycle would then charge up to ~96%, the third cycle will charge it to ~99%, until the capacitor reaches ~ 99.99% of the Vpk available after passing through the rectifier.
As the cap reaches full charge the current that flows to top up the last few tenths of a percent of full charge creates a small voltage drop in the secondary winding and causes a small voltage drop across the rectifier.
The end result is that the cap charges to ~25Vac * sqrt(20) - one or two diode voltage drops. A normal silicon diode usually drops 600mV to 800mV depending on how much current is passing.
A diode that is passing almost zero current drops a far lower voltage, I expect to see Vdrop ~500mV This is different from Vf, the specified Vdrop for the diode at a fixed test temperature and at a fixed test current.
Expect open circuit voltage on the cap to be ~34.35Vdc after passing through the two diodes of a bridge rectifier.
We have not multiplied any voltage, the capacitor has stored the peak voltage available after the Vdrop of the rectifier.
If you use one bridge rectifier across the whole centre tapped secondary, each half voltage stored in the two smoothing capacitors will be ~500mV higher, or ~34.86Vdc
The maximum voltage of the sinewave at the "peak" of the waveform is Vpk.
The heating effect coming from applying that sinewave to a heater is not comparable to the DC voltage heating effect if the DC voltage = Vpk.
We use a special term to define a voltage that has the same heating effect as a DC voltage. We term it Vrms That is a precise methodology applied to measuring any AC waveform to determine it's heating effect.
For the moment stick with sinewaves.
The 10Vdc volt displayed on an oscilloscope will be a flat line that when "measured" looks like 10Volts on the screen.
A 10Vrms sinewave displayed on the same screen will be that wiggle you have seen.
If you "look" at the screen you can "measure" the wiggle. This is the voltage from peak to peak (vertical not horizontal which is a time measurement).
Vpp is the term used.
The height of the peak voltage above zero volts is Vpk and for a sinewave is exactly = Vpp/2. For that same 10Vrms sinewave you will find that measuring the voltage on the screen that Vpk = sqrt(2) * Vrms and that Vpp = 2 * sqrt(2) * Vrms.
DC=10V, AC = 10Vrms, sinewave = 14.14Vpk, sinewave = 28.28Vpp, all describe a voltage that have identical heating effect.
Now back to your enquiry.
The secondary winding gives an AC waveform that is fairly close to a sinewave. It is corrupted by various effects and becomes quite distorted by the time the power is delivered to your home.
Let's for the sake of simplicity, assume your secondary delivers an exact sinewave with no distortion and no interference.
If you have 25Vrms then you now know it has the same heating effect as 25Vdc, and you also know that the top of the waveform is at a voltage of sqrt(2) * 25Vrms = 35.35534Vpk and that will show as 70.71Vpp on the oscilloscope.
The capacitor that comes after the rectifier (one way valve for electricity) gets fed with this wiggly voltage. If the capacitor is at a lesser voltage than what comes out of the rectifier, the capacitor will charge up, not instantly, but over a very short time period. Because of the rectifier, the capacitor cannot discharge back into the secondary when the wiggly voltage drops.
The capacitor stores the charge.
Next time the voltage rises to near the peak of the waveform, current will flow through the rectifier to charge the capacitor some more, for as long as the supply voltage is higher than the capacitor voltage. This repeats over a few cycles of the waveform.
The first half wave might charge up the capacitor to 80% of Vpk, the next half cycle would then charge up to ~96%, the third cycle will charge it to ~99%, until the capacitor reaches ~ 99.99% of the Vpk available after passing through the rectifier.
As the cap reaches full charge the current that flows to top up the last few tenths of a percent of full charge creates a small voltage drop in the secondary winding and causes a small voltage drop across the rectifier.
The end result is that the cap charges to ~25Vac * sqrt(20) - one or two diode voltage drops. A normal silicon diode usually drops 600mV to 800mV depending on how much current is passing.
A diode that is passing almost zero current drops a far lower voltage, I expect to see Vdrop ~500mV This is different from Vf, the specified Vdrop for the diode at a fixed test temperature and at a fixed test current.
Expect open circuit voltage on the cap to be ~34.35Vdc after passing through the two diodes of a bridge rectifier.
We have not multiplied any voltage, the capacitor has stored the peak voltage available after the Vdrop of the rectifier.
If you use one bridge rectifier across the whole centre tapped secondary, each half voltage stored in the two smoothing capacitors will be ~500mV higher, or ~34.86Vdc
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Oh, I was never aware of AC RMS value. I thought all the time that the sine peak = AC voltage, that's what was confusing me all the time! So the capacitor will load up to the sine peak voltage, which is higher than the AC rms. Thanks 🙂
Look at the amp design here: 60 Watt MosFet Audio Amplifier - RED - Page100
this is a design with some similar parameters to what you described.
Also look for the book(s) "The High Power Audio Amplifier Construction Manual" (and/or) "The Audiophiles Project Sourcebook" both by G. Randy Sloan (R.I.P.) both offer loads of info on design and construction of audio equipment and useful schematics to build your own. They are available worldwide so use Google or your choice of search engines and type the titles and author in and you should find them. HIGHLY RECOMMENDED for budding audio DIYers
this is a design with some similar parameters to what you described.
Also look for the book(s) "The High Power Audio Amplifier Construction Manual" (and/or) "The Audiophiles Project Sourcebook" both by G. Randy Sloan (R.I.P.) both offer loads of info on design and construction of audio equipment and useful schematics to build your own. They are available worldwide so use Google or your choice of search engines and type the titles and author in and you should find them. HIGHLY RECOMMENDED for budding audio DIYers
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