One of the things I love about the LM3886 poweramp chip is that it puts out no transient at all during turn-on or turn-off. This makes it usable for direct connection to a delicate expensive tweeter in a multi-amp'd arrangement (biamp, triamp, etc.). I built a 4 channel 3886 amp which puts out 50watts rms into an 8 ohm load with a +/- 32 volt powersupply. I'm very happy with it and want to build another.
Any preamp that doesn't have good tone controls seems foolish to me. I highly recommend a 4 section Baxandall tone control circuit.
Those speaker protection and soft start boards seem like just more to go wrong, and shouldn't be needed. You might also want to add a clip indicator LED, so you know when not to turn the volume up more.
Linkwitz used this chip in his earlier version of the Pluto active bi-amp'd speaker system. He's very smart and very picky. I used his circuit as a reference, but then messed with the phase margin caps to get that optimized. That's something that's significantly affected by physical layout.
Here's a link to my website. click on audio, then scroll down to the 3886 project.
opalcreekaudio.com
Any preamp that doesn't have good tone controls seems foolish to me. I highly recommend a 4 section Baxandall tone control circuit.
Those speaker protection and soft start boards seem like just more to go wrong, and shouldn't be needed. You might also want to add a clip indicator LED, so you know when not to turn the volume up more.
Linkwitz used this chip in his earlier version of the Pluto active bi-amp'd speaker system. He's very smart and very picky. I used his circuit as a reference, but then messed with the phase margin caps to get that optimized. That's something that's significantly affected by physical layout.
Here's a link to my website. click on audio, then scroll down to the 3886 project.
opalcreekaudio.com
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Hi Bob,
I find the lack of speaker protection inexcusable. Relays are about the best what to go, and if you have to replace it every 10 years, so what? That's just maintenance. There are some new types of speaker protection that uses Mosfet transistors. I have to check those out. If they work well, then you have protection that never needs replacement.
There is never an excuse for lack of speaker protection. Sorry, but that is just how I feel after 35+ years of audio service.
-Chris
I find the lack of speaker protection inexcusable. Relays are about the best what to go, and if you have to replace it every 10 years, so what? That's just maintenance. There are some new types of speaker protection that uses Mosfet transistors. I have to check those out. If they work well, then you have protection that never needs replacement.
There is never an excuse for lack of speaker protection. Sorry, but that is just how I feel after 35+ years of audio service.
-Chris
I haven't had a poweramp blow a speaker since I built a SWTPC Universal Tiger from a kit when I was in highschool, in about 1970. I do use fast blow fuses on my speaker outputs, but I know they are only so protective. I haven't been able to become convinced that an "active" protection circuit with a relay would be any safer than the fuses. But I respect your opinion.
how many secondary tappings?
how many secondary windings?
BTW,
AC does not have V & 0
You have a voltage difference between the two tappings of 23Vac.
One tapping could be set to 0Vac, then it follows that the other tapping is at 23Vac.
But equally valid set one tapping to 421Vac and the other can be either 421-23 = 398Vac, or 421+23 = 444Vac.
In all three cases the voltage difference between the two tappings is 23Vac.
how many secondary windings?
BTW,
AC does not have V & 0
You have a voltage difference between the two tappings of 23Vac.
One tapping could be set to 0Vac, then it follows that the other tapping is at 23Vac.
But equally valid set one tapping to 421Vac and the other can be either 421-23 = 398Vac, or 421+23 = 444Vac.
In all three cases the voltage difference between the two tappings is 23Vac.
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Hi Bob,
That's fair enough. In my work, I often see failed equipment that generates a substantial DC offset in failure more. Some that shared your views (early Bryston for example) would lay waste to speakers in a very short amount of time. It only takes one failure to create a fire in a speaker. This is a common outcome when unprotected amplifiers suffer a failure.
Your series fuse is actually causing a great deal of distortion. The resistance is highly variable. Just for grins, short your fuse out and you will probably hear an immediate improvement in sound quality. If you do find this, consider building a speaker protection unit for your amps and install them. If you can find information on the mosfet type protectors, maybe give that a whirl. Anything should be better than a fuse for speaker protection.
Look at what member jwilhelm has done. He might be able to point you to a thread where this is discussed.
Best,Chris
That's fair enough. In my work, I often see failed equipment that generates a substantial DC offset in failure more. Some that shared your views (early Bryston for example) would lay waste to speakers in a very short amount of time. It only takes one failure to create a fire in a speaker. This is a common outcome when unprotected amplifiers suffer a failure.
Your series fuse is actually causing a great deal of distortion. The resistance is highly variable. Just for grins, short your fuse out and you will probably hear an immediate improvement in sound quality. If you do find this, consider building a speaker protection unit for your amps and install them. If you can find information on the mosfet type protectors, maybe give that a whirl. Anything should be better than a fuse for speaker protection.
Look at what member jwilhelm has done. He might be able to point you to a thread where this is discussed.
Best,Chris
I'm sure you're right about power amps having a big DC level at the output when they blow. Maybe I've just been lucky with my amps. And thanks for the info about the fuse causing distortion. I'll look into that.
identify the separate tappings. Label them. Identify the phasing of the tappings. Label them.Okay so to anwser the obvious question:
The transformer has 4 secondary tappings and 2 secondary windings.
I don'til see how I can connect the secondaries differently to the bridge rectifier.
Report back and then we can describe how to connect your transformer.
In the meantime assemble a Mains Bulb Tester, ready for first power ON.
"Reboot"
Hi all.
I think I want to update this thread since I have learned a lot from it. I bought a different power supply board which uses two bridge rectifiers I bought locally. The quality of the board was also better than the one I got from the kit. I completed the testing (bulb tester) and wired it up successfully some time ago and it played! Nice. However it did have A LOT of hum which I blaimed my unshielded cables and short distances to the transformers. I had it hooked up to my homemade speakers and I thought the sound was weird and lacked bass. I though it was my speakers that were bad so I hooked up a Jamo subwoofer you connect directly to the amplifier and then connect the speakers to the subwoofer. It sounded better but still not good.
Some more time passed while I kept using the amp. I noticed the capacitors in the power supply had expanded so the disc on top of it was bending outward. I did some digging and found that the kit I bought was propably build using fake components and this made me open up one of the capacitors as seen in the image below.
The capacitor is clearly not genuine and has a lower value capacitance and/or lower voltage rating so not good. I havent tested it for capacitance. I replaced them with some Densen 10000uF 63V I found locally unused second hand. See next image. A lot of hum was removed but not all. The sound quality was still not great and this made me think that the IC's was probably fake too.
I tried to remove the pre-amplifier since it was not really doing anything, but I did not notice any significant increase in music quality.
Therefore I decided I should start the project over using new power amplifiers but still with the lm3886 IC. I followed the guide on Circuitbasics A Complete Guide to Design and Build a Hi-Fi LM3886 Amplifier - Circuit Basics
and designed my own board and selected components according to the guide and the PHE450 capacitor after I read about it in Humble Homemade Hifi's Capacitor test (Humble Homemade Hifi - Cap Test). I did not buy the resistors from the guide since I dont think I can hear the difference yet.
I designed my board with these values:
I found the correct packages for the components and designed the PCB layout as below. I will fit RF1 directly to the pins on the IC and I still need to fit RSN and CSN.
Right now I am finishing the PCB copper area shapes and will order the PCB's via EasyEDA soon.
Hi all.
I think I want to update this thread since I have learned a lot from it. I bought a different power supply board which uses two bridge rectifiers I bought locally. The quality of the board was also better than the one I got from the kit. I completed the testing (bulb tester) and wired it up successfully some time ago and it played! Nice. However it did have A LOT of hum which I blaimed my unshielded cables and short distances to the transformers. I had it hooked up to my homemade speakers and I thought the sound was weird and lacked bass. I though it was my speakers that were bad so I hooked up a Jamo subwoofer you connect directly to the amplifier and then connect the speakers to the subwoofer. It sounded better but still not good.
Some more time passed while I kept using the amp. I noticed the capacitors in the power supply had expanded so the disc on top of it was bending outward. I did some digging and found that the kit I bought was propably build using fake components and this made me open up one of the capacitors as seen in the image below.
The capacitor is clearly not genuine and has a lower value capacitance and/or lower voltage rating so not good. I havent tested it for capacitance. I replaced them with some Densen 10000uF 63V I found locally unused second hand. See next image. A lot of hum was removed but not all. The sound quality was still not great and this made me think that the IC's was probably fake too.
I tried to remove the pre-amplifier since it was not really doing anything, but I did not notice any significant increase in music quality.
Therefore I decided I should start the project over using new power amplifiers but still with the lm3886 IC. I followed the guide on Circuitbasics A Complete Guide to Design and Build a Hi-Fi LM3886 Amplifier - Circuit Basics
and designed my own board and selected components according to the guide and the PHE450 capacitor after I read about it in Humble Homemade Hifi's Capacitor test (Humble Homemade Hifi - Cap Test). I did not buy the resistors from the guide since I dont think I can hear the difference yet.
I designed my board with these values:
I found the correct packages for the components and designed the PCB layout as below. I will fit RF1 directly to the pins on the IC and I still need to fit RSN and CSN.
Right now I am finishing the PCB copper area shapes and will order the PCB's via EasyEDA soon.
After thinking more, I'm going to get rid of the fuses and build a relay circuit that should make things safer (and higher fidelity). My main speakers (triamp'd) have a $225 Seas Millenium dome tweeter. If I blew that up, it would be bad.
Also, in case anyone cares, I changed the name (address) of my website from opal creek to ephaseaudio.com.
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