4 ch. MOD86
I am planning on building a 4 channel amp based on four individual Modulus-86 boards. The instructions suggest a single 200VA transformer with 22V secondaries for a 2 ch. configuration e.g. the Antek AS-2222.
Can I use e.g. a single Antek AS-4222 i.e. 400VA with 22V secondaries rather than 2 x AS-2222? I reckon I would need two power supply boards and simply connect them in parallel to the AS-4222. Would I need to make any additional changes?
Soren.
I am planning on building a 4 channel amp based on four individual Modulus-86 boards. The instructions suggest a single 200VA transformer with 22V secondaries for a 2 ch. configuration e.g. the Antek AS-2222.
Can I use e.g. a single Antek AS-4222 i.e. 400VA with 22V secondaries rather than 2 x AS-2222? I reckon I would need two power supply boards and simply connect them in parallel to the AS-4222. Would I need to make any additional changes?
Soren.
Welcome to diyaudio, sebbesen!!
Tom's design doc discusses transformer selection. I used that to decide on 3222 to power 4 3886s.
If you have low impedance and lower sensitivity speakers that would require more power and larger transformer. But I think 3222 is still plenty for four chips for normal speakers. Especially if you are using a Power86 per pair, which allows my amps to keep playing a few seconds after power off.
One Power 86 would run the 4 amps but you may want to increase the storage capacity as Tom suggested when I asked the question on his other thread.
Is 400VA big enough to consider inrush limiter? With 2 Power86?
Tom's design doc discusses transformer selection. I used that to decide on 3222 to power 4 3886s.
If you have low impedance and lower sensitivity speakers that would require more power and larger transformer. But I think 3222 is still plenty for four chips for normal speakers. Especially if you are using a Power86 per pair, which allows my amps to keep playing a few seconds after power off.
One Power 86 would run the 4 amps but you may want to increase the storage capacity as Tom suggested when I asked the question on his other thread.
Is 400VA big enough to consider inrush limiter? With 2 Power86?
Thanks Richidoo! That's very helpful information. Actually, I already ordered the 2222. My plan was to start by building a 2 channel amp and then add another two channels down the road. For packaging reasons I would then opt for one big transformer like the 3222 or 4222 rather than adding another 2222 - or are there potential benefits (sound quality?) of having two separate 2222 rather than one big for all four channels?
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For the transformer sizing, I suggest taking a look at my Taming the LM3886 - Power Supply Design page. At the bottom of the page, you'll find an Excel spreadsheet that calculates the required VA rating of the power transformer.
You can connect as many Modulus-86 boards to the Power-86 board as you like, but with all channels running, you'll get higher ripple voltage, so the amp will clip a few hundred mV sooner. The Power-86 board is intended for a stereo amp. For more channels, I suggest adding more supply capacitance. You can do this in many ways. Connecting multiple Power-86 boards to the same transformer is certainly one way.
Good plan.
The benefits of mono blocks and separate power supplies are mostly related to power supply rejection and channel separation. Many power amplifiers have rather poor power supply rejection, i.e. some portion of the ripple voltage on the supply rails will make it through to the amplifier output. The Modulus-86, on the other hand, has absolutely stellar supply rejection. This is why I get the same measured performance on a regular unregulated power supply (Antek AN-2222 + Power-86) as I do when using two Agilent E3632A lab power supplies ($1200/each) to power the Modulus-86. The stellar supply rejection of the Modulus-86 means that you do not need a separate power supply for each amplifier channel. The only advantage of a separate supply is the lower ripple voltage as I touched on above. You can get that by increasing the supply cap as well.
The channel separation of a Modulus-86 stereo build pertains mostly to the quality of your wiring inside the chassis. Each Modulus-86 board is a fully self-contained mono channel to maximize the channel separation.
Feel free to ask the support questions in the Modulus-86 thread in the Vendor forum, by the way. I'm happy to answer questions in either thread, but it may make the answers to support questions easier to find if they're all in one place.
~Tom
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You just answered one of my questions Tom, i was mulling over the cost of another mono block build but looking at the info so far about supply rejection, i was thinking a single chassis would be just about as good.
Do you have any ideas about how close the boards can be mounted to each other without compromising the design. This might help with decisions about layout and chassis size.
Do you have any ideas about how close the boards can be mounted to each other without compromising the design. This might help with decisions about layout and chassis size.
Some nice toroids here with dual 22V secondaries, applicable to this build:
http://www.diyaudio.com/forums/swap...nsformer-130-va-dual-22v-sec-4-units-new.html
Best,
Anand.
http://www.diyaudio.com/forums/swap...nsformer-130-va-dual-22v-sec-4-units-new.html
Best,
Anand.
I use turned pin sockets with gold inserts for the pins. I have never experienced any difference in sound quality between socketed parts and parts soldered directly to the PCB.
I use sockets because it allows for easier debugging. For a final build, I'd probably just solder the ICs directly to the board. I included sockets on the Mouser BOM to allow the builder some flexibility and also to increase the likelihood of success for those who don't feel comfortable soldering directly on the IC pins.
~Tom
I use sockets because it allows for easier debugging. For a final build, I'd probably just solder the ICs directly to the board. I included sockets on the Mouser BOM to allow the builder some flexibility and also to increase the likelihood of success for those who don't feel comfortable soldering directly on the IC pins.
~Tom
Hello everybody,
I have just bought a couple of Modulus-86 Rev. 2.0 Amplifier PCB and a Power-86 Power Supply PCB.
I have a question :
- Does some internal protections prevent loudspeakers from DC current due to input signal ?
As you can see, some LM3886 cards from China are fitted with a Upc1237 protection chip.
- Is it necessary to add a such module in the build project ?
Dominique
I have just bought a couple of Modulus-86 Rev. 2.0 Amplifier PCB and a Power-86 Power Supply PCB.
I have a question :
- Does some internal protections prevent loudspeakers from DC current due to input signal ?
As you can see, some LM3886 cards from China are fitted with a Upc1237 protection chip.
- Is it necessary to add a such module in the build project ?
Dominique
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It is my understanding that a DC servo instead of an input capacitor serves to block DC in this amp.
Hi davym,
I think it would be better to put a protection card because if an output transistor in the LM3886 module is shorted or breakdown, I do not see how you could prevent current from flowing into the load! should be a monitoring system that blocks the second transistor when there is an unwanted current flow! I doubt there is such a system because Texas would have hastened to talk!
I do not agree with you because in my understanding, the DC servo is used in feedback in order to null or reduce the amplifier's offset voltage.
I think it would be better to put a protection card because if an output transistor in the LM3886 module is shorted or breakdown, I do not see how you could prevent current from flowing into the load! should be a monitoring system that blocks the second transistor when there is an unwanted current flow! I doubt there is such a system because Texas would have hastened to talk!
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How do you think servos work? Their entire purpose is to make the DC output zero. If DC is at the input then the servo removes that. Or are you talking about severe errors where (say) 12v is applied to the input?