Hi, I'm new to electronic design and I'm working on a USB DAC project.
I'm thinking of adding a power stage to this project but I don't have any experience in Audio Power Amps and not much time to spend.
If I take a Chip Amp (LM4780 for example) and connect it as per data sheet, is it gonna be ok? I'm not interested in extremely high quality.
Is the LM4780 an easy IC for a newbie? If not, which one do you suggest?
Thank you very much
I'm thinking of adding a power stage to this project but I don't have any experience in Audio Power Amps and not much time to spend.
If I take a Chip Amp (LM4780 for example) and connect it as per data sheet, is it gonna be ok? I'm not interested in extremely high quality.
Is the LM4780 an easy IC for a newbie? If not, which one do you suggest?
Thank you very much
Bluetech,
It depends on how you are going to implement it and your soldering skills.
Are you going to buy a pcb kit? are you going to etch your own pcb? are you going wire it point-to-point?
unless you are using a kit, LM4780 is not so easy to work with because of the fine pin spacing
as this is your first amp project, go for 2x LM3886 for simplicity
much easier to work with and better heat dissipation
LM4780 is essentially two LM3886's in one
Good luck!
It depends on how you are going to implement it and your soldering skills.
Are you going to buy a pcb kit? are you going to etch your own pcb? are you going wire it point-to-point?
unless you are using a kit, LM4780 is not so easy to work with because of the fine pin spacing
as this is your first amp project, go for 2x LM3886 for simplicity
much easier to work with and better heat dissipation
LM4780 is essentially two LM3886's in one
Good luck!
bluetech said:
Single V+ supply not recommended.
I used an adjustable power supply in my first LM3886 project, with 2 off LT1084 regulators and 2 off 10,000uf filter caps
http://www.shine7.com/audio/gainclone.htm
LT1083 is 7.5A in the weblink but I myself went for the LT1084 with 5A
The speakers are 4ohm and I am currently using +/-28V with good results, but I have experimented with +/-24V and had no problems
Again, as this is your first project, go for the flexibility of an adjustable regulated PS my opinion. You can set it up to whatever voltage you like.
Personally I love the sound of a reg. PSU despite what people say about stiff behaviour etc. Benefits are low noise and good bass for relatively little money. If you think LT1083 is too expensive you can use LM317 (with transistor for increased current capability)
So if you go for a regulated PS, don't forget the heatsinks for the regs - the more voltage drop across them, the more heat they will dissipate. But they don't need to be too large though.
Let me know if you need a schematic.
Finally I personally like soft-recovery bridge rectifiers, instead of the commonly used MUR860 diodes which are fast-recovery and induce ringing plus are not cheap (you'll need 16 of them). Either would be okay if used with reg. PS
Good luck
If you go for an unregulated supply with 4 Ohm speakers, use a 2 x 18 V transformer. You can use up to 2 x 22 V, but then you need an enormous heatsink and should take the unisolated package.
A regulated supply adds complexity and expense. For a first time project you should avoid that.
Adjustable voltage? There is an upper limit you can use. Setting the voltage below that means reducing the amplifier's dynamic headroom and increasing the heat dissipation across the regulators.
A regulated supply adds complexity and expense. For a first time project you should avoid that.
Adjustable voltage? There is an upper limit you can use. Setting the voltage below that means reducing the amplifier's dynamic headroom and increasing the heat dissipation across the regulators.
just a clarification, I am talking about PS output, not transformer output
I agree reg. psu may be more complex than unreg. but I still think it's a doddle on a perf board
the advantage is that you can change the voltage according to taste
I found optimum sonic performance at +/-28VDC but that is my taste!
I agree reg. psu may be more complex than unreg. but I still think it's a doddle on a perf board
the advantage is that you can change the voltage according to taste
I found optimum sonic performance at +/-28VDC but that is my taste!
LM3886
I'm with everyone else- its easier to use two LM3886 than a single LM4780 cause of those many tiny pins on the 4780. I've made both; and did a LM3886 on perfboard- no PCB required, but you have to angle those pins in there.
Do not use the single rail schematic on the data sheet, use the split supply and you will be fine. There are lot of schematics out there- I've got a few on my web site (link in my signature line).
I'm with everyone else- its easier to use two LM3886 than a single LM4780 cause of those many tiny pins on the 4780. I've made both; and did a LM3886 on perfboard- no PCB required, but you have to angle those pins in there.
Do not use the single rail schematic on the data sheet, use the split supply and you will be fine. There are lot of schematics out there- I've got a few on my web site (link in my signature line).
Re: Re: LM3886
No I have not, but its more complication for the first-timer. I was against it due to difficulity not sound quality-- though my guess using pure speculation is that the dual rail would sound better--- you've got me there though as I have never tried it.
Edit- I love that album on your avatar! Moving pics is awesome too.
MJL21193 said:
No I have not, but its more complication for the first-timer. I was against it due to difficulity not sound quality-- though my guess using pure speculation is that the dual rail would sound better--- you've got me there though as I have never tried it.
Edit- I love that album on your avatar! Moving pics is awesome too.
Hello everyone and thank you for your comments.
Igreen,
I saw in your schematic that you use a 2W resistor only in the output. Is that the only place that needs a high watt component?
What about the caps? what volt rating i should use. I saw in an other schematic was used 40v caps with 35v supply?
I'm thinking of using this power supply. what do you think?
http://sound.westhost.com/project04.htm
Nice project by the way.
Thank you
Igreen,
I saw in your schematic that you use a 2W resistor only in the output. Is that the only place that needs a high watt component?
What about the caps? what volt rating i should use. I saw in an other schematic was used 40v caps with 35v supply?
I'm thinking of using this power supply. what do you think?
http://sound.westhost.com/project04.htm
Nice project by the way.
Thank you
That power supply is great and can be used without any problems. May want to consider a "snubber" power supply (R and C across the + and - of your power supply to remove harsh high frequencies), search here for "snubber" or "snubberized" as posted by CarlosFM.
Yes, the 2W resistor is part of the Zobel network on the output terminal. You do not need any other high power parts, unless-
1. you put in a snubber power supply, the R should be high power.
2. You hook an LED to the power supply, you will need a 1/4 W or higher resistor to limit its current. Do you know how to do this? search here and internet for "LED equation" or "LED calculator"
You don't want to use 40V caps with a 35V supply. If there is a surge in your AC wall voltage the rating will be exceeded, plus good design calls for a wide saftey margin- double the expected voltage is good practice. There are standard voltages for Caps so pick the closest 50V minimum, 63 if you can or preferably 80V to impress the bigshots at this website.
Yes, the 2W resistor is part of the Zobel network on the output terminal. You do not need any other high power parts, unless-
1. you put in a snubber power supply, the R should be high power.
2. You hook an LED to the power supply, you will need a 1/4 W or higher resistor to limit its current. Do you know how to do this? search here and internet for "LED equation" or "LED calculator"
You don't want to use 40V caps with a 35V supply. If there is a surge in your AC wall voltage the rating will be exceeded, plus good design calls for a wide saftey margin- double the expected voltage is good practice. There are standard voltages for Caps so pick the closest 50V minimum, 63 if you can or preferably 80V to impress the bigshots at this website.
Even in the Boucherot cell a 1/4 W resistor should be enough. 2 W at that place would be something for a much bigger amplifier or to cover up a design issue like oscillations or insufficient airflow in the case.
The voltage rating for the caps should always be higher than the voltage they will be used on plus a safety margin of at least 25 %. 40 V capacitors with 35 V rails is already a tight match.
Project04 is a solid standard design except for the earth loop breaker, which a nice-to-have. Consider adding more capacity to the rails, especially with 4 Ohm speakers.
The voltage rating for the caps should always be higher than the voltage they will be used on plus a safety margin of at least 25 %. 40 V capacitors with 35 V rails is already a tight match.
Project04 is a solid standard design except for the earth loop breaker, which a nice-to-have. Consider adding more capacity to the rails, especially with 4 Ohm speakers.
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