Hi!
This is easy calculations if you understand how theese adjustable regulators works.
There is a constant voltage difference between the adjust pin and the output pin of 1.25 V. The resistor between adjust and output sets the current that goes throug the other resistor that goes to ground
If you use 91R between adjust and out, this gives you: 1.25 V / 91R = 0,013736 A.
This current goes throug the 1k trimmer. In worst case the trimmer is set to 1 K and gives you a voltage drop of : 0,013736*1000ohm = 13,736 V
Watt=Volt*Ampere. For this case: 13,736V * 0,013736 = 0,18867.
This means that in worst case the trimmer must handle 0,19 W. Some safety margin, and you are all set with a 0,25W trimmer.
It`s all about ohms law
Tor Martin
This is easy calculations if you understand how theese adjustable regulators works.
There is a constant voltage difference between the adjust pin and the output pin of 1.25 V. The resistor between adjust and output sets the current that goes throug the other resistor that goes to ground
If you use 91R between adjust and out, this gives you: 1.25 V / 91R = 0,013736 A.
This current goes throug the 1k trimmer. In worst case the trimmer is set to 1 K and gives you a voltage drop of : 0,013736*1000ohm = 13,736 V
Watt=Volt*Ampere. For this case: 13,736V * 0,013736 = 0,18867.
This means that in worst case the trimmer must handle 0,19 W. Some safety margin, and you are all set with a 0,25W trimmer.
It`s all about ohms law
Tor Martin
Vikash said:
I don't think such drastic movements would be required.
However, I'd like to point out, that any inquiries with regards to international distribution rights (of those boards), should be done directly with me, as it is mine, and Brian's, intellectual property, and the agreement I have with Brian is based on that (where I have the complete international rights to the sales of those boards).
I have no problem discussing it with you over the e-mail and I'm sure a solution can be easily achieved.
I know that the goal of this PSU is to make it as high quality as possible for chip amps, but I'm looking for ways to cut corners a little in order to reduce price for a multi-amped system. The project includes 10 3886's: 3 stereo and 1 bridged stereo 3886 amps (based off of Carlos' Non-Inverting v4 design), so the total cost is adding fast.
Any suggestions to help reduce the cost, especially in PSU land, without hitting quality too hard? One thing I was thinking was consolidating the traffos. If so, what would it be acceptable to combine down to? (as obviously a single traffo would not cut it for a regulated design when this many channels are needed). Any and all suggestions are greatly appreciated. Thanks for your time.
Any suggestions to help reduce the cost, especially in PSU land, without hitting quality too hard? One thing I was thinking was consolidating the traffos. If so, what would it be acceptable to combine down to? (as obviously a single traffo would not cut it for a regulated design when this many channels are needed). Any and all suggestions are greatly appreciated. Thanks for your time.
MikeLewis said:
That's 7 channels, right?
MikeLewis said:
Mmmm.... are you integrating everything inside one case?
That's big...
Seems like you're into multi-amping, so I would divide this by 3 separated, smaller amps: two with 3 channel each, and one with the bridge amp (which I suppose is for a sub?).
Then I would use the unregulated PSU, with a 300~400VA trafo for each amp.
Either separated amps or inside one only enclosure, this is my suggestion.
There are plenty of possible combinations, but I think this one is fine and won't break the bank.
yes, pretty similar to what I had in mind. the whole thing's going into a rather well-endowed 3-way system: stereo highs, dual stereo mids and bridged stereo subs (stereo because they will be reaching up to 300Hz, therefore non-omnidirectional).
The real fun's going to be getting the heat taken care of. Pretty sure this is going to require fans.
I really like the work you've done so I'm definitely going to try and stick to your specs on this, but that suggestion certainly helps a ton. Three 400VA traffo's is a lot easier bill to fit than ten 250's .
Also, I'm not in an area where I have a local parts shop. Any suggestions on good online shops that would carry quality components needed for this project and the 3886 amps? (Sorry if this has been asked before).
Again, thank you for your time, reading this forum has given me an enormous number of ideas that have radically improved/changed initial plans I had for this project.
The real fun's going to be getting the heat taken care of. Pretty sure this is going to require fans.
I really like the work you've done so I'm definitely going to try and stick to your specs on this, but that suggestion certainly helps a ton. Three 400VA traffo's is a lot easier bill to fit than ten 250's
.Also, I'm not in an area where I have a local parts shop. Any suggestions on good online shops that would carry quality components needed for this project and the 3886 amps? (Sorry if this has been asked before).
Again, thank you for your time, reading this forum has given me an enormous number of ideas that have radically improved/changed initial plans I had for this project.
Hi.
I had my amp playing into a pair of 8 ohm 50W resistors for about 100 hours before I put it into my main system for some serious listening.
Even though, the amp has improved alot the last few days.
When I first listened to it, the sound was exellent, but you could sense just a little bit of "roughness" in sound sometimes. I thought this was because of my tda1543 dac wich sometimes can sound a little rough.
But now the roughness is completly gone.
It might have been that the rest of my system needed some burn in time. It has not been used much during the summer.
Carlos:
I will try your new output stage.
But I have to wait until I have modified my speakers for biamping.
For now, when paralelling two chips, I need the output resistors.
Thanks
Tor Martin
I had my amp playing into a pair of 8 ohm 50W resistors for about 100 hours before I put it into my main system for some serious listening.
Even though, the amp has improved alot the last few days.
When I first listened to it, the sound was exellent, but you could sense just a little bit of "roughness" in sound sometimes. I thought this was because of my tda1543 dac wich sometimes can sound a little rough.
But now the roughness is completly gone.
It might have been that the rest of my system needed some burn in time. It has not been used much during the summer.
Carlos:
I will try your new output stage.
But I have to wait until I have modified my speakers for biamping.
For now, when paralelling two chips, I need the output resistors.
Thanks
Tor Martincarlosfm said:
I'm not American, but (in no particular order):
www.partsexpress.com
www.futurlec.com
www.digikey.com
www.mouser.com
I think that should cover it...
Michael
Tor M said:
Yes, caps need to
-in. Tor M said:Carlos:
I will try your new output stage.
But I have to wait until I have modified my speakers for biamping.
For now, when paralelling two chips, I need the output resistors.
Thanks
Ok, and try the new snubber values on the chip.
Did you find where to buy the 0.1R resistors?
Btw, I suspect you will benefit from biamping instead of paralleling chips, as you have now.
Yeah, I never thought a single LM3886 could get to this point of driving my speakers in perfection, but it does.
So much talk about damping factor and output impedance around here...
The PSU is essential for a good amp.
carlosfm said:
Hi Carlos.
No, I have not found any normal resistors in this value, just thoose 3 w wirewound. But they don`t cost more than half an euro anyway, so I`ll probably try thoose. Partsconnexion also has mills noniductive wirewound in 0,1 ohm that is not to expensive........
Thats the problem when I live in a city that don`t have any shops storing electronic parts.....
Tor Martin
carlosfm said:
Btw, I suspect you will benefit from biamping instead of paralleling chips, as you have now.
Yeah, I never thought a single LM3886 could get to this point of driving my speakers in perfection, but it does.
So much talk about damping factor and output impedance around here...
The PSU is essential for a good amp.
I made my amp such as I could change between parailell and single chip mode in a minute without soldering.
Listening to single chip now. The soundstage is even more holographic and the sound is a little cleaner with more details.
I`m going single chip from now on!
But I suspected this. The plan for this amp has always been biamping, not paralelling. Don`t think my Epos needs paralell chips with a minimum impedance of 7,2 ohm, and this in the trebile.
Tor MartinAttachments
Tor M said:I made my amp such as I could change between parailell and single chip mode in a minute without soldering.
Listening to single chip now. The soundstage is even more holographic and the sound is a little cleaner with more details.
I`m going single chip from now on!
There's always something to be lost when paralleling devices.
Glad you like it.
Now, before the resistors arrive you have something to entertain: adding another pair of binding posts to the Epos ES14 speakers.
Is it fresh in Norway?
It's too hot here.
Makes me dream about the north...
Yeah it`s fresh up here.
A little to cold (about 16 to 17 degree celsius), but it`s sunny and no wind, so it`s quite nice.
Unfortunally I`m sick, have stomach ache and have been throwing up.
Not nice Haven`t been out much today...
Only good about it is that I can stay home and listen to music instead of going to work. But I`d rather work than..........
Tor Martin
A little to cold (about 16 to 17 degree celsius), but it`s sunny and no wind, so it`s quite nice.
Unfortunally I`m sick, have stomach ache and have been throwing up.
Not nice
Haven`t been out much today...Only good about it is that I can stay home and listen to music instead of going to work. But I`d rather work than..........
Tor MartinTor M said:
That's nice.
It can make 30ºC at night here.
I'm better now, just arrived from a trip to a windy beach.
Tor M said:Unfortunally I`m sick, have stomach ache and have been throwing up.
Not nice
Only good about it is that I can stay home and listen to music instead of going to work. But I`d rather work than..........
Oh... that's not good.
Hope you get better soon.
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