| impsick |
can somebody please explain what im seeing here.
so i get the whole green blue puple is 24vct.
so is the orange and yellow, and grey and white dual secondaries?
can this push a 3 channel LM3886 amp?
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| sek |
Hi,
red and brown are the primary (not shown in the picture).
Orange and yellow form a secondary of 26.8V/4.8A.
Gray and white form a scondary of 26.8V/4.8A, too.
Green and purple form a secondary of 48.8V/4.8A with a blue center tap in the middle, giving you two 24.4V/4.8A rails with a common ground.
You can retrieve a second ground-referenced pair of rails by independently rectifying ORG-YEL and GREY-WHT (using one bridge rectifier per secondary wire pair), then connecting them in series. The connection would then become their ground reference.
Either 24V and 26V AC on the secondaries seem a little high, as it would be about 34V and 37.5V rectified and filtered DC. The specification of the 3886's assume 28V rails.
It will work, but you shouldn't connect a load lower than 8Ohm, as the SPiKE-Protection of the chip would ruin the sound. The datasheet shows around 35V as an optimal rail voltage for Ohm speakers (in order to achieve the highest dynamc range), but with a lower impedance power gets limited internally. :xeye:
For connecting three chips, use two at one pair of rails and the third at the other pair - e.g. two channels main speakers and one channel subwoofer... The current capability is fiar for this purpose (with 8Ohm speakers only!), although not high. I'd say domestic hifi, but no sound reinforcement. :D
See LM3886.PDF and AN-1192.PDF at http://www.national.com ;)
Hope this helps,
Sebastian. |
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| impsick |
| it helps allot! thanks Sabastian for your time. |
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| sek |
You're very welcome. :D
Just to make sure, check all voltages between all possible pairs of secondary wires using a multimeter. Connect a power resistor in the order of 1kOhm at 5 Watts between the leads while you measure (in order to load the winding and give meaningful readouts at the meter). |
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| impsick |
| cool. will do thanks again |
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| AndrewT |
Hi,
each secondary winding has around 120VA rating.
Each pair is thus 250VA or 230VA.
You can run upto 150W of output power from each pair. (VA~=1.5* max Pout)
This indicates you could run 4 amplifiers, each into 8ohm, from this one transformer. If you are prepared to accept slightly lower power ability you could run five or six channels from it.
I would recommend a separate rectifier and pair of smoothing caps for EACH amplifier.
Caution,
at these DC voltages, most chipamps will not like 6ohm or 4 to 8ohm speakers that are now very common. Stick to real 8ohm speakers Re>=6r0). |
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| impsick |
| Andrew, so are you saying orange & yellow, and white and grey should go to seperate rectifier boards? |
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| AndrewT |
Hi,
I did not recommend using separate rectifiers for one of your dual polarity supplies. That is a choice you can make if you want.
Here is something to think about before you make that decision.
The lower voltage centre tapped winding can only use a single rectifier to a series pair of smoothing capacitors. Each supply rail will lose 0.7V through the rectifier.
The twin windings can be centre tapped and single rectifier again to a series pair of smoothing capacitors. This will give a higher voltage on the DC supply rails.
Alternatively,
you can put a rectifier on each winding and then each rectifier feeds a single capacitor. This loses 1.4V instead of 0.7V on each supply and will bring your two sets of PSU voltages closer together at the cost of one extra rectifier.
What I was saying is, if you want to put more load on the transformer you can add extra rectifier and pair of smoothing caps for one extra amplifier, and repeat this as often as you need up to a limit on each pair of windings of about 150W to 180W. This will be 4, 5or 6 channels if you require that many. It is a big transformer to supply just two chipamps outputing a total power somewhere about 100W to 120W. |
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| impsick |
What I was saying is, if you want to put more load on the transformer you can add extra rectifier and pair of smoothing caps for one extra amplifier, and repeat this as often as you need up to a limit on each pair of windings of about 150W to 180W. This will be 4, 5or 6 channels if you require that many. It is a big transformer to supply just two chipamps outputing a total power somewhere about 100W to 120W. [/B][/QUOTE]
Andrew i appreciate your time. thanks.
i understand what your saying but im a visual person so to attempt this would be insane. here is a drawing of what i understand.
its probably totally not what you meant. if your bored and feel like drawing please correct me.
dont worry dont panic im not gonna try anything stupid. |
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| AndrewT |
H,
I can't see your sketch.
you have 4* in the search string. |
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| impsick |
sorry
**** man for some reason i cant post it |
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| impsick |
| andrew i sent you the link to the drawing. it wouldnt let me post it up. |
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| sek |
Hey,
| quote: | | it wouldnt let me post it up. |
Yeah, why oh why? :D
If you call your picture "*s*h*i*t*.jpg" and then post in a filtered forum, that's what happens. :smash:
Your picture looks alright, this is called a parallel connection of the rectifiiers.
But of course you wouldn't connect the rectifier to the amp without large smoothing capacitors and such, right? What Andrew meant was to connect multiple power supply units with each their own rectfier bridge. For the center tapped winding, center tap is the PSUs' ground.
Cheers. |
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| impsick |
ha ha oh my god. thats funny. yeah i got some 50v 15,000uf chemi- cons. that should be ok, or is that too much? im having a hard time understanding what you guys mean by multiple power supplies with ct as ground. so the ct is +pg and -pg? to multiple boards? sorry, im sure once i get this down i will understand the whole concept better.
ha ha i just realized what Andrew meant by 4*. every time he tries to help me i think i **** him off cause im all slow n ****. lol |
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| sek |
Your awesome rant| quote: | | **** man for some reason i cant post it |
did the trick for me. ;)
As to where to connect what and what name to give to which wire... Care to explain what amplifier and power supply schematics and boards you plan on using exactly? :) |
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| impsick |
oh sorry its chipamp.com
ok on the last diagram i believe this should work but im confused on where exactly im putting the ct. where it says center tap in bold?, or on center tap and PG? and then im confused on where it goes after. to amp board pg and -pg? |
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| sek |
Funny, looks like a TNT-Audio PSU drawing, the National Semi LM3886 datasheet standard application and a variety of the Peter Daniel/Brian Bell rectifier board glued together. ;)
On page 15 of Brian's/Peter's manual they describe the case "using a center-tapped transformer". This applies to your green-blue-purple winding.
On the very same page, the last paragraph mentions the difference to a true dual secondary transformer. This applies to your orange-yellow (AC1H-AC1N) and gray-white (AC2H-AC2N) windings and is also shown in the drawing on page 17.
A parallel connection means that you branch off each wire from the trafo and connect multiple such PSU boards.
| quote: | | and then im confused on where it goes after |
It's all in the manual. And Brian and Peter offer free support on their products, too. ;)
Cheers. |
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| impsick |
| quote: | Originally posted by sek
Funny, looks like a TNT-Audio PSU drawing, the National Semi LM3886 datasheet standard application and a variety of the Peter Daniel/Brian Bell rectifier board glued together. ;)
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ha ha you called that one.
i understand what parallel is, i 've read those manuals 100x. i guess its just the ct going after the bridge that gets me messed up. i just wanted confirmation on its placement. :( thanks for your time man. its appreciated.:) |
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| sek |
No worres, man. :cool:
Just don't forget to come back with any more questions once you have all the parts (and are unsure of the exact connections). It's always easier to explain it on the real thing. ;)
And post pictures of your results. :)
Sebastian. |
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| Greg Erskine |
| quote: | Originally posted by sek
Funny, looks like a TNT-Audio PSU drawing.... |
Not quite, TNT drew the bottom bridge the right way round. ;) |
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| sek |
Actually not, the current TNT article shows a different configuration with the supply star ground merged at the bridges instead of the capacitors.
On the drawing posted here, the bridge orientation is right for the configuration that was being discussed here. ;)
Maybe I just mixed up Brian Bell's and Dejan Veselinovic's drawings because they look similar.
Cheers. |
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