18V what?
DC or AC or dual polarity or single polarity?
This is not Cleudo, we need more than just the odd clue thrown at us.
DC or AC or dual polarity or single polarity?
This is not Cleudo, we need more than just the odd clue thrown at us.
If that's 18+18v AC (sticker on transformer), then you have 26+26vdc to 30+30vdc, depending on power supply efficiency (very much with that one!) and incoming voltage does also make a big effect on end result.
So you might want to check your DC output from your power supply to find out just how much. Please be safe. 😉
EDIT: HI Andrew! 😉
So you might want to check your DC output from your power supply to find out just how much. Please be safe. 😉
EDIT: HI Andrew! 😉
hi
I was reading it off the transformer which says dual secondaries at 18v each, I am thinking its AC right.
At the powersupply, its 26v, I am not gd with these terms, pls bear with me, so it should be read as 26vdc right?
I was reading it off the transformer which says dual secondaries at 18v each, I am thinking its AC right.
At the powersupply, its 26v, I am not gd with these terms, pls bear with me, so it should be read as 26vdc right?
Yes. That doesn't require a large heatsink. The "heat spreader" methods should work fine. Please use thermal paste.
That sounds about right.marcusdeming said:
But, both the 18Vac and 26Vdc will vary as the mains supply voltage varies.
Using the 26Vdc you can look up the National datasheets and read off suitable sizes for your heatsink.
That's about a 5-1/3rd C/W sized heatsink, on that voltage and with 6 ohm reference load.
In other words, it need not be huge, but you'll want something better than just the bottom of the case.
In fact, a thick flat aluminum plate added there, could do the job for both chips. Or, you could use just one large heatsink for both chips. Of course the really big washer method (simple heat spreader) can also work, if given sufficient thermal interface (shiny metal and thermal paste).
In other words, it need not be huge, but you'll want something better than just the bottom of the case.
In fact, a thick flat aluminum plate added there, could do the job for both chips. Or, you could use just one large heatsink for both chips. Of course the really big washer method (simple heat spreader) can also work, if given sufficient thermal interface (shiny metal and thermal paste).
danielwritesbac said:
Ok the heat spreader method, I will go get some thermal paste and black sand paper.
For the speaker zobels that you mentioned earlier, am i right to say that it can be done by connecting a 0.1uf polyester/pp cap across a pair of red and black speaker terminals, and to it on both sets. So what i need would be 2 0.1uf/200v (maybe) pp caps right?
EDIT: No, not polypropylene directly on the terminals--Polypro requires an added resistor
I think you can get a prettier sound with 2.2 ohms resistance added, and its less load for the amp.
While you're at the store, you can pick up some 0.22uf polyester film caps to try out as an option with 1 ohm (or 2.2 ohms) added for polyester--or much more added resistance if the cap is polypropylene.
Leaving off the zobel is also an option.
Um, correct me if I'm wrong, but the amplifiers pictured already have 0.1uf polypro+2.7ohm zobels installed.
EDIT3: This option mainly tailors the sound, but also provides extra support for very long speaker cables.
I think you can get a prettier sound with 2.2 ohms resistance added, and its less load for the amp.
While you're at the store, you can pick up some 0.22uf polyester film caps to try out as an option with 1 ohm (or 2.2 ohms) added for polyester--or much more added resistance if the cap is polypropylene.
Leaving off the zobel is also an option.
Um, correct me if I'm wrong, but the amplifiers pictured already have 0.1uf polypro+2.7ohm zobels installed.
EDIT3: This option mainly tailors the sound, but also provides extra support for very long speaker cables.
oh ok I didnt know that they are on board, those 0.1uf on board are polypropylene
danielwritesbac said:
And the big green thing in the photo next to it. . . is resistor for zobel? I think so. Its fine. You can play with the zobel later if you'd like to alter the treble response to suit personal preferences.
Hey, in that photo, your power caps are mismatched. You might want to fix that.
Hey, in that photo, your power caps are mismatched. You might want to fix that.
Screeching
I think Daniel is mistaken about the effect of carbon vs metal film resistors but absolutely right about heat management possibly causing the dreaded SPiKe to enter the room.
If your case is steel, as opposed to aluminum, you really should find a local scrapyard and get a piece of aluminum sheet 1/8" (3mm) or more thick; fasten it to the inside of the case (probably with your chip mounting bolts) with thermal goo between both the chips and the plate and the plate and the case. Round the edges and smooth down any scratches to insure good uniform contact. Aluminum spreads heat much better than steel.
By the way, one-inch (25mm) 5vDC fans that are extremely quiet are readily available at computer geek shops; if you still have heat problems, one of these might help.
I think Daniel is mistaken about the effect of carbon vs metal film resistors but absolutely right about heat management possibly causing the dreaded SPiKe to enter the room.
If your case is steel, as opposed to aluminum, you really should find a local scrapyard and get a piece of aluminum sheet 1/8" (3mm) or more thick; fasten it to the inside of the case (probably with your chip mounting bolts) with thermal goo between both the chips and the plate and the plate and the case. Round the edges and smooth down any scratches to insure good uniform contact. Aluminum spreads heat much better than steel.
By the way, one-inch (25mm) 5vDC fans that are extremely quiet are readily available at computer geek shops; if you still have heat problems, one of these might help.
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