Buncha jokers you guys are 
These next boards will only have one LED, and you're welcome to use any type you like. However, I will supply a red one because blue ones are about a buck a piece and that's just way too much for an LED says my wallet.
These next boards will only have one LED, and you're welcome to use any type you like. However, I will supply a red one because blue ones are about a buck a piece and that's just way too much for an LED says my wallet.
😱 I don't know where you buy your LED's, but a buck each is WAY too much.
I recently bought 100 blue 3mm 5000mcd LED's off ebay for $1 + $11 shipping. That comes out to only 12 cents each.
I recently bought 100 blue 3mm 5000mcd LED's off ebay for $1 + $11 shipping. That comes out to only 12 cents each.
Go on Digi-Key and look up blue LEDs. Most of the through hole ones are at least $1 for about 1-99pcs. 100 or more and the price will usually drop a little bit but I'm not going to buy that many at one time.
I usually don't buy stuff off of ebay because I have a running list of parts I can get from either Digi-Key or Mouser and when I have enough funds I just put in one large order to save on shipping 🙂
I usually don't buy stuff off of ebay because I have a running list of parts I can get from either Digi-Key or Mouser and when I have enough funds I just put in one large order to save on shipping 🙂
I'm aware of the price of LED's from the major parts dealers; which is why I buy them off ebay.
Anyways, about these modules. If I run two of these off a 14-0-14 supply, the output should be nearly the same as using a T-amp on a single 14v supply, correct?
I really hope I can come up with some money by the time you get the new boards, I'd really like to try them. I've been spending way too much money buying things online lately. I think I need to join an ebay addicts counseling group.
Anyways, about these modules. If I run two of these off a 14-0-14 supply, the output should be nearly the same as using a T-amp on a single 14v supply, correct?
I really hope I can come up with some money by the time you get the new boards, I'd really like to try them. I've been spending way too much money buying things online lately. I think I need to join an ebay addicts counseling group.
I guess Ebay really is good for some things after all 😉
The 7720 is rated to have an absolute maximum rail to rail voltage of 26V. With split supplies that's +/-13V rails. They recommend a maximum of 24V rail to rail or +/-12V rails. I haven't seen what output voltage swing it can do before clipping with 13V rails. I do know that the output can swing up to 10.5V on the verge of clipping with 12V rails. That's a maximum peak power output (all the following numbers are peak as well) of 13.8W @ 8ohms and 27.6W @ 4ohms assuming the overcurrent protection isn't tripped.
The TA2021B output will go to 12V on the verge of clipping with a 14V rail. That's 18W @ 8ohms and 36W @ 4ohms also assuming the overcurrent protection isn't tripped.
However, you can bridge two D10.1 modules to give you a 21V output swing with +/-12V rails. That's only recommended with a load of 8ohms, and will give you 55W assuming the overcurrent protection isn't tripped.
Both the 7720 and the TA2021B have internal overcurrent protection circuitry. The 7720's is set at 5A and the TA2021B's is set at 7A according to the data sheets. I've triggered that protection with the TA2021B but haven't yet with the 7720.
The 7720 is rated to have an absolute maximum rail to rail voltage of 26V. With split supplies that's +/-13V rails. They recommend a maximum of 24V rail to rail or +/-12V rails. I haven't seen what output voltage swing it can do before clipping with 13V rails. I do know that the output can swing up to 10.5V on the verge of clipping with 12V rails. That's a maximum peak power output (all the following numbers are peak as well) of 13.8W @ 8ohms and 27.6W @ 4ohms assuming the overcurrent protection isn't tripped.
The TA2021B output will go to 12V on the verge of clipping with a 14V rail. That's 18W @ 8ohms and 36W @ 4ohms also assuming the overcurrent protection isn't tripped.
However, you can bridge two D10.1 modules to give you a 21V output swing with +/-12V rails. That's only recommended with a load of 8ohms, and will give you 55W assuming the overcurrent protection isn't tripped.
Both the 7720 and the TA2021B have internal overcurrent protection circuitry. The 7720's is set at 5A and the TA2021B's is set at 7A according to the data sheets. I've triggered that protection with the TA2021B but haven't yet with the 7720.
Bummer, I have a handful of 14v 3amp switching supplies that work great for T-amps. I was hoping to be able to just throw two in series to make a supply for these.
What do you think the odds of them surviving 14v would be?
What do you think the odds of them surviving 14v would be?
They would survive, the question is for how long. I'm not sure, but I'd like to use my tester modules a little longer before trying out the 14V rail test. My unregulated supply has two secondaries that sit around 23V and the regulators knock them down to 12V, so I can certainly test that later. Is there any way you could adjust a resistor or something in the switching supplies to lower the output a volt or two?
No, unfortunately the chips these supplies are based on are internally set at 14v.
If these things can live at 14v with an 8ohm load and a heatsink attached to the chip I wouldn't have any doubts about wanting to snatch a couple of them from you.
If these things can live at 14v with an 8ohm load and a heatsink attached to the chip I wouldn't have any doubts about wanting to snatch a couple of them from you.
I wouldn't be too worried about the chip overheating but rather the higher voltage stressing the chip's internal mosfets and circuitry. The external components on the board can easily handle the higher voltage. The 7720 would certainly be better off with an 8 ohm load at 14V than a 4 ohm load.
So the supplies have an internal reference? I was thinking there would probably be some form of resistive divider at the output that goes to a feedback pin on the chip.
So the supplies have an internal reference? I was thinking there would probably be some form of resistive divider at the output that goes to a feedback pin on the chip.
Perhaps I'm wrong. I might have misread the product details the first time around, not that I have a very good understanding of these things in the first place.
The IC is a TOPSwitch-GX TOP247Y.
Here is a link to the product page.
http://www.powerint.com/topgxproduct.htm
And here is a link to a schematic based on this IC thats pretty much identical to the supplies I have. I do notice now that this pdf is for a 12v supply and mine are 14v using the same IC, so it must capable of being adjusted.
http://www.powerint.com/PDFFiles/di21.pdf
The IC is a TOPSwitch-GX TOP247Y.
Here is a link to the product page.
http://www.powerint.com/topgxproduct.htm
And here is a link to a schematic based on this IC thats pretty much identical to the supplies I have. I do notice now that this pdf is for a 12v supply and mine are 14v using the same IC, so it must capable of being adjusted.
http://www.powerint.com/PDFFiles/di21.pdf
An externally hosted image should be here but it was not working when we last tested it.
If you can tweak R13 or R14 then you can change the output voltage. I believe you'd want to make R13 a smaller value but I'm not sure how much smaller. It might actually be better to put a large value pot (100k should do) in parallel with R13 and then tweak it while measuring the voltage across the output. Just stop when you see 12v.
resistor value?
R13 sets the voltage. Any value close to 38.3k will give you close to 12v. The reference voltage is aprox. = to 2.5 volts across the 10k res this sets the networks current to .25 ma. .25ma X 38k + 2.5 volts = 12 volts. R13 is made a little larger to compensate for the LM431's reference point not being exactly 2.5 volts.
R14 could be changed to around 8k and a 2k pot put in series with it. This would give you a range of adjustment from 12v to 15v. Use a good multiturn cermet pot.
Roger
R13 sets the voltage. Any value close to 38.3k will give you close to 12v. The reference voltage is aprox. = to 2.5 volts across the 10k res this sets the networks current to .25 ma. .25ma X 38k + 2.5 volts = 12 volts. R13 is made a little larger to compensate for the LM431's reference point not being exactly 2.5 volts.
R14 could be changed to around 8k and a 2k pot put in series with it. This would give you a range of adjustment from 12v to 15v. Use a good multiturn cermet pot.
Roger
After close inspection the supplies I have differ from that schematic quite a bit.
I found a group of 3 resistors that change the voltage simply by the touch of my finger. I tried bypassing them with a 5k resistor and it definitely lowered the voltage, but my fingers get clumbsy and my eyes get squinty this late at night and I kinda slipped. I hit some microscopic black thing called IC001 that looks exactly like a SMD transistor and made a few sparks. The voltage reads 7v now. I have no clue what IC001 is so theres little hope of replacing it.
I have about 5 more of these so its no big deal, but I don't think I'll be probing around on the rest of them.
Heres a pic of the resistors and IC.
I found a group of 3 resistors that change the voltage simply by the touch of my finger. I tried bypassing them with a 5k resistor and it definitely lowered the voltage, but my fingers get clumbsy and my eyes get squinty this late at night and I kinda slipped. I hit some microscopic black thing called IC001 that looks exactly like a SMD transistor and made a few sparks. The voltage reads 7v now. I have no clue what IC001 is so theres little hope of replacing it.
I have about 5 more of these so its no big deal, but I don't think I'll be probing around on the rest of them.
Heres a pic of the resistors and IC.
An externally hosted image should be here but it was not working when we last tested it.
Unknown part?
I think that "ic" is the LM431 or equivalent. The picture is not high enough resolution to be very useful. Could you zoom in and make the parts clearer? Possibably attach it as a file?
Roger
I think that "ic" is the LM431 or equivalent. The picture is not high enough resolution to be very useful. Could you zoom in and make the parts clearer? Possibably attach it as a file?
Roger
Wow, I can see better with the pic I took than with a magnifying glass. Hows this?
I've tried to search for "F111" and this is all I can find...
F11 = DTB113EK pnp dtr 1k + 1k 50V 500mA
111 = DTA113ZUA pnp dtr 1k+10k 50V 100mA
Could it be either of those?
An externally hosted image should be here but it was not working when we last tested it.
I've tried to search for "F111" and this is all I can find...
F11 = DTB113EK pnp dtr 1k + 1k 50V 500mA
111 = DTA113ZUA pnp dtr 1k+10k 50V 100mA
Could it be either of those?
IC question
I can't be sure but with one leg of the IC going to the opto isolator input I do think this is the 431 equivalent. This would make R16 the same function as R14 and R15 the same as R13 in the drawing. It would appear as if R14 and R15 are in series. If the lower end of R15 is not connected directly to the output voltage and R14 is, then the extra resistor is being used to allow fine tuning. I can't read the values, can you? If you can determine the values the previous formula would work to set the new output value.
Roger
I can't be sure but with one leg of the IC going to the opto isolator input I do think this is the 431 equivalent. This would make R16 the same function as R14 and R15 the same as R13 in the drawing. It would appear as if R14 and R15 are in series. If the lower end of R15 is not connected directly to the output voltage and R14 is, then the extra resistor is being used to allow fine tuning. I can't read the values, can you? If you can determine the values the previous formula would work to set the new output value.
Roger
Technically all 3 resistors are in series. The top of R016 is connected to +Vout and the bottom of R014 is connected to -Vout.
R014 = (223) 22k
R015 = (4301) 4.3k
R016 = (1095)?
I cant really see R016 so I'm not sure of the number on it. The leg of IC001 I hit goes down to Q001 so that might be dead too.
Adjusting R015 or R014 will definitely change the voltage, just not sure if I'm interested in doing it anymore.
EDIT: I got my courage back and soldered a 1k resistor across R015 on one of the good supplies and its working just fine at 12.5v. I'll save trying to resurect the dead supply as a project for another day. No more poking at SMD parts in wee hours of the morning anymore.
R014 = (223) 22k
R015 = (4301) 4.3k
R016 = (1095)?
I cant really see R016 so I'm not sure of the number on it. The leg of IC001 I hit goes down to Q001 so that might be dead too.
Adjusting R015 or R014 will definitely change the voltage, just not sure if I'm interested in doing it anymore.
EDIT: I got my courage back and soldered a 1k resistor across R015 on one of the good supplies and its working just fine at 12.5v. I'll save trying to resurect the dead supply as a project for another day. No more poking at SMD parts in wee hours of the morning anymore.
Brian et al., my tweeters are Aurum ribbons. Would the impedance matching transformer built into them obviate the need for an output filter? Might be something to experiment with.
The short answer is no, the impedance matching transformer can not just replace the inductor in the output filter. For one, the inductor in the output filter is meant to handle much higher frequencies than the impedance matching transformer. Whether or not an impedance matching transformer could be designed to also work as part of the output filter in a class d amp is something I'm not sure of.
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