| theAnonymous1 |
I plan on using a 28-0-28 SMPS on three AMP1's and was wondering what the best way to get the "stabilized 50ma 5v" would be. The supply will be in a case with three XLR plugs, one for each individual amp, so the "solution" would need to come from the power feed into the amp.
Oh, and a couple dumb questions..... what is it even needed for, and does it need to be 5-0-5 or just a single supply? |
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| soongsc |
| I'm thinking about doing something similar with the AMP2. It uses +5V. I wonder if just adding something like a LM78xx to bring a voltage down to 5V would do. |
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| theAnonymous1 |
| This little obstacle is the only thing holding me back from ordering three of them, so you can imagine how anxious I am to find an easy answer. |
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| theAnonymous1 |
| Well I just read the data sheet for the TA2022 evaluation board and it say it needs a +5v supply that isn't referenced to the main supply ground. Does that mean I'm SOL on taking the 5v off of the main supply? |
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| soongsc |
My AMP2 is not here yet, but the assembly instruction say as follows:
Audio signal sources and the 5V supply must be grounded to J2. This connector is in turn connected via an inductor bead to the star grounding point where the power supply is connected. |
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| theAnonymous1 |
| I guess I'll just get a 5v supply and figure out another way to put everything together. I really did like the idea of three separate amps with only a single XLR running to each one for power. |
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| theAnonymous1 |
The only reference to a LM317 in the document I see is for an external VN10 supply that should be around 11v. Do I just adjust the 1.8k or 240 ohm resitor to get a lower voltage?
I'm sure this is probably something very simple for most, but I'm kind of new at this stuff so please forgive me. |
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| sx881663 |
Sorry for the confusion, I didn't look into it deep enough. I have no idea what use their recommended circuit was for.
The LM317 input would be from the main + input, its ground should be the analog ground connected on the same connector where the 5V goes into the board. R1 = 240 ohm (out to adj), R2 = 720 ohm (adj to ground) for 5 volts. Wish I had an easy way to do a little drawing. Scanning and editing is way too much effort to get it small enough to be accepted for posting.
Roger |
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| soongsc |
| quote: | Originally posted by theAnonymous1
The only reference to a LM317 in the document I see is for an external VN10 supply that should be around 11v. Do I just adjust the 1.8k or 240 ohm resitor to get a lower voltage?
I'm sure this is probably something very simple for most, but I'm kind of new at this stuff so please forgive me. |
You could adjust the 1.8K part, I somehow recal the 240 is a pretty standard value there.
I think you could also use an LM7805 sort of device.
Check the maximum input voltages before you use them. |
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| theAnonymous1 |
Thank you guys for all your help. After doing some reading it seems the lower you make the output voltage the hotter this little regulator is going to run. So if I am using a 28v supply and only need 5v from it, the LM317 has to dissipate the other 23v as heat :hot: .
In conclusion, I think I will use a LM350 or LM338, as they are rated at 3 and 5 amps. Thanks again for the help fellas. |
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| sx881663 |
With only .08a max the dissipation would be .08 X 23 = 1.84W. A small L bracket used to mount the part to the case would do very well getting rid of the heat This is very comfortably within the LM317’s specs, no problem. You really don’t need to use something bigger, especially something optimized for higher currents.
Roger |
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| soongsc |
| Lots of SMPS have more than one power output. It's possible to use one of those and then regulate it. 5V is very common in SMPSs as well, I just don't know how accurate they are. |
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| theAnonymous1 |
Your right Roger, I misread something in the document that led me to believe it would get much warmer than 1.6 watts of dissipation.
I'm using four 14v 12 amp supplies in series and there is no 5v section. Maybe theres 5v on the board somewhere, but I'm not comfortable probing around to find out.
I think this will work out well as long as I don't blow anything up trying to get the LM317 circuit working, I'm uber novice.
I'm just going to order one AMP1 for now and see how assembly goes and if I can actually get it to work. It will end up costing me another $10 in shipping fees to break up the order like that, but its better than having two more kits I can't use if things don't turn out right. |
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| theAnonymous1 |
Ok, another question :( . Tripaths circuit has the ground and Vin reversed from the standard LM317 circuit because it uses VNN which would make ground positive for the 5v supply.
That doesn't sound very safe for how I intend to use it. Would it be ok to use VPP instead and use the standard LM317 input scheme?
Attached is an image of both circuits with tripaths being on top. |
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| BWRX |
| quote: | Originally posted by theAnonymous1
Would it be ok to use VPP instead and use the standard LM317 input scheme? |
yes. the tripath circuit is like that so the voltage is referenced to the negative supply rail. plus, that was a schematic for an external V10 supply. |
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| theAnonymous1 |
| Seems I let my anxieties get the best of me again, the answer was as simple as just taking a moment to look at the 41hz website with my eyes a little wider open :bigeyes: . |
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| soongsc |
| quote: | Originally posted by theAnonymous1
Seems I let my anxieties get the best of me again, the answer was as simple as just taking a moment to look at the 41hz website with my eyes a little wider open :bigeyes: . |
Little devices like the attached pic can help you get rid of the transformer. If you get a 7.5V or 9V one and use it with an LM7805, it's very small. |
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| theAnonymous1 |
soongsc, I'm going to use an SMPS, so in the pic just imagine everything to the left of the +/- 30v gone and replaced with it.
I really need to slow down a bit, I just ordered 6 LM317's off ebay, then I found some LM317LZ's which are a TO-92 package that handle 100ma that I thought would work perfectly. This was all before I saw the 7805 regulator circuit on 41hz.com, so after seeing it I bought 6 LM7805's.
Now, I'm sure your saying something like "did this guy forget to take his meds today", but its not over yet. After ordering the 7805's I remembered I had some regulators somewhere but I had no clue what they were. I found four of them after a short search and low and behold their some nice Motorola T7805CT's that I verified to work in about 30 seconds hooking it up with two jumper wires to an SLA.
So after all my rambling and questions the answer to my problem was as close as the website for the amp, and my own junk drawer :dead: . |
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| soongsc |
| quote: | Originally posted by theAnonymous1
soongsc, I'm going to use an SMPS, so in the pic just imagine everything to the left of the +/- 30v gone and replaced with it.
I really need to slow down a bit, I just ordered 6 LM317's off ebay, then I found some LM317LZ's which are a TO-92 package that handle 100ma that I thought would work perfectly. This was all before I saw the 7805 regulator circuit on 41hz.com, so after seeing it I bought 6 LM7805's.
Now, I'm sure your saying something like "did this guy forget to take his meds today", but its not over yet. After ordering the 7805's I remembered I had some regulators somewhere but I had no clue what they were. I found four of them after a short search and low and behold their some nice Motorola T7805CT's that I verified to work in about 30 seconds hooking it up with two jumper wires to an SLA.
So after all my rambling and questions the answer to my problem was as close as the website for the amp, and my own junk drawer :dead: . |
I think we're on the same boat. I have an AMP2 that's supposed to come in soon, and I just got two 48V SMPSs that I intend to put in series (two of these turned out more expensive than the kit itself. :xeye: ). I'm also trying to figure out what to do to get the 5V. Most SMPS that I looked at had that kind of output, but not with the one's I got. So I'm just going to get the little AC-DC power either the 7.5V one or the 9V one and hook the LM7805 to regulate it. All I need to do is check the max input voltage of the LM7805. |
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| sx881663 |
The LM317 circuit as shown by Tripath and connected as per Jan at 41Hz would be your best solution. But you do need to heatsink it using the TO220 case style part. This is just too much heat for the small part. The dropping resistor shown in the 41Hz circuit won’t be necessary for the 317 part.
Roger |
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| soongsc |
| I've used LM317's in preamps before, and they never got warm. I never even added heat sinks. It also seems using the LM317 has more components. Is a sonic difference expected between the LM7805 and LM317? Also dropping 48VDC to 7.5~9V somehow that seems a lot. There is a limit the difference between input and output voltages these devices can handle, I don't recall LM317 can handle 48V to 5 V difference. |
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| sx881663 |
Yes, you are right, the 317 is maxed out at 40 volts. You would also be dissipating quite a bit more power with this much voltage across it. A substantial heat sink will be necessary. Not the same thing as when you use it in a preamp with 5-10 volts drop. A 2 watt 250 ohm resistor in series will take care of this.
I would expect better sound from the 317 as it is a better regulator.
Roger |
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| soongsc |
| The LM317 does have somewhat lower output impedance, but this seems to mak a difference when supplying analog circuits. I'm not sure what part of the AMP2 the 5V is supposed to supply, but if it's just digital (discrete) portion, then the difference might not be that significant. I'll look into it when I get the kit. |
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| theAnonymous1 |
I just finished the first of the three 5v supplies I need and I am very satisfied with how it turned out. Under a full load of 1.5 amps it only drops 10 millivolts.
The space between the input wires on the left and the small white cap is for a 47ohm resistor if I decide to use one. I didn't have any laying around so its jumpered with wire for now.
soongsc, the 5v is for the analog input section for both AMP1 and AMP2. |
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