Hello everyone. A few years ago I built a receiver where I put a preamplifier with a Rod Elliot circuit and a power amplifier with two LM3886s.
The problem is that the toroidal transformer that powers both the pre and the Lm3886 has burned out.
As a result of this search I found a switching power supply whose voltages are: +24 or 24-/6 A; +15 0 15- /1 A and +12v /1 A.
It adapts perfectly to what I need. The +12 v would be for the AM-FM board.
Would it be okay to use a source with these characteristics on an LM3886?
I appreciate your opinions.
https://www.aliexpress.us/item/3256....0.0.7aa038daXu2HFu&mp=1&gatewayAdapt=glo2usa
The problem is that the toroidal transformer that powers both the pre and the Lm3886 has burned out.
As a result of this search I found a switching power supply whose voltages are: +24 or 24-/6 A; +15 0 15- /1 A and +12v /1 A.
It adapts perfectly to what I need. The +12 v would be for the AM-FM board.
Would it be okay to use a source with these characteristics on an LM3886?
I appreciate your opinions.
https://www.aliexpress.us/item/3256....0.0.7aa038daXu2HFu&mp=1&gatewayAdapt=glo2usa
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I suggest a pair of Mean Well RPS-200-24 for the ±24 V. You can make +12 V with an LM7812 regulator IC. It's higher cost but also higher quality.
Tom
Tom
H
HAYK
I have the same PSU in 36v. The problem with multiple outputs the regulation is on one output and it is on +36v. I modified it to regulate upon 72v but you must destroy the warranty. I advise you if space is available to by 2 singles for less than $6 each.
https://aliexpress.com/item/4000138063768.html
https://aliexpress.com/item/4000138063768.html
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The supply you showed in your post should work great. I use two of these cheap 36V 5A supplies in series to produce a +/- 36 V supply on my LM3886 amps. $15 each from Amazon or you can find them on Ebay.
https://www.amazon.com/Dasiter-Converter-Step-Down-Isolation-Switching/dp/B089SPRTST
https://www.amazon.com/Dasiter-Converter-Step-Down-Isolation-Switching/dp/B089SPRTST
Have a look at the datasheet to verify, www.digikey.com has a link, but I think the maximum is near +/- 45 Volts for that chip. It says +/- 35 V is recommended to get you the full power output with an 8 ohm load. The chip does run a bit hotter at idle heating with higher supply voltages. I have ten channels of these in the house. Half run on +/- 24 V and the other run on +/- 36 Volt. I have one amp that has run at +/- 42 volts for many years. That power supply is available in 24V and 36V versions. As the outputs are isolated, you simply connect the outputs in series to produce the + and - supplies.
I don't know why you would want to mess with modifying a power supply board when you can just buy two of these or other supplies like this and use them as is.
Here's a picture of a stereo LM3886 board, left and two of those 24V power supplies back to back in a 3d printed box my son built last year.
I don't know why you would want to mess with modifying a power supply board when you can just buy two of these or other supplies like this and use them as is.
Here's a picture of a stereo LM3886 board, left and two of those 24V power supplies back to back in a 3d printed box my son built last year.
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H
HAYK
SMPS is regulated, but only one voltage can be considered at a time. The model that you selected, only +24v is considered. When the amp at low frequencies and negative output current is demanding, the supply doesn't see the demand as it is looking only +24v. I modified it so that it is regulating +24 to-24 instead of +24 to 0. You need to cut a track leading to 0v under the connector and add a 24v zener to the -24v out.
Unless your speakers are 4ohms, the 24v for lm3886 is very low.
Unless your speakers are 4ohms, the 24v for lm3886 is very low.
That's a nice and compact build for sure. I'm a bit concerned by the mounting of the switching power supplies, though. Unless the dielectric strength of the plastic is specified and you can guarantee that the pins of the SMPSes don't get too close to each other within the plastic, I would much rather want to see standoffs used to ensure proper clearance between the high voltage and low voltage sections of the SMPSes.
The heat sink seems sizeable but it's intended for forced air (fan) cooling. There doesn't appear to be any airflow through vent holes so I'd be a bit concerned about that too. I'm sure it works just fine as a desktop amp where it hardly ever delivers more than 100 mW, though.
Depends on the load impedance. ±36 V is fine for 8 Ω and above. For 4 Ω operation, I recommend staying at or below ±30 V. You can read my rationale here: https://neurochrome.com/pages/output-power
Tom
Hi Tom,
That's a 4 mm thick plate of PLA sandwiched between those power supplies. PLA is reported to have a dielectric strength exceeding 30,000 volts / mm, so I think it will stand off 125 VAC without fail.
This amp is running +/- 24 volt supplies into a pair of 4 ohm speaker and is successfully survived in a dorm room for more than a year, while generating a few noise complaints from the RA. So the vent slots in the side panel seem to be doing the job. As you well know one of the nice things about that LM3886 is that it has thermal and over current protection built in. If it ever gets upgraded to 36V supplies, as you suggested, a temperature controlled fan would be a good idea. I think a small one would fit on the back blowing right through those fins.
That's a 4 mm thick plate of PLA sandwiched between those power supplies. PLA is reported to have a dielectric strength exceeding 30,000 volts / mm, so I think it will stand off 125 VAC without fail.
This amp is running +/- 24 volt supplies into a pair of 4 ohm speaker and is successfully survived in a dorm room for more than a year, while generating a few noise complaints from the RA. So the vent slots in the side panel seem to be doing the job. As you well know one of the nice things about that LM3886 is that it has thermal and over current protection built in. If it ever gets upgraded to 36V supplies, as you suggested, a temperature controlled fan would be a good idea. I think a small one would fit on the back blowing right through those fins.
Ah. I couldn't see the vent slots. Yeah. The LM3886 is pretty rugged and with the internal heat sink you can let the heat sink temperature get up there. I've used CPU heat sinks (Pentium I ones are good) in the past during prototyping. The heat sink got up around 100-110 ºC but the LM3886 kept chugging along.
I bet a li'l 40 mm Noctua fan would work wonders should you ever need to get a little air moving across that heat sink. It doesn't take much airflow to make a big difference in the heat removal.
Tom
I bet a li'l 40 mm Noctua fan would work wonders should you ever need to get a little air moving across that heat sink. It doesn't take much airflow to make a big difference in the heat removal.
Tom