PSU for a specific board level amp

[7F40]

Hello,

I am looking for a small project to build for a kitchen stereo. I found a detailed analysis of this board:

20W HIFI Mono Channel LM1875T Stereo Audio Amplifier Board Module DIY Kits | eBay

The review was very thorough and found it to be a good design for a small single channel amp. My plan was to get two of them, and pair it with a 25V PSU. I don't think it's good enough to justify an expensive PSU, but I still want to buy something safe.

Can anyone recommend a decently safe, inexpensive, dual-rail 25VDC PSU?

Thanks,

Brian

 

[FauxFrench]

Hello,

I am looking for a small project to build for a kitchen stereo. I found a detailed analysis of this board:

20W HIFI Mono Channel LM1875T Stereo Audio Amplifier Board Module DIY Kits | eBay

The review was very thorough and found it to be a good design for a small single channel amp. My plan was to get two of them, and pair it with a 25V PSU. I don't think it's good enough to justify an expensive PSU, but I still want to buy something safe.

Can anyone recommend a decently safe, inexpensive, dual-rail 25VDC PSU?

Thanks,

Brian

Hi Brian,

Unless you have a particular preference for class AB (LM1875) and want to improve this very simple board, I will recommend you something cheaper, equally good and with less problems. Buy a class D stereo board based on the TPA3116 or alternatively the TDA7498. Buy a cheap 19V laptop power supply "brick" and eventually add a 4700uF power line decoupling capacitor and you are done.

LM1875 can play very nicely but it has issues with stability, issues with "fake" chips (if cheap), requires a good heatsink, needs better supply line decoupling than shown and a symmetrical power supply. A symmetrical power supply is considerably more expensive than a standard 19V laptop "brick". So unless you really WANT LM1875, the class D solution is less expensive and less trouble.
Sound wise the TPA3116 or TDA7498 is very good, not perfect, but you say yourself that it is for the kitchen.

 

[7F40]

Buy a class D stereo board based on the TPA3116 or alternatively the TDA7498.

Hi FauxFrench,

Thanks for the reply. I need a 4 ohm unit, so I found this unit to be recommended with the TPA3116, and seems to require about 20VDC and 2A per channel:

DC 12-24V TPA3116 D2 100W Mono Channel Audio Power Amplifier Board for Car TE633 4894663151645 | eBay

I would be looking for a ~20VDC 4A PSU to drive two of these. I don't currently own any supplies of that voltage, so I will have to buy something. Do you have a recommendation for the PSU in this range?

 

[7F40]

Update: I was able to find this power supply with V+/- terminals that can output a max of 4.5A and it costs $17.87 at time of this post. This PSU, I think could be used with the LM1875.

https://www.digikey.com/products/en?keywords=lrs-100-24

For the TPA3116, I found this generic laptop supply on amaz for $25.90:

https://www.amazon.com/ZOZO-Univers...&sprefix=19v+laptop,toys-and-games,121&sr=8-5

All things being equal, that means I will have so far spent:

LM1875= $4 for amp boards + $17.87 for PSU = $21.87 (must include heatsink, which I already have many)

TPA3116= $20 for amp boards + $25.90 for PSU = $45.90 (no need to use any of my heatsinks)

So, I would ask if you had any opinion about these two options? Objectively, it seems like the TPA3116 will cost twice the LM1875. (assuming my chosen PSU is okay) Even if I include the cost of the heatsinks, it would still be slightly cheaper.

 

[FauxFrench]

Update: I was able to find this power supply with V+/- terminals that can output a max of 4.5A and it costs $17.87 at time of this post. This PSU, I think could be used with the LM1875.

https://www.digikey.com/products/en?keywords=lrs-100-24

For the TPA3116, I found this generic laptop supply on amaz for $25.90:

https://www.amazon.com/ZOZO-Universal-Notebook-Ultrabook-Chromebook/dp/B0132ST35Y/ref=sr_1_5?crid=33HCYWGWO0A08&keywords=19v+laptop+power+supply&qid=1569249863&s=gateway&sprefix=19v+laptop%2Ctoys-and-games%2C121&sr=8-5

All things being equal, that means I will have so far spent:

LM1875= $4 for amp boards + $17.87 for PSU = $21.87 (must include heatsink, which I already have many)

TPA3116= $20 for amp boards + $25.90 for PSU = $45.90 (no need to use any of my heatsinks)

So, I would ask if you had any opinion about these two options? Objectively, it seems like the TPA3116 will cost twice the LM1875. (assuming my chosen PSU is okay) Even if I include the cost of the heatsinks, it would still be slightly cheaper.

I have some other suggestions for a TPA 3116 amplifier with power supply.
As far as I can see, the nice Meanwell power supply you suggest for the LM1875 is single 24V and will not do. It needs to be a symmetrical power supply.

TPA3116 power supply suggestion:
2.5x5.5mm Laptop AC Adapters Supply Power Charger for Toshiba ASUS 19V 4.74A 90W | eBay

Amplifier suggestions:
DC 10-25V TPA3116D2 HIFI Digital 2.0 Dual Channel Stereo Amplifier Board 2x50W 822933247723 | eBay
DC 12V 50W +50W TPA3116D2 High Power Digital Audio Amplifier Board S8W2 194452631278 | eBay
https://www.ebay.com/itm/2x100W-TPA...=311567426011f60d743492b740d3b23b787ca4e94b7f
https://www.ebay.com/itm/2-0-HIFI-l...925369&hash=item3f6a41c390:g:XzsAAOSwknJXzX20
https://www.ebay.com/itm/DC-12V-24V...604560?hash=item2ad5345ad0:g:ShIAAOSwHX5dhwcR

The LM1875 boards you suggest will need 4x4700uf replacing the small ones presently on the board. What about volume control?

 

[7F40]

Hi FauxFrench,

Thanks for your feedback and suggestions. I have a couple questions from that.

As far as I can see, the nice Meanwell power supply you suggest for the LM1875 is single 24V and will not do. It needs to be a symmetrical power supply.

Okay, thanks for the info. I was confused because the power supply has four output terminals, two labeled 24v+ and two labled 24v-. Why would they have four terminals if it wasn't symmetrical?

The LM1875 boards you suggest will need 4x4700uf replacing the small ones presently on the board. What about volume control?

I am comfortable ordering and swapping out a couple caps if I get that one. For the volume, I was going to use a passive volume control between the devices and the power amp. (except for the turntable which has it's own preamp)

 

[FauxFrench]

Okay, thanks for the info. I was confused because the power supply has four output terminals, two labeled 24v+ and two labled 24v-. Why would they have four terminals if it wasn't symmetrical?
I understand your logic. Perhaps you can connect two LED strings. When you read the "Product Attributes" it becomes clear that it is 1 output with 24V.

I am comfortable ordering and swapping out a couple caps if I get that one. For the volume, I was going to use a passive volume control between the devices and the power amp. (except for the turntable which has it's own preamp)
OK with a passive volume control. You have thought about it. You talked for a start about a "kitchen stereo". Now you talk about a turntable (in the kitchen?). My impression was that you wanted a simple MP3 or Bluetooth setup to please your wife.

 

[avtech]

Okay, thanks for the info. I was confused because the power supply has four output terminals, two labeled 24v+ and two labled 24v-. Why would they have four terminals if it wasn't symmetrical?

Digi-Key (and others) use stock images for a product series, so the details on the image are not representative of the exact item you will receive.

HCC24-2.4-AG Bel Power Solutions | Power Supplies - External/Internal (Off-Board) | DigiKey

That is the cheapest 24v split rail PSU listed at 2.4A per side. Not cheap at $145 though...

 

[7F40]

OK with a passive volume control. You have thought about it. You talked for a start about a "kitchen stereo". Now you talk about a turntable (in the kitchen?). My impression was that you wanted a simple MP3 or Bluetooth setup to please your wife.

Hahaha. Yes, it's something like that. However, I also use the kitchen area to read and relax. I've been collecting turntables and such for a long time, so I always seem to have one to hook up. There is also a cassette deck, a tuner and a bluetooth connection that get heavy use by the lady.

 

[7F40]

Digi-Key (and others) use stock images for a product series, so the details on the image are not representative of the exact item you will receive.

I think that particular one is the right image. I did a google search for the model, and all images of it come up with the four terminal outputs and the +/- labels. I believe you all that it's not symmetrical, so there must be some other reason for it.

In any case, over $100 is super overkill for what I'm doing, but there seems to be some less expensive hobby boards out there. Anyone have experience with this:

LPS215A | Connex Electronic

Thanks,