I suppose i could, but this was really a basic test evaluation to demonstrate the power output of the LM3886. The hum is virtually nonexistent and the freuency response is flat from 30-20khz (which I didn't show, sorry). I would imagine the THD would be close to the mfg's listed ratings.
Good question. If that's what i think it is, it's asctually just 1 power supply with the extra outputs connected in parallel to the screwdown wire terminals for convenience of wiring. I have a few supplies like that. There's 1 way to find out. If you have a multi tester meter, check contiuity between the 2 positive (+) terminals or the negative (-) terminals. If it checks a short between either of the 2 terminals, this means the psu just has extra terminals. Thus, you'll need an additional psu. Hope im wrong tho.
@@andresgamboa1275 ok, so you'll need to get a 2nd psu. If your psu has a metal case, make sure the negative terminal is not connected to the case. You can check that with your ohm meter.
Thanks! The relay circuit is just a relay coil in series with a 5 watt zener diode. I can further explain the circuit details but it's easier to just email you the schematic. My email is bob4analog@yahoo.com.
Off-the-shelf ones might have a lot of high frequency switching noise, but mostly its above the range of hearing, so it should be ok provided the amps are compensated properly so they dont oscillate given the high frequencies present. But if theres too much noise at the output it can damage tweeters. The amps can help somewhat depending on how they are set up given they still have 20-30 dB of CMRR at higher frequencies. Another consideration is the current, as these will only have around 3.5 amps peak (1.75 amps/channel), so they may not work well for 4 Ohm speakers. I used a flyback in my LM3886 amp, but of my own design so it could be bipolar, and be low noise with the appropriate bypassing and snubber networks, and fit onto one PCB so it just has a mains cord going into the cabinet. At the amp output the residual noise from the SMPS is down to around 20mV RMS. Power output is 36W RMS into 8 Ohm speakers.
Hi Bob, thanks for the video! What's the math behind adding the 10k resistor to make the SMPS go from 24 to 28.5 volts? Is there a practical limit to how low or how high the power supply can go?
Dave S - Yes, I'm sure there's math, but I didn't use any. Most SMPS can usually produce more voltage output by changing the error feedback voltage divider network. I managed to obtain a schematic of this PS, which helped. I still had to do a little 'reverse engineering' as well. With that and some experimenting, I managed to get 28v out of it. It will do a bit more, but I would need to replace output capacitors with higher voltage rating.
Hi Bob, I’m trying to do your idea with the two 24v switching but i add two step up voltage circuits that pull up the tension at 31v. What i’ve not understood yet, is how create negative voltage. It needs the relay to do this? Because at the pole of AC(in) amplifier i’ve only positive tension (+31v). Sorry i’m not well in electronic
Gday Bob, Great video mate, really got me inspired! Just curious, do you hear any of the lower order harmonic switching hash at all at quiescent levels?
Thanks, Mate! If you mean switching noise from the PSU, no; it actually sounds great. Have not heard any noise -- none that I noticed anyway. I was a bit concerned with using an SMPS, but I went ahead and built it anyway.. it worked. I kept the input away from the PSU inside to avoid any coupling of switching noise. SMPS are great for being light, small and can regulate wonderfully. Altho, I'd still rather have one with an 'iron supply' like I have in this vid... ua-cam.com/video/jJ6V0NjE6vg/v-deo.html - Cheers!
Is it possible to modify the power supply to work at 40v? I have a 16 ohm load that i want to drive using a 3886 for a guitar amp that i'm building. I actually already have one going with a 28-0-28 transformer but want to build a second one for a friend. These power supplies are much cheaper than a transformer!
I have another vid where I use 2 switching PSU's for the +/- rails. Yes, those are far less expensive than transformers. However, modifying them to do 40v per rail might be pushing the PSU's. I'd recommend finding a PSU that will do 40v or something close to that, then you can mod it for 40v from there. Hope that makes sense.
I like the SMPS in this vid. It's far less expensive and is not near as heavy. Altho the transformer type is simpler and does not present any issues with switching noise that's inherent in SMPS. :-)
Ciao, grazie di avermi risposto così presto, è una cosa che si apprezza di questi tempi!!! Mi spiego meglio io ho un TDA7498E MODULO DIGITALE CHE DEVO ALIMENTARE, ORA MI CHIEDEVO SE È MEGLIO UN ALIMENTATORE SWITCHING O LINEARE, E AVENDO UNO CON 10 AMPERE PIÙ DEL CONSIGLIATO PUÒ ANDAR BENE O RISCHIO DI FARE DANNI?? GRAZIE MILLE, E COMPLIMENTI PER I TUOI VIDEO, SONO DAVVERO CONTENTO DI TROVARE QUALCUNO BRAVO A SPIEGARE!!
TONY COMITA - Ok, grazie per la corretta comprensione. Registra il tuo alimentatore, se intendi regolato rispetto a non regolato, quindi regolato è meglio, indipendentemente se lineare o commutazione. Tuttavia, il passaggio è più efficiente. Ovviamente, il costo di commutazione degli alimentatori è economico, quindi è il migliore.
Really nice build Bob. sweet project for a rainy day.
Why don't you evaluate lm3886?
I like your way of doing this - compact, powerful, cheap. Can you do some noise measurements as well? How about hum and distortion?
I suppose i could, but this was really a basic test evaluation to demonstrate the power output of the LM3886. The hum is virtually nonexistent and the freuency response is flat from 30-20khz (which I didn't show, sorry). I would imagine the THD would be close to the mfg's listed ratings.
Nice amp Bob! Great project.
Tnx! Next, a SS 600w linear. ;-)
Hi Bob, i have a question, i have one switching psu with 2 out, (-V,-V,+V+V and gnd) 24 volt 5A , can i use? Or i need 2 separated psu? Thanks
Good question. If that's what i think it is, it's asctually just 1 power supply with the extra outputs connected in parallel to the screwdown wire terminals for convenience of wiring. I have a few supplies like that. There's 1 way to find out. If you have a multi tester meter, check contiuity between the 2 positive (+) terminals or the negative (-) terminals. If it checks a short between either of the 2 terminals, this means the psu just has extra terminals. Thus, you'll need an additional psu. Hope im wrong tho.
@@bob4analog yes, this tipe of power supply,
@@andresgamboa1275 ok, so you'll need to get a 2nd psu. If your psu has a metal case, make sure the negative terminal is not connected to the case. You can check that with your ohm meter.
@@bob4analog ok, like your video, thanks My friend
Hope it works ok for you. All the best! 😃
Thanks! I hope to use it as a modulator for a 100w AM. These are awesome ICs for audio.
Great budget idea! Thanks for the geat video, can you tell the relay circuit?
Thanks! The relay circuit is just a relay coil in series with a 5 watt zener diode. I can further explain the circuit details but it's easier to just email you the schematic. My email is bob4analog@yahoo.com.
How clean was the DC that these smps made? Doesn’t smps have a lot of ripple if not built for audio?
Off-the-shelf ones might have a lot of high frequency switching noise, but mostly its above the range of hearing, so it should be ok provided the amps are compensated properly so they dont oscillate given the high frequencies present. But if theres too much noise at the output it can damage tweeters. The amps can help somewhat depending on how they are set up given they still have 20-30 dB of CMRR at higher frequencies. Another consideration is the current, as these will only have around 3.5 amps peak (1.75 amps/channel), so they may not work well for 4 Ohm speakers. I used a flyback in my LM3886 amp, but of my own design so it could be bipolar, and be low noise with the appropriate bypassing and snubber networks, and fit onto one PCB so it just has a mains cord going into the cabinet. At the amp output the residual noise from the SMPS is down to around 20mV RMS. Power output is 36W RMS into 8 Ohm speakers.
Hi Bob, thanks for the video! What's the math behind adding the 10k resistor to make the SMPS go from 24 to 28.5 volts? Is there a practical limit to how low or how high the power supply can go?
Dave S - Yes, I'm sure there's math, but I didn't use any. Most SMPS can usually produce more voltage output by changing the error feedback voltage divider network. I managed to obtain a schematic of this PS, which helped. I still had to do a little 'reverse engineering' as well. With that and some experimenting, I managed to get 28v out of it. It will do a bit more, but I would need to replace output capacitors with higher voltage rating.
Hi Bob,
I’m trying to do your idea with the two 24v switching but i add two step up voltage circuits that pull up the tension at 31v. What i’ve not understood yet, is how create negative voltage. It needs the relay to do this? Because at the pole of AC(in) amplifier i’ve only positive tension (+31v). Sorry i’m not well in electronic
The power supplies are connected in series, like 2 batteries. The ground is where the 2 batteries (or power supplies) are connected together.
I'll be glad to send you the schematic of how i made it (if i haven't sent it to you already).
Gday Bob,
Great video mate, really got me inspired!
Just curious, do you hear any of the lower order harmonic switching hash at all at quiescent levels?
Thanks, Mate! If you mean switching noise from the PSU, no; it actually sounds great. Have not heard any noise -- none that I noticed anyway. I was a bit concerned with using an SMPS, but I went ahead and built it anyway.. it worked. I kept the input away from the PSU inside to avoid any coupling of switching noise. SMPS are great for being light, small and can regulate wonderfully. Altho, I'd still rather have one with an 'iron supply' like I have in this vid... ua-cam.com/video/jJ6V0NjE6vg/v-deo.html - Cheers!
Is it possible to modify the power supply to work at 40v? I have a 16 ohm load that i want to drive using a 3886 for a guitar amp that i'm building. I actually already have one going with a 28-0-28 transformer but want to build a second one for a friend. These power supplies are much cheaper than a transformer!
I have another vid where I use 2 switching PSU's for the +/- rails. Yes, those are far less expensive than transformers. However, modifying them to do 40v per rail might be pushing the PSU's. I'd recommend finding a PSU that will do 40v or something close to that, then you can mod it for 40v from there. Hope that makes sense.
hey bob. which one is better between this and the other power supply you use for lm 3886?
I like the SMPS in this vid. It's far less expensive and is not near as heavy. Altho the transformer type is simpler and does not present any issues with switching noise that's inherent in SMPS. :-)
Would you recommend this as a subwoofer amp for home use?
Elnufo - Yes, within its power range, it should be excellent for a subwoof.
Thanks a lot :-)
Elnufo - Certainly! Will be interesting to know how it worked for you.
ST540 power test/review please
Thanks for the suggestion! I'll give it a go.
@@bob4analog Thank you Sir!
Per Un amplificatore digitale è meglio un alimentarore swiching oppure uno stabilizzato?
TONY COMITA - Sì, ma non sempre necessario. Notare che LM3886 non è un amplificatore 'digitale' PWM; è una classe AB.
Ciao, grazie di avermi risposto così presto, è una cosa che si apprezza di questi tempi!!! Mi spiego meglio io ho un TDA7498E MODULO DIGITALE CHE DEVO ALIMENTARE, ORA MI CHIEDEVO SE È MEGLIO UN ALIMENTATORE SWITCHING O LINEARE, E AVENDO UNO CON 10 AMPERE PIÙ DEL CONSIGLIATO PUÒ ANDAR BENE O RISCHIO DI FARE DANNI?? GRAZIE MILLE, E COMPLIMENTI PER I TUOI VIDEO, SONO DAVVERO CONTENTO DI TROVARE QUALCUNO BRAVO A SPIEGARE!!
TONY COMITA - Ok, grazie per la corretta comprensione. Registra il tuo alimentatore, se intendi regolato rispetto a non regolato, quindi regolato è meglio, indipendentemente se lineare o commutazione. Tuttavia, il passaggio è più efficiente. Ovviamente, il costo di commutazione degli alimentatori è economico, quindi è il migliore.
Ok, grazie ancora!
TONY COMITA - Anytime! ;-)
please help me sir..I want to develop 180 watt smps
Vikrant Patil - That's not too difficult. so, 180 watts, for what voltage?
Hi BoB H, which rail does the relay switch on? Pos, Neg, or the Gnd rail?
The relay is connected across both rails. It will only activate when both supplies are up.
Thanks.
@@raytempo6332 - ;-)