Hi,
I'm on track to build a GC amp (3886), and struggling to make a choice on the final schematics (and therefore partlist). My main reference is A Complete Guide to Design and Build a Hi-Fi LM3886 Amplifier from Circuitbasics, but the article kind of skips the PSU design.
In advance, my apologies for a question thats sounds (even to me) like a heresy
Why build a PSU including a toroidal transformer (weighing like, 1.X kg ?) when a simple DC adapter like phone charger might do the job ?
Knowing that the transformer's job is to convert AC 230V (I'm in France) to xx V DC, my dumb Samsung charger might be enough ?
Then, why these chargers aren't so heavy ?
If I had to guess, I'd say this has to do with voltage requirements and stability in the signal (but then again, smartphones electronics should require precise voltage ?) or interferences ?
I'm on track to build a GC amp (3886), and struggling to make a choice on the final schematics (and therefore partlist). My main reference is A Complete Guide to Design and Build a Hi-Fi LM3886 Amplifier from Circuitbasics, but the article kind of skips the PSU design.
In advance, my apologies for a question thats sounds (even to me) like a heresy
Why build a PSU including a toroidal transformer (weighing like, 1.X kg ?) when a simple DC adapter like phone charger might do the job ?
Knowing that the transformer's job is to convert AC 230V (I'm in France) to xx V DC, my dumb Samsung charger might be enough ?
Then, why these chargers aren't so heavy ?
If I had to guess, I'd say this has to do with voltage requirements and stability in the signal (but then again, smartphones electronics should require precise voltage ?) or interferences ?
Hello
key "word" here is - power...
The phone charger has a output power of only 10-20W (V *A) ( low weight as these are SMPS) Laptop chargers has a capacity of 40W-90W....but you need dual voltage for gainclone...For stereo amplifier based on LM3886 you need ad least 200-250 W PSU. Does not matter with transformer or SMPS.
Some gainclone info regarding power/load /voltage :
Building a Gainclone chip amp power supply.
key "word" here is - power...
The phone charger has a output power of only 10-20W (V *A) ( low weight as these are SMPS) Laptop chargers has a capacity of 40W-90W....but you need dual voltage for gainclone...For stereo amplifier based on LM3886 you need ad least 200-250 W PSU. Does not matter with transformer or SMPS.
Some gainclone info regarding power/load /voltage :
Building a Gainclone chip amp power supply.
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Why not a DC adapter for an LM3886 amplifier?
Because your amplifier does probably need a symmetrical (+/-) supply voltage.
Because a DC adapter cannot supply sufficient power for a stereo LM3886.
Because a DC adapter does not include sufficient supply line decoupling (capacitance).
The chargers are light-weight because they use SMPS techniques, not a transformer.
Smartphones use 5V+/-0.25V as I recall it. Nothing for your amplifier.
Because your amplifier does probably need a symmetrical (+/-) supply voltage.
Because a DC adapter cannot supply sufficient power for a stereo LM3886.
Because a DC adapter does not include sufficient supply line decoupling (capacitance).
The chargers are light-weight because they use SMPS techniques, not a transformer.
Smartphones use 5V+/-0.25V as I recall it. Nothing for your amplifier.
Thanks FauxFrench & Osscar for your replies, this is crystal clear (and a bit more obvious now for me !).
Although I do have an additional question.
Leaving the realm of GainClone, I've ordered a 6n3 tube preamp kit on eBay to get a grasp on soldering & board logic (picture below).
It's sold with mention : " Operating voltage: AC12V / above 1A " (no mention of required power).
Should a power supply like this one suffice ?
No. of Outputs:
1 Output
Output Power Max:
18W
Output Voltage - Output 1:
12V
Output Current - Output 1:
1.5A
Input Voltage AC Min:
90V
Input Voltage AC Max:
264V
Plug Type:
EU
Although I do have an additional question.
Leaving the realm of GainClone, I've ordered a 6n3 tube preamp kit on eBay to get a grasp on soldering & board logic (picture below).
It's sold with mention : " Operating voltage: AC12V / above 1A " (no mention of required power).
Should a power supply like this one suffice ?
No. of Outputs:
1 Output
Output Power Max:
18W
Output Voltage - Output 1:
12V
Output Current - Output 1:
1.5A
Input Voltage AC Min:
90V
Input Voltage AC Max:
264V
Plug Type:
EU
An externally hosted image should be here but it was not working when we last tested it.
Your citation "Operating voltage: AC12V / above 1A" hints that the preamp kit is supplied from a 12Vac supply (transformer) which is likely to be rectified into a DC voltage, probably around 18Vdc. If so, a 12Vdc will not be sufficient.
Can you show us information about the preamp? Then, we may have a chance to figure out what supply to use.
Can you show us information about the preamp? Then, we may have a chance to figure out what supply to use.
Hello Bromatofiel
Sadly there is a lot of unnecessary overcomplication surrounding amplifier designs. Recently I made Mick Feuerbacher's two resistor 3886 amp: Mick Feuerbacher Audio Projects
I have listened to it for a month now and I find it to be sonically superb.
This is it in a wooden box, the aesthetics are of no concern to me, I listen in a room away from our home.
And no I do not get any RF interference
Or any humming.
Cheers
Sadly there is a lot of unnecessary overcomplication surrounding amplifier designs. Recently I made Mick Feuerbacher's two resistor 3886 amp: Mick Feuerbacher Audio Projects
I have listened to it for a month now and I find it to be sonically superb.
This is it in a wooden box, the aesthetics are of no concern to me, I listen in a room away from our home.
An externally hosted image should be here but it was not working when we last tested it.
And no I do not get any RF interference
Or any humming.
Cheers
In some cases you can use two laptop bricks to power a chip amp. You will need to connect the power supplies in series and take the ground from the centre between the two.
Do note that this setup requires complete galvanic isolation between input and output of the supply, which not all laptop bricks offer. In some cases, the negative output is connected to protective earth. In these cases, putting two laptop bricks in series will short circuit the negative supply.
Tom
Do note that this setup requires complete galvanic isolation between input and output of the supply, which not all laptop bricks offer. In some cases, the negative output is connected to protective earth. In these cases, putting two laptop bricks in series will short circuit the negative supply.
Tom
It can be done, but the switching supplies are tricky. Apply caution!
hacking the power supplies
hacking the power supplies
A pair of MEANWELL IRM-60-24 can be stacked in place of a traditional transformer for LM3886 based builds, and perform very well in many applications. Pretty attractively priced compared to a toroid and a couple of bridge rectifiers too-
IRM-60-24 MEAN WELL | Mouser PCB style
IRM-60-24ST MEAN WELL | Mouser Terminal style
They should be readily available at the usual suppliers, even in the EU.
IRM-60-24 MEAN WELL | Mouser PCB style
IRM-60-24ST MEAN WELL | Mouser Terminal style
They should be readily available at the usual suppliers, even in the EU.
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Thank you all for your replies !
. Aside cost & building convenience, are there major pros & cons vs. home-made PSU ?
@FauxFrench : hope this is conform with rule #8 of the forum, but here is a link of the initial preamp description. The vendor is a bit scarse of details... (this was mainly an attempt at getting familiar with a preamp composition).
@Lingwendil : interesting component, thanks for the tip, although it takes off a bit the DIY spirit
. Aside cost & building convenience, are there major pros & cons vs. home-made PSU ?
Trust me, you do NOT want to DIY an SMPS@Lingwendil : interesting component, thanks for the tip, although it takes off a bit the DIY spirit
Consider buying and using a ready made one same as buying a ready wound toroid instead of a naked core, a few spools of different sized wires plus insulating paper, tape, coloured wires and mounting bolts and washers and then winding your own.
The DIY side resides in building the amp itself, and in general making the whole project work properly, which by itself is a complex enough task.
Hello Bromatofiel,
I can see that you live in a city, great places for scrap yards, I go into them and am always very polite to the staff. Last time I went I asked for 'those alloy things with fins on and I don't mind stripping them out". They sold me the stuff for it's weight ridiculously cheap.
Cheers
I can see that you live in a city, great places for scrap yards, I go into them and am always very polite to the staff. Last time I went I asked for 'those alloy things with fins on and I don't mind stripping them out". They sold me the stuff for it's weight ridiculously cheap.
Cheers
Thanks for the link.
"9.Power requirements:±12-15V DC power supply 10W above transformer;
filament require 12V more than 2A". This is what I found below on the page.
I did not find your citation of 12Vac, min.1A.
Thus, as I assume this to be your pre-amp, you need 12V/2A and symmetrical 12-15V. I know little about tubes but I assume the 12V to be for the filament and not particularly critical with precision or noise.
For the 12V/2A, use any (reasonable) DC 12V/3A adapter. It won't cost much.
The symmetrical 12-15V is a bit more difficult to find. The noise must be reasonably low but you need only some 500mA. Do you already have such a symmetrical supply?
"9.Power requirements:±12-15V DC power supply 10W above transformer;
filament require 12V more than 2A". This is what I found below on the page.
I did not find your citation of 12Vac, min.1A.
Thus, as I assume this to be your pre-amp, you need 12V/2A and symmetrical 12-15V. I know little about tubes but I assume the 12V to be for the filament and not particularly critical with precision or noise.
For the 12V/2A, use any (reasonable) DC 12V/3A adapter. It won't cost much.
The symmetrical 12-15V is a bit more difficult to find. The noise must be reasonably low but you need only some 500mA. Do you already have such a symmetrical supply?
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Quote from above site "In particular in this design the use of an input coupling cap is avoided. If you want to build this amp, be however careful if you are not sure if the preceding stage in your system has output coupling caps. If it has not, DC may enter the amp, which will be amplified and sent to your speakers! Also, be careful if you have difficult to drive speakers. The amp has no Zobel network or any other stabilizing components."
you or someone else may think differently when the speakers blow due to DC or MHz oscillations...
After building over a hundred amplifiers for myself and others over the last dozen years, I've become a firm believer in coupling caps at the input of the majority of applications. I've repaired many systems and speakers that were damaged by DC on the input, all could have been avoided by a simple 10 cent part.
Stability components are another thing that should not be thrown out likely. Some amplifiers may measure much worse without them due to oscillation and have reduced power output, along with even destroying other components.
I fixed a gainclone a buddy built years ago, it was stable and sounded great in most loads, until the owner hooked it up to a set of vintage klipschorns. After first powering them up and the subsequent oscillations blowing the main woofers due to excessive excursion, I was tasked with fixing it. I added the components shown in the application notes, and it worked great into all loads after that. The speakers themselves were still broken, of course. That was an expensive lesson for the original builder, who thought that simply following a project schematic he found on DIYaudioprojects was enough, and didn't understand the IC.
Well, they're good enough for Tom at Neurochrome, but he adds some additional bits to them, and offers up a nice kit-
SMPS-86
Hopefully he or some users of them can comment further. I use them for constant max-load with LED drivers for aquarium/agriculture lighting setups. They are very reliable, and surprisingly quiet.
With adequate capacitance they will work well in typical audio applications, and are no less DIY than adding bridges to a pre-wound toroid if you really get into thinking about it
Stability components are another thing that should not be thrown out likely. Some amplifiers may measure much worse without them due to oscillation and have reduced power output, along with even destroying other components.
I fixed a gainclone a buddy built years ago, it was stable and sounded great in most loads, until the owner hooked it up to a set of vintage klipschorns. After first powering them up and the subsequent oscillations blowing the main woofers due to excessive excursion, I was tasked with fixing it. I added the components shown in the application notes, and it worked great into all loads after that. The speakers themselves were still broken, of course. That was an expensive lesson for the original builder, who thought that simply following a project schematic he found on DIYaudioprojects was enough, and didn't understand the IC.
@Lingwendil : interesting component, thanks for the tip, although it takes off a bit the DIY spirit
Well, they're good enough for Tom at Neurochrome, but he adds some additional bits to them, and offers up a nice kit-
SMPS-86
Hopefully he or some users of them can comment further. I use them for constant max-load with LED drivers for aquarium/agriculture lighting setups. They are very reliable, and surprisingly quiet.
With adequate capacitance they will work well in typical audio applications, and are no less DIY than adding bridges to a pre-wound toroid if you really get into thinking about it
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Hello ctrix,
May I show you with great respect the whole quote from Mick's text.
In particular in this design the use of an input coupling cap is avoided. (you forgot this bit, which was the first thing I noticed after making and trying the amp) "This greatly improves clarity and transparency, in particular if the preceding stage has output coupling capacitors".
Cheers
May I show you with great respect the whole quote from Mick's text.
In particular in this design the use of an input coupling cap is avoided. (you forgot this bit, which was the first thing I noticed after making and trying the amp) "This greatly improves clarity and transparency, in particular if the preceding stage has output coupling capacitors".
Cheers
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