With so many cheap Chinese amps available I can't have been the only one tempted to buy something ready made. So rather than completely hi-jack a thread about building amps I thought a new one about what people have bought or are thinking about buying would be good. including pre assembled PCB.
I've bought but it hasn't been delivered yet an Amp claiming to be a 12 watt per channel JLH 1969 Class A amp in two cases one for power supply one for the amp. All is not quite as advertised though - as has since been pointed out to me the heat sink is too small for 12watt class A amp. A closer look at some of the photos shows a pair of OP Amp chips next to the volume pot View attachment JRC5532-JRC.pdf
Here's the Amp
LP Spirit Pure Class A 1969 Amplifier Computer Desktop Mini Merge Split Type HIFI Audio Power Amp|audio power|power ampa class amplifier - AliExpress
We've all seem tube amp hybrids - this looks more like a 1969 JLH hybrid now. It might even deliver the claimed 12 watt per channel what do you think?
I've bought but it hasn't been delivered yet an Amp claiming to be a 12 watt per channel JLH 1969 Class A amp in two cases one for power supply one for the amp. All is not quite as advertised though - as has since been pointed out to me the heat sink is too small for 12watt class A amp. A closer look at some of the photos shows a pair of OP Amp chips next to the volume pot View attachment JRC5532-JRC.pdf
Here's the Amp
LP Spirit Pure Class A 1969 Amplifier Computer Desktop Mini Merge Split Type HIFI Audio Power Amp|audio power|power ampa class amplifier - AliExpress
We've all seem tube amp hybrids - this looks more like a 1969 JLH hybrid now. It might even deliver the claimed 12 watt per channel what do you think?
I don’t see any heatsinks capable of 12w Class A operation. The same vendor also sells a 1969 JLH class A amp that appears to have the correct sized heatsinks here.
US $189.00 | 2019 New Class A Hood 1969 Amplifier MJ15025G MJ15024G Stereo HiFi Power Amp 10W+10W Finished
2019 New Class A Hood 1969 Amplifier MJ15025G MJ15024G Stereo HiFi Power Amp 10W+10W Finished|power amp|hifi power amphood 1969 amplifier - AliExpress
If you read specs of the one you linked, it says power consumption is 27w yet output is 12w per channel or 24w. Now 24w/27w is Class D efficiency. Something is fishy with this amp’s description.
It’s probably Class AB and Class A for the first 1W or so. I have the same little heatsink on my other projects. It’s good for no more than 10w of dissipation.
US $189.00 | 2019 New Class A Hood 1969 Amplifier MJ15025G MJ15024G Stereo HiFi Power Amp 10W+10W Finished
2019 New Class A Hood 1969 Amplifier MJ15025G MJ15024G Stereo HiFi Power Amp 10W+10W Finished|power amp|hifi power amphood 1969 amplifier - AliExpress
If you read specs of the one you linked, it says power consumption is 27w yet output is 12w per channel or 24w. Now 24w/27w is Class D efficiency. Something is fishy with this amp’s description.
It’s probably Class AB and Class A for the first 1W or so. I have the same little heatsink on my other projects. It’s good for no more than 10w of dissipation.
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Nope. As said previously, you'll probably get about 5W/channel from a pair of TIP41 power transistors in class A output stages. This is what we find with other, simple PCB only kits featuring TO220 size power transistors. The second part of the power problem is bias current and the necessary heatsink size to dissipate the power. A tiny box like that would be roasting hot trying to dissipate the necessary 70 or so watts heat for 2 x 12W output continuously and I don't see enough unimpeded air flow through that single heatsink, that would be sufficient for even half that.
The seller is using peak, single channel ratings to make the power claims but doesn't state how much distortion you would get at those peak levels, even if possible. Also, 27W power consumption for 24W output is absurd when even class D can't get that close to perfect efficiency. I don't follow the +/-23V output claim either but it's meaningless without context anyway.
I'd like to think this is all a translational problem but perhaps the seller thinks they can just wave desirable numbers at customers and they will buy anything that has a nice picture to fill in the credibility gaps. That's why I DIY or at least check the physical design and testing wherever possible.
The seller is using peak, single channel ratings to make the power claims but doesn't state how much distortion you would get at those peak levels, even if possible. Also, 27W power consumption for 24W output is absurd when even class D can't get that close to perfect efficiency. I don't follow the +/-23V output claim either but it's meaningless without context anyway.
I'd like to think this is all a translational problem but perhaps the seller thinks they can just wave desirable numbers at customers and they will buy anything that has a nice picture to fill in the credibility gaps. That's why I DIY or at least check the physical design and testing wherever possible.
The problem I was having trying to buy a cheap amp was that the class D stuff all starts at 50watt per channel and upward for not much more than $50 US in many cases but that's way to much power for my needs on this occasion. So i've picked up something that looks reasonably well made for quite a bit more money.
But I hope this thread stays active so that others can get the benefit of the wisdom on this forum. I'd like to see what horrors or not other people find - preferably before purchase. I did watch a guy on youtube open up a valve amp to find no transformers at all just dummy spaces for them and heat sink with transistors on it. It was reckoned to be a hybrid amp so the tubes had some function but appearances totally faked for tube looks.
Interesting that the Opamps on the amp i'm getting are socketed - Just looking at reviews on Burston Opamps there may be some fun to be had with this amp at a later date swapping stuff out after all hacking stuff is a good way to learn too.
But I hope this thread stays active so that others can get the benefit of the wisdom on this forum. I'd like to see what horrors or not other people find - preferably before purchase. I did watch a guy on youtube open up a valve amp to find no transformers at all just dummy spaces for them and heat sink with transistors on it. It was reckoned to be a hybrid amp so the tubes had some function but appearances totally faked for tube looks.
Interesting that the Opamps on the amp i'm getting are socketed - Just looking at reviews on Burston Opamps there may be some fun to be had with this amp at a later date swapping stuff out after all hacking stuff is a good way to learn too.
Looks like just another piece of alibaba garbage in a snazzy box, with the typical snazzy marketing literature.
I conclude that the nicest part of all those junkers is the box, only the box.
They're known for that superficial touch.
I conclude that the nicest part of all those junkers is the box, only the box.
They're known for that superficial touch.
It uses an inexpensive $ 2 component with a power of 3-5 watts.
TIP41C Mono Amp Mini Board Assembly 1 Channel Pure Class A
Some components D, when powered by 12V, have a power of 18W \4 Ohm in bridge connection.
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Well it turned up today. I've hooked it up to my Cambridge DAC magic plus and put the big Carfrae horns the other side. It's blindingly good. I've had it cranked up all afternoon from James Horner Pas de Deux to U2 Joshua tree and on to Peter Gabriel Last temptation of Christ. It's fast and sweet and had my toes tapping away all afternoon whilst working. Yep It is a very nice box but what's inside is delivering the goods too. Stats for this model are all over the place in different adverts. It might well be class A just very much lower watts than advertised. The case is getting warm but just that, not hot like an ACA. I've bought it as part of a present to go with some speakers that won't handle high watts. More than happy to pass this on as being safe enough (no glass tubes or high temps) for my sisters family home - kids from 8 to 14. Paired with Decaware Tiny radials i'm building it should rock at xmas!