It should be a standard voltage regulator circuit because capacitance multipliers are best suited to low current (preamp) applications but check the Chinese schematic at #14 here: https://www.audiosciencereview.com/...d-1969-class-a-amplifier-off-aliexpress.3372/
The PNP thing is likely about better purchase deals and the novelty of it. I didn't hear anything special about the sound quality but maybe I'm not an audiophile who might notice it.
The PNP thing is likely about better purchase deals and the novelty of it. I didn't hear anything special about the sound quality but maybe I'm not an audiophile who might notice it.
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Hi @Ian Finch ,
Do you have memory of the bias current you or your friend used the amp with?
I'm wondering if the heatsinks are enough for at least 2A. My boxes are 4ohm and the 22V transformer the build seems to come with is a little higher than the recommended 17V (for 3ohms, per table).
Also: Is the bias current measured on the 220V AC input or the 22V after the transformer or rectifier 😕 ?
Do you have memory of the bias current you or your friend used the amp with?
I'm wondering if the heatsinks are enough for at least 2A. My boxes are 4ohm and the 22V transformer the build seems to come with is a little higher than the recommended 17V (for 3ohms, per table).
Also: Is the bias current measured on the 220V AC input or the 22V after the transformer or rectifier 😕 ?
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I would not have recorded bias current - just briefly checked that according to JLH's spec, it was enough for 10W with nominal 8 ohm speakers. Any class A amp. will distort if the bias is insufficient for the output voltage but that may only be noticed at sustained peak signal levels. Anyway, actual distortion shows up pretty clearly on the oscilloscope with just a steady tone signal, where it may go unnoticed just by listening to music program.
The product has been around in PNP, standard NPN and with various fake brand labels (my own amplifier is branded "Krell"!!) for several years now. Its hardware, transformer, case+heatsinks, connectors and semis are apparently much the same as the original NPN version of about 10 years ago. As far as 3 ohm speakers are concerned, I would avoid them with such a small amp and use higher nominal impedance, sensitive types for any affordable class A amplifier. Since you're obviously not power-crazy, good quality sensitive speakers of at least nominal 6 ohms will be key to getting the most enjoyment from your amp.
The product has been around in PNP, standard NPN and with various fake brand labels (my own amplifier is branded "Krell"!!) for several years now. Its hardware, transformer, case+heatsinks, connectors and semis are apparently much the same as the original NPN version of about 10 years ago. As far as 3 ohm speakers are concerned, I would avoid them with such a small amp and use higher nominal impedance, sensitive types for any affordable class A amplifier. Since you're obviously not power-crazy, good quality sensitive speakers of at least nominal 6 ohms will be key to getting the most enjoyment from your amp.
Actually it is exactly the opposite.
In a power amplifier, thermal noise is not really that problematic because the signal levels are relatively high.
But even if we don't consider this aspect, resistors are not really used in integrated circuits, but in general, in general, other solutions (eg: current sources) because resistors are very expensive to integrate.
A discreet design is, on the other hand, much more likely to capture ambient noise through capacitive and inductive couplings due to its tens-hundred times larger dimensions.
Plus, in an integrated design, all the components have the same temperature, they work in a temperature compensation system, and the thermal drift is minimal compared to a discrete assembly.
I don't know where you would hear such a "well-known fact" either. Perhaps it was a bit of sour-grapes internet chat from old-timers or kids parroting tales from a glorious past that never really was? One thing is certain though; the odds for class A being quieter than other audio classes of similar power are very slim when the supply current is constantly high and consequently at its noisiest in that mode. I can only think that the noise you guys refer to is actually distortion artefacts or perhaps poorly executed designs/PCBs. As an illustration of poor design, a local magazine version of the "Blameless" type amplifier wasn't performing like it should but its poor noise and distortion figures were vastly improved up to the text-book standard, just by changing the PCB ground layout, supply rails, feedback path and the quality of its connection terminals. It's not all about semi brands or circuit designers, you see 
.
A lot of nonsense comes from the desktops of folk who have only tinkered with components big enough to handle with klutzy fingers. Just the thought of using tweezers and probably losing the tiny, unobtanium ones somewhere in the carpet, is still a problem for most of us though, as you can tell by the popularity of Chinese DIY kits which thankfully, stick to TO92 minimum size semis where possible. I prefer to use bigger semis too but if I'm seriously looking for low noise, the circuits will probably wind up being built with SMDs on professionally designed, multi-layer PCBs.
.A lot of nonsense comes from the desktops of folk who have only tinkered with components big enough to handle with klutzy fingers. Just the thought of using tweezers and probably losing the tiny, unobtanium ones somewhere in the carpet, is still a problem for most of us though, as you can tell by the popularity of Chinese DIY kits which thankfully, stick to TO92 minimum size semis where possible. I prefer to use bigger semis too but if I'm seriously looking for low noise, the circuits will probably wind up being built with SMDs on professionally designed, multi-layer PCBs.
Combine high ripple with often poor power-supply rejection and this is the reason why class A amplifiers need regulated supplies.Ian Finch said:
Ed
A great basis for learning the basics, such as replacing screw connections with solder connections. Or the exchange of components. Or the decoupling of e.g. circuit boards and transformer. The result can be very different from the original: Super tuning to your conditions!
Regarding Classe A:
It is essential to distinguish single ended and push-pull!
A push-pull can in principle not be "high end" - contrasted to Single ended.
The push-pull example also shows "why class A sounds dead quiet". Just change the "bias";-)
Regarding Classe A:
It is essential to distinguish single ended and push-pull!
A push-pull can in principle not be "high end" - contrasted to Single ended.
The push-pull example also shows "why class A sounds dead quiet". Just change the "bias";-)