written by Diabeticblues on 09/03/2020
I don't know how the other reviewers here listen to music but this amplifier is, compared to its peers, not particularly good. Starting with the bass it is rather ponderous and one note. Not really a great sound and certainly no great extension. The bass seems to start at 50 hz and seems to have a high Q in and around this point so that no matter what you play into it the sound at the bottom end isn't particularly Hi-Fi. Further up and the mids and treble is rather hard and harsh. Compared to a Denon or a Marantz for example, the sort of amps this is going to be compared with, you will find that the upper mids and the treble is not the smoothest. So, what is wrong with this amp? Well from an engineering point there are several key areas that would really help it and I have performed this modification on a couple of them now so I think I know what I am doing! First is an upgrade to decent main smoothing capacitors which are low ripple types so fitting 10,000uf 63 volt caps off the circuit board makes all the bass confusion go away. I use Vishay caps with additional polyester caps in the vacated PCB holes to help the high frequencies. At the same time the thickness of the PCB tracks is pretty poor so thickening them with tinned copper wire such that the tracks are able to carry some current helps a lot too. If Sony had bothered to tin the board it would have helped but hey, its a cheap amp! The Sanyo output module is missing some parts. Actually if you look at the internals of the STK4211 II module it is somewhat different from the V version but the issues in its use are more or less the same so the parts that are shown for the V can be installed for the II as they do the same sort of thing even though the earlier module is missing the current mirrors sources in the long tail pair. But this little mod cures the nasty mids and treble. Other mods do help but are not exactly huge in their changes to the amp. First is a pair of polyester caps across the zeners that provide the low voltage supplies for the preamp circuits and at the same time the feed resistors need the same thing here too. This has the effect of lowering the noise floor of the entire amp for pennies and is effective at the phono input. Likewise if you change the M5218 op-amp (I am using an OP275) in the phono circuit you can get better sound from your turntable. So does it now sound like Hi-Fi? It is significantly better. I have one sitting here in my workshop with a pair of tiny Celestion F1 bookshelf speakers that have Peerless bass drivers and Monacor tweeters which I use as my near field monitors and we now have bass that stops and starts, that work great with drums and allows the midrange to open up without the dense and confused sound that was the original sound. Further work involves fitting an IEC mains socket, earthing the chassis, PAT certification, and the possibility that I might add in some extra buffering between the input selector IC and the tone controls as I think it could be further tweaked here. I only paid £12 for my second hand one on EBay so value is largely void!
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