If this amp has a circuit the same as the original ST-120, one of the reasons it can sound as nice as it can is that it makes a fair amount of 2nd ordered harmonic. This, and the 3rd, if in sufficient amount, can mask the higher orders to a certain degree and result in a fairly smooth sounding amp unless you push it hard. Modern electrolytics seem to be a bit better than the ones used back in the 1960s and early 1970s; I'm sure that doesn't hurt either.
For my bedroom system I use an amplifier made by Radio Shack (SA-175C) that is very similar- the same circuit sans power transistors. It makes about 5 watts, but I never push it past one. At lower power levels its very smooth (and of course I've serviced it out) but it does get less polite at higher levels.
The key to working with amps like these is to make sure that the speaker is easy to drive and not low impedance. The low impedances should be avoided as they interact directly with the output coupling cap and can introduce low frequency phase shift which messes with bass impact. The ST120, being an early solid state design, is not very forgiving if you do something dumb like short out the speaker terminals, do anything adverse to its ability to cool itself or try to play it on a difficult load and get it really hot! But if you go easy on them they hold up quite well.
I've repaired many of the ST120s over the years- fixing consumer electronics is how I put myself through school. The amps seen at the website are a bit of eye candy- its nice to see someone really taking the time to do a neat job! IMO the insides are where the money that you spend on audio equipment should go. Its nice to see someone really taking pride in their work.
For my bedroom system I use an amplifier made by Radio Shack (SA-175C) that is very similar- the same circuit sans power transistors. It makes about 5 watts, but I never push it past one. At lower power levels its very smooth (and of course I've serviced it out) but it does get less polite at higher levels.
The key to working with amps like these is to make sure that the speaker is easy to drive and not low impedance. The low impedances should be avoided as they interact directly with the output coupling cap and can introduce low frequency phase shift which messes with bass impact. The ST120, being an early solid state design, is not very forgiving if you do something dumb like short out the speaker terminals, do anything adverse to its ability to cool itself or try to play it on a difficult load and get it really hot! But if you go easy on them they hold up quite well.
I've repaired many of the ST120s over the years- fixing consumer electronics is how I put myself through school. The amps seen at the website are a bit of eye candy- its nice to see someone really taking the time to do a neat job! IMO the insides are where the money that you spend on audio equipment should go. Its nice to see someone really taking pride in their work.