This is truly a diamond in the rough. I am a big Hitachi fan, why? They made great stuff, from turntables to speakers and everything in between. This gem is no exception. Like it's fraternal twin, the SR-903, both seem to share the same genetics but differ cosmetically. I think both are great but, atlas I have the SR-904, which you could say is the updated version.
Service Manual is here: http://wegavision.pytalhost.com/HitachiSR-904s/
So, what makes this receiver so special? Well, it has to do with Hitachi Class-G topology and that fact that Hitachi used primarily Hitachi parts this receiver makes it a OEM special! So what's so special about the Class-G? Well, it has a 3 rail which allows additional voltage swings and increase peak power output at certain frequencies. NAD and Carver (remember the magnetic field power) used this same topology as well as many other Japanese manufacturers during the 80s. Unlike the Carver, this does not suffer from bad voltage swings due to a crappy power supply. In other words, It is one stable beast that sounds great. It also has the "Dyanharmony" badge!
It is rated at 75wpc into 8 ohms but, has a peak of over 100wpc when pushed. This makes the top end (treble) sound more vivid in some Classical pieces.
Cosmetically, it has the all so desirable VU meters and a cool green lights which doesn't show up nicely in daylight. It has plenty of features and a very nice midrange attenuator, which isn't commonly found very often in any receivers or amplifiers in comparison to the typical bass and treble.
It has the usual phono, aux, FM/AM and 2 tape inputs with loudness, high and low filters and stereo/mono buttons just like any receivers from the era.
Overall, it's in very nice shape, it does have a few small scratches and dings but, it still presents itself very nicely. It also has a read wood cabinet that's been vinyl wrapped! Oh well, but it sure looks nice!
This is a very nice sounding amplifier and well built. It sounds really clean and dynamic, and really it does sound like a NAD. I can't say if it's better or worse since I don't have any NAD gear but, it sure reminded me of it. Nonetheless, this is a excellent sounding piece of machinery.
Service Manual is here: http://wegavision.pytalhost.com/HitachiSR-904s/
So, what makes this receiver so special? Well, it has to do with Hitachi Class-G topology and that fact that Hitachi used primarily Hitachi parts this receiver makes it a OEM special! So what's so special about the Class-G? Well, it has a 3 rail which allows additional voltage swings and increase peak power output at certain frequencies. NAD and Carver (remember the magnetic field power) used this same topology as well as many other Japanese manufacturers during the 80s. Unlike the Carver, this does not suffer from bad voltage swings due to a crappy power supply. In other words, It is one stable beast that sounds great. It also has the "Dyanharmony" badge!
It is rated at 75wpc into 8 ohms but, has a peak of over 100wpc when pushed. This makes the top end (treble) sound more vivid in some Classical pieces.
Cosmetically, it has the all so desirable VU meters and a cool green lights which doesn't show up nicely in daylight. It has plenty of features and a very nice midrange attenuator, which isn't commonly found very often in any receivers or amplifiers in comparison to the typical bass and treble.
It has the usual phono, aux, FM/AM and 2 tape inputs with loudness, high and low filters and stereo/mono buttons just like any receivers from the era.
Overall, it's in very nice shape, it does have a few small scratches and dings but, it still presents itself very nicely. It also has a read wood cabinet that's been vinyl wrapped! Oh well, but it sure looks nice!
This is a very nice sounding amplifier and well built. It sounds really clean and dynamic, and really it does sound like a NAD. I can't say if it's better or worse since I don't have any NAD gear but, it sure reminded me of it. Nonetheless, this is a excellent sounding piece of machinery.
