Hitachi SR-604 Receiver

skrol

I have been trying to get rid of excess stuff lately and dropped off a Yamaha receiver and ADC eq at a small local thrift store. I like going in this place because I find goodies once in a while. Apparently most who drop stuff off are doing it for a little cash as times are hard. The owner was so pleased with the stuff I have been donating that he gave me a silver face Hitachi receiver from 1979 that I was eying. I tried to refuse it as I am trying to get rid of stuff but he insisted. He knows I like to fix stuff up and he said that this one was not working.

It is an SR-604, Class-G; whatever that is an was rather grimy to the touch. I got it home and found that the pots and switches needed a good cleaning, as did everything else, and it has some light out. DeOxit contact and fader cleaner to the rescue; it works great. I gave the rest a good cleaning and found a diamond under the dirt. This thing is like new. It didn't even have much dust inside. Now all it needs are a couple lamps and it is golden.

The Hitachi sounds quite nice with the Advent speakers that I recently restored. I may have a nice vintage system for a basement rig.

Anyone know anything about the Class-G amp?

skrol

Here is a pic.

mhardy6647

As I recall, Hitachi's "Class G" essentially used two sets of complementary (+ and -) DC power "rails" from the power supply, to allow short-term, higher-power operation to increase dynamic range/headroom available for signal peaks. These were fine components that were then and still are somewhat below the radar; they never quite "caught on" with the US mass-market hi-fi consumers like the bigger audio brands - despite the fact that Hitachi was (and still is, AFAIK) a huge Japanese electronics conglomerate, at least on par with Matsushita (actually even bigger, if memory serves).

heh, the only Hitachi Rx brochure scan I have handy is the next model up :-)


http://img.photobucket.com/albums/v223/mhardy6647/HitachiSR-703.jpg (the link isn't working for me - but it should...!

skrol

I think you are right. I believe Hitachi manufactured for other brands. So was the Class-G thing more of a gimmick or worth the while?

cnh

I've seen those Hitachi class Gs, but don't really have a working understanding of what difference that makes in amplification, if any (supposedly they are a design between A/B and D in their efficient use of power--more efficient than A/B but less than D) whether that translates into any improvement in sound (who knows)? I do own a couple of TOTL Realistic Tape decks that are rebadged Hitachi that are quite good for what they are. So lots of Hitachi parts and units around in that period!

Looks like a nice unit! From the appearance, yeah '79-80 makes sense. That's when most manufacturers used that kind of colored lighting for power meter displays.

cnh

mhardy6647

Not as much about efficiency per se as it was meant to provide, reasonably inexpensively, reserve power (headroom) when needed. I.e., don't build a P/S and amp for 200 watts continuous, but build one that really can deliver 200 watts for short durations when the signal dynamics and load sensitivity require it.

The above-mentioned Hitachi (three-head) cassette decks were very, very good - the R/S branded OEMs are, effectively, sleepers, as they don't have the cachet of a Tandberg or Nakamichi product - or even, say, an hk CD491 - but they don't cost like 'em, either! :-)