Hitachi HMA-8300 class G power amp

[stuwee]

I always wanted to hear one of these, interesting info on the class G circuitry in the ad

http://cgi.ebay.com/HITACHI-HMA-8300-CL ... 45fa221c54

 

[laatsch55]

Another example of a good idea implemented badly. IIRC the regulator circuits weren't up to the challenge.

 

[orange]

I have an SR-5010 'Class H' receiver.

 

[laatsch55]

Class "H" was an attempt to adjust the power supply voltage by a continous dynamic regulation instead of switching to set higher voltage rail as in class G, class G also required another set of outputs.

 

[stuwee]

So what made them unrealiable? I thought the design was clever.

Or, I might be remembering all the hoopla about the preamp HCA-8300?

http://cgi.ebay.com/Hitachi-Stereo-Cont ... 2eb4b5a625

 

[laatsch55]

Clever design yes, what inherent efficiencies were perpetrated were wiped out by the fact you had 2 separate SETS of outputs with 2 different SETS of power supply rails, the later class H (enhanced G whatever) went further with a constantly varying supply depending on the load. Ther are some other draw backs such as the PWM(pulse width modulation ) frequency needing to be in the MHZ region for Hi- Fidelity, and the chances of picking up RFI or EMI radiation grows exponentially as you leave the audio range. Need more detail??

 

[laatsch55]

A proper power supply is as much a component of the amplifier design as anything. An unregulated PS such as used in a class AB is not inherently inferior to any other design given the proper attention to ripple reduction and ultimately the amps power supply rejection ratio is the determining factor to the overall PS performance. It is also not more prone to rail injection of undesireables (RFI, EMI, etc.) as any other design given the proper construction details and techniques( proper uncoupling caps, separating AC/DC wire runs......etc.

 

[stuwee]

Excellent info many thanks!

 

[laatsch55]

Sure

 

[orange]

Class "H" was an attempt to adjust the power supply voltage by a continous dynamic regulation instead of switching to set higher voltage rail as in class G, class G also required another set of outputs.

What I know is that it's 25 wpc, 1979 and gets warm fast like Technics New Class A without the hybrid amp. That would predate 'non-switching' Pioneers like SA-1040/50 by around 4 years or so.

And if I'd have looked at my own picture it is ALSO a G.

The number of inputs is kinda sad anyway...only a tape loop and phono.

 

[nakdoc]

Soundcraftsman was the principal Class H proponent. All of these dual or variable rail schemes were attempts to make high power amps without the tremendous heatsink and transformers required to meet the US rules on power ratings. If we had never left the IHF and any method I want to make up days, we would still have simple amps, and the big amps would be heavy.

 

[laatsch55]

Thanks Nak. My thoughts exactly, except about the IHF.

 

[orange]

It WAS more fun having a 200 watt Pioneer or Fisher in 1968...they spoiled the fun?

Oh well, with the stuff played then would you notice?

(Oh, for the daze when your amplifier could smoke worse than YOU)

"The film of today's demonstrations we had planned to show you is not available so our our Action 5 Team will re-enact it for you now, with the help of Suburban Security's K-9 patrol, these are Charles and Fred with their dogs Ace and Justice"...

 

[nakdoc]

Thanks Nak. My thoughts exactly, except about the IHF.

How about a thread where we list all those old power rating acronyms? IHF was all I could think of. NAD earned their cohones when they dredged up "music power" and gave good reasons why it was a practical power rating method.

 

[stuwee]

Thanks Nak. My thoughts exactly, except about the IHF.

How about a thread where we list all those old power rating acronyms? IHF was all I could think of. NAD earned their cohones when they dredged up "music power" and gave good reasons why it was a practical power rating method.

A most excellent , would you honor us and start one?

 

[laatsch55]

you slow on the draw Stu.

 

[stuwee]

you slow on the draw Stu.

Yeah, I saw you posted the thread already, what you want a cookie or sumptin'??

 

[laatsch55]

Just a bow grasshopper.

 

[stuwee]

Just a bow grasshopper.

Don't make me go all Red Forman on ya