Early 70's watts vs. 80's watts

[swamppirate]

Dang this thread reads like War and Peace! Thanks for everyone's input, I have learned a ton!

 

[glen65]

Early 70's watts vs. 80's watts
I have a Sansui 5500 ( built around 1972) that is rated at 45 watts. When compared to 80's and 90's gear, the 5500 sounds more like 100 watts per channel. Were receivers in this timeframe rated differently, with different standards?

As some have already mentioned the real difference is simply the measuring standard. They have been doing the same thing with microwave ovens since the 80s.

 

[restorer-john]

...I believe the ratings are the same for the purposes of FTC. However I think the testing procedure has been relaxed. They now use a shorter duty cycle, 1/6 perhaps vs 1/3 back then...

When I read the amendments to the FTC rulings, all that had changed are the number of channels driven (allowing for AVRs/subs etc) and the preconditioning. Remember, the 1/3 power preconditioning (not duty cycle) was the killer back in the day as huge dissipation had to be dealt with for 1 hour, before the continuous RMS tests were commenced.

...One is the available current from the amp. Some (not all) newer amps and AVR's actually restrict current when the load dips to 4 ohms reducing the power it would have without current limitation...

Most 1970s amplifiers and receivers had very aggressive current limiting circuitry in the power amp stages. This was achieved usually by a gradual 'stealing' of drive from the drivers/output transistors as the required swings approached the design limit Ic or Pd limits of the SOAR curves of the output devices. It resulted in all sorts of dynamic compression artifacts, TIM issues, instability and general crushing of dynamics when speakers dipped low in their impedance curves at high volumes. Some circuits acted slowly, some fast, some didn't work at all, some worked too well. They were all horrible. What differs in most modern gear, is a hard limit current limit based on a single absolute value and that shuts off the amp/receiver. They also rely on the natural current limiting of a power supply that droops its rails and consequently limits the current than can be drawn.

Modern, post 1980, higher end gear completely eschewed current limiting in favour of hard limits and plenty of reserve dissipation capability.

Also there is peak power vs FTC ratings. Harmon Kardon and NAD, Perhaps others build some of their amps with 6 db's of headroom, while the average amp often has 1-2 db's headroom. This however should be taken with a grain of salt since IHF dynamic headroom is measured over just 10-20 ms. Still, we might get an extra 2-3 db's more power for music for longer periods from these rare amps.

NAD and Proton, Pioneer at one stage, Hitachi in the 1970s, Kenwood etc all built commutating rail amplifiers to allow for high short term power and keep the dissipation under control by running lower rails the rest of the time when transients didn't demand it. Many of those amplifiers were adorned with a rear-panel impedance switch. This tell tale switch either activates lower psu rails or adjusts the trip point for low impedance speakers. On modern AVRs, the rear panel switch usually selects a lower secondary HV rail to pro actively prevent excess dissipation and premature failure. I see those switches as 'cop-out' switches- excuses for poor design.

To my knowledge HK, never built a commutating rail amplifier in the 70s or 80s, nor did any of their designs subscribe to the peak power designs. HK specified clipping headroom, not dynamic headroom and it was a function of their tightly regulated and conservatively designed power supplies, completely the opposite to the designs and brands mentioned above.

As far as the 1kHz dynamic headroom tests, the specs for EIA are quite different to EIAJ, with the Japanese headroom test being much tougher IMO.

 

[whoaru99]

NAD and Proton, Pioneer at one stage, Hitachi in the 1970s, Kenwood etc all built commutating rail amplifiers to allow for high short term power and keep the dissipation under control by running lower rails the rest of the time when transients didn't demand it. Many of those amplifiers were adorned with a rear-panel impedance switch. This tell tale switch either activates lower psu rails or adjusts the trip point for low impedance speakers. On modern AVRs, the rear panel switch usually selects a lower secondary HV rail to pro actively prevent excess dissipation and premature failure. I see those switches as 'cop-out' switches- excuses for poor design.

Far as FTC amp rule, I believe 1/8 power preconditioning is now the standard.

With regard to the impedance switch, Audioholics did a story or two on that some time back. Their conclusion is that in many cases the switch is there to allow the amp to pass some temperature requirements of UL rating tests. Based on their testing though, they suggest to run the switch at the highest impedance setting despite the speaker load. They found the voltage and or current limiting imposed by the circuit actually is likely to contribute to more clipping and nastyness as people try to push them with the self-imposed restriction turned on.

 

[restorer-john]

Absolutely true. Agree 100%.

I have some very large TOTL integrated amps that have an impedance switch that drop the rails, and yes, in the interests of power and dynamics, I always have them at 8 ohms. I've tested them to full power at 2/4/8 on the higher rails and have no fear they will self destruct. Some gear however...

I'm just not going to give that advice to members of this forum because not all amps/receivers are well designed...

Far as FTC amp rule, I believe 1/8 power preconditioning is now the standard.

With regard to the impedance switch, Audioholics did a story or two on that some time back. Their conclusion is that in many cases the switch is there to allow the amp to pass some temperature requirements of UL rating tests. Based on their testing though, they suggest to run the switch at the highest impedance setting despite the speaker load. They found the voltage and or current limiting imposed by the circuit actually is likely to contribute to more clipping and nastyness as people try to push them with the self-imposed restriction turned on.

 

[bluesky]

70s watts sounded better!

 

[bluesky]

In my opinion, the vast majority of today's buying public have no idea about what a watt is, and RMS probably means even less.

I think that except for some quality high-end gear made today, nothing compares with the mass market stereo gear that was available in the late 1970s.

I use vintage gear, but I'm always wondering when some old component will reach the end of its useful life, and I'll have to get stuff fixed. If new gear was available at a price I could afford, I would seriously consider switching, providing the new gear had the quality of my old gear.

Isn't that the truth. :thmbsp:

Nothing lasts forever and the 'old gear' is 'really getting old' now. But... it still works and sounds fine!

1970 was 45 years ago. I've had some vintage gear just crash out hard, not cost effective to fix. For your favorite gear: just enjoy what you have and get it restored when the day comes I guess. Don't really want to think about it.

 

[Ed in SoDak]

A good clue on those 700 hunnert watt HT amps is how much they draw from the AC line. Can't get more out than coming in, not to mention the transfer isn't anywhere near 100% efficient due to having to power the circuit, lamps, etc.

My 70's Mitusbishi with dual overbuilt power supplies works for me! I don't know about the newer stuff, I simply quit looking after getting mine.
-Ed

 

[whoaru99]

It's certainly true that more can't come out than goes in, but problem with looking at back panel ratings is they're typically not given at full rated output power, only some part thereof, but then again it depends.

I always like to use the example of Yamaha M-80 since it's so clearly spelled out in the service manual. There are four different back panel ratings given for the same amp, depending on the intended market region. And, they're not small differences...600W, 850W, 1100W, and 1700W. In all regions the amp is rated 250/ch.

 

[Ed in SoDak]

Yeah, it's just a rough guideline and not indicative of much, but if it's only drawing say 135 watts AC for a receiver, no way can there be much more than half of that going to the speakers.

Now, my Mitsu briefly dims the room lights when I switch it on and those monster caps charge up. Now we're cookin'. :yes:
-Ed

 

[whoaru99]

FWIW, the back panel power consumption rating is listed at 1/8 of rated power on some gear. 1/8 rated power is the approximate average output wattage when an amp is playing music at the verge of clipping.

 

[swamppirate]

70s watts sounded better!

You may be on to something there... Seriously though, all of my 70's era SS gear is far better sounding than the "lighter" cheaply made stuff (aka, BPC) that was made in later decades.

 

[whoaru99]

You may be on to something there... Seriously though, all of my 70's era SS gear is far better sounding than the "lighter" cheaply made stuff (aka, BPC) that was made in later decades.

Do you consider that a realistic comparison? If I race a stock Corvette against a stock Chevette, should I be surprised when the Corvette wins?

 

[robgmn]

Do you consider that a realistic comparison? If I race a stock Corvette against a stock Chevette, should I be surprised when the Corvette wins?

Maybe he thinks 500HP out of a 1970 Chevelle is more powerful than 500HP out of a 2012 Corvette

 

[bd1886]

For a lot of music it just does.

70s watts sounded better!

My daughter called me up to have me bring her over something "better" for her vinyl. Out came a modern Pioneer HT receiver / small Polk Rti and in went vintage an Onkyo TX-4500 MKII / KLH Model Five's. (Her "ears" had her eyes and mouth smiling huge instantly.)

Son had a friend over that was into techno? Out came a Marantz 2385 / Dahlquist DQM 9c and in went Parasound and modern Energy / sub combo...and it made the vintage sound like "something tight lost" in trying to get it all out. (The new setup had fast and crisp coming at you incredibly well.)


We all can go on and on about switching things around, "What's the REAL watt output?", "....but what are the actual specs?" and all. It boils down to something about the difference in a simple "flavor aspect" to most and that can mean a slightly smoother / courser sound that moves physically through you with detail to......a sound that pierces you to continue on through (and to) the next carbon based unit!
A lot of us here have spent time learning what is right for ourselves and our listening, know the importance of specs to that end with "watts" standing a good chance of being important to the rest of our setup's requirements and what "we expect".


How it's all delivered and what our expectations require to that end is what keeps things all about the music, allows you to settle in and appreciate different rights. Delivery of wattage is what it's all about....not wattage. (Pi$$ing contests excluded.)