Somewhere (I think it was TAS) has a pretty thorough guide for alignment using a good test record like the HFNRR one.
Jan, does he still mention absurd achievable LP THD/IMD numbers? My fave the 10kHz 1/3 octave noise, "don't worry the low frequency crackle you hear is normal".
Actually, while Electrocompaniet did buy the rights to the original amp, they did change the design, and in my view, for the worse. All you need do is to compare the original paper with its measurements, which claim 0.5% THD at 100 kHz, with the commercial version to see the difference.
The fact that the original claimed a power rating of 25/50W into 8/4 Ohms, while the Electrocompaniet claims 25/40W into 8/4 Ohms, seems to indicate that the power supplies were also quite different. The article in IEEE has no schematics for the PSU, no voltage reguation schematics (the input stage and VAS were run off regulated +/-30V, the driver and output stage from unregaulated +/- 24V), and in the text it's said that for the sake of clarity, no protection circuits were shown.
In short, I would say that the Electrocompaniet only approximates the original, and I would suggest that the original was the better amp. Its only failing is in its really low output power, if it was say 50/100W into 8/4 Ohms, many people with more efficient speakers (say, 92 dB/2.83V/1m and up) would probably never need a better amp.
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So what's the problem? Instead of using the commercial 2 150W pairs per channel, use 4 200W pairs per channel, with a hefty PSU, and that's it.
You can never go wrong with more, but you sure can with too little.
Yeah, a little boy scout like. But that was in 1973 (I think?), and they really thought they had it all figured out.
They didn't, of course, but it is still marvellous to see how many things they did get right, perhaps even more than they were aware of.
I think it's a matter of perspective. While they obviously didn't have it all figured out, they did make the industry start to rethink its wicked ways as no other paper before them ever did, or so I think. This is its intrinistic value which would ripple through the industry ever after.
I never could believe any one single measure would guarantee good sound. I have always believed that to dance a waltz you had to know all the steps; miss or change some, and it's no longer a waltz, but it might be something else still worthwhile.
Thus, the headline is childlishy naive, even if I do believe low GNFB should be kept to around 20-26 dB, but to be able to do that, one needs to take quite a few steps in between.
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I don't really know. He has a separate website where he sells his turntables, and he has been announcing arms 'coming soon' for a few years now I think.
My interest is more in documenting the technical performance of turntables/arms/cartridge combinations. I plan to test a bunch of various concepts and executions, from expensive modern to oldies in original state and revisioned, and see what I come up with.
There's a guy here in Holland who tweaks the phase shift cap in AC turntable motors to get the phase shift at exactly 90 degrees and he had measurements from a spectrum analyzer showing very much quieter running with that mod. I should be able to corroborate his findings with Adjust+.
I mean, who cares what it sounds like - the measurement is important!
Jan
I find you guys 'second guessing' what was and still is a pioneering power amp design. It really was/is good! I own one today, and I owned another since 1976, and only lost it due to a firestorm. My original did do 100V/us, I know because I measured it myself.
This amp was a true breakthrough for me compared to virtually all other solid state amps made up to that time that were commercially available. I tried quite a number of Marantz, SAE, Quatre, and other solid state power amps that were available at the time. The only amps that might have beaten it were the upcoming JC-3 (ML-2 Levinson), or the Electro-Research by Jon Iverson. There were some Audio Research tube units like the 150, that could do as well or better, but they were priced very high.
There is 'magic' in this Otala inspired design, and you 'meter readers' should note that this amp still will beat most of today's amps sonically. It even can beat my equivalent level of design the A-23 sonically. Why, is controversial, but I think I know most of what is 'special' about this design.
This amp was a true breakthrough for me compared to virtually all other solid state amps made up to that time that were commercially available. I tried quite a number of Marantz, SAE, Quatre, and other solid state power amps that were available at the time. The only amps that might have beaten it were the upcoming JC-3 (ML-2 Levinson), or the Electro-Research by Jon Iverson. There were some Audio Research tube units like the 150, that could do as well or better, but they were priced very high.
There is 'magic' in this Otala inspired design, and you 'meter readers' should note that this amp still will beat most of today's amps sonically. It even can beat my equivalent level of design the A-23 sonically. Why, is controversial, but I think I know most of what is 'special' about this design.
Jan, as one who has taken much interest in the subject, I cannot promise, but I think I have the schematics of the Electrocompaniet somewhere, buried deep down in some old, fogotten log. I'll try to look it up and post a copy here, with the schematic of the original, so everyone can see for themselves.
BTW, I have also heard the story of their demanding that their names be taken off the fascia, because it was not the same amp, and Electrocompaniet never bought any right to using their name and/or their electronics. If Lohstroh says so, for me, that's it, that's the truth. I don't know him, but I sort of like him and certainly respect him.
I'll drink to that, John.
Exactly what I said a few messages ago. When you are shown how, it all becomes easy and obvious, and we forget all too often that it took somebody to show us how. Once we mastered the technique, got the hang of ot, it became "easy" and "obvious".
Also, please note one and all, Otala is far too often judged by that first amp. It seems forgotten that he subsequently spent years working for Harman/Kardon, and is often, right or wrong, credited with H/K's truly legendary Citation XX. The big, black behemoth, which could do 200 or 250W into 8 Ohms and was said to be capable of pumping out 200 Amps of current in peaks.
So, just to make things a little more fair, why not judge him by that amp, which came out 7 or 8 years later, and embodied what he had learnt in the meanwhile. Or, better yet, why not display your work which betters those?
The entire H/K and associated companies' work ever since then is literally based on Otala's views, but is not static, it has slowly and surely evolved since then. There aren't many who can boast to have influenced the industry so fundamentally, fingers of one hand with change. Richard Marsh with his fully complementary topology, James Bongiorno with his designs which were more or less copied no end by the industry even from his way back SAE days, and John has hardly passed by unnoticed, I have seen many more or less faithful copies of his Parasound work around. Add Otala & Lohstroh, and that's still less than there are fingers on a hand.
The original had much more feedback and less distortion, especially in the treble.
The Electro homed in on a meager 1.5% THD at 40kHz.
Hey, man, it had a 3 STAGE VOLTAGE AMPLIFICATION ( the Otalla - Lohstrom ).
The notion that the norvegian amps got such a good review although they where configured for only 20dB of NFB created that 30 year battle that only low feedback amps can have low TIM.
One of the clasical disasters of misunderstanding.
Put a fitting low pass filter and the TIM is gone. OK, the slew rate discussion....
The Electro homed in on a meager 1.5% THD at 40kHz.
Hey, man, it had a 3 STAGE VOLTAGE AMPLIFICATION ( the Otalla - Lohstrom ).
The notion that the norvegian amps got such a good review although they where configured for only 20dB of NFB created that 30 year battle that only low feedback amps can have low TIM.
One of the clasical disasters of misunderstanding.
Put a fitting low pass filter and the TIM is gone. OK, the slew rate discussion....
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