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Vintage amplifiers that could challenge or approach current state of the art amplifiers

March Audio

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Have you ever measured the noise on a components power rail?

No, I have not. I am not experienced in conducting measurements myself. The only measurements we conducted were with my engineer friend on the power distributor strip. He himself doubts the effects of such interference on music much like you.
That's because he, as a trained and educated EE, understands why there is not necessarily a correlation from one to the other. He understands the process by which the mains supply gets turned into a quiet supply for the electronics inside the box.

With respect you are using lay intuition to form your conclusions. No doubt biased by (erroneous) things you had read or been told from the audiophile community. Your subjective test conclusions can't be regarded as accurate because you used zero controls when making the assessment meaning bias will be a given.

Anyway this us the last point I will make as this is derailing the thread.
 
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gags11

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None of you guys are wrong.

grand piano + huge ballroom = beautiful sound
grand piano + anechoic chamber = shit sound

If you can imagine and agree with the above, the rest are all derivatives of the above.
 

murraycamp

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I have installed a parallel noise eater and ferrite clamps on the power cables to less the effect. The result is better imaging and greater tonal balance.

:facepalm:
 

sergeauckland

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I bought a bag of pure unrefined Quantums a few years ago when they were cheap and few people knew about them. Now, they have come into their own, and all my friends are amazed I can afford them.

Sometimes one just gets lucky.

S.
 

mhardy6647

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See, if he had used Quantum Purifiers, it would have been even better.
Quantum Purifiers are only good for digital.
We need Newtonian Purifiers for analog!
You read it here first, folks -- it's a marketing bonanza! Trust me on this one!!

:rolleyes:
 

mhardy6647

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oh -- on topic:

DSC_4301 (2).JPG


https://www.dix-project.net/item/10...ntasound-system-as-used-for-disney-s-fantasia

:cool:
 

RickSanchez

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So I'll add the Harman/Kardon hk670 to the thread because ... there are measurements! Ironically the measurements likely take it out of the running for "SOTA" compared to today's amps. (Just on power alone -- rated at 60W per channel, measured at 74W per channel -- this unit doesn't stand a chance.)
  • In the spirit of full disclosure I own one of these.

Measurements
Some highlights taken from the April 1979 edition (pages 47-50) of Stereo Review magazine. *Please note*: I cannot speak to the equipment that was used for these tests, nor how it compares with Amir's test equipment.
  • "The receiver's outputs clipped at 74.4 watts per channel into 8 ohms (IHF clipping headroom = 0..94 dB). The output into 4 and 16 ohms at clipping was 112.4 and 43 watts, respectively. The IHF dynamic headroom was 1.05 dB, corresponding to a short-term output of 76.5 watts into 8 ohms. The closeness of the clipping- and dynamic- headroom ratings indicates the use of well regulated power supplies in the hk670."
  • "The harmonic distortion of the hk670 at 1,000 Hz was extraordinarily low at most usable power levels. From less than 0.002 per cent at 0.1 watt, it increased smoothly to 0.003 per cent at 1 watt, 0.01 per cent at 20 watts, and 0.028 per cent at the rated 60 watts. The intermodulation distortion was about 0.028 per cent at power outputs from 1 to 10 watts. It increased at lower and higher outputs, to 0.08 per cent at 0.1 watt and 0.095 per cent at 60 watts."
  • "At rated power, harmonic distortion was under 0.03 per cent through the mid frequencies, rising to 0.04 per cent at 20 Hz and 0.05 per cent at 20,000 Hz. At reduced power, the distortion was consistently lower than at full power, with typical readings between 0.006 and 0.01 per cent over the entire audio band at normal listening levels."
  • "The hk670 evidently has a very effective system [in the FM tuner section] for removing the 19 -kHz pilot carrier from its audio circuits (no schematic was supplied, so we do not know if it uses a filter or a canceling circuit). The frequency response was almost ruler-flat-within +0.1, -0.2 dB from 30 to 10,000 Hz, rising to +0.4 dB at15,000 Hz. In spite of the fully maintained high -frequency response, the 19 -kHz leakage into the audio was a very low -69 dB. The tuner hum was an inaudible -71 dB."

1595506437630.png



1595506593057.png

(not my image)
 

tmtomh

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I bought a bag of pure unrefined Quantums a few years ago when they were cheap and few people knew about them. Now, they have come into their own, and all my friends are amazed I can afford them.

Sometimes one just gets lucky.

S.

I bought a bunch of those too. Problem is, I haven't been able to install them in my system because I can never seem to figure out for sure exactly where they are.
 

mhardy6647

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So I'll add the Harman/Kardon hk670 to the thread because ... there are measurements! Ironically the measurements likely take it out of the running for "SOTA" compared to today's amps. (Just on power alone -- rated at 60W per channel, measured at 74W per channel -- this unit doesn't stand a chance.)
  • In the spirit of full disclosure I own one of these.

Measurements
Some highlights taken from the April 1979 edition (pages 47-50) of Stereo Review magazine. *Please note*: I cannot speak to the equipment that was used for these tests, nor how it compares with Amir's test equipment.
  • "The receiver's outputs clipped at 74.4 watts per channel into 8 ohms (IHF clipping headroom = 0..94 dB). The output into 4 and 16 ohms at clipping was 112.4 and 43 watts, respectively. The IHF dynamic headroom was 1.05 dB, corresponding to a short-term output of 76.5 watts into 8 ohms. The closeness of the clipping- and dynamic- headroom ratings indicates the use of well regulated power supplies in the hk670."
  • "The harmonic distortion of the hk670 at 1,000 Hz was extraordinarily low at most usable power levels. From less than 0.002 per cent at 0.1 watt, it increased smoothly to 0.003 per cent at 1 watt, 0.01 per cent at 20 watts, and 0.028 per cent at the rated 60 watts. The intermodulation distortion was about 0.028 per cent at power outputs from 1 to 10 watts. It increased at lower and higher outputs, to 0.08 per cent at 0.1 watt and 0.095 per cent at 60 watts."
  • "At rated power, harmonic distortion was under 0.03 per cent through the mid frequencies, rising to 0.04 per cent at 20 Hz and 0.05 per cent at 20,000 Hz. At reduced power, the distortion was consistently lower than at full power, with typical readings between 0.006 and 0.01 per cent over the entire audio band at normal listening levels."
  • "The hk670 evidently has a very effective system [in the FM tuner section] for removing the 19 -kHz pilot carrier from its audio circuits (no schematic was supplied, so we do not know if it uses a filter or a canceling circuit). The frequency response was almost ruler-flat-within +0.1, -0.2 dB from 30 to 10,000 Hz, rising to +0.4 dB at15,000 Hz. In spite of the fully maintained high -frequency response, the 19 -kHz leakage into the audio was a very low -69 dB. The tuner hum was an inaudible -71 dB."

View attachment 74777


View attachment 74781
(not my image)

hk did some nice things over the years -- 'specially in the Matti Otala "low TIM" days (early '80s), I'd opine.

Identically one hk component from that era floatin' around here --

DSC_9171 by Mark Hardy, on Flickr

(plus some older things, predating that hk670 -- which was a nice receiver, if one graced with idiosyncratic cosmetics)
 

richard12511

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Listening enjoyment without stumbling over tonal imbalance does not qualify as 'the basic experiment'? How else should I determine my success in setting up a system, if my own ears cannot play a role in this?

Your ears can play a role, but your eyes and brain state need to be excluded.
 

richard12511

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Sorry, but how am I to agree to that? By this you are implying that neither the unpleasantness I heard before, nor my satisfaction should be taken as measures. Instead it would be wise for me to accept your judgement from a distance that my experience is a figment of my imagination. That's a tough call.

A tough call, no doubt, for you, but it's the truth. We don't hear with our ears; we hear with our brains. Ears are just one of the many inputs that goes into what we hear.
 

richard12511

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I heard the sonic imbalance (an unpleasant leaning towards the higher spectrum) and thought it was the speakers, the amp, whatever. Some weeks later a friend came over to test for distortion on my dedicated power line and we found that some had remained. Most tellingly there were periodic spikes that my friend said were typical of phase cutting and asked me if I had a switching supply somewhere. I pointed to my Cambridge DAC, and pulling the plug, the spikes were gone. I bought a linear power supply instead. The sonic imbalance was gone. Not sure if it was the switching itself or that the new power supply is simply stronger.

Most likely explanation is that it was just your imagination. The brain is very tricky like that.
 

murraycamp

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Back to OP-

I may have missed it but I'll add the NAD 2200 (although upgraded to 2600/2700-spec).
 
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RickSanchez

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... (plus some older things, predating that hk670 -- which was a nice receiver, if one graced with idiosyncratic cosmetics)

Yeah, I get a lot of those reactions to the hk670. Personally I love the look, but probably for mostly for sentimental reasons as it reminds me of my dad's old Fisher stereo amp. I don't remember exactly which one he had, but it might have been the RS 1020?
 

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Wes

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what is that Sherwood receiver that was all the rage a few years ago? It cost ~~$200 IIRC.

------

I hope Amir will be able to test some of the candidates in this 12 page thread. Maybe a compiled list would be good?
 
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