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Correcting Michael Fremer

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    Posted: 28 Apr 2019 at 9:11pm
This post replaces my earlier rant at Michael Fremer in response to his review of the Accession M phono stage. I would like to thank members for the support they extended to me in the now deleted topic.

In his review of the Accession M, Mr Fremer misread the instruction manual and spent most of the review suggesting I was in error.

He wrote that the manual said records have boost from 50Hz to 500Hz.

This is the actual extract from the manual: "... Both boosted the cutter head at 50 Hz all the way up to 500Hz; ..."

Please note that I said cutter head? I did not say the record.

The cutter head without feedback coils will simply be an inductive hump like this (these being simplified drawings)


Fig.1

Feedback coils cause its output to do this


Fig.2

Boost from 50Hz to 500Hz, then boost at the upper time constant (RIAA, NAB, FFRR etc.) does this


Fig.3

That is the output from a record played flat.

Unfortunately this confuses most people and also reviewers (and Wikipedia) because they only have experience of magnetic cartridges.

They cause the output from a record played with a magnetic cartridge to look like this


Fig.4

It is because a magnetic cartridge (MM, MI, MC) is 'constant velocity' (volts per hertz) and not 'constant amplitude' and that means its output increases as frequency increases.

If you connect a magnetic cartridge directly to a sensitive line input (one which obviously has a flat response) you will hear a bright scratchy sound with inaudible bass. Mr Fremer also takes issue with this, but try it and you will find it is correct.

A Nude Ceramic Cartridge

If you could play a record using a flat or 'constant amplitude' cartridge it will sound almost acceptable, and if anything quite the opposite to the above. It will sound this way because you are hearing the output of the record as in Fig.3 above. All that's missing is some EQ to take the step out of the middle.

This type of cartridge was known as a ceramic (or crystal) cartridge, and I had a lot of experience with these when designing circuits for disco preamps back in the 70s, so I should know.

However, most people, most reviewers, and it seems Wikipedia too, believe the output of the record is as Fig.4.

It is only as in Fig.4 if played by a magnetic cartridge, and that is because it is the combination of the rising output of the magnetic cartridge (volts per hertz) plus the response in Fig.3.

I will repeat that the output of a record is as Fig.3 when played with a constant amplitude or flat output cartridge (that is to say within its capabilities of flatness).

However, misinformation has it that I'm wrong - that the record's output is as Fig.4, - and the ceramic cartridge contains equalisation which makes it flat.

This is a complete fallacy or fabrication, and this is why I am showing you a nude or naked ceramic cartridge, and one of the most popular ones in audio history.

These images will hopefully quash the idea that a ceramic cartridge has a built-in equaliser.


Fig.5

The frontal view shows the stylus stereo pantograph along with its damping "pillows" (which decide its compliance). The left and right actuators couple the groove movements to the ceramic elements.


Fig.6

This side view shows the rear ends of the ceramic element housings with the "pos" output leads attached to them. The "neg" side outputs are metal pieces within the moulding. All four connections are brought to a socket at the rear, where a plug carrying the headshell wires plugs in, otherwise it's hollow.

This is an Astatic copy, but the original and identical Sonotone 9TA cartridges were manufactured in the 1960s and 1970s, long before surface mount miniaturisation. In other words, this cartridge DOES NOT CONTAIN AN EQUALISER!

Its output is constant amplitude, so within its frequency response capabilities, it outputs exactly what's on the record, FLAT! (as shown in Fig.3)

Because it has piezo-electric (ceramic) elements it does not conduct DC, and so appears capacitive. The actual value is between 600 and 800 pico-farads.

This has nothing to do with built-in EQ. When operated into a valve input having a one megohm grid resistor its bass is rolled off from around 200 Hz, period! Nothing else.

This was essential for its use as a record player cartridge, in preventing bass acoustic feedback from the built-in speaker back to the cartridge, and to prevent bearing rumble being heard.

When mounted on a good quality turntable such as a Garrard SP25 or BSR MP60 (good quality in their day), and loaded by 4.7 or 5 megohms, its bass roll-off is around 50 Hz, which is where an RIAA record has its short-lived bass boost to around 20 Hz (if in production the bass boost is made use of). This being illustrated by the up-flick at 50Hz in Fig.3.

The 12dB shelve-down of the record between 500 Hz and 2122 Hz (remember, this has a constant amplitude output) could be made up by fixed EQ (the Accession does it in exactly the same way!), or by treble control manipulation, which gave rise to the "boom and tssh" disco style.

Illustrations of Output Profiles

I do not have the fancy graphic drawing packages of journalists, their publishers, the marketing departments of big manufacturers, or Wikipedia. I am just an engineer, so I have to make use of what I have. Therefore the following illustrations are simply inversions and rotations of the plot I did of a phono stage response curve. That's a phono stage for a magnetic cartridge by the way!

It is in greater depth than what can be put into a product manual introduction. I can understand the non-technical being confused.

But facts are facts, and I suppose sometimes the truth hurts those who have been led to believe otherwise. But really, they should not show their ignorance in perpetuating misinformation.

The first image below is the output of the record, which is just the same as in Fig.3, but with curves as in reality, instead of the sharp corners used to illustrate earlier.

If played using a 'constant amplitude' device - in other words flat (flat like the output of a CD player and the like) this is the frequency response it will give.


Fig.7

As ceramic cartridges are no longer considered any good and today only exist on cheap record players, then I suppose the above is academic, but it isn't academic in describing that the first stage of the Accession gives this output. This output is available by switching to CA/Flat. The other EQs provided are not done in the conventional way!

The second image below shows the output from an RIAA record with the rising response of a constant velocity device added to it. In other words this is the response from a magnetic cartridge playing an RIAA record.


Fig.8

It seems Mr Fremer believes this is the actual output from the record, when in fact it is the homogenous combination of record and cartridge response.

This is why most will tell you that a ceramic cartridge has a built-in equaliser. I have proven from the previous post that it does not!

This last image is the response of a phono stage designed for RIAA reproduction using a magnetic cartridge. It is the inverse, not of the record's output, but the combination of the record and the constant velocity (volts per hertz) device - the magnetic cartridge!


Fig.9

I trust you follow me now?

Now, I could understand you saying where's your proof, as if the above isn't enough? So, as all good studies do, here are my references:

Disc Recording Equalization Demystified. G. A. Galo.
Audio/Radio Handbook 1980, National Semiconductor, pages 2.23 - 2.25



Edited by Graham Slee - 28 Apr 2019 at 9:22pm
Not simple enough for Google-Bot to understand...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2019 at 5:08am
The Reason For My Initial Rant/Outburst (now deleted)

After a stressful week, you're just about to put your feet up for the weekend, when you receive an email alerting you to the long awaited (4 years now!) Michael Fremer review of your MM flagship.

You don't quite fully understand the rest of the email, such is the excitement.

You frantically search the web - the email didn't provide a link - it just gave the title of the review "Graham Slee's $1449 Accession Raises the MM Playback Bar"

Google have the exact match in 1st and 2nd positions - so much for "Panda", "Penguin", or is it "Duck Billed Platypus" getting rid of exact match search results! To be in positions one and two this has to be hot news!

You head over there only to be met by Michael ridiculing you for something you never said, and preaching at you from Wikipedia, this taking up precious review mileage, and you go "Oh my God - it's the end for me"!

There are already comments nodding in agreement with him by people quick off the mark to accuse.

In blind panic you look at the email again, and misread it, sending the guy who sent it a reply that must have confused the hell out of him.

Then, with tired and failing eyesight you try to defend yourself - a stitch in time saves nine - but can you hell find the graphics which explain everything: the f'ing computer just sits there laughing at you as you struggle to find the right folder in 20 years of folders!

Destroyed, you vent your spleen at your US distributor for failing to spring to your defence, and he replies that he doesn't understand the product sufficiently to have done so.

YOU HIT THE ROOF!



Edited by Graham Slee - 29 Apr 2019 at 5:09am
Not simple enough for Google-Bot to understand...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BAK Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2019 at 12:44pm
"YOU HIT THE ROOF!"
All completely understandable.
Bruce
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Post Options Post Options   Thanks (0) Thanks(0)   Quote patientot Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2019 at 4:26pm
Thanks for the detailed explanation. Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Drewan77 Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2019 at 5:23pm
As a non-technical person, I read the Fremer review as a positive endorsement of the Accession & quite frankly, most of 'us' don't fully understand how it does what it does, but do understand what it does to music. That comes across quite strongly in the review, especially the conclusion which is what most people tend to remember afterwards.

Graham, I don't post so much these days but still watch what's going on & enthusiastically support your brand on a few other forums or face-to face when the occasion arises (also, David - Patientot is currently doing a great job on your behalf with the Accession!). 
Older than I once was, younger than I'll be
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Post Options Post Options   Thanks (0) Thanks(0)   Quote morris_minor Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2019 at 7:00pm
I read that review and could only imagine Graham's er, "disappointment" at it. The ironic thing is Fremer has always struck me as a "subjectivist" rather than an "objectivist". Hang the measurements, what does it sound like? So to go off on a rant at technicalities - that he obviously doesn't understand - doesn't seem true to form. Admittedly his conclusion was a sound one, but how many readers had he lost on the way? 

A comment on my latest video was

" went to a hifi show with a friend who took this CD with him to audition various systems. In most of the rooms we visited this track was blasted at loud volumes on some very expensive equipment and left me wincing at the coarse and strident sound that I heard. Listening to this on my Sennheiser HD600 headphones and tube amp combo the sound is far more refined, and mixing effects and subtle details can be heard that were inaudible on that occasion. It's like one is hearing a completely different piece of music."

That was the Accession MC at work. Even doing it's magic when hobbled by tube amp Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m3man Quote  Post ReplyReply Direct Link To This Post Posted: 05 May 2019 at 7:15pm
I am a big fan of Michael Fremer, and a happy owner of a Reflex C. So I was excited to see Fremer review the Accesssion, and now I am disappointed that his review contained so little information that is useful in helping me decide if an upgrade is in order.

What makes the Accession special is the fact that Slee has decided it was important to EQ the RIAA curve and the rising slope and from the magnetic cartridge separately. I was looking forward to hearing Fremer's evaluation of this technique and his opinion on whether it improves the sound.

Instead, I got 4 paragraphs of him contradicting Graham's explanation of response curves that was completely over my head, and therefore of zero interest to me. And instead of discussing whether this new EQ technique sounded better, he says "honestly, this is all news to me—I’ve never previously heard this discussed or mentioned anywhere." 

Now how often does a reviewer of phono pre-amps see a technology that has "never even been discussed before?" But instead of exploring it, he kisses it off with a "There are other theoretical advantages to doing it this way, but I’ll skip them for the purposes of this review." SKIP THEM? Sorry Mikey, I think that should have been the point of the review, and a much better use of those four wasted paragraphs.

Once he got down to the business of discussing how the unit sounded, he had nothing but good things to say. However, he spent most of his words on technology I don't care about, including 3 paragraphs on mono records. I own maybe 10 of those. I don't think I have any that need pre-1956 EQ curves.

Later, in the comments section, someone asks how it compares to a Reflex. All he could say is I "can't really say but I'd only consider swapping out if its functionality interests you." So does this mean it sounds no better than a Reflex?

Again, very disappointing. I like Mikey and respect his opinion. But in  this review, I never really heard his opinion about the things I care about, like, how will this impact the sound on my huge collection of stereo LP's. We didn't even get a comparison of it to another top notch phono pre. All we learned is that it sounds better than a $600 Project. 

His bottom line is that it is a fine unit. But I feel like I got a 4 page summary, when I was expecting that 400 page detailed report.

Mike, I'm still a fan. But this time, you let me down.  
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