Reviewing the Furutec Demag

[ack]

There are many ways to have mono material, and Amir's approach is pure, SIMPLE, and sound: you take L1+R1 material and first create L1+L1 - there is nothing complicated about it - this is, in fact, better than using a true mono LP because a stereo cartridge playing said LP will exhibit differences between its two coils, therefore to do it right with a true mono LP you also need a mono cartridge, mono preamp, etc - there is nothing simpler and more predictable than Amir's approach, I hope that's clear.

Then you take L1+L2 and as long as they are perfectly aligned in time and were generated with the same parameters, you have another mono outcome, and apparently according to Amir of different amplitude between L1 and L2. I guess if you don't like it, you don't like it.

For some of us, these experiments prove what we already knew of this and other tweaks (see other thread) - plain unworthy, if not detrimental.

 

[Orb]

There are many ways to have mono material, and Amir's approach is pure, SIMPLE, and sound: you take L1+R1 material and first create L1+L1 - there is nothing complicated about it - this is, in fact, better than using a true mono LP because a stereo cartridge playing said LP will exhibit differences between its two coils, therefore to do it right with a true mono LP you also need a mono cartridge, mono preamp, etc - there is nothing simpler and more predictable than Amir's approach, I hope that's clear.

Then you take L1+L2 and as long as they are perfectly aligned in time and were generated with the same parameters, you have another mono outcome, and apparently according to Amir of different amplitude between L1 and L2. I guess if you don't like it, you don't like it.

For some of us, these experiments prove what we already knew of this and other tweaks (see other thread) - plain unworthy, if not detrimental.

Ack, I think we are coming from different perspectives on this and so will let it drop.
However please take the time to look at what Jim Lesurf did and consider why his approach was to keep the two channels seperate, even if what I am saying you feel is not relevant.

Apologies but probably best if I stop posting in this thread, you say no difference and it is simple; yet a pro audio engineer who was also a physics lecturer at St Andrews notes same behaviour as Bruce - quoting the page I linked:

The above graphs is as the previous one, but for the other channel.
It is interesting to note that the apparent change in power level before-after is, for both channels somewhat greater than when we compared unfiltered versions of the the before and after samples.
Indeed, it should be noted that I had to increase the power-range plotted from around 40dB to around 70dB for the above plots and this should be taken into account when comparing these results with the previous graphs.
Overall, the results may indicate that the reduction in noise is greater at frequencies above 150Hz than below.
The results are interesting in that they do seem to support the claim that the surface noise level is reduced.

While this was not demag, it was a vinyl solution test to look for exactly same thing; why if any improvement to sound before and after.

Thanks again
Orb

 

[amirm]

Thanks Ack.

Just adding on, I am trying to analyze the signal so the kind of "mono" I created is not meant to be the way you normally create mono. I am interested in comparing one channel at a time and also to check their subjective levels. Hence the method I used. The assumption being that if a device improves sound, it should improve each channel also.

 

[amirm]

Ack,
I am trying to understand why and the implications of creating a psuedo mono recording.

It is as I said, to compare a single channel at a time which studies have shown to be more revealing than stereo.

I feel if wanting a mono, then a true mono LP recording should be used where those issues associated with stereo recordings do not apply (I think as its only L+R)

Which we don't have here. But again, any improvement should manifest itself into a single channel just the same.

Anyway, I am trying to understand how creating a psuedo mono does not add complexity, a case in point is does Jim Lesurf (audio engineer and also a physics lecturer at St Andrews) go through this process in the link I provided?
Furthermore he mentions using higher pass filter as a further analysis.
From what I understand he keeps the two channels seperate for a before/after comparison.
http://www.audiomisc.co.uk/VinySol/vinysol.html

For listening tests, I did exactly what he did. Even though I created a composite of the two left channels, for listening I would mute one channel and listen to the other and go back and forth.

He however did not attempt to compare the subjective levels which is what I tried to do. He is just running analysis on each channel which can be done of course with one channel at a time.

Looking at Jim Lesurf's analysis (last 2 graphs), notice how channel 1 and 2 are quite different from each other for both before and after, how do you make a psuedo mono from that behaviour without changing it?
Bear with me as I appreciate I may be missing something here.

Thanks
Orb

Let's start with the fact that Jim's test is really faulty . You can't use an MP3 to make these comparisons. I realize those are the only files he had from the vendor. But really. MP3 compression corrupts transients, rolls off high frequencies, and raises the noise floor. The vendor is really at fault for releasing MP3. The only reason to actually analyze and MP3 of the output would be if there were gross differences like different music used, wildly different levels and such. I would not expand the waveform and try to read anything into it.

in that sense, the kind of analysis we are doing is far more rigorous than what he tried to do.

BTW, let me repeat again that I am just doing something very simple: listening for level differences.

 

[mep]

The vendor is an idiot for releasing MP3.

Why Amir, that sounds like something I would say and then be promptly chastised and have my post removed. And you didn't even put a smiley at the end of the sentence. At least in your first sentence when you said that Jim's test was "really faulty," you put a smiley there to help soften the blow.

 

[amirm]

Why Amir, that sounds like something I would say and then be promptly chastised and have my post removed.

I probably should have used a better word there (I will edit and correct). That said, I have a lower bar for people who trying to sell something using faulty data than fellow members who are simply here to have fun and do not need to be called names.

And you didn't even put a smiley at the end of the sentence. At least in your first sentence when you said that Jim's test was "really faulty," you put a smiley there to help soften the blow.

I am showing differing levels of respect for the two: one is trying to do good with his analysis, the other is distributing non-sense trying to make a buck. Emoticons do have value here .

 

[mep]

I am showing differing levels of respect for the two: one is trying to do good with his analysis, the other is distributing non-sense trying to make a buck. Emoticons do have value here .

I get it Amir. I'm starting to read your smiley faces like a book. One thing you have to keep in mind is that all people on this forum don't come here for the same defintion of fun. Some people's idea of fun is to constantly bully other people and try to discredit their point of view. Some of these people have a well-established track record of causing hate and discontent on every forum they haunt until they are banned.

Back to the topic at hand. Haven't there been studies done in the past that showed that playing an LP causes the vinyl to temporarily deform as a result of the stylus pressure and the heat generated in the grooves? I think I even remember seeing pictures from an electron scanning microscope that showed the groove walls before and after playing. If someone really wants to test the effect of the Furtech demag device, maybe the test should be spread out over a 24 hour period of time if using the exact same LP. Day one record the LP before it has been demagged. On day two, demag the Lp and record it again. I think you have conclusively shown that the variances between two successive plays swamps anything that the demag process might have accomplished.

 

[Orb]

I get it Amir. I'm starting to read your smiley faces like a book. One thing you have to keep in mind is that all people on this forum don't come here for the same defintion of fun. Some people's idea of fun is to constantly bully other people and try to discredit their point of view. Some of these people have a well-established track record of causing hate and discontent on every forum they haunt until they are banned...

Hi Mep,
I hope this was not directed at me, it may be unfortunate timing but it seems to have come after my recent posting.
It was only in PMs it was clarified that the right channel is discarded, thanks Amir for taking the time to go over this - was appreciated.
Anyway to clarify and this is really last time posting this thread so not to distract.
I feel I should clarify the Jim's website as some have taken it too far with a few comments, my point was to highlight his approach in analysis and not the flawed mp3, specifically how to look at before and after splitting the channels and also his comment relating to using a filter for analysing higher FR, and while at a high level he feels there may be something about reducing noise level.

The 2nd point I want to say is that the horizontal (mono or in-phase L+R) and vertical modulation (difference information L-R) are integral to both left and right channel , therefore it makes it rather tricky to completely isolate one channel from the perspective of whats going on especially for perception test, although I do agree one channel can be useful but not conclusive.
I.e. can it be said it is not the sum of both channels and their behaviour/performance that is possibly affected, or making changes if any more noticable?

And also compounding this is the difference in performance a cartridge can have for left and right channels (was the other link of Jim's page I included).
So while some may feel it is conclusive using a perception test relating to just the left channel duplicated into stereo is fine, it may not cover all what is happening - This is not directed at Amir but some who may feel such a mono test will resolve the discussion.

Thanks
Orb

 

[mep]

Orb-my comments had zero to do you with you. We're fine.

 

[Bruce B]

The original file that we did at the PNWAS meeting was in mono (Ella and Louis). So no need to drop and match tracks.

 

[garylkoh]

Back to the topic at hand. Haven't there been studies done in the past that showed that playing an LP causes the vinyl to temporarily deform as a result of the stylus pressure and the heat generated in the grooves? I think I even remember seeing pictures from an electron scanning microscope that showed the groove walls before and after playing.

Yes, I recall something like that. Amir's test is the first I've come across that shows that you can actually HEAR these differences with the vinyl deforming. This is likely going to be something that I will put into my "Something I (or someone else) can measure, but I can't hear" cigarbox.... because doing ABX testing, I certainly can't hear any difference between Cut2 and Cut3, or Cut 2 and Cut4. Initially, I thought I heard a difference between Cut1 and Cut2, but testing again, I think that I lost that difference.

If someone really wants to test the effect of the Furtech demag device, maybe the test should be spread out over a 24 hour period of time if using the exact same LP. Day one record the LP before it has been demagged. On day two, demag the Lp and record it again. I think you have conclusively shown that the variances between two successive plays swamps anything that the demag process might have accomplished.

I can do that.... but I don't know what it will prove. As it is, the variances between two successive plays swamps anything that the demag process does (if I am reading Bruce's and Amir's results correctly) - so if it does, doing the demag the next day and recording may not make a difference. Even with the CutX and CutD, I thought I heard a difference, but with more protracted listening, I can't hear a difference anymore.

But..... there's always the possibility that there's something that the demag process does that is so subtle that it can't be captured by the 24/96 PCM recording process

 

[garylkoh]

The original file that we did at the PNWAS meeting was in mono (Ella and Louis). So no need to drop and match tracks.

If anybody is still interested, I can go back to the mono Ella and Louis LP and do this all over again - including recording a cut one day and then recording the same cut the next day to see if some of these play-to-play variances go away...... but I'm out the office next week so this will have to wait.

 

[Bruce B]

But..... there's always the possibility that there's something that the demag process does that is so subtle that it can't be captured by the 24/96 PCM recording process

Time to break out the DSD128fs!

 

[garylkoh]

Time to break out the DSD128fs!

Yeah! But then if we post those files, no one will be able to play them

 

[amirm]

Time to break out the DSD128fs!

That's a ploy to put me out of business with my freebie PCM editing tool!

 

[garylkoh]

That's a ploy to put me out of business with my freebie PCM editing tool!

Then Bruce will have to do all the work because I'm using Audacity too - and I don't have a DAC that can play back DSD files.

By the way, did you listen to CutX and CutD? Did you hear a difference?

 

[amirm]

I had to tear up my audio workstation to fix the broken TacT processor. I managed to get it barely working and listening through the TacT driving my NHT monitors, I hear no difference. OK,I keep thinking there is a tiny difference in highs with X having a bit more of it but I can't confirm it in repeated plays. Once I get my DAC and headphones hooked up again, I will give it another listen. For now though, if there is a difference, it is extremely small.

 

[garylkoh]

I had to tear up my audio workstation to fix the broken TacT processor. I managed to get it barely working and listening through the TacT driving my NHT monitors, I hear no difference. OK,I keep thinking there is a tiny difference in highs with X having a bit more of it but I can't confirm it in repeated plays. Once I get my DAC and headphones hooked up again, I will give it another listen. For now though, if there is a difference, it is extremely small.

Thanks, Amir. I thought the same, a tiny bit more highs in CutX and Cut1 than all the other cuts. However, as Bruce mentioned in your thread on Perceptually erasing Differences, I thought that I heard much more of a difference pre- and post- demag when I wasn't paying attention - standing behind an acoustic panel taking care of equipment.

Whatever it is, I think that I'm comfortable that for my tastes sighted or blind, demagnetizing an LP isn't worth the 30 seconds of delay in cueing up the music

 

[Lee]

I've done some analysis and added some screenshots to show everyone what is happening.

Take 1-4 had approx. 20sec of music. Lining them up and taking a snapshot of 00:00:00:000 and another at 00:00:20:000 produced a variance of 2-3ms. Also taking a snapshot of 1-2, 2-3, 3-4 showed varying degrees of difference as shown


Take 1-2 zoom 5ms
Take 1-2 zoom 1ms
Take 2-3 zoom 5ms
Take 2-3 zoom 1ms
Take 3-4 zoom 5ms
Take 3-4 zoom 1ms

Now, the before and after Demag

Take X and D zoom 5ms
Take X and D zoom 1ms

Now for statistical parameters of Takes 1-4
and

Takes Before and After Demag

Cool stuff Bruce.

 

[Gregadd]

[video]http://www.aolhealth.com/2011/02/24/magnetic-boy-7-attracts-electronic-and-metal-objects/[/video]

speaking of magnetic.