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  #1  
Old 15th July 2006, 11:04 PM
Primalsea Primalsea is offline
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Default Turntable Signal to Noise Ratio

How is this measured on a turntable ?
(I know how to calculate it from the measurements).

I guess you must have a test record and cartridge with known signal to noise ratios at a particular reference level. Then use them on a TT and measure the output and compare it to the test signal.

Now I know that tech specs often have no bearing on subjective sound quality. However whats confusing me is the S/N ratios being quoted by many TT manufactures. There should be a reference quoted for the test signal overwise the spec is meaningless. All S/N specs for turntables don't mention the reference signal. Is there a standard reference that I can't find or is this another example of the misleading info given out buy manufacturers.

I ask this because Clearaudio often brandish S/N ratios of 84db (with no reference) Pro-ject Audio TT's have much lower S/N ratios even for their best TT's, and again no reference. This means that it is quite possible that Pro-ject TT's could actaully have similar S/N ratios to Clear Audio TT's depending on the refernce used.

I know that many people won't find this post very interesting but I was hoping that there are some other sad people out there who might know the answer.
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  #2  
Old 15th July 2006, 11:28 PM
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pre65 pre65 is offline
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Default Re: Turntable Signal to Noise Ratio

Hi-whilst looking on the net for clues to answer this question i came upon this interesting article on how the sound on valuable old recordings can be preserved
for future generations.

http://www.jts2004.org/english/proceedings/Stotzer.htm

it is not something i had heard about before.

Is it possible their is a British or DIN standard for this signal/noise ratio ?

Philip
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  #3  
Old 16th July 2006, 09:26 AM
Primalsea Primalsea is offline
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Default Re: Turntable Signal to Noise Ratio

Phillip,

Thanks for having a look around, very kind of you. Although I wasn't expecting anyone to do any research for me, I was just hoping that someone might know.

The article you linked to is quite interesting. Have you seen the record player that uses laser heads to read records? I think one was reviewed in Hifi Choice at some point. Looks like it does almost the same thing (same end anyway) but is in a more compact package (fits on a hifi rack).

Where abouts are you, I live on the Essex / Suffolk boarder also.
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Old 16th July 2006, 09:59 AM
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Default Re: Turntable Signal to Noise Ratio

Hi Primalsea-yes i have seen the laser player,infact they have been on e-bay in the past.

from what i remember they were not praised for their sound quality but obviously wont further damage valuable archive material.

i am at Ashen,near Clare which is on the Essex side (cos i'm an Essex boy !) and Gerry is not too far away near Ousden so perhaps we have the beginnings of a local group.

Some other forums ask new members to introduce themselves briefly so members can "get to know" newcommers.

we have the "user CP" section on the forum but most seem unwilling to use it,although (as in this case) the "Location" would seem a good thing for getting help from local members.

Philip
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  #5  
Old 16th July 2006, 10:16 PM
Primalsea Primalsea is offline
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Default Re: Turntable Signal to Noise Ratio

I know Clare quite well, we go to the park alot in the summer as the kids like to feed the ducks. I live in Haverhill, or "Dodge City" as it is refered to buy some Cambridge dwellers.

A local group might be a good idea as I personally find that you can learn alot more by listening to other peoples systems in relaxed surroundings.
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  #6  
Old 16th July 2006, 10:41 PM
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Default Re: Turntable Signal to Noise Ratio

Hi-Haverhills reputation seems to have improved a little in the last few years !

there is (was ?) a post on the forum somewhere where members could list their equipment so if you can find it let us all know your kit or if not post it here.

Philip
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  #7  
Old 17th July 2006, 01:04 PM
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petercom petercom is offline
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Default Re: Turntable Signal to Noise Ratio

Quote:
Originally Posted by Primalsea
How is this measured on a turntable ?
(I know how to calculate it from the measurements).

I guess you must have a test record and cartridge with known signal to noise ratios at a particular reference level. Then use them on a TT and measure the output and compare it to the test signal.

Now I know that tech specs often have no bearing on subjective sound quality. However whats confusing me is the S/N ratios being quoted by many TT manufactures. There should be a reference quoted for the test signal overwise the spec is meaningless. All S/N specs for turntables don't mention the reference signal. Is there a standard reference that I can't find or is this another example of the misleading info given out buy manufacturers.

I ask this because Clearaudio often brandish S/N ratios of 84db (with no reference) Pro-ject Audio TT's have much lower S/N ratios even for their best TT's, and again no reference. This means that it is quite possible that Pro-ject TT's could actaully have similar S/N ratios to Clear Audio TT's depending on the refernce used.

I know that many people won't find this post very interesting but I was hoping that there are some other sad people out there who might know the answer.
The reference level for LP measurements is based around a peak velocity cut of 7cm/s of a 1kHz sinewave. Various test discs have been cut with this reference level over the years.

To check signal to noise all you have to do is play the test record reference level track to set the 0dB level. Then play a record with a blank groove to measure the S/N ratio.

The problem is that even a test record with blank groove will still display a cutter noise value of -65dB. So to measure lower is difficult. As a result some testers use a blank disc instead. It is still difficult to differentiate between stylus friction noise and inherent noise when you are trying to measure to very low levels of bearing and motor noise. One way would be to filter out higher frequencies as most bearing and motor noise occurs below 500Hz. This is what matters, anyway, as it is the area most boosted by RIAA eq.

I would take most turntable manufacturer's figures below, say, 75dB as fairly meaningless in comparison with each other as you don't know exactly how they have been derived. And does it matter anyway. S/N ratio is not a measure of goodness as to whether a turntable is any good for playing music. It only gives you an indication as to whether the noise might intrude on playback, and even then it is only helpful if you are shown the frequency spectrum of such noise.
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  #8  
Old 17th July 2006, 08:19 PM
Primalsea Primalsea is offline
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Default Re: Turntable Signal to Noise Ratio

Peter,

Thank you for that info. As I kind of suspected manufacturers publish these specs which are pretty much meaningless. However at least I have some idea how to test my own TT for S/N after I have modified it. This should be a good if not general indicator if things are making a difference and how the S/N corrolates to perceived improvements.

I had a look for the post with peoples systems on but could not find it so i will post give a description of my system here and copy later if I find the post.

Pro-Ject Debut (Red) with Speedbox, 20mm Glass Plater, Felt Mat, Metal shielding over motor and power cables, Spiked Feet.
RB250 which has had the fingerlift removed, holes drilled in the underside of the tube and has had all paint removed. Stainless steel weight & end sub. The cross piece of the armtube has had the bearings removed and a teflon rod inserted in their place. The ends of the rod have been drilled out and mate with 2 glass beads which are held in place by the brass inserts that used to mate to the bearings.

Homemade adjustable isolation plinth

Home made SS Phono Amp.

Marantz CD94 with OS disabled

Passive preamp / Input extender which actually works very well and is my favourite preamp so far. I also have a homemade hybrid preamp which I swap out now & again.

Homemade 4 channel power amp in a large rackmount case. I uses 2 450VA transformers and some amp kit I bought from Maplins. I was so pleased with it I now use it all the time despite trying all sorts of other SS and tube amps.

I also have various other homemade amps scattered about.

Mission 773e speakers. I'm also making a pair of large 3 way active speakers which are nearly finished. These are beasts being nearly a meter tall and too heavy for me to carry on my own.

As you may have guessed I got into Hifi through the DIY route. I have some other projects on the go like a leak Stereo 20 restoration, DAC, CD Player and possibly some other things that I have forgotten about until I find them.

Last album bought: David Sylvian - Gone to Earth
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  #9  
Old 18th July 2006, 07:49 AM
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petercom petercom is offline
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Default Re: Turntable Signal to Noise Ratio

Aah, Mission 773e, that was my first design exercise when I started as Acoustic Director at Mission. Fond memories.
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  #10  
Old 18th July 2006, 09:57 AM
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pre65 pre65 is offline
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Default Re: Turntable Signal to Noise Ratio

Hi-re the maplin bits in your 4 channel amp.

i so very nearly bought a couple of the 50w mosfet modules years ago, to make a stereo amp (cos they said the sound was valvelike).

i had lifesize cutouts of all the bits to sort out an enclosure but never got round to it.the 832 project i'm on now is the first amp i've actually started.

did anyone here ever use these mosfet modules,and if so what was the result ?


Philip
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