Very straightforward, after Joachim triggered the idea.
The conclusion is: Signal/noise = output/(Johnson noise from series R)
so you want the most output with the least resistance. Inductance probaby too small to make a difference, but I have not checked that. Bear in mind that this simple calculation is for a flat frequency response, and does not take into account RIAA equalisation. Applying that would alter the numbers, but not the quietness ranking of the various cartridges.
Applying the same notion to moving-magnet cartridges is trickier because the high inductance means that not all the Johnson noise from the series resistance reaches the preamp input, due to the 47K load resistance. I also don't have a large database of MM cartridge characteristics.
However, here are a few back-of-envelope calculations for maximal S/N ratio. The RIAA is taken into account, so is the Johnson noise from the 47K load resistance, but the amplifier is presumed to be noiseless:
Shure ME75ED 2 (R=640 Ohm, L=470mH) S/N= -81.8 dB
Goldring Eroica H (R=77 Ohm, L=200mH) S/N= -82.8 dB
Interesting because the very different cartridge parameters seem to indicate different design philososphies but the maximal S/N is much the same.
The conclusion is: Signal/noise = output/(Johnson noise from series R)
so you want the most output with the least resistance. Inductance probaby too small to make a difference, but I have not checked that. Bear in mind that this simple calculation is for a flat frequency response, and does not take into account RIAA equalisation. Applying that would alter the numbers, but not the quietness ranking of the various cartridges.
Applying the same notion to moving-magnet cartridges is trickier because the high inductance means that not all the Johnson noise from the series resistance reaches the preamp input, due to the 47K load resistance. I also don't have a large database of MM cartridge characteristics.
However, here are a few back-of-envelope calculations for maximal S/N ratio. The RIAA is taken into account, so is the Johnson noise from the 47K load resistance, but the amplifier is presumed to be noiseless:
Shure ME75ED 2 (R=640 Ohm, L=470mH) S/N= -81.8 dB
Goldring Eroica H (R=77 Ohm, L=200mH) S/N= -82.8 dB
Interesting because the very different cartridge parameters seem to indicate different design philososphies but the maximal S/N is much the same.
Hello Douglas !
I tryed the Low Z input with the Lyra Titan i ( 5.5 Ohm impedance ) and it worked well aurally but i did not do a measurement. Somewhere hidden in the text is the information that for the Low Z case the feedback resistors appear in PARALLEL to the cartridge so the value of the feedback resistors can be raised without worsening the SN much when the cart is a low Z type. Raising the resistor values whould also lessen the burden on the current delivering Opamps. I build a lot of transimpedance stage with theoretical zro input impedance and also in this cases i could not percept a treble loss with my asortment of Low Z carts.
I found another cartridge that is a contender for high SN. It is the Air Tight P1 with 2.5Ohm and 0.5mV. There is a Signature model above that has even a higher ratio of impedance to output voltgae but i did not find te data sheet so far.
I tryed the Low Z input with the Lyra Titan i ( 5.5 Ohm impedance ) and it worked well aurally but i did not do a measurement. Somewhere hidden in the text is the information that for the Low Z case the feedback resistors appear in PARALLEL to the cartridge so the value of the feedback resistors can be raised without worsening the SN much when the cart is a low Z type. Raising the resistor values whould also lessen the burden on the current delivering Opamps. I build a lot of transimpedance stage with theoretical zro input impedance and also in this cases i could not percept a treble loss with my asortment of Low Z carts.
I found another cartridge that is a contender for high SN. It is the Air Tight P1 with 2.5Ohm and 0.5mV. There is a Signature model above that has even a higher ratio of impedance to output voltgae but i did not find te data sheet so far.
Attachments
Yes, this price is insane. I was able to hear the Air Tight Supreme on the weekend with one of my phonostages and it sounded nice. Noise was nearly non existing. There are some less expensive contenders in the new Lyra range and i will post the specs later.
Like it or not, there is a suprisingly robust market for expensive cartridges and i know a lot of people that own them and are perfectly happy with their choice.
Like it or not, there is a suprisingly robust market for expensive cartridges and i know a lot of people that own them and are perfectly happy with their choice.
Hi Jack,
Yes a good suggestion, I'll think about it.
One of my focal points for the next issue is the look and placing of illustrations. Surprisingly (or maybe not) the illustrations in an article take much more effort than the text. Then again, a pic is worth a 1000 words they say
jan didden
I think Sugano San of Koetsu stated the high price race in the 70th. His idea was to use precious stone for the body of the cart and using exotic materials for the wires and the magnetic structure. Then came the Audio Note Japan IO Limited that had a field coil instead of a magnet and special rigid and low resonance design for the body. That cartridge also had a very low impedance around 1 Ohm and a super low output of only 0.025mV. Even today the best phonstages with a SN of 80dB are not good enough for this cartridge in terms of noise so a transformer is the only way to do it justice. Today we have a plethora of exotic and expensive cartridges and new ones are comming each day. But there are also very good sounding cartridges that do not cost an arm and a leg. What i find really importand is how this cartridges are adjusted and amplified and if the tonearm has the correct effective mass, has good bearings and good damping of resonances and that the turntable has no audible rumble, holds the speed and is isolated from mechanical shock and air transmission. Recently i put together a turntable for a friend of mine and the sound i got was in some but not all ways better then the sound of my 10 times more costly refference table. It all depends how the equipment is setup and used. By mentioning this expensive cartridges it was not my intention to give the impression that only very expensive cartridges do the job. My intent was to show that for a lowest noise result impedance should be low and output voltage should be high.
Hello
I am painfully aware that my website is not currently accessible under its usual address. The Pipex address translation system seems to have failed. They don't seem to be interested in fixing it.
You can still access it at: The Douglas Self Site
(http://www.aqpl43.dsl.pipex.com/index.htm)
Please pass this info on to anyone you think might be interested.
Hi Joachim
I don't think I follow you about the feedback resistors appearing in parallel to the cartridge. So far as I can see their noise contribution still counts. Can you do us a diagram?
I was more concerned about the implications for the cartridge response of running it into a virtual short-circuit, as opposed to the manufacturer's minimum load. Surely there must be bad effects?
The Air Tight P1 shows a (non-RIAA) S/N of 84.8 dB, not so good as the Hyper Eminent at 86.3 dB. But the Air Tight Supreme gives 86.9 dB, so we have a new winner. Mind you, for that money it should be good.
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Hi Douglas !
I am busy with family issues at the moment but i will answer later today.
Concerning the expense of such high tech cartridges i hope that the technology trickles down into more affordable regions ones in a while. I asked the guys at Lyra why this cartridges have such a good relationship between impedance and voltage output and the answer was that My Sonic Lab and Air Tight use a special core material where they wind the coils on that is a trade secret.
I am busy with family issues at the moment but i will answer later today.
Concerning the expense of such high tech cartridges i hope that the technology trickles down into more affordable regions ones in a while. I asked the guys at Lyra why this cartridges have such a good relationship between impedance and voltage output and the answer was that My Sonic Lab and Air Tight use a special core material where they wind the coils on that is a trade secret.
Douglas, if you want any help with your own domain and a good webhotel, I can help you. This will take me 15 minutes maybe and transfer all you info won't be hard either. Let me know if you are interested. I administrate six websites so I'm used to deal with this. One of my webhotels is ManuFrog Webbhotell very good with servers in UK and the US.
Here come two simplified gain structures that are posible with the Rabbit Hole Phonostage. One is High Z and the other Low Z. I will do a noise analysys with both circuits with my assosiates the next days. I simmed my referrence cartridge with 6 Ohm and 6uH. I measured this values at the connectors that go into the phonostage so they include the cabling. With the Lyra Titan I and a feedback resistor of 10 Ohms the sound i got was fine but i did not do any measurements of frequency response. That will be done too as soon as i have the finished product in house. As far as i can see it the impedance of the cartridge is parallel to the feedback resistor AC wise in the Low Z case.
Vlads travel fund
At the Burning Amp tread AR2 collects travel money for a couple of DIYA-members to enable them to visit Burning Amp.
Linear Audio will contribute to this fund: I'll donate $ 1 for each sale to a DIYaudio member; you need to enter discount code DIYA when ordering.
And ohh yes, you'll get 10% off as well yourself.
Deal?
jan didden
At the Burning Amp tread AR2 collects travel money for a couple of DIYA-members to enable them to visit Burning Amp.
Linear Audio will contribute to this fund: I'll donate $ 1 for each sale to a DIYaudio member; you need to enter discount code DIYA when ordering.
And ohh yes, you'll get 10% off as well yourself.
Deal?
jan didden
Hi there
Sorry for delay in replying, but yes, I am interested. The site is currently unavailable even under its alternate name and I'm sick of being messed about by Pipex.
I have registered by own domain- douglas-self.com
Where do we go from here?