Flyfish, The others have subverted your post into a discussion of loading. Bear in mind that this is a "loaded" question; there are "front-loaders" (those who urge you to add a resistor to the primary side) and back-loaders (the more common method of loading the cartridge only on the secondary side) in two opposing camps. On this question, I can only add that Tim de Paravicini might know a little bit more about cartridge loading than some of the others here who are telling you that loading the secondary is "wrong". But what I am interested in is whether you got rid of the noise by switching from your MC input stage to using the SUT. I am not clear on what happened to the noise when you made the switch.
Need to be educated re: MC Step-up transformers
I recently purchased the EAR MC-4 Step-up transformer. I was having some noise problems with my analog rig. I spoke with Tim de Paravicini of EAR directly in the UK. He answered all the system matching questions and pronounced the MC-4 a fit with my system. He is very direct, extraordinarily knowledgeable, and seemed very sincere and honest.
I still don't understand the "How" though. Here's what I do understand and relayed to Tim:
1. I use the ClearAudio Stradivari, a MC at 0.7mV output.
2. Currently, my phono stage provides a total of 57 dB of gain: 20 in the MC mode using a JFET and 37 in the MM mode using all tubes. My tube line stage provides 12 dB of gain SE, which is how I run it. So, currently without the MC-4, I have a total of 69 dB gain when running my phono stage in MC mode (20 + 37 + 12).
3. The MC-4 has four taps – I was told by Tim to use the 40 ohm tap which provides a 10x gain in voltage and is compatible with the 32 ohm impedance of my cartridge. This would change the output voltage my phono stage “sees” from 0.7mV to 7.0mV.
4. The phono stage must be run in MM mode, bypassing the JFET in the MC mode.
5. Given all this, then, my phono stage will receive as input a 7.0mV cartridge output from the MC-4. This signal will run through the MM mode and receive 37 dB gain and then another 12 dB gain from the line stage SE for a total of 49 dB gain, down from 69 dB, as we are no longer “gaining” the additional 20 dB from the JFET MC mode.
6. I need to remove the 600 ohm Vishay resistors and get the phono stage back to the stock 47 kohm setting, as the MC-4 will reduce the resistance by the square of the voltage gain or 10^2 or 100: 47,000/100 = 470. That is within the range recommended by Clearaudio of 320 – 900, preferably toward the lower end, though let your ears be your guide.
It was based on this information (which I provided) that the MC-4 was pronounced a fit - I certainly don't doubt that.
Here's my confusion: Am I to understand that 7.0mV of cartridge output from the MC-4 is so much more voltage that all I need is the 49 dB the system provides in its new configuration for low noise and analog bliss?
I just don’t understand the science, I guess. I appreciate the education.
Brent
I still don't understand the "How" though. Here's what I do understand and relayed to Tim:
1. I use the ClearAudio Stradivari, a MC at 0.7mV output.
2. Currently, my phono stage provides a total of 57 dB of gain: 20 in the MC mode using a JFET and 37 in the MM mode using all tubes. My tube line stage provides 12 dB of gain SE, which is how I run it. So, currently without the MC-4, I have a total of 69 dB gain when running my phono stage in MC mode (20 + 37 + 12).
3. The MC-4 has four taps – I was told by Tim to use the 40 ohm tap which provides a 10x gain in voltage and is compatible with the 32 ohm impedance of my cartridge. This would change the output voltage my phono stage “sees” from 0.7mV to 7.0mV.
4. The phono stage must be run in MM mode, bypassing the JFET in the MC mode.
5. Given all this, then, my phono stage will receive as input a 7.0mV cartridge output from the MC-4. This signal will run through the MM mode and receive 37 dB gain and then another 12 dB gain from the line stage SE for a total of 49 dB gain, down from 69 dB, as we are no longer “gaining” the additional 20 dB from the JFET MC mode.
6. I need to remove the 600 ohm Vishay resistors and get the phono stage back to the stock 47 kohm setting, as the MC-4 will reduce the resistance by the square of the voltage gain or 10^2 or 100: 47,000/100 = 470. That is within the range recommended by Clearaudio of 320 – 900, preferably toward the lower end, though let your ears be your guide.
It was based on this information (which I provided) that the MC-4 was pronounced a fit - I certainly don't doubt that.
Here's my confusion: Am I to understand that 7.0mV of cartridge output from the MC-4 is so much more voltage that all I need is the 49 dB the system provides in its new configuration for low noise and analog bliss?
I just don’t understand the science, I guess. I appreciate the education.
Brent
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- 24 posts total
Brent -- Regarding using a 47K load, iirc correctly even the estimable Harry Pearson (founder of "The Absolute Sound") wrote many years ago of preferring the sound of some particular mc cartridge when loaded (or perhaps I should say "unloaded") with 47K! But as Axel indicates, that would be optimal only for a small minority of mc's. Basically, what the typical lower value load does is to dampen what would otherwise be a large high frequency (usually ultrasonic) resonant peak. You can find an explanation of that here: http://www.hagtech.com/loading.html The degree to which that peak would produce adverse audible consequences, such as brittleness or edginess, would depend on its amplitude, its frequency, the bandwidth of the rest of the system, and the intermodulation and other effects that may be produced in the rest of the system by ultrasonic or very high frequency spectral components, as well as on the mechanical damping provided in the cartridge itself, as Axel points out. Axel & Saudio -- Thank you for your comments. I don't question your experienced-based comments, and I think we all agree that mc cartridge matching necessitates that listening be the final arbiter even more so than with the rest of an audio system. I haven't seen any good explanations of why use of a step-up transformer would typically call for heavier loading than would be the case if a high gain phono stage or head amp were used. After giving it some thought, I've developed the following theory: A real-world transformer can be modeled as an ideal transformer in parallel with an inductor on the primary side, representing "magnetizing inductance," as well as other resistive and inductive elements representing loss mechanisms. See the diagram around the middle of this page: http://en.wikipedia.org/wiki/Transformer Referring to that diagram, if we assume that the series leakage inductance Xp is relatively insignificant compared to the cartridge's inductance, then by Thevenin's Theorem the magnetizing inductance Xm can be considered as combining in parallel with the cartridge inductance. That will result in a lower total inductance, and therefore an ultrasonic resonant peak which is higher in amplitude if a heavier load is not applied to damp it. Although the peak will be higher in frequency as well, and it will also be affected by the bandwidth limitations of the transformer, all of which sufficiently muddles the situation such that, again, listening would seem to be the only way reach any meaningful conclusions. Regards, -- Al |
Thanks again for the posts. In my second posting, I was discussing loading my phono stage, or what I have just learned is referred to as "back loading". I never even knew one could "front load". I apologize to Axelwahl for any confusiuon. In my phone conversations with Tim, he felt I could use the MC-4 "as is", just remove the two 600 ohm resistors I use to "back-load" and I should be good to go. Did I remove the noise - can't answer that, yet. Neither the US importer nor EAR carry any inventory on the MC-4. Each is made as an order is placed. From e-mails, I understand my MC-4 just made it out of testing in the UK and should be shipped to the US either Monday or Tuesday of next week. I will post again with results. Again, this is wonderful info for me. Brent |
Flyfish, I am going to stay clear of all the technical discussion here. As valuable as it can be, the bottom line is how it all sounds to you. I have been running with a Clearaudio Accurate for several years now. With this previously straight into an Aesthetix Io phono stage, I ultimately found the "best" load to be between the 500 and 1kohm jumpers. When I changed to the Aria WV preamp with Sowter SUTs, the 200, 300 and 500 ohm jumpers were so close that any of these would have been fine. Running without any of these defaults the input to 1k and this was just a touch too "hot". And now with the cartridge running into a rebuilt Counterpoint SA-2, I have found that a 500 ohm resistor in the load terminals is a great balance. So your drop way down to 700 ohms is close to my own experience here. John |
- 24 posts total