This is a great reference, very clear and fits within a good intuitive feeling for the problems.
At this time, I don't have much to say here about the various contributions from different parties. However, MY stand on audio design, that works for me, is to do what I CAN, and live with what I can't. From my world view, I CAN make better electronics that is easier on the ear, achieve TRUE channel separation to eliminate false generation of image placement, and remove clipping or having my amplifiers sounding stressed,'homogenized', or distorted, for the most part. I can also design enough peak current into my designs that they can drive even 'difficult to drive' speakers at least under normal listening conditions, where some current compromised designs might fail.
This MAY sound easy, but it is not, and most audio designs fail in doing what I just stated in some major way. That is what keeps me in business.
Some here want MORE or different. They want TRUE image and reverberation coming from any concert hall in the world coming from their audio reproducer. I cannot do that, as it is NOT what I do in audio design. However, others, over many decades, have done so, and they 'could' be copied, in principle.
For example, Manfred Schroeder, in the above named book, shows how HE did it, to COMPARE different concert halls throughout the world and be able to reproduce and compare them on demand. He uses artificial ear recording. However, is this practical? Not really. Others, have studied hall characteristics and have attempted to simulate them with black boxes full of op amps, where you can change the listening characteristics with the flip of a switch or the push of a button. If THIS turns you on, go for it. I personally find the congestive sound of multiple op amps and other marginal components fatiguing, but I must agree that they can be effective for what they attempt to do. For me to make something that I could really live with, would cost a fortune, and nobody has offered me one yet, to attempt something like this.
So I stick to my mostly 2 channel reproduction, even mono, much of the time, because what I mostly want is there with good playback equipment.
Now, if someone else wants something different, and is willing to forgo really high fidelity that seems to come almost exclusively from tubes and discrete designs, good luck to them. The same as if someone insisted on driving a pickup truck or a Limo to achieve their needs. If I drive a 2 seat sports car, that is MY business and pleasure, and it doesn't need to be parsed or criticized by the limo driver.
The solution is to live, and let live. To each his own, yet let us learn from the other, perhaps in a polite discourse, what each of us may be missing by NOT concentrating on a particular solution.
The CTC BLOWTORCH, the preamp that is the title of this thread is CLUNKY, MASSIVE, HARD TO CHANGE, with either volume or selection, or polarity, EXPENSIVE, yet it does what it is SUPPOSED to do. Play music as effortlessly and as accurately as possible.
And so it goes.
This MAY sound easy, but it is not, and most audio designs fail in doing what I just stated in some major way. That is what keeps me in business.
Some here want MORE or different. They want TRUE image and reverberation coming from any concert hall in the world coming from their audio reproducer. I cannot do that, as it is NOT what I do in audio design. However, others, over many decades, have done so, and they 'could' be copied, in principle.
For example, Manfred Schroeder, in the above named book, shows how HE did it, to COMPARE different concert halls throughout the world and be able to reproduce and compare them on demand. He uses artificial ear recording. However, is this practical? Not really. Others, have studied hall characteristics and have attempted to simulate them with black boxes full of op amps, where you can change the listening characteristics with the flip of a switch or the push of a button. If THIS turns you on, go for it. I personally find the congestive sound of multiple op amps and other marginal components fatiguing, but I must agree that they can be effective for what they attempt to do. For me to make something that I could really live with, would cost a fortune, and nobody has offered me one yet, to attempt something like this.
So I stick to my mostly 2 channel reproduction, even mono, much of the time, because what I mostly want is there with good playback equipment.
Now, if someone else wants something different, and is willing to forgo really high fidelity that seems to come almost exclusively from tubes and discrete designs, good luck to them. The same as if someone insisted on driving a pickup truck or a Limo to achieve their needs. If I drive a 2 seat sports car, that is MY business and pleasure, and it doesn't need to be parsed or criticized by the limo driver.
The solution is to live, and let live. To each his own, yet let us learn from the other, perhaps in a polite discourse, what each of us may be missing by NOT concentrating on a particular solution.
The CTC BLOWTORCH, the preamp that is the title of this thread is CLUNKY, MASSIVE, HARD TO CHANGE, with either volume or selection, or polarity, EXPENSIVE, yet it does what it is SUPPOSED to do. Play music as effortlessly and as accurately as possible.
And so it goes.
Phono Noise
John, since you have as much or more experience as anyone designing MC preamps and MM RIAA eq amps, can you give me your opinion on the following observation?
One of the apparent advantages to an MC would be the low DC resistance and corresponding lower Johnson noise, which is of course offset by the added noise from the required preamp. The L of the MM source in conjunction with the load C provides a peak at some HF which shapes the (higher) Johnson noise of the MM cart, and gives it a more HF premphasized "hissy" noise, as opposed to the MC's more Gaussian "shhh."
Probably all of us here have measured phono preamp output noise specs and summarized them with a S/N number, but I have not done that with the cartridge itself. However, as you have heard me complain about here in the past, I really hate it when a complex phenomenon is rolled into a single number. What would be more informative would be a comparison between the two different cartridge types noise spectra, something I have not measured. An engineer with better handle on the math than I could take measurements of the preamp gain and input-referred noise spectrum, and subtract the result from the output to get at the inherent cartridge noise spectrum, but it is a bit beyond me.
This is my question (finally): Can you give a quick comparison of the noise spectrum as you have measured it associated with the cartridges themself (along with their termination)? And maybe share your opinion comparing the nature of the difference between MC and MM noise?
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill
www.wxyc.org
1st on the Internet
John, since you have as much or more experience as anyone designing MC preamps and MM RIAA eq amps, can you give me your opinion on the following observation?
One of the apparent advantages to an MC would be the low DC resistance and corresponding lower Johnson noise, which is of course offset by the added noise from the required preamp. The L of the MM source in conjunction with the load C provides a peak at some HF which shapes the (higher) Johnson noise of the MM cart, and gives it a more HF premphasized "hissy" noise, as opposed to the MC's more Gaussian "shhh."
Probably all of us here have measured phono preamp output noise specs and summarized them with a S/N number, but I have not done that with the cartridge itself. However, as you have heard me complain about here in the past, I really hate it when a complex phenomenon is rolled into a single number. What would be more informative would be a comparison between the two different cartridge types noise spectra, something I have not measured. An engineer with better handle on the math than I could take measurements of the preamp gain and input-referred noise spectrum, and subtract the result from the output to get at the inherent cartridge noise spectrum, but it is a bit beyond me.
This is my question (finally): Can you give a quick comparison of the noise spectrum as you have measured it associated with the cartridges themself (along with their termination)? And maybe share your opinion comparing the nature of the difference between MC and MM noise?
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill
www.wxyc.org
1st on the Internet
I have and I think I posted a spectrum of a MM with a FET vs bipolar, quite a dramatic effect of current noise and the impedance bump at HF. National still has on line an app note from 1977, it would be a nice exercise to turn it into an Excell spread sheet (it's almost presented that way anyway).
Phono Noise
So Pavel, you would recommend Vogel's book? I'll look into it, I have seen it referenced elsewhere as well...so many books, so little free time!
(Yikes! The Sound of Silence: Lowest-Noise RIAA Phono-Amps: Designer's Guide by Burkhard Vogel - $115 on Amazon!)
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill
www.wxyc.org
1st on the Internet
So Pavel, you would recommend Vogel's book? I'll look into it, I have seen it referenced elsewhere as well...so many books, so little free time!
(Yikes! The Sound of Silence: Lowest-Noise RIAA Phono-Amps: Designer's Guide by Burkhard Vogel - $115 on Amazon!)
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill
www.wxyc.org
1st on the Internet
Phono Noise
Thanks Scott,
I'll try to find your posting, and I am studying the NatSemi App Note 222 now. Thanks for the referral.
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill
www.wxyc.org
1st on the Internet
Thanks Scott,
I'll try to find your posting, and I am studying the NatSemi App Note 222 now. Thanks for the referral.
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill
www.wxyc.org
1st on the Internet
Howard, we studied this in detail, many decades ago, even before the latest books, etc. An important early AES paper on this was given by Dick Burwin(sp) back in the late '60's or early '70's.
First, I am surprised if you hear any hiss at all. Yes, the S/N of the vinyl record itself is limited, but the electronics should be just about perfect. IF NOT, you have a problem that is probably solvable. MC and MM have very different output levels. This makes midrange noise in MC cartridges very dependent on the S/N of the electronics. We have discussed to 'death' high S/N phono stages here, 0.3nV/rtHz is not only possible, but has been available for almost 35 years. This does not mean that the following electronics will be perfect sounding, however.
When it comes to MM cartridges, there are other problems. In the old days, seemingly celebrated by Soundminded, the MM phono cartridges had huge output inductances, 1H being possible or even more. These have been reduced in modern MM cartridges to less than 0.5H. This helps a lot. Grado almost eliminates output inductance.
Still, there is a dilemma with COST EFFECTIVE phono designs. This is that low noise jfets are being discontinued in masse and they have the best overall dynamic input loading characteristics bridging between most MM and most MC cartridges.
IC's are problematic in that the transistor input units are voltage quiet, but not current quiet, and WILL compromise the S/N to some degree. Whether you can hear the difference should mostly depend on the choice of phono cartridge, and your age. A good compromise can be reached, BUT it is a compromise.
I haven't heard the upper frequency noise problem in a MM phono cartridge for the last 40 years. This may be because: They improved the phono cartridges enough to take out the upper midrange peak, or at least push it up to inaudibility, I don't listen to anything but discrete fet input phono stages, or I have just gotten too old.
I would appreciate any input from younger people as to their experience in this.
First, I am surprised if you hear any hiss at all. Yes, the S/N of the vinyl record itself is limited, but the electronics should be just about perfect. IF NOT, you have a problem that is probably solvable. MC and MM have very different output levels. This makes midrange noise in MC cartridges very dependent on the S/N of the electronics. We have discussed to 'death' high S/N phono stages here, 0.3nV/rtHz is not only possible, but has been available for almost 35 years. This does not mean that the following electronics will be perfect sounding, however.
When it comes to MM cartridges, there are other problems. In the old days, seemingly celebrated by Soundminded, the MM phono cartridges had huge output inductances, 1H being possible or even more. These have been reduced in modern MM cartridges to less than 0.5H. This helps a lot. Grado almost eliminates output inductance.
Still, there is a dilemma with COST EFFECTIVE phono designs. This is that low noise jfets are being discontinued in masse and they have the best overall dynamic input loading characteristics bridging between most MM and most MC cartridges.
IC's are problematic in that the transistor input units are voltage quiet, but not current quiet, and WILL compromise the S/N to some degree. Whether you can hear the difference should mostly depend on the choice of phono cartridge, and your age. A good compromise can be reached, BUT it is a compromise.
I haven't heard the upper frequency noise problem in a MM phono cartridge for the last 40 years. This may be because: They improved the phono cartridges enough to take out the upper midrange peak, or at least push it up to inaudibility, I don't listen to anything but discrete fet input phono stages, or I have just gotten too old.
I would appreciate any input from younger people as to their experience in this.
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They have a bunch of good stuff, but in this case I meant The Audio Handbook Appendix 5.0. I can't find a copy on line anymore but Old Colony has reprinted it. Too bad it steps through the whole problem in octave steps just like a spreadsheet. You could enter preamp and cartridge parameters and do the whole thing.
NatSemi handbook
Now that you mention it, I used to have a copy of that around here. Now I can only find the Linear Applications Handbook (1986 ed) I may have to spring for a replacement from Old Colony.
Thank you!
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill
www.wxyc.org
1st on the Internet
Now that you mention it, I used to have a copy of that around here. Now I can only find the Linear Applications Handbook (1986 ed) I may have to spring for a replacement from Old Colony.
Thank you!
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill
www.wxyc.org
1st on the Internet
I have the book and here is a scan of the appendix 5.
Page 1 and 2
@ Scott: thanks for your PM, most of the problem is solved.
Stein
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