Go Back   Home > Forums > Member Areas > The Lounge

The Lounge A place to talk about almost anything but politics and religion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 25th February 2011, 12:40 AM   #10141
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by martin clark View Post
BBC RD 1970/13: Acoustic scaling: General outline. H.D. Harwood, A.N. Burd

The reason to enclose the model would be to ensure a very low %RH can be maintained locally to avoid excess in-air losses at the very high frequencies used - the Beeb used a zeolite trap in the setup. I can't see that high pressures per se help in any way.
This is a great reference, very clear and fits within a good intuitive feeling for the problems.
__________________
“The earth's rotation will slow within days and stop for several days just prior to the pole shift. This is when you and your loved ones should be situated at your safe location.”
  Reply With Quote
Old 25th February 2011, 02:54 AM   #10142
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
One good reference on the Lincoln Center acoustical problem is: 'Fractals,Chaos, Power Laws' by Manfred Schroeder, 1990 pp. 74-79. The author was apparently one of the people delegated to find the problems, and he did.
  Reply With Quote
Old 25th February 2011, 01:02 PM   #10143
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Phono cartridges anyone?
  Reply With Quote
Old 25th February 2011, 01:34 PM   #10144
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
If you're giving 'em away, I'll be happy to take one!
__________________
"The way to deal with superstition is not to be polite to it, but to tackle it with all arms, and so rout it, cripple it, and make it forever infamous and ridiculous."- H. L. Mencken
  Reply With Quote
Old 25th February 2011, 02:10 PM   #10145
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
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.
  Reply With Quote
Old 25th February 2011, 02:23 PM   #10146
hhoyt is online now hhoyt  United States
diyAudio Member
 
hhoyt's Avatar
 
Join Date: Mar 2010
Location: Chapel Hill, NC
Default Phono Noise

Quote:
Originally Posted by john curl View Post
Phono cartridges anyone?
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
  Reply With Quote
Old 25th February 2011, 02:51 PM   #10147
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by hhoyt View Post
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.

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).
__________________
“The earth's rotation will slow within days and stop for several days just prior to the pole shift. This is when you and your loved ones should be situated at your safe location.”
  Reply With Quote
Old 25th February 2011, 03:11 PM   #10148
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Cartridge noise (and its relation to input stage design) is well described in Mr. Vogel's book.
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 25th February 2011, 03:14 PM   #10149
hhoyt is online now hhoyt  United States
diyAudio Member
 
hhoyt's Avatar
 
Join Date: Mar 2010
Location: Chapel Hill, NC
Default Phono Noise

Quote:
Originally Posted by PMA View Post
Cartridge noise (and its relation to input stage design) is well described in Mr. Vogel's book.
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
  Reply With Quote
Old 25th February 2011, 03:22 PM   #10150
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Hi Howard,

let me send you a friendly e-mail ...

Best,
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 02:13 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2