I forgot about that, did I send you the excess noise schematic? I think I still have the schematic from the adaptor board. Probably useful to all of 10 people in the world.
I use 300 Ohm and will try 138 Ohm on the High Z MPP. 1kOhm was still too treble heavy in my system.
John, a wirewound pot should work well for cartridge loading. It has vitually no excess noise.
RS Components make a presision one. I could try to find it.
John, a wirewound pot should work well for cartridge loading. It has vitually no excess noise.
RS Components make a presision one. I could try to find it.
If you PM me you shipping info I should be able to send you some 300 and 138 ohm samples of the more cost effective resistors that measure well.
If any one wants to they have my permission to re-post the attachment to this thread in a PDF format. ES
That one works quite well.
http://docs-europe.origin.electrocomponents.com/webdocs/05e0/0900766b805e0fa8.pdf
http://docs-europe.origin.electrocomponents.com/webdocs/05e0/0900766b805e0fa8.pdf
Being one of those 10 people please forward it. Not that I need it for resistors, I have the resistor analyzer and the Semi analyzer's noise floor is too high for low value resistors. But it may be useful for testing Zeners and voltage references.
-Demian
Excess noise-
is the noise generated by passing DC at some level of power dissipation through a resistor. I don't see how it can be an issue with a phono input. Most cartridges woould be a smoking ruin before there was enough DC to generate noise in the loading resistor.
is the noise generated by passing DC at some level of power dissipation through a resistor. I don't see how it can be an issue with a phono input. Most cartridges woould be a smoking ruin before there was enough DC to generate noise in the loading resistor.
I am 1 of those 10, Scott, and it is people like you giving info to people like me, that made me famous, because I took it seriously, and used the results.
Joachim, please get up to speed, we know this more than 40 years ago. There is more to it than just that, if you think about it.
What do you think about that? It is 4 potmeters. 2 are wound one way around, two are wound the other way around and they are turned clockwise and anticlockwise. The switch allows switching between 47kOhm and 500 Ohm aerea. That way you avoid end stop resistance problems.
Thanks
BTY I have an article on PC layout that just came out in the digital version only @
http://www.audioamateurinc.com/digital/ax/issue/410/
Free views for now.
(Although I think they may have mislabeled a figure or 2! Need to check.)
Interesting article on layout. I have used expresspcb for years, just to be quick and cheap. One thing you didn't touch on is inductive coupling between star ground returns. if traces are close enough and carrying currents they will couple. That may cause some unanticipated effects, especially when handling high currents at high di/dt.
I might do a quick historical review of why we concern ourselves about resistors and specifically EXCESS NOISE.
In the old days, like Marantz, Ampex, and original McIntosh, through the 1960's, carbon resistors were used in almost every audio circuit, even feedback resistors.
In those days, precision 1% metal film resistors cost about $1/ea. For your own computation, multiply your European currency by 4.
In the USA, that was the cost of lunch for one day. Therefore every precision resistor cost us 1 lunch/resistor. This is why we kept them to a minimum, if we used them at all. Did we know about EXCESS NOISE in those days? You bet! We generally found that some brands of carbon resistors were better than others in this way, and we used them.
The first time I ever saw 1% metal film resistors used throughout in a circuit design, was with Mark Levinson's LMP-2 preamplifier. Mark told me that Dick Burwin suggested it. It was relatively expensive, but Mark worked at it to keep it affordable.
Today, everybody has access to 1% metal film resistors, as they are so cheap. However, some metal film resistors are better made than other metal film resistors, and this remains the problem between resistor choices.
Excess noise, itself is measured by putting DC across a resistor and measuring its noise with the DC voltage across it. IF it gets noisier than its noise value, then the extra noise is called EXCESS NOISE. Many metal film resistors have very little EXCESS NOISE, others have more EXCESS NOISE than others. We have test equipment that can measure it, if necessary.
In the old days, like Marantz, Ampex, and original McIntosh, through the 1960's, carbon resistors were used in almost every audio circuit, even feedback resistors.
In those days, precision 1% metal film resistors cost about $1/ea. For your own computation, multiply your European currency by 4.
In the USA, that was the cost of lunch for one day. Therefore every precision resistor cost us 1 lunch/resistor. This is why we kept them to a minimum, if we used them at all. Did we know about EXCESS NOISE in those days? You bet! We generally found that some brands of carbon resistors were better than others in this way, and we used them.
The first time I ever saw 1% metal film resistors used throughout in a circuit design, was with Mark Levinson's LMP-2 preamplifier. Mark told me that Dick Burwin suggested it. It was relatively expensive, but Mark worked at it to keep it affordable.
Today, everybody has access to 1% metal film resistors, as they are so cheap. However, some metal film resistors are better made than other metal film resistors, and this remains the problem between resistor choices.
Excess noise, itself is measured by putting DC across a resistor and measuring its noise with the DC voltage across it. IF it gets noisier than its noise value, then the extra noise is called EXCESS NOISE. Many metal film resistors have very little EXCESS NOISE, others have more EXCESS NOISE than others. We have test equipment that can measure it, if necessary.
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