Wavebourn, Volt, you are saying tubes and transformers have better RF immunity? Could you explain, elaborate? Just want to learn more.
H,
I would look at shielding and a cellphone extender. Gives you a bit more control.
Yes I have had folks in arenas put their antennas next my gear. I suspect you can do better! 🙂
I would look at shielding and a cellphone extender. Gives you a bit more control.
Yes I have had folks in arenas put their antennas next my gear. I suspect you can do better! 🙂
Hi Ed, I had already suggested this in addition to the shielding, we'll see what they say. I'm just aghast that anyone would even have a phone on in a control room, if just for the mental interruption potential...but that is apparently just me.
I hadn't measured the actual field strength of a cell phone itself at that location, it should be at minimum transmit power considering how close the tower is. Still, it was news to those people that a cell phone can induce interference into nearby equipment, I guess the inverse square law is a foreign concept...
Cheers,
Howie
Yes. Audio transformers are filters actually, thanks to their parasitic capacitances and inductances. Stray inductance and capacitance between windings and grounded interwinding shield forms kind of a filter. Additional RF chokes from input sockets with capacitors to the ground add one more, symmetric.
Input transistors need much lover signal level to rectify RF than tubes. Plus, feedback loops in high open loop gain solid state amplifiers do not work on RF, that magnifies the problem.
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For inside use... try the old land line phone system. Can talk-listen without RFI issues. get one (or more than one phone) with memory and record messages etc. Others can forward their mobile number to the land line number temporarily as needed.
-RNM
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I too read those reviews, but given their age I am pretty sure they were not referring to the latest JICO series with either sapphire or ruby cantilevers. I do not have the specs nor test results with the latest JICO sapphire or ruby SAS, but it would be interesting!
The original stylus was indeed fantastic, quite an achievement! I wish they were still available...I am always leery of eBay "lightly used" styli.
Cheers,
Howie
Thanks for the explanation, it´s a good starting point. The passive filtering of RF is easy to grasp. The semiconductor effects I need to look deeper into (review the physics). Tubes I know very little about. You are at a huge advantage to understand all of this.
Rectification of RF. Is this what happens when I place a cellphone next to say, a standard gainclone, and I can clearly hear audio ("squarish") tones? My latest attempt at a chip-amp doesn´t do this at all, it is dead silent, no noise from phones, fridge, nothing. Without input filtering. Sounds much better than standard chip-amps.
Rectification of RF. Is this what happens when I place a cellphone next to say, a standard gainclone, and I can clearly hear audio ("squarish") tones? My latest attempt at a chip-amp doesn´t do this at all, it is dead silent, no noise from phones, fridge, nothing. Without input filtering. Sounds much better than standard chip-amps.
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Alexandre;
You can compare volt-ampere characteristics of a p-n junction forward biased, and a reverse - biased vacuum diode (grid to cathode).
You can compare volt-ampere characteristics of a p-n junction forward biased, and a reverse - biased vacuum diode (grid to cathode).
It is very similar to the Twisted Pear Sympatico. A composite amp with THS4131 at the front. But I used two LM3875, in inverting mode, while the Sympatico used two LM3886 in non-inverting.
Inverting mode means the input signal goes through a resistor that being loaded on parasitic capacitances attenuates RF signal.
It is clearly better than my previous attempts (non-inverting). And I didn´t use non-inverting buffers in front of the THS4131: I just used a floating source going directly into the series input resistors. The source doesn´t have opamps or feedback. It´s dacs and common-gate I/V.
Did I say anything smart about loading of tiny current powered LT1358 on complex impedance of LCR networks? 😀
I could, actually 😉
Bold mine: my point is when you take an inverting config and ground the independent source you end up with exactly the same circuit. The noninv input is already grounded and the source would normally feed into the Rf resistor to the inv pin, that source is now grounded and you get the same circuit with the Rf normally grounded, the source feeding into the noninv input which now gets also grounded. So in the case you break the loop between output and the input to the feedback circuit, both configs become identical.
Jan
So ask now then. What do you want to know that you couldn't answer yourself?
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I want to know, when and how I stepped on your tail, why are you jumping on me?
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