Since the topic was initially forfeited somehow with overmodulation, we look at the corresponding time characteristics - and make it easy for ourselves (methodically and didactically reduced), feeding in a periodizing jump (rectangle) with an amplitude of 1,
1V.
HBt.
1V.
HBt.
Attachments
Why on on earth do postings have to be this unfriendly.
What´s wrong with a nice and friendly explanation.
Hans
Only now does it get exciting, namely not when we look at active filtering (i.e. nfb allInOne solution), which would have no problems with processing and would come very close to the ideal, but when we look at the Aikidos, Salas, Pass Pearls ... of this world.
Assuming our fantastic 2V bump hits the first linear single-ended class-A jFet stage and is to be amplified with +30dB, the first one pops out over all the rails.
But, our pick-up is also a great low-pass filter (correctly terminated), second order with fh=15kHz, so it will attenuate the surge and deform it properly ... We could check whether this is the case with our simulators, completely without thinking.
Assuming our fantastic 2V bump hits the first linear single-ended class-A jFet stage and is to be amplified with +30dB, the first one pops out over all the rails.
But, our pick-up is also a great low-pass filter (correctly terminated), second order with fh=15kHz, so it will attenuate the surge and deform it properly ... We could check whether this is the case with our simulators, completely without thinking.
always friendly
"Khz" is wrong
kHz is right
please do it in the right way Hans
.thx
HBt.
Here are my measurements. (Note I use a 3-stage tube phono preamplifier with passive EQ between the stages, so overloading is not an issue).
https://www.diyaudio.com/community/threads/measured-phono-signal-levels.372498/
https://www.diyaudio.com/community/threads/measured-phono-signal-levels.372498/
This is relevant here from the above cited post of mine:
... it seems the highest modulation velocity is around 30...35 cm/s @1kHz, which is 17dB above 5 cm/s. Then +20 dB is a safe margin. In my case it means 5 mV might come from the cartridge at extreme conditions, and 28Vrms might appear at the phono output. That is 80V peak-to-peak signal level!
(As I mentioned my phono gain is on the high side with 50dB; if we calculate with a more common 40dB, the output swing would be 26Vpp. A phono preamplifier made of opamps with +/-15V PSU can just handle it)
... it seems the highest modulation velocity is around 30...35 cm/s @1kHz, which is 17dB above 5 cm/s. Then +20 dB is a safe margin. In my case it means 5 mV might come from the cartridge at extreme conditions, and 28Vrms might appear at the phono output. That is 80V peak-to-peak signal level!
(As I mentioned my phono gain is on the high side with 50dB; if we calculate with a more common 40dB, the output swing would be 26Vpp. A phono preamplifier made of opamps with +/-15V PSU can just handle it)
I have marked all posts with a "like".
I am particularly pleased about the analogy in the "Bewegungsbild".
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Cool,
I keep saying it, phono equalization can only work properly with tubes and anode voltages much higher than 200Vdc.
All the junk of my childhood didn't work at all - oh, if only I had ...
😱
DUAL - everything was junk back then, it was already transistorized - BJTs
28.3Vrms
is ( a little bit) nonsense ...
Before I get beaten, I would like to point out that I like tubes too, I just don't use them anymore.
HBt.
+/- 15Vdc supply rails solve any subjective problem
then all's well - the porridge has been eaten!
Bye,
HBt.
Ok,
then all's well - the porridge has been eaten!
Bye,
HBt.
Spot on! 👍
"related to the active devices" - and the fact that one has passive RIAA ... whilst the other has active.
And the wheel keeps turning
Let us simply believe the statements and logically search for a correct answer to these observations:
It can't be that difficult!
HBt.
Let us simply believe the statements and logically search for a correct answer to these observations:
It can't be that difficult!
HBt.
A 50dB phono stage is high for MM (and will suit HOMCs) - but is not "high" for an MC phono stage.
I thought this was an Oscar Wilde, but turns out it's called Sayre's Law "In any dispute the intensity of feeling is inversely proportional to the value of the issues at stake."
All good fortune,
Chris
All good fortune,
Chris
I think the entertainment value is quite decent for some of the protagonists.
#
So let's stick with the following topology:
Gain block 1
loaded by the passive first order filter with two poles and a zero
followed by Gain block 2.
Many experts prefer this Lego brick composition. There is no question that this scenario can work perfectly - and in the majority of cases it does.
The only question that remains now is how to implement the two amplifier components. Perhaps also how to implement the equalizing low-pass filter.
In this context, one can make a multitude of mistakes.
I am happy to have a few concrete pieces of butter with the fish.
kindly,
HBt.
Hi,
I simulated a single op amp with Riaa correction in the feedback versus a three stage design, each stage having a gain of 20dB with a 75usec passive filter after the first stage and a 3180usec/318usec passive filter after the second stage.
Both versions had the same 40dB@1kHz gain and about the same noise, all amps based on the OPA1656.
Stimulating was done with a 70mV 100usec wide triangle peak such as Bob Cordell has recorded in #8.
As almost to be expected, outcoming signal from both was identical. 🤣
Hans
