Andrew, I know you understand these things. My point was that there is NO delay between the current into and the voltage across a cap, despite the phase shift. Phase shift is NOT delay.
The fact that a sine current into a cap gives a sine voltage 90 degrees shifted is not due to delay. We know that a cap voltage is the integral of the current. The integral of a sine current is a cosine voltage, which is a sine but 90 degrees shifted....
Soooo, you put a sine current into a cap and out comes a cosine voltage... which looks like a delayed sine. But looks deceive, big time!
jan didden
jan didden
Currents at the summing node are same (resistor current and capacitor current), and capacitor voltage is an integral of the current.
(explanation - I speak about true integrator results of which I showed several pages before. RIAA network is not a true integrator, it has 3 freq. breakpoints - just for the reason that someone wanted to say i was inaccurate).
They seem not to understand, no background. I give up, this is a loss of time. I will free the space for stories.
(explanation - I speak about true integrator results of which I showed several pages before. RIAA network is not a true integrator, it has 3 freq. breakpoints - just for the reason that someone wanted to say i was inaccurate).
They seem not to understand, no background. I give up, this is a loss of time. I will free the space for stories.
Last edited:
Last edited:
yes, I fell into that trap.
I got confused by folk referring to phase shift as if it were signal delay.
The loop gain must not send back a signal that causes instability. That instability is caused by the sum of the circuit delay plus the phase shift.
It's just fortunate that in Audio the phase shift predominates and the circuit delay is trivial.
I got confused by folk referring to phase shift as if it were signal delay.
The loop gain must not send back a signal that causes instability. That instability is caused by the sum of the circuit delay plus the phase shift.
It's just fortunate that in Audio the phase shift predominates and the circuit delay is trivial.
Agreed. it is not something that looks like the phase shift you sometimes see in scope pictures. It is of no consequence to the working of feedback in audio.
jan didden
Of course, depending on the opamp or discrete topology used, its SR, GBW etc. But, it has nothing to do with 90° phase shift reasoning. And even vinyl mistracking signal is not that fast for us not to be able to make a choice of appropriate opamp. It was a problem 25 years ago, but is no problem today. I have made a choice of 2 types of opamps with SR 55V/us that work great in RIAA phono pre. The circuit is not as simple as opamp only, but opamps may be very well utilized in RIAA preamps.
One way to design around the probem of high slew rate garbage at the input of the phonostage is passive EQ of the 75usec BEFORE it enters the amplification stage. I designed a passive inductive RIAA for ETF that does just that. By coincidence i even use the ADA4898 at the input. The reason i use it is, that it can swing 40mA clean so a feedback resistor of 300 Ohm can be used to limit the gain in the first stage. As funny as it looks, this stage works fine with the ceveat that the impedance of the cart. is known. In my case the 6 Ohm of my Titan i ( including losses in the connectors ) are tumed with a series resistor of 4 Ohm to have the required 75usec with a 0.75mH coil.
I put the coils in an oversized Mu-Metall can for low hum. Again this is a low Z design with 4 Ohm DC impedance. AC impedance goes up in the treble though so this is not exactly a zero ohm design.
I put the coils in an oversized Mu-Metall can for low hum. Again this is a low Z design with 4 Ohm DC impedance. AC impedance goes up in the treble though so this is not exactly a zero ohm design.
... and I can vouch that it sounds very good!
/OT: I see you made it home alright!
jan didden
Joachim -
try OPA627 (instead of OPA134) or even better OPA627+ buffer at the position of the 2nd opamp.
Best,
try OPA627 (instead of OPA134) or even better OPA627+ buffer at the position of the 2nd opamp.
Best,
Thanks Bob for explaining that. I know this because I had to learn this during my education .... I just liked to mention the "time delay" of the musical structure.
Jan
This is true regarding the electrical circuit. My answer is the same I gave Bob, I'm speaking from the delay of the musical texture...
Mr. PMA
why do you offend me, do you know me, my knowledge or my education? Have you ever listened to any of my designs?
Why do you offend other peaople here? It looks that you're Mr. Know-It-All ...
I will not lower himself (down) to your niveau and discuss anything with you, especially music and it's reproduction. Anyway thank you for your kind words...
I wish you all the best for your live!
Yes Jan, i made it home safe at least to Cologne and we drive further to my home in Sauerland today.
I was surprised too how well my little passive phono sounded but i do not claim that this is my best efford. I found it apropriate for a DIY festival. It is another option and very easy to build because it is so simple. As far as i heard from Martina your female partner liked the sound of our system too.
PMA, i was sure that you spot the OPA134 at ones and when you read my original MPP thread you find that it is not my favourite Opamp eather. I use OPA827 and ADA4627 when i want a Fet input nowerdays but i had them only as SMD not soldered to an adaptor yet and time was running. Sorry for compromising.
I was surprised too how well my little passive phono sounded but i do not claim that this is my best efford. I found it apropriate for a DIY festival. It is another option and very easy to build because it is so simple. As far as i heard from Martina your female partner liked the sound of our system too.
PMA, i was sure that you spot the OPA134 at ones and when you read my original MPP thread you find that it is not my favourite Opamp eather. I use OPA827 and ADA4627 when i want a Fet input nowerdays but i had them only as SMD not soldered to an adaptor yet and time was running. Sorry for compromising.
Personally I think PMA is rather decent and I wouldn't get offended by statements like this. I think PMA maybe has a point.
Joachim,
I am sorry but I have not reviewed the MPP thread, though I am of course aware of that thread.
IMO your choice of OPA827 and ADA4627 is perfect, sorry for any misunderstanding.
Best,
Folks with a water dependency view an amplifier as a basin, having walls that become more rigid when frequency goes up.
At lower frequencies, the walls are so soft that waves are reflected without a phase shift.
At unity gain frequency, the walls become totally inflexible and reflected waves experience a 180 degree shift of phase.
The wall, and it's love affair with frequency level, is an intrinsic design feature of the amp, and nothing changes that.
The way you view an amplifier seems like regarding it as 1-on-1 with a water basin, while in reality it's a bouncing charge thing that doesn't require to generate a water ripple to travel the distance.
Mr Macura is an acoustic engineering EE, i'd be somewhat pee'd off if he replied it takes indepth knowledge about aquatic wave and ripple theory, but he's fully entitled to point out that fully understanding an electrical thing requires adequate theoretical background/teaching.
Last edited:
I don't think his post was offending. Just facts that can be seen clearly if one wants to look.
What did you find offending?
jan didden
- Status
- Not open for further replies.