What AC amplifier are you talking about? 😱
C215 and C217 are 100uF each, giving the total value of 50uF. Do you understand what 50uF in the feedback loop gives you in combination with 22K resistor at the input? It gives you an integrator with 1 sec time constant. What "range up to megahertz" are you talking about??? It will not really pass even 10Hz. It's a slow DC servo integrator. The second OpAmp section is simply an inverter - one of the ways to arrange a non-inverting servo (inverting integrator + inverting unity gain amplifier).
I'm talking about the servo input leads from SV. This is input. You see there is a low-pass filter: R231С10. The cutoff frequency of this filter is about 700 kHz. I was wrong, speaking about the band in megahertz. 🙂 But I was right about everything else. 🙂
I will say it again, slower. The servo has two inputs. Servo performs two functions.
To one input of a servo amplifier of DC, here opamp works as an integrator,
to the second input of the amplifier AC, here opamp works as follower.
You look closer.
To one input of a servo amplifier of DC, here opamp works as an integrator,
to the second input of the amplifier AC, here opamp works as follower.
You look closer.
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You're trying to imagine this circuit is related to speaker cable compensation one way or the other. It's not. It's just a well-designed servo.
The reason of having R231 equal to R229 is the fact that Mitsubishi M5218 OpAmp has got BJTs at the input. So, for having a good DC balance, base currents must be equal. This is also the reason why low value (22K) is used for these resistors and high value (50uF) is used for integration capacitor.
It would not be an issue if, for example, LF412 would be used for the purpose (virtually zero input currents).
Much more interesting is differential error correction in the output stage - L401 inductor-based circuit - Onkyo engineers' development.
Perhaps you don't understand me. I will repeat again.
1. The SV wire connects from the servo to the terminals of speaker systems. This wire forms a magnetic loop to catch interference. This wire is a mile long. It should particularly be protected from interference along its length.
2. They could take the reference for the servo much closer - from the signal ground. This wire would be short and not be caught interference.
3. What was needed a long wire servo SV and protection from interference? For only one purpose. This is elementary.
4. The engineers of the company Onkyo, they used the same method in preamps to compensate for interference in a inter-unit cables. Here is the manual preamp ONKYO P3060R. The right side clearly drawn schematic is exactly the same servo, Q521 in the lower right part of the diagram.
5. The wire goes from pin 5 Q521 through the R549 to the connector "servo sensor" near the connector "output 1".
6. The difference is that you will say again: this is the reference for servo. In fact, it's circuitry to compensate for the interference of industrial frequency 50/60 Hz, which penetrate into the interconnect cable. You will say again that the amplifier does not amplify the AC current from this input?
7. To achieve success, we should be attentive to the work and thoughts of the old engineers.
Is this servo circuit compatible with Symasui?
If yes i will built this and test just from curiosity
If yes i will built this and test just from curiosity
Thimios, it will surely work fine.
It's also based on BJT-input dual op-amp, so input resistors' value is relatively low (18K), having integrator capacitor's value relatively high.
Anyway - with better op-amp it will work even better.
Yes Valery it is working (tested)!
No magic smoke!😱
A new test for comparison two servo circuits,servo LF412 and servo like Onkyo using NJM2068L is coming soon!
I will post this in Slewmaster thread to keep this thread for N.S and your's IPS.🙂
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Have you worked out why the servo version steps to very high offset after start up and then corrects back to low offset?
At the first i have test the original sircuit with TL072.There are two problems.Long settling time and final offset about 2.8mV.
Then a LF412 in the TL072 position.The long settling time remain but final offset is zero.
Using steps and ARTA low frequencies i see that start up offset is very high, the same using a Fluke 289 in record mode.
Then playing with the values of R26,27,28 and C12,C13 I found the appropriate values.
The final test was using an offset control circuit from a comercial amplifier the Onkyo A8057.
The rest in Slewmaster thread soon.
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Thanks. I realized while I was assembling this that it would be a good idea to add DC detection and output relays right on the amp because there won't be any binding posts on this one, so I'm going to an improved version after a successful test run.
I finally got my pair of boards running. Both channels work right out of the gate. The only problem I am having is setting the bias clamp.
Following the setup instructions to adjust the clamp I am very near the end of the adjustment on one channel and run out of adjustment on the second.
Following the attached schematic the wiper of R43 is all the way to R40. One channel adds the prescribed 5mv to the bias but the second only adds about 3mv. The only resistor that is easily changed on both boards is r44.
I'm looking forward to boxing this one up and giving it a real listen
I'm off now to visit with family. Hope everyone is enjoying the day..
Evan
Following the setup instructions to adjust the clamp I am very near the end of the adjustment on one channel and run out of adjustment on the second.
Following the attached schematic the wiper of R43 is all the way to R40. One channel adds the prescribed 5mv to the bias but the second only adds about 3mv. The only resistor that is easily changed on both boards is r44.
I'm looking forward to boxing this one up and giving it a real listen
I'm off now to visit with family. Hope everyone is enjoying the day..
Evan