Redesign 544: „Rev/One 2018“

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Peter B.
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Lid geworden op: ma 22 sep, 2014 15:38 pm

Re: Redesign 544: „Rev/One 2018“

Bericht door Peter B. »

Hello everyone!

Tomorrow, I will have some time to respond to your interesting opinions on the two versions of the "Rev/One 2018" schematic.

Greetings
Peter B.
Kruger_BG
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Lid geworden op: zo 04 mar, 2018 10:42 am

Re: Redesign 544: „Rev/One 2018“

Bericht door Kruger_BG »

Hello Hans,
Thanks for taking your time to check the schematics. If we could face issues with the driver compensation we will go for the standard approach.
Can we borrow your filter design then ? This one - 544Mk2
If possible Peter can put optional headers on the main PCB. If someone wants to try more exotic filter schematics a second horizontal board to be mounted. This way we can keep the Peter's schematics as options.

Hello Rene,
Option 3 can be easily added.
Option 1 is very specific indeed. I downloaded the 587 schematic from MFBfreaks site, but such a tweaked baffle compensation is not apparently visible. No dedicated filter network available. At least i cannot see it.
Option 2 is neat. Not so straightforward as option 3, but uses the MFB system. And the original 544 has a baffle step compensation.
We will go for option 2 or 3. I guess 2 because it exists in the original design.
Hans
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Re: Redesign 544: „Rev/One 2018“

Bericht door Hans »

Kruger_BG schreef:Can we borrow your filter design then ? This one - 544Mk2
No problem. One of the basic ideas for this forum is that one can re-use everything that is published here. If someone doesn't like that they should not publish it on this forum.
Kruger_BG schreef:If possible Peter can put optional headers on the main PCB. If someone wants to try more exotic filter schematics a second horizontal board to be mounted. This way we can keep the Peter's schematics as options.
That is fully up to you.
Kruger_BG schreef:Option 2 is neat. Not so straightforward as option 3, but uses the MFB system. And the original 544 has a baffle step compensation.
We will go for option 2 or 3. I guess 2 because it exists in the original design.
In the 544Mk2 I used the X-over filters to compensate for the baffle-step effect.
Groeten,
Hans
Peter B.
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Lid geworden op: ma 22 sep, 2014 15:38 pm

Re: Redesign 544: „Rev/One 2018“

Bericht door Peter B. »

Hi Rene,
here are my answers to your questions:
Leave out the transistor stages. See also here
- I'm familiar with the Hans material, but it went out of my mind, so I put the transistor scheme for connecting the MFB / sensor that I tested and applied to a Subwoofer. We can use any schematic available.
Can you explain a bit more what the Linwitz tranform does in the loop? How will this affect the loopgain and phase margins? What is the Starbass filter stage doing?
- In a few words, the Linwitz transformer helps the bass driver reproduce the lower frequencies. See here: https://trueaudio.com/st_lkxfm.htm You are familiar with the subject anyway. Typically, only part of it is used. In the schematic I have put it for discussion. Infralow tones are also very important - they are enveloping the low signals ... And if the playback bandwidth starts at 35Hz, the infralow frequency passband should start 15Hz. I have taken this idea from a Nota Bene article. Will such a correction be compatible with MFB – it could be tested. We can bypass this opamp easily.
Was macht die Starbass-Filterstufe?
- Regardless of the type of sensor, it is good frequencies where it does not affect to be cut off. Example-here:
https://piratelogic.nl/data/images/prod ... ircuit.png
For the 3 amplifiers, use the full current amp as Hans proposed here. The AD0211 and AD0163 benefit al lot from a full current amplifier.
- Yes, the power amplifiers have options for the three possible feedbacks: Voltage, Current only and Mixed. We have to keep the impedance in a reasonable limit at the end of the frequency ranges. In addition, the three amplifiers can be separated from LP3. As I have shown here: Allgemeines Aussehen des Mechanikers 1.
Where is the bafle step compensation, or will this be done with the feedback loop adjustment?
- This baffle step compensation is implemented according to the box design. From the active correction, the signal can be corrected at the input of LP3. It can be done as it is with Rod Elliott or as proposed to be directly in the feedback path.
Make the design only applicable for a symmetrical transformer, you can modify the current transformer as I showed before or just buy a new toroidal transformer (better).
- Yes, that's my intention. Moreover, I ordered for the tests 4 pcs. toroidal transformers with electrostatic and electromagnetic screens. They are 120VA power and very, very high quality workmanship. I'm expecting a price bid. Once the price is known, I will also give the basic measurements of the finished transformers. Idle current is expected to be very low due to low iron core inductance.
To summarize, use the MKII as base, create one PCB for this (like David and Sander mentioned before) and turn all the amplifiers into current.
- When Hans pointed out the reasons for a simpler crossover (Danke Hans!), we decided on a possible optional change later. I will put the usual LP / HP Linkwitz-Riley filters and jumper configuration.
Leave out the That4305, or make it optional.
- The limiter can be made simpler. THAT variant plus option.

As a conclusion:
- My aim with this design is to have electronic for both RH544 and for a new MFB box with new drivers and using StarBass sensors.

Regards,
Peter
Peter B.
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Lid geworden op: ma 22 sep, 2014 15:38 pm

Re: Redesign 544: „Rev/One 2018“

Bericht door Peter B. »

Hello everyone again!

A) Here I present a third version of the LP3 schematic: - Input circuit with baffle corrector, limiter, crossover, input for the MFB sensor, ect.
Filter 3 RevOne2018.PDF
1. Input circuit with baffle corrector.

2. Active Subtractive Subbass Filter up to 70Hz. The input signal can be obtained directly from the output of (1) or from the Low Pass Filter 4kHz.

3. After (2.) follows Dynamic Sub-bass Limiter. If someone decides not to use THAT4305, it is possible to set a different limiter (connector pins H1 ... H5). The schematics are as suggested by Chris.

4. From the output of the OP N5B, the signal is used to supplement the bandwidth of the LF amplifier, with a 500 Hz low pass filter.

5. An amplitude-controlled sub bass signal after the limiter, the other signal after the 500 Hz low pass filter and the corrected signal from the MFB sensor, are fed to the summator circuit with the N4A.

6. After the N4A output follows the second correction OP (MFB) of the sum signal. The R22 trimmer controls the signal to the LF amplifier.

7. The remainder of the crossover includes a 4-order Low Pass Filter and two 4-Order High Pass Filters. Accordingly, the cut-off frequencies according to the RH544 specification, they are 500 Hz and 4 kHz. The filters can be calculated for other frequencies as well as for a different type configuration. Just like 544MK2. Each output of each channel (vor MF and HF) is adjustable - trimmers R56, R62.

8. The MFB sensor input has been changed to MFBlabs.nl according to the suggested by Hans Schematics.
Filter 3 RevOne2018.jpg
B) Here are the simulations to determine the elements in the baffle correction:
Baffle Step Compensation-2 RH544.png
Until July 1st / 5th, I can make minor changes to the wiring diagram. In the next few days I will introduce the remaining blocks of the PL3 board and the three amplifiers.

Regards,
Peter
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motoindo
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Re: Redesign 544: „Rev/One 2018“

Bericht door motoindo »

Just a short msg as I'm officially still on holidays 8-) I would suggest to skip the dynamic rumble all together because it doesn't serve any purpose with 544 like setups where the bass driver is large enough to produce a satisfactory low end @ low listening volumes.
Chris Camphuisen
mfb does to the ear what a pretty face does to the eye
Peter B.
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Lid geworden op: ma 22 sep, 2014 15:38 pm

Re: Redesign 544: „Rev/One 2018“

Bericht door Peter B. »

Hello everyone,

My silence on the topics here has arisen because I have been ill for a long time. I even had to go to hospital for a week. Afterwards in the last few weeks I could continue the work on the 544 redesign.

1. On version 3 of the motherboard LP3, Chris wanted me to remove the limiter. It may be that without limiter everything would go well, but the experience with the MFB boxes shows the need for a limiter. As we all know, this is needed for increasing the dynamic range of low frequency broadcasting. Using the THAT circuit from Chris and limiting the effect of the limiter to only the lowest frequencies can completely eliminate a basic error-hit. Namely, his work in the amplitude limitation should not be noticeable. In its frequency range and at the limit of the sub-depth frequencies, the MFB gain of the corrector increases and then this can lead to overload of the loudspeaker even for low level.

For this reason, I decided to leave the limiter in the circuit. However, the limiter will be available on request on a sub-board!

2. The MFB processor was made according to the suggested circuit of Nota Bene, that is Nail Muhamedsjanov. The block diagram can be seen here:
Blockschaltbild des ЭMFB Prozessors.pdf
The coming LF signal is fed to the mixer stage and then mixed together with the sensor corrected signal (Z3) and passed on to the corrector stage (Z2). Z2 allows two variants of assembly:

a) As an incomplete integrator.

b) As an elliptical rejection filter for the case where the sensor shows very strong resonances behind the work area.

Another advantage of the MFB processor here is the lack of separation capacitors between the blocks. This, together with the current Amplifire vor the woofer channel, enables safe operation of the system without positive feedback in the circuit contour. As a bonus, you can achieve a deeper MFB feedback.

Regards,
Peter

LP3 Schematic (Teil1) vom 15.09.2018
RevOne2018 Schematic LP3-F4-Ver096.pdf
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Hans
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Re: Redesign 544: „Rev/One 2018“

Bericht door Hans »

Peter B. schreef:.....
LP3 Schematic (Teil1) vom 15.09.2018
One quick remark. The drain current of the j-FET in the sensor changes with the temperature of that FET, this has "some" consequences.
Groeten,
Hans
Peter B.
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Lid geworden op: ma 22 sep, 2014 15:38 pm

Re: Redesign 544: „Rev/One 2018“

Bericht door Peter B. »

Danke Hans!
Ich werde mich Morgen mit der Schaltung auseinandersetzen. Die Berechnungen sollen überprüft werden.
Gute Nacht!
P.

(Thanks Hans! I will deal with the circuit tomorrow. The calculations should be checked.
Good night!
P.)
Peter B.
MfbLabs Gebruiker
Berichten: 68
Lid geworden op: ma 22 sep, 2014 15:38 pm

Re: Redesign 544: „Rev/One 2018“

Bericht door Peter B. »

Hallo Hans!

When I simulated this unfortunate circuit of the current mirror, I noticed that there is a problem with a higher amplitude of the signal. But then I was distracted by the other simulations and forgot to see what was going on. :? This specific dimensioning of the current mirror has only caused problems. So far I had always used similar values to the components of the current mirror like yours.

Now that I have read your topic "Openner electronica met FET ingang" in detail, I am now determined to use an OP-circuit for this redesign "RevOne 544" instead of current mirror. To integrate this schematic into the rest of the MFB processor, I had to use a simplest level shifter. This will also simplify the work of the servo circuit of the MFB processor.

Hans, I simulated your proposed circuit # 3. Subsequently, at the location of the inverting operational amplifier, a level shifter has come. I had compiled these two simulations with older simulations of the original RH544 schema. Here you get all simulation documents because of the completeness as a PDF file. In the simulations, instead of the complex piezo circuit diagram, I only use one capacitor as a replacement. It may be that I had seen somewhere in their publications how you had specified the piezo capacitance of the Philips sensor plate by about 1.5nF. I have 8 pieces of new speaker for RH541 and the two of RH544, but all the sensors are unfortunately covered with the dust caps so that I can not afford this cap for capacitance measurement easily.

My request to you is whether, with the mention of her name, I could also use circuit no. 3 in "RevOne 544"? And second, whether the specification of 1.5nF capacity of the sensor plate is right?

Groeten,
Peter
SIMULATIONEN für RevOne 544.pdf
Die [b]unglückliche[/b] Schaltung.pdf
Hallo Hans in Deutsch.pdf
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