If you cannot get the simulation running in Tina try LTspice. It works there. Though instead of actual logic gates, I use two voltage sources with square wave outputs of opposite polarity. Maybe that will also fix your problem?
Jan
Jan
Dual Polarity Voltage Multiplier...
- Thread starter rogs
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Yes, I had the simulation working with that, I wanted to provide a simulation file with actual logic gates so that someone wanting to build could try different resistor/capacitor combinations in case they wanted to minimize number of different components in the BOM, or wanted to try different clocking frequencies.
I've been tinkering with diverse variations of your OPIC circuits, and the more i play with them the more i get irritated by phantom power limitations. If all those tube mics have clunky PSUs that follow, why wouldn't we have dedicated PSUs for opamp based mics? This is definitely my next step. No more hustle with voltage multipliers, no limitation of how many opamps in a mic we get to use for various purposes, and the benefit of basically unlimited headroom is priceless.
I just want a mic where capsule's SPL limitation is the only limiting factor and i believe this is the way to go. Sorry for this rant, just had to share some frustration after several hours of LTspice desperation.
I just want a mic where capsule's SPL limitation is the only limiting factor and i believe this is the way to go. Sorry for this rant, just had to share some frustration after several hours of LTspice desperation.
You could take Thor's approach and modify your pre-amps with lower value resistors and increase the phantom voltage to 60v so the phantom can supply more power.
The nice thing about modern power supplies is if you make an external supply it can be very compact and lightweight compared to the old tube mic supplies.
rogs
Well-known member
As I've mentioned before, I'm a great one for 'simple' inside the mic, and to move everything else (eq etc) further down the signal path.
So the simplicity of the original OPIC LDC wth a single op-amp appealed to me.
My first OPC multipattern mic uses 3 opamps, and a single polarity VM. ...Obviously that draws more current - so a lower DC supply is available for the op-amps - and each extra op-amp and associated signal path ressitors will add some extra noise as well. (Not a lot - but some! ).
The original idea of this dual VM was to enable a multi-pattern mic to be created, using just one op-amp again.
Allowing for 1mA of current to power a VM, adjusting the values of the op-amp supply feed resistors (R4 and R5 on the OPIC LDC schematic ) to be 2k2 instead of 10k should make the available DC supply to the op-amp should be aroud 36v.
Close to the upper limit for many op-amps - and certainly for the OPA164* series.
There will obviously be some attenuation of the output signal, working into this lower impedance load, but that should be less than 0.5dB, so not that significant.
That should give a maximum signal rail to rail output swing of c.36volts p-p. Probably slightly less than that, to allow for a finite impedance of the phantom power supply, but not a lot less I suspect.
I'm not sure that you'd need any more headroom than that ? ... and that's still using a standard phantom power supply.
Of course if you want to include more op-amps internally, for other functions, then those figures would no longer compute.
As I mentioned before, I'm not a fan of doing any 'non-linear' signal path modifications at mic level, so I quite like the idea of a single OPA1641 being fed from a 36v DC supply as being the simplest impedance converter, with the maximum output signal that an op-amp can provide.....
And that would still only need standard phantom power..
My post was certainly not a critique towards your original design which is marvelous. It led me to further experimentation for which i just need more juice.
rogs
Well-known member
No, I didn't read you post as being critical .... I was just intrigued to know why you needed more power.....
I think maybe I'm taking the idea of doing everything apart from the impedance converter outside the mic a bit too seriously ?
mhelin
Well-known member
To get the double power (or more) you could also use a passive external splitter box and connected the mic output to two or more mic pre input channels (increases the load a bit though). On the other hand you would like to record both front and back diaphragm outputs anyway (so a XLR5->2x XLR3 adapter cable is needed anyway). Also the efficiency of 48V to whatever voltage op amp circuits like to use could be improved using DC/DC converters instead of zeners.
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