feedback balances the two drivers and flattens the frequency response.
a resistor across the cap is definitely NOT what you want.
a resistor across the cap is definitely NOT what you want.
Feedback isn't something I have experimented with much previously, so there is the possibility of more idiocy in the attached. I have swapped out the first stage for two halves of an ECC83 per channel (I do have some TubeTech E813CCs in the spares box which could be nice) to get more first stage gain and then attempted to wrap some local feedback round each side of the output. LTSpice appears to give the gain of the final stage at about x5 compared to around x18 without feedback.
Out of preference I would want to keep to a two stage design just to keep the power supply requirements and outlay under control so
Is there a good model for the impedance of electrostatics/electrets which can be used to check if the output impedance is low enough?
Out of preference I would want to keep to a two stage design just to keep the power supply requirements and outlay under control so
Is there a good model for the impedance of electrostatics/electrets which can be used to check if the output impedance is low enough?
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You can put 200pF across your outputs to see what the FR looks like.
I would take the feedback from the outputs and cross them back to the first stage.
I would still load the plates with resistors and use your CCSs for R9 and R1.
I would take the feedback from the outputs and cross them back to the first stage.
I would still load the plates with resistors and use your CCSs for R9 and R1.
You could consider a two stage circlotron topology, but OTL amps often suffer from current insufficiency. Or a solid state amplifier using the SRD4 transformer.
From the tech data it looks like 110pF for the SR30.
At this point I am going into idiot mode, as with a first attempt at cross feedback around both gain stages I am getting some odd sim behaviour. With a 1V sine input everything seems to work but with anything else it is coming up with odd voltages at each of the test points.
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> a first attempt at cross feedback
Is that positive feedback? Or are my thumbs tangled?
What are R23 R24 for? Looks like they throw-away stability.
Is that positive feedback? Or are my thumbs tangled?
What are R23 R24 for? Looks like they throw-away stability.