Yes it may matter. Nonlinear and or piezoelectric caps can be bad news, even if presumed to only affect outside the audio band. You might try C0G/NPO, small-ish physical size MKP, Mica, etc., which can be used for such types of purposes (if they are available in the needed uf value). If found necessary for damping purposes, a low value linear resistor might be useful in series with the cap. May not be necessary though.
It is on simulation, IanHegglun remarked this
Post in thread 'Linearizing the CFP crossover - P3a of Rod Elliot as example' https://www.diyaudio.com/community/...-of-rod-elliot-as-example.402148/post-7426979
Any type will work.
If its a piezoelectric transducer then why can't it transduce in the audio band? If its nonlinear then why can't its nonlinearity effects intermodulate with the audio signal to produce audible artifacts? Its a well known problem with forward biased semiconductor junctions in some situations.
Just saying, if different caps sound different to many people on good systems, then some assumption that its all in the mind of the listeners is not necessarily within the scope of expertise of typical EE training. Thus, sometimes it turns out the EE is wrong when outside of his area of expertise. IOW, critical thinking is domain specific.
So, I ask if they sound different. Maybe they do or maybe they don't. If they do, then we need to better understand the mechanism. That's all.
Just saying, if different caps sound different to many people on good systems, then some assumption that its all in the mind of the listeners is not necessarily within the scope of expertise of typical EE training. Thus, sometimes it turns out the EE is wrong when outside of his area of expertise. IOW, critical thinking is domain specific.
So, I ask if they sound different. Maybe they do or maybe they don't. If they do, then we need to better understand the mechanism. That's all.
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C6 is in the feedback loop of a common emitter stage Q6 and the level of capacitance of 100pf will be multiplied by the gain of the stage. I see no local discharge route for this as the carriers in n material are electrons and the negative supply is rich in electrons -so nothing doing there. There is an alternative route through the bootstrap circuit. connecting to the Vbe where it runs into more electrons in Q9 emitter and can cannot pass.
Hey presto behold the 100n bypass cap connecting to the opposite circuit half.
Without this Q6 is a laggard.
Setting the Vbe still seems to be a problem if high levels of output standing current have to be used. In an earlier post I suggested reducing R11 and R12 from 220R to 100R which has been taken up however the suggest of adding 100R resistors in the emitters of Q5 and Q6 passed without notice. I believe this would make Vbe biasing easier to set.
Another change I would try would be to replace Q4 with BF469 which is still available in Austrralian and New Zealand over the counter outlets.
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You could use these in place of Q7 and Q8. to build "My MOSFET amplifer designed by Mooly one of the thread administrators.. This thread was last active on 7 April 2023.
I hope these devices did not come in the raw as they are sensitive to static which can destroy them. Mooly's circuit is a variation of a theme by Linsley-Hood. I have some output stage simulation on my Windows pc. which is in the coldest room in the house. I'm working on an android where it is warm and I am in hearing range of my wife who has permanent disabilities.
That's exactly what I will use them for. Probably not for a years though given all the other projects in the queue.
I imagine they will come come raw given we're talking about jaycar....