Does it matter what kind of 100nf cap?Because the Vbe is not bypassed. 100nF added and the oscillations stop. I advised this on post 5. The CFP is stable, see the step responses
Post in thread 'Stability testing my new Rod Elliot P3A' https://www.diyaudio.com/community/...ing-my-new-rod-elliot-p3a.403473/post-7462178.
If the amp got destroyed because the output got shorted. This why the VAS got also destroyed. See also
Post in thread 'The Blameless CFP' https://www.diyaudio.com/community/threads/the-blameless-cfp.402614/post-7449527
Ceramic or mkt for example?
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.
Add 100nF across the C_E of Q9.
hayk has not stated if this is in a simulation, or if he has built this amp
I would use MKT or MKS for a 1uf servo integrator cap, since I know it won't affect SQ there. Not so sure about if its for compensating a CFP loop.
H
HAYK
It is on simulation, IanHegglun remarked thishayk has not stated if this is in a simulation, or if he has built this amp
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.
Okay. They all stop the oscillation, but do they all sound the same?Any type will work.
H
HAYK
This capacitor acts in high frequencies above the audio band. It should not make any audible difference.
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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Does it matter what kind of 100nf cap?
Ceramic or mkt for example?
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.Is this 100nF cap a better solution than the 100pF C6 in the P3a, and if so, why?
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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Lucky me.
The closest jaycar to work had a pair of bf469.
Unrelated, but I have what should be a quad each of hitachi 2sk1058/2sj162 coming from another store. Clearance stock at $5 each, last in the country.
Brick and mortar ftw
The closest jaycar to work had a pair of bf469.
Unrelated, but I have what should be a quad each of hitachi 2sk1058/2sj162 coming from another store. Clearance stock at $5 each, last in the country.
Brick and mortar ftw
H
HAYK
At low frequencies the impedance of the Vbe is low enough to shunt the nonlinearities of the capacitor. Even electrolytic 1uF used in many amplifiers is OK.
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.Lucky me.
The closest jaycar to work had a pair of bf469.
Unrelated, but I have what should be a quad each of hitachi 2sk1058/2sj162 coming from another store. Clearance stock at $5 each, last in the country.
Brick and mortar ftw
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.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.
I imagine they will come come raw given we're talking about jaycar....
Is putting the 100nF cap across q9 going to effect the current bias setting if I do this to the working channel?
Same question regarding changing r11/r12 to 100r
Same question regarding changing r11/r12 to 100r
There has been some less than complementary comment from some members who prefer EF2 or EF3 output stages. In fairness to these views I have simulated an EF2 output stage for supporting evidence such as shown below.
The test results below are for 5Vrms into 10R at 1kHz with no nfb.
s
The test results below are for 5Vrms into 10R at 1kHz with no nfb.
s
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