Terry can you scope direct on VAS out when square wave attached on input?
Oscillation isn't visible at the speaker output.
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Ohh i thought there was a Resistor but it is just a short. The raise c7 and c8 by 10%
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I see in #6069 that OS added a 22R resistor. Perhaps this is the resistor that you speak of. I will have to cut a trace to add it. Looks like he also removed a couple caps.
Thimios,
I will take some scope readings from the output of the IPS. I actually took readings of the IPS with just a pair of 100R resistors tied to the Feedback return. It looked perfect. I believe it is the way the IPS and OPS work together that is causing this.
Thimios,
I will take some scope readings from the output of the IPS. I actually took readings of the IPS with just a pair of 100R resistors tied to the Feedback return. It looked perfect. I believe it is the way the IPS and OPS work together that is causing this.
Make Changes In Steps
Hi Terry,
Have been following this thread for a long time and slowly gathering parts to build Kypton C, Infidel and symetrie. Will be a bit before I am done as I am slow.
Glad to see you have this "sort of" working. It does not look like anything catastrophic is going on, maybe some low level oscillation as previously suggested. Looks close.
Based on some stuff I have seen in my sims, A possible debugging approach might be (keeping it simple);
1.) Remove the opt1 folded cascode connections (if you have them) and see what happens at the output.
2.) Remove the 0.22uf "Cpb" emitter bypass caps and see what happens.
3.) Change the gain by adding the 22 ohm resistor
Beyond this it may get rather "hairy" (i.e. not so close) 😱
Also, what is the "sizzling" noise you are hearing ... from the speakers, from the board or from specific component?
Bill
Hi Terry,
Have been following this thread for a long time and slowly gathering parts to build Kypton C, Infidel and symetrie. Will be a bit before I am done as I am slow.
Glad to see you have this "sort of" working. It does not look like anything catastrophic is going on, maybe some low level oscillation as previously suggested. Looks close.
Based on some stuff I have seen in my sims, A possible debugging approach might be (keeping it simple);
1.) Remove the opt1 folded cascode connections (if you have them) and see what happens at the output.
2.) Remove the 0.22uf "Cpb" emitter bypass caps and see what happens.
3.) Change the gain by adding the 22 ohm resistor
Beyond this it may get rather "hairy" (i.e. not so close) 😱
Also, what is the "sizzling" noise you are hearing ... from the speakers, from the board or from specific component?
Bill
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Bc 560 550 C very high hfe often, hasard transistor other ,resistor 22 or33 to be perhaps to base respektive.
Here you go.
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Appears to be possible input slew rate over driven. Try temporarily increasing C2 to 470p or larger and see if there is any change to the transition edges. I also agree with others suggest of removing both Cbp caps, or at least reduce them to, say, under 150pF. These caps at 0.22uF can generate a big spike of current at the moment the circuit begins to recover from clipping, and this current is a real threat to lives of Q5 and Q7.
According to simulation is that not a good idea, while it will reduce HF gain it will also introduce a HF phase shift that could lead to oscillation
infidel 2
A complete test.
All these measurements on VAS + out.
A complete test.
All these measurements on VAS + out.
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infidel 2
The rest on VAS out.
The rest on VAS out.
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infidel 2
Now measurements on speaker out with a dummy load =7R
Picture 6 with 150nf//7R
Picture 7 with 330nf//7R
Picture 8 with 2u2//7R
Now measurements on speaker out with a dummy load =7R
Picture 6 with 150nf//7R
Picture 7 with 330nf//7R
Picture 8 with 2u2//7R
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Hi bimo do you believe that is stable?
Keep in mind that this oscillation picked by the coil always exist
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Yes, I think. Please play music until the heatsink hot then take measuring again.