The reason for caps change is that i seen an unusual woofer movement🙁
I hope that isn't something wrong😕
No problem at all. Even 1uF will be fine there. But not less, otherwise distortion at very low frequencies will start increasing.
From a short listening test it seems that everything is ok.
Amplifier tested without any protection tryk at clip levels all this morning.
Some musical parts (solo drummers) was used as woofer test,nothing wrong this time!
Cone of the woofer move well,nothing unusual now.
Please don't ask for comparison.
I can't use my main speakers without any protection.😉
Amplifier tested without any protection tryk at clip levels all this morning.
Some musical parts (solo drummers) was used as woofer test,nothing wrong this time!
Cone of the woofer move well,nothing unusual now.
Please don't ask for comparison.
I can't use my main speakers without any protection.😉
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I'm still rounding up parts for your protection system. I hope to send it out later this week.
Jeff don't worry!🙂
I will test this CFA and in any case it will take a long time to finish my amplifier 😉
I guess I will wait to see if you come up with new ops boards. One question, to test the ips boards, can I just short all the pins together?
Hi Terry,
Yes, no problem - you can short PD+, ND- and NFB together and treat this node as a front-end's output.
Cheers,
Valery
Vbe multiplier
We are in a big trouble again.
This is about Vbe multiplier.
When heat sink temperature rise at about 54°C idle current becomes unstable.
You can see on emitter resistors mVmeter ,20mV jump to 8mV jump rapidly to 0mV again 20mV and so on.
When temperature falls below το 45°C,you see again something like 20mV what is stable and variable linear as temperature falls to about 30mV what is the idle current adjustment.
We are in a big trouble again.
This is about Vbe multiplier.
When heat sink temperature rise at about 54°C idle current becomes unstable.
You can see on emitter resistors mVmeter ,20mV jump to 8mV jump rapidly to 0mV again 20mV and so on.
When temperature falls below το 45°C,you see again something like 20mV what is stable and variable linear as temperature falls to about 30mV what is the idle current adjustment.
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This is a somewhat strange behaviour. I heated my prototype (different layout) up to 90C - bias decreased slightly, then, as it was cooling down, bias increase back to the nominal value. No quick "jumps".
Jeff, did you experience something like this with your prototype?
Jeff, did you experience something like this with your prototype?
In my earlier prototype with the Vertical VFA, I did notice some bias current changes with temperature, but it was more related to the temperature of the VAS transistors. If I touched the VAS transistors with my fingers bias current would change quite a bit. If there was a draft around the board bias would really wander too. I increased the size of the heat sinks on the VAS transistor, and along with the recommended changes to a few capacitors for stability is seemed to settle down. In my bench testing of the latest boards, the Vertical inputs seem to wander a lot, but the VZ-Z4 was fairly constant.
I think Antek has finally got me proper transformers coming for my latest builds, so hopefully I can properly test this one soon.
Thimios, maybe see what happens if you install a huge heat sink on the VAS transistors of the input and see if things improve.
I think Antek has finally got me proper transformers coming for my latest builds, so hopefully I can properly test this one soon.
Thimios, maybe see what happens if you install a huge heat sink on the VAS transistors of the input and see if things improve.
Jeff,i don't believe that is a matter of VAS temperature.
Touching the VAS transistors i can't feel any high temperature.
This was tested using the CFA as IPS.
I will try again using the VFA as IPS.
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In mine the VAS transistors weren't very warm either. 115F if I recall correctly. A couple degrees change really effected the VAS current, which in turn changed the bias current of the outputs.
I don't see changes in bias current,i see quick jumps between 0 up to 20mV and so on!
Okay. I get it now. So you are getting intermittent bias current. This sounds like a cold solder joint.
I can't believe such a scenario,but who knows😕
May be it's time for OPS testing alone...
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Do you have the second one built? Testing a second one would be the easiest way to verify if it's a build or design error. If it acts the same the problem wouldn't likely be a build issue.
Yes i have built the second one.
This second one uses the VFA IPS,i will test this as it and then i will test second one with the CFA IPS