So I've started this build. I'm just building the power amp for now and have a question regarding the voltage rating for the two capacitors: C11 and C19. It appears there is the potential for 425 VDC to appear across the caps at power on and perhaps even afterwards. Does this call for a 600V rating? Seems like that would be a rather large capacitor...
This is a version of the Sunn 100s. That schematic shows only 35 VDC between C11 and the cathode.
Thanks for your considerations as I'm kinda at a stall point...
silverfox.
Capacitor Voltage Rating Question
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Capacitor Voltage Rating Question
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Stevem
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Tttt
yes, make C11 a 500 volt cap.
Also note that coupling / bypass type caps have a ac voltage rating also that should not be exceed.
Most 400 volt rated caps can only handle 250 volts of ac or audio signal going into them,and this can be a issue in some PI / driver circuits like in class AB2.
Also note that coupling / bypass type caps have a ac voltage rating also that should not be exceed.
Most 400 volt rated caps can only handle 250 volts of ac or audio signal going into them,and this can be a issue in some PI / driver circuits like in class AB2.
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Capacitor Voltage Rating Question
If a real GZ34 is used, then as long as the EF86 is functional, the cap would never 'see' much voltage, and a 250V rated C11 may be ample.
As the screen current is about 1/5 of plate current and the screen grid resistor is about 5 x the value of the plate load resistor, then the screen grid voltage should be about the same as the plate voltage, noted as 88V.
But if quick start rectification is used, then yes, it may see close to full unloaded VB+ at start up, so 500V
The 'presence' control seems strange?
I think it would work more like a local stage gain control, but it's within a global feedback loop.
I don't think that the amp could operate in AB2, as there's no bias shift mitigation?
But yes, a 400V rating for C17 would be insufficient.
Full Weber scheme http://www.tedweber.com/media/kits/6s100_schem.jpg
Original Sunn 100S http://bmamps.com/Schematics/Sunn/Sunn_100s.pdf
Watch out for errors!
As the screen current is about 1/5 of plate current and the screen grid resistor is about 5 x the value of the plate load resistor, then the screen grid voltage should be about the same as the plate voltage, noted as 88V.
But if quick start rectification is used, then yes, it may see close to full unloaded VB+ at start up, so 500V
The 'presence' control seems strange?
I think it would work more like a local stage gain control, but it's within a global feedback loop.
I don't think that the amp could operate in AB2, as there's no bias shift mitigation?
But yes, a 400V rating for C17 would be insufficient.
Full Weber scheme http://www.tedweber.com/media/kits/6s100_schem.jpg
Original Sunn 100S http://bmamps.com/Schematics/Sunn/Sunn_100s.pdf
Watch out for errors!
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Here's how the Weber 6s100 sounds
Courtesy of Fusion Bear:
https://www.youtube.com/watch?v=a8ukDw_j1KU
The interesting thing about the voltage rating; When I went looking for a 10uf 600 VDC cap the are fairly spendy- $8.00 and unavailable unless you want to buy 1400 or was it 14000 from mouser. The dimensions are fairly large also so it has me wondering if Weber really used the type in question.
What is the purpose of such a large value, 10uf, in the presence circuit? Would a .1 work just as well?
silverfox.
https://www.youtube.com/watch?v=a8ukDw_j1KU
The interesting thing about the voltage rating; When I went looking for a 10uf 600 VDC cap the are fairly spendy- $8.00 and unavailable unless you want to buy 1400 or was it 14000 from mouser. The dimensions are fairly large also so it has me wondering if Weber really used the type in question.
What is the purpose of such a large value, 10uf, in the presence circuit? Would a .1 work just as well?
silverfox.
Re: Capacitor Voltage Rating Question
Are you talking about:SilverFox wrote:... there is the potential for 425 VDC to appear across the caps at power on and perhaps even afterwards ...
1) typical running conditions? or
2) the startup surge? or
3) unloaded secondaries?
2 and 3 above may or may not be similar, depending on whether your system is 'slow start' or not, so its better to anticipate voltage ratings that can safely cope with unloaded secondaries
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Just don't want to blow a cap
I think I've found the answer. First the voltage won't rise very high since the cathode will only be sitting at .8 volts, so a 50 or 100 volt rating on the 10uf cap should be fine- I think... Just don't want to blow the 10uf cap.
What would the difference be if the 10uf is a nonpolar vs. Electrolytic?
silverfox.
What would the difference be if the 10uf is a nonpolar vs. Electrolytic?
silverfox.
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