Capacitor p0rn
- Thread starter adamct
- Start date
fullheadofnothing
Moderator
A poly Oly!
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It's the water!
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It's the water!
i luvmusic 2
New member
I just ordered my 2 Mundorf 100uf 400V Film Caps just waiting for the supplier's reply. 
i luvmusic 2
New member
I received the 2 Mundorf 100uf 400V film caps,I would like to know if these film caps are polarize i look at them and they don't have any polarity sign?Thanks!
i luvmusic 2
New member
THANK YOU!
Paul Joppa
Moderator
Depending on who you ask, bypass caps will improve the treble, damage the treble, or have no effect. There is no known way to consistently predict which answer you will get. But if you try it and see, you will know the only answer that you care about!
In the first post of this thread, adamct says:
"Below is a 200uf metalized polypropylene motor START cap that I bought by accident. These are NOT suitable for use in the Crack. They will explode if you try to install them. This one is shown here just for fun."
My question is: why?
I believe they will work just fine as output coupling caps. No explosions.
As filter caps, I see no reason why they would "explode." They are rated at 450 VAC and the DC rating for a cap with a 450 VAC rating is usually about 1.4141 times VAC or about 636 in this case, so you are not going to over-volt the thing. As far as current goes, motor run caps are built to continuously carry much higher currents, but a motor start cap ought to be able to carry the ripple current of this power supply, no? Motor run caps have to handle a fairly high peak current and are likely able to carry reasonable currents for extended periods, I should think.
Personally I haven't heard any difference using all film caps in the power supply vs. good low-ESR electrolytics in the audio circuits I have experimented with (which does not include any SET amps.) I HAVE been able to clearly tell the difference in A/B comparisons between electrolytics and film caps when used as output coupling in the Crack / Speedball.
"Below is a 200uf metalized polypropylene motor START cap that I bought by accident. These are NOT suitable for use in the Crack. They will explode if you try to install them. This one is shown here just for fun."
My question is: why?
I believe they will work just fine as output coupling caps. No explosions.
As filter caps, I see no reason why they would "explode." They are rated at 450 VAC and the DC rating for a cap with a 450 VAC rating is usually about 1.4141 times VAC or about 636 in this case, so you are not going to over-volt the thing. As far as current goes, motor run caps are built to continuously carry much higher currents, but a motor start cap ought to be able to carry the ripple current of this power supply, no? Motor run caps have to handle a fairly high peak current and are likely able to carry reasonable currents for extended periods, I should think.
Personally I haven't heard any difference using all film caps in the power supply vs. good low-ESR electrolytics in the audio circuits I have experimented with (which does not include any SET amps.) I HAVE been able to clearly tell the difference in A/B comparisons between electrolytics and film caps when used as output coupling in the Crack / Speedball.
mcandmar
New member
Motor starts are generally electrolytics and and are only intended to be in a circuit for a short time during startup, motor runs are usually poly and always in the circuit. I dont see why a motor start would fail with miniscule currents in a tube amp, but i also dont see why you would want to use one.
Grainger49
New member
Many AC rated caps are PIO caps and are bare metal. I have a pair of them in a PDMPS power supply for my FP 2 and in the last 12 years these haven't exploded. They are called Motor Run caps.
I looked back at the first post and those are distinctly different from what I am used to seeing on a motor. Most stay in the circuit. A start cap is taken out of the circuit by a switch on the motor that opens at a set RPM. It is just for the starting torque.
I'll add a picture today.
I looked back at the first post and those are distinctly different from what I am used to seeing on a motor. Most stay in the circuit. A start cap is taken out of the circuit by a switch on the motor that opens at a set RPM. It is just for the starting torque.
I'll add a picture today.
mcandmar said:
One of the very first Crack type amps I built, a long time ago (maybe 10 years now) ended up coming together with a bunch of surplus parts I had sitting around. I ended up accidentally using motor start caps in the power supply (by accident), and several of them exploded at about the same time rather immediately after I started using the amp.
Motor start caps aren't intended for continuous duty. They are very cheaply made as well, so they are likely to not sound that great. If you use them, they will fail, and they will explode their oily goop all over your Crack and whatever is under it. It's also quite likely that they will damage whatever headphones you have plugged into them at the time, and if they do survive, they will smell like exploded capacitor for a few years.
Motor run caps are great though.
Grainger49
New member
Here are a few of my stash. As you can see 3 of the 5 have been in amps already. These are motor run caps and they are not small.
