F5 power amplifier

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#4,682
HI brian

for caps I haved a good service from audiocap , Campbell is diyA user on vendor bazar, 5€ shipping cost to italy😉

or panasonic tsha from digikey

for heatsink if you want, we can do a combinate order from conradheatsink ,for MF35-151.5 62.64€ for a pair ,plus 68€ shipping ,with half price on ship not so bad.....

you can add later coil, from capsandcoils
 
#4,683
f5 heat question

good mornign campers
just fired up a new f5 with barross's big heat sink and have a few quesitons-
the mosfets run warm- I was hoping to get away from fans but maybe not this time, at about 125 degrees farenheit measured off the surface next to the mosfet- I can leave my finger on the device but its pretty hot-I left it running for about two hours yesterday, tweeking the bias, and that temp was pretty stable- is this too hot?
Second querie- the MUR3060twg are also running pretty hot at about 125 degree farenheit- I cann't tell from the data sheet- is this too hot?
thanks for your input
rob
 
#4,684
Re: f5 heat question

rob lenk said:
good mornign campers
just fired up a new f5 with barross's big heat sink and have a few quesitons-
the mosfets run warm- I was hoping to get away from fans but maybe not this time, at about 125 degrees farenheit measured off the surface next to the mosfet- I can leave my finger on the device but its pretty hot-I left it running for about two hours yesterday, tweeking the bias, and that temp was pretty stable- is this too hot?
Second querie- the MUR3060twg are also running pretty hot at about 125 degree farenheit- I cann't tell from the data sheet- is this too hot?
thanks for your input
rob
Click to expand...


Rob, up to 60-65c is okay for Mosfet temperature output, with temp probe directly touched to plastic casing of FET. Higher is not recommended. I usually bias till I get there. of course I do this over a course of a day (6-8 hours) to make sure the sinks are fully warmed up.

My temp probe is cel. so 65c is 150f.
My diodes never seem to run hot, I attach them to bottom of chassis however, in case they ever do. There maybe a problem there. With the heat we have been having, everything is probably running quite hot.
:hot: 😀
 
#4,686
Hi,
scientific wire company supply enameled copper wire on reels from 100grams to 1000grms.
If your order arrives on a plastic spool then you have a ready made air core inductor that will be much cheaper than buying from any coil supplier.
Rapid also supply on 500gram reels but they are slightly more expensive.
 
#4,687
Re: f5 heat question

rob lenk said:
good mornign campers
just fired up a new f5 with barross's big heat sink and have a few quesitons-
the mosfets run warm- I was hoping to get away from fans but maybe not this time, at about 125 degrees farenheit measured off the surface next to the mosfet- I can leave my finger on the device but its pretty hot-I left it running for about two hours yesterday, tweeking the bias, and that temp was pretty stable- is this too hot?
Second querie- the MUR3060twg are also running pretty hot at about 125 degree farenheit- I cann't tell from the data sheet- is this too hot?
thanks for your input
rob
Click to expand...


Maybe you can order about 10-12 inch lengths instead of 8 so they'll run a little cooler. The problem is the MOSFETs are so close together. I wished he made them a little beefier too.
 
#4,691
I imagine that it could also be a function of heatsink efficiency. So when we bias up we get 'better' sound. So is this because the mosfet sounds better at a certain temp or is it because of the bias point. Maybe you bias it up to 2amps and it sounds great but is that because of the temp of the device or the current? Can we tune a heatsink to get better sound rather than biasing a mosfet to the point of destruction?
Uriah
 
#4,694
Not to be argumentative, I certainly appreciate the conversation. It just isnt working out with what I have heard yet. See TeaBag brought his F5 over and it took about an hour, little less, to sound good. So to me that meant that the heatsink had to get to certain temp. Following that logic I figured that the mosfet sounds best at a certain temp or at least above a certain temp.
Whats happening here?
Uriah
 
#4,695
udailey said:
Not to be argumentative, I certainly appreciate the conversation. It just isnt working out with what I have heard yet. See TeaBag brought his F5 over and it took about an hour, little less, to sound good. So to me that meant that the heatsink had to get to certain temp. Following that logic I figured that the mosfet sounds best at a certain temp or at least above a certain temp.
Whats happening here?
Uriah
Click to expand...

What you see there, is most likely that everything settles in the right parameters, which in the first place had been adjusted at full working temperature.

If you measure the circuit when it's cold, many measurements would be off target.


Magura 🙂

EDIT: BTW that's not being argumentative, I call that curiosity 🙂
 
#4,697
udailey said:
See TeaBag brought his F5 over and it took about an hour, little less, to sound good. So to me that meant that the heatsink had to get to certain temp. Following that logic I figured that the mosfet sounds best at a certain temp or at least above a certain temp.
Whats happening here?
Uriah
Click to expand...

I wouldn't be coming to such conclusion yet. There are many other low power circuits, that do not feature mosfets or need heatsinks, yet they are also claimed to sound better after an hour or so of warm up.
 
#4,699
Magura said:
What you see there, is most likely that everything settles in the right parameters, which in the first place had been adjusted at full working temperature.

If you measure the circuit when it's cold, many measurements would be off target.
Click to expand...

That's pretty much the case. Almost always the bias goes up with
temperature and the performance improves over an hour or so.

😎
 
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