F5 Turbo Builders Thread

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#1,043
Howdy,
I set my V2 up with no sinks on the diodes,and adjusted the bias around and kept some fingers on the diodes,I set them to around 350 and then cranked the volume and that's when they come on ,I didn't let them stay on too long but a small heatsink should work,I think I will use a heatsink long enought for 2 diodes, maybe keep them closer heat tracking wise.
I read papa's article on them he said they work on the peak times of conducting to keep the impeadance low at high current draw ,if I got that right,LOL.
Thanks for the reply Buzz!
Regards,
NS
 
#1,045
noSmoking said:
Howdy,
I set my V2 up with no sinks on the diodes,and adjusted the bias around and kept some fingers on the diodes,I set them to around 350 and then cranked the volume and that's when they come on ,I didn't let them stay on too long but a small heatsink should work,I think I will use a heatsink long enought for 2 diodes, maybe keep them closer heat tracking wise.
I read papa's article on them he said they work on the peak times of conducting to keep the impeadance low at high current draw ,if I got that right,LOL.
Thanks for the reply Buzz!
Regards,
NS
Click to expand...

They dont com eon suddenly, as they are sharong current with the resistors that they are in parallele dwith. As the current increases through that junction the Vdrop increases in proportion to the ratio of their resistance to the Rs. I am not sure they ever complete bypass the Rs, as this would cause instability in the output, moat likely leadin gto thermal runway. I woul dimagine, they work to maintain a similar Vdrop across Rs, regardless of current passing through the junction. Imagine Vdrop staying in the .4-.6V range instead of steadily climbing with increased current. This would affect degeneration amount, bias point, and gain, all in one. Sliding bias😀
 
#1,046
buzzforb said:
They dont com eon suddenly, as they are sharong current with the resistors that they are in parallele dwith. As the current increases through that junction the Vdrop increases in proportion to the ratio of their resistance to the Rs. I am not sure they ever complete bypass the Rs, as this would cause instability in the output, moat likely leadin gto thermal runway. I woul dimagine, they work to maintain a similar Vdrop across Rs, regardless of current passing through the junction. Imagine Vdrop staying in the .4-.6V range instead of steadily climbing with increased current. This would affect degeneration amount, bias point, and gain, all in one. Sliding bias😀
Click to expand...
Thanks buzz I'll go back and read that article again,
Regards,
NS
 
#1,047
buzzforb said:
They dont com eon suddenly, as they are sharong current with the resistors that they are in parallele dwith. As the current increases through that junction the Vdrop increases in proportion to the ratio of their resistance to the Rs. I am not sure they ever complete bypass the Rs, as this would cause instability in the output, moat likely leadin gto thermal runway. I woul dimagine, they work to maintain a similar Vdrop across Rs, regardless of current passing through the junction. Imagine Vdrop staying in the .4-.6V range instead of steadily climbing with increased current. This would affect degeneration amount, bias point, and gain, all in one. Sliding bias😀
Click to expand...


I thought that people were having trouble even having the diodes turning on? ie , the circuit never gets driven hard enough to reach those V and current levels.
In the V3 with 4 pr is it then necessary to put heatsinks on the diodes?
 
#1,048
You want some sort of heat dissipation on the diodes no matter what. You have t consider there ability to get rid of heat. With out any thermal coupling. Their internal temp would vary greatly and make for an unstable amp. As a point in fact, in the Paradise bilders thread, there have been people who have been able to affect bias by simply blowing across the boards. Temperature is a major part of any amp build.It is exponentially more important in CLass A. If you want them to cut on, bolt them to the main sink. For most speakers, V3 without diodes may be sufficient, but it nce to have them.
 
#1,057
What sort of speaker protection are you guys thinking of using? Or none at all?

I am not really crazy about using protection with relays in the speaker circuit. Not with the amount of current that the F5TV3 is able to generate on the output. Any ideas?
 
#1,058
i'm going for NONE🙂
when there is more then one pair of outputs, the risk of total failure decrices.
if one output fails. the outhers keep on going. exept if it shorts. then it most likely is construction fault. i've run my dual output F5 for allmost 1 year now. whitout a hickup. and no protection🙂
i also did run some aleph 2 monoblocks for one year. whitout protection. on one of those i had a output failure. one transistor burned up. i did't notice it before 2-3weeks later🙂 no problem. the amp did keep on playing🙂
 
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#1,059
That is what I am also aiming for. Anyway, that is how I am doing my KSA50 clone that is now almost complete.

BTW, one should never underestimate the amount of work and cost involved in building a decent case for a Class A monster. Besides the cost in metal, it is the time as well as tooling costs if you have not got all the tools yet. I am doing the cases usually by hand as I love metalworking also (No CNC and milling by machines, just a Tablesaw, Drill and a bunch of files).

I bought a M6 Counterbore the other day sothat I can hide the heads of my capscrews, and it cost me a whopping R400 (about $50 US). Maybe I should import my tools also.
 
#1,060

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