An F5 mono with only 1pair of output devices has a current draw of ~ 1.308A. The bias of the output stage is ~1.3A. The difference is the current flowing down through the jFETs.
A stereo F5 with double 1pair of output devices (4 in total) has a current draw of ~2.616A and each output stage is biased to ~1.3A.
Nowhere does quiescent or continuous current draw approach 5.2A.
A stereo F5 with double 1pair of output devices (4 in total) has a current draw of ~2.616A and each output stage is biased to ~1.3A.
Nowhere does quiescent or continuous current draw approach 5.2A.
So it's 1.3A for both the N&P channel mosfets and not per mosfet. Thank you AndrewT for the clarification. So is there any other reason you can think of for the 30A bridge recommendation in in the power supply?
Actually, the recifiers in the F5 are 35A. It doesn't hurt to have extra surge capacity. Rectifiers are cheap enough. I wouldn't use 8A ones.
Hi labjr,
The BYW-EX have peak current of 80A. I don't disagree though that rectifiers are cheap. It's just interesting that NP uses 25V caps for 25V rails but specifies 35A bridges where 8A might be sufficient. I was just wondering if there is something else here to consider.
80amp surge current rating is not a lot. When there's a lot of capacitance a power supply, it's like a dead short when turned on. Most soft recovery diodes have lower surge current rating and fail easier than regular bridge rectifiers.
If diodes are cheap then a little overkill can't hurt.
If diodes are cheap then a little overkill can't hurt.
I would make a guess that Mr.Pass purchased a huge quantity of the bridges that he found worked the best for these applications. There have been threads where he talks about rectifiers, and it's obvious that these rectifiers have been chosen carefully, not just because of cost.
There was something Mr. Pass wrote about how one of the aspects (recovery or speed or something) of the "fashionable" diodes was actually not beneficial for an amp PSU. I wish I could find it or (better) if Papa would chime in... 🙂
Here is an article by Papa on power supplies:
The Importance of the Power Supply
That's probably what you're looking for:
heinz1
Tanks for posting that article.
Loads of juicy bits to be analysed understood dissected and pondered about as for anything that Papa write + like is stile.
In regard to the rating of the bridges the word surge is to be considered.
IMO 35 A is ok 50 A even beter going for less and the surge may turn around and bite your bottom.
A second word is temperature de-rating even a single piece of wire got it.
You may find that the bridges are rated at 35A at 25 C or such
Posting third decimal places (and wrong) figures in regard to power consumption or suggesting the use of valve rectifiers totally pointless posting just for the sake of it.
Each one of our F5 is slightly different just because each single mosfet be slightly different from another.
IMO
I think I got the wrong bridges (PB3508 Vishay)
1 they suit the PCB
2 It is what I have
3 I can change them if the sound changes.
Tanks for posting that article.
Loads of juicy bits to be analysed understood dissected and pondered about as for anything that Papa write + like is stile.
In regard to the rating of the bridges the word surge is to be considered.
IMO 35 A is ok 50 A even beter going for less and the surge may turn around and bite your bottom.
A second word is temperature de-rating even a single piece of wire got it.
You may find that the bridges are rated at 35A at 25 C or such
Posting third decimal places (and wrong) figures in regard to power consumption or suggesting the use of valve rectifiers totally pointless posting just for the sake of it.
Each one of our F5 is slightly different just because each single mosfet be slightly different from another.
IMO
I think I got the wrong bridges (PB3508 Vishay)
1 they suit the PCB
2 It is what I have
3 I can change them if the sound changes.
I think in recent years Nelson has changed his opinion a bit.
http://www.diyaudio.com/forums/pass-labs/93721-np-recommended-rectifier-diode.html
http://www.diyaudio.com/forums/pass-labs/93721-np-recommended-rectifier-diode.html
Each time i listen to that guy i get myself in trouble(s).
http://www.diyaudio.com/forums/pass-labs/28336-aleph-x-builders-thread-34.html#post1674000
Surge voltage is tolerated for how long? and how often?
What if one buys a different 25V capacitor with an apparently similar surge rating?
What guarantee do we have for consequential damage as a result of operating a capacitor in excess of rated voltage?
This is silly.
I cannot understand why NP recommends a 25V capacitor for a nominal 25Vdc supply. This has come up before and we seem to have buried our collective heads in the sand.
Speak for yourself --
Panasonic series T-UP, 35v nominal, 44v surge.
Question - does the CL-60 thermistor help hold the starting voltage down?
Also, NP has used the 25v caps in this commercial designs for quite some time now, and he says he has had an effective 0% failure rate...
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Well done.
You are brave enough to speak out.
It appears too many will not speak out for fear of upsetting other Members.
You are brave enough to speak out.
It appears too many will not speak out for fear of upsetting other Members.
Maybe the Panasonic capacitors are of good quality, conservatively rated and Nelson knows this. Evidently, First Watt uses the same parts in all the F and J series amps. I don't recall any owners, dealers or reviewers complaining about premature failure. So I'm not going to doubt his judgement.
I don't think I'd want to use 25V rated bargain brand cheapo caps though.
I don't think I'd want to use 25V rated bargain brand cheapo caps though.