F5m kit

[tonyEE]

...

So approach this as a group effort of supporting the people who are here, regardless of their skill and knowledge. It’s the only way to keep the community going.

Well said...

BTW, I'm sure many of us are willing to help too.... I know I am. I can fry electronics like the ham fisted pro I am.

"Diode smoking done by a professional... don't do this at home..."

But seriously, we should all be helping in any way we can, after all I think this forum gives a lot...

(thanks)

+++

Hmm... can we get a list going for those interested in buying the kit?

 

[kannan_s]

We are not doing Graduate or masters degree in this forum. This forum for building things at your home to enjoy good music. It is also for learning Electronic principals including mathematical formula if one wishes. Technical Skills??? Are Spice Simulations and Electronic design skills required to participate here ?? No one is forced to teach as much as learn here. We have to learn a lot from Nelson in his interaction with his kit builders. He always try to explain in way for them to learn from fundamentals.
Do not fear to ask questions even if it requires simple ohms law. Apologies for OT here but my 2cent

 

[Holzarbeiter]

I miss AndrewT!

 

[Zen Mod]

you and Pa are in a quiet but heated competition

No way Jose, I can't be in any competition with Pa

After I taught him everything I know, he successfully soared in direction of using less and less parts ........ while I'm going slowly in opposite direction

(ignore main fact that I'm under his permanent disgrace, so everything I do is more or less just making muted noises around)

 

[BeardyWan]

The name's Dennis. And I'm 37!

 

[citationfan]

Iam curious about if F5M circuit work with +/- 32Volt without hesitation?

 

[poseidonsvoice]

Iam curious about if F5M circuit work with +/- 32Volt without hesitation?

Reviewing and re-reviewing the writings of Nelson Pass is key. In Mr. Pass' excellent F5 turbo article he reveals many different improvements and permutations including the use of higher voltage rails. Since he said it best, let's paraphrase:

The more technically astute DIYer may note that the input Jfets are now being exposed to greater voltage and dissipation, and this might be a concern. With respect to voltage, the operating point of these devices is around 30 volts, 5 volts over their rating. In actual testing these devices break down around 43 volts, and I depend on Toshiba's famed conservatism to carry the day. If you don't want to trust Toshiba as much as I do, then you can cascode these devices, which is covered here later. The average dissipation of the Jfets with a 32V supply will be about 28 volts times the operating current. A 2SK170 or 2SJ74 with a 10 mA Idss will operate at about 8 mA in this circuit, which gives a dissipation of about 220 mW. A quick calculation shows that its maximum junction temperature at 220 mW is reached with an ambient temperature of about 70 deg C.

A wise DIYer will either select a Jfet with a lesser Idss (say 8 mA) and/or see to it that the Jfets gets some cool air or a little heat sink. Or you can cascode them.

If you want to calculate the maximum junction temperatures of the Jfets, you can apply this equation:

Tj = Ta + (P * (Rjc + Rcs + Rsa))

Where,

• Tj = junction temperature
• Ta = ambient temperature
• P = power to be dissipated
• Rjc = thermal resistance of junction to device case
• Rcs = thermal resistance of device case to heatsink
• Rsa = thermal resistance of heatsink to ambient

Best,
Anand.

 

[citationfan]

Ok, thanks for reply!
Iam not frightend about the Jfets, they will last,
I will try it, but have no IRFP140/9140 on hand, only matched Irfp240/9240.

 

[citationfan]

Is it possible to take Mosfets 240/9240 over 140/9140?
What will be shortcomings?

 

[barossi]

Regarding transformers: Is a 400W (18V+18V) transformer sufficient for an F5M stereo set?

 

[Zen Mod]

yup

 

[N Brock]

Is it possible to take Mosfets 240/9240 over 140/9140?
What will be shortcomings?

For you: https://diyaudiostore.com/pages/irfp140240

Regarding transformers: Is a 400W (18V+18V) transformer sufficient for an F5M stereo set?

Yes, though a bit overkill. NP's article recommends a 200VA and a 300VA transformer at the bottom of page 5

 

[KevinHeem]

In some respects you’re not far from the truth.

 

[Zen Mod]

as always is the case, when ZM involved

sometimes far, sometimes not

 

[barossi]

Regarding transformers: Is a 400W (18V+18V) transformer sufficient for an F5M stereo set?

yup

I was wondering, while for F5 i found that:

---

Power supply requirements​

A Bipolar power supply of (+/- 24V) is required. This will require an 18V+18V (or 36V Center Tapped) transformer from 300-500VA, and PSU capacitance of 30,000uF per rail or more. The PSU for the F4, F5, and Aleph J are all essentially identical. See the F5 build guide for details.
---

 

[birdbox]

I'm pretty sure the intent is 300-500VA single transformer for the amp. The "per rail" is intended to apply to capacitance value only.

 

[Zen Mod]

if that helps - regular FW Donuts are around 300VA (one Donut per amp), by memory

easy to check on numerous pics everywhere

 

[Dennis Hui]

Yes, the early FW production pieces used 300VA Plitron transformers (sadly no longer available)

 

[gary s]

Nelson, are there any discernible differences in sound, harmonics, speaker preference etc that you can identify between the original FW F5 and this scaled down F5M version?

 

[EUVL]

https://www.diyaudio.com/community/threads/pass-f5m.406472/post-7534522

For the original see First Watt article.


Patrick