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PostPosted: Sat Jun 18, 2016 6:00 am 
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Location: Toronto, ON, CA
It's always like this, friend ask me to build something, end up besides his stuff, I also got mine...take DCB1 for example...he got his DCB1, and I got one for myself. Thing is, in order to build the thing for friend to top qualify, I have to build one for myself to "learn" and make sure...and to be honest, it's also a good excuse to build something for myself...

Now, a friend ask me to build a F5 T, could be V3...and I am obliged to build one for myself probably even before build my friend's...

I don't need that much power though, even 50W F5T V2 is too much for me...or a 25W F6, or 25W F5 T V1?

I don't think F6 as F5's upgrade...

The only headache is the Fairchild mosfets if building F5, I can get genuine one for P, but not N...probably end up using IRFP240/9240...


Last edited by Frank Wang on Tue Jul 12, 2016 6:04 pm, edited 1 time in total.

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PostPosted: Sat Jun 18, 2016 6:48 am 
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Have anyone listened both F5T and F6? Any comparison?


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PostPosted: Sat Jun 18, 2016 7:58 am 
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Location: Winnipeg, MB, CA
Six Moons has reviewed all of them, including the new F7
http://6moons.com/archivelibrary/alphabet.html


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PostPosted: Sat Jun 18, 2016 9:13 am 
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wpgwpg wrote:
Six Moons has reviewed all of them, including the new F7
http://6moons.com/archivelibrary/alphabet.html


Thanks.
Yeah, I know those "reviews"...but want see reviews from canuck forum members


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PostPosted: Sat Jun 18, 2016 1:44 pm 
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Location: Ottawa, ON, CA
Frank Wang wrote:
Now, a friend ask me to build a F5 T, could be V3...and I am obliged to build one for myself probably even before build my friend's...

I don't need that much power though, even 50W F5T V2 is too much for me...or a 25W F6, or 25W F5 T V1?

I don't think F6 as F5's upgrade...

The only headache is the Fairchild mosfets if building F5, I can get genuine one for P, but not N...probably end up using IRFP240/9240...

Frank,

I've tinkered with the F5 and used it to drive a 10" dual concentric pair of Tannoys.
Its OK.
However, without any question, a class A MOSFET power amp - like the Aleph J clobbers the F5.
Its not even close.
If you are concerned about power dissipation of the Aleph J, you could back off on the biasing.

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PostPosted: Sat Jun 18, 2016 5:13 pm 
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Uunderhill wrote:
Frank,

I've tinkered with the F5 and used it to drive a 10" dual concentric pair of Tannoys.
Its OK.
However, without any question, a class A MOSFET power amp - like the Aleph J clobbers the F5.
Its not even close.
If you are concerned about power dissipation of the Aleph J, you could back off on the biasing.



Thanks Uunderhill.

I will probably build them all...

Some of Nelson Pass's comments on his own amps...below thread#6:
http://www.diyaudio.com/forums/pass-lab ... -amps.html


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PostPosted: Fri Jul 08, 2016 5:23 am 
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Probably will go build F6...anyone also interested?


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PostPosted: Fri Jul 08, 2016 7:26 am 
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Uunderhill wrote:
Frank Wang wrote:
Now, a friend ask me to build a F5 T, could be V3...and I am obliged to build one for myself probably even before build my friend's...

I don't need that much power though, even 50W F5T V2 is too much for me...or a 25W F6, or 25W F5 T V1?

I don't think F6 as F5's upgrade...

The only headache is the Fairchild mosfets if building F5, I can get genuine one for P, but not N...probably end up using IRFP240/9240...

Frank,

I've tinkered with the F5 and used it to drive a 10" dual concentric pair of Tannoys.
Its OK.
However, without any question, a class A MOSFET power amp - like the Aleph J clobbers the F5.
Its not even close.
If you are concerned about power dissipation of the Aleph J, you could back off on the biasing.

Image


Isn't the F5 a Class A MOSFET power amp :?


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PostPosted: Fri Jul 08, 2016 7:50 am 
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AJ is sweet for sure...since you already have AJ, probably I should build F6 so can compare later on;-)

F5 T is out of picture for now...too much power for me.

Just curious the input transformer in class A amp like M2 and F6.


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PostPosted: Fri Jul 08, 2016 8:53 am 
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jst_canuck wrote:
Isn't the F5 a Class A MOSFET power amp :?


If I recall correctly, the output stage of the F5 is biased at around 1 amp.
So that under a certain output voltage the F5 operates in class A mode.
But after a certain output voltage it switches into class A/B.
The higher bias current is set to, the better the F5 sounds.

IMO the output impedance of the F5 is too high for many speaker loads - even for speakers like Tannoys.
I would have hate mail if I wrote this on a certain other website.
The solution was the F5 Turbo - which many output MOSFET's were paralleled up - which lowers Zout.
With a lower Zout, the amp can deliver more current to the load.
Remember drivers need current to build up a magnetic field.

Where as with a true Class A amp, like the Aleph J, there is a current source (Q5 & Q6)
and other transistors (Q7 & Q8) amplify 360 degrees of the signal.

-- 08 Jul 2016 17:07 --

Frank Wang wrote:
AJ is sweet for sure...since you already have AJ, probably I should build F6 so can compare later on;-)
F5 T is out of picture for now...too much power for me.
Just curious the input transformer in class A amp like M2 and F6.


Frank,

I've tinkered with my own version of a Class A amp - its very close to the Aleph J.
Biased at just 1 amp - it has incredible bass control with a pair of B&W 110's.
I can't believe B&W 110's are capable of producing that much bass.
But haven't had the chance to complete the design.
Another, "more important" project (like my kitchen or roof) always come up.

Before considering the F6, I would find out if you source the Jensen JT-123-FLPCH transformers.
Since both output MOSFET's are both n type devices, the transformer is being used as a phase inverter.


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PostPosted: Fri Jul 08, 2016 11:24 am 
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That's why I asked...I have contacted Jensen, and will buy from them....if you want, I can count you in. Also thinking draw the PCB myself...I'd rather spend money on transformer and power caps.


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PostPosted: Sat Jul 09, 2016 5:16 am 
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Frank,

I'll pass on the F6 (no pun intended).

Just need the time to finish my own amp.

But I wonder what the PSRR of the F6 is ?

BTW: Have you seen the newer Antek power transformers ?
They have a shield between the primary and secondary windings.
http://www.antekinc.com/content/AS-4218.pdf

My one experience with this company was very good.
Shipping to Canada may be the biggest issue.


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PostPosted: Sat Jul 09, 2016 11:05 am 
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Location: Toronto, ON, CA
It's ok, I will just buy board from diyaudio...not worth draw the PCB and have factory do it if only a few PCBs...

Never used Antek...
I normally use Plitron(factory on my way to work), which has been acquired by ACAL (ACAL also owns NORATEL transformer)...

I don't have gears to measure PSRR...


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PostPosted: Sat Jul 09, 2016 4:23 pm 
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https://www.plitron.com/acal-acquires-p ... facturing/

http://www.acal.co.uk/acal/en/home


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PostPosted: Mon Jul 11, 2016 10:16 am 
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Uunderhill wrote:
....

jst_canuck wrote:
....


Guys, you have done the AJ, any parts differ from the "default"? What's the Zenner voltage you end up with?



Thanks
Frank


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