First Watt F7 review

[maty tinman]

Scheme, from here:

6moons audioreviews: FirstWatt F7 [page 2]

-> http://www.6moons.com/audioreviews2/firstwatt2/5.png

 

[fab]

Hi Maty

From where did you get the schematic? More to the point, do you know it works? It looks to me like the output from the MOSFETS is fed back positively to the input, independent of Rsen which doesn't feel right.

To me , it looks like topology type 1 from this post 442:
http://www.diyaudio.com/forums/pass-labs/275921-first-watt-f7-review-45.html#post4585617

Fab

 

[maty tinman]

quebecdiy.net

Off topic

Fab, I admire your assemblies (and Pinocchio too): quebecdiy.net Transistors

 

[Ian Macmillan]

To me , it looks like topology type 1 from this post 442:
http://www.diyaudio.com/forums/pass-labs/275921-first-watt-f7-review-45.html#post4585617

Fab

Stupid me, it does indeed look like this topology. Still doesn't feel intuitively like it would work but I clearly need to go and try it.

Ian

 

[2 picoDumbs]

Stupid me, it does indeed look like this topology. Still doesn't feel intuitively like it would work but I clearly need to go and try it.

Ian

Before building anything you better read this whole thread.

 

[generg]

I tell you all I really needed was F4 and Pumpkin.....

the rest was all luxury.......

 

[Soundhappy]

This morning read F7 Part2 first page

6moons audioreviews: FirstWatt F7

...to be continue

 

[Ian Macmillan]

Before building anything you better read this whole thread.

Thanks for the warning although I already read most of the thread. I now recognise that the type 1 topology is more a theoretical one than a practical proposition in that it is way too sensitive to resistor values. Type 2 looks to be a better bet.

 

[fab]

From topologies shown in post 442, which would be best for minimum damping factor variation upon real load speaker impedance that varies with frequency?
Thanks
Fab

 

[Nelson Pass]

From topologies shown in post 442, which would be
best for minimum damping factor variation upon real load speaker impedance
that varies with frequency?

As a concept they all work, that's the central point. The imperfections are
mostly the qualities of the gain stage itself. The best in this regard is the one
with the highest amount of negative feedback and/or the topology with the
lowest intrinsic (open loop) output impedance.

Of course if you already have a very low output impedance, the need for
positive current feedback is very small.

 

[fab]

As a concept they all work, that's the central point. The imperfections are
mostly the qualities of the gain stage itself. The best in this regard is the one
with the highest amount of negative feedback and/or the topology with the
lowest intrinsic (open loop) output impedance.

Of course if you already have a very low output impedance, the need for
positive current feedback is very small.

From the above it looks like the open loop gain needs to be higher to have good results with positive feedback....but I thought that lower open loop gain due to use of Lateral mosfet was the reason to use positive feedback...

Fab

 

[Nelson Pass]

From the above it looks like the open loop gain needs to be higher to have good results with positive feedback....but I thought that lower open loop gain due to use of Lateral mosfet was the reason to use positive feedback...

The lower amount of negative feedback on this topology puts in a situation
where the output impedance is not very low. Positive feedback lowers the
output impedance.

If you already have a low output impedance, then you have less need of
this technique.

 

[wdecho]

A little more of the review is trickling in from 6moons.

6moons audioreviews: FirstWatt F7

 

[Zen Mod]

now they're really worsening the writing style

 

[jvhb]

now they're really worsening the writing style

Yeah the writing style and odd metaphors and expressions often makes it difficult to read. I enjoy the overall approach and thoroughness though - and I love the mountain view out his big glass doors!

 

[generg]

Hi Srajan,

Thanks for this "never ending" review of the F7. Never before I read such a broad review where one amp was so thouroughfully compared with so many speakers and some other amps.
Your comments about possible reasons that the F7 or 30.8 sounds better with the one or other speaker are very interesting and uncommon in its broadness.

It is of course also a bit hard to see how insecure the perfect matching of an Amp with a speaker is in reality. Compared with the normal reviews, your review is irritating and revealing at the same time.

Thank you!
And continue please.... ))

 

[Zen Mod]

yup

considerably improved writing style , on later pages

 

[Bare]

I'm liking the Font used which says: Firstwatt F7
Trying to deduce what variant of Wright's style it actually is

 

[CeeVee]

There are a couple you can try...Reynolds Art Deco and Gradl font....i'm beting it's the second ...but they are very similar.

Both are free fonts....

Just remember the Logo is Nelson's.... respect that.

There are plenty of gorgeous free fonts about....design your own logo.....it's fun.

 

[Bare]

Absolutely! I'm an Architect so I have a Fondness for Fonts.. and was trying to identify it... is all
Thanks.. by the way.
Seems you were right; Gradl seems as close But Reynold Art Deco Font seems as 'it'
It's an attractive one I understand it's choice.