F6 Amplifier

[buzzforb]

Originally Posted by lhquam

Told me what? Do not forget that high values of Rswip1 and Rswip2 mean higher output impedance and lower damping factor. There is a tradeoff between lower THD and lower Zo. Also consider that small "tweaks" to the relative values of Rswip1 and Rswip2 are comparable to minor adjustments to Rs to correct for transconductance differences of the output FETs and reduce 2nd harmonic.

Forget pot and do same thing with different Rs and cap positioning. Both caps don't have to be in same place. All things affect everything and just simmig only goes so far. Listen to cap above on both.( I know you have it that way). Now take upper cap and connect bellow top Rs. Listen and then test not only THD but also harmonic breakdown. Shape the sound man.

[lhquam]

You cannot get the 2nd harmonic minimum with just the above/below combos unless you try many many combinations of Rs-above and Rs-below. The variable adjustment greatly simplifies things and does not require readjustment of the DC bias.

Originally Posted by buzzforb

Forget pot and do same thing with different Rs and cap positioning. Both caps don't have to be in same place. All things affect everything and just simmig only goes so far. Listen to cap above on both.( I know you have it that way). Now take upper cap and connect bellow top Rs. Listen and then test not only THD but also harmonic breakdown. Shape the sound man.

[Zen Mod]

Originally Posted by buzzforb

.... Shape the sound man.

my man Buzz ...... that's good enough for sig

[lhquam]

Perhaps my post with the THD vs Freq plots wasn't clear. These were NOT simulations, they were measurements of the actual PCB using the pots.

Originally Posted by buzzforb

Forget pot and do same thing with different Rs and cap positioning. Both caps don't have to be in same place. All things affect everything and just simmig only goes so far. Listen to cap above on both.( I know you have it that way). Now take upper cap and connect bellow top Rs. Listen and then test not only THD but also harmonic breakdown. Shape the sound man.

[Zen Mod]

I just ran some measurements....

that was pretty clear

[buzzforb]

Ilquam,
You are the man. You have put forward a tremendous effort and have offered lots of information that has been helpful, but I am weird. I want to know what you hear.
What differences you perceive, and why you think they are occurring. I am trying to take advantage of your knowledge to help shape my sound, but i cant do that with measurement, solely. I am perhaps asking for the wrong thing(my ignorance again), as I think i want the frequency sweep showing the breakdown of the harmonic structure. Simple version is seen in 3rd pic of this link.

Using FFT spectrum analysers for audio amplifier design

[lhquam]

ZM: How much more performance-wise can be squeezed out of the F6 Conceptual Schematic beyond what I am seeing? How will I know when I am getting close?

Originally Posted by Zen Mod

that was pretty clear

[Nelson Pass]

Originally Posted by Zen Mod

Pa is having fun

zillion of posts ,based on teaser

Perhaps in the future I will let you guys do all the work.

In the meantime, I will suggest that you have taken it about as far as
it will go, now that you are just down the choices of the Rs values.

I'm at the coast finishing the F6 article up, and no doubt you will be
pleased with yourselves when you see it.

[willamp]

Originally Posted by Nelson Pass

Perhaps in the future I will let you guys do all the work.

In the meantime, I will suggest that you have taken it about as far as
it will go, now that you are just down the choices of the Rs values.

I'm at the coast finishing the F6 article up, and no doubt you will be
pleased with yourselves when you see it.

I have been watching this whole affair since it started waiting for a working schematic from Mr Pass. And, at the same time being amazed by the talents of this community. I don't have the skills to go from the teaser to working circuits myself but I have tried to follow all the great minds posting their thoughts here. Kudos to all who have elevated a simple audio transformer to the celebrity status of being the centerpiece of over 1800 posts.

While I was waiting I've started collecting parts for an F4 to join my F5. Will I be able to complete it before I'm compelled to collect the parts for an F6?...time will tell.

[Zen Mod]

Originally Posted by Nelson Pass

.....

proud Pa