F6 Amplifier

[PKI]

Big!

BTW, you can make a cab for markaudio drivers from your desk ;-)

 

[flocchini]

NEW TOY - NICE !!!!

 

[buzzforb]

It would work nicely. It, like so many things, remains unfinished. Really nice piece of figure maple plywood. THat is 5 filar winding, BTW. IT will give a sweet couple of watts very soon if all goes according to plan.

 

[dimkasta]

Nice one Justin

But look what I got

They are breeding... soon I will have four

 

[buzzforb]

Nice clean build. I really want some of those Fischer sinks. They make a 400mm version that would be perfect.

 

[dimkasta]

They are modushop

 

[buzzforb]

Fishcer has similar, but with longer fins.

 

[Zen Mod]

Cinemag , 5-filar

that's for sissies , needing bridged

 

[buzzforb]

Might try different FE on this one, using Quasi B1/SLCF/CAlvin buffer. Should ease the need for transistors. Got the Exicon here as well, but they will more than likely end up in M2 bastardo. PInout is different, making play time difficult. Crazy Swede building balanced amp as well

 

[Zen Mod]

buffer or buffer or buffer , they're good enough if they're good enough

as Pa sez - you need more zeroes ?!?

however , name of the game is Fun , as long you don't expect mucho difference from some things ; in contrary , you can be dissapointed

 

[stajo]

I'm not building a balanced amp. I'm building a true symmetrical amp. Tail is SE. Hopefully Andrew or/and ZM gets the itches now

 

[buzzforb]

name of the game is Fun

 

[buzzforb]

I'm not building a balanced amp. I'm building a true symmetrical amp. Tail is SE. Hopefully Andrew or/and ZM gets the itches now

I surrender before beginning.

 

[PKI]

ZM, this forum was not the same without you for the last weeks

 

[Zen Mod]

..... Tail is SE. Hopefully ......

when you have idea , everything else is just semantics

 

[Zen Mod]

ZM, this forum was not the same without you for the last weeks

yup

The Court is dry without The Jester

 

[PKI]

Some experience from Saturday playing with my F6(no THD analyzer yet, only ones attached to my head):
1. I had F6 with no FE degeneration and R13=0.1R R=0.
Very deep soundstage, but too much distortions -- harshy sound.
2. Same but R13=0.05R. Better distortion and almost same soundstage. Just didn't like its tonal balance.
3. Symmetrical one with variable 2nd harmonic from the F6 article. Very clean like F5.
4. Made 5 turns of trimpot to make a neg. phase shift (I.e. R13). That's it! Like it better than everything. Soundstage, clean and very soft and pleasant tonally.
for what it worth.

 

[PKI]

Boys, how can I measure THD spectra of F6 FE? If I make output Rs symmetrical and measure the whole amp will it be enough?

 

[buzzforb]

Just measure whole amp while adjusting. At the end of the day, it is the final sound you are trying to manipulate. You may find lowest distortion on FE does not result in best sound. I am not 100% sure lowest THD on FE will result in lowest THD in final product, but could be wrong. Perhaps Ilquam or others can comment. If you want t measure just FE, you can pull transformer and load FE with 10K resistor to ground and measure.

 

[lhquam]

Boys, how can I measure THD spectra of F6 FE? If I make output Rs symmetrical and measure the whole amp will it be enough?

I recently tried adding a 10 ohm pot between the source pins of the JFETs with the wiper to the transformer primary. Measuring the end-to-end THD, I could not detect any significant change with different wiper positions. My conclusion is that the FE distortion is so low compared to the output stage that source resistors make no difference other than to reduce the JFET current.