F6 Amplifier

Member
Joined 2009
Paid Member
coming from ultra resolution of J2, it was another sound I had to get customer to....

Botte is right the medium area with the Jensen is similar to the F3 sound with a bit better bottom.

"For reasons unknown" I like the Edcor as an available xformer a bit more....:D

but it is really a matter of taste... Even I could change all day long and enjoy both sounds...:)
 
Official Court Jester
Joined 2003
Paid Member
:D
 

Attachments

  • SShot-F8.jpg
    SShot-F8.jpg
    55.1 KB · Views: 447
Interest in a phase inverting diy F6?

If yes, a theoretical schematic is attached. The following modifications are principally the re-wiring of the parent.
  • The parent output node is now Ground
  • The output node is now the parent Star Ground
  • Each channel in a stereo enclosure must have its independent power supply.
  • The phase notations of the Jensen's primary windings are reversed.
Will it work? Detriment or value?
Brgds
 

Attachments

  • PhaseInvertdiyF6.pdf
    34.1 KB · Views: 141
With transformer coupling there is no reason that you cannot float the power supplies, assuming that the feedback is correctly phased and at the correct level.
OTOH, if you are going to float the power supplies why not implement a circlotron? You can even dispense with coupling transformers if you follow the path chosen by Rothacher http://www.diyaudio.com/forums/pass-labs/130810-amazing-fet-circlotron-mike-rothacher.html.

If yes, a theoretical schematic is attached. The following modifications are principally the re-wiring of the parent.
  • The parent output node is now Ground
  • The output node is now the parent Star Ground
  • Each channel in a stereo enclosure must have its independent power supply.
  • The phase notations of the Jensen's primary windings are reversed.
Will it work? Detriment or value?
Brgds
 
If yes, a theoretical schematic is attached. The following modifications are principally the re-wiring of the parent.
  • The parent output node is now Ground
  • The output node is now the parent Star Ground
  • Each channel in a stereo enclosure must have its independent power supply.
  • The phase notations of the Jensen's primary windings are reversed.
Will it work? Detriment or value?
Brgds
I did a double phase inversion; once at the primary winding of the Jensen [to implement feedback], and a second at the new output node. I am afraid the schematic in the preceeding post still shows a non-inverting diyF6; like the parent.

Will this mod and its parent perform the same? Is there a practical advantage to this modification over the parent?
 
With transformer coupling there is no reason that you cannot float the power supplies, assuming that the feedback is correctly phased and at the correct level.
OTOH, if you are going to float the power supplies why not implement a circlotron? You can even dispense with coupling transformers if you follow the path chosen by Rothacher http://www.diyaudio.com/forums/pass-labs/130810-amazing-fet-circlotron-mike-rothacher.html.
Thanks lhquam for your clarification and link. I recall you doing sims with Teaser-6 as a circlotron. I'll look again at Rothacher's paper. Brgds.
 
Member
Joined 2009
Paid Member
some news from Frankenstein 6....:)

very different pictures, may explain a bit the different character of sound Jensen versus Edcor with my build ...first picture Jensen, second Edcor...

I have to play with the two pots over the two secondaries..... 500R are a good starting point to mistune the distortion ......:D ?
 

Attachments

  • Jensen left 1W 7 Ohm.jpg
    Jensen left 1W 7 Ohm.jpg
    89 KB · Views: 418
  • Edcor left 1W 7 Ohm.jpg
    Edcor left 1W 7 Ohm.jpg
    70.1 KB · Views: 413
Last edited:
Edcor looks good to me, but if you can tune out some of the third on the Jensen, you are sitting pretty, I think. I guess that you will probably obly be able to add second, but you never know. Does this show that the Jensen's secondaries are more balanced. This assuming you just swapped the trafos.
 
Member
Joined 2009
Paid Member
Edcor looks good to me, but if you can tune out some of the third on the Jensen, you are sitting pretty, I think. I guess that you will probably obly be able to add second, but you never know. Does this show that the Jensen's secondaries are more balanced. This assuming you just swapped the trafos.

yes I just swaped the trafos...same SS side. But of course the data of the Xformers are different.

I will try some more feedback on the Edcors and when I trim the Jensens to have about 12db more k2 over the k3 I have a THD of 0,086%, unfortunately!