Grounding the 4ohm tap

[tyu]

Today we have a lot of tube amps output Transfourmer that are only 0-4-8 taps an no 16ohm taps, i have moved the ground from the 0 to the 4ohm tap . Then put the Speakers on the 0-8 ohm taps.There is a more open fuller sound,gives great sound on the Magnepans an Martinlogan i have, Is this a more push pull output?Have others done this,any info
Thanks for your time

[Globulator]

Depending on the schematic this will reduce the amount of global negative feedback.

Can't think of any other effect..

[Loren42]

Originally Posted by tyu

Today we have a lot of tube amps output Transfourmer that are only 0-4-8 taps an no 16ohm taps, i have moved the ground from the 0 to the 4ohm tap . Then put the Speakers on the 0-8 ohm taps.There is a more open fuller sound,gives great sound on the Magnepans an Martinlogan i have, Is this a more push pull output?Have others done this,any info
Thanks for your time

I, too, think that you have simply reduced the negative feedback and that is why is sounds different.

This reduces the amplifier's damping factor and possibly increases the susceptibility to the amp oscillating.

The other effect is that ground is now referenced as a virtual ground between the two speaker terminals, which has no audible effect at all.

[hidnplayr]

Originally Posted by Loren42

The other effect is that ground is now referenced as a virtual ground between the two speaker terminals, which has no audible effect at all.

That is not quite right, the 4 ohm tap is not the middle between 0 and 8 ohm.
It would be the middle tap between 0 and 16 ohm.
Calculate the voltages if you dont believe me

[DF96]

Ground is somewhere between the two speaker lines, but not half-way between.

Reducing the NFB will probably reduce the risk of oscillation, but may give a more lumpy frequency response and more distortion.

[tyu]

[Reducing the NFB will probably reduce the risk of oscillation,]



I have even ran the Amp with out any Ground an did not get any oscillation,
i get the less feedback well give more output,but the sound is great but the panels can eat power an Keep on trucking, I think that ARC output tube setup is Geart,why more dont do this can anyone Say??I dont buy the front end ARC thay love more an more parts,not my bag like the output setup,I have a pr of Dya MK3 setup as the ARC70.Just the output tubes.The Amps are full pentoid not UL.
Thanks for all an more input an info

[Frank Berry]

Less feedback will not give you more output. It will only increase the amplification.
The maximum output power of your amplifier will not change.

[Globulator]

Originally Posted by tyu

[Reducing the NFB will probably reduce the risk of oscillation,]



I have even ran the Amp with out any Ground an did not get any oscillation,
i get the less feedback well give more output,but the sound is great but the panels can eat power an Keep on trucking, I think that ARC output tube setup is Geart,why more dont do this can anyone Say??I dont buy the front end ARC thay love more an more parts,not my bag like the output setup,I have a pr of Dya MK3 setup as the ARC70.Just the output tubes.The Amps are full pentoid not UL.
Thanks for all an more input an info

I don't understand - the schematic you posted will only work properly with the 4ohm terminal grounded - else the push-pull feedback is asymmetrical (i.e. greater on one side than the other)...

I.e. in this case grounding the 0 tag side = faulty wiring.

[tyu]

Yes you are right The amp is a Jolida502a that i have ran with out ground,an now have the 4ohm tap grounded, i was not clear ,The MK3s are set up as the ARC 70 .
thank you