Speaker amp balanced transformer output?

[Doc B.]

Our recent development of a headphone amp with balanced outputs was interesting. Along with an expected improvement of soundstage I noticed an improvement in the bass - tighter and more punchy. I do not have a logical explanation for why.

So I thought what the heck, let's try it with the amps on the woofers of the main system. In stock configuration the Paramounts have the cold (black binding post) leg of the output transformer secondary connected to ground for safety. One can lift this ground connection and depending upon the output impedance configuration one can either tie the center tap created by series connection of the secondary windings to ground instead, or in the case where that tie point does not exist, one can create a virtual center tap on the secondary by connecting a 60 ohm resistor to each end of the secondary and connecting the other end of both resistors to ground. This will retain a safety path to ground in the exceptionally unlikely case there is ever a short created from primary to secondary in the OT - which is even more unlikely with a parafeed output transformer where the primary is usually isolated from B+ voltage by a cap - but PJ takes safety pretty seriously.

I think I hear tighter and punchier bass with this configuration. This makes no sense, I know. Neither does our 300B preamp having better bass than our other preamps that have the same output impedance and draw about the same current, and neither does our "accidental" power cord kit sounding better than the stock cord. I freely admit I have no idea why any of these things sounds better. However I would appreciate if someone would try this balanced output thing on a system with the capability for ample deep bass (not OBs or dinky little horns or stuff that is crossed over to a sub woofer) and report their results. Maybe I am just crazy.

[balancedtriode]

I am very interested in doing this to my Stereomour.
what parts would I need to do this and where would I need to connect the wires?
Any Info would be appreciated.
Thanks,
-Coltrane

[Doc B.]

You can connect the resistors at the output transformer secondary terminals, or at the speaker binding posts. The grounded end of the resistors can connect to the loose end of the wire that the black binding post was connected to before you removed it to do the balanced setup. I would strongly advise looking at the schematic and visualizing the lifting of the existing ground wire from the black binding post and how this will be connected so you understand what is changed with this mod before you tackle it.

[Paul Joppa]

Of course, the impedance switch kit that will be coming out shortly allows switching between balanced and unbalanced, as well as a choice of impedances.

[balancedtriode]

Ok, Cool.
Without writing anything in stone, what is a ETA of that kit?
I would be very Interested in it.
-Coltrane