• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

#26 pre amp

Really Sowter 9063 doesn't have two input coils it's a center taped....
Incorrect...
https://www.sowter.co.uk/specs/9063.php
Sowter says "Two chamber bobbin provides full geometric balance for the ultimate in noise rejection and phase splitting performance." so the schematic is correct.
I use these transformers in my line-drivers:

zeus-lineamp-vmos-pp-iptx-sowter9063-1x4-dn2535n5-optx-sp-gaped-1x1-front-1-800.jpg
 
Sowter says "Two chamber bobbin provides full geometric balance for the ultimate in noise rejection and phase splitting performance."
"Two chamber bobbin" is what the Sowter page says.
And please DON'T use a multi-meter / DVM to measure the DC resistances of the windings - that WILL magnetize the core!
"The map is not the territory."
 
primary is always CT
Yes, you are quite correct.

The primary signal is always across both windings, otherwise the output won't be symmetrical because each output is on a separate section.
The schematic you are referring to also does not show the sectioning... it is not a physical representation of the winding stackups.
I have been using the 9063s since 2006, and have a couple in a box at my feet which are just about to go into a new line-driver.

And yes, Happy New Year everyone. :)
 
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H
Ring of two type CCS? This is my general preference as well for bipolar transistors. In general I have avoided CCS in the audio path of my own equipment. I am experimenting a little with some of the IXYs devices - SY, Doug and a couple of others think very highly of these which has my curiousity piqued.

I was thinking perhaps I had a specific preference for bias approach but I think I might be almost close to agnostic. I use cathode bias with tubes like the 6J5/6SN7/6SL7 almost exclusively, fixed (grid) bias in power stages and with DHT types in general or and some high transconductance types like the 5842. I have also employed LED bias with 5842 and D3A with choke loads or tube based gyrators. I've found the LED bias sounds good in these applications sans CCS. Using high transconductance types with LED bias in particular means that you need to pay close attention to matching and target plate current vs supply voltage (since I don't currently use CCS).

Fixed bias seems to work really well with low transconductance dhts and results in reasonably predictable Ip which generally is not the case with higher transconductance types which need to be tweaked to achieve the desired operating point.

I guess there are about as many ways to do this as there are designers. :p
 
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15 years is a long time ago particularly for a quote. Since I made those comments I have moved on to cascode CCS typically with depletion mode mosfets and in low voltage applications JFETs. I also use cascode bipolar CCS with LEDs as references in some headphone amplifier and discrete op-amp designs.

Rod Coleman as always remains an excellent reference on all things CCS.
 
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