Output Transformer Specs for TwoStroke

[ArgStrat]

I am working on my own design for a TwoStroke style amp with a Blackface VibroChamp tremelo circuit. I have made a lot of drawings and acquired most of the parts to start building with a planned date sometime in the next month. While revising my layout I decided to take some time to evaluate the hook up of my OT, a Mojo15WH, and realized that it is considerably different than the Hammond that DH spec’d. The Hammond 125ESE has a two wire primary with a rating of 10,000 ohm or 5,000 ohm or 2,500 ohm to a variety of load impedances which are based on the input impedance. The Mojo has a 4 wire primary with a spec for each winding with respect to 0; 3,500 ohm or 4,000 ohm or 5,000 ohm. I also read DH’s spec saying an OT with a 2,000 ohm to 2,500 ohm primary. Having said all that my question is: will my Mojo15WH work with this circuit with the switching device?

[Robin]

I’m not sure what you mean by “switching device” but if you refer to this link: http://www.valvewizard.co.uk/se.html
you can see the formula for establishing the correct primary independence for a proper OT for your application.

[ArgStrat]

Thanks, Robin. By switching device I was referring to the impedance switch for the speakers. I am trying to read as much as I can to make an informed decision and I have been trying to find this link. I think I may just return the parts I bought and order what you spec’d.

[Author]

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