Cap Coupled vs Direct Coupled

[LF240]

In the Sherwood, the transformers couple the signal from the last class A stage of the power amp to a push-pull pair of output transistors. From there, the speaker output also goes through an output capacitor, needed to block DC.

I'm probably being pedantic - sorry!

Not pedantic at all, and thanks for clarifying! After a look at the schematic I can see what you're saying.

 

[6.5CM]

I really find it funny how circuit designs largely abandoned in the 1930s enjoyed a rebirth in the early transistor days. I guess transformers were cheaper than transistors at one point.

Not pedantic at all, and thanks for clarifying! After a look at the schematic I can see what you're saying.

View attachment 2539843

My Allnic L3000 preamp is transformer coupled. Its output comes from transformers. The transformers are made of nickel, which is supposed to be a thing.

What the design provides is a linear and very low impedance output of 150 ohms. I attribute this to its unique and robust low frequency performance.

I would think my preamp and power arrangement is similar to whats on the Sherwood.

Depending on which power amp I use, Im either DC or transformer (tube) coupled at the amplifiers output.

 

[gadget73]

The expensive part is why I have always heard that since the 70's, the design has only been used by high end manufacturers like McIntosh. I assume they engineer circuitry around the transformer that minimize the frequency response problem. If you look at McIntosh's web site, under amplifiers, they really tout their "Unity Coupled Circuit Output Transformers" and their "Autoformers".

Mac tube iron at least is truly something extra special. Not only is it very well made, the basic design is different than most anything else. I know at least one other company made some unity coupled output transformers, don't remember who offhand (Lundhal??) , but its definitely not a common arrangement. Its a fair bit more complicated to wind and most just don't bother with it.

 

[JimEGR]

One of the more valuable threads I've read here on AK. Appreciate the discussion and the education.