[sdiy] DIY Mixer - please help!

[Antti Huovilainen]

On Wed, 2 Sep 2009, Paul Dhillon Weber wrote:

> Often designers used output transformers to achieve greater level and 
> headroom without having to add additional, phase inducing and noisy amp 
> stages.

Transformers actually have far worse phase problems than amplifier stages. 
So much so that interstage transformers can't usually be used inside 
feedback loop which is part of the reason they fell out of favor in tube 
circuits when lower THD amount required using feedback.

> Think about your favourite THICK recordings from the 70s.  That's the 
> sound of transformers.

As much or even more likely to be due to distorting transistor circuitry. 
Vintage designs using discrete components aren't exactly what you'd call 
low distortion these days. 0.1% THD was considered good back then and in 
simulation many circuits produce even more distortion. As for opamp 
designs, one word should be enough: 741.

I once tried to measure distortion in a cheapo behringer DI isolation 
transformer. We had problems getting enough signal to produce any 
measurable distortion in FFT view.

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova