[sdiy] DIY Mixer - please help!

[Weber Paul Dhillon]

Transformer definitely add their own form of distortion or  
"colouration", as I like to refer to it -- and quality transformers  
will exhibit completely different characteristics than a Berringer  
isolation box.

But, it is a matter of taste and application -- Quality inductors are  
great in EQs too.  Last night I was mixing a project through a Manley  
Massive Passive that has hand-wound inductors and it sounds much  
smoother than my active filter based around a low distortion FET Op  
Amp (AD604).  But the active filter has its uses.

What kind of tools do you want in your sonic paintbox?

Try searching on DISCRETE  OP AMP designs.  Try this page: http://www.prodigy-pro.com/diy/index.php?topic=281

Someone also mentioned Forssell.  He is a great designer -- I have  
used his transformerLESS tube designs for classical recordings -- they  
are ultra-clean and have very high headroom: http://www.forsselltech.com/

Forssell help design this equipment as well: http://www.mil-media.com/  
-- look at the M2b.

Tape Op Magazine ran an article on a gentleman named Dan Garcia who  
just finished building a high quality mixer.  Here are some photos but  
I can't find the article online.  http://www.dangarcia.net/ 
photos.html  It was in the May/June 2009 edition and worth a read to  
understand his approach.

Colouration: Isn't this is what we are after in many cases with our  
synth modules.   One can find a lot of vanilla 4 pole VCFs in software  
emulation but nothing sounds like the real and non-linear 2040 or 3320  
or, more impressively, a discrete designs.  Where did I put that  
horrid 4136?

Paul Weber



On Sep 3, 2009, at 04:04 , Antti Huovilainen wrote:

> 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