Simple Neve Summing "Mixer" Design

[XAXAU]

I´m now thinking I´m better off ditching the input trafos and get a 2-ACA-BO instead. I don´t know how to make that happen in regard to the huge difference in bus R´s. If the Neve´s are 600 ish the API are 47K (as per Jeff Steiger).

I do have 2x DB25 summers from Ian so I might be able to split the inputs into 2 different DB25 summing PCB´s at their respective output (this way I´ll only have 8 input channels which isn´t a problem for me). Or is it stupid to have both circuits active at the same time and only use one? Will one circuit interfere with the other through ground? Is it possible to use the Neve´s bus R´s and just hang a 47K on the inputs of the 2-ACA-BO?

I´d love to be able be able to stack them as well. The ultimate configuration is to be able to run both circuits in series and change order of them plus do parallel but this is major clueless territory for me. I´d love to learn though!  ;D

Oh and a happy new year to all DIY heads!

 

[XAXAU]

Screw it, I´m just gonna build the 2x EZ1290´s and "see" how it sounds on its own! I see original dual 1073´s for $10-15k on eBay so there must be some serious mojo in this Neve circuit!  8)

 

[XAXAU]

[quote author=ruffrecords]You have to load the input transformer with close to 600 ohms[/quote]
Been thinking about this. The VTB9045 has a 1200ohm input impedance in series and 300ohm in parallel. Why 600ohms?

Also, I´ve seen mods to the 1290 that switches the primaries between series and parallel. How will this affect the sound for mic duties and summing duties? Is it a useful mod to have done?

 

[ruffrecords]

Been thinking about this. The VTB9045 has a 1200ohm input impedance in series and 300ohm in parallel. Why 600ohms?

Also, I´ve seen mods to the 1290 that switches the primaries between series and parallel. How will this affect the sound for mic duties and summing duties? Is it a useful mod to have done?

You do not have to load it with 600 ohms. Most mic transformers preamps are designed to present a load of around 1200 ohms which is fine for mics from 150 ohms to 600  ohms. The 300 ohm strapping gives another 6dB of gain and is intended for old fashioned 50 ohm mics, typically ribbons.

Cheers

Ian

 

[kambo]

off topic to your mixer plans, but if u have time and budget, i would go with
Ian's tube mixer. its super well documented!
i tried/used summing mixer on 8-mono ch in past, and was better than mixing ITB, but it wasnt wooooow!
(some may argue the other way, may be depends on what u do)
currently i am mixing ITB, and i am purposely clipping the DAW's master output... and i am totally
skipping the separate mastering session!
i like it way better than passive summing+mic_pre... but, it may not suit ur needs!

but, once u start driving 8 tube stages with nice 2nd harmonics, than its becoming woooooow!
i built similar circuit design to Ian's (P2P) for a friend, and it was pretty sick!
now, i am still building my tube mixer, with some mods etc(recall, vst connection etc)... no EQ!

 

[XAXAU]

You do not have to load it with 600 ohms. Most mic transformers preamps are designed to present a load of around 1200 ohms which is fine for mics from 150 ohms to 600  ohms. The 300 ohm strapping gives another 6dB of gain and is intended for old fashioned 50 ohm mics, typically ribbons.

Cheers

Ian

Thanks Ian! is it true that the frequency response changes as well?

off topic to your mixer plans, but if u have time and budget, i would go with
Ian's tube mixer. its super well documented!
i tried/used summing mixer on 8-mono ch in past, and was better than mixing ITB, but it wasnt wooooow!
(some may argue the other way, may be depends on what u do)
currently i am mixing ITB, and i am purposely clipping the DAW's master output... and i am totally
skipping the separate mastering session!
i like it way better than passive summing+mic_pre... but, it may not suit ur needs!

but, once u start driving 8 tube stages with nice 2nd harmonics, than its becoming woooooow!
i built similar circuit design to Ian's (P2P) for a friend, and it was pretty sick!
now, i am still building my tube mixer, with some mods etc(recall, vst connection etc)... no EQ!

Hey kambo!

I´ve read up on Ian´s tube mixer and it seems amazing! I might do a TLA colour box further on down the line!