Built a "Custom 500 Series Mixer"

[ip_dalie]

Hi Guys..

I’m planning to make a custom 500 series mixer

The ideas is:

- For tracking (pre - eq/comp - direct out)
- For mixing 8-16 channels (DAW insert)
- Summing 8-16 to 2
- Monitor & Headphone amp


So it’s basically 500racks plus Faders+Pans to Mix Bus.

In the schematic below,
- As a newbie I think I will lose -6 (THAT1256) at the balanced-unbalanced section,
- And I’m not sure about how much I lost and recover at the Fader-Pan section (ESP Project).
- The Unbalanced & the L/R Bus section, I took from DiyRe Colour Module schematic.



I really need help for some advice, or maybe if there is better idea

Thank you Guys!!

- Ip

 

[ruffrecords]

Nice project.

I am not sure what is going on with your input pad but the load it presents to the mic and the source it presents to the mic pre does vary somewhat. What are you trying to achieve here?

You will need a few more components around the THAT parts to make them work properly but I am sure you already know that from the data sheets.

Looks like you have 6dB in hand on the fader. 10dB is more 'normal'

The pan pot circuit is OK and inexpensive but the dual circuit will give slightly better noise performance (not a big deal)

Looks like you are using voltage summing. With op amps there really is no reason not to use virtual earth summing. I am not usre of the purpose of the 20KA dual pot in the summing section - is it just a level trim or is it supposed to be a master fader?

I notice you have no AUX sends or returns.

Cheers

Ian

 

[ip_dalie]

Nice project.

I am not sure what is going on with your input pad but the load it presents to the mic and the source it presents to the mic pre does vary somewhat. What are you trying to achieve here?

You will need a few more components around the THAT parts to make them work properly but I am sure you already know that from the data sheets.

Looks like you have 6dB in hand on the fader. 10dB is more 'normal'

The pan pot circuit is OK and inexpensive but the dual circuit will give slightly better noise performance (not a big deal)

Looks like you are using voltage summing. With op amps there really is no reason not to use virtual earth summing. I am not usre of the purpose of the 20KA dual pot in the summing section - is it just a level trim or is it supposed to be a master fader?

I notice you have no AUX sends or returns.

Cheers

Ian

Thanks Ian

- Yer, Im not sure about the pad just because some of my modules have no pad on it, I'm trying to crank the line level with the mic pre (from DAW). Or maybe not working like that?

- I got also idea to put this fader and pan schematic below (from s600). do you think it's better? and also is 22k for summing resistor ok? or maybe 47k?





- For the summing section, it's supposed to be single 10KA right?, yes it's for master fader, I tried to make another schematic below, I dont know which one is good for the master bus.



- Yes, no AUX and send return,



Cheers!!

- Ip

 

[ruffrecords]

Most modern mic pres have wide ranging gains so you probably need nothing more than a simple switched 20dB pad at the input which you can make with a couple of 680R and a 150R resistors.

The S600 fader/pan circuit looks fine to me. 22K bus reistors should also be fine.

I would not put the master fader in the feedback loop of the summing amp. Instead I would add the fader after the summing amp. You would probably need to add a buffer after it because the THAT device requires a low impedance drive.

Cheers

Ian

 

[ip_dalie]

Most modern mic pres have wide ranging gains so you probably need nothing more than a simple switched 20dB pad at the input which you can make with a couple of 680R and a 150R resistors.

The S600 fader/pan circuit looks fine to me. 22K bus reistors should also be fine.

I would not put the master fader in the feedback loop of the summing amp. Instead I would add the fader after the summing amp. You would probably need to add a buffer after it because the THAT device requires a low impedance drive.

Cheers

Ian

Thanks Ian for all the infos, it's help me a lot.

So I'll use 5532 virtual summing and then 5532 buffer and then balance them with 1646. Do you think it's gonna work like this schematic below? or maybe, do I need to put 10K resistor before the fader?

Cheers

Ip

 

[ruffrecords]

Looks good to me. I would couple the summing ap to the fader with a 100uF capacitor - you do not want to risk dc flowing in a fader.

Cheers

Ian

 

[ip_dalie]

Looks good to me. I would couple the summing ap to the fader with a 100uF capacitor - you do not want to risk dc flowing in a fader.

Cheers

Ian

Thanks Ian!

Schematic updated


Cheers

Ip

 

[Ricardus]

This would be a really cool project if we had a fader module and more universal metal-work, and we could really make a proper console.

I remember Jeff from CAPI teased a bunch of modules and buckets he was designing, a few years ago, so you could basically make any size (API style) console you wanted to, then it all disappeared.

I think the DIY space needs that.

 

[ip_dalie]

This would be a really cool project if we had a fader module and more universal hardware, and we could really make a proper console.

Hi Ricardus.
Yer, my built is basicaly on that concept, or maybe more like this -> VIAFADER
and, my design look like this (but is not finish yet )



Cheers

Ip

 

[ip_dalie]

Updated the whole schematic

Cheers

- Ip

 

[Harpo]

Thanks Ian!

Schematic updated
View attachment 112599

Cheers

Ipin

Ipin, maybe allow some remarks.
Inputs +/- of U5.1 are flipped. The opamps inverting input (-) is the summing node.
An additional cap (about 10uF) between wiper of VR3 and the junction of R14 and the non-inverting input of the +8.6dB fader buffer seems missing in order to keep U6.1 bias current from the fader.
I don't understand the use of R13, limiting the fader-range in between 0dB and -9.9dB in the ccw position.
Cheers
Harpo

 

[ip_dalie]

Inputs +/- of U5.1 are flipped. The opamps inverting input (-) is the summing node.

Thanks Harpo! Spot on
Do I need to put 10pf betwen the (-) input and the output the U5.1?

An additional cap (about 10uF) between wiper of VR3 and the junction of R14 and the non-inverting input of the +8.6dB fader buffer seems missing in order to keep U6.1 bias current from the fader.
I don't understand the use of R13, limiting the fader-range in between 0dB and -9.9dB in the ccw position.

- I don't know what I'm doing haha .
- The fader, buffer and the 1646 sections, I took it from DiyRe Colour Module schematic.
- Do you have another suggestion for that?


Cheers

- Ip

 

[Harpo]

Thanks Harpo! Spot on
Do I need to put 10pf betwen the (-) input and the output the U5.1?



- I don't know what I'm doing haha .
- The fader, buffer and the 1646 sections, I took it from DiyRe Colour Module schematic.
- Do you have another suggestion for that?


Cheers

- Ipin

If it helps better sleep, a 22pF..33pF compensation cap across the 22K feedback resistor will set a 329kHz...219kHz LPF.
A 10pF would have the -3dB cutoff point at 723kHz.

 

[Ricardus]

Hi Ricardus.
Yer, my built is basicaly on that concept, or maybe more like this -> VIAFADER
and, my design look like this (but is not finish yet )

View attachment 112603

Cheers

Ipin

Yes! Exactly!

And do you really have a 9098 preamp?

 

[ip_dalie]

If it helps better sleep, a 22pF..33pF compensation cap across the 22K feedback resistor will set a 329kHz...219kHz LPF.
A 10pF would have the -3dB cutoff point at 723kHz.

Thanks Harpo!
And do you think my master fader, buffer, and 1646 is gonna be okay as well?

Cheers

- Ip

 

[ip_dalie]

Yes! Exactly!

And do you really have a 9098 preamp?

Yer, I made a couple design of it, not trying it yet. Need to finish the Mixer first.
Based on Peter's Green and 9098 schematic, home etch, . I thought I sent you before

Cheers
- Ip

 

[Ricardus]

Yer, I made a couple design of it, not trying it yet. Need to finish the Mixer first.
Based on Peter's Green and 9098 schematic, home etch, . I thought I sent you before

Cheers
- Ipin

Oh. If we talked about the 9098 I forgot because I am old.

 

[Harpo]

Thanks Harpo!
And do you think my master fader, buffer, and 1646 is gonna be okay as well?

Cheers

- Ipin

I'd miss the output protection as shown in That 1646 datasheet pg.9 fig.8. Lots of a/d interfaces come with build in mic preamps and +48V phantom supply. If this would accidently be activated, this might/will blow your 1646. Just 4 clamping diodes for a better sleep. Imho the RF protection with the 2 inductors and 2 caps (going to shield/case, not to gnd/0V reference) isn't that essential.
As always ymmv.
Cheers
Harpo

 

[ip_dalie]

I'd miss the output protection as shown in That 1646 datasheet pg.9 fig.8. Lots of a/d interfaces come with build in mic preamps and +48V phantom supply. If this would accidently be activated, this might/will blow your 1646. Just 4 clamping diodes for a better sleep. Imho the RF protection with the 2 inductors and 2 caps (going to shield/case, not to gnd/0V reference) isn't that essential.
As always ymmv.
Cheers
Harpo

Thank you Harpo!!!

Yes! Just updated the schematic

Cheers

- Ip

 

[ip_dalie]

Updated the schematic