That1580 mini mixer
Posted: Thu Apr 20, 2017 2:46 am
Hello:
I have been noobing on a diy 6x2 THAT1580/1510 mini altoids tin sized mini mixer. I'm not sure whether to split this up into two threads since I keep waffling between which one I want to finish.
specs:
-fit everything into altoids tin
-6 mic preamps/ 3.5mm jacks
-stereo summing, unbalanced output interfacing with 5k-20kOhm portable recorders/adc.
-LCR pan
-phantom power
-phase reverse
-modular cards
-1510 based physical switched gain
-1580 based bluetooth>>rfduino gain control
What's working:
That1510 mic pre cards
LT8330/LT3012 phantom power card
2 x LTC3265 +-15V rail card
backplane
rfduino card
(P/S card for the 1580 has everything on board, P/S for the 1510 is 3 smaller boards)
P/S card for the 1580/5171:
LTM8049 micromodule dc converter >> +-17V
TPS7A4701 regulator >> +15V
LT3015-15 >>-15V
LT8330/LT3012>>P48
LT1763-3.3>>3.3V logic
(noise issues aside, it works. needs filtering and grounding work, but that's tabled for now)
Not working:
1580-/5171 preamp card. It's passing signal but distorts too easily. DC offset coming off the 1580 is about -.5V, trying to track down problem with the servo section?
Summing card schematic was wrong, fixed it and most likely a trivial fix but for now not working. I'm using a barebones arduino sketch to load 30db of gain on startup since I don't have spi variable gain control/interface working yet.
https://1580mixer.shutterfly.com/pictures/8
The first version was THAT1510 based. I got very close to finishing it, but I didn't think through the gain switch well enough. The only pots available were alpha 9mm-sized and that created some physical constraint headaches (more later) and the lack of exact channel matching led me to table that version and try to get a 1580/5171 version working.
All cards are modular: backplane, preamp cards, summing card, p/s card, rfduino breakout board card (1571 version only).
I think I solved how to make the 1510 gain switch work (fit) with a combination of the grayhill 75ap36-01-1-10n screwdriver actuated switch
(http://eu.mouser.com/ProductDetail/Gray ... DzgrKUYw==) and a mini slide switch.
screwdriver actuated for two reasons: there is no room for fingers to get around a knob with 1.5mm clearance on either side, and I thought it would be more compact keeping as many controls inside the box as possible. 10 way switch for 5db gain increments on the preamp, then a 5 way miniature slide switch for post gain 1db increment attenuation. Apem makes a mini slider that I think will fit.
Phantom, phase, and pan are all on mini slide switches. Phantom and pan are not ideal since the switches are non-shorting, but I can live with this. Similar issue with the input jacks being 3.5mm and phantom, need to be careful not to hotplug.
I am aware that since I have zero design experience that the 1580 version could very well just not work due to noise issues, or other unforeseen problems. Mixed signal routing is many levels over my paygrade, but signal passed, and gain registers were set so I'll keep plugging away on it.
Current problems to tackle on the 1580 mixer are DC offset, distorted signal with higher input level, some high frequency noise even when using two batteries for supply rails bypassing the switchmode p/s, some motorboating from the rfduino card, fix summing card (new board arrival this week), then start chipping away at all the noise issues and bluetooth interface. I originally planned for +-15V rails, but this will likely change soon since it's unnecessary when interfacing with prosumer unbalanced line level gear. Probably will tone it down to something like +-8 or 10.
I have been noobing on a diy 6x2 THAT1580/1510 mini altoids tin sized mini mixer. I'm not sure whether to split this up into two threads since I keep waffling between which one I want to finish.
specs:
-fit everything into altoids tin
-6 mic preamps/ 3.5mm jacks
-stereo summing, unbalanced output interfacing with 5k-20kOhm portable recorders/adc.
-LCR pan
-phantom power
-phase reverse
-modular cards
-1510 based physical switched gain
-1580 based bluetooth>>rfduino gain control
What's working:
That1510 mic pre cards
LT8330/LT3012 phantom power card
2 x LTC3265 +-15V rail card
backplane
rfduino card
(P/S card for the 1580 has everything on board, P/S for the 1510 is 3 smaller boards)
P/S card for the 1580/5171:
LTM8049 micromodule dc converter >> +-17V
TPS7A4701 regulator >> +15V
LT3015-15 >>-15V
LT8330/LT3012>>P48
LT1763-3.3>>3.3V logic
(noise issues aside, it works. needs filtering and grounding work, but that's tabled for now)
Not working:
1580-/5171 preamp card. It's passing signal but distorts too easily. DC offset coming off the 1580 is about -.5V, trying to track down problem with the servo section?
Summing card schematic was wrong, fixed it and most likely a trivial fix but for now not working. I'm using a barebones arduino sketch to load 30db of gain on startup since I don't have spi variable gain control/interface working yet.
https://1580mixer.shutterfly.com/pictures/8
The first version was THAT1510 based. I got very close to finishing it, but I didn't think through the gain switch well enough. The only pots available were alpha 9mm-sized and that created some physical constraint headaches (more later) and the lack of exact channel matching led me to table that version and try to get a 1580/5171 version working.
All cards are modular: backplane, preamp cards, summing card, p/s card, rfduino breakout board card (1571 version only).
I think I solved how to make the 1510 gain switch work (fit) with a combination of the grayhill 75ap36-01-1-10n screwdriver actuated switch
(http://eu.mouser.com/ProductDetail/Gray ... DzgrKUYw==) and a mini slide switch.
screwdriver actuated for two reasons: there is no room for fingers to get around a knob with 1.5mm clearance on either side, and I thought it would be more compact keeping as many controls inside the box as possible. 10 way switch for 5db gain increments on the preamp, then a 5 way miniature slide switch for post gain 1db increment attenuation. Apem makes a mini slider that I think will fit.
Phantom, phase, and pan are all on mini slide switches. Phantom and pan are not ideal since the switches are non-shorting, but I can live with this. Similar issue with the input jacks being 3.5mm and phantom, need to be careful not to hotplug.
I am aware that since I have zero design experience that the 1580 version could very well just not work due to noise issues, or other unforeseen problems. Mixed signal routing is many levels over my paygrade, but signal passed, and gain registers were set so I'll keep plugging away on it.
Current problems to tackle on the 1580 mixer are DC offset, distorted signal with higher input level, some high frequency noise even when using two batteries for supply rails bypassing the switchmode p/s, some motorboating from the rfduino card, fix summing card (new board arrival this week), then start chipping away at all the noise issues and bluetooth interface. I originally planned for +-15V rails, but this will likely change soon since it's unnecessary when interfacing with prosumer unbalanced line level gear. Probably will tone it down to something like +-8 or 10.