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Re: That1580 mini mixer

Posted: Fri Oct 23, 2020 3:10 am
by AnalogJoe
weroflu wrote:
Mon Oct 19, 2020 8:00 am
c12,14.16 gone.

Metering will be done post unbalancing right before the 5k mixing resistors. Going with attiny84 somethings on each channel card, 10 leds, will try to emulate an lm3916 with the mcu. low current leds and peak metering should not be too much of a current draw. (led color render is messed up, it's supposed to show as 8 greens, 1 yellow, 1 red)

I'm hoping that those mini jacks (which are soldered to the motherboard) will squeak into the tins.

That's about it for the design I think. The rest is making it work and writing code.
Hopefuly OLED technollogy will die soon, OLED displays have their days numbered, my U1273A meter has an OLED display, I regret buying it every day, at first it lwas beautiful to look at, now its impossible to read because the display is so dark, it makes sense since it has organic materials which decay over time, I had to buy a new display from a Chinese dealer, it wasn't cheap, it cost me around $100 USD, I just wish I had the LCD version instead.... My point: avoid OLED https://en.wikipedia.org/wiki/OLED#Lifespan

Re: That1580 mini mixer

Posted: Sat Oct 24, 2020 10:17 am
by JR.
AnalogJoe wrote:
Fri Oct 23, 2020 3:10 am
weroflu wrote:
Mon Oct 19, 2020 8:00 am
c12,14.16 gone.

Metering will be done post unbalancing right before the 5k mixing resistors. Going with attiny84 somethings on each channel card, 10 leds, will try to emulate an lm3916 with the mcu. low current leds and peak metering should not be too much of a current draw. (led color render is messed up, it's supposed to show as 8 greens, 1 yellow, 1 red)

I'm hoping that those mini jacks (which are soldered to the motherboard) will squeak into the tins.

That's about it for the design I think. The rest is making it work and writing code.
Hopefuly OLED technollogy will die soon, OLED displays have their days numbered, my U1273A meter has an OLED display, I regret buying it every day, at first it lwas beautiful to look at, now its impossible to read because the display is so dark, it makes sense since it has organic materials which decay over time, I had to buy a new display from a Chinese dealer, it wasn't cheap, it cost me around $100 USD, I just wish I had the LCD version instead.... My point: avoid OLED https://en.wikipedia.org/wiki/OLED#Lifespan
not to feed the veer but IIRC OLED displays were supposed to be the next great display technology. That short life seems like a swing and a miss...

JR

Re: That1580 mini mixer

Posted: Sat Nov 21, 2020 5:37 am
by weroflu
Oled: Show me how I can use lcd in a smaller footprint than what I'm using now.

I managed to squeeze the 6th channel back in by offloading the p/s onto a mini card.

Getting close to a board run and then I saw the That 6261, hmmm.

It wouldn't be hard to add a master channel with gain/attenuation now. a pair of 1646/1606's after the summing and one 6261.
edit: i didn't look closely enough, the adc driver is not bypassable. Not sure if this is a good idea.

Re: That1580 mini mixer

Posted: Mon Dec 07, 2020 10:47 am
by weroflu
Boards ordered. First next step is just a physical dimension test on the jacks and edge connectors.

I caught one error, which might turn into a positive...

I rearranged the phantom blocking caps, which were previously 22uf - as I understand it this about the low end of what you want.
I can only fit 10uf now, well no I can Kludge in 22uf but not prettily and probably higher if I mash them.

Also realized that I never had .1u film caps in parallel in any of my past designs. This will be a challenge to squeeze in but I think it's possible on the next board run. Is it worth it? Wima, Kemet, any recommended brand?

Regarding these current 10uf blocking caps, I noticed the that 5171/1580 sample schematic does not include a T-bias 22k resistor as in the 1510/12 datasheet. Is this a simpler way to bring the corner rc frequency down lower without using a larger phantom blocking cap?

Re: That1580 mini mixer

Posted: Tue Dec 08, 2020 5:33 am
by mediatechnology
weroflu wrote:
Mon Dec 07, 2020 10:47 am
Boards ordered. First next step is just a physical dimension test on the jacks and edge connectors.

I caught one error, which might turn into a positive...

I rearranged the phantom blocking caps, which were previously 22uf - as I understand it this about the low end of what you want.
I can only fit 10uf now, well no I can Kludge in 22uf but not prettily and probably higher if I mash them.

Also realized that I never had .1u film caps in parallel in any of my past designs. This will be a challenge to squeeze in but I think it's possible on the next board run. Is it worth it? Wima, Kemet, any recommended brand?

Regarding these current 10uf blocking caps, I noticed the that 5171/1580 sample schematic does not include a T-bias 22k resistor as in the 1510/12 datasheet. Is this a simpler way to bring the corner rc frequency down lower without using a larger phantom blocking cap?
I would leave off the 0.1 uF films since you are space-constrained.

T-bias will raise the common mode impedance to reduce the effect of cap mismatch so it will improve LF common mode rejection. It won't lower the differential Fc. The best way to lower the differential cutoff frequency under your circumstance would be to raise the bias resistor values somewhat.

The downside to raising the bias resistor values is increased 1/f noise when the input is open circuit. Since open inputs should be muted I don't see this as a big penalty.

What are the values of your bias resistors?

Re: That1580 mini mixer

Posted: Wed Dec 09, 2020 12:13 pm
by weroflu
1.2k bias straight from the datasheet.

I don't have mute on this version.

Re: That1580 mini mixer

Posted: Wed Dec 09, 2020 12:38 pm
by mediatechnology
I calculate a differential mode 13 Hz cutoff with 5uF (2X 10uF in series) and 2400Ω (2X 1200Ω).

I would raise Rbias and continue to use the 10 uF.