Cheap Surround sound buffer/level shifter

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JR.
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Re: Cheap Surround sound buffer/level shifter

Post by JR. » Mon Aug 03, 2020 9:44 pm

I had squirrels pop my personal transformer fuse before Katrina when I had my own transformer and drop. During Katrina I chased a squirrel out of my carport and up onto the cottonwood with the arcing high tension lines. Now I am sharing a transformer with multiple neighbors.

I suspect a squirrel could have been involved, they often are, but not obviously this time. I was ready to hit the shower and cold beer, but since the power was off I kept mowing my rain ditches for another half hour.

I'd say 15-20 minutes to first show up, and then another 20-30 minutes to inspect the entire branch for obvious tree branches or whatever. Who knows might have found some branches, from earlier storms... it took some effort and skill (and time) to replace the fuse on the end of a 50' long fiberglas pole. I've seen them do that in the middle of blowing rain storms so this was relatively easy.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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JR.
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Re: Cheap Surround sound buffer/level shifter

Post by JR. » Thu Aug 06, 2020 4:13 pm

Well the computer has stopped disappearing my designs... Now I am remembering how nice it was to have junior engineers and technicians to finish my projects for me..

I don't mind doing the first channel layout, but need 5 more identical channels. :oops:

The design issues are sorted, I contacted Hypex and they shared a spec sheet for the amplifier I had never seen before.

I.8k input impedance which seems low and +12.5dB total voltage gain also seems low, but these are intended for OEM use so they expect the packager to deal with it.

I found a decent 5V rail to rail op amp for around $0.80 or so. Only parts I need to buy are the op amps, some 1% resistors, and some electrolytic capacitors (that aren't 30 years old).

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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JR.
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Re: Cheap Surround sound buffer/level shifter

Post by JR. » Sun Aug 09, 2020 2:41 pm

Last night I had an epiphany while trying to layout this PCB design on my tiny normal (22" diagonal) computer monitor while surrounded by big screens... It only took me a few minutes this morning to get my old PC rig displaying at 44" :lol:

Still the same tired old version of Eagle layout software that crashes once a day or more... I have long ago figured out that a quick save and reboot preserves the design. 8-)

I have one channel almost perfected so the rest is just repetition.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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mediatechnology
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Re: Cheap Surround sound buffer/level shifter

Post by mediatechnology » Sun Aug 09, 2020 5:37 pm

JR - In the future for "one-offs" or small runs you might want to consider ExpressPCB. Their software is pretty bullet-proof and although you're locked into their production for the first run they'll provide Gerbers at NC with the order. Since you only need one board doing the first run with them won't be a hindrance.
https://ka-electronics.com

Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

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JR.
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Re: Cheap Surround sound buffer/level shifter

Post by JR. » Mon Aug 10, 2020 8:42 am

Thanks, but I am too old to learn another round of new secret handshakes. :lol:

IIRC Eagle has a free newer release that is limited to small PCBs. I am still using EAGLE-4.03, a seat purchased for my consulting work on a project a couple decades ago. I have kicked the tires and probably downloaded more than one free layout package over the decades, but nothing appealed to me enough to permanently lock into. I recall several years back, PCB houses and even parts distributors were trying to offer one stop shopping to capture customers.

I am pretty much finished with the hard part and now it is mostly repeating the first channel 5 more times which will go faster. I will likely use a cheap chinese PCB fab and get more boards than I need. .

JR

PS: In hindsight it would be slightly easier to layout individual channel boards and cobble together 6 of them, but then I'd need to bus power and common signal nodes... too late anyhow. :lol:
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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Re: Cheap Surround sound buffer/level shifter

Post by JR. » Wed Aug 12, 2020 5:00 pm

Finished the first pass layout... but I need to soak it in beer for a couple days... I put in extra parts I probably won't pop.

Since I am using a LTP for overload LED I can't be confident in threshold voltage for base so stuck some extra through holes resistors in the design because I have tons of different values still...

I made the LEDs smd & TH in case the SMD LEDS aren't visible enough.

After I get it finished I will share images.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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mediatechnology
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Re: Cheap Surround sound buffer/level shifter

Post by mediatechnology » Wed Aug 12, 2020 5:21 pm

I always like to walk away from a layout for a few days and then look at it again a second, third, fourth and a few more times after that with fresh eyes.
I've been very lucky having boards work on the first pass by being super-careful.
The only thing that usually nails me is the silkscreen component designators having a number swallowed by a via hole.
Those are easy to fix and don't keep me from selling the first pass layouts.

Did you breadboard the level winkys?

Soaking it in beer sounds like a very good idea...
https://ka-electronics.com

Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

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JR.
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Re: Cheap Surround sound buffer/level shifter

Post by JR. » Thu Aug 13, 2020 8:38 am

mediatechnology wrote:
Wed Aug 12, 2020 5:21 pm
I always like to walk away from a layout for a few days and then look at it again a second, third, fourth and a few more times after that with fresh eyes.
I've been very lucky having boards work on the first pass by being super-careful.
+1... It is so much easier these days with computer forward and back annotation.
The only thing that usually nails me is the silkscreen component designators having a number swallowed by a via hole.
Those are easy to fix and don't keep me from selling the first pass layouts.
I ran a kit business for years without parts designations screened on the PCBs. Those can be a PIA to find clean places for them all.
Did you breadboard the level winkys?
No but there are a bazillion of the basic circuit working out in the world. Same as FLS, only difference is I didn't include diodes and hold capacitors.The only novel part of this circuit is hanging another LTP off the common emitter of all the transistors to light a red overload LED... In hindsight this would have been a nice feature for the old Peavey FLS GEQs 8-) Of course with two base emitter junctions involved, the threshold voltage for this overload is difficult to precisely predict (thus the use of through hole resistors so I can use my full complement of TH 1/4W resistors in my back lab to dial this in.)

The voltage swing is small enough that I don't have to worry about transistor base-emitter junctions reverse zenering. Sampling diodes and hold capacitors would dump spiky current into the ground, so pass. I don't need the LEDs to be on solid or bright. In fact I can add a cap to the common emitter node to serve as a hold for the overload LED.. Adding a cap to that node will sharply cut off the green loudest per channel LEDs and hold on the red overload LED longer. I like that idea (but I like most of my ideas). :lol:
[update] done added 0.1uF that was easy...[/update]
Soaking it in beer sounds like a very good idea...
always a good idea, but usually a little later in the day... :lol:

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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JR.
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Re: Cheap Surround sound buffer/level shifter

Post by JR. » Fri Aug 14, 2020 8:37 am

My overnight design team has lobbied to add the diodes and hold caps, for a more solid blinky light display... I have the parts sitting around so it's not a big deal.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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Re: Cheap Surround sound buffer/level shifter

Post by JR. » Thu Aug 20, 2020 1:54 pm

I just ordered op amps and the few parts I don't already have.. I had to buy new electrolytic caps because all mine are several decades old.. :lol:

The opamps I will use are AD 8656 Pretty remarkable performance for a 5V process...

https://www.mouser.com/datasheet/2/609/ ... 502553.pdf

I need the low Z drive capability to drive the hypex 1.8k input z, and the rail to rail swing.

I only need two legs of 1.25v AC but in a single 5V rail not much breathing room.

JR
[update- parts arrived today but I still haven't released the PCB gerbers. Still getting 250 warnings but no errors from the crappy schematic capture software... The design rules check spits out errors on the smd LEDs but I blame the component build. If I cared I would rebuild the part but nah, not for a one off.

Maybe one more day cleaning up the gerbers. I notice that I didn't even name the PCB... I'm thinking maybe "plus ten" for 10dB gain[/update]
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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