Arduino code sources?

It's part of why this ng is valuable to me even though it contains, to my mind, a bunch of assholes who have bad political opinions. I can use it to get my own bad engineering ideas broken. Great! Bad engineering ideas at least should be broken at the outset. Saves time that way. Lots of people here happy to do it!

When I left Lockheed Martin (a decade ago, give or take), the group was about to consolidate their FPGA (VHDL) engineers into their software group. Scary indeed! Scary place, all around.

We knew that you weren't here for the usual reasons, for instance to be friendly or helpful.

Cheers

Phil Hobbs

I've been helpful plenty of times, likely not to you but that's the way it goes.

Sucking up isn't my department, though, which does tend to irritate people who expect it.

PS: you really gotta let this condescending-sarcastic-Internet-man act go, Dr. Phil. it's not becoming of a doctor. it's not a good look for u.

Background:

My Altoids audio mixer [1] is in the middle of a makeover. The new iso transformer front end's already finished and sounds heavenly. New components made my circuit outgrow the tiny Altoids tin, so now everything's housed in a small Bud box. The new circuit utilizes a TEA2025 stereo audio amplifier [2], among other things. That beast can output up to 1.5 A, which far exceeds the capabilities of the TLE2426 "rail splitter" [3] that ultimately powers the new circuit. So the "rail splitter" will drive a BUF634A buffer [4] instead, which can supply up to 250 mA.

Spot the app note error:

My original intention was to use app notes to cobble the buffer on to the output of the "rail splitter," easy peasy. You inspired me to spend a little bit more time to look deeper into those app notes. Any wisdom that you, or others, can impart on my quest to "spot the app note error" is appreciated.

Note.

1. formatting link
2. formatting link
3. formatting link
4. formatting link

Thank you, 73,

--
Don Kuenz KB7RPU 
There was a young lady named Bright Whose speed was far faster than light; 
She set out one day In a relative way And returned on the previous night.

On 6/4/19 12:03 PM, Don Kuenz wrote:> Phil Hobbs wrote: > > > >> I taught myself circuit design largely by reading app notes, assuming >> that all the circuits were junk, and figuring out why. (Some of them >> are okay, of course, but you can always think about input protection and >> so forth.) > > Background: > > My Altoids audio mixer [1] is in the middle of a makeover. The new iso > transformer front end's already finished and sounds heavenly. New > components made my circuit outgrow the tiny Altoids tin, so now > everything's housed in a small Bud box. The new circuit utilizes a > TEA2025 stereo audio amplifier [2], among other things. That beast can > output up to 1.5 A, which far exceeds the capabilities of the TLE2426 > "rail splitter" [3] that ultimately powers the new circuit. So the "rail > splitter" will drive a BUF634A buffer [4] instead, which can supply up > to 250 mA. > > > Spot the app note error: > > My original intention was to use app notes to cobble the buffer on to > the output of the "rail splitter," easy peasy. You inspired me to spend > a little bit more time to look deeper into those app notes. Any wisdom > that you, or others, can impart on my quest to "spot the app note error" > is appreciated. > > Note. > > 1.

> 2. > 3. > 4. > > Thank you, 73, >

One of the usual appnote sins is to use gold-plated parts (their own, naturally). This is one of those--you're using a $10 BUF634 and a $2 TLE2426 instead of a $1 TCA0372 and two resistors. (See George's thread.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

why does an audio mixer need 1.5A of available output current?

The mixer opamps are on a daughterboard in order to facilitate experimentation. You convinced me that the power circuit also deserves its own daughterboard. That way, those two expensive parts can go right back into inventory if they offer little, if any, improvement.

73,

--
Don Kuenz, KB7RPU

It morphed into a mixer-amp. All will be revealed in the upcoming webpage.

Thank you, 73,

--
Don Kuenz KB7RPU 
There was a young lady named Bright Whose speed was far faster than light; 
She set out one day In a relative way And returned on the previous night.

The AMP portion should be BTL, that way there'd be no rail-splitter mid-supply ground current.

--
 Thanks, 
    - Win

The TEA2025 drives two separate stereo speakers, a left and a right.

Thank you, 73,

--
Don Kuenz KB7RPU 
There was a young lady named Bright Whose speed was far faster than light; 
She set out one day In a relative way And returned on the previous night.

The TEA2025 drives two separate stereo speakers, a left and a right.

BTW, 1.5A is the maximum current output by the TEA2025. For this application the speakers need less than one tenth of that value, but they also need a little more than the 20mA available from a standalone TLE2426.

Thank you, 73,

--
Don Kuenz KB7RPU 
There was a young lady named Bright Whose speed was far faster than light; 
She set out one day In a relative way And returned on the previous night.

Stereo, yes. I'm suggesting you use a more capable amplifier, one with complementary Bridge-Tied-Load outputs. There is no "ground" current. Two mono parts would be fine, but these are also available in stereo versions. The positive current from one output goes to the negative output of its BTL pair.

--
 Thanks, 
    - Win

In bridged mode the TEA2025 can only drive a single speaker. It takes two TEA2025s, each in bridged mode, to drive drive stereo speakers. Either that or find a more capable amp. It seems that the amp also deserves its own daughterboard. My quick and dirty solution grows more elegant by the hour. It also becomes more interesting.

Thank you, 73,

--
Don Kuenz KB7RPU 
There was a young lady named Bright Whose speed was far faster than light; 
She set out one day In a relative way And returned on the previous night.

If the line-level output is to be AC-coupled there should probably be a

50-100k load resistor and maybe small value cap, 100-470p, in parallel after the coupling cap, ideally right near the output jack. And probably a ~1k resistor in series with the coupling cap, too.

If it's to drive a significant length of cable the impedance looking back into the output terminals of the op-amp at the audio frequencies of interest should be well-defined.

If it's to become a mixer/power amp with a power output stage the output network would be different depending on the power amp chip's characteristics. like say a Zobel network in shunt and a small VHF-suppression inductor in series in the case of a linear power amp driving speakers.

In parallel to ground, rather

Or across the BTL load, if that was adopted.

There must be somebody on eBay or AliExpress selling a small PCB with a stereo BTL amp.

There are certainly plenty of blokes selling larger PCB versions, and I am a sucker for buying various high-power class-D versions. I imagine modifying them for DC operation, using them to run big Peltier coolers, etc. Or maybe I just admire their fancy heatsinks, and in some cases towering fan assemblies. Filling boxes with an impressive assortment.

--
 Thanks, 
    - Win

BITD BTL meant "bridge transformerless". When did that change?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com