facepalm Yes.
Note to self, don't try to do smart stuff in the middle of the night when you should be sleeping.. Yet again.
OK I'll start a new topic on capacitive decoupling for all the main output-burners out here! ^_^
Might have fried the output of Axo
mackemint
#12
ndlopes
#13
Definitely something similar happened to my axo core. Very weak output with a lot of noise.
Right output is almost dead, left output has more signal but also more noise.
Axo was connected to an amp that was suddenly disconnected and reconnected,
in that moment a burst occurred and the main output was gone...
However, the headphone output seems to be working without noise.
Summarizing I'm very very sad..and since I got a bit lost in the electronics in this thread,
So what is the cheapest and safer way to use the headphone output as a line out?
Help, please.
keyman
#14
3.5mm (1/8") mini-jack is a headphone output. Use only for headphones (headphone jack is electrically biased at 1.65V.)
johannes
#15
So apparently IC4 (the line output driver) broke down due to a voltage spike. This causes IC3 (just behind the line out socket) to overheat (be careful not to burn your finger when you check this!), dropping the analog supply voltage and then the audio chip would not function anymore (but that seems not to be the case on your board).
This mod would remove power to IC4 and remove the DC bias from the headphone out and couple that into the line out socket:
step 1 : cut the power to IC4
step 2 : cut three tracks on the bottom side.
(blue are copper tracks on the bottom side, red are copper tracks on the top side)
step 3 : connect one wire and two capacitors:
For the capacitors I'd suggest 10 microfarad, 16V electrolytic types. More voltage rating does not hurt. 22uF or 47uF would also be good values, it only makes a difference for low-impedance loads.
step 4 : add two resistors to bias the capacitors properly
I suggest 10kiloOhm resistors, but anything between 2.2kOhm to 22kOhm would do the job fine.
This mod bypasses the ground loop break circuit. Ground loop noises are most likely when you power Axoloti Core by USB from the same PC that is also involved in the audio path somehow (like soundcard to the same mixerdesk...).
BTW: the 'S', 'T' and 'R' markings mean sleeve, tip and ring. The top row goes straight to the headphone, line-out and line-in jacks, the bottom row connects to the circuitry. This is to allow circuit hacks, like re-purposing the 1/4" jacks to footswitch or footpedal inputs, breaking out to dual mono jack inputs and outputs, or adding a relais for true bypass...
Control transfer failed: -7 - need a little bit of help
mackemint
#16
Hey bro,sorry for your loss. Till be using one of these:
Its cheap and will do the trick.
I tried out a few capacitor based configurations but without satisfying results.
Good luck!
ndlopes
#19
The hack proposed by @johannes.
Used 10k resistors and 1mF 35v Caps.
After all I have a big electronics store in my neighborhood.
Now I've a bit of digital noise (probably due to the USB connection) and it seems that the output is a bit lower...
But completely useful and stable. 
mackemint
#20
Hey @johannes, how'bout if one is feeling friskey and would like to attempt replacing the headphone amp IC? It seems this component (TPA6132A2) is available from a retailer near me..
johannes
#21
QFNs can be tricky. With a hot air soldering station and flux, this can work. Avoid a lot of solder on the center pad - if there is too much there, the component will float on the center pad, not making connections to the signal pads.
kausto
#22
I guess somewhere (on site/on forum in form of conspicuous sticky topic) should be a recommendation how to avoid this since it can happen easily.
mackemint
#23
I guess I'll have to see a friend about a hot air soldering gun then...
Before I do something possibly stupid,I guess its the QFNL IC in the image? It says IC4 but has the text "AIWI48JPDTY", which doesn't turn up any results when I octopart it..
harryt
#25
Hi Johannes,
I just got around to experimenting with my v1.1 Axoloti today. I love it! But it just broke. It seems to be behaving like others have described in this thread - low voltages and IC3 heating up.
Should I follow the procedure to bypass IC4?
Many thanks,
Harry
mackemint
#26
I replaced IC 4 with a new one. Not too hard, but required a hot air station and a magnifying glass.
Blindsmyth
#27
Hey there I got 2 boards now with the same sympoms, IC3 hot and red light blinking. Both boards had these failures after I fucked up something with the dc input.
@Johannes you think my boards have the failures described in this thread?
Since I'm struggling a lot with ground noises in my setup I really don't want to bypass the ground loop break circuit.
I guess replacing IC4 is then the best option? Would this be the right replacement part? https://www.aliexpress.com/item/IC-TPA6132A2RTER-TPA6132A2-TPS6132A2RTET-WFQFN-16-Original-authentic-and-new-Free-Shipping-IC/32699546195.html?spm=2114.01010208.3.9.Hm1h98&ws_ab_test=searchweb0_0,searchweb201602_2_10152_10065_10151_10068_10193_10194_10136_10137_10060_10155_10062_437_10154_10056_10055_10054_10059_303_100031_10099_10103_10102_10101_10096_10052_10053_10107_10050_10142_10051_10084_10083_10080_10082_10081_10177_10110_519_10111_10112_10113_10114_10180_10182_10184_10078_10079_10073_10186_10123_10189_142,searchweb201603_2,ppcSwitch_2&btsid=0669cbdb-3288-409f-9914-06182a77f321&algo_expid=b547535a-6146-41b6-91a8-3631930b549d-1&algo_pvid=b547535a-6146-41b6-91a8-3631930b549d
I could ask somebody at my local fablab to do the exchange for me.
mackemint
#28
Yes that looks like the one,with a hot soldering gun, a microscope and liquid flux its possible to do.
Audio output does not work
Blindsmyth
#29
Ok thx for the tip. Already talked to Johannes, he confirmed that it should be the right part.
srodillof
#30
Hello all! I have a question:
What can I do to use a single output (either jack or mini-jack) of the axoloti to work with headphones as well as stereo receivers, portable speakers, etc?
Just like an iPod works with any of those using a single mini-jack output.
terrible design. DC input kills ALL units. fuck me, just waisted 200 euros on TWO boards 