AC97 vs HD-audio computer case frontpanel audio: I feel clueless - Page 1
Forum section: electronics / projects

author: Whales
author_rank: Super Contributor
timestamp: November 30, 2023, 04:48:04 am
content: Context: Frontpanel audio on PCs has two standards.AC97 is the older standard. Audio is sent to the case front 3.5mm female jacks. If nothing is plugged in then the normally-closed switches send the audio back to the rear of the PC:(Source: Intel Front Panel IO connectivity design guide, Version 1.3)HD audio is the newer standard that came out in 2004. It detects jack insertion using normally-open isolated switches (the small rectangles are plastic blocks/insulators).(Source: Intel Front Panel IO connectivity design guide, Version 1.3)It's a pain to find 3.5mm female jacks with these HD-audio style isolated switchesIt looks like 99% of the parts on LCSC use the AC97 style switch or something similar (normally-closed non-isolated).Neither LCSC or Digikey have a way of filtering for just isolated-switch style jacks.I had to open and review most of 100 datasheets to find one(LCSC specific rant): Garbage datasheets for many of their jacksTake thePJ-343Kwhich I tried to use:Above 100% of the information provided. Now try and make a footprint for it. I'll wait and see if you can spot what vital information is missing.Many of the other jacks I looked at have similar datasheet problems. XKB has no website that I could find or way of contacting them (possibly XKB is a westernised version of their name?). Some of the other companies' products I looked at are the same."Ah", but I thought, "I could use the footprint that LCSC provides for their EasyEDA product!"It turns out that this footprint is complete garbage. It's not even a mirror image or a single pin being off, most of them are completely wrong:So.. time to get my vernier calipers out, a cut 3.5mm male plug and a multimeter. Then respin the board. Because I think that will be less pain than looking for new HD audio jacks again.Surely I'm doing something wrong hereIt can't be this hard, can it?Why is the market dominated by AC97-style switched parts? HD audio is a standard from 2004 and my current case has "HD audio" proudly printed in white on the plug -- or are they lying?How do those front panel cables that let you choose between HD audio and AC97 work? They have two connectors on the end. These two standards shouldn't be electrically compatible as far as I can tell.

author: HwAoRrDk
author_rank: Super Contributor
timestamp: November 30, 2023, 05:38:37 am
content: Quote from: Whales on November 30, 2023, 04:48:04 amhttps://www.helloxkb.com/Home/Goods/goodsInfo/id/27035Not sure how you didn't find their website, it's literally the second result I get on Google when searching for "xkb connectivity".XKB are quite good in that they freely offer 3D models without keeping them behind a form, or offloading to a third-party site that requires an account.

author: ArdWar
author_rank: Frequent Contributor
timestamp: November 30, 2023, 05:39:22 am
content: Quote from: Whales on November 30, 2023, 04:48:04 amOf course. Most standalone and non-PC products use "AC'97" style detection, if they use any detection at all. "HD audio"-style is the odd one out as far as common usage goes.Quote from: Whales on November 30, 2023, 04:48:04 amWith dual detection jacks.

author: Whales
author_rank: Super Contributor
timestamp: November 30, 2023, 05:50:10 am
content: Thankyou both so muchQuote from: HwAoRrDk on November 30, 2023, 05:38:37 amHmm, it looks like it's a search engine problem. It shows up in Google but not in Duckduckgo.https://duckduckgo.com/?t=ffab&q=XKB+connectivity&ia=web

author: Whales
author_rank: Super Contributor
timestamp: November 30, 2023, 05:59:01 am
content: I'm still struggling to find a pinout on their website. They offer a lot of different (auto-generated?) versions of the docs, so I'll keep trying to check through them all.Pin numbers are not hidden in the 3d .step are they?

author: HwAoRrDk
author_rank: Super Contributor
timestamp: November 30, 2023, 01:16:40 pm
content: Quote from: Whales on November 30, 2023, 05:50:10 amHmm, weird. But if you search for "xkb connectivity website", their .cn website comes up first.BTW, their website address was staring you in the face all along. If you'd looked more closely at the datasheet linked on the LCSC website, you'd have seen the website addresses in small print right at the bottom of the page.

author: HwAoRrDk
author_rank: Super Contributor
timestamp: November 30, 2023, 01:38:37 pm
content: Quote from: Whales on November 30, 2023, 05:59:01 amThis document linked on the product page has pin-outs for 3 and 4 pole versions:https://www.helloxkb.com/public/images/pdf/PJ-343K-.pdfBut they are an embedded image with only Chinese text. I ran the 4-pole image through Google Translate - see attachment. Apologies for the enormous size, I had to make it that large to convince Google Translate not to make the translated text overlay un-readably small.

author: Whales
author_rank: Super Contributor
timestamp: November 30, 2023, 11:21:22 pm
content: Thanks HwAoRrDk, but that only describes the internal pins (how it mates with a male TRS). What I really need is a picture of the bottom pins of the part with labels as to what pin is what (and preferably a recommended footprint too if they've already made one, but that's just a nice-to-have).EDIT:I'll try and chat with the manufacturer and see if they can help.Quote from: HwAoRrDk on November 30, 2023, 01:16:40 pmUmm... *checks excuses list* they put too much ink on their stamp and my PDF viewer has high humidity.

author: wraper
author_rank: Unknown
timestamp: November 30, 2023, 11:28:23 pm
content: Quote from: HwAoRrDk on November 30, 2023, 05:38:37 amQuality however sucks. The only thing I found of good quality were pin headers. Micro USB connectors, TACT and micro switches I bought were subpar.

author: Whales
author_rank: Super Contributor
timestamp: November 30, 2023, 11:30:05 pm
content: Quote from: wraper on November 30, 2023, 11:28:23 pmWhat were the failures you experienced? Connectors losing friction after few cycles, micro switches becoming intermittent before spec, ?

author: wraper
author_rank: Unknown
timestamp: December 01, 2023, 12:00:26 am
content: Quote from: Whales on November 30, 2023, 11:30:05 pmMicro USB connectors for example had slightly wrong dimensions so most of (good quality) cables were very hard to insert for the first time and still too tight afterwards. Also barely any gold plating on the pins, almost no golden tint. I bought significantly cheaper "Jing Extension of the Electronic Co." connectors from LCSC and they were with proper dimensions and had much better gold plating. I also remembered that full size USB-B from XKB was an utter trash. Again barely any gold plating and ground (shell) spring contacts were not springy at all, got bent outwards after the first plug insertion and no longer made a good contact (many cheap Chinese USB-B connectors are like this). Again Jing Extension was much better and with shell made of springy steel as it should be and did cost even less. On microswitches with lever it interferes with rectangular bumps half way through (bumps located next to the plastic actuator on both sides). Although switch got activated, lever gets bent with increased force rather than going with normal force all of the way down. Good switches have those bumps too but not nearly as tall. I guess it's to protect actuator being pushed inside too far but dimensions were plain wrong. Don't exactly remember what was wrong with TACT switches, but they were the least bad I think.

author: Whales
author_rank: Super Contributor
timestamp: December 08, 2023, 06:49:05 am
content: UpdateI emailed XKB a week ago and have received no reply.LCSC contacted me to say they have reported the bad EasyEDA footprint to their team and it will get fixed. For my other problems they recommended I contact XKB and linked me to their website.I suspect I'm not the target audience of XKB. Most of their profits probably come from domestic Chinese manufacturers, not foreign engineers. Perhaps they respond faster/better if I give them a domestic phone number or QQ handle, but I have neither of those (and would prefer to just change parts instead).I ended up reverse engineering the pinout. The board is now working but the other jack in my design appears to be a nonstandard long TRRS type, so I have to redesign it all anyway.It's a shame, the compliant 3d printed mechanism I made for activating two jack-presence-detect switches was fun:(Screw it, maybe I should use simpler jacks and do more of my own external jack-presence-detect switching mechanismsThat would solve my headaches finding the right parts.)

author: HwAoRrDk
author_rank: Super Contributor
timestamp: December 08, 2023, 10:25:24 am
content: That's a pretty neat idea.Although, I would be concerned that if one of the slide switches ever got stiff, the bar would get cockeyed and jam up.Could you not have used a single DPST/DPDT switch? I'm sure I've seen similar small slide switches with that configuration.

author: Whales
author_rank: Super Contributor
timestamp: December 08, 2023, 10:50:06 am
content: Those two switchesare very light to activate (50g ~= 5 milli-newtons) and their particular geometry allows my plastic bar to move "too far" without causing harm or hitting limits, greatly simplifying its dimensional tolerances. At the time I didn't find any double-throw switches in such a low profile and with such low activation force (ie not a right-angle tactile) but I'm sure they're out there.> I would be concerned that if one of the slide switches ever got stiff,I didn't think of that. I've been more worried about the plastic springs becoming mismatched (due to plastic deformation or rotation of the end anchors in the PCB).I might place the two switches closer together so that a mismatched switch force would not have as much rotational leverage (compared to the rotational leverage of the springs).

author: HwAoRrDk
author_rank: Super Contributor
timestamp: December 08, 2023, 11:19:52 am
content: I think the ideal solution would be to put the two switches inline, one behind the other. Then there's no chance of binding, etc, but of course you don't have space for that, and I'm not sure what the spring arrangement would look like for that.One other thought is a couple of right-angle tactile switches with a 'T'-shaped actuator piece would obviate the need for a spring mechanism, as the switches have that built-in. But of course that might also take more space.

author: gabiz_ro
author_rank: Regular Contributor
timestamp: October 30, 2024, 12:47:54 pm
content: I know is old topic but few updates.SenseX_Return in fact are termination resistors on motherboard.Sense_Send read voltage based on voltage divider resulted by resistors inserted in circuit, via jack contacts.As result you can use only one switch to enable both, earphones and mic, using one resistor with value of parallel resistors on motherboard on pins 6 and 10.

author: wraper
author_rank: Unknown
timestamp: October 30, 2024, 01:27:32 pm
content: Quote from: HwAoRrDk on November 30, 2023, 05:38:37 am90% of their switches and connectors are utter trash though. For example they cannot make micro USB sockets with proper dimensions, so most of the plugs require way too much force to insert/pull out. USB-B with metal shell of non springy steel, so GND "leaves" get bent to fixed position on the first plug insertion and no longer make reliable contact. Shit microswitches, etc. The only decent parts I've seen were header connectors. LCSC has much better parts from other Chinese manufacturers which often also are significantly cheaper (Jing Extension of the Electronic Co., for example).