VOGONS


First post, by justin1985

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I remember my very first PC, an IBM Aptiva Pentium 120 - the tower type with the massive riser card and the roll down drive bay cover - had a very neat little 12v DC out socket on the back to power the supplied speakers. I'm sure this worked pretty well - there was slightly less of a rats' nest going on, and I don't recall it leading to particularly 'noisy' audio. I don't remember exactly how the Aptiva 12v out was wired up - as in, was it direct from the PSU, via the motherboard, via dedicated PCB etc?

Anyway, it struck me that now I'm messing around with old PCs and powered desktop speakers again, wouldn't it be cool to cut down the rats' nest a bit again?

Thinking about it, there should be plenty of amperage spare on the 12v rail of a PSU, especially if the HDD has been replaced by an SSD? Is there any reason not to strip down a Molex connector's 12v and ground wires, solder them to a 2.1mm barrel socket, and mount it through an enlarged ventilation hole on the back of a case?

I guess the obvious potential problem is noise/interference? Would looping the wires through a big old ferrite loop sort that out? Or would some sort of smoothing circuit be necessary?

Reply 1 of 14, by Tiido

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It is definitely workable but if things are buzzy it likely isn't because of noisy power rails (increased supply capacitors will likely fix that) but ground loop between the PSU and sound card but that can be fixed by taking the power from the sound card itself.

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Reply 2 of 14, by gerwin

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For systems with USB connector it may be a good option to have a set of these around, for temporary setups and such:
Manhattan 2600 Speaker system (model 161435), USB 5V powered / 3,5mm stereo jackplug analog input / With volume control.
I cannot find the Ampere rating, on the box or in the manual.

--> ISA Soundcard Overview // Doom MBF 2.04 // SetMul

Reply 3 of 14, by justin1985

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gerwin wrote on 2023-08-02, 16:06:

For systems with USB connector it may be a good option to have a set of these around, for temporary setups and such:
Manhattan 2600 Speaker system (model 161435), USB 5V powered / 3,5mm stereo jackplug analog input / With volume control.
I cannot find the Ampere rating, on the box or in the manual.

Ooh thanks for the recommendation! It’s good to know there are USB powered but traditional input speakers out there.

I’d actually bought a Dell soundbar (that conveniently clips to the 4:3 LCD monitor I’ve salvaged from work) which is described as USB powered, with 3.5mm line in as well. But, super annoyingly, it turns out that it needs USB audio to be configured before it will initialize and work with the 3.5mm line in! I was planning to just power it from the monitor’s USB hub, and use the 3.5mm input - but no luck! No active USB audio, no line in audio - so no DOS etc.

Reply 4 of 14, by gerwin

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justin1985 wrote on 2023-08-03, 08:36:

Ooh thanks for the recommendation! It’s good to know there are USB powered but traditional input speakers out there.

Yes, Those Manhattan speakers were tested to work on a i440BX Pentium II/III system with DOS and Windows 98. They sound reasonable, but their housing is as cheap as their price. Would be nice if they had mounting clips or feet or something, but they are just plastic cubes. The volume adjustment wheel is on the cable. Also no headphones connector.

Optionally one could power them without using an USB socket, by getting a "5V molex to USB C female" cable/adapter.

For headphone use, I recently obtained an Alcron HA-8 battery-powered amplifier. Though rebranded from "Alctron" to "Subzero". Seems fine so far.

justin1985 wrote on 2023-08-03, 08:36:

I’d actually bought a Dell soundbar (that conveniently clips to the 4:3 LCD monitor I’ve salvaged from work) which is described as USB powered, with 3.5mm line in as well. But, super annoyingly, it turns out that it needs USB audio to be configured before it will initialize and work with the 3.5mm line in! I was planning to just power it from the monitor’s USB hub, and use the 3.5mm input - but no luck! No active USB audio, no line in audio - so no DOS etc.

Good to know. Very annoying to have such a dependency.
I also use some of these Dell soundbars, two types, attached to either Dell U2312HM or U2412M monitors. All about ten years old by now:
Soundbar AY511: This is a more luxurious version with pretty good sound quality. But Dell writes it should NOT be used with the 12V supply connector on the backside of the monitor. So instead I use the power adapter that came with it. It is controlled with non-tactile/flush buttons, don't really like those. These buttons are for on/off, volume, muting and some sound "enhancement" modes.
Soundbar AX510: A cheaper version, with a sound quality obviously inferior to the AY511. Has a single big volume +on/off knob on the right. This one has a cable that can connect to the monitor's 12V supply. Works fine that way.
Both these soundbars use 3,5mm stereo jackplug for analog input. Both have headphone connectors on their left side.

For completeness, some notes about the monitors I mentioned, so I can save this page as pdf in my hardware database 😀 :
Dell U2312HM = 23" IPS 60Hz, 1920x1080 / DisplayPort, DVI-D, VGA (D-Sub) input +USB Hub / OSD aspect ratio options: 16:9 / 4:3 / 5:4.
Dell U2412M == 24" IPS 60Hz, 1920x1200 / DisplayPort, DVI-D, VGA (D-Sub) input +USB Hub / OSD aspect ratio options: 16:10 / 4:3 / 5:4.

--> ISA Soundcard Overview // Doom MBF 2.04 // SetMul

Reply 5 of 14, by Big Pink

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I also liked the idea of powering the speakers from the PSU rather than take up another wall socket. I came across the following and grabbed a bunch off eBay a while back.

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I thought IBM was born with the world

Reply 6 of 14, by gerwin

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Big Pink wrote on 2023-08-03, 19:47:

I also liked the idea of powering the speakers from the PSU rather than take up another wall socket. I came across the following and grabbed a bunch off eBay a while back.

Interesting concept.
Downside is, for obtaining 6 Volt it is dissipating quite some heat. The regulator/heatsink is 93,7 degrees Celsius in the photo here:
http://nana1451.web.fc2.com/dc.html

--> ISA Soundcard Overview // Doom MBF 2.04 // SetMul

Reply 7 of 14, by justin1985

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gerwin wrote on 2023-08-03, 15:56:
Good to know. Very annoying to have such a dependency. I also use some of these Dell soundbars, two types, attached to either D […]
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Good to know. Very annoying to have such a dependency.
I also use some of these Dell soundbars, two types, attached to either Dell U2312HM or U2412M monitors. All about ten years old by now:
Soundbar AY511: This is a more luxurious version with pretty good sound quality. But Dell writes it should NOT be used with the 12V supply connector on the backside of the monitor. So instead I use the power adapter that came with it. It is controlled with non-tactile/flush buttons, don't really like those. These buttons are for on/off, volume, muting and some sound "enhancement" modes.
Soundbar AX510: A cheaper version, with a sound quality obviously inferior to the AY511. Has a single big volume +on/off knob on the right. This one has a cable that can connect to the monitor's 12V supply. Works fine that way.
Both these soundbars use 3,5mm stereo jackplug for analog input. Both have headphone connectors on their left side.

Interesting! I can find the AY511 on the Dell support site, but absolutely nowhere else - it doesn't seem like ANY are available on eBay (UK) - I just get search results for AC511, which is the annoying USB dependent one 🙁 AX510 is an older type, which I originally bought one of, before I realised Dell changed the mounting arrangement. My monitor is an E1914 - the mounting points are just very small slotted holes on the very bottom, rather than the clips going into the rear of the monitor, like on older models. If I'd realised this a week or two earlier, I probably could have salvaged an earlier Dell monitor to suit the AX510 too - but a whole room full of them at work got taken away for e-waste (after sitting there for at least a year) just before I started trying to find a matching sound bar 🙁

It looks there are are also some Amazon Basics USB powered but 3.5mm audio speakers that look like they would do the job - and don't look too bad. "Amazon Basics USB-Powered Computer Speakers with Dynamic Sound".

When many of the wall power sockets in my house now have USB charger sockets too, and plenty of the power strips, seems like that could be a nice solution.

Reply 8 of 14, by elszgensa

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gerwin wrote on 2023-08-04, 00:07:

it is dissipating quite some heat. The regulator is 93,7 degrees Celsius in the photo here

Oh it gets better. Translating the linked page:

93 degrees Celsius... And that's not the end of it. In fact, after this, the temperature rose further and the thermometer read "HHH". In other words, it is impossible to measure.
I can really boil water.

tbh that sounds like it might be a broken unit. They can't have designed it that way, right? ...right?

Reply 9 of 14, by shevalier

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To power the amplifier from the power of the computer, you need to break the ground loop.
1. Signal transformer. It is expensive.
2. A very competent engineer who understands PCB routing and low-level signals.
They work for NASA or SpaceX.
Such an engineer will cost even more than installing a transformer.

So you have to listen to all the noise of the processor and video card.

PS. Its not power noise issue, "need more capacitor" is not work idea.
Its CMRR and other side effect, like parasitic ground current.

Aopen MX3S, PIII-S Tualatin 1133, Radeon 9800Pro@XT BIOS, Diamond monster sound MX300
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Reply 10 of 14, by Big Pink

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elszgensa wrote on 2023-08-05, 16:20:

tbh that sounds like it might be a broken unit. They can't have designed it that way, right? ...right?

It's a pretty basic looking board probably designed around the fact the manufacturer came into possession of a bin of 10,000 linear regulators of unknown quality. Hasn't effected me much since my speakers are 12V so I'm just using it as a molex to barrel jack adapter.

I thought IBM was born with the world

Reply 11 of 14, by Tiido

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A linear regulator burns all the excess volts as heat, so if you have 12V coming in and you only need 6V and you need some current too say 1A. This is 6W burned away in the regulator, that little dinky heatsink is going to get really hot in the process 🤣.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 12 of 14, by justin1985

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shevalier wrote on 2023-08-05, 16:35:
To power the amplifier from the power of the computer, you need to break the ground loop. 1. Signal transformer. It is expensive […]
Show full quote

To power the amplifier from the power of the computer, you need to break the ground loop.
1. Signal transformer. It is expensive.
2. A very competent engineer who understands PCB routing and low-level signals.
They work for NASA or SpaceX.
Such an engineer will cost even more than installing a transformer.

So you have to listen to all the noise of the processor and video card.

PS. Its not power noise issue, "need more capacitor" is not work idea.
Its CMRR and other side effect, like parasitic ground current.

Out of interest, is this the kind of transformer you're referring to? https://cpc.farnell.com/pulse/pls00547/ground … -p-p/dp/AV25541

I hit the ground noise issue when I started keeping my PC and MacBook both connected to the same Creative desktop speakers (all devices powered from the same mains power strip). But I bought the linked cable from Farnell, and the results have been perfect.

Reply 13 of 14, by shevalier

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justin1985 wrote on 2023-08-06, 15:13:

Out of interest, is this the kind of transformer you're referring to?

Yes, but what is on the link is a low-cost solution positioned exclusively for voice (300-3.3 kHz).
In the upper frequencies it works fine, in the middle - high distortion, in the low - "wow, what is it?".
For low distortion (and generally the ability to reproduce) at low frequencies, the transformer must have a large inductance, and therefore a large size.
For example, Lundahl Audio Output Transformer LL1517
Distortion (achieved with mixed feedback drive circuit, load 600 R) < 0.03 % @ 20 dBU, 30Hz
And that's a hell of a lot.

Aopen MX3S, PIII-S Tualatin 1133, Radeon 9800Pro@XT BIOS, Diamond monster sound MX300
JetWay K8T8AS, Athlon DH-E6 3000+, Radeon HD2600Pro AGP, Audigy 2 Value

Reply 14 of 14, by BitWrangler

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gerwin wrote on 2023-08-02, 16:06:

For systems with USB connector it may be a good option to have a set of these around, for temporary setups and such:
Manhattan 2600 Speaker system (model 161435), USB 5V powered / 3,5mm stereo jackplug analog input / With volume control.
I cannot find the Ampere rating, on the box or in the manual.

I was reading this thread the other day and thought "Yeah, why the hell don't I have a pair of USB powered speakers for testing etc???" with the obvious advantages of less wall sockets required etc. So I made a mental note to acquire some if the opportunity presented.

Dropped into a thrift today and the opportunity presented, there was even a choice, it was these little buggers (see pic) or a pair that seemed tall and tippy, the kind you'd always be standing up again or fetching from behind the desk even. So yeah, bought them for pocket change.... and damned if they don't sound wayyyy better than they have any right to... I know lying their arse of on specs is endemic at the low end, but they sound as loud as stuff marketed as "10W" which seems unpossible given they're sucking 2.5W maybe out of the USB. Anyway, some decent bass for the size and the treble doesn't muddy up in complex stuff, quite crisp reproduction really. Thought I'd get distortion when the volume was set to max, nope, they have a edge mount knob on back for volume. I looked them up but they seem to be primarily marketed in India, so don't know if they got brought by an immigrant or whether they're turning up kinda "grey market" in discount stores or something. Kinda second guessing their purpose, they'd fit nice in tight spots, sit between keyboard and monitor, and the perspex surround/foot thing lends itself to being clipped onto things by screwed or glued down binder strip clips or similar. So would get more pairs if I see them...

But back to the central topic. I personally would hook up 6V powered speakers to 5V or 15V powered to 12V and use them at up to about 8 tenths volume, no damage will occur but with the voltage being low they will start clipping and sound robot-ish. Ground loops are just bad luck really, might not happen. For if you've got 9V powered speakers, which have been quite common, if you trust yourself not to turn the volume past 3/4 and potentially overheat the amp chip and damage it, you can hook them to 12V. It is possible they have 12 or 16V rated components anyway and survive 12V 24/7, but unless you want to take it apart and check datasheets, don't turn the volume high if you do that. Another thing you can do if this is a situation where the household voltage side of the transformer has blown out (no connection or very high resistance between live and neutral) then you can strip the guts out, cut off the main transformer (Talking about older ones with linear supplies here, the heavy wall warts) and put 12V to where the transformer wires connect to the rectifiers on the DC convertor part and you'll end up with a 1.2-1.5 voltage drop and the benefit of all the smoothing and filtering originally built into it, and can tape that up into a small box and throw it inside the PC and route original DC cable out or whatever suits your sitch. Then you can go like 9/10 on the volume, measure what's coming out, if it's 10.5 volts it's probably lower than what the original linear floated at at low load, so if they aren't super precious speakers you can go for 100% volume probably. Some old speakers were a bit distorty at max anyway.

Edit: i guess re-using the board also works if the low voltage side of transformer is blown, but what usually happens if the DC side is overloaded is the bridge rectifier burns up.

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