Passive mixers are very inexpensive, especially compared to your MIDI gear.

You can loop through but afaik they both need to be on then in order to use one.

I have a little, cheap, stereo 4-input switchbox with headphone jacks in and out. Works fine. I use another one to switch spdif into a DAC.

It sounds like the best way is to purchase a mixer but my desk is already extremely crowded. Are there any other options available? I'm new to MIDI but it looks like both of my devices have a "MIDI THRU" jack as well. Would that help?

In this statement, you are mixing two different things. Are you asking how to connect both devices via MIDI at the same time, or how to get their sound output into your sound card at the same time? Both is actually pretty easy and does not require additional hardware (apart from cables). For MIDI, connect the most-used device via MIDI to the PC, then route it's "MIDI Thru" to the "MIDI In" of the second device.

As for sound output, it's almost the same, just with the audio connectors. Connect the audio out from the first device to the audio in of the second device, and from there you go to line in of your sound card. Of course, both devices always have to be powered for this to work.

For audio outputs a proper way is to use a mixer like Vixen Mixer https://kvgear.com/products/vixen-mixer or even these cheap chinese 8-channel mixers (effectively it has 4 stereo channels): https://www.aliexpress.com/item/32529940373.html
ie.

1SOUND CARD LINE OUT ----------- MIXER >--------- OUT TO AMP
2                                 |  |								
3MT-32 AUDIO OUT -----------------+  |
4                                    |
5SC-55 AUDIO OUT --------------------+

Don't use line in on your sound card for 'mixing in' the audio from your modules - quality will be degraded, you risk introducing ground loops as well.

Use midi through to stack your midi devices (connect midi out from your sound card/mpu-401 to midi in on one of the modules and then use another midi cable to connect midi thru on this module to midi in on the next module). It allows you to use just one control device (computer in this case, but it could also be a keyboard, sequencer etc) to control several midi devices with just a single physical link (cable).

HanJammer wrote:

Don't use line in on your sound card for 'mixing in' the audio from your modules - quality will be degraded, you risk introducing ground loops as well.

I don't think you got my reply right. There's audio in on the SC-55 for mixing with an external source, so the mixer is there already. Mixing is done by the device and only the final output goes into line in of the sound card. That setup is perfectly fine, as that's what the audio in jacks are intended for.

derSammler wrote:

HanJammer wrote:

Don't use line in on your sound card for 'mixing in' the audio from your modules - quality will be degraded, you risk introducing ground loops as well.

I don't think you got my reply right. There's audio in on both devices for mixing with an external source, so the mixer is there already. Mixing is done by the device and only the final output goes into line in of the sound card. That setup is perfectly fine, as that's what the audio in jacks are intended for.

What makes you think I replied to you?

This setup is very far from being perfect.
Routing audio path through several devices (like the stack of midi modules and the line in of the sound card) introduces noise (actually a lot of noise) along the way and you loose a versatility of a dedicated audio mixer, not to mention the risk of ground loops I mentioned earlier (if the devices for some/any reason are not separated correctly). It's one of the most common mistakes. Only advantage is less cables but it doesn't really matter with just three devices.

PS: There is audio in on SC-55mkii and there is no audio in on MT-32.

This setup is very far from being perfect.

Are you aware that both the SC-55 and the MT-32 were low-cost consumer devices? He's not setting up a studio environment. It's always funny to see when people trying to suggest high-end solutions for low-end problems. Yes, he COULD buy a mixer, but it's simply not needed.

PS: There is audio in on SC-55mkii and there is no audio in on MT-32.

I know. I corrected that already in my statement.

Something I came across years ago and have applied with my two devices.
I went with option two, since my MPU-IPC-T has two MIDI Out connectors.
The SC-55 allows you to mute the output from the MT-32

derSammler wrote:

Are you aware that both the SC-55 and the MT-32 were low-cost consumer devices? He's not setting up a studio environment. It's a […]
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This setup is very far from being perfect.

Are you aware that both the SC-55 and the MT-32 were low-cost consumer devices? He's not setting up a studio environment. It's always funny to see when people trying to suggest high-end solutions for low-end problems. Yes, he COULD buy a mixer, but it's simply not needed.

PS: There is audio in on SC-55mkii and there is no audio in on MT-32.

I know. I corrected that already in my statement.

MT-32 was never low cost nor a consumer device (IIRC MT-32 + MPU was around 600 USD - same as IBM Music Feature Card and 1/3 of DX-7 for example, and AdLib card and Game Blaster for comparison costed way less - like 130 USD). It was intended for professional / prosumer market - specifically as an extension for D-50 - if you needed better polyphony out of your expensive D-50 - you bought one of these.
Later when Roland realized that there is a niche on the consumer market (computer games) they released CM-32L, CM-64 and MT-100... and to some extent LAPC-I - a bit less expensive devices using the same sound engine.

Mixer is by no means a 'high end solution' - it's sensible, low cost and simple solution for a simple problem. This is technically oriented forum so don't be surprised that people suggest solutions logical and correct from technical point of view. Just because something is possible (like daisy-chaining audio devices) - doesn't mean that it should be used (when better solutions are at hand).

What about something like the Behringer U-Control UCA202 Ultra-Low Latency 2 In/2 Out USB Audio Interface? It's a USB device that provides a line input?

I'm trying to avoid having a large mixer on my desk if at all possible, but I don't want the audio to suffer too much. I'm not a huge audiophile so if the audio quality loss is barely noticeable then I'm OK with it. However, if there is a lot of noise/static/hissing then it won't work for me...

EDIT: What about a simple audio switcher/selector? (kolderman also suggested this)

sofakng wrote:

What about something like the Behringer U-Control UCA202 Ultra-Low Latency 2 In/2 Out USB Audio Interface? It's a USB device that provides a line input?

I'm trying to avoid having a large mixer on my desk if at all possible, but I don't want the audio to suffer too much. I'm not a huge audiophile so if the audio quality loss is barely noticeable then I'm OK with it. However, if there is a lot of noise/static/hissing then it won't work for me...

EDIT: What about a simple audio switcher/selector? (kolderman also suggested this)

That USB audio interface is a long way to go just to get another line in, and you still have to use a software mixer. How big is too big for your desk? They make some remarkably small mixers these days. Just search Amazon for "mini mixer" and see what you get. I personally use the Mackie Mix5 which is about the size of a notepad, but they make 'em even smaller.

OK - I'll take a look at the mini mixers.

That USB device I linked to above is only $28.99 (on sale from $44.99). If the quality between that and a hardware mixer is equivalent, I just thought this might be an easier way to go.

sofakng wrote:

What about something like the Behringer U-Control UCA202 Ultra-Low Latency 2 In/2 Out USB Audio Interface? It's a USB device that provides a line input?

I'm trying to avoid having a large mixer on my desk if at all possible, but I don't want the audio to suffer too much. I'm not a huge audiophile so if the audio quality loss is barely noticeable then I'm OK with it. However, if there is a lot of noise/static/hissing then it won't work for me...

EDIT: What about a simple audio switcher/selector? (kolderman also suggested this)

Both mixers I gave you links are not much bigger than 3,5" hdd. Even this cheap chinese one is basically silent (won't introduce any noise) and is battery powered too (battery lasts long) - I have one of those in my home studio - you will need 2 RCA-6.35mm TS cables (for SC-55), two 6.35mm TS <-> 6.35 mm TS cables (for MT-32) and single 3.5 mm TRS <-> dual 6.35 mm TS cable for your sound card. Also output cable/cables depending on what kind of output device you have.

Audio interface is another option, but the one you mentioned only has two mono inputs and two mono outputs. I wouldn't spend money on anything like this. Better option would be something with built in preamps and maybe even USB-MIDI audio interface which would allow you to use the midi modules with your modern PC.

Hey everybody... thanks again SO MUCH for the advice!

I decided to go with a good quality audio switcher (JDS Labs OL Switcher) and connect both devices to it. I received it over the weekend and it sounds fantastic.

Thanks again for all of the help!

Another option is to just get a Y-cable for headphones and plug it into the sound card’s line in. Then just plug MT32’s and SC-55’s output into it. You do need cables to convert the modules’ output to 3.5 minijacks.

I'm sure this isn't he most audiophile way of doing it, but this is basically what I'm doing to have 3 separate sound modules connected at once to my PC. I have an MT-32, MT-200, and MT-90 all connected. This is how I have them setup:

I have the Roland UMone USB-MIDI from my PC to the MIDI IN on the MT-32, then use a small MIDI cable from the MIDI THRU on the MT-32, into the MIDI-IN on the MT-200, then another small MIDI cable from the MT-200 MIDI THRU to the one and only MIDI IN on the MT-90. I have all of the modules audio output going into something like this:

https://www.walmart.com/ip/4-Way-AV-Switch-RC … -More/325709139

And then use an RCA to 1/8" stereo cable from that AV selector into my SB Zxr Line-in. Technically all three modules are receiving the same data at the same time, but I only push the button on the one I want to actually to hear at the time. So if I'm playing a Sierra adventure game where the MT-32 will sound the best, I push the button to hear music/sounds from it, and then when I play some Doom I switch over to the MT-200 or MT-90.

Again, it is simple. But it doesn't take up much space at all and just works for what I'm needing to do with only one USB connection from the computer to all the modules and one audio line coming back into the PC.

jheronimus wrote:

Another option is to just get a Y-cable for headphones and plug it into the sound card’s line in. Then just plug MT32’s and SC-55’s output into it. You do need cables to convert the modules’ output to 3.5 minijacks.

Never ever do this if you care about your equipment. Easy way to fry things as you basically feeding with device output line with other's device's output. Always use a mixing circuit - even a simple passive mixer.

HanJammer wrote:

jheronimus wrote:

Another option is to just get a Y-cable for headphones and plug it into the sound card’s line in. Then just plug MT32’s and SC-55’s output into it. You do need cables to convert the modules’ output to 3.5 minijacks.

Never ever do this if you care about your equipment. Easy way to fry things as you basically feeding with device output line with other's device's output. Always use a mixing circuit - even a simple passive mixer.

I don't understand why that would be dangerous. I'm not using both modules at the same time and I don't even keep them both turned on. Only one at the time.