mothergoose729 wrote on 2021-03-15, 21:55:

I have multiple sound sources that can be playing at any one time (a common problem in DOS games), and I also have a number of s […]
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I have multiple sound sources that can be playing at any one time (a common problem in DOS games), and I also have a number of sound cards that I switch between with a hardware switch. Rather than a complex daisy chain of inputs and outputs that gets noisy and dumb, I thought a better solution would be to buy a simple mixer.

I am not much of an audio guy myself, so I might be talking gibberish. By mixer I mean I just want to merge them into a single output and be able to adjust the volume on each source. Nothing crazy. I know I need the following:

• 3 inputs, ideally 3.5mm or RCA
• Volume control
• RCA output
• Small footprint (limited desk space)
• Not expensive (50$ or less would be ideal)

An even better solution would be a digital mixer that I can output with TOSLINK or SPDIF. All of my sound sources except 1 are capable of digital out. A cursory google search suggests that all of those solutions are complex and expensive.

The three audio devices I plan to mix are - External midi device (my PC with MUNT mostly), the sound card output, and I want to run the CD audio from my optical drive out as well.

BTW while I am here, does anybody know what equipment I would need to convert 2 pin digital CD audio to 3.5mm or RCA? It seems simple enough to wire the 4 pin out to 3.5mm but I would like to bypass the internal DAC if I can.

Thoughts and suggestions are appreciated 😁. Thanks!

For analogue mixing, see https://www.amazon.com/Rolls-MX42-Stereo-Mini … /dp/B00102ZN40/

AFAIK, most mixers (and multitrack recorders that with mixers) that have S/PDIF input only have one input. One of the reasons for this is clock sync. If you have multiple S/PDIF devices that you need to mix you either need to

a) use the same sample rate on each device AND sync their word clocks
b) have a mixer that is able to resample and sync S/PDIF sources with non synched word clocks and different sample rates.

It is usually not an option to do a on consumer gear (most consumer products or even sound cards with S/PDIF output do not expose a way receive an external sync signal).

AFAIK, there is no affordable and currently available product that does b . The Roland M-1000 is a discontinued product that would fit the bill but it is hard to find and in 1000$ price range . There is, however, the DIY option, which I have chosen .
See Not so crazy idea : using a Raspberry Pi 4 with jackd , Zita A2J bridge and jack_mixer to make a software S/PDIF mixer

As for 2-pin S/PDIF, it is the same as coaxial S/PDIF except it is 5volts instead of 1volt (AFAICR). You can find simple conversion circuits on the Internet, may be someone can recommend one or even adapt a bracket meant for a motherboard .

darry wrote on 2021-03-16, 00:27:

For analogue mixing, see https://www.amazon.com/Rolls-MX42-Stereo-Mini … /dp/B00102ZN40/ […]
Show full quote

mothergoose729 wrote on 2021-03-15, 21:55:

I have multiple sound sources that can be playing at any one time (a common problem in DOS games), and I also have a number of s […]
Show full quote

I have multiple sound sources that can be playing at any one time (a common problem in DOS games), and I also have a number of sound cards that I switch between with a hardware switch. Rather than a complex daisy chain of inputs and outputs that gets noisy and dumb, I thought a better solution would be to buy a simple mixer.

I am not much of an audio guy myself, so I might be talking gibberish. By mixer I mean I just want to merge them into a single output and be able to adjust the volume on each source. Nothing crazy. I know I need the following:

• 3 inputs, ideally 3.5mm or RCA
• Volume control
• RCA output
• Small footprint (limited desk space)
• Not expensive (50$ or less would be ideal)

An even better solution would be a digital mixer that I can output with TOSLINK or SPDIF. All of my sound sources except 1 are capable of digital out. A cursory google search suggests that all of those solutions are complex and expensive.

The three audio devices I plan to mix are - External midi device (my PC with MUNT mostly), the sound card output, and I want to run the CD audio from my optical drive out as well.

BTW while I am here, does anybody know what equipment I would need to convert 2 pin digital CD audio to 3.5mm or RCA? It seems simple enough to wire the 4 pin out to 3.5mm but I would like to bypass the internal DAC if I can.

Thoughts and suggestions are appreciated 😁. Thanks!

For analogue mixing, see https://www.amazon.com/Rolls-MX42-Stereo-Mini … /dp/B00102ZN40/

AFAIK, most mixers (and multitrack recorders that with mixers) that have S/PDIF input only have one input. One of the reasons for this is clock sync. If you have multiple S/PDIF devices that you need to mix you either need to

a) use the same sample rate on each device AND sync their word clocks
b) have a mixer that is able to resample and sync S/PDIF sources with non synched word clocks and different sample rates.

It is usually not an option to do a on consumer gear (most consumer products or even sound cards with S/PDIF output do not expose a way receive an external sync signal).

AFAIK, there is no affordable and currently available product that does b . The Roland M-1000 is a discontinued product that would fit the bill but it is hard to find and in 1000$ price range . There is, however, the DIY option, which I have chosen .
See Not so crazy idea : using a Raspberry Pi 4 with jackd , Zita A2J bridge and jack_mixer to make a software S/PDIF mixer

As for 2-pin S/PDIF, it is the same as coaxial S/PDIF except it is 5volts instead of 1volt (AFAICR). You can find simple conversion circuits on the Internet, may be someone can recommend one or even adapt a bracket meant for a motherboard .

You are fantastic! The all digital solution was always going to be the most difficult. I will be following your rasberry pi project very closely 😁.

Regarding the 2 pin digital audio, I am not much for circuits, but if anybody can help me with the resistors I am sure I can solder in something myself. Or if anyone has the stuff or knows where to get it that would be a great option too.

I finally got the mixer in the mail today and unfortunately it isn't going to work for my setup. The mixer adds a lot of resistance to the line, even when turned all the way. So my headphones are far too quite. It also adds some noise to the line that I pick up on my extremely sensitive roland speakers, and since I have to turn up the volume on my DAC higher, that only gets worse. It's a shame. I am going to have to do the mixing in the card I think.

Anyway, I appreciate the feedback. Maybe I'll take a deep dive on the rasberry pi project you have going darry. An all digital mixer would probably be what I need considering all my limitations right now.

mothergoose729 wrote on 2021-03-28, 03:49:

I finally got the mixer in the mail today and unfortunately it isn't going to work for my setup. The mixer adds a lot of resistance to the line, even when turned all the way. So my headphones are far too quite. It also adds some noise to the line that I pick up on my extremely sensitive roland speakers, and since I have to turn up the volume on my DAC higher, that only gets worse. It's a shame. I am going to have to do the mixing in the card I think.

Anyway, I appreciate the feedback. Maybe I'll take a deep dive on the rasberry pi project you have going darry. An all digital mixer would probably be what I need considering all my limitations right now.

Too bad the that analogue mixer did not pan out for you . There are better but still relatively affordable (100 to 250 CAN$ ) home studio grade mixers from the likes of of Yamaha and Behringer that might be worth a look . They often have headphone amps built-in and, if necessary, a dedicated headphone amplifier can be used with the mixer's monitor out .

If you want to use a sound card as a mixer, have a look at this : Multichannel DOS mixer for DOS sound builds v0.49 for Live, v1.01 for Audigy

As for the Raspberry PI 4 S/PDIF mixer project, I am still tweaking it . I will post another update soon . I have mainly been working on improving reliability (eliminating x-runs/dropouts) and lowering latency .

Have a look at the Hart Maker mixer series. I have the Just Mixer 5 and I find it to be great. 5 Channel's input, Output via 3.5mm jack and RCA and also amplified output for headphones. It's powered via USB and is pretty compact. I've found it to be really good!

I wish proper data existed to truly compare a bunch of these cheap mixers on the basis of signal integrity and noise.

Shreddoc wrote on 2021-04-05, 21:39:

I wish proper data existed to truly compare a bunch of these cheap mixers on the basis of signal integrity and noise.

Somebody who owns one could always compare running RMAA while looping through mixer versus direct loopback (soundcard out to in) to get an idea .

I am using this method for testing in one of my projects : Not so crazy idea : using a Raspberry Pi 4 with jackd , Zita A2J bridge and jack_mixer to make a software S/PDIF mixer

I am doing it digitally, but running comparisons with analogue out/in is just as feasible .

EDIT : Using this method to compare different mixers might not be feasible (unless similar sound cards are used), but it should help weed out marginal/crappy units and help form the basis of a keep or return decision or serve as a warning to potential buyers.

I'm using one of these:
https://m.nl.aliexpress.com/item/4000500049769.html

It's very cheap compared to other mixers and it has 4 rca input channels. It doesn't require external power so the sound is not amplified but I find that the output is loud enough and it doesn't distort it. The casing is all metal which is nice too. And it's really small, so it's easy to put next to your setup. I've seen really happy with mine.

Hezus wrote on 2021-04-06, 20:07:

I'm using one of these:
https://m.nl.aliexpress.com/item/4000500049769.html

It's very cheap compared to other mixers and it has 4 rca input channels. It doesn't require external power so the sound is not amplified but I find that the output is loud enough and it doesn't distort it. The casing is all metal which is nice too. And it's really small, so it's easy to put next to your setup. I've seen really happy with mine.

I use the same mixer and i am quite happy with it too. Only downside i have with it, is some noise if amplifier is turned to high levels.

Sorry to bump this up but any of you Audiophiles have recommendations regarding old mixer brands from the end 70s 80s 90s?
Like I saw bunch of HAMA, Sound city and other noname brands floating around on the markets for almost free but are they good for PC audio, for sound card output voltage levels?
What to look for when buying an external mixer?

I'm also looking for something stereo with 4+ channels and basic functionality.