DIY audio input for MAC/PC?

[darron]

hey. i've had a quick search and couldn't really find anything appropriate. i'm up for a challenge. i'd like a build a hifi audio input for my mac that would be well suited for accepting a guitar input signal for recording. i've seen cheap kits for this sort of thing for pc which can go into the gaming/midi interface etc. the audio inputs on computers, even my macbook pro, isn't well suited for recording instruments. there's just too much noise and i think that they mostly all have a preamp for microphones etc. i can't plug my mixer into sound cards because it clips harshly, and turning the recording level down just won't cut it.

anything exist? is it too crazy?

[aron]

It's not crazy. Mostly all the boosters online will do this. Even the beginner project will work.

This should work as well:

http://diystompboxes.com/pedals/schems/shakaboost.jpg

This one is fun too ( I plug my pedals into it)

http://www.diystompboxes.com/pedals/schems/msim.jpg

[trevize]

the best solution is: buy a cheap usb audio card like the new edirols or m-audio.
good external soundcards are equipped with decent microphone/instrument preamp, decent A/D converters and provide low latency.
you can get an M-audio for 100$ probably

[darron]

It's not crazy. Mostly all the boosters online will do this. Even the beginner project will work.

This should work as well:

http://diystompboxes.com/pedals/schems/shakaboost.jpg

This one is fun too ( I plug my pedals into it)

http://www.diystompboxes.com/pedals/schems/msim.jpg

i was thinking something with a usb/firewire interface. the sound card sounds horrible to me. or is that just my misconception/misuse?

the best solution is: buy a cheap usb audio card like the new edirols or m-audio.
good external soundcards are equipped with decent microphone/instrument preamp, decent A/D converters and provide low latency.
you can get an M-audio for 100$ probably

so i'm taking the wrong approach maybe. i used to have an old soundcard where i could actually turn that annoying preamp off. with everything new that i've played with by the time that the signal has been lowered enough to not clip the preamp, there's wayyyy too much noise. also, you can hear all the computer noises being picked up. for example, you can hear hte noise of the hard drive moving or the interference from the finger pad.

[aron]

The Line 6 USB interfaces are great. SUPER bang for the buck and fun! I use the KB37 a lot (keyboard+interface).

[MartyMart]

Darron, sounds like it could be an interesting project, you'll need all the specs for USB/Firewire connections
but remember that after the jack/mic input you'll have an analog to digital convertor to deal with before the
signal gets down the USB/Firewire cable to your mac/PC !!
As suggested, it may be much easier to get a simple/cheap interface for between $100-200
On my Powerbook system, I use a Digigram pocket V2 card ( PCMCIA ) which has a nice breakout cable with
digital I/O balanced line I/O and heaphones/wordclock connection.
This was around $600 though !! - pro sound and noiseless 24bit recordings.
There's cheaper stuff these days ( this is a 6 year old card )
Good luck though, let us know how you get on

Marty.

[darron]

Darron, sounds like it could be an interesting project, you'll need all the specs for USB/Firewire connections
but remember that after the jack/mic input you'll have an analog to digital convertor to deal with before the
signal gets down the USB/Firewire cable to your mac/PC !!
As suggested, it may be much easier to get a simple/cheap interface for between $100-200
On my Powerbook system, I use a Digigram pocket V2 card ( PCMCIA ) which has a nice breakout cable with
digital I/O balanced line I/O and heaphones/wordclock connection.
This was around $600 though !! - pro sound and noiseless 24bit recordings.
There's cheaper stuff these days ( this is a 6 year old card )
Good luck though, let us know how you get on

Marty.

hey Marty. I was hoping there might be a project out there. I don't want to design one! maybe there would be some sort of smd generic (hifi) analogue/digital converter. it would obviously need to be a chipset common enough to have drivers for it, since nobody wants to write a driver! i guess it's not really practical.

thanks (:

[MartyMart]

Some stuff to read, hope it's applicable :

http://www.maxim-ic.com/appnotes.cfm/an_pk/3775
http://www.edn.com/archives/1997/102397/22di_05.htm
http://www.faculty.iu-bremen.de/birk/lectures/PC101-2003/14usb/FINAL%20VERSION/usb_protocol.html
http://www.yov408.com/html/tutorials.php?s=42

[MartyMart]

Also, you will get more help if this is moved to the "digital/pic" section of the forum 

[darron]

Some stuff to read, hope it's applicable :

http://www.maxim-ic.com/appnotes.cfm/an_pk/3775
http://www.edn.com/archives/1997/102397/22di_05.htm
http://www.faculty.iu-bremen.de/birk/lectures/PC101-2003/14usb/FINAL%20VERSION/usb_protocol.html
http://www.yov408.com/html/tutorials.php?s=42

i don't suppose that any of those are really applicable for an audio input device. it would be a lot of trouble to get it going as an audio input wouldn't it?

[MartyMart]

Well the analog audio "in" is the easy bit ! - there's a ton of that stuff here, it's the "turning it into digital
and stuffing it down a USB cable" that's the hard bit ..... or have I totally misunderstood your idea ? !!
In the former case, those articles are then quite useful.
Personally I can't see any reason ( other than a learning reason ) to try and make one, when $125 will get
you a small MAudio or Edirol device.
MM.

[darron]

Well the analog audio "in" is the easy bit ! - there's a ton of that stuff here, it's the "turning it into digital
and stuffing it down a USB cable" that's the hard bit ..... or have I totally misunderstood your idea ? !!
In the former case, those articles are then quite useful.
Personally I can't see any reason ( other than a learning reason ) to try and make one, when $125 will get
you a small MAudio or Edirol device.
MM.

i understand that the digital conversion there would work, but it would still have the problems of needing a driver on the software side to get it going as an audio device. i definitely didn't want to do this to save some money, nor did i want it as a learning activity. i wanted to know if there were any diy or clones of circuits that have already been designed for this. my circuit design knowledge needs LOTS of development, but i wanted to try to push my building skills pretty hard.

i don't think what i wanted existed, so i think i should invest my time elsewhere

thanks for your input everyone (:

[Seljer]

some modern soundcards (even the integrated ones) come with a S/PDIF input, if you make your own preamp and a ADC you might be able to get something oing

otherwise I think just using a basic preamp of some sort with the line in input instead of the mic input would be a pretty good improvment over the mic input's builtin preamp thing

[darron]

some modern soundcards (even the integrated ones) come with a S/PDIF input, if you make your own preamp and a ADC you might be able to get something oing

otherwise I think just using a basic preamp of some sort with the line in input instead of the mic input would be a pretty good improvment over the mic input's builtin preamp thing

my macbook pro doesn't have a line in, but i think that you are onto a really good thought with the analog to SPDIF convertor! i don't have an spdif input either, but that i would be willing to buy if i could make my own hifi input. that would solve all of the issues. i'll look into it. thanks for the idea! (:

[darron]

first thing i found was this... which is half of the requirements:

http://www.ecp.cc/usb-spdif.html

[evilpaul]

some modern soundcards (even the integrated ones) come with a S/PDIF input, if you make your own preamp and a ADC you might be able to get something oing

otherwise I think just using a basic preamp of some sort with the line in input instead of the mic input would be a pretty good improvment over the mic input's builtin preamp thing

my macbook pro doesn't have a line in, but i think that you are onto a really good thought with the analog to SPDIF convertor! i don't have an spdif input either, but that i would be willing to buy if i could make my own hifi input. that would solve all of the issues. i'll look into it. thanks for the idea! (:

Actually, you MacBook Pro does have a line-in AND an optical S/PDIF input.

Being lazy and pasting from the Apple website:

The sound input jack accepts line-level stereo signals up to 24-bit stereo 44.1-192kHz sampling rate. 
It also accepts a stereo miniplug-to-RCA cable adapter for connecting stereo equipment to the computer.


Optical audio input is SPDIF format and uses a standard toslink cable with a toslink mini-plug adapter, 
accepting up to 24-bit stereo and 44.1-96kHz sampling rate.

[darron]

some modern soundcards (even the integrated ones) come with a S/PDIF input, if you make your own preamp and a ADC you might be able to get something oing

otherwise I think just using a basic preamp of some sort with the line in input instead of the mic input would be a pretty good improvment over the mic input's builtin preamp thing

my macbook pro doesn't have a line in, but i think that you are onto a really good thought with the analog to SPDIF convertor! i don't have an spdif input either, but that i would be willing to buy if i could make my own hifi input. that would solve all of the issues. i'll look into it. thanks for the idea! (:

Actually, you MacBook Pro does have a line-in AND an optical S/PDIF input.

Being lazy and pasting from the Apple website:

The sound input jack accepts line-level stereo signals up to 24-bit stereo 44.1-192kHz sampling rate. 
It also accepts a stereo miniplug-to-RCA cable adapter for connecting stereo equipment to the computer.


Optical audio input is SPDIF format and uses a standard toslink cable with a toslink mini-plug adapter, 
accepting up to 24-bit stereo and 44.1-96kHz sampling rate.

ohh wow evilpaul. it's like i just got something for free! i'll take a look into analog to optical converters then (:

any diy projects come to mind?

i suppose ebay will be the go.

[caress]

if you're looking to spend a little bit more, presonus makes great firewire interfaces.  the firebox is a good and simple 4in/6out interface for 300 new, so you can probably find one for 150-200 used...
you can even get an older model motu 828 8in/8out w/ firewire and s/pdif for around 250-400...if you want to go cheap, then maudio or edirol are good choices.  don't know much about diy, but i figured i would throw my 2c in.

[darron]

if you're looking to spend a little bit more, presonus makes great firewire interfaces.  the firebox is a good and simple 4in/6out interface for 300 new, so you can probably find one for 150-200 used...
you can even get an older model motu 828 8in/8out w/ firewire and s/pdif for around 250-400...if you want to go cheap, then maudio or edirol are good choices.  don't know much about diy, but i figured i would throw my 2c in.

the presonus firepod looks really good! thanks (:

a friend told me to get an maudio, but i wanted a bit more flexibility and to work with balanced xlr lines now.

i'll try ot wait for a used one to pop up on ebay (:

[caress]

hope you can find one!