Preamp between mixer and soundcard.

[kni52]

Hi there, I'm new here, so please be patient with me if I'm not up to speed with all of you. I'm wondering if I could get some more experienced advice on the following project that I want to do.

I'm working on setting up a home studio and an audio recording setup for an independent film I've been asked to work on. I recently purchased an M-Audio 1010LT. This card has 8 unbalanced analog ins and outs. While two of the inputs have switchable preamps, the other six do not. What I would like to do is build an 8 channel preamp to go between the card and my mixer, an old Fostex 450 (no built in preamps, -10db outs). My hope is to do this simply and inexpensively since, I think, all I really need to do is amplify the signal to a level the card can accept.

While I have done some searching for similar projects, I have not found anything use for this exact purpose. Most of what I've found are either mic preamps or phono preamps; I think I can use something far more simple. As far as putting something together myself, I'm sure with a little work I could start from scratch if I knew where to start (IC or discrete, what chips would work well etc.).

My questions so far:

- Are there any exiting projects that accomplish what I am looking for?

- Should I be looking at mic preamp circuits, or plain preamp circuits for this?


- Am I correct in thinking that I don't think I need all the features that a ready made 8 channel mic preamp would have?

-Any circuit or even IC recommendations?

- Quite a few of the schematics I've found are single channel. Is there anything I should take into consideration when thinking about putting 8 of these in a rackmount case? Crosstalk, power, matching components, etc.?

Any help would be greatly appreciated. Thank you in advance!

[sangram]

I'm assuming you need 8 microphones at exactly the same time? If not, the 1010LT can handle two mics fine.

If you need more channels, consider the audiobuddy, also from M-audio, not very expensive, and each does two channels. You need three of them to up the total to 8.

If you want to go the DIY route it shouldn't be too expensive in terms of parts, but mic preamps do require a lot of attention to layout, decoupling and signal routing, as we are talking pretty high gain. Low noise chips/discrete is a must, as well as good clean power supply.

I still am not clear on what you want to do, though. The unbalanced analog ins on the 1010LT need a -10dB signal, which your mixer is capable of supplying. You will not need a preamp between the mixer and the card.

If you need more mic inputs (for example, if you were doing live sound or lots of tracking) then you need a solution for adding more mics into the setup. If you can clarify the project a bit it would help to be clearer on recommendations.

[kni52]

Thanks for the reply sangram. It looks like I made some silly mistakes, misunderstood what I actually want/need myself, and left a confusing post for all of you as well. I'll try to clear things up a bit.

To answer your questions sangram:

Originally posted by sangram
I'm assuming you need 8 microphones at exactly the same time? If not, the 1010LT can handle two mics fine.

I currently anticipate needing up to 6 mics, maybe 8 in the future at a time for filming. While for the home studio use I anticipate using 1-2 mics with 1-2 non-mic sources such as guitar, synth, etc.

Originally posted by sangram
If you need more channels, consider the audiobuddy, also from M-audio, not very expensive, and each does two channels. You need three of them to up the total to 8.

I've read that the audiobuddy isn't that great. More importantly, I would like to keep everything rack mount and all of the preamps the same. That is, I'd rather have 8 identical preamps than a mix of the 2 onboard 1010LT preamps and 6 other preamps.

Originally posted by sangram
If you want to go the DIY route it shouldn't be too expensive in terms of parts, but mic preamps do require a lot of attention to layout, decoupling and signal routing, as we are talking pretty high gain. Low noise chips/discrete is a must, as well as good clean power supply.

I kind of want to stick with the DIY route because I will enjoy it far more than just buying something. I was hoping to start with an existing circuit or layout. I think I will have to go that route since addressing the decoupling and power supply portions are outside of my present experience.

Originally posted by sangram
I still am not clear on what you want to do, though. The unbalanced analog ins on the 1010LT need a -10dB signal, which your mixer is capable of supplying. You will not need a preamp between the mixer and the card.

You're right about this. I have to admit I got myself pretty confused with a couple of embarrassing mistakes. Both the card and the mixer are new to me, so I've been in unfamiliar waters with both of them. What happened is, I had come to the conclusion that my mixer didn't have preamps at all because of a line in the manual that states all outputs are -10db, also the preamps are sparsely mentioned, especially in the sections I had been scouring. I had forgotten that this is well within the range that the 1010LT is looking for and begun thinking that the mixer output was too low.
I finally figured out where I had gone wrong last night when I tested the mixer on it's own (I should have done this first) to figure out what was going on with it. All of my confusion and troubles came down to the following:
-I was originally using the direct outs from the mixer rather than the per channel send.
-I found that half of the cables I was using between the 450 and the 1010LT were bad.
-I've found that 3 of the 8 channels on the 450 are bad, 2 no-output, 1 is too noisy to use.
-I had the 2-8 inputs muted on my computer.

It turns out that the 450 has at least 5 different ways I can plug it into the 1010LT using the preamps: post preamp send (one for each 8 (6 working) channels, no mixer functions), 4 buss outs (through faders and eq), aux1 (2 outs, IIRC one vol control per chanel), aux2 send with switches determining where in the signal path it is sent (2 outs, IIRC one vol control, one pan setting per chanel), and the master outs (2). Also the preamps in the 450 are more than powerful enough (+50 db), enough to overdrive the 1010LT actually, if using the post-preamp send.

Originally posted by sangram
If you need more mic inputs (for example, if you were doing live sound or lots of tracking) then you need a solution for adding more mics into the setup. If you can clarify the project a bit it would help to be clearer on recommendations.

To clarify my confusing OP and what I am thinking now:
I had thought that I maybe needed some simple preamps for between the mixer and the card. Obviously (now ) that would not do me as much good as I thought.

Since I can only use the mixing capabilities on 4 channels, I don't think I'd like to lug the mixer in addition the rest of my equipment around from my home to the set just to use the preamps. I think it would be nice to have a small rack 8 channel mic pre. I wonder if a full blown mic preamp might be a bigger project than I anticipated. I'd love to hear some thoughts on DYI vs. ready made for an 8 channel mic pre.

Two that look interesting for me primarily because of the small size (portability) and secondarily, price are:
http://www.musiciansfriend.com/produ...amp?sku=185277
http://www.musiciansfriend.com/produ...amp?sku=480830
The latter I've read can be modded to improve it's sound.

As for my home recording uses, I'm pretty much set, I can use the mixer as a mixer, I doubt I'll be using more than 4 channels at once. I might use the mixer for since it has the ability to. The only other things I think I will need are a compressor, DI, and noise gate. I haven't spend any time researching these yet, but advice and recommendations would certainly be appreciated here too.

In general I think that building these myself will could be quite a bit of fun, and could result in a good bang for the buck ratio. Thoughts, recommendations, existing projects/designs etc?

On a somewhat related topic, do mic pres ever have DI capabilities, compressors or noise gates built in? I probably sound like I've never even been near recording equipment by now!

Hopefully that is more clear than my original post. Thanks again for the help!

[sangram]

Woah, that's a very helpful reply.

A single rack-mounted 8 channel mic pre like what you referenced would be good for the live sound part of your project. The Delta recording panel allows you to accept the +4 inputs (The NADY has only TS output so I'm assuming it's unbalanced -10, but you shouldn't worry with either - your card can handle both).

I only worry at the mention of 8 channels at a hundred dollars. Can't be very good channels.

I don't know if DIY will be cheaper/faster/better. It can be a fun project but you're not going to be up and running right away since you'll be building the preamp. Think about that. If the downtime isn't a big deal, there are schematics for mic preamps available, some from manufacturer datasheets.

Here's one:

http://sound.westhost.com/project66.htm

You will have to multiply the circuits by 8, add a power supply, case, connectors, and lay it all out so there is no hum, crosstalk and noise. Not a simple project really. I would up the budget to about 350 dollars (which is roughly what a quality DIY project like this will cost in parts) and look for suitable 8 channel rackmounts in that price range. Would not be afraid to buy used quality equipment, that will be a better investment than low end cheap gear. This is long-term stuff. However if you're really tight on funds I guess the SMPro should work out fine for you for some time.

Some in the general area to look for feature sets:

http://www.music123.com/Focusrite-Sa...73274.Music123
http://www.music123.com/PreSonus-FIR...25345.Music123

I know you've already bought a card, but these are excellent systems. And you use the ADAT to stream 8 channels over to your card.

http://www.wwbw.com/Focusrite-OctoPr...-i162448.music

http://www.sweetwater.com/c664--Multi-Channel_Preamps (oooh, pricey!!!)

You sound like you have a good mixer and have the connections figured out for home use. I don't use hardware effects at all. I have the bundled effects with my card and with software, and those are enough for me, but then I'm not working on paying projects anyway. Sorry can't help with more specific recommendations on those (but do check out www.prorec.com and www.homerecording.com , they have dedicated rack effects fora. Maybe you can pick up some more solid recommendations from there). Good rack gear is usually single-purpose though, and as you can see from that sweetwater link, the sky is literally the limit.

Once you get a rack in place you'll need a patchbay, and things can start becoming more complex quickly. Consider Wavelab effects suites, they have decent effects that are suitable for studio use at not much money (relative to good hardware units). The general wisdom in recording circles is 'Buy cheap, buy twice'.

And oh, do get onto the homerecording bbs. I can not afford or have access to much of the gear, but you can get solid advice and recommendations on gear for your studio from people who actually use the stuff.

If you do choose the DIY route, I'm sure there will be lots of advice here. It may also be a delightful way to start in DIY, even though it's a complex project it can be modular. Let us know what you want to do.

Enjoy!

[subterfuge]

Originally posted by kni52

More importantly, I would like to keep everything rack mount and all of the preamps the same. That is, I'd rather have 8 identical preamps than a mix of the 2 onboard 1010LT preamps and 6 other preamps.
...
I think it would be nice to have a small rack 8 channel mic pre. I wonder if a full blown mic preamp might be a bigger project than I anticipated. I'd love to hear some thoughts on DYI vs. ready made for an 8 channel mic pre.
...
On a somewhat related topic, do mic pres ever have DI capabilities, compressors or noise gates built in? I probably sound like I've never even been near recording equipment by now!

Plenty of stuff in just couple of racks sure is a good idea, especially if you have to haul the gear around. The problem (if any) is the usual one, the more you have under the same hood, the more compromises you have to make.

For your own home studio applications I could suggest a DIY pre-amp or two as you are so inclined. This depending on your needs of course. There are plenty of projects around, and with not too much money put in, you might even get a world class sound some pay big bucks to get from vintage shop items or reissues.

For the 8 ch. pre-amps I would forget anything DIY. Just for the price of the box and even the simplest components inside, you're already better off just getting what is available commercially.

For the DIY thing, you wouldn't necessarily want 8 channels of the same thing to start with. It's also about sound creation at that point, rather than just sound reproducion...so more colours you can have, the better in many cases. But building maybe even 4 different, nice sounding pre-amps under the same hood is too hard quest for the beginners, IMHO.

If looking (just) for the better spec pristine sound quality on all channels, you might want to go digital asap in the signal chain. Don't have to pay too much for that, compared to these cheap analog pres.

Yes, there are pre-amps in the market with some processing added , but as always, quality pays. Just check Manley Vox Box for one big buck example. That kinda things you might actually want to DIY later, way cheaper also.

Prodigy-Pro forums will give you more DIY details in that area you'd ever want to know.

http://www.prodigy-pro.com/forum/vie...75c54dc3fcd7a5

For overall view to (anything) recording and gear, ProSoundWeb might interest you too.
http://recforums.prosoundweb.com/

[kni52]

Thanks for all the great info guys! My thoughts and position have changed a bit once again, but I think that's bound to happen when learning so much so quickly. So here are some answers and an update:

Originally posted by sangram
Woah, that's a very helpful reply.

A single rack-mounted 8 channel mic pre like what you referenced would be good for the live sound part of your project. The Delta recording panel allows you to accept the +4 inputs (The NADY has only TS output so I'm assuming it's unbalanced -10, but you shouldn't worry with either - your card can handle both).

I only worry at the mention of 8 channels at a hundred dollars. Can't be very good channels.

I've found a few threads that suggest that the SM Pro Audio PR8 can be modded to improve it. The best one I've found so far is here: http://www.prodigy-pro.com/forum/viewtopic.php?t=344

I'm thinking that I might like to try this but, I may have found another route which I'll get to below.

Originally posted by sangram
I don't know if DIY will be cheaper/faster/better. It can be a fun project but you're not going to be up and running right away since you'll be building the preamp. Think about that. If the downtime isn't a big deal, there are schematics for mic preamps available, some from manufacturer datasheets.

Here's one:

http://sound.westhost.com/project66.htm

You will have to multiply the circuits by 8, add a power supply, case, connectors, and lay it all out so there is no hum, crosstalk and noise. Not a simple project really. I would up the budget to about 350 dollars (which is roughly what a quality DIY project like this will cost in parts) and look for suitable 8 channel rackmounts in that price range. Would not be afraid to buy used quality equipment, that will be a better investment than low end cheap gear. This is long-term stuff. However if you're really tight on funds I guess the SMPro should work out fine for you for some time.

Some in the general area to look for feature sets:

http://www.music123.com/Focusrite-Sa...73274.Music123
http://www.music123.com/PreSonus-FIR...25345.Music123

I think I'm going to hold off on the DYI on the preamp for now. I think I would like to give a high end one a try in the future though.

Originally posted by sangram
I know you've already bought a card, but these are excellent systems. And you use the ADAT to stream 8 channels over to your card.

http://www.wwbw.com/Focusrite-OctoPr...-i162448.music

http://www.sweetwater.com/c664--Multi-Channel_Preamps (oooh, pricey!!!)

My card does allow me to bring in 8 digital channels over the SPDIF connection, but I have to admit I know very little about this connection, what it's used for or what kind of gear would have it. I'm not even sure if I would want to search out gear that would use it. Since using a digital signal before my card would bypass the D/As in the 1010lt which if I understand correctlty are actually pretty good. So to make a move to a more digital option would be mostly connection convienience right? Plus wouldn't it cost more since I would be buying additional equipment to basically bypass much of what the 1010lt does? Or are you just mentioning the digital route because it is a route for higher quality expansion in the future. Forgive me if this is some missing the point silliness on my part.

Originally posted by sangram
You sound like you have a good mixer and have the connections figured out for home use. I don't use hardware effects at all. I have the bundled effects with my card and with software, and those are enough for me, but then I'm not working on paying projects anyway. Sorry can't help with more specific recommendations on those (but do check out www.prorec.com and www.homerecording.com , they have dedicated rack effects fora. Maybe you can pick up some more solid recommendations from there). Good rack gear is usually single-purpose though, and as you can see from that sweetwater link, the sky is literally the limit.

Thanks for the links, I've learned quite a bit more from them already!

Originally posted by sangram
Once you get a rack in place you'll need a patchbay, and things can start becoming more complex quickly. Consider Wavelab effects suites, they have decent effects that are suitable for studio use at not much money (relative to good hardware units). The general wisdom in recording circles is 'Buy cheap, buy twice'.

As far as the software processors, I've been looking more into what I have available on my system. I'm using a Ubuntu Studio setup so there is a wealth of LADSPA plugins http://www.ladspa.org/ for processing audio including compressors, reverb, delay, tube emblation, and dozens more I have no idea what to do with. I think I'm going to try going this route for now on for the compressor and gate.

Originally posted by sangram
And oh, do get onto the homerecording bbs. I can not afford or have access to much of the gear, but you can get solid advice and recommendations on gear for your studio from people who actually use the stuff.

If you do choose the DIY route, I'm sure there will be lots of advice here. It may also be a delightful way to start in DIY, even though it's a complex project it can be modular. Let us know what you want to do.

Enjoy!

Modular was kind of what I was hoping for, and will probably do in the future. I do plan on coming to everyone here for help on the other DIY stuff I'll do in the future.

Originally posted by subterfuge
Plenty of stuff in just couple of racks sure is a good idea, especially if you have to haul the gear around. The problem (if any) is the usual one, the more you have under the same hood, the more compromises you have to make.

For your own home studio applications I could suggest a DIY pre-amp or two as you are so inclined. This depending on your needs of course. There are plenty of projects around, and with not too much money put in, you might even get a world class sound some pay big bucks to get from vintage shop items or reissues.

This is kind of what I was thinking, and now as a future project. Any specific projects that you would recomend?

Originally posted by subterfuge
For the 8 ch. pre-amps I would forget anything DIY. Just for the price of the box and even the simplest components inside, you're already better off just getting what is available commercially.

For the DIY thing, you wouldn't necessarily want 8 channels of the same thing to start with. It's also about sound creation at that point, rather than just sound reproducion...so more colours you can have, the better in many cases. But building maybe even 4 different, nice sounding pre-amps under the same hood is too hard quest for the beginners, IMHO.

If looking (just) for the better spec pristine sound quality on all channels, you might want to go digital asap in the signal chain. Don't have to pay too much for that, compared to these cheap analog pres.

This sounds interesting, but as I said above I don't know much about it, and I'm somewhat confused about the details like the how and why. It sounds like maybe just getting the signal into the computer right away and using software tools to to the rest might be the best plan?

Originally posted by subterfuge
Yes, there are pre-amps in the market with some processing added , but as always, quality pays. Just check Manley Vox Box for one big buck example. That kinda things you might actually want to DIY later, way cheaper also.

Prodigy-Pro forums will give you more DIY details in that area you'd ever want to know.

http://www.prodigy-pro.com/forum/vie...75c54dc3fcd7a5

For overall view to (anything) recording and gear, ProSoundWeb might interest you too.
http://recforums.prosoundweb.com/

Thanks for these great links too!

After continued reading and exploring I bought a
Behringer DI800 this weekend. While I bought this because I'll need more than one signal to go though a DI, I'm thinking about giving it a try as a makeshift mic pre since it is 8 channel, has preamps (and pads) built in, and will take both balanced and unbalanced as input. I realize that this might not be an ideal use since it is not meant to be a mic pre, but my initial test seems to indicate that it can do the job, and with my limited knowledge I haven't been able to think of a reason not to. The only disadvantage so far seems to be that I won't have a variable gain to adjust the signal going into my card, so I'll have to adjust input volume in the software mixer. Of course I will still have to get something like the PR8 when I have a need for phantom power or use my mixer, but I don't have any mics that can't also be battery powered, so this might be good for a while. I have only tested this with one dynamic mic, so it may not even work with a condenser mic. What do you guys think of this? Am I overlooking something that will be a problem, or is this is a completely stupid idea?

Assuming that the above idea isn't completely absurd, I think my next two projects will be to build a breakout box/patchbay for my 1010lt and a portable rack case, but I'll give those threads of their own.

Thanks for the help and for putting up with my inexperience!