I need a LOT of help designing a mixer

[u=0]

(First a quick preface about me ...) I'm a part-time audio engineer and drummer. I know how to hook up gear and use it, but I know almost nothing about the insides of it. I can read schematics for and build most simple devices, but understanding and designing them is something I'm only just now getting into.

So with that being said, I welcome almost any productive answer you may have. Even if it's only to say, "Whoa! You're getting in way over your head. First read this [book/site/thread/etc] then come back after," that's fine, too.

The scenario:

I have 8 mics hooked up to my drums but only two input channels available on the house mixer, so I need to 'pre-mix' my 8 mics into a stereo feed for it. I'd also like to have a headphone amp on it to reference my mix or to use during practice.

If I had $500 to spend on my own mixer, this would be an easy fix, but I don't. So, I'd love to just build a simple mixer for this specific purpose instead. But, my budget is extremely low: $50 for parts would thrill me.

When I first started thinking about this, it seemed simple, but as I got further in and started breaking down each portion of the build, I realized there were too many questions I can't answer:

1.) For the sake of expenses, not including pre amps onboard is ideal, but can mic-level signals even be mixed on a circuit board without butchering the sound quality?

2a.) Will the balanced signal need to be converted back into an unbalanced signal? (I'm thinking yes.)

2b.) How is a balanced signal converted back into an unbalanced signal?

2c.) How is an unbalanced signal converted into a balanced signal?

3a.) How do I create Phantom Power, or can I allow Phantom Power from the house mixer to 'pass through' my build to my mics?

3b.) How do I filter out the DC Phantom Power from other parts of the build that don't need it?

4a.) I want to include a simple headphone amp for rerence (perhaps an LM386). Can I use the house mixer's Phantom Power to power it?

4b.) If I use the headphone amp concurrently with the 'main' output, will I lose too much signal level? (Should I just switch it off?)

In summary:

- Extremely low budget
- Not hi-fi; 'Practice' quality acceptible
- 8 balanced mic inputs (Phantom Power req'd on 2)
- 2 balanced mic outputs (un-amp'd mix of inputs)
- 2 unbalanced headphone outputs (through op-amp)
- Ideally, Phantom Power provided by house mixer

--------

As you can see, I'm on step 3 of perhaps 100, so any advice, guidance or reference you have is more than welcome.

 

[davenn]

(First a quick preface about me ...) I'm a part-time audio engineer and drummer. I know how to hook up gear and use it, but I know almost nothing about the insides of it. I can read schematics for and build most simple devices, but understanding and designing them is something I'm only just now getting into.

So with that being said, I welcome almost any productive answer you may have. Even if it's only to say, "Whoa! You're getting in way over your head. First read this [book/site/thread/etc] then come back after," that's fine, too.

The scenario:

I have 8 mics hooked up to my drums but only two input channels available on the house mixer, so I need to 'pre-mix' my 8 mics into a stereo feed for it. I'd also like to have a headphone amp on it to reference my mix or to use during practice.

If I had $500 to spend on my own mixer, this would be an easy fix, but I don't. So, I'd love to just build a simple mixer for this specific purpose instead. But, my budget is extremely low: $50 for parts would thrill me.

When I first started thinking about this, it seemed simple, but as I got further in and started breaking down each portion of the build, I realized there were too many questions I can't answer:

1.) For the sake of expenses, not including pre amps onboard is ideal, but can mic-level signals even be mixed on a circuit board without butchering the sound quality?

2a.) Will the balanced signal need to be converted back into an unbalanced signal? (I'm thinking yes.)

2b.) How is a balanced signal converted back into an unbalanced signal?

2c.) How is an unbalanced signal converted into a balanced signal?

3a.) How do I create Phantom Power, or can I allow Phantom Power from the house mixer to 'pass through' my build to my mics?

3b.) How do I filter out the DC Phantom Power from other parts of the build that don't need it?

4a.) I want to include a simple headphone amp for rerence (perhaps an LM386). Can I use the house mixer's Phantom Power to power it?

4b.) If I use the headphone amp concurrently with the 'main' output, will I lose too much signal level? (Should I just switch it off?)

In summary:

- Extremely low budget
- Not hi-fi; 'Practice' quality acceptible
- 8 balanced mic inputs (Phantom Power req'd on 2)
- 2 balanced mic outputs (un-amp'd mix of inputs)
- 2 unbalanced headphone outputs (through op-amp)
- Ideally, Phantom Power provided by house mixer

--------

As you can see, I'm on step 3 of perhaps 100, so any advice, guidance or reference you have is more than welcome.

hi there,
Sign your name next time its just coutesy so we know who we are talking to

yes all those things can be done that you would like. its probably gonna cost lots more than $50 in parts
rather than the cost of a ready built unit have you considered a kitset ?
it would substantially save in cost and would include a PCB for mounting the parts
there are good kits available in my part of the world... maybe yours too where-ever that is

here's the front end of a mixer that I have built just to give you an idea of complexity that gives you some of the features you want. quality, 8 input, phantom power .... line and mic inputs

Dave

 

[Mike F]

First if you don't have a degree you are NOT an Audio Engineer or Electronic Engineer.

You have a good list of questions. Get books that cover all those subjects.
Don't expect others to teach you all that stuff.

Read electronics parts catalogs. Learn what each part does. Learn what the specific terms mean and how they relate to each other.

Then when you open a piece of equipment you can understand what each part is. Learn to read resistor color codes, recognize the ratings of resistors physically. 1/4 watt, 1/2 watt, 1 watt, 2 watt, 5 watt.
Buy the best VOM (volt ohm meter) you can afford and learn to use it.
When you can afford it get a Scope (oscilliscope) and learn to use it.
Some times you can find useful affordible test equipment in a Pawn shop. The caution there is being able to recognize junk from something usefull. Not likely that the Pawn shop clerk will be able to tell you much more than the asking price. You might be able to negotiate a lower price if it's gotta lot of dust or faded price tag on it. That indicates that they've had it for awhile and would be glad to see it go.
The difference between price in instruments is durability and accuracy.

Buy books, search at your local city or school library. Read voraciously.
Don't hesitate to ask questions of someone who obviously knows what they are doing. If you see someone repair something successfully ask them to share how they recognized the problem. Be sure that you tell them you are trying to learn so they won't think you are doubting their abilities and judgement.

Have fun. Take pride in your sucess. Learn from your failures. There are NO stupid questions if you are really trying to learn. The person you are asking wasn't born knowing the answers. He had to learn it someway.

Mike...
a life time of broadcast Radio, TV and Manufacturing knowledge and experience.

 

[davenn]

this resurrected 8 year old thread closed

@Mike F tis usually a waste of time reviving VERY OLD threads the OP in this one never came back after his 2010 posting

Try and avoid resurrecting old threads


thread closed