Component Advice

[as_ad]

Hi there, I'm about to embark on my first project(Green Mic Pre), and I had a few questions. When buying all of the components(caps, resistors,semi-conductors) which brands/types are better than others when it comes to sound quality? Also, when building the power supply, are some transformers better than others? Thanks a lot,

David

[Kev]

I don't think you will have any problem here.

Resistors. 1% metal film will put you in good company. I'm not going to get into a Carbon verses Metal film argument. Al I'm saying is, if you use 1% metal film the circuit will work as expacted and the noise due to the resistors will be low.

The 6.8k phantom resistors must be as close as posible to the same as each other. 6.7 or 6.9 is not the point but they BOTH have to be the same.

Capacitors. The modern RB style used in this project are all good. If you chose a low-leakage 105 degrees modern cap you will be fine.

The ferrites are just little cylinders that I put a resistor leg 'off-cut' through the middle of.

Power Supply. I have a power supply in the works that should be fine for this project. See Group DIY. In the mean time volt batteries can be used as a clean and stable power supply for both the main power and the phantom.
my site for details or I can explain later.

good luck. This is a good beginner project.

[HiString]

Kev and as_ad,

I too am working towards the Green mic pre as a first true DIY project.

I contacted Peter C re the power supply and he directed me to; http://sound.westhost.com/projects.htm#index

And Kev, I will probably email you somewhere down the track as get myself organised with this...........currently spending my time tracking my son's band and building a new PC specifically for the audio mixdown and CD burning.

I don't supposed you have any spare pcb's for the Green :D

Regards,

ChrisO

[kent]

Looks like a bunch of us are doing the Green Pre. I noticed several bypass caps & 10R resistors on the PCB vs. the schem. Are these necessary or what's the deal?

kent

[peterc]

Hi there

Aaahh! Feedback!

The 10R / 47uF combinations on the PCB but not on the schem are de-coupling filters for each of the opamps. I was trying for a very stiff supply for the opamps, so I used 47uF caps in place of 100nF caps.

I will update the schem on my site.

GO FOR IT

Peter

[Kev]

I think this is one area I did like about Pete's Green.

I do like the idea of the R/C on the power supply to the op-amps. You can see on all my op-amp base circuits I use a 33ohm and 10Mf tant on each pos and neg power leg of each op-amp. It is like a mini pwoer supply for each building block. True it may not be necessary and it does add to expense BUT I am convinced it lets each op-amp run as you intended it to. Even if one op-amp is stressed the others will be happy.

All of this adds to a more stable, cleaner and with as much headroom as the circuit will allow.

The 33ohm or Pete's 10ohm will also act as a fuse if you put the elect/tant in backwards.

[as_ad]

OK, so I spent the day digging and reading about caps and resistors. I just wanted to make sure none of this was blatantly wrong.

Caps-

-Panasonic FC electrolytics-25V and 63V when needed

-I'm completely lost as to what to use when electrolytic is not explicitly defined. What do I use for best sound? I think I read about a Massenburg interview where he said that tantalums made the sound warmer...although I'm not sure that's the goal here.

Resistors-
-I forget where I read it, I think it was some audiophile page, but some guy was saying that he thought Vishay metal foil were the best. Mouser has these, but I don't know which wattage to buy. 1/2,1/4,1/8????

Semiconductors-
-Mouser has a NE5532N. Works for me.
-Mouser also has a BC550C, but alas, the minimum order is 1000. I tried ordering a sample from Fairchild, but I guess they don't offer samples of that particular piece. Any ideas?

Misc-
-I randomly picked the 1N4744A out of a list of 15V zeners. Will this work? Is there something better?

-I'm confused about the ferrite beads. Peter told me he doesn't use them. If I can gain a little quiter operation, I'd just as soon use them. What impedance bead should I order?

[HiString]

Peter and Kev,

Re the power supplies you guys are using for this mic-pre.................how many mic-pre modules do you think your respective p/supplies would operate successfully? e.g; If I wanted to make an 8 Channel mic-pre unit, what would be a safe option in regard to power supplies?

OK, I know it's probably a naive newbie question, but it is something that has been bugging me

ChrisO

[peterc]

In Circuitmaker each stage measures about 14mA per side, so about 60mA per channel in total. Work on 100mA for a bit of reserve & headroom per channel.

Peter

[Kev]

Guys ,
don't get tied up in knots over component choices.

I'll post a picture of my Green so you can see for yourself what things look like ... I hope this will help chose a cap.

I do understand that caps are often the most difficult to work out what the designer had in mind. Things in the cap world are changing as things get smaller. Working in our favour is generally all electronic components are getting better and smaller and with closer tollerances.

The power supply question. My new one is probably not for 8 Mic-pre's and I suggest you don't make 8 in a box. We do have a plan for 4 or 8 in a box so wait.
(this infomation leak was brought to you by Group DIY) :D

For 4 in a box have a look at,
http://recording.org/users/kev/mic_pre_general.htm
look for Kev's Quad Mic-pre.

Don't get too many of the one type of Mic-pre ... UNLESS you have a specific job to get through , like a live recording.
If you own a small group of equipement, keep a variety rather than a large number of one thing.