Mar 12, 2007 - Building a Mic Pre

I'm starting a project build of a tube mic pre.

I've been playing guitar through a tube amp for awhile (67 super reverb), and am very fond of the tube sound. I'm also building a studio in my basement, and started thinking that my pre's on my yamaha board are a little too sterile and clinical for my taste, at least for vocals and acoustic.

So I went looking for a tube preamp schematic. Building a few guitar amps, the preamp section seemed pretty simple, so I figured I should be able to find a mic preamp that was similar, but built for mic usage. It was not so easy to find a simple build.

Over on the reaper board I was posting my dilemma regarding hard-to-find tube pre schems, and someone over there posted this:

http://www7.taosnet.com/f10/micpre.html

This is a preamp with parallel triodes, feeding a mosfet source follower. The writeup on the page seems pretty stable, and the builder seems pretty knowledgable, and was very impressed with the preamp, so that was my choice. Plus, it's not overly complex, like some of the other tube preamps I've found.

Now I had a choice picked out, I need to get a build design. The builder used a PCB, home-made, I'd assume. I haven't done home-made PCB yet, so I decided to pass on that idea. I'm more inclined to persue the point-to-point layout, or an eyelet board. Seeing as how I already have an eyelet board from a previous not-built-yet project, I decided to use that.

Here's a layout of my plans so far:

* image removed due to layout changes. new one coming soon *

This isn't totally proofed, so don't think this is a perfect layout design. This is just what I've put together so far. I'm pretty confident with it, but I have to go over it point by point, to make sure I don't have any logical mistakes.

There's no power supply on the layout, or the schem. I'm creating one on my own, using duncanamps.com power supply designer II.

I've designed one using a hammond 270x power transformer, which provides 240vac per side, as it has a center tap. This xfrmer should give around 310vdc rectified with a bridge, full wave, or tube full wave rectifier. I've not decided which I'm going to use, but I'm leaning towards a solid state rectifier, but not firm yet.

The input transformer is a jensen, which I purchased directly from jensen, for 73$. This is the highest one piece price of the preamp. The power transformer I purchased from stf-electronices, for 39$, i think. The components (res, caps, etc) I purchased from mouser.com, as they have a nice project manager function, which you can build up the parts of a project, save it, and come back later. I purchased 2 of all the components, so I can easily build up a second preamp, if the first one goes well. Then I'll be set for stereo. The power supply can power both sides, as preamp tubes take very little current, around 5ma or so, so I'm set there. I'll just have to purchase another input xfrmr, and I'll be ready to go.

I don't have a case / chassis figured out yet, but I will pretty quick, as most of my parts have shown up, so I'll be starting to populate my board pretty soon.

More later.

Jul 21, 2006 - More studio news

The studio is still moving along. The control room is done; primed, painted, and the electric works. I've now moved my modest PC stuff in temporarily. I've not installed the floor yet, as there's still construction going on in other areas.

I scored some laminate flooring from HD that was marked down a bunch. They were trying to get rid of a gun-stock walnut finish stuff. Price went from 65/box, down to 53/box, down to 40/box. Right up my alley, it was. I wouldn't have picked gunstock finish, but this stuff is the best laminate they sell, so I won't be too picky. Plus, they had only 5 boxes left, which is exactly what I needed, so there's a little kizmat going on there.

My small bathroom is done; drywalled, mudded, primed and painted. I had some vinyl (lino) left from my house bathrooms, so it went in there. Not quite the same decorating theme, but it's free, so what're ya gonna do. I'll take free. The toilet is in too, so I now have a working bathroom in the basement. Whoo-Hoo!

I've now put up the clips and channel in the iso room. ALso, I've put up the sound barrier, so I'm ready for wood planking now. I'm cleaning the planks, getting them ready to be put up. Should be this weekend.

The live room is planked, and is ready for caulk and drywall. I'm getting the iso room done first, then I'll drywall the two rooms in one swoop. Hopefully I can get adequate help, as 5/8" drywall is mucho heavy, and difficult to work with.

pix to be forthcoming, probably in my photo gallery.

May 08, 2006 - Studio's moving along, equipment is up and running

The studio is moving along, though not as fast as I had planned (does anything?).

The control room has been drywalled, as mentioned, and the mudding is mostly complete. The sanding has commenced, and moving along well.

The live room has been worked on pretty steadily, if only an hour or so a night. I've received the materials from SIC, and they're being installed.

The ceiling has been covered by the 1/8" sound barrier. Man, was that a challenge. That stuff is heavy!. Anyway, it's up.

I then installed the clips and hat channel, and have installed the ceiling planks. The clips and channel were easy and quick to install, and the planks weren't so bad to install. Not nearly as bad as the sound barrier was, nor as bad as the drywal will be. ugh.

I'm installing the clips and channel to the walls, and should be done with that, and hanging planks on the walls this week.

On to the equipment! I've received everything (see profile), and set it all up for a test run in the open area of the basement (the control room is under construction). Mostly I just wanted to make sure all equip is running properly, and no DOAs. Everything is running as expected, so there's no suprises.

On a good note, I hooked up 4 mics (the new condensors) to test mics and inputs. I was recording at 24bit, 88.2khz. I recorded 3 sets of 4 tracks each, of me snapping my fingers.

After playing back all 12 tracks at 88.2khz, the PC was only running around 20% CPU. So I'm pretty stoked about that. No clicks or pops to be heard either. So I think I have a winning combination with the PC hardware (see profile).

Mar 31, 2006 - Some news

Well, the studio is moving forward. I've gotten drywall up in the control room, and am mudding and finishing this weekend. I'm pretty happy with the way it turned out (pix soon in gallery).

I've purchased the materials from SIC for the live room: 1# barrier, and isolation clips. Hoo-boy, it's not cheap. They should be showing up next week. Hopefully, the control room will be primed by then, and I can start right into building walls in the live room.

I just purchased a bunch of replacement equipment: microphones, monitors, mixer, and stands. It won't be shipping till next week, but it's at least ordered. I'm purchasing early, as the studio isn't ready for equip yet, but I'd rather get it while the gettin's good. I figure if I leave money in the account, it'll have a tendency to walk off to other areas, so I'd better use it for it's intended purpose while I got it.

I chose to replace the SP B3, but also add a SP C1 for vocals. The B3 is a good 'other' LDC, for a bunch of things, while the C1 is very well regarded for vocals.

I also am getting a pair of Rode NT5 SDC. I needed something for OH, plus good acoustic recordings, so there you go. My sales guy went through a list of sets, and that's the one that won.

I'm getting a powered set of tannoy reveal (not the new ones). I had passives, and was pretty happy, and my equip house has them for a good price, so I'm going with them. I won't need the power amp now, so that's good.

The mixer is yamaha mg16/4. I had one before, and no reason to change as it was workin very well for me.

Stands aren't so exciting, but i needed some, so there you go.

Dec 16, 2005 - Pictures

Here's a list of pix so far:

Print of the basement


Print with studio dimensions


Temporary computer area (in control room)


Room after framing outer studio wall


Pencil layout on floor, they're not perfect, i had to adjust to fit into pipes overhead


Control room wall pencil layout


Back of live room


Isolation booth window, mic wire payout


Control room wall w/ windows




Isolation Booth


Mic wires in ceiling joist


Mic faceplate location


Wires installed, starting insulation




It's been slow going, with Christmas coming, should have more to show in a month.

Dec 06, 2005 - Studio is taking shape

We're moved into the house, as of end of October. There's been a ton of work to do, getting the house finished, so the studio wasn't a priority.

Nonetheless, I've been able to start the building process in the basement, putting up walls, and some of the insulation. I've installed the wires, so I can have mic and headphone cables out of the way, putting the faceplates on the wall, and burying the cables.

A few thoughts about the cost.

First step is the framing. I purchased building material earlier, for the framing. I figure it was around 250$ for the wood, and another 20 or so for the nails. After I exhausted my inaccurate amount of material, I purchased more for an additional 200$ or so. So I figure wood / framing material to be around 500$.

Second step, I then purchased 500 ft of 22ga mic cable to be used for in-wall cabling, my patch cords from my faceplates to the mic, and from the faceplate to the mixer in the control room. I'm going to have 3 4-position faceplates around the live room, plus 1 2-postion faceplate in the isolation booth. I'm also going to have 3 2-position headphone faceplate in the live room, plus 1 2-position headphone faceplate in the isolation booth. This makes 8 2-pos hp plates, 3 male 4-pos xlr plates, and 3 female 4-pos xlr plates. Plus I got 15 male neutrik xlr jacks, and 15 female neutrik xlr jacks. Also I needed solder, and a meter. This outlay was around 450$. I got most of the stuff from parts express, but 3 xlr plates I got from sweetwater, cause they were 6$ cheaper each.

Third, I purchased pink insulation batts, like the ones you put in walls, R13 on 32 ft rolls. Home depot had them for 9.44 each, and I picked up 26 ( i think). This brought the insulation to 250. I don't think I'll be using all the insulation, but HD was running a rebate on 250$ + so I got enough to get the rebate (75$ HD gift card).

I picked up the window glass on my way to work one day, someone was pitching some large 3 panel windows with storms in the frames. I grabbed one full set (around 5ft wide) with the frame, for a different project, and grabbed the second set of just the window inserts. I'm going to be using them for my windows, doubled up. They are 26 x 32. I'll be using 2 pair for my control room -> live room, and 1 pair for control room -> isolation booth.

I must admit, this is a large undertaking. At first, you think this will be pretty simple, but not being a full time construction worker, plus having a new house, family and holidays, it's going slow. I try to work on it at least a little every day, but it's hard.

Anyway, I'm set on using the Sound Isolation Company's products. They offer sound barrier - 1/8" 1lb - that is somewhere around 28stc by itself. I'll be putting that barrier all around in my live room, on the studs, covering my insulation. I'm also going to be using their SIC clips, plus hat channel that lives in the SIC clip. This will make my second wall, inside of the normal wall, thereby isolating my sound from the outer wall structure. I don't have any $$$ figured out for the SIC stuff yet, but will soon, as I need to get this studio finished to get our C of O. Fortunately, the missus is on board to get this finished, and the next few months should get it complete.

Pictures to follow . . .

Sep 09, 2005 - House showed up!

The house is now in place. I've decided that I'll be building the framing and the skins, as it's too $$$ for my general to do it. I've done construction before, so it shouldn't be much of a problem. Probably just slow.

Anyway, I'm figuring material now, so I know what I'll need and how much it'll cost. Hopefully I'll get some pix up on my webspace shortly. I've got pix but they're not up yet.

I've decided to avoid the quietrock approach, as I've seen a few forums where users said they didn't like it, and were not impressed with the results. I believe I'm going to work with Sound Isolation Company, utilizing sound clips, hat channel, isolation pad (thin foam), along with my planking and sheetrock. I'm pretty confident this direction will give my desired results, but am not sure of the cost, so I need to figure it out.

Aug 08, 2005 - My run at rebuilding my studio: bigger & better

This will hopefully be a running archive of my studio rebuilding: bigger & better.

I experienced a house fire in dec 2004, which took the whole house. Even my basement studio was not spared, as water has a way of finding the lowest point (stoopid gravity) and soaking all my equipment. Add to this the floor caving in, and the -5f temperature, this makes for useless equipment pretty quick.

On to the insurance company. I shouldn't have a problem replaceing everything I had (see my profile) but I am now going to attempt to build a somewhat soundproof studio / practice room in the basement. The old house had 2 rooms dedicated to wood storage and heat, so I can now utilize that space for music. The wifey has green-lighted my ideas, so I'm good to go there.

I'm planning on tearing down my old practice room from in the garage (see www.kondratko.com for pix) and re-using that planking for my wall structure / skin. I'm planning on adding a layer of drywall as well to make the walls more mass-intensive and dense.

I'm also planning on creating a second set of walls/ceiling to isolate myself from the rest of the house. I'm in the planning stage of this, so I'm sure more developments and ideas will come in the next few months.

As far as actual building, my house is getting the footings / basement plumbing / foundation done this week, so I won't be actually constructing until october at least. Hopefully I'll have more info before then.