December – March updates

Nothing fancy. Worked this week on an Aria Precise bass (a P-Bass knockoff). It’s a pretty neat bass, but needed a new volume pot and I felt like the neck was weird – I ended up maxing out the truss rod for acceptable relief.

I also had to replace the pickguard on that bass (owner wanted a different flavor, is all), and that required a lot of filing, scraping, and sanding to get it to fit right by the neck and over the pickups. A razor blade with a burr works really well for scraping here. Files are not great. The best tool for getting the pickup openings right is to take one pickup cover, put sticky sandpaper around it and use it to shape the openings. This maintained the right radii of the corners.

I also set up a friend’s Guild M-120. All Mahogany, made in China, and it sounded and played great. Fretwork was pretty much excellent, and the neck is straight with a very responsive truss rod. For that price, you really can’t go wrong with those guitars.

Also re-wired an EV RE 664 with an XLR connector and at the same time eliminating the Hi-Z output. I’ll make a post about that later.

I also finished (in December) my second rack. It turned out pretty well, about as good as the first one did. I had a few mishaps, the biggest of them was that even though after I dry-practiced for more than 5 times, when I came to glue it together, things weren’t square so I had to take it apart while the glue was starting to set. It was incredibly stressful and I had to clean the glue out of the joints with a lot of water, which warped the the wood a bit, but like I said, it turned out fine. I’ll probably write a whole post about the new rack, but for now here are some pictures:

 

Also worked on a few other guitars in the last few months, as well as my own Stratocaster. I “inlayed” a piece of mahogany in the neck pocket:

Also leveled its frets. Also it probably needs a new nut.

I’m also building some drawers for my works area, but more on that when they’re done next week hopefully. Maybe I’ll write a whole post about it.

That’s pretty much it other than little jobs.

Advertisements

Re-foaming Beyer M380

I’m lucky enough to own two Beyer M380, and since they’re both probably over 20 years old, their foam needed to be replaced. In one microphone (gold M380) the foam was almost completely gone, but for the other it was more of a precautionary measure – the foam had holes in it, but wasn’t exposing the whole capsule. Anyway, these guys can go bad if even a small hair gets in the capsule, so it’s a good idea to replace the foam as soon as it starts showing signs of breakdown.

Greg from Electrical Audio tipped me off to McMaster Carr and said to search their website for “the thinnest Reusable Polyurethane Foam Air Filter”. It’s this one, and in case the link goes dead in the future, the catalog number is 9803K301. The thinnest one is 1/8″ thick, and that’s the same thickness of the foam that’s already in the microphones.

The next question is the porosity, 30 or 60 pores per inch? I got both and compared them to the existing foam in the microphone. The answer is 60 PPI. See for yourself!

The difference between 30 and 60 pores per inch is very obvious:

One sheet was enough to re-foam two microphones with some extra material left over.

There’s really not a lot to it once the microphone is open. One side the body comes off completely and the other is holding the capsule in place with a couple of screws.

I started on the gold microphone because its foam was in worse shape. However, it was deteriorating so badly that I couldn’t use the old foam as a template. So in retrospect, I should have started with the black M380 whose foam was in a better shape. Anyway, it took a bit of experimenting to figure out how to cut the foam. Like I said, it’s better to use the old foam as a template, but if it’s in rough shape, start with a square that is bigger than the grill. Fit the square of foam in the “tub”, and cut the four lines for the corners. Now the foam is overlapping at the corners and need to be trimmed. This is kind of tricky and here’s what I learned: the body of the mic has these vertical slats, right? They go all the way around to the rim of the tub, so if you cut to much foam along the length of the tub, you might leave holes in the foam that overlap with a slat. That’s bad. So the trick is to cut the excess at the top and bottom of the tub. Also, make sure to first cut the lines for the posts where the screws go in. Anyway, that’s basically the only tip I have for how to actually cut the foam. Here are a couple of shots of how my foam pieces turned out.

And the two M380s fully re-foamed.

 

Old foam (from the black M380):

img_20160915_211949

Important: Don’t try to glue the foam to the grill, that’s not how it’s supposed to be and the glue will probably eat the foam. When I got my black M380 I was dumb and decided to glue it to the grill, and when I re-foamed it I had to clean out a bunch of old gunk. It sucked.

(This was done in September, but I only now remembered to post about it)

Overheads and room mics mixing and recording thoughts

As I’m mixing things that I (and others) recorded I notice that sometimes the room mics and overheads are unbalanced.

For instance, with overheads, the snare can be a little off-center, and sometimes even the kick is leaning to one side more than the other. I usually place overheads as a spaced pair and not in XY so the overheads really are just there to capture the cymbals. However, because the OH are a spaced pair and are positioned above the cymbals, the kick and snare end up off-center. It’s probably possible to place a spaced pair so that they capture the cymbals but the rest of the kit is still balanced, but these things can be fixed in mixing too. A high pass at around 250Hz would basically eliminate the kick, and a really fast compressor will work to eliminate the snare from the overheads without washing out the cymbals.

I noticed that some of my room mics have a similar issue – the kick and snare aren’t centered. The way I almost always position the room mics is on the floor and so that they create an equilateral triangle with the kick. This should guarantee that the kick is centered, but I guess sometimes the microphones aren’t symmetric with regards to the kick. However, this positioning will always lead to the snare leaning to one side or the other. Since the room mics serve as a full image of the drum kit, this isn’t something that can be fixed during mixing. So maybe a better method is to keep the microphones symmetric along the line that runs between the kick and snare. One way of doing that would be to position the microphones in front and behind the kick. Another is to have the microphones in a non-equilateral triangle formation.

With all this being said, I haven’t really noticed the drums being asymmetric once the close mics are brought up, so maybe this isn’t something that a lot of time is spent on during quick sessions.

Grounding and Rane Note 110

I made a cable to connect my Kilpatrick PHENOL, which has unbalanced outs, to my recording interface (MOTU 16A) which has balanced inputs and outputs.

I’ve read Rane’s note #110 about interfacing unbalanced lines with balanced a few times and thought that I’ve internalized it well at this point. I followed no. 14 on their diagram and made a TS to TRS cable, but when I plugged the cables in I got a pretty nasty 60Hz hum at -60dB. At the same time TS-TS cables work fine and their noise floor is at -110dB!

The PHENOL is using a wall-wart and is therefore un-earthed and floating. This means that its enclosure (and therefore its audio ground) is one big antenna. Feeding that antenna to the balanced line’s “-” injected all that noise into the inputs of the interface. According to a friend, Rane note #110 is only applicable when both devices are earthed, and that makes sense.

 

Shellac vs. Tung Oil

I promised to write about Shellac and tung Oil after I finished my rack (the first one), so here it is. I should mention that this post is not about which finish is better as much as it is about my experience with each one.

Tung Oil:

I got the idea to finish my rack in tung oil from a friend who builds Dietz cabs out of baltic birch ply and uses tung oil to finish them. When I was looking into tung oil I learned that there are two kinds of tung oil. One kind is really a varnish, like Fromby’s tung oil, or any other kind of tung oil you can get at the hardware store. Then there’s real tung oil which is an actual oil, made from a nut, and needs to be cut with citrus solvent or it’ll never dry.

The varnish tung oil is fine, but it’s made of chemicals that are toxic, and if you can’t finish outside or in a well ventilated shop, then you really shouldn’t use it. That’s why I went for the real tung oil which is made of safe materials. The one I bought is made by Real Milk Paint, and I really recommend them if you’re looking for actual tung oil. You can call them and they actually answer the phone and answer whatever questions you might have. They recommend using citrus solvent to thin their oil, but being a cheapskate I thought maybe 99% isopropyl would work, and they were positive that it would. Honestly, I’m not sure it did. I think it did, because the oil seeped into the wood, but this was my first time using tung oil, so who knows.

I wasn’t happy with the way the finish turned out. I think some finishes and some woods don’t work well together, meaning that the finish brings unattractive colors out of the wood. That’s what happened with the tung oil and Baltic birch. The wood looked unnaturally yellow and orange, and the grain popped out but in a weird and unflattering way. This was a surprise because I tested the oil on a scrap piece and it looked find, but I guess I underestimated what it would look like on the whole thing. Here are a few before and after pictures.

As you can see, it’s orange and yellow and the edges look burnt. It doesn’t look as bad in the first three pictures with the oil on, but in the last one, which was taken under a lower light, it looks pretty bad, but even that is quite flattering. Notice the little shelf in the bottom of the last picture. It was made from the same slab of birch plywood, but it didn’t have as many layers of tung oil. I’d like to elaborate on that.

Fewer layers of tung oil will result in the piece looking less orange and yellow – just look at the rack vs. the shelf. The shelf looks better because it didn’t have as many applications of oil. It’s also important to keep in mind that tung oil is, well, an oil. This means that while it’ll protect (and seal, I think) the wood, you will still be able to feel the grain underneath. It’s not a clear, hard finish that comes between the wood and the environment, so think of what you’re making, its application, and whether or not tung oil would work for it. I wouldn’t hesitate to use tung oil on a cutting board, wood bowl, wooden spoon, etc. At the same time, a coat or two of tung oil could be nice to use under another finish just to give the wood a bit of a color and help the grain pop.

Keep in mind that tung oil has a really strong smell. It’s a nut-like smell, but it’s really strong and our apartment smelled like it for a while until I washed the floors a couple of times and kept airing out the place. It also helped when I moved the rack to the basement. My understanding is that the citrus solvent will work to counter the smell, so if you were to use tung oil on something that needs to be food safe, it’s a good idea to use citrus solvent. In fact, I’d use it anyway.

Shellac:

Kind of like tung oil, there’s the stuff you buy at the store or you can mix your own. The Zinsser product, which is available everyone, is fine. It’s a bit thick (I think it’s a 3lb cut), but worse they put a lot of stuff in it that’s harmful, so again it’s not a great idea to use Zinsser shellac inside and without ventilation. I actually got woozy from applying it at home even with the windows open. Then I read the GHS document for their shellac and god really scared, so I decided to get flakes and mix my own shellac. (I got my flakes from shellac.net).

Mixing shellac is very simple. You crush the flakes and mix them with alcohol. The ratio is determined by the kind of cut you want. The higher the shellac ratio, the thicker the solution will be. The solution should be kept in a plastic or glass container, but not metal. Most people use denatured alcohol, but since it’s toxic, I decided to look into 99% isopropyl alcohol. No one seemed to be able to answer whether it’s fine to use it with shellac, so I went ahead and mixed a small amount and the answer is YES, it’s fine to use 99% isopropyl alcohol to mix shellac. It has to be 99% IPA, though. 91% won’t work because it has too much water in it.

As far as application: I tried applying shellac with a brush and it’s a pain, mostly because I get brush marks on the wood and can’t seem to apply it evenly. It also comes on too thick. So instead I went the route of French polishing, which is really not as hard as people make it sound. I use a cheesecloth wrapped in cotton fabric (old sock, old t-shirt), I get a bunch of shellac on it and rub it on the wood in circular motion. I don’t think the motion matters as much, and I’ve seen people go in straight lines; the important thing is to make sure you never leave the applicator in one spot because it’ll stick and mess up the finish. People also seem to use some kind of oil to lubricate the applicator and that seems like a good idea – I tore a hole through my sock applicator. I use a 1lb cut and I really like it because it’s so thin. In fact, you won’t see a difference after the first application or two, but it’s worth it because it looks really nice and even at the end.

Staining shellac seems to be something that people do, but it hasn’t worked for me. It doesn’t seem to make a difference when French polishing, and even with a brush it barely changes the color of the wood. And I’ve put a lot of dye into that shellac! It was practically black! However, I saw a video of Paul Sellers applying stained shellac, and his looked pretty thick (and also heavily tinted), so if you’re after staining shellac, a thick cut would be a good place to start.

Edit: Shellac dries to the touch within minutes. Probably even one minute. However, it’s still soft for a few days, so if you place items on your shellaced piece, those items will leave marks. I let my rack dry for a long weekend, and after that I was able to put stuff on it and it was fine. I didn’t let my shelf dry for more than a day, and after that long weekend it had marks all over it.

Making rabbets with a router

I’m making another rack. I promised I’ll write about the finish of the first, tung oil, and shellac, and I will get to it eventually, but I want to write this before I forget.

As I mention in the rack post, all the joints are rabbeted, and with the first rack I did some with a table saw and a dado blade, and then some were impossible to do on the table saw, so I did them with a router. Also, the dado blade was tearing out some wood, so it really makes sense to do it all with a router. Here are my best rabbets:

Some aren’t as pretty and smooth but they’re pretty close, and with the glue and the piece that goes in the joint, it’ll all be invisible. These were done separately, meaning that the long edge was done first, and then the shorter one. I then squared the rounded corner with a chisel. I thought I took a picture, but I guess I didn’t. It came out pretty well I thought.

So here’s my method for making rabbets, but before I get into it. Yes, it’s safe to use a router on Baltic Birch plywood. I do not know if this will work with regular hardware store plywood, and I don’t know if it’ll work on Oak plywood that has a very thin top – I can see that tearing like crazy, but it works very well on the Baltic Birch, as you can see.

Width of the rabbet:

Pretty self explanatory, it is the horizontal distance in the pictures. I hemmed and hawed about how to set that distance in the best way, and here’s what I came up with. I measured the distance from the edge of the router base to the edge of the bit. It measured exactly 2.5″, and I’m sure it’s specific to this router (Porter Cable 690) and bit. So if I set my guide/fence at 2.5″ from the edge of the piece, then the bit will just slide along it. So now I add the thickness of the piece of birch. This birch is pretty close to being 3/4″ thick, but it’s not – it’s about 0.715″. Now I add the two measurements together (2.5″ + 0.715″ = 3.215″) and set my digital caliper to this length. Then I use my caliper to set the depth on my adjustable square. So basically, I use the caliper like I would measure depth (of course the measurement is locked in) and adjust the square so it’s perfect. Then I make two shallow passes with the router and check if the width is right by placing a piece of birch on it. I like it to be dead on (it almost never is) or for the piece to be a little shallower than the edge of the rabbet. So if the piece is really 0.715″ thick, then the width of the rabbet is maybe 0.715″. The excess can then be trimmed away with a flush bit with a ball bearing.

Depth of the rabbet:

First and foremost, do multiple shallow passes. I probably do 5-10 passes to get the depth. Try and remove a 19″ stretch of 3/8″ thick of Baltic Birch in one pass and your blade will dull and your joint will suffer.

I set the depth like I set the width. Measure 3/8″ on the caliper, and copy that to the square. My first rabbet will be exactly that and I’ll measure how far the bit sticks out by placing the square on top of the bit and see how the ruler end touches the base. When I have rabbets that are a corner, I do one edge first (mentioned that earlier), and make it 3/8″. Then for the depth of the other end of the corner, I just keep lowering the bit down, and I see how it sits on top of the rabbet I have already done. Obviously, power is off and the router is unplugged. I keep comparing and I like erring on the side of caution, meaning that it’s ok if the new edge is a little taller.

18U Rack

I think I may have mentioned it before, but I’ve built an 18 space rack. It took a while to complete, and I’ve finished it over a month ago, but since then I’ve been wasting a lot of time finishing (I’ll get to that later).

This video is a good place to get started. Even if you don’t follow their plans (I didn’t), it’ll at least give you an idea as to how it should be done.

Here’s what mine ended up looking like:

I used 3/4″ Baltic Birch plywood, and all the joints are rabbeted as you can see from the pictures. There are three aprons – two on the back (top and bottom) and one on the front. The aprons are allĀ 19.875″ (19-7/8″) long and 3/4″ thick, but their heights are different: The front is 2″, the bottom back is 2-3/4″, and the top back is 2″. I used the birch for everything except for the rails (see below).

Top to bottom the rack is 35″ tall, and the opening on the front is 32.25″ tall. This is slightly larger than 18U. The way to figure out the opening is using Pythagoras Theorem. One side is 3″, another is 33″, and the hypotenuse (the diagonal opening) can be figured out from there. The angle of the slant can also be figured out using inverse sine, cosine, or tangent, but it isn’t necessary to know if you don’t care to know the angle!

As the pictures show, the front of the rack is slanted. I made the top 16″ deep and the bottom 19″ deep. The length of the diagonal can be figured out with Pythagoras Thereom, where one side is 3″, another 33″ The angle can be figured with a trapezoid calculator, but it’s also not really necessary to know. The bottom front apron is straight and not angled.

For the rails I used White Ash. I got a piece that was 7/8″ thick and almost 3.5″ wide. I cut it down the middle to make the two rails. Maple would work also. Anything that really hard and durable would be good. Some people use metal rails. I prefer wood, especially since I don’t want any ground loops.

The distance between the two sides is 19-1/8″. At 19″ some equipment might not fit in. This is very important!

I used pins to reinforce the bottom and top to the sides. Odd number of pins is more appealing than even. The pins are walnut dowels that I think are about 3/4″ long. Don’t use too much glue or the pins won’t go all the way in. I drilled for the pins after everything was glued up and assembled.

For gluing I used Titebond II. I honestly didn’t put a lot of thought into it other than this is the glue that the carpenter who runs the woodshop uses. It has a relatively short open time. Titebond III seems to have a longer open time and is supposed to be stronger. Maybe I’ll use it on my next project. Generally speaking, though, for a project like this, I think it’s better to stay away from a water-based glue.

I have a lot to say about the finishing. Basically right now my rack is wreck cosmetically and I’m very bummed about it. I’ll write a separate post about it later.

Some tips:

The Birch’s sides aren’t the same. What this means is that you want all the outside piece be from the same side of the birch. When I selected the birch I went for the stuff that’s the least warped. Then when I cut the pieces, I chose what would be the outside according to whether or not I liked the grain and if there weren’t any patches. If you’re going to the store to get some birch, pick a sheet that doesn’t have any patches on one side. Also make sure you like all the grain patterns on one side. Why is this important? Because when you finish it, the grain of the different pieces will look different. For instance, the top of main has very tight lines, but the sides don’t have that. It’s a real drag.

Practice clamping. A lot. At first I didn’t think I’ll be able to clamp it all up in under 5 minutes, but after 3-4 practices I was able to get all the clamps on in about four minutes.

Practice clamping the way you will glue it. I practiced with the two back aprons on because it helped with the alignment. However, I didn’t want to glue them in with the big pieces (long story), so then when I had the glue on, I couldn’t align it as easily. It ended up working alright with a diagonal clamp.

Use a router for the rabbets and do multiple passes. This can’t be done with a table saw. Also, you will dull the hell out of the router bit if you try to cut a whole rabbet in one go. My rabbets were 3/8″ deep, so I did 3-4 passes and then squared them with a chisel.

Set the depth of your rabbets before you begin routing. This one is a little tough to explain, but I’ll try. Say you want the rabbets to be 3/8″ deep. So you do one pass that takes about 1/8″ of material, then another, and then another. For the last one you want to measure the depth of the bit, and the best way to do it is with an adjustable square. However, you won’t adjust the square just the right way every time. I think it’s best to set the depth once and keep it this way. So don’t use that square for anything else. Same goes for measuring the distance from the bit to the edge of the router. This is how you figure out where to put the fence for the router. Set it once on a square and put it aside. Some of my rabbets were too deep and some of my aprons didn’t fit right. That’s why you want to do all this. Also:

Maybe it’s better to glue it all up and make the aprons. See above.

Swanson Speed Squares are awesome. Get two!