/dev/toe

Ossus Amplifiers - Step 10, wiring and installation.

2006-06-26T20:17:00.000-04:00

Before I get started I have to admit that this entry is long overdue. The truth is that the amp has been finished and in fine working condition for three weeks now. I've been a bit pre-occupied playing it and doing some other fun stuff that I'll chronicle in future posts.
So, where were we when I last left off? Oh, everything was done save the electrical hookup and final install. The turret board was drilled and the turrets installed. The chassis was drilled out to fit the tubes, transformers, the pots (potentiometers for volume, bass, treble, drive), the switches, and the power cord. Next up, wires and solder.

I cleared off a desk in my place and set things up to do the work. I have a nice soldering iron, lamp, some mats, a good chair, and a nice stand that can hold things while I work.

Before I got started I had to peek at the face and rear plates that I had etched. Up until now I had not really seen the results. I was waiting to do the drilling first. Well, I'm very happy with the etching.

Nice eh? Seeing the face plate sitting there really pushed me to start the work on the electronics. I wanted to start slow, pick some easy things, things that I could feel good about and work up from there. So, I started by mounting the tubes and transformers.

If you took the time to drill out the chassis properly and accurately then the pieces should just slip into place. Me? Well, I had to use a grinder bit and some persuasive force to clean up the holes to a point where things fit properly. I wasn't too far off, but far enough to require some minor adjustments.

A view into the interior of the chassis shows how the wires from the transformers get inside via holes with grommets to prevent chafe. A photocopy of the turret board layout to scale fits properly in place inside the chassis so I placed the turret board in just to get a view of how things were going to work out.

Next I put on the face and rear plates. I did this using some automotive epoxy which was totally overkill. The cement dried rock hard (really, as hard as a stone) and did the trick. A good epoxy would have done just as well. At least I know that my plates are never coming off. Ever. With the plates on I could install the pots and switches. This was easy, but I did learn an important lesson. You can over tighten a nut and strip these little gizmos. Don't do that. Also, some pots had alignment flanges. If I'd know that ahead of time I might have set the chassis up to accept them, but its really just overkill for this project. Finally, the two 1/4" jacks were installed. A self grounding one in the front, a normal one in the rear. I should have looked for fancy flush mount plugs, but these look okay.
At this point I stopped for the day. I had done a good bit, next up was the turret board and I wanted to be well rested and alert before I started that work.

First off I laid out all the tools and parts I'd purchased for the electronics. I inventoried them against some printouts I had and felt good about having everything I needed to put things together. Well, to be honest I was missing a capacitor and a resistor, both on back order, but that wasn't such a big deal.

I used my fancy resistor lead bending tool and put in the first resistor. Right off the bat I knew that I'd never use that bender tool again. Its overkill and I'm the sucker that bought it. A good pair of pliers and some careful bending and you are done. So I placed in the first resistor and I marked the fact on two printouts I had and on the resistor packaging. In doing so I kept perfect track of what I'd used and where it had gone. This turned out to be a life saver later on in the project. First I'd highlight the inventory sheet. Next I'd highlight the part on the layout. Finally I'd write on the label on the part's packaging where I'd installed the part (resistors are names 'R' and a number like 'R1', so mark the package 'R1', capacitors are 'C' and a number and so on).

And so it went, part after part, left to right along the board. At this point there was no soldering at all. Just part placement. You'd think that the parts would fall off, but no they don't. As you place a part on the turrets you carefully bend the wires around the turret posts and so they become fixed to the board. Take the time to try to keep the amount of wire uniform on either side of items, that reduces noise. Also, try for symmetry as you place parts, again that reduces noise. Finally, try to layout items in such a way that you can see what the part is. Later in life someone will have to fix this amp and figure out what the heck you did and why. Make that easy now.

Again, I stopped for the day at this point. Note the highlighted layout picture to the right of the chassis. Without that I would have missed something. I placed the board into the chassis, still unsoldered, just to get a look not to mount it.

Now it was time to solder the parts to the turrets. I placed the turret board into my clamp and set things up. Gravity will help the solder flow into the wires at this angle. Use proper solder, not the cheap stuff. Also, have at least two head sinks and a few clamps. Use them on every joint to protect the capacitors and other parts from damaging heat. As you solder highlight the joints on the same diagram you were using earlier. Doing this will help you keep track of things.
Again I stopped for the day when I finished this stage. Its tedious and complex and there was no reason to rush.

The next big stage is to place the board into the chassis and then wire the components together and to the proper locations on the turret. Take your time on this, plan out the wires. Work in a pattern. I worked clockwise starting from the power switch and heater wire on around. Some of the tube hook ups and complex pot wiring I left for last so that I would have time to hone my soldering skills. Again, as you wire things up highlight each wire. Do one wire, highlight it on the picture, then plan out and do another wire. I used solid core 20 gage wire for the hookups. I used 20 gage stranded wire with teflon insulation for the heater wire (the black and green twisted wires) as someone told me that was the best combination for the least amount of noise. There are two resistors on the turret board that are optional if you choose to ensure that you keep your heater wire lengths consistent with either an even or odd number of turns. I wasn't going to pay that close attention to that, so I kept those resistors in the mix.

It took some work to get the chassis to fit into the cabinet. Turns out that I'd made the tolerances a bit tight, almost too tight. There was a point where I considered building the cabinet over. Turns out some of the wood pieces shouldn't be glued in before the chassis is installed. Who knew? No one told me that. I made it work with only a few small sacrifices.
Amplifiers have a large amount of electricity flowing through them that can kill you if you do the wrong things. When I first started the amp up I used the trick of a modified plug with an inline lamp in one socket and the amp in the other. If the amp had a short the lamp would glow brightly. When I turned mine on the lamp didn't even flicker a bit. I was almost concerned that my test contraption was broken. I did a lot of testing for stray voltage. I waited a while for smoke or excess heat to show up, but there was none to be had. With that, I plugged in my guitar and let it rip. And it worked. Well mostly. It turned out that I had a short in one of the more complicated shielded wires from the drive pot to the turret board, but when that was fixed the amp sounded sweet and was much louder than anticipated. Much more than you'd expect from a 5-7 watt amp.

Here is the amp, lit up and running properly. Adjusting the drive can take the sound from Muddy Waters to the Scorpions. The amp has range and reacts in a very sensitive way to the particular guitar and the volume sent to it from the guitar. Basically, I couldn't be happier. I have a functional guitar amplifier that I'll keep forever. As a side note, my guitar teacher thought so much of the amp that I'm now helping him to build his own exactly like mine.

Technorati Tags: audiophile, diy, guitar, hobbies, music

Ossus Amplifiers - Step 9, drill and preparing for wiring

2006-05-27T18:57:00.000-04:00

This morning I said that I was going to try to get things ready to wire up, I think I'm there. I had a few things to get done. I needed to drill out the garolite turret board so that I could install turrets to which I'll solder the components. I needed to install the turrets. I needed to drill out the chassis top, front, and back. I needed to drill out the face and back plates too and match them up with the chassis. It sounds like a lot, but if you get things setup and ready to go it doesn't take that long, a few hours of work for me.
I went down to Ace Hardware on Charles street (its not a True Value after all, you'd think I'd know being such a good patron) and borrowed their full size large chuck drill press. I needed that because the step bit I purchased (from them for $44, yikes) required a large chuck press. I also needed the press to properly use the turret install tool and properly seat the turrets into the garolite.
Things went fairly well at Ace, the guys (and lovely college girls) who work there are getting to know me. Is that a good thing? I'm not sure it is.
The prep for the chassis top is to print out the plans at scale, cut them out of the paper to size, then rubber cement them to the top of the chassis. I did that and it turned out to be a perfect guide (I hope, I've not mounted anything yet, here's hoping that the holes are all in the proper places). Then drill things using the press and sharp new bits.
The prep for the chassis front and rear is easy, but needs to be precise. Take the etched face plates that still have their protective covering on and tape them (use painter's blue masking tape) one at a time to the chassis. Position them properly, make sure the front is on the front (or the back is on the back) and double check the hole sizes from the plans against the parts you have for those holes. When you have the plates etched ask for small pilot holes, not full size holes. Using the drill press drill through both the face plate and the chassis. This will make sure that things will line up later when you do final assembly. Drill slowly and decisively (using sharp bits!).
Installing the turrets was a breeze once I had put together and aligned a jig holding the turret install tool at the proper height. Just take your time, then go back and check to make sure that they are all snug.
So, now I have a chassis and a turret board ready for me to install parts and start the process of wiring and soldering things together. I've turned one of my desks into a work bench so that I can keep everything out while I do this. It'll also be a nice clean place to do the work.
Maybe I'll relax a bit over the holiday weekend and save this for another time. It was particularly nice out today while I was in Ace's basement working.

Technorati Tags: audiophile, diy, guitar, hobbies, music

Ossus Amplifiers - Step 5, 6, 7, and 8 finishing the cabinets

2006-05-27T14:38:00.000-04:00

As I sit this morning at my computer working on a second cup of coffee I have here beside me two finished cabinets.

In that picture you see my Gibson Les Paul Smartwood guitar leaning up against my finished products. the amplifier cabinet is on top (the smaller box), and the speaker cabinet is on the bottom. In the background you see my Yamaha CP-80 baby grand piano (It is circa the late 60s/early 70s, just today I spotted one in the music video for the song, "Video Killed the Radio Star," check it out if you don't believe me).
A note to the reader, you can enlarge any picture in my blog postings by clicking on it. Also, my camera seems to be having focus problems, I'm doing my best, but the images have been a tad fuzzy, my apologies.
The speaker cabinet is completely done. Both cabinets are constructed, covered in tolex (the black exterior is a plastic/cloth material with a rough texture customary on equipment designed for concert use), they have their front pieces covered in grill cloth (the cloth is a special design so that sound can easily resonate through while keeping the speaker hidden), they have their rubber feet mounted and they both look great. The speaker cabinet also has its removable castors installed so that it can be rolled from location to location. The Celestron speaker is mounted inside and wired to the input jack in the top center of the rear panel. I used the completed speaker cabinet during yesterday's guitar lesson. My teacher liked the look and sound so much he has asked me to build him one. Quite the compliment. Maybe I can trade lessons for it?

Three more pictures of the finished cabinets. Left there is a closer view of the guitar (for scale, and because it's cool) next to the amplifier and speaker cabinets (top and bottom). Center you see the cabinets from behind. I used traditional looking screws with fancy washers to attach the rear panels to give it that nice standard decorative look. The third picture on the right above is a closer view into the back of the speaker cabinet with the mounted Celestron. If you look you can see the red and black wires from it to the speaker jack in the center of the top panel (there is a dust particle on the camera lens that created a halo next to the jack, ignore that).

Above, to the left, is another view of the rear of the amplifier cabinet. You can see the hole cut at the top to allow the electronics, which get very hot, to exhaust and stay semi-cool for extended life. In the middle is another front view. To the right is a top down view to show how the amplifier is smaller than the speaker so as to fit the chassis. The speaker cabinet needs the extra room for the speaker to resonate. Besides, it would make no sense for the amp to be bigger than the speaker, the same size maybe, but not bigger. It's a personal choice.

These next two pictures show off the underside (bottoms) of the two cabinets. To the left is the amplifier with rubber feet. To the right is the speaker cabinet with both rubber feet and removable castors. Next time I'll position the castors closer to the front and back (as close as possible without being visible). As it is there is a slight chance of tipping over if pushed hard enough. Its a minimal risk, just a small thing to improve next time around.
My recent push to get things going all started a week ago when I was at True Value Hardware on Charles street. I was ordering a step bit to cut holes in the chassis and picking up odds and ends. I needed a stapler to attach the grill cloth to the two boards. I was eyeing a nice stapler when the owner of the place came by and we started chatting. "What are you building this time?" and before I knew it he was impressed with my ambitious goals and offered that I borrow the electric stapler. "Sure, use it then put it back in the box like you found it. Heck, I did that the other day. Its a great stapler." So I left with some random stuff I needed and a borrowed stapler. I don't like keeping borrowed things around, so I felt the need to get going. And so I have.

Just to give you an idea of the process take a close look at the two pictures above. I don't know if I've mentioned before that I don't have a garage, a work shop, or any other normal place to do this kind of work. I have a living room, where I live and work. Every time I wanted to do some work I would haul out all the equipment, set things up, do some work, clean up, put things away, and clean up with my vacuum and sometimes more.The thing you see under the amp sitting on the floor is a piece of plywood, or as I like to call it, my work bench. I'd put that up on a piano stand about a foot off the floor (here it is on the floor as I put on the tolex, wheels, etc) and do my work sitting down. The dust from drilling and sanding had to be managed somehow so I developed techniques to vacuum while I drilled or sanded or anything else so that I always had a nearly perfectly clean working area. This kept the dust to a minimum. If I hadn't done that I would have tracked it all over the place. As it is, my place is perfectly clean each time I stop working, well as clean as it was before I started working.

Once I got the cloth on the speaker front I mounted up the speaker, then I put in the speaker jack and wired things up. I wanted to a) test the connections and b) hear what it was going to sound like so I hooked that up to my existing Bedrock amplifier and turned it up. It sounded great. It was ready to be mounted into the cabinet.
I put the speaker cabinet together after measuring, drilling, counter sinking, and gluing the internal supports in. That took a bit of time. Then I put the pieces of the speaker cabinet together with screws and wood glue. I filled in the counter sunk holes, let it dry, then sanded down the excess putty. The next step was to round the edges with a 1/2" round router bit. That was a pain due to the MDF dust. Then I spray painted all the parts with a flat black paint.
I don't have pictures here, but it was a fun and complex process to cut a properly sized hole in the board for the speaker. It had to be perfect and sized so that there was room to screw things together. I built a jig that attached to my router and the center of the circle out of a piece of scrap wood. Then I used a straight bit, measured one more time, and went for it. Perfect, first try.

I used Dap Weld non-toxic glue to attach the tolex covering. Its important to cut the tolex just right, then carefully position it, check the positioning (twice), practice applying it before applying the glue, then glue it in stages. I used the disposable foam brushes for the glue, get six. Use one, toss it out after you finish up a stage, it will be full of a rubbery cement and its not worth saving. Apply the glue to both the tolex and the wood to be covered at the same time, let it dry a bit (10 min is enough, 5 is okay), then slowly press it into place being sure to check positioning as you go. Press hard enough to remove bubbles and excess glue. Go slow. It pays to be patient at this stage. Don't glue the edges until the glue sets up a bit, use the time to visualize how the tolex will wrap the corner, then wrap on around into the interior of the cabinets. Make sure you think it through, then cut. Remember you only have one shot at this, mess up and you'll be left pealing off the tolex and dealing with a sticky mess and a lot of cleanup. I avoided that, I made one small tolex cutting mistake, but I can live with it. I made another tolex related mistake later because I forced something rather than revising it, again I'll live with it. Its not so visible unless you look for it.

Something I forgot to mention. Before applying the tolex, use a large drill bit to create holes to counter sink the corner pieces. They are formed to sit just below the surface, I didn't do this for the speaker cabinet and I paid the price. I had to use a hammer to flatten them, the screws don't really fit properly, again a minor defect I can deal with. Also make sure you get corner pieces that wrap around at 1 1/2" not 1" (as I did). I had to use a hammer to flatten the wrap, then snips to remove the excess and a file to clean the edges. One more minor mistake that I'll notice, but no one else will. While I'm on the subject, drill the holes for the castors before putting on the tolex too. Again, I didn't and I paid for it later.
The grill cloth went on relatively easily, make sure to double up the edges on the back side when stapling them down. Be careful at the corners, you'll have to cut more than you want to, but don't take too much off. One more lesson I learned at this point is that grill cloth is thick. It'll add at least 1/8 if not 1/4 inch to the edges of the wood making fit hard if your tolerances are too close. This is where I made my second tolex mistake, I forced a piece in and it ripped the tolex. If you look closely on the left of this picture you can find it. Go ahead, try.

Here are a few more shots, by now you know that I'm proud of this work and I'm just showing off. I hope you don't mind.

In other news, I now have the right transformer and guess what, it fits properly. I ordered a step bit (1/8" - 1") to cut the larger holes in the chassis. I've started putting the holes into the turret board using a Dremel mounted on its drill press-like device. I tried installing a turret, but quickly discovered that I was missing something. Turns out that something was the second half to the turret installation tool. I'll try it again soon enough, this time with both pieces of the tool, I bet it'll work this time. My plan is to get things ready to wire up by the end of today, then do the rest this weekend and test it next week. That may be rushing things a bit, but I have momentum now so I might as well keep going.

Technorati Tags: audiophile, diy, guitar, hobbies, music

Ossus Amplifiers - Step 4, cabinet assemble part 2

2006-05-27T08:58:00.000-04:00

I've been busy the past three weeks. Work's been a bit hectic and time consuming, but despite that distraction (get it?) I've made some good progress. Better yet, I have pictures. Let's get to it.
All of this happened about two weeks ago. Before that I had taken the PDF files with the designs for the chassis, turret board, and electronics schematic to a Kinkos and paid (way too much) to have them printed at scale in color. Now is where that money starts to pay off. The following picture shows the component layout (the big sheet of paper), the garolite board with the turret drilling layout, and the chassis with its drilling layout as well. The layouts were rubber cemented to the pieces. Just secure enough to allow for easy drilling. I thought it was a better idea than masking tape, your call.

Next is a picture of the garolite board placed inside the chassis where it will ultimately live.

I thought I'd put the parts onto the chassis just to get a feel for things. I forgot to mention, my etched face and rear plates arrived mid-last week. I went to look at them, but they had a protective covering. I almost peeled it off when it dawned on me, keeping that on would protect the plates when I drill them later. I left them in thier bubble wrapped and placed them at the front of the chassis. I put down the three tubes where they will live, and the two transformers.

Notice that the transformers are aligned at a right angle to each other, this cancels their noise out of the circuit. Here is a front view to get an idea of how the parts will sit on top of the chassis.

Here is a top view where I've placed the garolite on top to see how it will ultimately align with the parts on top. The garolite will end up inside the chassis, but I was curious to see how things would be wired. So there you have it.

Here I've removed the tube boxes and put down the tube mount rings just because they are cool and I wanted to ensure that the drill holes lined up.

Then I noticed something odd. The two transformers were about the same size. I remembered from other pictures that one should be larger than the other. Hmmmm... Then I looked at the mounting holes for the Hammond 125ES, they didn't line up with the transformer. Something was amiss. I went back to the pictures of finished amps to see if the drawing was off, or if the part was wrong. The pictures showed that I had a Hammond 125ES and everyone else had a Hammond 125ESE. Turns out I bought the wrong transformer. I called Angela's and ordered the proper one, look for the other one on eBay soon. It pays to double and triple check things. You can see in this photo how the transformer does not line up properly with the holes.

On to the cabinet, I put together the amp cabinet. Before I did that I painted the pieces with a flat black spray paint. Then I glued and screwed (1 1/2" wood screws) each of the 2"x1"x1" support pieces. I glued each edge using more of your basic wood glue, then put five 2" wood screws along each edge. I filled in the screw countersunk holes with a bit of DAP plastic wood filler. I used a router to put a 1/2" round edge on all exterior sides. I had to do some adjustments on two of the support pieces, they prevented the chassis from sliding in by a very slight margin. A little sanding and that was fixed, I'll touch up the black paint and paint the exterior at the same time. This picture shows the amp cabinet assembled with the chassis in viewed from the front.

The wood working continues next with the speaker cabinet. It's laid up in this photo with angle brackets. I've pre-drilled and counter sunk five screw points at each edge. With those in place I'll take the pieces out of the clamps and place the supports for the front speaker panel and the rear baffles. I need to cut the hole for the speaker out too. The speaker will mount to the board using t-nuts. I'll use the same to mount the speaker board to the braces. Once everything is measured, drilled, glued, screwed, holes filled with putty, and painted I'll screw the sides together and route the edges to match the amp. You can see the amp cabinet sitting on top of the speaker cabinet, then off to the left is the Celestron speaker.

That speaker is huge. I have a big hand, I don't think you can appreciate its size until you see one in person. It should sound terrific.

So, good progress on a few fronts. I need to push ahead on drilling out the chassis top, face plate and chassis front, back plate and chassis rear, the turret. I'll also move some of the speaker cabinet things along to get it to the same point as the amp cabinet.
Lots of work left, nothing too tough yet. Wiring will be a challenge. One mistake there and the consequences range from a poor sounding amp to a good high voltage shock. But I have a solution for testing the amp for ground faults that I'll detail in a future post. That should give me a way to avoid shocking myself, which is a good thing.

Technorati Tags: audiophile, diy, guitar, hobbies, music

Ossus Amplifiers - Step 5, ordering the electronics and other parts

2006-05-07T12:21:00.000-04:00

This must be what women feel like when they go out for shoes. I'm almost giddy with excitement. Resisters, capacitors, transformers and vacuum tubes. What could be better? It's time to get the parts ordered and on their way. WhileI'm waiting for them to arrive I'll continue to work on the cabinets, but my guess it that could take a few weeks and I don't want to get stalled later in the process. Projects that start gathering dust generally never get finished, it's just the way I am. Before I jump into the list I'll say that I started with the parts list at the Silvatone Hi-Octane project. I found that a few parts have new part numbers, some parts are not listed, and one or two are in error. In the following list I try to correct those errors and add other parts that I think were over looked. So, with that, here is the list of parts I've ordered.

Type	Qty	Reference	Part	Supplier	Part #
Capacitors	4	C1,C2,C13,C14	47uF/450V	Mouser	140-XAL450V47-RC
	2	C7,C3	470pF	Mouser	5982-15-500V470
	4	C4,C5,C6,C8	0.022uF	Mouser	75-715P600V0.022
	2	C9,C10	1uF/25V	Mouser	140-XAL50V1.0
	1	C11	0.68uF	Mouser	23ME468
	1	C12	100uF/25V	Mouser	140-XAL25V100-RC

Resistors	1	R1	10K/1W	Mouser	281-10k
	2	R2,R4	1K/1W	Mouser	281-1.0k-RC
	5	R3,R5,R6,R7	100K	Mouser	273-100k-RC
	1	R8	33K	Mouser	273-33k-RC
	1	R9	5.6K	Mouser	273-5.6k
	1	R10	68K	Mouser	273-68k-RC
	4	R11,R12,R15,R17	470K	Mouser	273-470k
	1	R13	1 Meg	Mouser	273-1.0M-RC
	1	R14	2.7K	Mouser	273-2.7k
	1	R16	1.2K	Mouser	273-1.2k-RC
	1	R18	820	Mouser	273-820
	1	R19	130/1W	Mouser	281-130
	1	R20	100/2W	Mouser	282-100-RC
	1	R21	100K/1W	Mouser	281-100k-RC
	2	R22,R23	100	Mouser	273-100

Potentiometers	2	VR4,VR6	1 Meg Log	Mouser	31VJ601-F
	1	VR1,VR2	Dual - Ganged 1 Meg Log	Mouser	313-2420-1m
	1	VR3	250K Lin	Mouser	31VA503-F
	1	VR5	25K Lin	Mouser	31VA403-F



Switches	1	S1	SW 3POS (Impedence)	Mouser	633-M202402
	1	S2	SW SPST (Standby)	Mouser	633-S1A-RO
	1	S3	SW DPDT (Power)	Mouser	633-S6A-RO



Transformers	1	T1	5W OT (Hammond 125ESE)	Angela	125ESE
	1	T2	Hammond 269EX	Angela	269EX



Tubes	2	V1,V2	12AX7A	Triode	12ax7tesla JJ
	1	V3	EL 84	Triode	EL84JJ



Turret Board	50		Turrets 1/8" Board	Hoffman	Turrets
	1		Garolite 3" x 11" x 1/8"	McMaster-Carr	9322K43



Wire	2	D2,D1	1N4007	Mouser	583-1N4007-B



Misc	2	D2,D1	1N4007	Mouser	583-1N4007-B
	1	J2	Input Jack (shorting)	Mouser	502-L-12A
	1	J1	Speaker Jack (nonshorting)	Mouser	502-L-11
	1		16 AWG Belden 3 wire grounded cord	Angela	AC Power Cord
	1	J3	AC Inlet Port	Angela	AC Inlet Port
	1	F1	Fuse Holder	Mouser	576-03453RF1H
	1		Fuse 1A Slo Blo	Mouser	576-0215001.HXP
	1		Phone Plug	Mouser	502-227
	2	Inside Chassis	Shoulder Washer, .385	Mouser	534-3069
	2	Outside Chassis	Flat Washer	Mouser	534-3222
	3 packs of 2 each		Metal Dome Knob Chrome, push on style	Guitar Nucleus	MK3300-010
	1		16x8x2 Chassis	Mouser	546-1444-26
	5		3/8" Grommets	Mouser	534-745
	3		9 Pin Ceramic Socket	Triode	9pingoldchassis
	1		Lamp Holder	Hoffman	Pilot Lamp Assembly
	1		Lens	Hoffman	Green Jewel
	1		6.3V Lamp	Hoffman	6.3v Lamp
	10		#4-40 Machine Screw	Hoffman	4-40 x 3/8"
	10		#6-32 Machine Screw	Hoffman	6-32 x 3/8"
	10		#4 Keps Nut	Hoffman	#4 Lock Nut
	10		#6 Keps Nut	Hoffman	#6 Lock Nut
	10		#4 Flat Washer	Hoffman	#4 Flat Washer
	10		#6 Flat Washer	Hoffman	#6 Flat Washer
	10' each		20 amp solid core hookup wire	McMaster-Carr	KC51 (black), K654 (white), K664 (green), K667 (blue),K661 (yellow), K657 (red)
	10' each	Heater Wire	Kimber TCSS Varistrand Internal Hookup Wire, #19AWG, / black, green	Angela	Item #4 on page

Every time I look at this list it is clear that I have my work cut out for me. There is a lot to wire up. I found that some of the parts specified, mostly from Mouser, have to be ordered in lots larger than what you require. Most ofthe time it is lots of 10 resistors rather than 1 or 2. This isn't a big deal, resistors are cheap and now I have a few with which to practice soldering. There were also a few tools that I purchased along with the parts. A tool to bend resistors properly, a new sharp drill bit to cut the aluminum cleanly, and some other basic stuff. I already own a really nice voltmeter, which is essential for this type of project. I went to Home Depot to pick up some odds and ends and a few tools that I think I'll need. I'm not going tocount those in the running cost. My rational is that they are useful for other projects and so not really part of the amplifier's build cost.

Speaking of costs things are starting to really add up. The parts listed above, a few extra tools, and a few random other parts I will need along the way have cost me roughly $500. That includes two full sets of color reproductions of the PDF plans from the Silvatone Hi-Octane site tobe used for part layout and wiring for $40 at the local Kinkos (crooks). If you owned all the tools, printed things yourself, and were a bit more frugal than I am you could easily knock off $200 of that.

Soon I'll be adding the final set ofparts purchases in another post. The finishing items like tolex, wicker, rubber feet, handles, and even the Celstron 12" speaker I'll need for the speaker cabinet have not yet been ordered. So, I've got one more set of purchases and then I should be done spending significant amounts of money unless Ifry/twist/mangle/smash or otherwise destroy something later on.

Cost for parts,etc: ~$500.00
Running total: ~$660.00

I've found a few good resource for amp builders out there. Here they are in no particular order.

18watt - a members onlyplace for amp builders.
Tubebias tables - the what and how of tube biasing, which turns out to be a critical success factor.
DIY GuitarAmplifiers - parts, information, etc.
The Tube Store -guess what they sell.
DIY HiFi Supply -another easy one to guess.
Tolex application tutorial/pictorial - Casy4's ever elusive pictures of proper tolex application.
Mick's Hi-Octane build - Looks like someone else started with Ramio'sdesign and was able to build a functional amp. Sure, he's an electrical engineer, I can do that.
TrainWreck Amplifiers- Turns out that if you know what you're doing you can charge $30,000 or more for a guitar amplifier. My friend tells me these guys are the cream of the crop in hand built amps.
Ken Fischer's Column - Ken is the smart guy from TrainWreck who does all that deep thinking about signal paths and sound quality differences in each and every part of his amplifiers. He writes a column for Ultimate Guitar Gear.

I'll wrap up with some sage advice from Hoffman Amps, advice for those starting this type of project, in summary "go buy a nice amp at your local store." My running total proves this point, but its not about cost for me, its about building it myself. God I hope it works.

Technorati Tags:audiophile, design,diy,guitar, hobbies, music

Ossus Amplifiers - Step 4, cabinet assembly, part 1

2006-05-07T10:23:00.000-04:00

Okay, I get it, I'm not an expert when it comes to building things out of wood from scratch. There are a lot of variables to keep track of, a lot of double checking measurements, a lot of "Ah ha!" moments and even a few "Oh crap" moments to keep things interesting.
My grandfather and my father were both excellent carpenters. I've remember watching in awe as they built various pieces of furniture. At one point they took a wood working course together and soon a nice new coffee table arrived. Some, but certainly not all of that ability was passed on genetically and via osmosis to me. I wish I had either had them around now to help, or that I'd appreciated their skills more and paid closer attention to them when they were around. But here I am, and every mistake I make builds a) character and b) skills. So I'm one hell of a skilled character these days.
I have developed a love/hate relationship with MDF. That's the type of material specified for 98% of the cabinets. Cheap, flat, smooth, dense, and not too hard too work with are all good qualities of this material. But, if you work with small pieces, or forget to drill pilot holes, you're going to have issues.
The plans call for a lot of 1" x 1" pieces of various lengths to use as braces. They will form the braces that hold up the front and back panels on both cabinets. This seemed reasonable to me in theory.
Today I started out early with a goal of drilling all the holes for the amp cabinet and putting together a few of the pieces in preparation for painting. Things started off well enough, but eventually I ran into a few problems.
Two things were against me at this point, I was getting tired, but I wanted to make progress so kept pushing myself. But the larger problem was the MDF, it was just not going to hold up. With all pieces measured, cut, holes laid out, and drilled for assembly I took a deep breath and started putting pieces together gluing, bolting and screwing things together. At first things were proceeding as anticipated then it happened. As I tightened a screw to mount one of the 1" x 1" braces to a side piece crack! It split.

Turns out that MDF is really like a bunch of layers of cardboard glued together. That's nifty, until you apply pressure between layers. This causes them to split quite easily. I cursed a few choice words, then some quick thinking and wood glue led to a reasonable solution. This same scenario played out two more times with two other pieces of 1" x 1" MDF. This was getting out of control quickly. Clamps were everywhere holding together the split pieces with copious amounts of wood glue trying to keep the MDF together. Not good, especially for what were supposed to be structural supports, but I decided to press on. This was where the fatigue set in and bad decision making resulted. After getting things to a point where I thought it just might be okay and not result in a crappy, unsound, cabinet I went to put part A into slot B (it doesn't really matter what part I'm talking about, just that they were things I'd carefully assembled to fit nicely together). The two pieces didn't fit, they weren't even close. I was off by at least a 1/4". Crap. What the hell had I done wrong? Well, in my haste and thanks to fatigue I had not taken into account an offset of 1/8" per side on a particular board and now I was really screwed, there was no fixing this. More choice words, then a quick disassembly and I was left with some broken scrap 1" x 1" MDF supports.

Two things, first measure, think it through, visualize, review the plan, measure again, measure a third time, then cut or drill something. Second, if you're tired, put the project aside for another time.
My next step is to cut new 1" x 1" blocks to replace the crappy MDF ones. Some real wood, pine, ash, or even some scrap teak I have lying around is going to do the trick. Something that won't split with minimal pressure (like MDF, particle board, and plywood - basically anything consisting of glued layers). That's what I need to make this thing work. That and a good night's sleep.

Technorati Tags: design, diy, hobbies, music

Ossus Amplifiers - Step 3, preparing the cabinet for assembly

2006-05-07T09:57:00.000-04:00

MDF appears to be highly compressed cardboard. Its like particle board but the particles are "micro-sized", hence Micro-Dense Fiber (MDF). This makes for heavy, solid, and very straight boards. On the downside the dust from cutting them to size is also micro-fine and was really getting to me. The smell and the dust are a drag too. I decided to coat the MDF for strength and to seal up the dust and smell. Conveniently I had some appropriate coatings on hand. Recently I had recoated my hardwood floors under my desk, where there is maximum wear and tear, with a nice Minwax poly urethane. About two weeks ago I was doing a different project involving flat black spray paint. I decided to test both, layering each on the other in the four possible combinations to see which I liked the best. I knew that eventually the cabinet needed to be black, but the question was, glossy or flat? An aesthetic choice, but worth a quick test.

It only took a few minutes to put down a few coats of each (MDF on the left, poplar on the right in the picture). Coating the pieces has sealed them up nicely. The MDF sucked up both the black spray paint and the poly urethane like a new dry sponge. I chose to put one coat of poly urethane on, then assemble the pieces, and after that to paint over with flat black. The interior paint will be exposed, but eventually the exterior of the cabinets will be covered with black tolex, and if that rips I don't want to expose a brown wood color. Another benefit to coating the boards is an increased water integrity and overall stability. It was a bit disconcerting to see how aggressively the poly urethane was drawn down into the fiber. In my head I could see water just destroying an uncoated board. The wood will either be finished with a flat black spray paint or covered with tolex so the urethane will be totally invisible when I'm done, but I'll know it's there just in case.
It only took about an hour to finish the job and put the pieces aside to dry. The dust and smell are gone, and I feel better about the wood. MDF is an odd material. Next up, start assembly of the cabinets.

Technorati Tags: audiophile, design, diy, guitar, hobbies, music