The Ron Apple Memorial Bass Cabinet

This is a bass cabinet I customized for a friend. I didn’t do the paint job—it was already painted when I got my mitts on it.

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This cab started life in the 1980’s as a Peavey 115.

peavey_frontpeavey_rear

Typical Peavey gear, nothing fancy but it got the job done.  One 15″ driver in a vented cab.  The cab was a mix of plywood and particle board, tolexed, with one 1/4″ jack and one strap handle on top.

I don’t know how many times this cab changed hands, but I do know that in the ’80’s it belonged to Ron Apple, who played bass in the Bohemians.  The Bohemians nearly comprised the entire music scene in Novato at that time (approx ’83-’84) and they were a great inspiration to a lot of us who had dreams of making music.  They played lots of local venues–San Marin High School, the Novato theater, various rec. centers.  They had a great jangly melodic sound that with sixties pop and psychedelic influences.  They had a dedicated tambourine player, Joey Kosdrosky.  Imagine having the balls to get up there and play tambourine and do your own weird style of dance.  They did their own thing their own way, that’s what inspired me.

Anyway, the current owner of this cab is Pat “the Rat” Powers, AKA Pat Riot, AKA Ned Zapariah.  The cab had seen many years of use and abuse in his previous bands, most notably RETOX, whose name is still painted on the cab.  When he brought it to me the speaker was shredded and the grille was long gone.

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Before

 

Modeling the Kappa 15LFA in WinISD
Modeling the Kappa 15LFA in WinISD

The original plan was to just slap a new 15″ driver in there, maybe tune the box a bit, and hand it back to Pat.  Thing is, the only 15 I had on hand was a Kappa 15LFA, which wouldn’t be well suited to Pat’s playing style, which is definitely “lead bass” in the mode of Flea or Adam Clayton.  He’s not content to hold down the root and fill out the low end.  He needs to cut through the mix.

As it happened, I’d already been noodling the idea of a 15/6 cab with the Kappa as the low and an Alphalite 6A CBMR for the mid.  I’d arrived at that idea simply because the Alphalite was relatively affordable (compared to, say, an 18Sound mid) and its sensitivity matched that of the Kappa, at about 99 dB 1w/1m.  The cab I’d been modelling in WinISD was about 2.8 cubic feet.

When I measured the volume of the old Peavey it was right at 3 cubic feet before subtracting for the driver, port, etc.  So basically I’d just been handed the right size cab for the project I’d been envisioning.

Modeling a crossover in LTSpice

So I had a box, it already had a hole for the 15 and a 6″ port about 7″ deep, which WinISD told me was pretty close to what I’d want.  But I needed to design a crossover, which I’d never done before.  So I got on TalkBass and started a thread, which wound up being crucial.  I got tons of good info, got PMs from experienced guys offering advice, and got turned on to BoxSim, which I wound up using to simulate the box & crossover.  I also learned how to simulate a crossover in LTSpice.  The trick was to model the speaker as an inductor, assigning it a series resistance of approximately what you’d expect at the crossover frequency and an inductance straight off the Thiele-Small parameters for the driver.

BoxSim turned out to be the most helpful for getting ballpark values for the crossover.  It lets you input all of your box and driver parameters, then simulated the crossover taking into account the effects of the box tuning, baffle step, etc.  It will even optimize the crossover for you, adjusting whichever component values you allow it to adjust.  I based my initial crossover design partly on BoxSim’s optimization, partly on advice from an experienced builder on TalkBass.

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some bracing
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Oops, cut the wrong hole and had to glue the cutout back in. Guess that’s where I’ll mount the memorial plaque.
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Once I’d ordered the crossover parts and 6″ driver, I set to work on the cabinet.  There was very little bracing, so I added some—spine and girdle bracing, as well as a couple of runners from the bottom of the baffle up to the girdle brace, on either side of the 15″ hole.  All the bracing I added was 3/4″ poplar stock from Home Depot, glued in with PL Premium construction adhesive and tacked into place with a brad nailer.  I also cut holes for some inset handles I had lying around from a previous project.  The stock single top strap was definitely inadequate.

RAMC_crossover
Final crossover

Once I got my parts I built the crossover on a scrap of 1/4″ ply, installed that and the 6″ driver and put the whole thing together to try it out.  I’d been warned about the Alphalite’s impedance spike around 500hz, and I’d thought I had crossed over high enough to avoid it, but no dice.  Farty noises from the 6 with any loud midrange-y notes.  Back to the drawing board.  BoxSim told me that I needed a bigger cap and smaller inductor on the HF driver.  I dug out an crossover from an old, failed project and found to my surprise that the parts I had on hand looked like they world work pretty well.  In fact, I couldn’t sim anything much better.  So I rebuilt with the new (old) parts and blammo!  Good sound!

BoxSim_RAMC_Freq_Response
BoxSim frequency plot

I finished up by shortening the port a bit, which brought the box tuning up to about 48hz.  I also added some fiberglass batting (the cab as it came to me had no stuffing, unless you count the random garbage floating around inside [punk rock!]).  I tacked on some grille supports (hardware store moulding and weatherstripping), cut the grille material (screen door kick guard, OSH, $10) to size and screwed it on.  The memorial plaque I made from some leftover mild steel sheet using a cheap set of alphanumeric punches.

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Back to work on the Pelvis Amp

After months of inaction due to creative and logistical roadblocks, I’m finally back to work on the Pelvis hi-fi amp. Which is not to say that it will be done next week or anything–it’s still fighting for time with the bathroom remodel, and Karin’s been cracking the whip there.  No rest for me until I’m done with:

  • floor
  • drywall
  • tubular skylight
  • medicine cabinet
  • vanity/sink
  • paint
  • baseboards
Workbench!!
Workbench!!

But meanwhile, I am able to embezzle a few minutes here and there, and I’ve just overcome one of the major obstacles in the way of keeping a side project going;  I’ve built a workbench!  No more soldering and computing at the same tiny desk, components and chassis fighting for space with keyboard and mouse.  Now I’ll be able to leave the project in whatever state it’s in, no worries about having to clear it away to get to the computer.  Ahhh.

 

danger: no user serviceable parts on this workbench
danger: no user serviceable parts on this workbench
So here’s the workbench as I prepare to test the tubelab Simple SE power amp that will be the heart of the Pelvis amp with its transformers.  The little screw connectors make it super easy to wire up.  Note the highly custom handcrafted douglas fir workstands.  The transformers are HUGE.  This amp will not be light, especially when its in a hardwood case with a thick steel top plate.  I may actually have to deliver the thing personally–it might actually be cheaper do drive down to SoCal than to pay to ship this thing.
black steel in the hour of chaos
black steel in the hour of chaos

Speaking of the top plate, I’ve finally got the steel cut to size.  A local metal fabricator did that for me.  Then I realized that one side was not quite square.  I filed away at it for a bit with various hand tools, but it quickly became obvious I could spend months just getting the plate square doing it by hand.  Clearly I needed to invest in an angle grinder.  I haven’t deployed it yet, but I expect it to make quick work of the errant edge.  Then a little cleanup with the hand tools and it’ll be square as Ward Cleaver and I’ll be ready to drill.

The trick will be figuring out how to grind without setting the lab on fire.  Probably have to roll up the carpet at least.

 

Terminal Port Experiments on a 2 cu ft cab

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Here’s an example of me getting too excited about a project or experiment to document the process along the way. So here are a couple’after’ photos of a recent experiment adding vents to my used-to-be-a-combo closed cab. I modeled the frequency response along the way with WinISD, working backward: tweaking the tuning frequency until the length of vents matched the thickness of the baffle for a given number & diameter of ports. The results were not good. As soon as I started making ports, the cab got louder, but the treble became obnoxious. Adding more ports increased bass response, but did nothing about the harsh treble. By the time I had six ports I had stopped modeling, figuring I was pretty close to an open cab at that point. It definitely sounded better the more ports I put in it, but nowhere near as good as it sounded sealed. So I got out the PL Premium and glued the plugs back in, and now the cab is extra crazy looking. Sounds great though.

Speaker is an Eminence Private Jack. Amp used was an AX84 SEL, more or less. Cab was once a Fender London Reverb combo, and is about 2 cubic feet. It’s lined, back and sides, with 1.5″ polyester batting.

Sound clips would have been a good idea, huh? As I said, I tend not to think of documenting until it’s too late.

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4_vents

2_vents

Masco CM20

So I go to the lumber yard today to pick up a used 2×6 from the Away Station.  Carrie, who runs the place, is writing up my tag for the wood and asks if there’s anything else I’m looking for.  I tell her I’m always looking for old tube gear and she has me write down my number, says she’ll put me on the “want” list.  I walk away assuming nothing will come of it–most likely the scrap of paper with my number on it will wind up blown into a corner of the shed.

Half an hour later Carrie’s on my answering machine.  Some dude on his way to the dump.  Tube thingy.  I ran right down there.

So here’s the latest in my growing hoard of future projects.  It’s a Masco monoblock amplifier, model CM20. Push pull 6L6G output section, couple of 6SJ7 driver tubes, MASSIVE power transformer, choke and output transformer.  2 5U4GB rectifiers.  Came with all but one tube and a lot of dust, which I take as a good sign.  It’s likely this thing spent the last 30 years in someone’s garage/basement, and with a tube missing it seems unlikely anyone would have tried to power it up recently.

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Unrecognizable Whitey

Or, how to ensure that you are thoroughly searched by the TSA.

unrecognizable whitey: a guitar amp project waiting to happen
Cab and speakers

I recently traveled to Boston for an outrageously large shindig celebrating my mom’s 80th.  We have a huge extended family there, mostly around Malden and Everett.  I stayed with my cousin Allison and her husband Gary.  I got to blathering to Gary about my amp hobby, and offered me Gary Jr’s old amp since no one was using it and it was just sitting out on the porch.   I was intrigued and immediately wanted it, though I had my doubts about getting it home on the plane.

The amp comes by its nickname honestly.  The faceplate has been painted white, and a cheap aluminum grille added, also painted white.  From the front you can’t tell what it is.  The back was not sprayed white however, so you can tell it’s a Lab Series L5 amp, 100 watts, supposedly one of the best sounding solid state amps ever made.  Apparently Clapton had one, as did B.B. King.  The L5 was a clean amp, preferred by blues and jazz players.  I wasn’t interested in restoring it (it was pretty far gone anyway) but the chassis and cabinet looked in decent shape, and it came with two JBL K120 speakers, probably still in working condition.

power transformer from Lab Series L5
TSA bait

But again, how to get it home?  It weighed at least 80 lbs. and was way too big to even think about carrying on the plane.  I consulted the United website.  As a Frequent Rewards program flier, I was entitled to check one piece of luggage, up to 50 lbs.  Any heavier and it would cost $100 to check it.  I decided the thing to do was remove some of the heavy bits and ship them.  Gary offered to take care of shipping the speakers; he has the advantage of working for a major shipping company.  We didn’t have a scale, and the thing still seemed fairly heavy after removing the speakers, so I removed the power transformer and put it in my backpack.

Off to Logan the next day.  The skycap didn’t look twice at the derelict amp carcass I was checking through to San Francisco.  I tipped him $3.  The TSA screening was a different story.  They spied the suspicious device on their monitor and took me right over to an inspection station.  The TSA officer asked if there was anything sharp in my backpack.

I said, “well, the transformer you’re looking for has some rusty sheet metal bits, but it’s not particularly sharp.”

She found the tranny and pulled it out, gave a cursory look through the rest of my bag.  Then I got to watch her use what I assume was an electronic nose—a small wand with a disc on the end, which she rubbed all over my suspicious item.   Probably it would have squealed if it smelled any ammonium nitrate or saltpeter.  It kept quiet, so she took my bag and transformer for a second ride through the x-ray machine.  As she did I saw her point at the transformer and ask her supervisor something, probably “is this a transformer?”  He nodded.  I was soon on my way.

And here the speakers are, a couple weeks later, reunited with their cab.  Gary did an amazing packing job, I wish I’d taken a picture before unboxing.  The baggage handlers probably could have dropped the box from the cargo hold to the tarmac and the speakers would have been fine.

I have big plans for this one.  Mum’s the word for now as ideas continue to congeal in my brain, but it’s gonna be cool, and it’ll look nothing like it does now when I’m done.

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Chocolate Bourbon Pecan Pie

FILLING
3/4 cup sugar
1/2 cup maple syrup
2 1/2 tbsp bourbon
2 tbsp butter
2 tbsp flour
1/2 cup semi-sweet chocolate chips
3 large eggs
1 cup toasted pecans

Toast the pecans in a skillet over medium-high heat. Be careful, keep ’em moving. Once they reach a certain temperature they go from toasted to burnt right quick.
Everything else, throw in a blender and blend. Toss the pecans and blended mixture in a bowl and mix, then pour into prepared crust. Bake at 400 for 5 minutes, then 350 for about 30 minutes.

The Green Manalishi nears completion

Eye of the Manalishi

New photos of the Green Manalishi showing the faceplate, etc. Still need to take some video to show the magic eye and tremolo in action.

Here are some photos of the process of creating the patina for the faceplate. I basically started with a sheet of weldable steel, rusted the hell out of it with salt water, rubbed of most of the orange oxide, rubbed on some instant gun blue…allowing for drying in between stages. Then a final coat of penetrating oil with teflon.

Farnsworth!

1948 Farnsworth radio phonograph

1948 Farnsworth radio phonographThis is a recent acquisition from the Away Station. I like it so much I’m considering keeping it a radio. It was built in 1948, and I bet if I just replace 1 tube and the electrolytic capacitors, it’ll work just fine.

Philo Farnsworth was famous for inventing television, but his company made radios and such as well. There’s a statue of him outside the building where I work. George is a fan of technical innovators.