Cornford Hurricane Build: 10lbs of crap in a 5lb Chassis

[dorrisant]

Boards = brilliant. Looks like some '50s milspec or valve computer miniaturization attempt. TAG employee of the month nomination.

So did you cut the stand-off in half at a bevel, then sandwich the board btwn the two pieces?

Thanks again to all for the kind words.

Yes rp, that is exactly how i did it... I looked areound the shop for something like a metal tube of the appropriate size to cut at the angle. Couldn't find the tubing I was looking for. The standoffs were just right.

... and as far as strength goes, these mounts are very strong. These are 2mm thick boards (cut in half from a single piece) and I could pick the bare chassis (no TXs) up and swing it around without any flex or worry. The contact surface area of the standoff cut at an angle actually increases with the angle cut. More contact surface area equates to a much stronger mount. I am very happy with the way that part turned out!

A local luthier friend of mine brought a bookmatched piece of Cocobolo that I will use for a new facia... More sanding to do.

[dorrisant]

Hey Leo... How about a "Cornfield Hurry-Cane"?

I could etch this into the faceplate... Too much?

[martin manning]

Just replacing Cornford with Cornfield works for me.

[rp]

and let's not forget...

[Tone Lover]

How about a pic of a half-open can of biscuits... You know, when you pull the little tab and the cardboard pops..

Maybe the image below... The one on the left of course!

Man the cardboard popped on that one .LOL best laugh ive had in a while.

[Leo_Gnardo]

Hey Leo... How about a "Cornfield Hurry-Cane"?

I could etch this into the faceplate... Too much?

Never underestimate the power of alliteration: how's 'Cornfield Cyclone' hit ya? We're not in Kansas anymore Toto... This is cool, I feel like we're in a Mad Men episode. I should light up a Pall Mall, straighten my tie & take a sip of a martini.

[Structo]

That was very creative thinking to angle the boards like that.

Kudos for using a old chassis instead of just buying a new one.

[dorrisant]

Leo... I thought about it like a pitch-man too. How about CornFed Hurricane, Tornado, Cyclone, etc.. Seems appropriate for tornado alley here where I live.

Thanks Tom, I actually have been finding quite a few projects like this. I think I bought this amp with a bad PT for like $40. Sometimes I buy them from customers when they don't feel like investing any more money in them.

I recently bought a Marshall Haze 40 from another customer. Had a dying PT... The cost of any type of replacement was too high for him. So now I have another chassis and combo cab to play with in the future... They present some different design challenges but where else could you get a matching chassis and cab for that little money? Besides sometimes they don't need tolex or other things like a handle, rubber feet, cab corners or even the chassis mounting hardware. It is usually all there... just waiting for a new circuit.

I love recycling these things... No offense to Bruce, but this amp will be WAY more desirable than the original Tweaker 15 in my humble opinion. I would buy these chassis with matching head cabs for $40 each all day long.

[dorrisant]

Ok... Here are some updated pics...

Deviations: Hi/Lo switch for the input, power tube cathode bypass attenuation using the primary voltage selector (thanks Geezer and 10thtx). Both work as they should.

The OT I used doesn't sound right... It has a harsh fizzieness that kicks in when you crank it a bit and dig in. This fizz pops on abruptly and has a wierd kind of frequency sweep that rises and falls kinda like working a wah up and down through a full cycle and dies... Very weird!

I subbed in a Dynaco clone I have here. I used the 4Ω tap on the Dynaco to get a 7.2k load as opposed to the installed OT's load of 6.4k. I don't think the difference in impedance made the difference in volume, but what do I know? I did measure 4db higher with the Dynaco. 96db as opposed to 100db. Any ideas here?

There were some different values in the dropping string from the schematic in the original post that were changed too. Seems right now.

I'm not sure I'm in love with this circuit... a new OT and time will tell. I think it looks pretty good anyway!

[dorrisant]

More...

[dorrisant]

More...

[dorrisant]

This is all for now...

[Smokebreak]

Cool amp! The bypass switching looks like a great option. How do you like it?

[dorrisant]

Thanks!

It works as advertised... Can't say if I like it or not until I get another OT in it and play... Sounds pretty good so far though.

[dorrisant]

Update: I got a used Hammond 1620 from Xtian... (Thanks again!)

Had to do some surgery but the patient has pulled through. New mounting and chase holes. I ordered the special impedance selector switch from AES/CED... so I hardwired it to the jacks for the 8Ω tap.

Very nice tone just like in this video: https://youtu.be/mcDVkB73VKc

I can understand how some have called this circuit a one-trick pony. It is like the tone stack is there to dial this one tone in... The bass control acts somewhat like a resonance control. It is not an overly bright circuit, yet the treble control seems useful even at low settings. It does get up and rock. I tried it in a 2x12 with a Vintage 30 and a Greenback. Plenty of punch for an 18 watt output. Gotta see how it cuts through in a band situation.

The cathode bypass attenuation seems very good. Tone remains relatively constant at all three settings... Glad I tried this! Even if it does change the tone maybe a bit, it is very nice to be able to cut the volume down as far as it does. If anything, it seems to maybe loose a bit of the bottom end.

Now time to go play!!