DuKane 460 incl soundclip

[Racing]

Sort of a presentation post on my behalf then.
As i wrote elsewhere tube amps is what i do for a living and apart from repairs and mods i do a few what´s to be regarded as scratchbuilds a year. This DuKane then being one of them.

It being an amp intended for the US it of course sports a 110VAC powertransformer..which is a no-go around here in Europe.

Anyways. Cool looking old PA amp that somehow ended up around here for better for worse and in a rather nice nick to boot IMO.
From what i´ve understood these amps stem from the late -50´s,made in Illinios. I stand to be corrected on that tho.



To be blunt rather..."not american" to the build. No flashy signs..more to the point a rather laid back attitude. In turn..a LIGHTWEIGHT american! WTF?
Old friend asked me if i was into the piece,like the design of it..so it came to follow me home.



Right. Knobs even a blind hen would appreciate. Damn them large! Speaking of which this one is in such a nice nick that it´ll stay the color it is. Seing that it´s painted that brings cleaner and a buffer.



Yep. Output impedances we can use. Of course i´ll have to put that on regular 1/4" jacks.



After having spent a little while with Mr Google i´ve come to understand that these amps are half hot in the US. Rumour has it the output transformers are THE thing for Trainwreck builds. Then again..WTF do i know..
They seem to fetch fair money tho.

A pair of 5881/6L6´s..a 5U4 rectifier..a pair of 82´s (12AU7) and then for a friggin myriad of 83´s (12AX7). The 82´s being the phaseinverter and what not. A concertina/cathodyne.







Uhu. All labels intact.





Yep. The stock thing is an aircastle alright.



Stock PT has taps for 110VAC and 127VAC...so out my trusted 10A variac came. Yep. The thing had survived the trip over here sometime way back i guess and i presume that tells for the minimum wear. It being equipped with a PT for US wall voltage. IOW not an issue in my case,at least not as firing the thing up.



Checked various resistor values and so forth and..it all checked out.
So i just jumpered a Cliff jack in there..for "Mic1" and then pulled the transformer for it (they´re of the variety that plugs into a regular octal socket) and that way i got a 1M gridleak for first hit.
TBH these things friggin ROCKS as is! As a sort of one trick pony i´d even say they´re the ticket as is.

First up now..a PT for Euro voltages. A converter transformer is simply out. To cumbersome to haul around for anyone sane..

[Racing]

Picked the thing apart completely and out the cleaner and buffer came. Cleaned right up



New Belton sockets throughout as well as fasteners.



Them there white "towers" are ceramic resistors and as they measure as they should and fit the bill i´m gonna keep them. Like the idea of having them on the outside-heat n all.
Then for a trio of fresh e-lytes. 500V JJ ones.

So? What powertransformer then? Looked around a bit..and asked my vendor. Turns out he had just the ticket standing around so...a brand new one i guess it is. Intended for a 45-50w "Marshall" really which hands me 350-0-350 and 5V@3A and in turn all the 6,3V i could ever ask for. Not as expensive as one´d think all said and done either.



Yep. Even the hood of it got a first hit too.

[Racing]

Twin 6L6´s in push-pull. Run at approx 450VDC.
50 watts all said and done maybe?



What i have in mind is this optional 4 stager i´ve been playing around with a bit lately that´ll feed into an ECC-82 (12AU7) setup as a longtailed pair..heading into a triode each of yet another ECC-82 as cathode followers.



Pilot light i moved to the other end of the chassis,by the mains switch. Hole left i opened up and installed the input jack into.
Knobs have hade a good scrubdown..and fresh pots to boot.



The new powertransformer. Endbells of both x-formers will come off and be handed a dab of red paint. Specs for the PT per above.



Sockets for the ECC-83/12AX7´s have shields. No idea if it´ll be needed but rather safe than sorry i guess.



V1 is rubber suspended. As stated...that 4 stager i´ve played around with a bit lately...no idea if it´s really needed but seing how easy it is to do at this stage..why not? Sure won´t hurt anything and IF it turns out that vibrations would mock around with V1..we´re safe by this.



Ah. Yes. A small bias board with individual pots for respective powertube. The PT lacks a bias tap why the tube rectifier socket has been equipped both with "saver diodes" and drop resistors for bias voltage out.
Them small boards there...like those. Compact to say the least and does the job.



Bias board in place. Color coded wiring vs the powertubes,thus simpler to tell which trimpot does what,even down the road. In turn a "hum dinger" for the heaters.. Fuses for both heaters and HT. Saver diodes installed to the tube rectifier socket as are drop resistors for bias AC voltage out vs the board.



Wiring is per definition rather unsexy. The use of small pieces of shrink sleeve to keep the bundles tight..is a rather good idea IMO.



Again. And again..and again. There´s NOTHING as boring with a new build as laying heater wiring down. The more reason to be anal about it as that keeps one from doing it over.



Yep. Reusing the stock tagboard for the Geloso 3298 as it´s long enough to room all the components needed for the build.

Atop that i´ve installed an extra noval,idea being that if i feel the need i´ll put together a loop...

[Racing]

Wiring of the OT was shot right. Dryrotted,so while at it and them endbells being off anyways.. I hope that red will become a sort of "clash" through the hood.



Yep. Endbells came off the OT for some paint too. PT was covered with some sort of Hammerite tho and..i didn´t bother taking that off.



Mm..i believe the word of the day would be...full. That socket closest to us has been added. Is to become a loop. Or..more to the point driver in form of a cathode follower and then a regular gainstage for recovery.
Anyways. As you can gather lots got done today rendering that there´s not all that much left to do. Ie;i hope to hear this thing scream come tomorrow.



Uhu. All said and done it turned out there was 4/8/16 Ohms taps. In turn one of them "Aux" holes there will get a tele stereo to control high/low gain via footswitch.



Yep. Fabbed a piece of aluminium to cover up all the old holes out back. Safety thinking if you wish...



Yes. Gonna go James this time out too. Have a few ideas up my sleeve this time tho. We´ll see where it all ends up.



Yep. The high/low gain switch on the facia. Run by a switched 5VDC transformer that controls a few H11 optos. The whole thing works very very well...



Yep. We need a footswitch jack for the thing too. That simple isn´t it? High/low gain,indeed.



Now. It sports a tube driven loop too right and the jacks for that i´ll install in the former holes for Mic input. Or..two of them at least.



So? Summary is simple,this piece of kit rocks to the point where it´ll split your head wide friggen open! Played around with resistor values for the two cathode followers downstream of the PI buuuuut..waste of time really.
PI in turn i decided on an ECC-83/12AX7 all said and done after all. The cathode followers tho are a ECC-82/12AU7. Amp is REAL overtone prone and very easy to work with IMO.
Does what it should and atop that surprises you a bit every so often. B+ came all in at 420VDC@40mA per powertube. That said i tried another 5U4...the one in there is good to go is all i can attest to.. In turn i tried a GZ34/5AR4 which of course made voltage jump a bit but..that made the amp a tad to stiff IMO so back in the original 5U4 went.

Summary impression is very good the little i´ve used the amp tonite. That and..it´s wide. Them switches that lets you change values for the James truly brings something to the party and seing my background i absolutely LOATHE when there´s trix and gadgets that amounts to zip. If it´s there..it HAS to perform something. Period.

420VDC...then please be adviced that i use 47V zeners in series with 100 Ohm resistors vs g2. Yes. It DOES indeed make for a difference (see above).

Within that James i´ve replaced the "separation" resistor with a 470k Ohm trimpot which makes it a breeze to tailor the amp for whatever player or guitar. Yep,again a feature that actually DOES something.
Amp feels real vivid for lack of better words. The difference in how the PI is loaded i guess is part of that..

The FX loop then. Thus far the tube in Q is up and running. Component choice is a compromise thus far as the jury´s still out as if the tube´ll be an ECC-81 or ECC-82 (12AT7 or 12AU7). In short that actual socket/tube is up and running just that i haven´t hooked anything to it yet. Remains to be done in short.

I put the thing on a scale and it pegged at a mere 11kg. Seing the physical size of the thing and the power it omits AND in turn country of origins i´d say that is way fair. Good even.

Next up then..evaluate the thing further (giving thought to yet another switch for the James for instance) and make that FX loop active.

[Racing]

Yeah yeah..needs a couple of knobs and some proper labeling but...for an amp this turned into. Every now and then you put together an amp that has that "effin" factor,and this one´s one of those.
It to the letter SCREAMS in lead mode.
It all came full circle as i installed that ECC-82/12AU7 driven loop and tossed a few tweaks at it. Just..amazing.



Yep. Send and return adjustments. The loop is serial if there ever was one why that ECC-82 contributes to the overall picture....and that picture is simply magic.
This thing´s got sustain for friggin DAYS and it is an overtone friggen MONSTER!



I took to installing one of them old design "Fender" carrying straps. Don´t really know if that was the hot ticket? Mind you this thing´s got "carrying handles" on its sides,ergo that strap really isn´t absolutely needed.
Well. Nevermind any and all carrying straps...

This thing will as of now to the letter split your head wide friggen open. It is out of this world even. Thus i need to check various parameters and what not and write these down (otherwise i almost never do,carry it all in my head) as this thing...wow. Just wow.

[Racing]

[video]https://www.youtube.com/watch?v=wKL1yJGFY7k&feature=youtu.be[/video]

´N here ya go! Full swing.

[Marc G]

very cool.... the Fire Alarm manufacturer my company represents actually bought over Ducane many years ago, I use their 125 and 250 watt amps for our Fire Alarm PA installations

[clipless bumper]

nice write up - but what is James?

[itchyfingers]

Damn, I have no clue what most of that content means, Racing - but it was a cool read nonetheless. The amp freakin screams!

[Racing]

Thanx guys!

A James is short for James network. Sry i wasn´t more explicit. A James network is a type of tonecontrol,as in contrast to a way more common "stack" that we mainly find in Fenders,Marshalls..Vox and what not.

Some claim the James network to be the passive version of yet another type of tonecontrol,the Baxandall (and hence,the Bax is an active tonecontrol).

For a more in depth look at it google.

[Riffraff]

The amp sounds great but that's no surprise, your amps always do. I enjoy looking over your tube PA conversion stories for their great detail and top notch work. No EF86 in this one but shock mounted socket none the less eh? That looks like a fun amp, congrats.

[ajaxlepinski]

Totally awesome write up and the amp sounds killer!!!

"aircastle"

Adding a bias circuit, fx loop with in & out volume controls, foot switch -and- 4, 8, 16 ohm speaker outs? F 'n A brilliant!!!!

[Racing]

Thanx guys.

@ RiffRaff.
Yeah. Small signal pentodes like the EF-86 carries some inherent does and dont´s. Suspending V1 in a highgain setup however is always a good idea really.
Most hardcore such factory solution i´ve ever run across was a Dynacord Reference 502 where the entire thing is suspended mid air by four springs.



This is an ECC-83/12AX7 amp too. Cumbersome is the word that comes to mind but TBH the Dynacord Reference series is THE most hardcore tube amp i´ve ever run across from a tech POW. Ugly as hell but DAAAAAAAAMN for a build!