NAD - AC15 style conversion - solid state meh to valvey goodness!

4114Effects

Just finished this last night ... 

Got an old faulty Vox Cambridge 30 in trade with @marktheharp a couple of weeks ago. Wasn't too fussed about the sound, but the chassis and cab seemed like a perfect candidate for converting into something full of lovely valves. Having a look through my amp parts I realised I had most of the bits for an AC15 style build. Let's face it, only a vox style circuit could go in that cab. The build kept me busy for a couple of evenings whilst the missus watched the last months worth of Holby she'd recorded ...

The circuit is based on the EF86 (drive) side of an AC15. An EF86 is a much higher gain valve than a 12AX7 and has a great fat tone. Original AC15 amps had and EF86 but they were switched to 12AX7 at some point as the EF86 can be an unreliable valve and has a tendency to go microphonic. I believe the newer Heritage AC15s have gone back to the EF86 due to popular demand as it was a big part of the Vox sound.

Controls are: gain with a pull-pot for boost, 6 way tone selector switch, cut, and master volume with pull-pot to take it out of the circuit. I managed to use the chassis from the amp by turning it upside down and enlarging the holes where the controls would have been to accommodate valve bases. The top now has a nifty ventilation grille which I left in as it looks kinda cool.

The control panel is a place holder - it's rather scruffy and will be replaced by a proper etched or screen printed one eventually.

Speaker is a Celestion G10 vintage, I pulled the old speaker out as it had a rather raspy sound and weak output. 

Valves are an old Mullard EF86, can't remember the 12AX7 but I'll probably try get a nice NOS one for that position, TAD EL84 and a NOS Tesla EZ81 rectifier.

Sounds exactly like I hoped it would. Chimey vox cleans, gritty breakup and thundering aggressive overdrive that can be smoothed out with the cut control. It's flipping loud too!

Just needs some retainer clips adding to the EL84, new control plate, a bit of a clean on the cab and it'll be out gigging with me ...

Here are some quick pics for your viewing pleasure.

 

HAL9000

Looks great. Have a Wow.

thermionic

That's the WOWest thing I've seen here for a while. Excellent work.

stickyfiddle

This is awesome!

Dibs!!!

marktheharp

Really looks great.
Well done, just a teeny wee bit jealous. .... :-\"

ESchap

Great conversion and neat looking build.   

Really useful donors these Vox solid states.  I did a similar thing with a Pathfinder, built an AC4 circuit in it.  

What plate voltage are you running on the EF86?

breadfan

That is absolutely brilliant! 

There's so many builders cloning Marshall & Fender circuits but I've come across very few making Vox style amps.

Any ideas as to why this is?

My next amp will definitely be an AC15 or, more likely, an AC30 circuit.

A Badcat is top of my list but, as well as being bloody expensive, I think they're hideous looking. 

BigMonka

Amazing! Those are some mad skills you've got there

randomhandclaps

Top work.  Really well put together.

gubble

That sir is fantastic !

 

cruxiform

Beautiful work!

equalsql

Wow, what a crackin' piece of workman ship. As an amateur pedal and amp builder myself I just love these sort of threads.

That's some very neat wiring and I like the copper ground bus.

4114Effects

breadfan said:

That is absolutely brilliant! 

There's so many builders cloning Marshall & Fender circuits but I've come across very few making Vox style amps.

Any ideas as to why this is?

My next amp will definitely be an AC15 or, more likely, an AC30 circuit.

A Badcat is top of my list but, as well as being bloody expensive, I think they're hideous looking. 

That's a good question. I guess a lot of home amp builders use kits -  and Vox style kits are rare for some reason. The popular ones are the usual culprits - 5e3 Tweed Deluxe, Fender Champ, and of course Marshall 18watt. That's why I thought I'd try something a bit different!

Vaernima

breadfan said:

That is absolutely brilliant! 

There's so many builders cloning Marshall & Fender circuits but I've come across very few making Vox style amps.

Any ideas as to why this is?

My next amp will definitely be an AC15 or, more likely, an AC30 circuit.

A Badcat is top of my list but, as well as being bloody expensive, I think they're hideous looking. 

If you're looking for a Vox style tweed thingy.
I've been using my Calrsbro VAC15 Classic for a few months. Was going for a Vox then tried the Carlsbro in store cause it was cheaper. I was really surprised.
Not the usual standard I'm used to from that company. Also has a Celestion Greenback in it which - to shock and horror....I actually enjoyed. Usually find them to flabby. But I guess on a chimey tweed style sound it works.

Nice build 4114! Neat as..!

4114Effects

Thanks!

It's a keeper, so I thought it deserved a nameplate and backplate ...

Phil_aka_Pip

Superb work sir! wanna hear it

robinbowes

Nice. Very nice.

I'm guessing you make the plates yourself?

R.

monquixote

Awesome work!

thermionic

Yes, they are very nice valves!

4114Effects

Balls, I should have known better! Ah well. 

Good spot

thermionic

Ah, it doesn't spoil the excellent job.