JHS Colour Box: Anyone have a working schematic?

[vizcities]

Back when I was more Gearslutz than DIYSB/Madbean, I had my eye on this pedal/pre - it seemed like a (somewhat) elegant, versatile alternative to shelling out for a Neve pre clone - but it sort of fell off my radar until this week, when Tape Op gave it a glowing review.  My interest is definitely rekindled, but, given that it's $400 for an analog pedal, I'm inclined to try and build one myself.  Does anyone have a schematic?  Or a gut shot of the PCB?  I can breadboard and prototype from there; I just need something to get me started, if possible.

[HamSandwich]

There is a gut shot in reply 215 in this thread

http://www.thegearpage.net/board/showthread.php?t=1370265&page=15

Good luck

[vizcities]

Yoinks - there's a lot of SMD in that gut shot (as well as plenty of blurred values).  I may not have the DIY bona fides to become this pedal's cloning pioneer, unfortunately.  Thanks for tossing it my way, though!

[HamSandwich]

It's enough to dismay anyone, that's for sure. I'd love to have something like it though. If you were really into it, check out the Neve 1073 (I think?), learn how it works then see how best to adapt it to guitar. Would probably be easier than finding and tracing a Colour Box.



...errr, probably not, actually.

http://www.technicalaudio.com/neve/neve_pdf/1073-fullpak.pdf

[midwayfair]

It's enough to dismay anyone, that's for sure. I'd love to have something like it though. If you were really into it, check out the Neve 1073 (I think?), learn how it works then see how best to adapt it to guitar. Would probably be easier than finding and tracing a Colour Box.



...errr, probably not, actually.

http://www.technicalaudio.com/neve/neve_pdf/1073-fullpak.pdf

it's really not that complicated, it's just a lot of components overall. Most of the stuff on the left is switches (rotary I think) for pads to attenuate the level, with different impedances for either the line or mic inputs. That's a good 1/3 of the schematic just within that dotted line box.

The signal is buffered, then band-split so you can control the low and high frequencies separately, and then the other half of the board has switches to set the actual frequency of the cutoffs for those two controls. Each little block is made up of a couple transistor networks, which are given later in the document, and they aren't anymore complicated than a fuzz to build. Even higher frequencies ("presence") are handled by another PCB, and there's a low-pass filter (with switches for the cutoffs) handled by a fourth PCB. There's a network on the far right to chain another preamp into the output transformer, which you probably don't need.

The electronic applications are pretty basic. Again, it's just the number of components, not their complexity.

This pretty much leaves the transformers, which (a) I think are proprietary and (b) would be very expensive even if you could buy them. There are a LOT of transformers in that preamp. Each little transistor block is transformer-coupled, and there are some really important ones at the input and output. The make-or-break in a lot of rack gear and amplifiers is the iron. You pay for performance. So while most of the effect would be cheap and easy to replicate, you're still stuck with probably a good $100-200 in transformers, depending on whether you can get appropriate ones used on a rack gear forum. $400 looks a lot more attractive now, doesn't it?

[peterc]

Hi all

I have built about 30 Neve discrete  preamps with various configurations and transformers, and I have some observations on this unit.

jhs have got a couple of things wrong conceptually.

Like the wrong spec input transformer..... the original mic pre uses a 1:4 unit while the Lundahl is a 1:10 ratio unit. They probably wanted a bit of extra gain, so upped the transformer ratio.

One of the big contributors to the sound is the Carnhill mic input transformer, and IMHO it is about 70% of the sound of the unit. The way it interacts with the discrete transistor amp stage also has an effect. I have tried 5 or 6 different transformers and the Carnhill is the one. Shure sm7, 1290 mic pre and voila, instant Matallica ;-) kinda....

The original eq is a coil/inductor style unit, which the jhs is most definitely not.
Plays a big part in the eq'd sound.

Amongst other things, those are the major ones.

But I find the bullsh!t astounding..... They are sitting in Abbey Road 2 going on about the 'console sound', and they even mention the Neve name on their product page, but to my knowledge Abbey Road have never had a Neve console. Revolution was done on Emi valve consoles. Etc, etc.

One of my 10 year projects is to build a couple of Neve gain stages and see how they overload with a guitar signal, trying different gain staging.

hope this helps.....
Peter

[peterc]

Just checked Abbey Roads' website, they have 3 Neve consoles..

Peter

[JC103]

Actually, I believe Abbey Road got their first Neve console custom made and delivered in late 1974. Just in time to track Pink Floyd's "Wish You Were Here" in studio 3. Studio 1 and 2 still had the in house TG consoles for at least another decade.

[raulduke]

The thing I don't get with this box is that the 'classic Neve recording chain' is a Microphone plugged into a Neve pre recording the guitar.

Not a guitar plugged into a Neve pre plugged into a guitar amp.

The JHS is totally the wrong part of the signal chain IMO

[dropanchor812]

If the Colour Box is still a bit too daunting for a trace, maybe the Crayon would be more manageable?  At least it looks like it doesn't have that transformer in there...

https://www.jhspedals.com/products/guitar-pedals/thecrayon/