Christmas offering.... Fairchild Valve EQ ..... ez627

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Slenderchap

Well-known member
Joined
Mar 10, 2005
Messages
617
Location
Manchester, UK
After 6 years of waiting I finally got round to finishing this project off:

AML-17-033_composite_600.jpg



It's a mono EQ made by Fairchild in the 1950's for mastering:
http://www.worthpoint.com/worthopedia/vintage-unobtanium-fairchild-627-tube-135319292

Colin
www.audiomaintenance.com
 
A thing of beauty Colin. I love the triple gang pots for the frequency selection and the good sized screened box for the PSU.

Happy Christmas

Ian
 
ubxf said:
http://www.preservationsound.com/?p=8602

THat is an incredible circuit for the era. I still have not got my head around it. The only 'obvious' part is the low roll at the input. Looks like the CF after the first stages feeds a twin T followed by and active twin T which then feeds back to the input. even the high roll is very different.

Thanks for posting.

Cheers

Ian
 
Did the magic eye tube in this EQ have any practical functions back in the day, or was it only decorative like in the Shadow Hills mastering compressor ?
 
Hear Hear!!!!!!

Nice one. I've seen it on you're website when I was browsing and thought to myself "Hey, that is a new shiny object!"

:)

Best wishes for 2017!

 
Hey Colin,

what a gorgeous Kit, looks absolutely astonishing!

I ordered one right away and if the unit sounds as good as the schematic looks, i will make sure to get a second one.

However, having build a lot of stuff over the years, I wonder if there might be an alternative to using the Carnhill iron. They are excellent transformers of course, but I have made big improvements in some of my units by swapping new small irons against old clunky stuff.

Do you have experimented with some other irons? Anything you can recommend - Western Electric, UTC e.a. ?

Thanks and really great work you did here! Incredible nice and clean layout and PSU.

Happy Easter!
 
I´ve built this unit in one very pleasant evening and have to say, this is by far the best kit I have ever seen. Also, it was one of the best and most satisfying evenings I´ve ever had cause it culminated in adding a very nice unit to my studio.

Everything is hasslefree, superbly organized and very thought through designed.

It holds ups to the highest standards.

Also, it sounds incredible. I spent a lot on nice tubes. Might be experimenting with different Input and Output Irons though, there is plenty of space left in the case, even though it will mess up the neat inner parts.
 
DonnieDarko said:
I´ve built this unit in one very pleasant evening and have to say, this is by far the best kit I have ever seen.

Wow.  Can you share photos?  It really took only one evening? How many hours?  Tell us more about it.  Why would you want to change the iron?  Intriguing.           

PS: What is the High Roll and Low Roll? 
Is it boosting frequencies only?  Or can it cut or attenuate frequencies?

8)
 
Hey Tommi,

yes, Roll is attenuation working like a smooth low or high cut. See this site for diagrams and manual of the unit:

http://www.preservationsound.com/?tag=fairchild

If you´re quick with the soldering iron, you might build this unit in 2-3 hours, the kit is giving you the components in such a thought trough manner.

I build several units, where I changed transformers and could achieve a hughe improvement in sound.

In some LA2A Builds, I used Sowter and then swapped for old UTCs.

In a Sta Level Build, I used old Collins (in) and Edcors (out), then swapped them for Sowters.

In a TG1 Build, I swapped Carnhill Inputs for some Irons pulled from some BBC Broadcast console.

All of the changes affected the sound of the unit, especially in frequencies in the high and low end. Most of the times I found this to improve the sound, but it´s a matter of taste after all. Some people discuss the benefits of different brands of transformers at length somewhere round here, so you may dive in if you interested.

I will report back as soon as my Sowters arrive for this unit and I can give first hand information about wether it sounds "better". Might post some Sound Files.
 
i recently built a pair of these and i'm delighted with them. the kits are fantastic. it felt luxurious... even the resistor leads are clipped and bent. the build guide is very clear. they were quick and easy builds. they're the largest boards i've ever worked on and it was a real pleasure. the finished units sound stunning. colin was very friendly and helpful the few times we chatted on the phone.
 
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