[BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD

[Unit-8]

Hi Bernd,

Thank you so much for the quick reply.
In mastering work EQs, compressors, limiters or simply a trick are welcome, with the engineer's goal to get the best result obtainable always with a touch of personal taste, you know.
I read a lot of good things about this piece of gear and all the guys who have it or just trying it were impressed using it on bass sounds, drums and vocals as well.
So I thought, if it works well on sounds as bass and drums it could be a good tool to use in studio to achieve a particular effect by exploiting his character since it is very rich in harmonics due to the special design of its circuitry plus the features you added as variable attack/release time.
I have already received the PCBs from Tony, thanks for that, and I'm ready to start to build it.
I hope that will be more than someone who wants to use it for the same purpose in order to exchange ideas and solutions to get the most out of it. Andrea

 

[Winetree]

Has anyone done a Mouser Cart they would be willing to share?

 

[bernbrue]

I think, Zayance is putting a mouser cart together.

I found a pair of NOS GE 5751 ***** in my tube box. These tubes sound so damn fine in comparison to the China 12AX7 I had used for the NU Federal. Did some work on my prototype: mounted the transformers and cleaned the messy wiring and finally tested various setting with vocals.  It's very easy to get this "straight in your face" sound. Crank up the input and you get very pleasant distortion. Love this box!
Bernd

 

[zayance]

Hi There,

PCB's are back in stock.

Has anyone done a Mouser Cart they would be willing to share?

I have done a Mouser Cart, but their sharing link is a little cumbersome, or maybe i'm not doing it right.
I remember having used links of other members that directs you to the shopping bag, and then you have the ability to
multiply full shipping bag etc... since it's usually based on mono channel/ 1pcs etc....
But my link needs a code to enter etc....
Maybe someone can clarify this, and so i can give you guys the Mouser card that goes according to the BOM.
Even if it's always better to make one, or at least have a second look, i choose parts going with their price ans specs,
you might choose something else.


Best,


T.

 

[bernbrue]

Finished the 2nd channel. Updated the first post (at the bottom)
Cheers
Bernd

 

[bernbrue]

I had a really nice session with a singer songwriter this afternoon. I tracked her lovely voice with the NU Federal inserted. Although the meter barely moved I recorded a really nice and gently compressed vocal track. I used the second channel for acoustic guitar, which really shined with this compressor.
Bernd

 

[Mablonowski Jarc]

Did anybody used the Sowter 8540 600/10kCT 1:4 Mic/Line input/output transformer for this build ?

 

[bernbrue]

I'm quite shure that the Sowter 8540 will work fine in this circuit.
Bernd

 

[DonnieDarko]

Hey Bernd,

I´m contemplating using the Sowter 9900 for Output, what do you think?

Looking forward to set this unit up!

 

[bernbrue]

Hi,
the Sowter 9900 will shurely work fine. The NU Federal is definitely a colour box, so it might be a bit overkill to use these expensive output transformers. Ask member AVDO for a pair of his transformers including the clamps! They are really great and a serious alternative to the sowters, only less expensive.
Bernd

 

[DonnieDarko]

Hey Bernd, thanks! I totally forgot I already bought some Edcors, will check em out and maybe upgrade later if they dissapoint.

 

[DonnieDarko]

Hey guys,

so Bernd asked to post some Pictures of my completed build. Here we go.

IMG_7982 by Friedrich Kautz, auf Flickr

IMG_7984 by Friedrich Kautz, auf Flickr

IMG_7985 by Friedrich Kautz, auf Flickr

IMG_7986 by Friedrich Kautz, auf Flickr

Allright. As you can see, I installed both H Pads, might get rid of the Output Pad though.

Tubes where really hard to find, I don´t know if the ones I got will hold up to the specs provided by their ebay sellers. Couldn´t find them on tubetown, TubeAmpDoctor or Banzai.

Input Iron are pulled from a small BBC broadcast console and measure and look allright. Output Iron cheap Edcors for now, might exchange them later for some bigger older stuff - plenty of room left in the case.

Mains Trafo is the one suggested by Bernd.

Meter and Knobs from Don Audio, meters where cheap alternative to Instrument Meter Specialities, where I usually buy. They are smaller compared to the IMS Roundmeters, found that out the hard way after ordering my Frontplate.

Case by NRG enclosures, to me by far the most clever cases with their mounting rails that provide easy access to the pcbs from top and bottom. Great price and delivery/engraving times too. Very precise work.

Still waiting for the last tube, then will power on hopefully tomorrow. Might have to swap some of the big resistors regulating B+ and change a oversized 100uf cap in the relais power circuit.

 

[bernbrue]

Hi Friedrich,
Very nice unit, as always. You have found a very unique frontpanel design. Indeed, Franks cases and frontpanels are superb. The tubes are easily available from tube amp doctor, voelkner or even Conrad. Please take an ECC83 as output tube. Perform much better than a ECC82. You might get rid of the input pad first and test the unit before taking out the output pad.  As far as I remember I used a 3k3 and a 1K power resistor to bring B+ down to around 200V. Please report back when you power up the unit. In case you need help for trouble shooting, don't hesitate to ask.
Bernd

 

[DonnieDarko]

Hey Bernd,

I´ll post my findings in "officially" in the forum, so other members can read your answers too as they might encounter similar issues.

I fired the unit up and checked voltages.

Everything is in a good Range, with B+ running at a stable 211V.

Relais do their clicking, tubes are heated properly and the others voltages fit also.

I can easily match B & C. G & H were on spot from the beginning, E&F could be matched to about +/- 0,05 V as the readings are fluctuating a bit on my meter. E&F and B&C are not same on both channels and it´s not possible to get them to be perfectly the same on both channels, even with trying out a few ECC83s and different pairs of 6BA6.

So technically, everything seems to be fine. Meters come up almost to zero with the adjust pot fully cranked up.

I tried some pairs of tubes and this is the best I can get so far. I saw that I already have the russian alternative you mentioned.

As for the sound -  I think I have to get rid of the pads. The meters are showing compression, but the signal doesn´t sound really compressed.

When turning the Input pot more then 3/4, strange things happen.

The output pot doesn´t do anything.

Attack and Release also not. Treshold does affect the meter when fully cranked. Ratio not doing anything.

Will get rid of the input pad an hope this will fix most of the issues with the not really working Controls…

I ordered new Irons to try out. Will report back!

Besides that - everything worked out very well. Thanks for such a great project to Bernd and Zayance!

 

[bernbrue]

Hi Friedrich,
A few things to consider:
- Attack and release controls change the compression behaviour slightly, not drastically.  There is room for 
    tweaking.
- the compressor starts compressing already before the meter starts to move
- output pot is just a variable pad (same as sta level). Check schematic and wiring once again.
- cranking up the input pot more than 3/4 results in pleasant distortion
- ratio control should  have an audible influence. Check wiring.
The input pad is not needed. Take out the resistors and solder in wire bridges as noted on the silkscreen.  The compressor needs a strong signal in order to compress. Double check the wiring of the input transformer, especially the centertap connection. Start with all controls at 12 o'clock and learn how this compressor behaves. It's not an ordinary compressor.
Bernd

 

[vitopower]

I think, Zayance is putting a mouser cart together.

I found a pair of NOS GE 5751 ***** in my tube box. These tubes sound so damn fine in comparison to the China 12AX7 I had used for the NU Federal. Did some work on my prototype: mounted the transformers and cleaned the messy wiring and finally tested various setting with vocals.  It's very easy to get this "straight in your face" sound. Crank up the input and you get very pleasant distortion. Love this box!
Bernd

Oooh, audio clips, please!!  I'd really love to hear how this thing does its thing! 

 

[bernbrue]

I made a video with the NU Federal on drums. 

https://www.youtube.com/watch?v=0eJVCCYApOw

Enjoy
Bernd

 

[vitopower]

Wow, NICE!  ;D Building a mono unit now I ordered parts for a while back, now I want this for stereo!  THANKS!

 

[jefflehiress]

Hello everyone, hello Bernb.

I no longer had 1N4002 100V 1A for D11 and D12, is it possible that I install 1N4007 which goes up to 1000V 1A instead, without that pause of problems?

Jeff

 

[bernbrue]

Yes  ;D
Bernd