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Project Specific Discussions => Dynamic Processors => Topic started by: bernbrue on November 13, 2016, 01:03:38 PM

Title: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 13, 2016, 01:03:38 PM
Hi,
I would like to provide you with some files, information and recommendations for the NU FEDERAL 864 built based on our new developed pcb [Zayance & bernbrue].

The NU FEDERAL is our version of the famous Federal Limiter  AM 864/u. We replaced the original 6SK7/6SN7/6SQ7 tubes with 7-/9-pin glass tubes (2x 6BA6, 12AU7, 6AV6), changed the power supply and added a few options like input pad, variable output pad,  balancing trimpots, relay based true hardwire bypass, variable attack and release time, ratio and threshold pots, stereo link and so on. Here is a short video with the NU Federal on drums.

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

PCB's are available!! Click below.
https://groupdiy.com/index.php?topic=53011.msg676707#msg676707

Finished unit

(https://groupdiy.com/gallery/0/2575-070317123820.jpeg)

Stuffed  PCB
(https://groupdiy.com/gallery/0/thumb_2575-270117115410-5161693.jpeg) (https://groupdiy.com/index.php?action=gallery;sa=view;id=517)

BOM and Schematic

BOM: https://docs.google.com/spreadsheets/d/1494R_j2GwApoZcIZ743OuftWG7Q_4nS62gMaNTXq2zE/edit?usp=sharing

Schematic & BOM as PDF
https://drive.google.com/drive/folders/0B125JwaqoqLrbU5EVkRPZ0hYQ28?usp=sharing

Frontpanel

(https://groupdiy.com/gallery/0/thumb_2575-210117073909.jpeg) (https://groupdiy.com/index.php?action=gallery;sa=view;id=513)

https://groupdiy.com/gallery/0/2575-210117073909.jpeg

fpd files will be available soon.

 3HE Frontpanel  available here:
https://www.don-audio.com/NU-Federal-864-3HE-Frontplatte

2HE frontpanel (+ enclosure, IEC, XLR etc.) available here:
https://www.don-audio.com/navi.php?a=6537

Transformers

Powertransformer (stereo unit)
Primary: 2 x 115V
Secondary: 2 x 170-200 VAC 100mA, 2 x 6,3 VAC 2A, 1 x 9 VAC 1A

available here:
https://www.don-audio.com/Audio-Toroidal-Transformer-Pri-115/230V-Sek-2x-180V-2-x-63VAC-9VAC

Input:
any decent 1:1 or 1:4 transformer with secondary centertap  (test what you've got at hand)

Output:
 4:1 (10K/600R) transformer with primary centertap, typically suitable for double Triode push pull circuit. The Edcor XSM 10K/600R works, the XPP 10K/600R might be better (not tested)

!!! Forum member AVDO makes fantastic and price worthy transformers  for this project. Contact him and support his good work!!,!
Here you go: https://groupdiy.com/index.php?topic=62494.0
My personal review of his transformers: https://groupdiy.com/index.php?topic=65692.0

Heater wiring
Before you solder the tube sockets you have to solder the screw connectors for the heater supply from underneath. Only the heater connector on the top right is soldered from component side.

Fellow member “Fiat_cc” found out, that a 12AU7 as output tube works fine when changing the heater wiring for this tube.

For anybody who is interested in running this unit with the 12AU7 tubes (as a closer match to the original Federals 6SN7GT) with correct heater voltages, the mod is very simple! Just put a jumper wire from each terminal of the 12au7/12ax7 heater terminal block (this ties pins 4 and 5 together), then solder one leg of the heater supply directly to the pcb pad for pin 5, and the other to pin 9. A 12ax7 will provide too much gain running this way I think, so try the 12au7.


(https://groupdiy.com/gallery/0/thumb_2575-270117115409-512285.jpeg) (https://groupdiy.com/index.php?action=gallery;sa=view;id=516)

Measuring points
The small pads with letters from A to H are test points for measuring voltages against ground (G). Next to the tube sockets there are dots indicating pin 1 of the tube.
Here are the voltages from my prototype:
B+ = 215 V

A= 8,35 V
B= 208 V
C= 208 V
D= 155 V
E= 0,58 V
F= 0,58 V
G= 210 V
H= 210 V
Use the trimpots for aligning/balancing the anode/cathode voltages. Trimpot R9 (500R) is a bit small and should be increased to 2,5K or 5K.

Reducing potentiometer  range
The original Federal Limiter was a unit with fixed settings for attack/release and trimpots on the back for threshold and ratio, set and forget so to say. The calibration procedure is described in the original manual. When turning threshold and ratio to extreme settings (fully clockwise),  the unit (and I suppose the original unit as well, maybe someone can confirm) will start to motorboat.  These settings are just ridiculous and completely unusable. So the range of useful settings can be found more or less in the first quarter of the pot range. I strongly advise to "tame" the pots for:

Threshold Limiter: 100 K log pot plus a 400K resistor in series
Current control: 1K log pot with a 1K3 resistor strapped across legs 1 and 3. (resulting in ~ 600 R total resistance).

Tubes

2x 6BA6 (EF93)
6AV6 (EBC91)
12AU7 (ECC82)*

* The 12AU7 is supposed to be very similar to the 6SN7 used in the original unit. Personally I recommend  the 12AX7 (ECC83)  in this circuit. Please check the “heater wiring “ passage when using the 12AU7 !!

Meter
Any 200uA to 1mA DC meter will work. I successfully tested a Sifam R32 standard VU meter as well.

Reading stuff

Original manual: http://www.preservationsound.com/wp-content/uploads/2014/02/Federal-AM-864-U-Manual-copy.pdf

-------------------------------------------------------------------------

Update 5th of March:
Has anyone built it yet? I have my second channel running. Really nice what it does. Wiring needs to be cleaned up and then I'll close the lid.
Some observations:
- buy a bunch of 6BA6 tubes. I had a NOS pair in and the meter barely moved up.  With another pair the meter moved up as it should.
- when linking two channels the already slow attack/release time doubles.
- the meter trimmer is a must, since the meter is very sensitive to the threshold/ratio settings. It's recommended to find suitable settings first, switch in bypass and trim the meter to zero.

update 17th December
This compressor is indeed very special. I tested it for a few days now on different musical material (bass, drums, vocals etc.). It takes some time to understand how it reacts and what it does, since threshold and current control interact somehow. The meter needs to be recalibrated when using extreme settings. It's recommended to use a 6x2 or 4x3 Lorlin for the current control in order to have reasonable fixed settings. The threshold pot needs to be "tamed" as well.  A 200uA DC meter works fine with R10(240 Ohm). Revision 1.1 will have a 1K pot in series with R10 in order to calibrate the meter. An ordinary VU meter without an internal rectifier can be used as well.  The variable time constants (attack & release) we implemented are very useful, especially the shorter release times. I used a 1:1 input transformer (Haufe/Malotki) without input pad. Output transformer is a 10K/600R Edcor.  While I'm testing the unit and searching for some improvements, Tony includes these in the pcb layout revision 1.1.  Boards will be available after Christmas. Stay tuned!
Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 13, 2016, 01:04:03 PM
Hi,
Today I had some time to measure the NU Federal. I used RMAA in loopback mono mode, inserted the NU federal into my ADT-5MT mixer and tried to get unity gain with the input/output controls.  The threshold and ratio pots were turned fully counterclockwise so that at least the meter showed no gain reduction.

As you can see, the results for noise are very convincing for a tube unit. The frequency response with sidechain disconnected (pulled the 6AV6) is absolutely flat. The frequency response shown here is with 6AV6 inserted. The values for THD are quite high, mainly caused by the Edcor XSM transformer. Yes, it's a colour box.
Title: Re: [BUILD] NU FEDERAL PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 13, 2016, 01:10:54 PM
Reserved
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: iprovlek on November 13, 2016, 01:13:05 PM
Great bernbrue!!!
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 16, 2016, 08:55:26 AM
Black & gold :D
Bernd
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Joechris on November 16, 2016, 02:29:15 PM
Cool...7pin version...whats that mysterious input tube..?  6BF6??
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 16, 2016, 02:33:08 PM
Modern tubes throughout, first tube stage with two 6BA6  pentodes.
Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 17, 2016, 11:31:14 AM
Updated first post.
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: thomasdf on November 17, 2016, 11:32:02 AM
Wow cool project!!
Just finished mine on turret board from scratch... And I am not 100% happy with the sound yet.

Will you version be cleaner than the original?
What transformers would you use?
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 17, 2016, 11:37:45 AM
We spend about 3 month in designing and optimising the pcb layout.  The pcbs are still untested. I'll get them tomorrow and build the Limiter  in the next few weeks.  We hope that everything will work out fine and that our rev. 1.0 boards will be the last revision (as we  had it with the sta level pcbs)
Bernd
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: DerEber on November 17, 2016, 02:04:17 PM
I'd love to make a shootout against my P2P!
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: mylesgm on November 18, 2016, 06:42:25 AM
Definitely interested!
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: kosi on November 18, 2016, 06:45:03 AM
subscribed  8)
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on December 03, 2016, 01:04:11 PM
Prototype works!!!
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: rock soderstrom on December 03, 2016, 04:12:35 PM
Very interesting! Beautiful pcb, keep up the good work!  :)
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on December 17, 2016, 11:54:21 AM
Updated first post
Title: Re: [BUILD] NU FEDERAL 864 PCB OFFICIAL BUILD & HELP THREAD
Post by: DonnieDarko on December 17, 2016, 02:37:42 PM
Nice! Looking forward building this unit!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on January 09, 2017, 11:13:18 AM
Populated the second pcb, finished the frontpanel design and worked on the meter scale (see first post). Boards version 1.1 are on their way.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: DonnieDarko on January 21, 2017, 02:08:20 AM
Nice!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on January 21, 2017, 07:44:10 AM
Frontpanel arrived!!! See first post
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bancho on January 21, 2017, 06:37:53 PM
Frontpannel looks very nice  :D
Any chance for Output Level/GR switch for the meters?
Is this 2U high?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on January 22, 2017, 03:32:23 AM
Hi,
You can build it in a 2U enclosure.  The gain reduction/output level switch can be implied as well, but only with real VU meters. My meters are  200 uA DC meters with a custom VU meter scale and wouldn't work as output level meters. The way it's done in the original Federal causes a lot of distortion. So we left out the rectifier part.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: zayance on January 22, 2017, 01:46:23 PM
Hi There,

PCB's are in Stock.
https://groupdiy.com/index.php?topic=53011.msg676707#msg676707


Thanks a lot.


T.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Unit-8 on January 22, 2017, 08:08:26 PM
Hi Zayance, PM sent. Thank you.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on January 24, 2017, 03:24:36 AM
updated first post
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bancho on January 24, 2017, 05:59:48 AM
So I think I don't get it right: when using real VU meters there will be distortion? or were you talking about uA DC meter?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on January 24, 2017, 06:12:31 AM
You can strap a vu meter across any output of any audio device and distortion (thd) will slightly increase. In order to avoid this vu buffers are used.  Google JLM VU buffer. If you really need to have a meter showing  output level, then take a VU meter and connect it as shown in the original federal schematic, but leave out the rectifier diodes.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: djfatum on January 26, 2017, 11:59:48 AM
 8) 8) 8) Dual & Mono

(https://scontent-frt3-1.xx.fbcdn.net/v/t1.0-9/16265473_934548423342735_2589107638814668240_n.jpg?oh=5f2f7be1b186529daa04e8e2967dabd5&oe=59066DF9)


(https://scontent-frt3-1.xx.fbcdn.net/v/t1.0-9/16298991_934548370009407_1419463695455414893_n.jpg?oh=c586917bf63ff91f744df7a3d4895439&oe=5905339B)

Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on January 26, 2017, 12:15:27 PM
Very nice! And it's your own frontpanel design! That's what I like!
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Winetree on January 26, 2017, 02:20:10 PM
Are these cases available for sale?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: gaetan on January 27, 2017, 06:45:11 AM
Looks like a great project, Any numbers on attack and release time?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on January 27, 2017, 07:00:21 AM
I think dj fatum bought these cases including frontpanel from Frank
https://www.frontpanels.de

I haven't measured the attack/release times, but they are way faster and more usable then the original.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on January 27, 2017, 09:23:49 AM
Did some measurements today. Updated 2nd post.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: rock soderstrom on January 27, 2017, 01:34:54 PM
Thanks for the measurements!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: solderboy on January 28, 2017, 03:21:45 PM
got the pcb´s today, thanks! will start soon after some other projects.
question... whats about the sidechainfilter?  is there one and if yes at aproximitly with frequency? if not would it be possible to do one?

Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on January 28, 2017, 03:44:30 PM
Hi,
The sidechain is according to the original. I wouldn't change anything here. Build it and try to get accustomed to what it does. You'll like it.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: solderboy on January 29, 2017, 09:18:09 AM
thank you for the fast reply. i am ordering parts right now and like to go stepped. found everything exept 25k log. would it be possible to use 50k log for attack?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on January 29, 2017, 10:46:50 AM
Hi,
Either take something like 22K log or you could indeed try a 47/50k log pot.  But then you should reduce R13 to 4K7. If it works without any side effects (not guaranteed) you've got a faster attack.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Unit-8 on February 05, 2017, 01:57:45 PM
Hi Bernd,

I have a couple of questions to do about the limiter and his nature.
I would use it for mastering, but looking around on the internet I have not found useful informations or someone who has built a stereo version for this job so far.
Do you think this compressor can find a place in my mastering rig?
Then, I read about the sensitivity and behaviour of the threshold and ratio controls in this design and I saw other mono compressors derived from Fed AM864, like the Audio Dizengoff D864 or the Schmidlin Fed + have both full control of the ratio and threshold and they seem not to have this kind of problem, so I believe that it is possible by adapting a few components on the circuit to get a normal use of the controls and compressor itself without having a motor boat on board. Everything to try, I know it. Any input or help is appreciated. Thanks. Andrea
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on February 05, 2017, 02:28:34 PM
Hi,
The Federal Limiter is/was a single channel (mono) broadcasting limiter.  As far as I know there has never been a stereo version of this limiter and I've never seen this compressor in a mastering chain. A few recording engineers modified this limiter and used it mainly on vocals and bass. It became a kind of secret weapon.
The other compressors you mentioned are, same as the NU Federal, free adaptions of the Federal Limiter circuit and have shurely  been modified. They are not 1:1 copies. Our adaptation of the circuit has full control over threshold, ratio, input/output gain, attack and release. Read other threads about the Federal Limiter and you will find further information.
I don't see this unit in a mastering rig. It's indeed a very quiet compressor in terms of noise/hum, but I can't imagine that mastering guys appreciate the relatively high thd figures.
I strongly recommend to build it and then decide on your own for what purpose it might be predestined.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Unit-8 on February 05, 2017, 06:49:58 PM
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
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Winetree on February 06, 2017, 12:15:36 AM
Has anyone done a Mouser Cart they would be willing to share?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on February 06, 2017, 02:33:02 PM
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
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: zayance on February 24, 2017, 10:38:52 AM
Hi There,

PCB's are back in stock.

Quote
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.

Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on March 05, 2017, 08:28:58 AM
Finished the 2nd channel. Updated the first post (at the bottom)
Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on March 17, 2017, 01:18:57 PM
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
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Mablonowski Jarc on March 17, 2017, 04:52:04 PM
Did anybody used the Sowter 8540 600/10kCT 1:4 Mic/Line input/output transformer for this build ?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on March 22, 2017, 02:39:42 PM
I'm quite shure that the Sowter 8540 will work fine in this circuit.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: DonnieDarko on April 13, 2017, 07:36:44 AM
Hey Bernd,

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

Looking forward to set this unit up!



Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on April 13, 2017, 09:09:36 AM
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
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: DonnieDarko on April 16, 2017, 06:00:22 AM
Hey Bernd, thanks! I totally forgot I already bought some Edcors, will check em out and maybe upgrade later if they dissapoint.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: DonnieDarko on May 01, 2017, 04:36:56 AM
Hey guys,

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

(https://c1.staticflickr.com/3/2823/34377478085_e656753fea_h.jpg) (https://flic.kr/p/UnPyxp)IMG_7982 (https://flic.kr/p/UnPyxp) by Friedrich Kautz (https://www.flickr.com/photos/[email protected]/), auf Flickr

(https://c1.staticflickr.com/5/4188/34377481915_8353745535_h.jpg) (https://flic.kr/p/UnPzFr)IMG_7984 (https://flic.kr/p/UnPzFr) by Friedrich Kautz (https://www.flickr.com/photos/[email protected]/), auf Flickr

(https://c1.staticflickr.com/5/4165/33992900390_3c61725c18_h.jpg) (https://flic.kr/p/TMQuZu)IMG_7985 (https://flic.kr/p/TMQuZu) by Friedrich Kautz (https://www.flickr.com/photos/[email protected]/), auf Flickr

(https://c1.staticflickr.com/3/2808/33992901800_964c56661e_h.jpg) (https://flic.kr/p/TMQvpN)IMG_7986 (https://flic.kr/p/TMQvpN) by Friedrich Kautz (https://www.flickr.com/photos/[email protected]/), 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.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on May 01, 2017, 05:01:56 AM
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
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: DonnieDarko on May 08, 2017, 02:57:04 PM
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!



Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on May 08, 2017, 03:55:30 PM
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

Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: vitopower on June 22, 2017, 12:51:59 AM


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! 
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on June 25, 2017, 02:15:58 PM
I made a video with the NU Federal on drums. 

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

Enjoy
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: vitopower on June 26, 2017, 01:12:16 AM
Wow, NICE!   ;D Building a mono unit now I ordered parts for a while back, now I want this for stereo!  THANKS!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on August 09, 2017, 06:22:33 AM
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
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on August 09, 2017, 06:44:25 AM
Yes  ;D
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on August 19, 2017, 10:56:52 AM
Hi bernb,

I have some questions about wiring:
- For the 400k resistor in series on the ratio pot. It is necessary to solder on the cable connecting CW, W or CCW?
The deck 1 of input pot is the one on top or bottom (closest to the front - panel)?
- for the attack and the release is there a meaning for the cabling of W and CCW? Because I do not see any indication on the PCB.
- For the link should I connect each point "link" of the pcb with each other with a cable?

thank you very much
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on August 19, 2017, 12:05:50 PM
Hi,
Turn the pot with shaft towards you, solder pins downwards.  Solder the 400k to the pin fully ccw, so it's the pin on the left. Solder the wire to the open side of the resistor.

Deck 1 is the closest to the frontpanel.

Attack/release should at least be wire the same. It's up to your taste/frontpanel design whether turning cw wil reduce or increase attack/release times.

Link is as you described. Make it switchable.

Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on August 19, 2017, 12:46:24 PM
Ok thank you for your answer,
For the attack and the release the front panel is the 3U from don audio.
When I face the frontpanel, slow is to the left and fast to the right.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on August 19, 2017, 02:28:56 PM
So it is wiper/cw !
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: dogvoid on August 22, 2017, 08:40:40 PM
Hi!
Edcor WSM600/600 work well as input transformer (without HPad)?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Tubetec on August 22, 2017, 10:06:46 PM
Re Edcor as input tx .
Im working on a point to point version of the fed at the moment , any way to loose some gain sounds like a good plan . Even though theres some dc on the secondary my guess is ungapped would do fine here . Ive decided to go with a 2x50k input pot too ,wouldnt 2x500k on the secondary of the input transformer severely limit high frequencies ?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Tubetec on August 23, 2017, 12:30:43 AM
Using a chunky line transformer on the front end would be good in that you could drive a proper line level signal into it ,lack of mu metal sheilding might mean more problems with induced noise though if you have a mains tx in close proximity .
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: ChrioN on August 29, 2017, 02:34:21 AM
How come you guys use 6BA6s instead of 6SK7s used in the original? (Reason I ask is I got a crapload of 6SK7s)
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on August 29, 2017, 02:49:54 AM
We searched for a "modern" glass tube alternative. Since the 6BA6 is the successor of the 6SK7 and already worked fine as sub for the 6386 in the sta level, we thought it might work fine the NU Federal as well. Indeed it does.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: sr1200 on September 09, 2017, 05:22:19 PM
Quick question, in the BOM there are two R21s listed.  One of them is on the board next to the "from Out TX"  and is 160r. The other is a 15 K 10 W resistor which I'm not sure where it  goes.  Thoughts?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on September 10, 2017, 05:08:03 AM
The 15K 10W resistor is on the mainboard and is needed for the bias voltage. See schematic. The 160R is part of the input/output pad. Buy both.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Tubetec on September 10, 2017, 07:50:20 PM
Hi Bern,
Just wondering how would the Federal circuit work with triode connected 6BA6's or 6SK7's at the front end. If anyone has attempted such a mod Id be very interested to hear what the results were .
Thanks again for all the info in this post on pot values and attack/release mods, you've really made a silk purse out of a sows ear .
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: sr1200 on September 11, 2017, 10:40:47 AM
OK got it.  Thanks  ;D

Any further reading on what NOT to populate for a stereo build? I notice in the pics that the PS section is pretty sparse with the exception of a bunch of the bigger caps.  The only mention i saw was in one of the docs that says only populate one board, but didn't mention what exactly.  The pics of the board lead me to believe its just the V supply portion, but I'd like to confirm that.  Also, where are the connections between the two made?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on September 11, 2017, 01:05:55 PM
Hi,
You need to stuff both boards though you only need a single power supply for the relays of both boards (See picture attached to the very first post). There is a stereo link between both boards. Make it switchable. That's it.
Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on September 20, 2017, 10:37:26 AM
hi bernbrue.
I have some questions about the editing:
the first concerns the wiring of the EDCOR output transformer:
- this is an EDPOR XPP1:
on the primary input I have 1 = flat, 3 = B + and 5 = flat
on the secondary output I have 7 - 9 = 600 ohms
how should I wrap all this on the to-out-tx and the from-out-tx knowing that on the PCB there is a "point", "CT" and a location with no indications.

my second question concerns the wiring of the power transformer:
I have B +, AC and V +, AC on the PCB. On which I have to wook the 180V the 6,3V and the 9V of the transformer.

thank you very much
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on September 20, 2017, 10:41:59 AM
on the primary input I have 1 = plate, 3 = B + and 5 = plate   ;D
sorry
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on September 20, 2017, 12:35:04 PM
Please have a look at the datasheet of your transformers. I'm quite shure that you will find the answers to your questions yourself. Don't get me wrong, but it's better to understand what you do than being told which wire goes where.

The 180V is B+, 6,3V is filament and 9V is V+ for relays.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on September 20, 2017, 12:42:06 PM
ok thank you I will try to find the data sheet of the transformer
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on September 20, 2017, 12:54:16 PM
I understand your point of view but I do not understand what "CT" and "point" mean on the PCB for the audio transformer?
thank you.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on September 20, 2017, 01:00:07 PM
CT= Centertap ! It  indicates where the centertap of the output transformer is connected. The dot is for polarity. So connect the + or *  side of the input/output  transformer to this terminal.

Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: dogvoid on September 21, 2017, 04:02:00 PM
Hi!!!
I'm testing the first channel, it sounds lovely, but there are some strange things, the input attenuator, the transformer is a 8540 sowter (600 / 10k) with the same h-pad configuration as the output. Attenuates to the middle, from the center to the ccw seems to expand the sound (I do not know if it's a problem, the result I like) I've reviewed and everything is correct unless something happens with the H-Pad, you may not need it, any ideas? I have not clarified with the H-Pad calculator, which I put in Required Attenuation In DB (1 to 40)?
The VU, I used a Vintage-Meters VM-B10R https://www.don-audio.com/Vintage-Meters-VM-B10R-LED-Retro-VU-Meter-LED-Illuminated
and I can not put it to 0, it does not exceed -5, but it moves, indicates compression (and I hear it !!!) any help with this?
the release is noticeable and seen in the movement of the VU, the much more subtle attack
The voltages are OK.
Still sounds great !!! I think it was worth the investment in tubes
For 6ba6: 4 paired manleys
6av6: Heintz and Kaufman (nos) matched
12AU7: CC803 S matched tube amp doctor.

Great project !!!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 06, 2017, 06:53:25 AM
Hi guys!

I've been building my very own NU Federal compressor this week, and I have some questions. First of let me show you guys my progress! I need to cleen up my wiring, but I'm waiting for cable sleeves to show up! I've done my own frontpanel, since I own a CNC, I bought the power transformer and in/out transformers from Don-Audio.

(http://users.telenet.be/Eli-Audio/GROUPDIY/IMG_7556.JPG)

(http://users.telenet.be/Eli-Audio/GROUPDIY/IMG_7557.JPG)

(http://users.telenet.be/Eli-Audio/GROUPDIY/IMG_7559.JPG)

So as for voltage I get a few strange things?
Voltages from Power transformer: 2x197VAC, 2x10.36VAC and 7.12VAC.
I had to put 1K on both R1 and R2 to get exactly 200V DC for B+ here are my voltages measured after 10 minutes power-on.

B+ 200V

A 93.5VDC
B 51.1VDC
C 109.3VDC
D 156.9VDC
E 0.59VDC
F 0.59VDC
G 200VDC
H 200VDC

So A voltage should be around 8V? This one comes right after the the 15K 10W resistor (R27.) wich takes it's power from B+ so it's right that this voltage is around 90V instaid of 8V.
B/C are off because I think one of my 6BA6 tubes is not ok, it lights up rather hot when powered on and when switched with the other 6BA6 tube the B/C voltage switch places, I can only trim them slightly with R9 and somehow they burn R3/R4 (12K 1/2W)

note! I've only connected one ground connection to the ground of my power connector, are there any more seperate groundings I should make?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: rock soderstrom on October 06, 2017, 07:22:23 AM
Hi, I can't answer your questions but I got one suggestion. The distance between your power transformer and the unshielded Edcor transformers are pretty close. This could lead to hum problems. I would maximize this distance and move the power transformer to the right corner of your case.

Nice build, keep up the good work!  :)

Cheers!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 06, 2017, 08:21:05 AM
Hi Rock,

When I'm cleaning up my wiring I might do so. First I'll need to get it running propperly. Did you build a Federal? And you remember your voltage at point A?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 06, 2017, 08:58:54 AM
I just don't get this,

Why is point A at +/-90VDC?  And why are R3/R4 burning up? I think the tube that isn't flashing when powering up the compressor is faulty, because it's that resitor (closest to that tube) that's burning up.

to be sure, all voltages ar measured with tubes in and all pots wired? because I fired it up before I got the rest wired and voltages for B+ where higher then!

By the way, my 1mA DC meter just crashes to the right wall when power is on! Audio passes trough, all pot's seem to work, like they have audible features like louder when turning output-pot, more compression when turning input pot, attack and release works to! Just that meter doesn't show anything.

is it maybe because these tubes are not matched? I can tell they are not even the same model/brand because they look different!! Maybe this guys just sold me fake 6BA6 because there's no markings on the tube... I'll just get a couple new ones!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 06, 2017, 02:51:01 PM
Hi there,
Nice built and nice frontpanel. The specs of your power transformer are for a stereo version, where each channel has got its proper winding and power supply. For your mono version you only need 1x200VAC and only 1x 6,3V ( not 10,36VAC !!!) for the heater (wires underneath).  The 7,12 VAC are for the onboard 5V psu provided for the relays and lights. So check your heater voltage and the transformer wiring.
Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 06, 2017, 04:30:58 PM
Hi Bernbrue,

I’m using the transformer you put in the First post of this thread, it has (stated on the transformer) 2x180, 2x 6.3 for heaters and 1x 9V. But all the voltages are a bit higher when connected to my main power.

I thougt the 9V was for the relays, 6.3V for heaters and 180V for B+.

When measuring heater voltages I get 3,4V
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 06, 2017, 04:47:41 PM
Hi,
for a single channel use only one 180V and one 6,3V winding.  9V is for the relays.  Heater voltage must be 6,3 VAC, measured at the screw terminal FIL/AC. Check your transformer wiring.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 06, 2017, 05:32:52 PM
Ok,

So i mixed up my potmeters!! I had threshold and current control on the wrong potentiometer!!

These are my measurements:
B+ = 216V

A = 16V
B = 208V
C = 212V
D = 138V
E = 1.27V
F = 1.23V
G = 215V
H= 215V

Better check my other pots... ;-)
 
Edit: all potentiometers are in the right positions and now my meter is up and running too!
However, I experienced the same problem with the input attenuater as Dogvoid. No attenuation in the middle, and less signal to the cw and ccw position. So I figured out that one deck of the input pad should be reversed and now I have a proper working input attenuator, and a clean signal and a working compressor! Now I need to calibrate the voltages and maybe add this resistors to the threshold and ratio-pots!

Here's a small video of me turning knobs! (https://www.facebook.com/ELiAudioCom/videos/1136000863198412/)
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 10, 2017, 03:34:11 PM
Not to brag but i'm kind of proud of this build!

At least of how it looks because wiring could have been a bit cleaner, but I'm sure I'll get it next time. I'm waiting for new 6BA6/EF93 tubes to arrive, I've bought like 10 and hope to good pair out of them. I'm not totally aware of how one would match tubes, or if I even need to, but I'm guessing it wouldn't hurt as I can't seem to get C and B to the same voltage! This might explain that the input get's distorted when cranking the input?

I've yet to do the threshold/ratio range reduction mods

(http://users.telenet.be/Eli-Audio/GROUPDIY/IMG_7604.jpg)

(http://users.telenet.be/Eli-Audio/GROUPDIY/IMG_7619.JPG)

(http://users.telenet.be/Eli-Audio/GROUPDIY/IMG_7610.JPG)

(http://users.telenet.be/Eli-Audio/GROUPDIY/IMG_7609.JPG)
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on October 10, 2017, 03:51:24 PM
Nice work,
I have to finish mine in 2 weeks, the time that my input transformers arrived.
I did not put any PAD in entries...
I would tell you if I have the same kind of values when I measure.
What did you get in as audio for now? and what do you think?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 10, 2017, 03:53:38 PM
Hi,
What a superbly built unit!! The wiring is fantastic. Maybe I'm  wrong , but there is nothing connected to the "from Output tx" terminal ? You'll get pleasant harmonic distortion when cranking up the input.  Did you use ecc83 as output tube?
Congratulations!!!
Bernd 
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 10, 2017, 03:59:38 PM
Cool video!! Your unit works as it should!! Enjoy it!!
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: rock soderstrom on October 10, 2017, 04:06:29 PM
Very good work! Where did you buy these fabric hose?  :)
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 11, 2017, 03:36:19 AM
Hi,
What a superbly built unit!! The wiring is fantastic. Maybe I'm  wrong , but there is nothing connected to the "from Output tx" terminal ? You'll get pleasant harmonic distortion when cranking up the input.  Did you use ecc83 as output tube?
Congratulations!!!
Bernd

Hard to see, but the output TX is connected and thank you for your kind words!
I do have a couple of questions though.

Question 1: I'm having trouble adjusting the voltages between B and C, seems like the R9 (500R) trim pot is working, but it does nothing to the voltage difference between B and C.
Question 2: Do I need matched 6BA6 tubes for this build or is R9 supposed to make up for the difference?
Question 3: Are all voltages supposed to be measured with all tubes in place and how close should I have to get to  your voltages?
Question 4: My heater voltage is 6.9V in stead of 6.3V is this going to be a problem? 

Very good work! Where did you buy these fabric hose?  :)

It's MDPC-X sleeve bought at Highflow.nl (https://www.highflow.nl/modding/flex-sleeves-and-heatshrinks/flex-sleeve/mdpc-x-sleeve-small-1-meter-nl.html) for €1 per meter.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 11, 2017, 03:48:32 AM
1) try to find a nice pair of 6BA6 tubes where the voltages of B and C are quite close. Trim small deviations with the pot. Otherwise replace the 500 ohm pot with a 1 K
2) see 1)
3) yes, all tubes in (within 10%)
4) no

Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: iampoor1 on October 11, 2017, 06:19:50 AM
Hi guys!

I've been building my very own NU Federal compressor this week, and I have some questions. First of let me show you guys my progress! I need to cleen up my wiring, but I'm waiting for cable sleeves to show up! I've done my own frontpanel, since I own a CNC, I bought the power transformer and in/out transformers from Don-Audio.


This might be better in another thread, but what CNC are you using? Are you just engraving anodized aluminum? Love the look of your panel. :)
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: rock soderstrom on October 11, 2017, 06:47:27 AM

It's MDPC-X sleeve bought at Highflow.nl (https://www.highflow.nl/modding/flex-sleeves-and-heatshrinks/flex-sleeve/mdpc-x-sleeve-small-1-meter-nl.html) for €1 per meter.

Thanks!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: djfatum on October 11, 2017, 09:03:33 AM
 ;D ;D ;D

(https://scontent-bru2-1.xx.fbcdn.net/v/t1.0-9/22228574_1093504254113817_260796677114496773_n.jpg?oh=320fcec21845365c85133ba9150e533a&oe=5A3A1CC5)

(https://scontent-bru2-1.xx.fbcdn.net/v/t1.0-9/22448241_1093504584113784_144969775608730540_n.jpg?oh=e2e020b9099d9ed37134ab5b45b6d8a9&oe=5A7C7928)

(https://scontent-bru2-1.xx.fbcdn.net/v/t1.0-9/22449687_1093504557447120_3695936206242030772_n.jpg?oh=c019c30a84eeb6a093e6222613474ccc&oe=5A3E08AE)

(https://scontent-bru2-1.xx.fbcdn.net/v/t1.0-9/22406027_1093507137446862_1447781993311348345_n.jpg?oh=4b09a1bfab1d23d2c1051692f3aa8424&oe=5A450CF3)

(https://scontent-bru2-1.xx.fbcdn.net/v/t1.0-9/22309055_1093507477446828_3995743061455464103_n.jpg?oh=64747cda48eeeceb3fca85a379196884&oe=5A3DAD9E)

(https://scontent-bru2-1.xx.fbcdn.net/v/t1.0-9/22310560_1093507554113487_8261155781064642373_n.jpg?oh=0ba798fe47f2ce72acc0e437b287b5ec&oe=5A7CA56D)

(https://scontent-bru2-1.xx.fbcdn.net/v/t1.0-9/22366659_1093507960780113_2695794841934728996_n.jpg?oh=e684cf4100f32a84599081019073c58f&oe=5A6FB7E2)
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 11, 2017, 09:23:19 AM
Baaamm! Very nice!!
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on October 11, 2017, 10:52:16 AM
 :o woww ! crazy
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 11, 2017, 02:35:55 PM
Yep, you've got to love that!!

so new tubes in mine! I was able to find a couple real close to each other, now the voltages are cool!
Next up is metering, I've got a 1mA meter. But the dial wil not go upto the max value, and with extreme settings the dial is halfway the scale... not usable I would say...

What do you guys sugest?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: djfatum on October 11, 2017, 05:40:11 PM
The VU must have 200 micro amperes (1 milli amper too much)
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 12, 2017, 01:34:58 AM
The VU must have 200 micro amperes (1 milli amper too much)

Cool, that's what I thought
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 12, 2017, 11:27:02 AM
This might be better in another thread, but what CNC are you using? Are you just engraving anodized aluminum? Love the look of your panel. :)

I’ve got a BZT PFE1000PX, and Yes anodised aluminium. And thank you!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 12, 2017, 12:31:46 PM
The VU must have 200 micro amperes (1 milli amper too much)

Could you tell me what meters you bought and where you got them? I'm having trouble finding them.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on October 14, 2017, 05:13:21 AM
Could you tell me what meters you bought and where you got them? I'm having trouble finding them.

Don audio  sells them in 200 micro amperes now...
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: rob_gould on October 14, 2017, 05:34:46 AM
Not to brag but i'm kind of proud of this build!

At least of how it looks because wiring could have been a bit cleaner, but I'm sure I'll get it next time. I'm waiting for new 6BA6/EF93 tubes to arrive, I've bought like 10 and hope to good pair out of them. I'm not totally aware of how one would match tubes, or if I even need to, but I'm guessing it wouldn't hurt as I can't seem to get C and B to the same voltage! This might explain that the input get's distorted when cranking the input?

I've yet to do the threshold/ratio range reduction mods

(http://users.telenet.be/Eli-Audio/GROUPDIY/IMG_7604.jpg)

(http://users.telenet.be/Eli-Audio/GROUPDIY/IMG_7619.JPG)

(http://users.telenet.be/Eli-Audio/GROUPDIY/IMG_7610.JPG)

(http://users.telenet.be/Eli-Audio/GROUPDIY/IMG_7609.JPG)

Really great job - you should be proud!

I've been a bit out the DIY loop for a while but seeing your project had inspired me to get back to a couple of half-finished projects of my own...
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on October 14, 2017, 01:29:57 PM
Yeah, I tend to lose interest in certain projects after a while too, but most of the time it's lack of time or funding!

By the way, about the 200uA DC meters, Aaron from Don-Audio let me know he's doing a run for them, now available in his store, although they will not be available for another 3 to 4 weeks. So I bought another Weston 2521 meter, but instead of the 1mA I found a 200uA version. And I bought a bunch of strange 200uA meters just for future projects.

I ordered 4 more PCB's from Zayance for a single control stereo version and one with a mono switch and dual controls... looking forward to that, because I just spent over €1000 for all the parts!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on October 25, 2017, 04:24:15 PM
Hi everybody,
Here, finally I finished the unit.
not without trouble with my beginner errors when buying audio transformers without CT eg: thank you bernbrue for your information that allowed me to finish this jewelry without too much trouble.
indeed I say: "without much" because during my measurements I fall on these values, and this as well on the left unit as on the right unit:

B + = 230 V

A = 14.46V
B = 224 V
C = 227 V
D = 173 V
E = 1.09V
F = 1.09V
G = 230 V
H = Over Load on the multimeter.

When I turn on the beast, the two hands go up to +2 dB then go down slightly, tremble lightly then come to fix on -3db is in the center of the VU meter. knowing that I was mistaken for sensibility of Vu meter as seen before with Eliani.

If you have a small idea of what might possibly be there. I take.

Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 25, 2017, 04:35:26 PM
Either you've got a bad output tube (12AX7) or your output transformer is not wired correctly. You should have the same voltage as on G.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on October 25, 2017, 04:43:34 PM
Either you've got a bad output tube (12AX7) or your output transformer is not wired correctly. You should have the same voltage as on G.
Bernd

I bought a pair of 5751 RCA Jan NOS. I hope these are not the tubes: D
I will test that.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 25, 2017, 04:45:39 PM
Post some pictures of your build. Makes troubleshooting easier.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on October 25, 2017, 05:14:47 PM

(http://i65.tinypic.com/2aj1k08.jpg)

(http://i66.tinypic.com/71lb2u.jpg)

(http://i66.tinypic.com/1z4wuwj.jpg)

(http://i67.tinypic.com/1z3xqxf.jpg)
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on October 25, 2017, 05:26:26 PM
ok, so I just changed by 12AX7B China to test something else and the values are:
A = 14.30 V
B = 223 V
C = 224 V
D = 173 V
E = 315V
F = 357V
G = 230 V
H = 230 V

either, no more coherence with the previous results.
I also have the hands that are at the bottom right of the Vu meter and bouncing in rhythm ...
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 25, 2017, 05:26:54 PM
Very nice build. How have you connected the meter trimpots? Try to measure voltage on H once again. There must be some voltage.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 25, 2017, 05:32:02 PM
E and F are not measured correctly.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on October 25, 2017, 05:35:51 PM
E and F are not measured correctly.
Bernd

thank you ! trimmers pots are wired on CW and C.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on October 25, 2017, 05:49:02 PM
E and F are not measured correctly.
Bernd

ok, sorry E = 315 mV   
                     F = 330 mV
you think that the bouncing needle is due to bad wiring trim pots?
When I turn the threshold to the max the needle does not bounce but is fixed a little lower.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 26, 2017, 04:02:38 PM
Watch my video.  The meter needs to be retrimmed quite often. Did you tame the pots as suggested in the first post?

https://www.youtube.com/watch?v=0eJVCCYApOw
Very nice unit. Be proud of yourself !
Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on October 26, 2017, 04:22:10 PM
Watch my video.  The meter needs to be retrimmed quite often. Did you tame the pots as suggested in the first post?

https://www.youtube.com/watch?v=0eJVCCYApOw
Very nice unit. Be proud of yourself !
Cheers
Bernd


Thank you very much,
I still need to calibrate all that ....
yes I had already watched your video and the trim pot works the same way home but my meter is not assé sensible (200mA). I have to change.
all the knob is zero and the needle jumps to the max.
I will try to understand what is wrong.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on November 08, 2017, 09:46:55 AM
Hello everyone,
I have a big problem in calibrating the federal.
I do not really understand what's going on.
I checked everything and everything is well connected: trim = CW and W, thlimit = ratio, current ctrl = threshold, to-out-tx = primary, from-out-tx = secondary, link = pcb right on the spindle of the middle of the switch and pcb left on the right or left pin of the switch two positions ... etc ...).
but I have values ​​at control points that are apparently not the right ones:

B + = 230V

A = 14.54V
B = 223 V
C = 224 V
D = 173V
E = 0.32V
F = 0.33V
G = 230V

- all the tubes are lit except the 12Ax7 whose filaments are not incandescent but heats a little ...
- I always have the two hands of the Vu meters jumping right when the unit is ON.

- what are used to adjust R26, R11 and R9?
- apparently the heating circuit should power the 12ax7 in 6.3V and not in 12.6V.
- Bernbrue, on your first photo of the heating circuit at the beginning of the thread I see a small green cable soldered, that is it indispensable and what it serves it on the rev 1.1.
- Is there a test procedure to be performed without the tubes?

Thank you in advance for your answer because there I am really headed.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 08, 2017, 12:30:55 PM
Your voltages are a bit high but not wrong. I wouldn't care too much about that. Try to get the heater wiring right. You need to see the 12AX7  glow, otherwise it won't work. Maybe there is a short somewhere or the tube socket is not soldered correctly. The heater wiring as shown is correct. It's for 6,3 V. The small green wire has no relevance for you. It was just a fix on the prototype.

In case you have a few more 6AS6 tubes, I would test them out. I had a few broken ones, although they were sold as new. They have a big influence on the whole circuit.
R26 is for fine trimming the voltage for the relay. R11 and R9 are trimmers for balancing the two 6BA6 tubes and the two halves of the double triode (12ax7).
Can you adjust the meter with the pot? They should react somehow. Which value did you take for the meter trimmer?
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on November 08, 2017, 02:31:43 PM
Your voltages are a bit high but not wrong. I wouldn't care too much about that. Try to get the heater wiring right. You need to see the 12AX7  glow, otherwise it won't work. Maybe there is a short somewhere or the tube socket is not soldered correctly. The heater wiring as shown is correct. It's for 6,3 V. The small green wire has no relevance for you. It was just a fix on the prototype.

In case you have a few more 6AS6 tubes, I would test them out. I had a few broken ones, although they were sold as new. They have a big influence on the whole circuit.
R26 is for fine trimming the voltage for the relay. R11 and R9 are trimmers for balancing the two 6BA6 tubes and the two halves of the double triode (12ax7).
Can you adjust the meter with the pot? They should react somehow. Which value did you take for the meter trimmer?
Bernd


ok I will try to test with new 6BA6 tubes, I have a stock, but not 6AV6.
the 6BA6 and 6AV6 are very bright yet transparent.
when I turn the trim to the right the needle descent to the left and that for both sides.
the needle on the right side only rebonit at the beginning but the left side all the time.
when I activate the link the left needle does not bounce anymore.
and when I push the IN pot all the way to the right the needle of the left channel is also fixed.
when i try to measure the voltage at the trim terminals i have 0.5 mv turned completely to the right and 70mV to the center and 83.9 mV turned completely to the left.
the 12AX7 do not emit light at all.
can this come from a power transformation cable inversion (FIL / AC?) or I would not have the values ​​I tested if it was the case?
whether I am a link or a link, the potentiometer on the left or on the right influences both channels. weird because only the link is the link or the power transformer.
Since I only had two outgoing cables from the transformer for the 9V power supply I took two cables and came out of the 9V powered terminal block to join the other serial PCB ... maybe it was there an influence?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 08, 2017, 03:14:13 PM
That's a bit confusing. I suggest to concentrate on setting up a single channel, let's say the left channel.  Please remove any links between the two channels including the wires for 9V power.

Can you make a short video of your Federal? I would like to see, how it behaves. A close up of the inside would be nice. Double check the tube socket of the 12ax7 and also the heater wiring underneath.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on November 08, 2017, 05:17:32 PM
That's a bit confusing. I suggest to concentrate on setting up a single channel, let's say the left channel.  Please remove any links between the two channels including the wires for 9V power.

Can you make a short video of your Federal? I would like to see, how it behaves. A close up of the inside would be nice. Double check the tube socket of the 12ax7 and also the heater wiring underneath.
Bernd


ok i will make a video and cut the links. I will send you a vimeo link.
I also changed all the 6BA6 tubes by a new pack (not pair) and the needles do not hop anymore.
There is a slight light at the end of the anode and catode 12AX7 but it is necessary to put in black to distinguish them.
The others light up a lot.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on November 08, 2017, 06:18:31 PM
Here is the link to the video you asked me.
you must know that I have not yet replaced the vu meters by 200 micro amper. they are ordered

https://vimeo.com/241967119
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: skal1 on November 08, 2017, 07:21:15 PM
hi jefflehiress

that last tube has no heater voltage getting to it , check your connection on the bottom of pcb to see if the two wire's are  on pin 4 and pin 5 of that tube .

quick check, pull the tube out  of that socket ,and check from the top  , with your meter , 1 probe to pin 4 and the other to pin 9  , if voltage is their , the tube is naf ,if no voltage  , you may have a dry solder  joint in that part of the circuit.

regards

skal1
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on November 19, 2017, 10:54:37 AM
hi jefflehiress

that last tube has no heater voltage getting to it , check your connection on the bottom of pcb to see if the two wire's are  on pin 4 and pin 5 of that tube .

quick check, pull the tube out  of that socket ,and check from the top  , with your meter , 1 probe to pin 4 and the other to pin 9  , if voltage is their , the tube is naf ,if no voltage  , you may have a dry solder  joint in that part of the circuit.

regards

skal1


I finally received the vu meters of 200 micro ampere.
Skal1, thanks for your answer,
so I just measured and at terminals 4 and 5 I have 0.3V at both terminals, but the voltage is not fixed, it's up to 0.35V and it drops to 0 then goes back ... etc. ..
However all the pins of the base of the tube 12AX7 are soldered neatly.
I'm not sure I understood but basically I have to weld pin 4 and 5 together to properly feed the tube?

(http://i66.tinypic.com/6te8ut.jpg)
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on November 19, 2017, 12:07:44 PM
Your voltages are a bit high but not wrong. I wouldn't care too much about that. Try to get the heater wiring right. You need to see the 12AX7  glow, otherwise it won't work. Maybe there is a short somewhere or the tube socket is not soldered correctly. The heater wiring as shown is correct. It's for 6,3 V. The small green wire has no relevance for you. It was just a fix on the prototype.

In case you have a few more 6AS6 tubes, I would test them out. I had a few broken ones, although they were sold as new. They have a big influence on the whole circuit.
R26 is for fine trimming the voltage for the relay. R11 and R9 are trimmers for balancing the two 6BA6 tubes and the two halves of the double triode (12ax7).
Can you adjust the meter with the pot? They should react somehow. Which value did you take for the meter trimmer?
Bernd

hello bernbrue!
ok I think everything is fine now, would you have a technique or measures at particular points to calibrate step by step so that the entire stereo unit is calibrated at best?

thank you
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 19, 2017, 12:49:05 PM
There is no real step by step calibration for stereo matching. The best thing you can do is to balance  each single channel for identical voltages at the corresponding measure points. The 6BA6 input tubes are the most important part in terms of matching. Try to find a set of four most identical tubes. Search for "tube matching". Afaik it has been discussed before.
Found it in the sta level build thread:
https://groupdiy.com/index.php?topic=59017.msg807357#msg807357
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on November 19, 2017, 01:27:04 PM
There is no real step by step calibration for stereo matching. The best thing you can do is to balance  each single channel for identical voltages at the corresponding measure points. The 6BA6 input tubes are the most important part in terms of matching. Try to find a set of four most identical tubes. Search for "tube matching". Afaik it has been discussed before.
Found it in the sta level build thread:
https://groupdiy.com/index.php?topic=59017.msg807357#msg807357
Bernd

Hi Bernd
yes I had seen this topic on the 4 tube peers. and it's done for me.
notice you could watch the video I made? what do you think ?
ok, so I tested the unit with a drum, and I have a big problem of interferences and buzz. I always have the left and the right which have an influence on one another while the link is not welded. I will try to order another pair of 6AV6 just in case ...
Do you have an idea about the worries?
I will try to make a video with the sound to give an idea.
thank you.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on November 22, 2017, 01:49:53 PM
Hi Bernd and everybody,
Here is as expected the video of the Federal with audio.
I unsoldered the link, so normally there is no link between the left and the right apart from the 9V power supply connected in series.
In the video we see very well that the left channel has an influence on the right, especially when I activate the threshold.
Can you give me advice on what you hear ... the compression works well but there are some things that go beyond me like the action of the pot IN which is incoherent ...
Thank you

https://vimeo.com/244089212
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 23, 2017, 05:12:45 AM
The input pot is not wired correctly. Turned fully counterclockwise there should be any signal at all. Your unit starts to motorboat, so I assume you haven't tamed the pot range of threshold and ratio, as I described in the first post. The output pot is also not wired correctly. It is just an attenuator, I.e. there is always a signal even when turned fully counterclockwise. Check your wiring!!
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: jefflehiress on November 23, 2017, 04:27:47 PM
The input pot is not wired correctly. Turned fully counterclockwise there should be any signal at all. Your unit starts to motorboat, so I assume you haven't tamed the pot range of threshold and ratio, as I described in the first post. The output pot is also not wired correctly. It is just an attenuator, I.e. there is always a signal even when turned fully counterclockwise. Check your wiring!!
Bernd


actually, for the IN I reversed deck 1 and deck 2 and I did not tam the threshold with the 1K3 between 1 and 3 ... for the rest everything is ok, except that having unsoldered the 9V and the link I always have the signal sent in the left unit that goes in the right ... very strange since nothing is connected ... I'll see everything if it's not the XLR sockets that create a contact.
thank you for your follow in any case.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on December 05, 2017, 06:37:32 AM
Hey Guys!!

I just finished my Dual/Stereo unit! Or at least almost, but it's all very functional!!

So It's a shame I'm sitting in a boring conference about health-care (wich great in Belgium, it's practically free, but still some guy says in these harsh times we should do better!) , but at least I'm working with audio all day, every day!!

(http://users.telenet.be/Eli-Audio/GROUPDIY/Dual%20Federal.jpg)
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on December 05, 2017, 06:42:27 AM
What a fantastic build! Congratulations!
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on December 08, 2017, 05:59:01 PM
Thanks Bernd,

Although I do have a few issues!
When modding the ratio pot (Threshold [email protected]) with the 400k resistor on solder lug 1 (CCW) and the 1.3k resistor Paralleled over the Threshold (Current Control, Lug 1 end 3) the meter trimmer (1k with 240R on R10) just isn't cutting it! Even with both knobs fully CCW the needle barely goes past zero on the 200uA meter. I've upped the B+ voltage to be around 200V and that improves the situation slightly. Adding another resistor in series just lowers the range of the trimmer... So how do I get this needle up, or what's wrong here?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on December 09, 2017, 08:31:17 AM
Try reducing the 400K to 330K.  Test another pair of 6K4P.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Eliani on December 10, 2017, 04:52:56 AM
Test another pair of 6K4P.
Bernd

That's going to be it!
Since I did not yet receive my uTracer Tube-tester kit, I can't really tell which tubes are good, But when I searched my stock for some 6BA6 tubes I remember using last time, I found some new RSD EF93 tubes and those made the needle shoot past the 0dB mark!

So let's get better tubes!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: dmp on February 09, 2018, 05:56:02 PM
Here is a short video with the NU Federal on drums.

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


The video plays in fast forward when I try to watch it today.  Does this happen to anyone else?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: scott2000 on February 09, 2018, 07:03:54 PM
Yes....

I thought it was some new drum & bass stuff...... :D
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on February 10, 2018, 03:22:29 AM
Oh, need to check what’s wrong there. At least a few people watch the video.
Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on July 25, 2018, 03:05:19 PM
Fixed the video demo!! I love this compressor!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: leitmo on July 25, 2018, 03:17:21 PM
I just got a pair of v1.0 boards and some tubes.

I'm planning a stereo AM864 with one set of controls and I have some questions:

- When stereo linking what parameters are still individual operating? i assume it's Input and Output gain/att? I'd do a complete stepped control for everything

- It'd be great to have a unique 200uA GR meter. It's a crazy idea to just link both meter pads on PCB and feed meter?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on July 25, 2018, 03:39:25 PM
Honestly I wouldn’t do that. For a mono channel  you already need a dual deck input potentiometer. The link between two channels guarantees that attack and release times are more or less identical. All other parameters need to be adjusted by hand. This unit is a compressor with lots of character and definitely not a precision tool for a mastering chain. You may check our “NU VARIMU 436” with steppend controls for each parameter.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: leitmo on July 25, 2018, 05:18:07 PM
Honestly I wouldn’t do that. For a mono channel  you already need a dual deck input potentiometer. The link between two channels guarantees that attack and release times are more or less identical. All other parameters need to be adjusted by hand. This unit is a compressor with lots of character and definitely not a precision tool for a mastering chain. You may check our “NU VARIMU 436” with steppend controls for each parameter.
Bernd

Thanks for answering!

Sorry I didn't explain myself right.

I know Federal is a very colored compressor so not for mastering but stereo processing.

It would be feasible to make all parameters stepped stereo ganged rotary switches? I know I will be using 4 deck ones but is not an issue as long as I'm starting a Barry Porter Net EQ.

Channel matching is just measuring resistors and matching tubes and voltages accordingly
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on July 26, 2018, 04:48:38 AM
Basicly it is possible, although matching will be a tough job here.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on September 13, 2018, 01:23:09 AM
Sorry if this is astupid question or has been asked before...

I bought Vintage Meters VM-B10R meters, but I can’t find any specs on the LED to illuminate them, hence I am not sure how to power them. Any ideas?
I have a 9v rail on my transformer. Tap off that after the rectifier diodes? Will I need a series resistor?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Rob Flinn on September 13, 2018, 04:45:18 AM
Sorry if this is astupid question or has been asked before...

I bought Vintage Meters VM-B10R meters, but I can’t find any specs on the LED to illuminate them, hence I am not sure how to power them. Any ideas?
I have a 9v rail on my transformer. Tap off that after the rectifier diodes? Will I need a series resistor?

Probably, unless it has a resisitor already in series.   Yes, tap after rectifier diodes, and after smoothing. Without a spec most led's can take 5mA.  V=IR will give a resistor value.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on September 21, 2018, 12:14:54 AM
I opened the meter up and had a look.  The little LED board in there is loaded with several surface mount LED's and resistors.  The back of the meter says 12VDC so I hooked it up to the relay V+ rail, just post filter cap, and I get 12V and they light up beautifully.

I built this for a friend who found this page online.  I don't currently have any balanced XLR gear at home in order to test things properly, so I completed the unit, and gave it to him to have a play with.  There is a little bit of hum, which I suspect is due to filament wiring.  I didn't notice until after I had assembled everything, that the filaments swap polarity from tube to tube.  Mine are all wired with the same polarity, so that will be my first port of call to try and correct the hum.  He also thinks he is not getting enough output.  With input and output both close to full, it is sounding nice, but he thinks it is too quiet.  Voltages are all pretty good, if a little on the high side (the transformer is rated for 230V on the primary, and my wall voltage was 253V when doing measurements).  I can't quite get B and C points to match.  They are within 2 volts, but that is as close as I could get them.  Everything else matches up.  The controls appear to do what they should, but at some settings the unit starts to motor boat, and yes, I did include the fixes to try and remove that.  Any thoughts?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on September 21, 2018, 12:15:41 AM
Another photo, although I hadn't quite finished in this photo.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on September 21, 2018, 02:39:01 AM
Nice build.  :)
In order to reduce hum you should move the transformer a bit away from the XLR. You could also test another pair of 6AV6 tubes. I had problems finding a good pair. Of course you should check grounding and polarity of the heater as well.
I suppose you’ve used a 12AX7/ECC83 for output?
Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on September 24, 2018, 07:50:53 PM
Thanks Bernd.
Strangely the channel whose XLR is closest to the transformer is actually quieter in terms of hum than the other channel.
I agree though, that it is not an ideal layout.  I didn't realise the chassis was pre-cut.  It's difficult to find somewhere else to put the transformer. I could move it closer to the front of the case, down that channel in the middle, but I'm worried then that I'll start getting too close to the tubes and the signal chain on the board.  I had wanted to put it vertically on the back panel of the chassis, over near the IEC inlet, but it wouldn't fit in a 2RU chassis.

I will look at heater polarity and check grounding as a starting point. I think I have another pair of 6AV6 tubes, so I'll try those too.  Yes, I used reissue Tung Sol 12AX7 tubes.  I have plenty of 12AX7's around as I work on guitar amps quite a lot, so it's easy to try different tubes there too.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on October 03, 2018, 12:17:42 AM
OK, so I rewired the heaters and that did help marginally in reducing the hum, but it is very much still there.  One question I have is around 'ground' and 'PE' on the schematic.  Obviously PE is the physical chassis earth, and ground is the ground return path for the circuit.  I currently also have 'ground' attached to the chassis.  I've tried at the same point, and separate points to the physical earth, but I'm wondering whether perhaps I should lift that from the chassis?  Also, in the schematic, it shows 'J5' connected to 'ground'.  What is J5?
Another interesting thing is I can't seem to see the noise at the output on my scope.  There is a very small amount of noise visible, but it is not effected by either volume control (which the hum is), and it seems to be quite high frequency, where the hum is sounding to me like 50Hz (but possibly 100Hz). This makes me think it is some sort of ground loop issue, but I'm not really sure.  Another odd symptom is that putting the lid back on the chassis actually increases the hum, rather than reducing it, which is another reason I suspect grounding.  Any thoughts?

I tried unbolting the power transformer and moving it further from the XLR's but there was no discernible difference in noise. I have also identified a very microphonic 6BA6 in one channel which seemed to be causing some of the motor boating symptoms, but I tried swapping it from one channel to the other and there was no real discernible effect on the hum either, although the motor boating did seem to follow that tube.  Also, just how closely do I need to be able to match those 6BA6 tubes?  I seem only to be able to get within about 2V, which is less than 1% discrepancy, so I figure it is OK, but I'm curious.

Last couple of things... I just noticed trawling through the BOM document.  It mentions using thermal paste and an isolator for the LM317. I used thermal paste, but missed the isolator.  Could that be leading to hum somehow? Also, R27 is getting massively hot.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 03, 2018, 02:44:22 AM
The Isolator for the LM317 is mandatory!! Also check the wiring of the output transformer.  j5 is a jumper that needs to be connected to ground. I haven’t got the pcb layout in front of me. It should be on the psu pcb.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on October 03, 2018, 03:01:13 AM
Thanks Bernd.
The isolator is easy.  I can sort that out no problem.  Then I need to figure out this J5 business.  I can't see it anywhere.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 03, 2018, 03:21:43 AM
Make shure that both, PE and GND are connected to star ground. That’s a point near the IEC connector,  where all ground wires are connected to chassis and IEC main ground. So, each pcb has two ground wires going to star ground!!  I can’t find J5 either.  Seems to be a „leftover“ of  our other projects.
Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on October 03, 2018, 03:53:30 AM
Yep, PE and Ground are currently both connected to the star ground.  I double check all my off board connections to pots and transformers.  Whatever is causing the hum is the same on both boards.  Would the lack of isolation on the LM317 cause hum somehow?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on October 04, 2018, 04:16:06 AM
No, isolating the LM317 didn't solve the hum issue.  I'm starting to tear my hair out with this.  The hum is present with all 3 of the 7 pin tubes removed, but disappears when I remove the 12AX7, but I've no idea where it's getting in.  I've removed the output transformer from the chassis on one channel, and tried moving it around as much as the leads will let me, but that makes no discernible difference. Both PE and Ground connections measure well under 1 ohm from the board to the chassis, so the earth connections are good.  What else can I be missing here?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 04, 2018, 04:35:36 AM
Which output transformers do you use? How did you wire it? The 12ax7 could be bad as well. Can you measure the voltages around the output tube once again? Has your input transformer got a  centertap? Check for correct wiring.  Compare with the data sheet of your transformers.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on October 05, 2018, 12:53:57 AM
I used the Edcor  XSM 10K/600 output transformers as recommended on the first page of the thread.  Input I used  Hammond 140QEX 1:1 600ohm transformers.  The Hammond has both sides centre tapped, so I connected it on the output side of the input transformers, and just blanked it off on the input side, as there is nowhere to connect it to the board.
Output transformer I connected the centre tap on the primary side (TO-OUT-TX on the board), and left it disconnected on the  secondary (FROM-OUT-TX) connection.

The bit that is annoying me, is whatever the issue is, it's the same issue on both channels, because they both have the same hum. To me that kind of rules out a bad tube.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on October 05, 2018, 03:32:51 AM
The circuit itself is absolutely flawless. The pcb has been tested as well. So there must be a very simple, obvious mistake. Please double check the wiring of the XLRs and verify that hum is not introduced to the unit from an external source.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on October 05, 2018, 11:06:46 PM
I'm not suggesting at all there is an issue with your product.  I'm just frustrated, as I feel as though I did a good job of building this, and I cant figure out where the hum is coming from. I'm not a tube guru, but I've built my share of tube circuits successfully, and feel as though I have a sound understanding of layout issues etc.  I'm always learning of course, but I thought this one would fire right up with no issue. 

I will partially disassemble and try a few things in terms of layout etc, and triple check my wiring.
Regards,
Reuben
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: scott2000 on October 05, 2018, 11:47:35 PM
Maybe a leaky cap?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on October 08, 2018, 06:54:06 PM
Maybe a leaky cap?

Not impossible, but given that it's a 2 channel unit, and both channels exhibit virtually identical noise issues I'm leaning towards something that is shared between both boards.  I have some sheet aluminium at home, and will try building a shield of sorts around the PT.  I've just been dealing with a guitar amp build that has all sorts of noise issues due to the OT placement too.  I'm feeling it's either a layout thing, or possibly something like meters.  I may have made a wiring mistake on both boards, but I was careful with this build, and it seems unlikely.

I've put it on the shelf to concentrate on another project for a few days, and will come back to it with fresh eyes soon.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: shot on November 17, 2018, 04:48:43 PM
Hi!

I'm in the process of finding what's wrong with my one channel build.
I'll explain in the next post what is wrong and ask for assistance if I don't find the error in the meanwhile.

But I think I found an error on the pcb silkscreen!
It's in the section of output pad.
Labels on R23 and R19 are reversed.

I've drawn myself a diagram  of actual situation on the left and schematic on the right.
If you look at top left on my diagram you'll notice that R19 is connected to output pot CCW (that's supposed to be R23 on schematic) and R23 is connected to output transformer (that one is supposed to be R19 on schematic).

If you stuff the board following silkscreen labels you end up with wrong values. It works of course, but it's wrong!

I attached my hand drawn diagram (sorry for the lack of drawing skills  ???)

:)

Luka
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: zayance on November 18, 2018, 03:28:56 AM
Yes you're correct shot, silk error there.
I surely have crossed the names while cleaning the board's silk...

Sorry for the inconvenience, will add a note for this error.

T.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: shot on November 25, 2018, 09:13:17 AM
Unfortunately, I'm struggling to find free time to work on this compressor more.
I don't have a clue what's happening with compression. I don't hear it!
Meter is showing that it's compressing, attack and release slightly change the way needle on the meter is moving, but when pushed I only notice more distortion. I don't hear the compression. Os should I say, I think I hear some compression but it may even be placebo when simultaneously watching the meter bounce.
Input potentiometer is definitely not behaving as it should since whatever I do it keeps the same level. I went to check if it's connected the wrong way but it seems fine. I'll double check. Maybe that's the root of all my problems.
I'll keep you posted as I go along when I get some time to work on it.
Btw, I have 10k:10k as input transformer and at the moment I'm using 10k:150R as output. I know that this output transformer may not be appropriate but I don't think it's got anything to do with my problems at this stage.

:)

Luka
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on November 25, 2018, 12:07:33 PM
Hi Luca,
You might check the video I made from my unit and compare the compression you clearly can hear there with yours. Attack and release changes are subtle with this compressor.  I mentioned this before. Your input pot should cut down the input signal to zero when turned fully counterclockwise, whereas the output pot is just a 10dB attenuator.  Try to get the input pot wiring right, Im shure this is causing your problems.
Heads up!
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on January 29, 2019, 07:12:31 PM
Well, I rebuilt the power supply end of things and made a shield for the transformer out of light gauge galvanised steel, and the problem persists.
I’m going to strip the chassis, re examine boards and solder joints, rewire the whole front panel, and try to track down the issue.
I’m wondering about ground issues. There are two points on the board, one labelled ground, and another labelled PE with a ground symbol. I have both these points on each board running back to a single shared earth. Am I inadvertently creating a ground loop by doing that?

Cheers,
Reuben
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on January 30, 2019, 12:11:02 PM
No, the grounding seems correct. Indeed there are two points on each pcb, GND and PE, which need to be wired to a common chassis ground nearby the IEC inlet (verify that there is a solid connection to the base plate of the enclosure). This chassis ground needs to be connected to the IECs  main ground.
XLR input and output pin 1 need to be connected properly as well. Check attached picture ones again.
Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on February 01, 2019, 06:29:02 PM
I’m currently away on work again, but I’ve measured to the ground pin on the mains plug, from each ground on the pcb and am well under 1 ohm everywhere (closer to zero ohms).
One thing I did do was populate the 9v psu section on both boards, but I don’t imagine that would creat hum.
I’ve ordered new 7 pin tubes, in case there’s issues with  the old NOS tubes I originally got.

I plan to strip the whole chassis (besides the power supply which I just rebuilt and shielded), and see what I can find. It’s gotta be something causing it, so I just need to find what it is.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on February 14, 2019, 12:53:07 AM
I may have found my issue, in the heater filament wiring, so I wanted to ask a question (seeing as I now have my unit totally stripped down).  In every tube amp I've ever built or serviced running twin triodes like 12AX7's on 6V heater voltage, the filaments are always wired where pins 4 and 5 are tied together, so pin 4/5 get one side of the heater wiring, and pin 9 gets the other.  When I assembled the board, I couldn't get continuity from the terminal block to pin 9, so I hard wired that connection.  Upon deeper examination, I can see that you have pin 4 +, pin 5-, and pin 9 apparently has no connection that I can discern, so am I right in thinking you are running the heaters in series, rather than parallel?  If so, doesn't that make the heaters very under powered at only 3.15V per filament, or am I missing something in the way that you've put this together?  In any case, the way I had wired it is not in keeping with the way you have designed the board, and therefore is quite likely the cause of my hum, but I would like to understand what we have going on here with filament wiring before I reassemble everything and find out that wasn't my issue (pretty sure it is though).
Regards,
Reuben
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on February 14, 2019, 02:03:44 AM
The heater supply is  6,3 VAC with 100 Ohm resistor to ground. The wiring is in parallel. Have a look at the picture of the heater wiring in the first post and the picture attached.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on February 14, 2019, 03:15:20 AM
Hi Bernd.
The attached schematic shows heaters in series.

Each tube might be in parallel with each other tube, but a 12ax7 has two triodes, each with a 6.3v heater. If you run them in series (I.e. pin 4 and 5, with pin 9 disconnected) it requires a 12v supply (hence the 12 in the tube designation), if you connect pin 4 and 5 together, and connect one side of the heater supply to pins 4/5, and the other to pin 9, the 6v heaters are in parallel and run off a 6v supply.
I’m sure that the way you have the board made is running the 12ax7 filaments at 3.15v each.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on February 14, 2019, 04:57:28 AM
In fact, just doing some reading and found an article about running 12a-7 series tubes on starved heaters. Apparently a 12ax7 will still conduct at 3.15v heater voltage but only produce about half the gain making it similar to the output of a 12au7 running at full heater power. I am guessing this is why you couldn’t get satisfactory results out of the 12au7 that you originally designed around as being a close replacement for the original Federals 6SN7GT.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on February 14, 2019, 02:55:56 PM
I was talking about all tubes being wired in parallel. Indeed the 12AX7 is wired in series and this could have been the reason why the 12AU7 didn’t produce enough gain. Nevertheless to solve your hum problem you should do the heater wiring as shown in the first thread.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on February 14, 2019, 03:30:00 PM
I’m going to go ahead and jumper pins 4 and 5, and hard wire my filament wiring to pins 9 and 4/5 and try a 12au7 in there. Obviously your design works, but is running the tube a long way from the tube manufacturers operating parameter specifications (tube manufacturer datasheets say not to go lower than about 6v).
I’ll let you know results.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on February 15, 2019, 02:14:05 AM
I’m yet to run audio through it, but voltages are better. Cathode voltage on the 12au7’s is around 5.3 volts, which is much closer to the bias suggested in the tube manufacturers  specs sheet. Spec sheets suggests grids at -8v for a plate voltage of 250v and grids at 0v for plates at 100v, so +5.3v cathodes (grids at -5.3v) for plates at almost exactly 200v seems to be well within an acceptable range.
All other voltages measure exactly as per the original measurements for this unit, so I feel this is a step in the right direction.
Now I just need to make sure that the hum has gone, and it passes audio as expected.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on February 15, 2019, 10:19:34 PM
So, it works beautifully with the 12au7’s in it. When I plugged it up initially I only had output connected and there was some hum, and my heart sank. As soon as I connected a balanced input load, the hum disappeared. The unit is respectably quiet, and seems to compress as it should. Cranking the output gives a nice gritty overdrive too.
The client is very happy!

For anybody who is interested in running this unit with the 12AU7 tubes (as a closer match to the original Federals 6SN7GT) with correct heater voltages, the mod is very simple! Just put a jumper wire from each terminal of the 12au7/12ax7 heater terminal block (this ties pins 4 and 5 together), then solder one leg of the heater supply directly to the pcb pad for pin 5, and the other to pin 9. A 12ax7 will provide too much gain running this way I think, so try the 12au7.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on February 16, 2019, 05:36:03 AM
Completed unit in last stages of bench test and calibration.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on February 16, 2019, 05:39:43 AM
Clients are very happy with the unit. They’ve spent the day tracking, and mixing using the unit, and have had many nice things to say about it!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on February 16, 2019, 06:09:38 AM
Congratulations, Reuben. The unit looks great! Sometimes troubleshooting can be hard, but when everything is working in the end, it makes me happy as well.  Go on!
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on February 16, 2019, 06:23:09 AM
Congratulations, Reuben. The unit looks great! Sometimes troubleshooting can be hard, but when everything is working in the end, it makes me happy as well.  Go on!
Bernd

Thanks Bernd. It’s been a process, no doubt, but a good outcome for all concerned.

It’s an interesting unit. The client described it as quite transparent at some settings, when tracking guitars etc, and said you more ‘feel’ it than hear it. Then at other settings, it can give that really driven , ‘slammed’  vintage sound. A cool unit for sure.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on February 28, 2019, 08:21:01 PM
A quick question...
My client loves the unit. It’s quiet in operation, but he said it’s noisy when bypassed. Now, looking at the schematic, when bypassed, it is for all intents and purposes just shielded mic lead running from the back panel, to the board, then back again. Any ideas why this would be noisy?  I was considering connecting all pin 1 earth connections on the back of the xlrs to each other but not sure if that will help or worsen any ground loops.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: hugo on March 01, 2019, 06:54:20 AM
A quick question...
My client loves the unit. It’s quiet in operation, but he said it’s noisy when bypassed. Now, looking at the schematic, when bypassed, it is for all intents and purposes just shielded mic lead running from the back panel, to the board, then back again. Any ideas why this would be noisy?  I was considering connecting all pin 1 earth connections on the back of the xlrs to each other but not sure if that will help or worsen any ground loops.

https://www.rane.com/png/n110fig1b.png
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on March 05, 2019, 06:20:21 AM
Client informed me he fixed the issue by properly seating the IEC connector...! 😂
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: shot on April 09, 2019, 06:53:36 PM
After a lot of time doing some other projects and having some family issues that kept me off the soldering, I'm trying to get back to this compressor.

I had a few issues that I found were wiring related and I fixed that. No more problems with input gain pot. It passes signal as it should. But still there's an issue with amount of compression that my unit is experiencing.

The problem is whatever level of signal it gets, it barely touches it. I can crank up the input gain to the point distortion is very obvious. If I push more signal into it, it actually severely distorts (in a nice way!). But compression is not happening. Just some slight compression that the meter is showing but it can't be heard. Yes, I see some of it on the recorded waveform, but when A/B-ing signal it's negligible.

Also, potentiometers are very non-responsive. Changing attack and release barely does anything. I can notice when release is set to longer value it makes GR needle respond slower but there's no change in sound. Treshold may make it enter into more gain reduction on the meter but that doesn't sound any more compressed. Ratio seems as if nothing happens wherever I set it.

I've tried replacing tubes. Got 8 different 6BA6 (two pairs plus four different singles) and I tried all of them. Couple of them were crappy and just made sound more distorted and lacking low end. I guess those were dead ones or fake ones. But other didn't make any significant change. Just a bit of color change (or maybe it was placebo...).
Then I tried changing 6AV6 to a couple of the same brand (NEC) and nothing happened.
I'm using 6N2P-EV instead of 12AX7 but I guess it's not an issue. I have used this tube twice before when I had no 12ax7 and it was okay. To me it even sounds better (or again another placebo...). It is supposed to be russian equivalent.

I assumed it could be that compressor is not biting enough because I used 1:1 input transformer so I replaced it with a 1:6 transformer I had around (OEP A262A3E). That didn't help neither. It just made the unit get more volume on the input and subsequently enter into distortion earlier.
I put back the 1:1 transformer and then tried bypassing input pad - the change was similar to having 1:6 input transformer. Higher level and more distortion...

Pots are wired correctly and have their resistor added where needed. Heater voltage is spot on.

Voltages from the PSU are a bit different than what is noted in first post, but not that much
B+ 220V
A 8.15V
B 217V
C 217V
D 186V
E 1,16V
F 1,16V

G 219V
H 219V

Looks as if D is 30v higher and E/F are double than they should.
Are those voltages too off?

What can I do to lower the treshold or in any other way make it compress more?
I've watched the video posted here of the compressor in action and it's compressing  way more than mine is.

:)

Luka
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on April 10, 2019, 04:03:20 AM
Hi,
you need an input transformer with a secondary centertap, otherwise it won’t compress. Please check the wiring of the input transformer once again. Then use a ECC83 for output and test it once again. You should change the heater wiring so that both halves of the double triode get 6,3V as Reuben pointed out a few post above.
Cheers
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: shot on April 10, 2019, 10:04:26 AM
Hi Bernd,

I'm already using center tapped input transformers. Both transformers I tried are with dual primaries and secondaries wired to have center tap. But you gave me few ideas to try to measure what is going on from the secondary center tap to the grid of the tubes. I'll do some tests and also try to get a different transformer and get back with results.
thanks!

:)

Luka
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on May 17, 2019, 12:23:50 AM
So, I just seem to have an endless string of bad luck with this machine.  An input transformer died on me, and created all sorts of noise and havoc.  I now have a replacement input transformer, and channel 1 is beautifully quiet, channel 2 is slightly noisier, but seems to be usable (I think), but as soon as you engage the link switch, it gets horrendously noisy.  Bypassing channel 1 whilst linked makes the noise much worse, bypassing channel 2 makes the noise completely disappear.  Something is obviously up with channel 2 to create the extra noise when in mono mode linked mode. I would usually jump straight to grounding issues, but I can't find any (not to say there isn't one I haven't found...).  What would be possible causes for added noise on channel 2, and for the noisy interaction between channels when linked?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on May 17, 2019, 01:06:17 AM
A little more info...
The basic him in channel 2 is there immediately on power up,  before tubes conducting, so must be in the output transformer area.

Link issue disappears with channel 2 v1 and v2 removed, so possibly two separate issues.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on May 17, 2019, 02:07:41 AM
Could you explain, how you linked the two channel? I never had a dying input transformer. Either it’s broken or it works.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on May 17, 2019, 07:47:20 AM
Input transformer was just hopelessly microphonic, and far more susceptible to RF interference than the other.  I swapped channels and the issue followed the transformer. Replaced transformer, and those issues are gone.

In terms of link, I just ran the two link nodes on the boards to a toggle switch on the front panel.
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on May 17, 2019, 08:25:19 AM
Hi,
So my guess is, that something in the input tx and/or  input pot area is wrong. Probably a wiring error,  since  you already reported about microphonic input transformer. The channel link just connects the two center taps of the input transformer/sidechains. Check values/ voltage rating of C15 and C13 and the pot wiring in the sidechain as well.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: fiat_cc on May 17, 2019, 09:31:38 AM
Thanks Bernd.
New input transformer got rid of microphonics etc, and had issues regardless of which board it was hooked up to.  This link issue seems to be related to channel two, so I'll re-re-check wiring on that board and it's associated pots. 
Title: B+
Post by: Tashi on August 29, 2019, 09:08:23 PM
Hi Bernd,

What would happen with a stereo unit if I used one B+ supply for both sides? (with sufficient current and filtering - ie a 5H choke).
Would there be some interaction between the channels or would it be okay?

Thanks!
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on August 30, 2019, 02:28:04 AM
Hi,
honestly, I’m not shure, what would happen. I don’t know of any dual channel tube compressor with a single B+ supply for both channel. Parts are cheap, so build a psu for each channel.
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: Rob Flinn on August 30, 2019, 02:54:32 AM
I don’t know of any dual channel tube compressor with a single B+ supply for both channel.
Bernd

Looked at the 670 diagram much ?
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: bernbrue on August 30, 2019, 03:12:43 AM
Huh, now you’ve got me. It’s more than 10 years ago :-)
Bernd
Title: Re: [BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD
Post by: scott2000 on August 30, 2019, 06:48:16 AM
Quote

What would happen with a stereo unit if I used one B+ supply for both sides?

Collins 26U-2 has a similar thing as well I believe....