Unit-8

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #80 on: December 09, 2019, 08:28:57 AM »
Hi Tony,

Yes, there were no ground  connections on the input relays ... I'm the lucky one!
About my headache I used a lot of pain relief pills, so don't worry :)
Only a small tip on the input triodes (6bz7) is recommended to ground pin 9 (internal shield).
News to follow....


Unit-8

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #81 on: January 17, 2020, 10:27:55 AM »
My NU436 is working and it’s an excellent  compressor. It has a clean and transparent sound but with character.
There’s not much to say about it’s build, apart  to match the tubes (in & out) in order to avoid different levels between the two channels.
Also do not connect the 6bz7 pin 9 to ground as I said earlier, as it generates weird behavior on tubes.
And, if you use an input transformer that is not the Sowter do not jumper R144 A & B  as it’s written on BOM otherwise you short the output transformer.
Thanks guys for this great project!

echoplex

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #82 on: March 09, 2020, 07:16:27 PM »
Very interested in this project.. not too many people here seem to have done this vari-mu.
Is it possible to get some sound demos?


bernbrue

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #84 on: March 21, 2020, 04:26:58 PM »
Looks great, Holger. I think I’ll find the time to finish my prototype soon. Thank you for your support!
Bernd

electrisizer

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #85 on: April 15, 2020, 08:06:58 AM »
Here is my version:


nice!
what's your impression soundwise?
wich TX have you installed?

vitopower

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #86 on: April 15, 2020, 11:13:15 AM »
Stellar looking build, Holger.

« Last Edit: April 16, 2020, 02:08:25 AM by vitopower »

Holger

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #87 on: May 03, 2020, 04:28:39 PM »
nice!
what's your impression soundwise?
wich TX have you installed?
Sowter 3575 for IP and Sowter 1232 for OP

Ayman59

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #88 on: June 21, 2020, 06:16:05 AM »
Hey  All,  ;)

Can someone briefly explain the function of each three tubes in this design please ?
I’m in the process to build one but I like when I understand what I do  ;D

Thank you in advance guys!!
« Last Edit: June 26, 2020, 03:50:22 PM by Ayman59 »

Rob Flinn

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #89 on: June 21, 2020, 09:15:24 AM »
Hey  All,  ;)

Can soleone briefly explain the function of each three tubes in this design please ?
I’m in the process to build one but I like when I understand what I do  ;D

Thank you in advance guys!!

The 6BC8 is a vari mu valve & actually performs the gain reduction.   The 6CG7 is an amplifier valve that boosts the signal for the output tranformer & provides a strong signal to drive the side chain.   The 6AL5 is a double diode that rectifies the sidechain signal & makes into one that only goes negative.   The side chain signal needs to be negative going because by making the voltage between the grids & cathodes larger on the 6bc8 turns the gain down.
regards Rob


petermontg

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #90 on: June 26, 2020, 07:30:27 AM »
Any sound samples yet?

Love to here this in action

Best
Peter

Ayman59

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #91 on: June 26, 2020, 03:51:32 PM »
Thank you very much for your explanations Rob ;-)

electrisizer

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #92 on: June 29, 2020, 10:38:54 AM »
Im raedy for the Sowters OP TX, but they will arrive at the earliest in august :( what a production time...
as suggested i dont fire it up till then.

tubes are NOS mullard 6bq7a, siemens ecc81 and GE electron eaa91





« Last Edit: June 29, 2020, 10:48:21 AM by electrisizer »

Ayman59

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #93 on: June 29, 2020, 03:36:57 PM »
Im raedy for the Sowters OP TX, but they will arrive at the earliest in august :( what a production time...
as suggested i dont fire it up till then.

tubes are NOS mullard 6bq7a, siemens ecc81 and GE electron eaa91





Woaaaaaaw such a beauty  :o Good job electrisizer  ;)

Ayman59

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #94 on: July 06, 2020, 04:33:37 PM »
Hi folks,

Maybe a dummy question but... for the 8650 OP tx is the mumetal can option mandatory or the fully shrouded style S will make the job as well? I mean if they are mounted onthe side on the opposite side of the power trafo, is there any noisy risk?

Thx for your lights ;-)

Jérôme

Rob Flinn

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #95 on: July 06, 2020, 07:56:47 PM »
Hi folks,

Maybe a dummy question but... for the 8650 OP tx is the mumetal can option mandatory or the fully shrouded style S will make the job as well? I mean if they are mounted onthe side on the opposite side of the power trafo, is there any noisy risk?

Thx for your lights ;-)

Jérôme

I used the open frame version on both of my builds with no issues.   I also had it working with an open frame Edcor with no issues. It sounds good with both the Edcor or the Sowter.
regards Rob


Ayman59

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #97 on: July 07, 2020, 12:06:08 PM »
Thanks again for your advice Rob!  :)

Rob Flinn

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #98 on: July 07, 2020, 03:48:00 PM »
What Edcor have you used here?

I think it was an xsm 10k:600, although I'm away from home at the mement so not too sure.  People have said it isn't specced for the d.c but it worked fine while I was testing it,  I then swapped them for the Sowter.     I have experimented with a gain cell using  4x 6bc8 in parallel with that edcor too & that worked well & sounded nice.
regards Rob

electrisizer

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #99 on: July 08, 2020, 09:15:18 AM »
hello i use the don audio power trafo with 5V AC for V+ (measured 6v).

i tried the voltage doubler mod, as my relays are 12v:



but this mod and all mods ive found will generate a multiplied "DC" voltage.

in my case voltage is rised to +15V/0V (GND)DC . but this dosent seem to work... dont i need 12v AC?
by engaging the bypass switch relays dont "click"

(i havent connected the XLR or Out TX if this is important for the relay circuit)


 

Related Topics

  Subject / Started by Replies Last post
gar2520 build thread

Started by gar381 « 1 2 ... 16 17 » The Lab

339 Replies
89105 Views
Last post June 17, 2020, 10:09:22 PM
by EmRR
5 Replies
3341 Views
Last post January 04, 2010, 01:56:11 AM
by syn
210 Replies
32312 Views
Last post April 30, 2020, 07:16:15 AM
by bernbrue
2 Replies
558 Views
Last post November 03, 2019, 08:36:42 PM
by andyfromdenver