GROUP BUY: Universal Audio 176 - a 100% faithful recreation of a legend! CLOSED!

[Potato Cakes]

Update:
The unit is calibrated and sound fantastic!!!
The only problem is the hum .
It's 50hz predominant and depends from output level.
I think it's not heater problem.
Suggestions?
Thanks!

This is same issue I mentioned earlier. My problem turned out it was from the heater, which is why I installed DC heaters for both of my units. The leads from the the transformer and any off board wiring to the heater connections need to be twisted very tight, but you also have to make sure you don't pull out the windings from the transformer.

Thanks!

Paul

 

[ilfungo]

Hi Paul
I'm tryng to install dc heater for  6bc8 12ax7 12h7
have you used also for 6AL5?
What power transformer have you used?
My dubt is regardind consumption, because have read the 6.3 consumption is double in DC.

6bc8  400ma
12ax7 300ma
12bh7 300ma
6AL5  300ma

total 1.3A x 2 = 2.6A

My hammond 370x is 2A on 6.3vAC...

Thanks!

 

[Potato Cakes]

These are the power transformers I used:

https://www.ebay.com/itm/153854905331?ViewItem=&item=153854905331

Has 3A for the heater winding and an additional winding that can be either 5V or 6.3V rated at 2A. I use the 3A winding which goes to the DC heater circuit which powers all of tubes in the audio path.

Thanks!

Paul

 

[Greebok]

Update:
The unit is calibrated and sound fantastic!!

Could you send any sound sample via PM please?  :

 

[ilfungo]

Hy Greeok
I'm at home for covid 19 and don't have a samples ut I have a dgi 002 and 176 unit.
If you want send me a vocal sample or what do you want and I can process it for you...

 

[ilfungo]

Hi
I'm tryng to resolve the hum, now at accettale level
but I'm not completly satisfied....
the stange is a 150 hz noise, is the first time i've seen it and the classic 50hz...
see attached...
suggeston please...
It's not heater hum I've tryed dc 6.3 without differences...

 

[ilfungo]

Sorry for a stupid question ...
The 12ax7 and 12bh7 are connected in parallel for 6.3 Vac Heater
If I'm not wrong pin 4-5 must joined and we have
6.3 between 9 and 4
6.3 between 9 and 5
Correct?
I've noticed that now pin 4 and 5 are not connected
and I have 6.3v between 9 and 5 and 3v between 9 and 4..

 

[jeanpierreisyou]

Hey guys, almost done sourcing parts! Looking to see if anyone on here has an API 361 VU Meter, UTC 0-17 Shield and A-33 Shield? Thanks!

Also for those looking for high quality vintage design, I found a 10HY choke made Classic Tones. It's Paper Layer wound like the vintage era ones using premium materials. Made in USA. Here's the link: http://www.classictone.net/40-18082.html

Also found that Aerovox has a new name, its CD Aero. They still sell their capacitors, but still waiting on a reply to see how to purchase. Doesn't look like they have them at retail.

Hoping all the builds are great or are coming along great!

 

[Phrazemaster]

Hey guys, almost done sourcing parts! Looking to see if anyone on here has an API 361 VU Meter, UTC 0-17 Shield and A-33 Shield? Thanks!

Also for those looking for high quality vintage design, I found a 10HY choke made Classic Tones. It's Paper Layer wound like the vintage era ones using premium materials. Made in USA. Here's the link: http://www.classictone.net/40-18082.html

Also found that Aerovox has a new name, its CD Aero. They still sell their capacitors, but still waiting on a reply to see how to purchase. Doesn't look like they have them at retail.

Hoping all the builds are great or are coming along great!

PM me if you still need an API meter. Are you in the USA?

Thx,

Mike

 

[Phrazemaster]

By the way - did anyone ever find a clean copy of the schematic? The one I got, an original, is very blurry. Is there a clean crisp copy somewhere? I couldn't find it googling.

Thx,

Mike

 

[Phrazemaster]

And one more question - the Hammond 372 X power transformer puts out 620v, split that's 310v x 2. The schematic calls for 325v x 2. Is this a problem?

Thx

Mike

 

[jslstudio]

Update:
The unit is calibrated and sound fantastic!!!
The only problem is the hum .
It's 50hz predominant and depends from output level.
I think it's not heater problem.
Suggestions?
Thanks!

You shouldn't have ANY hum. The wiring should be done correctly. Look at a real unit. They ran the wires for a reason. The main
heater wires that travel to far end. Should run down the middle of the circuit board behind.
ALSO make sure the ground nut !!! That mounts the bottom circuit board is grounded to chassis! Or you will get hum!
I have ZERO hum. And I copied my 100% to original wiring ( as I also have an original ). Routing of ALL wire is very important.
John

 

[Potato Cakes]

By the way - did anyone ever find a clean copy of the schematic? The one I got, an original, is very blurry. Is there a clean crisp copy somewhere? I couldn't find it googling.

Thx,

Mike

Is the one in the build manual too blurry?

 

[Phrazemaster]

I guess I didn’t get a build manual.

Link? Or can anyone email to me?

Thx!

Mike

 

[Potato Cakes]

I guess I didn’t get a build manual.

Link? Or can anyone email to me?

Thx!

Mike

PM me your email and I'll send it over.

 

[moltenwok]

Hiya team, having trouble sourcing C1, C2, C3, C4 capacitors that will physically fit.. Any clues would be much appreciated ~cheers johnny

 

[Potato Cakes]

These are the ones I used or similar:

https://www.mouser.com/Passive-Components/Capacitors/Film-Capacitors/_/N-9x371?P=1z0z819Z1y9kvc0Z1yp7zipZ1z0wpt1Z1z0wqua

These are both 0.47uF and 0.047uF so be sure to double check the description.

For the C3 and C4, I just put the capacitor on its side and shrink tubed the exposed lead. I gave up trying to find radial film caps for those spots and just used axial ones.

Thanks!

Paul

 

[ilfungo]

You shouldn't have ANY hum. The wiring should be done correctly. Look at a real unit. They ran the wires for a reason. The main
heater wires that travel to far end. Should run down the middle of the circuit board behind.
ALSO make sure the ground nut !!! That mounts the bottom circuit board is grounded to chassis! Or you will get hum!
I have ZERO hum. And I copied my 100% to original wiring ( as I also have an original ). Routing of ALL wire is very important.
John

Thanks John!
Can you share some pics of your wiring of your unit or the real one ?
By the way,  my unit is without o-17 and A-33 screen,  I've buyer them on ebay but never received them...
Thanks!!!

 

[athnony]

Hey all, I'm running into a problem I don't really know how to diagnose. This is my first tube project so I appreciate anyone willing to tackle this with me!

Audio passing through sounds really distorted and weak. What's weird is it only happens when the unit is warmed up - it actually sounds incredible the first ~10 minutes of being powered on, then slowly devolves into this weird farty distortion...

I attached a .zip with MP3s of what's going on - just change .txt to .zip. There are three files - raw, as the 176 warming up, and when it craps out.

Wall AC is measuring at 111V - could it just be that the 176 isn't receiving enough power?

Here are my other voltage measurements:

V1 6BC8:
1 - 91.6 VDC
6 - 91.6 VDC
3 - 1.670 VDC
8 - 1.706 VDC

V2 12AX7:
1 - 163.1 VDC
6 - 152.8 VDC
3 - 1.358 VDC
8 - 1.465 VDC

R19/20 - 0.938 VDC
R23/24 - 205 VDC

V3 12BH7:
1 - 208 VDC
6 - 226 VDC
3/8 - 17.56 VDC

V4 6AL5 (in 12:1):
1 - 38.2 VDC
5 - 38.2 VDC

V5 GZ34:
4 - 286 VAC
6 - 286 VAC
2 - 340 VDC
8 - 341 VDC

V6 OB2:
5 - 107.7 VDC

R43/V6 - 107.7 VDC
R43/44 - 226 VDC
R44/L1 - 327 VDC

Edit: forgot to mention I'm using a 372X wired for 120V in the US.

Edit 2: Here's a Soundcloud link in case you don't want to download the attachment: https://soundcloud.com/anthony-lopez-14588992/sets/diy-ua-176-issues

Edit 3: how embarrassing.. I chased it down to a bad 12BH7. These things sound incredible.

 

[TubeMonkey]

Hi All,

I have two clients who want me to build a 176 for them after seeing mine. I'm wondering if anyone who had bought a kit and may not have intentions of finishing the build would consider selling their chassis kit? I know its a long shot and a lot to ask!

Thanks!

EB