Western Electric 111c wiring/parts help for a passive color box

[analogggman]

I recently acquired some Western Electric Transformers to use making a transformer color box. Can someone point me in the direction of the diagram for how to wire it up. I know there are a couple iterations based on ohmage, but I figure there's already an accepted standard that's best for mix bus duties.

Also, what components as far as switches would be good to use as attenuators on the output? Would standard neutrik balanced TRS work well as my input/output jacks?

 

[dmp]

It depends on what you want it to do. I built a box with a pair of 111c with both XLR and TRS in/outs
Plugging a TS into the TRS lets you convert unbalanced to balanced with the 111c.
Putting XLR in & out just sends your mix through the transformers.
(I can't even tell they are there when I do this.)

You can wire them 600:600 for unity or 600:150 for a -6dB drop. To put this in a single switch on the panel I think I used a 4pdt switch.

I did not use anything for level control, but you could try a 600 Tpad attenuator like this or a cheap 1k pot across the secondary.

 

[analogggman]

It depends on what you want it to do. I built a box with a pair of 111c with both XLR and TRS in/outs
Plugging a TS into the TRS lets you convert unbalanced to balanced with the 111c.
Putting XLR in & out just sends your mix through the transformers.
(I can't even tell they are there when I do this.)

You can wire them 600:600 for unity or 600:150 for a -6dB drop. To put this in a single switch on the panel I think I used a 4pdt switch.

I did not use anything for level control, but you could try a 600 Tpad attenuator like this or a cheap 1k pot across the secondary.

I think I'll probably just stick with the TRS jacks. I'm planning on using it for mix bus. Can you explain exactly what you meant what the XLR does versus the TRS? you said you can't tell they are there. Do you mean the transformer expects to see an unbalanced signal? Like what is the difference audio wise. Sorry, slightly confused. Also, what did you do for the ground lift? I saw some boxes don't have them.

I was thinking of just using it as unity gain. and have the potentiometer for rolling sound back if I wanted to drive into it.

Also do you have a diagram with the numbers? Like where to wire in, out, ground etc? I'm not sure how to read the numbers alone.

Thanks for reply.

 

[dmp]

TRS is enough - I meant that if you plug a TS into the TRS, it functions as a unbalanced to balanced convertor. The ground lift switch is also for interface purposes, it lifts the ground between the input and output sides. If you just want to use it on a mixbus, balanced in and out, you can ignore that.
The transformer is fine with the balanced signal in XLRin 2,3 go to 111c 4,7 (bridge 3-8) and 111c 2,5 go to XLRout 2,5 (bridge 1,6). This gives you 600:600, level out = level in. I did attach a diagram of the 111c, but it is not on my post above. Trying again. You can find it with a search ("western electric 111c diagram")
If you want to attenuate the output, try a Tpad.
When I said I can't tell they are there I meant when I put the transformers in on a mix bus and then bypass them, I can't hear any difference. You might. But the 111c is a really good transformer. It can take a really high level without any distortion.

 

[emrr]

Mine are set up only with a 620Ω load resistor switch, I always leave it off. Everything sounds only slightly more 'Back in Black' in the low mids. They'll take +30dBm at 20Hz or lower, so you need something like a Quad Eight output stage to get them hot. Most stuff won't do it. They're super flat whether or not there's a load on them.

 

[analogggman]

TRS is enough - I meant that if you plug a TS into the TRS, it functions as a unbalanced to balanced convertor. The ground lift switch is also for interface purposes, it lifts the ground between the input and output sides. If you just want to use it on a mixbus, balanced in and out, you can ignore that.
The transformer is fine with the balanced signal in XLRin 2,3 go to 111c 4,7 (bridge 3-8) and 111c 2,5 go to XLRout 2,5 (bridge 1,6). This gives you 600:600, level out = level in. I did attach a diagram of the 111c, but it is not on my post above. Trying again. You can find it with a search ("western electric 111c diagram")
If you want to attenuate the output, try a Tpad.
When I said I can't tell they are there I meant when I put the transformers in on a mix bus and then bypass them, I can't hear any difference. You might. But the 111c is a really good transformer. It can take a really high level without any distortion.

Thanks very much for the detailed reply. I'm hoping to use them for the subtle coloration I have heard in some demos. The ever so slight high end roll off and gelling of everything.

Is it redundant to install the output Tpad since the headroom is so high?

Am i right with the diagram below?

Last question (I hope lol), I was considering making a wooden box and just shielding the inside. See any issues with that?

 

[thomasdf]

I used to have a pair wired simply 1:1 for color, too. They needed to be hit CRAZY HARD hard in order to impart that tasty harmonic saturation / compression... Too hard for my taste and setup, so I ended up selling them for a good amount of money. I lended them to a famous mastering engineer here in France, and even he said the headroom was a little too high for his taste, using them fully passive..

You could build a super powerful and clean amplifier stage, fixed gain, and attenuate as much after the transformer. But don't be shy with gain ...!

Transformers are shielded so if you keep everything passive with shielded wires, no need to shield the box.

 

[dmp]

That diagram is correct for 600:600
If you want to be able to drive them hard (~30 dBm) then you will need to attenuate the output to be able to bring it back in.
30 dBm = 20 dBu, so you'd need a amplifier able to drive 20 dBu (or more) and you'd probably want to have at least -20dB to attenuate, which is 1/10.
You could build a stepped switch attenuator with resistors or get a Tpad attenuator or just a pot to cut the level on the output.
It's not redundant at all if you plan to drive the 111c at greater than +4 dBu and don't want to clip on the way back in.
Do some experimenting
And yes they are shielded so the box doesn't matter. You can just use pigtails if you want.

 

[analogggman]

What would be a good pot besides a Tpad? I read somewhere someone liked 100k linear pot. Is there a tonal difference in using the Bourns Tpad? I don't want to sacrifice anything since it's mix bus.

Since they are shielded it would probably be cooler to expose them on the top. The transformers look so big and cool to hide them! lol

Seems like I have everything sorted. Just need to order the parts now other than the pots. Thanks again for the help. Any other suggestions? Maybe a bypass switch. I guess i would need a 3 way toggle switcher for that. Standard switchcraft should work i presume.

 

[dmp]

What would be a good pot besides a Tpad? I read somewhere someone liked 100k linear pot. Is there a tonal difference in using the Bourns Tpad? I don't want to sacrifice anything since it's mix bus.

I wouldn't expect much tonal difference. The advantage of the Tpad is it maintains a impedance of 600 ohm throughout the travel. If you just stick a 1k ohm pot across the secondary and output from the wiper, you will have some changing impedance. It's up to you if you want to try the $0.75 pot first and decide if you can hear a difference before ordering the $31 part. I would suggest a audio (log) pot since human hearing is log scaled.

A bypass switch needs to switch the (+) and (-) of the input and output XLRs, so each transformer needs a 4PDT switch for bypass. Having a single switch for both L&R would probably mean using relays since to find a rotary switch with 8 decks would be difficult. Not sure about Switchcraft but C&K like this

I used something much cheaper FWIW

 

[dandeurloo]

I put 4 in a 3U with the impedance wired to the front panel. I wired them to my patchbay.

They get used more then often enough in tracking, mixing and mastering to have made it worth it!

 

[emrr]

What would be a good pot besides a Tpad? I read somewhere someone liked 100k linear pot. Is there a tonal difference in using the Bourns Tpad? I don't want to sacrifice anything since it's mix bus.

If it's mix bus, you need to build stepped pots for accurate stereo. Or be prepared to do alignments with tones every time you change something.

Mine just have pigtails, sitting behind the rack.

 

[waltzingbear]

If you want color try a different transformer, this is the wrong choice for that. UTC A series will give you more color at much less cost.
We used the 111C coils because they DON’T distort.
They do make an absolutely lovely MS box.

Cheers

 

[analogggman]

If you want color try a different transformer, this is the wrong choice for that. UTC A series will give you more color at much less cost.
We used the 111C coils because they DON’T distort.
They do make an absolutely lovely MS box.

Cheers

I definitely plan to make more. The 111c struck my interest for mix/master bus for the exact reason, they do not distort. To my ear (from the comparisons I have heard) it does sound like it ever so slightly creates a euphonic effect.

What are some other options besides the UTC a-20

 

[analogggman]

If it's mix bus, you need to build stepped pots for accurate stereo. Or be prepared to do alignments with tones every time you change something.

Mine just have pigtails, sitting behind the rack.

Yeah, my plan is to just align with some test tones. I picked up some bourns Tpads, and can swap out in the future for stepped if need be. Where's the best place to get quality stepped pots?

 

[analogggman]

I put 4 in a 3U with the impedance wired to the front panel. I wired them to my patchbay.

They get used more then often enough in tracking, mixing and mastering to have made it worth it!

Do you mind describing the impedance wiring switch setup?

 

[analogggman]

I wouldn't expect much tonal difference. The advantage of the Tpad is it maintains a impedance of 600 ohm throughout the travel. If you just stick a 1k ohm pot across the secondary and output from the wiper, you will have some changing impedance. It's up to you if you want to try the $0.75 pot first and decide if you can hear a difference before ordering the $31 part. I would suggest a audio (log) pot since human hearing is log scaled.

A bypass switch needs to switch the (+) and (-) of the input and output XLRs, so each transformer needs a 4PDT switch for bypass. Having a single switch for both L&R would probably mean using relays since to find a rotary switch with 8 decks would be difficult. Not sure about Switchcraft but C&K like this

I used something much cheaper FWIW

Why wouldn't a 3pdt work? I thought you just need positive, neutral and ground for each. Is the bypass worth it that overkill? What scenarios would I need it, other than A/Bing? seems like I could just A/B in the DAW. Is there a page someone posted on how to wire that?

What kind of switch is needed for the ohm switcher? Thanks again for bearing with all my questions.

 

[analogggman]

Ok so does this look right for the bypass switch? I was thinking you meant there would be a 4pdt for each channel.

Also, ignore the mono jacks, I'm going to use stereo jacks and just bridge the negative and positive.

 

[Gavin Pursinger]

Thanks for this post. I have some line level xformers out of a beat to crap Sunn mixer I plan to gut and experiment on the outs of my yamaha pm 3500.
This has been VERY helpful especially the link to the 600 ohm T pad....

 

[dmp]

Where's the best place to get quality stepped pots?

People make them from stepped switches usually. If you don't want to make them, check out goldpoint or daven

Do you mind describing the impedance wiring switch setup?

You have the 600:600 wiring figured out, which is the primary and secondary both series. To switch to 600:150, switch the secondary to parallel.

Why wouldn't a 3pdt work? I thought you just need positive, neutral and ground for each

You have balanced signals so there is a (+) and (-) coming in on each XLR. You don't have to switch the ground, but you do have to switch the (+) and (-), so each needs a 2P. For full bypass, then you need 4PDT for both left and right.

Is the bypass worth it that overkill? What scenarios would I need it, other than A/Bing?

Just A/Bing. You need to decide if you want it or not.

I'm going to use stereo jacks and just bridge the negative and positive.

That doesn't make any sense. Read about balanced signals.