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Transformer Color Box
Old 12th June 2018 | Show parent
  #31
Lives for gear
 
Jesse Skeens's Avatar
 
🎧 15 years
Quote:
Originally Posted by MYN ➡️
Super cool idea with the Carnhills. If you get a chance, I'd love to hear a sample of how that sounds on whatever you're going to put it on.
Sure will let you know. Eventually want to put a couple in there all switchable. My main colour piece is a 2500 but sometimes I need a bit more roundness.
Old 12th June 2018
  #32
Lives for gear
 
🎧 15 years
Hi
Adding a resistance to drive it more does not make any sense as a resistor would drive it LESS.
Matt S
Old 12th June 2018 | Show parent
  #33
Lives for gear
 
Jesse Skeens's Avatar
 
🎧 15 years
Quote:
Originally Posted by Matt Syson ➡️
Hi
Adding a resistance to drive it more does not make any sense as a resistor would drive it LESS.
Matt S
Ok thanks must have read that incorrectly, for some reason I thought it would change the impedance but guess it would just change level as usual.



cheers
Old 12th June 2018 | Show parent
  #34
Gear Guru
 
Brent Hahn's Avatar
 
1 Review written
🎧 15 years
Quote:
Originally Posted by Jesse Skeens ➡️
Thanks Matt. So if I put it in a little metal box does that count?
I've made quite a few of these, and haven't found the need for a metal box; I use inexpensive PVC electrical boxes from Home Depot. Just connecting the can to the input/output ground path seems to be all you need. Many transformers already come with a ground pin or lead.
Old 12th June 2018 | Show parent
  #35
Lives for gear
 
🎧 15 years
Adding a resistor before the transformer will alter things, level drop mostly but it can't drive the transformer 'harder'.
Having the transformer in a steel box will help it to not pick up hum from other power transformers.
Having conventional EI transformers too close to each other WILL 'crosstalk' between them.
Matt S
Old 12th June 2018 | Show parent
  #36
Gear Guru
 
Brent Hahn's Avatar
 
1 Review written
🎧 15 years
Quote:
Originally Posted by Matt Syson ➡️
Having the transformer in a steel box will help it to not pick up hum from other power transformers.
With older transformers I can see that in theory, but haven't had it happen in practice. Most good modern transformers come in a mu-metal can, often with a Faraday cage inside of it. Not sure how you're going to improve on that.
Old 12th June 2018 | Show parent
  #37
Lives for gear
 
🎧 15 years
The model Jesse is thinking of does not have a can so will pick up hum and crosstalk if not placed carefully or put in a steel/mumetal can or box.
Matt S
Old 12th June 2018 | Show parent
  #38
Lives for gear
 
Jesse Skeens's Avatar
 
🎧 15 years
Quote:
Originally Posted by Matt Syson ➡️
Adding a resistor before the transformer will alter things, level drop mostly but it can't drive the transformer 'harder'.
Having the transformer in a steel box will help it to not pick up hum from other power transformers.
Having conventional EI transformers too close to each other WILL 'crosstalk' between them.
Matt S
I think it was this post that gave me the idea:

DIY transformer box to add color

Reading again I could just do the obvious and pad the output. The GSSL has make up gain but need to measure how far it can go before clipping its own internals.

At the moment I've already got a pad on the 2500 to drive it harder.


Ha guess I could mount one of the transformers on a sliding mechanism and have variable crosstalk
Old 12th June 2018 | Show parent
  #39
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Jesse Skeens's Avatar
 
🎧 15 years
Quote:
Originally Posted by Matt Syson ➡️
The model Jesse is thinking of does not have a can so will pick up hum and crosstalk if not placed carefully or put in a steel/mumetal can or box.
Matt S
Since the box isn't connected to earth does the metal just act as a sort of antennae to draw away any interference from the audio path?
Old 12th June 2018 | Show parent
  #40
Lives for gear
 
🎧 15 years
The box should be connected to earth (pin 1 of XLR) as it shields high frequencies better when grounded. This capacitive coupled mainly. At LF the rejection of external magnetic fields is as implied a magnetic not capacitive effect.
The predominant LF interference is usually mains hum and harmonics and from other transformers.
You can just leave an unshielded transformer 'lying about' but not if you want an interference free signal.
Brent's transformers have the metal can as part of the transformer assembly so can get away with a non metal box and may also be mounted closer to other transformers.
Matt S
Old 12th June 2018 | Show parent
  #41
Lives for gear
 
Jesse Skeens's Avatar
 
🎧 15 years
Quote:
Originally Posted by Matt Syson ➡️
The box should be connected to earth (pin 1 of XLR) as it shields high frequencies better when grounded. This capacitive coupled mainly. At LF the rejection of external magnetic fields is as implied a magnetic not capacitive effect.
The predominant LF interference is usually mains hum and harmonics and from other transformers.
You can just leave an unshielded transformer 'lying about' but not if you want an interference free signal.
Brent's transformers have the metal can as part of the transformer assembly so can get away with a non metal box and may also be mounted closer to other transformers.
Matt S
Does he sell his own? From what I read on the site it sounded like he was using off the shelf ones.


cheers
Old 12th June 2018 | Show parent
  #42
Gear Guru
 
Brent Hahn's Avatar
 
1 Review written
🎧 15 years
Quote:
Originally Posted by Jesse Skeens ➡️
Does he sell his own? From what I read on the site it sounded like he was using off the shelf ones.
By "he" do you mean me?
Old 12th June 2018 | Show parent
  #43
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Jesse Skeens's Avatar
 
🎧 15 years
Quote:
Originally Posted by Brent Hahn ➡️
By "he" do you mean me?
Ha sorry thought he meant Brent Averill
Old 13th June 2018
  #44
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Jesse Skeens's Avatar
 
🎧 15 years
Been looking into this idea of increasing saturation via other means than increased input on the primary. Checked out a now defunkt site that used to sell colour boxes:

"It does not add a boost, but rather it lowers the threshold where saturation can take place (technically speaking: by adding a finely tuned load to the output of the transformer.) "

And here: Transformer Circuits

", if the load resistance in the secondary is reduced, then the power required will increase, forcing the primary side of the transformer to draw more current to supply the additional need."

That seems like it would result in more saturation? Or are these two talking about different things?
Old 23rd March 2019
  #45
Gear Addict
 
🎧 10 years
Hey everybody.

I have a little question for the experts of iron.

I reverse engineerd a little cordial DI with some modern 10:1 (180k:200) former.
I have an old UTC a20 and allready experienced the subtle but pleasant things it did to a hit level (modular) drum loop (i would call it breathing)

So i have a second utc a20 landing soon and for testing i wired the present one 200:500 after the stock transformer.
Works fine. Louder than 200 of course. Plan is to reverse the second one and put it behind the first for 500:200 with hope to get additional „coloring“ by the step up/down.


Sooooo.... what i dont know and can not clearly test right now is, if that stock transformer with its 180k:200 will work against my aim to drive the UTCs.
Will this kind of tame the signal before it gets to the oldies? And is that at all important for the aim to drive them since we talk Impedance here not Level?

So question would be to pull the stock former out or change positions in the chain for better results?
I also think about a direct in for 3,5mm from the modular to the first UTC to maybe add DC again for the aim of driving them?
Old 11th April 2020 | Show parent
  #46
Lives for gear
 
106 Reviews written
🎧 10 years
Finally getting my DIY transformer box together using a matched pair of 111C, a pair of outputs out of an RCA 76 console and a pair of old Peerless 15356.

This is for myself...

I decided to start out at 1:1 fully balanced through.
It does not have an amplifier, I will use outboard Neve style stuff.

The boards are left over from MTB-1 builds and allow series resistance to primary, a load resistor and pads for as Zobel network at each TX.
They are cascadable (is that even a word?)

I used wire jumpers instead of plotting a series R for tuned flux density.
I left the loads above the normal 600R at 1.5K

That value lets some more of the dynamics through.

Tuning flux density is very cool... It can help push the harmonics that usually give ringing, like around 30K and moves it down to usable range.
This also deals with ringing way better than a Zobel, imo.
Thanks to David Geren down at Cinemag for the flux density theory and tips!

I used the flux density stuff on the MTB-1s.

Anyway, I got the main parts on a 3mm thick plate to mount in the 2u rack case.
I attached a picture of the subassembly.

Be well!
Roger
Attached Thumbnails
Transformer Color Box-internal_sub_plate_assembly_sm.jpg  
Old 2nd April 2021 | Show parent
  #47
Gear Head
 
🎧 5 years
Quote:
Originally Posted by RogerFoote ➡️
Finally getting my DIY transformer box together
If you had a minute to put something together, I would love to A/B that on/off on amix bus, drum bus, drums + bass, that kind of thing.
Old 2nd April 2021 | Show parent
  #48
Lives for gear
 
106 Reviews written
🎧 10 years
Quote:
Originally Posted by pierre_r ➡️
If you had a minute to put something together, I would love to A/B that on/off on amix bus, drum bus, drums + bass, that kind of thing.
Had to sell it...
Medical bills piled high.

It is OK now, but it was really scary for a while.

I have panels for them, but that doesn't help much,
Been on the lookout for more RCA and WE transformers though, to use the panels, so maybe then?

Sorry,
Roger
Old 3rd April 2021 | Show parent
  #49
Gear Head
 
🎧 5 years
I’m very sorry to hear that Roger. I know it’s different but I’ve had to sell a bunch of stuff for health bills myself when my son was born a couple of months early so I kind of understand how that feels. I’m glad to know you’re ok now.
Old 3rd April 2021 | Show parent
  #50
Lives for gear
 
106 Reviews written
🎧 10 years
Quote:
Originally Posted by pierre_r ➡️
I’m very sorry to hear that Roger. I know it’s different but I’ve had to sell a bunch of stuff for health bills myself when my son was born a couple of months early so I kind of understand how that feels. I’m glad to know you’re ok now.
Thanks Pierre!

Here is some feedback from the buyer of that transformer box in the picture:
The Passive transformer system you built for me is unbelievable
Worth it’s weight in gold!


I remember the white knuckle days when my son was born and I was self employed... Scary times there as well!

I ended up taking a govt job as Senior Instrumentation Tech in a water agency in California. That meant having steady income, health and dental insurance.
Made being a young parent much, much easier!

Stay well!
Roger
Old 3 weeks ago | Show parent
  #51
Lives for gear
 
ruffrecords's Avatar
 
🎧 10 years
Quote:
Originally Posted by Matt Syson ➡️
Adding a resistor before the transformer will alter things, level drop mostly but it can't drive the transformer 'harder'.
Matt S
You are quite right. But adding a series resistor will alter the source impedance seen by the transformer which has the effect of increasing the distortion the transformer produces.

Cheers

Ian
Old 3 weeks ago | Show parent
  #52
Lives for gear
 
106 Reviews written
🎧 10 years
Series primary resistance also modifies the flux density, which in turn modifies the resonant frequency.

It changes the audible tone within limits.
David Geren made me aware of that "Flux Density" thing and I have used it to good effect on some transformers. Not all will take kindly to screwing around like that but it can be quite satisfying, finding the sweet spot in primary drive series R for transformers that do benefit.

Changing the secondary load R works in concert with the above method.
For example I found that an 1800 Ohm load was best with primary R modification on some of the transformers.

David said he has seen up to 2.8K secondary loads being the sweet spot on some transformers.

Some transformers have ringing at 30kHz, like some Carnhills, and flux density adjustment pushes it higher.

Roger
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