What transformers to run your mix through

[Michael Tibes]

This is an interesting topic for me. In my experience the effect of transformers in the audio path can be subtle to practically inaudible. I'd be interested in some opinions and practical experiences. One experience of myself was back in the day when the forum was building Igor's TG compressor. I did a level-matched version with bypassable transformers for the I/O. I believed to be able to hear a tiny difference, but none of my clients heard any change with the transformers in or out. Those were Lundahls at the input and kinda 'Neve-style' at the output (ungapped for that circuit).

So does anyone have a concept for a stronger, more audible / useful effect?

Michael

 

[AlgoRhythms]

This is an interesting topic for me. In my experience the effect of transformers in the audio path can be subtle to practically inaudible. I'd be interested in some opinions and practical experiences. One experience of myself was back in the day when the forum was building Igor's TG compressor. I did a level-matched version with bypassable transformers for the I/O. I believed to be able to hear a tiny difference, but none of my clients heard any change with the transformers in or out. Those were Lundahls at the input and kinda 'Neve-style' at the output (ungapped for that circuit).

So does anyone have a concept for a stronger, more audible / useful effect?

Michael

Overdrive an un-terminated transformer for more color and then reduce gain after the output by the same amount.

 

[AlgoRhythms]

This is an interesting topic for me. In my experience the effect of transformers in the audio path can be subtle to practically inaudible. I'd be interested in some opinions and practical experiences. One experience of myself was back in the day when the forum was building Igor's TG compressor. I did a level-matched version with bypassable transformers for the I/O. I believed to be able to hear a tiny difference, but none of my clients heard any change with the transformers in or out. Those were Lundahls at the input and kinda 'Neve-style' at the output (ungapped for that circuit).

So does anyone have a concept for a stronger, more audible / useful effect?

Michael

The designers of transformers and the circuits that use them were not looking for color. The designed their products for the lease amount of color that they could. "Color" is a nice name for distortion.

So it's no surprise that many people can't hear a transformer when its used correctly.

 

[ruffrecords]

As noted in previous threads about transformer colour, adding an output load to a transformer makes little if any difference to its colour (but it might lead to increased distortion from the driving amplifier. adding a series resistor to the primary side of the transformer does make a difference to the colour.

Cheers

Ian

 

[AlgoRhythms]

As noted in previous threads about transformer colour, adding an output load to a transformer makes little if any difference to its colour (but it might lead to increased distortion from the driving amplifier. adding a series resistor to the primary side of the transformer does make a difference to the colour.

Cheers

Ian

Interesting. I've found that a properly terminated output on a transformer improves square wave response and lowers distortion.

 

[JohnX]

Terminating the output terminals with a resistor can fix the mismatch impedance and restore a flat frequency response.

But a flat response isn't always what you want if you're using the transformer as a color device.

Thank you so much for clarifying that.
I’m quite certain that my small purple box which contains a pair of Lundahl 1521’s exhibits exactly the behavior that you are describing, and one of my clients absolutely loves it and insists that we use it on all of his mixes. I have repeatedly insisted that it’s too bright, and of all of my color boxes, that one is the only one that exhibits that behavior.

I’m gonna have to add a resistor & switch so I can choose whether it is active or not

 

[JohnX]

I use old transformers for color devices in mastering, usually 600:600 ohm. I add a 600 ohm resistor to the secondary terminals which help flatten frequency response and ringing.

I have had a hard time finding any info on the Lundahl 1521 (possibly discontinued, but there is a model 1521B which clocks in at 1:2.28, I believe), but someone else told me that they are actually 10k:10k.
If I find out that is the case, would you suggest that I use a 10k resistor?

 

[terry setter]

I use old transformers for color devices in mastering, usually 600:600 ohm. I add a 600 ohm resistor to the secondary terminals which help flatten frequency response and ringing.

Hello AlgoRhythms, I've seen more than one way people "added resistance" to help terminate a transformer. For example, I've seen a resistor across the secondary taps (parallel), and I've seen separate resistors on each leg of the secondary (series). Could you tell us exactly how you do it (maybe even a simple diagram)? Sorry for the hassle, and thanks in advance.

 

[AlgoRhythms]

NP. Here's what I do for the termination on a 600:600 transformer.

1. attach a 1/2 watt variable resistor in the range of 200/2k ohms across the output terminals. Need not be exact to these specs, just something close to this that spreads 600 ohms.
2. put a 10k square wave through the transformer while looking at the output on a scope.
3. adjust the variable resistor for the flattest, best square wave response.
4. measure the resistance of the variable resistor that obtained that flat response.
5. substitute a fixed resistor(s) of the same value as the measured.

done.

Hope this helps.

 

[BruceARP]

There is only one choice. It’s the secret of many mastering studios and a few big studios in Nashville. Western Electronic 111c. You have to strap them for 600/600. The Westwrn Electric web site has documentation on these.

 

[Nen'O]

Neve portico 5042 sounds amazing and it’s basically transform box, Phoenix audio nice di is another colour box I use. Both are amazing .
Seven circle audio makes diy colour boxes, never tried it but cool concept .

 

[JohnX]

Phoenix audio nice di is another colour box I use.

You’re the second person that I have seen mention using a direct box as a color box.

Are you just patching a balanced line out mix straight into the direct box and then bouncing the output of the direct box as your mix?

 

[SoundBlaster]

I've been testing a lot of transformers for a gentleman that resells a lot of vintage radio station gear. One thing discovered is that being able to vary the driving impedance from 50ohms to 600ohms can yield a huge difference in bandwidth and distortion spectrum. A lot of transformers (peerless, Western Electric, UTC) all sound pretty similar when driven by 50ohms (regardless of stated primary impedance) and with 100k loads (Zobels use to compensate for resonances.) Increasing the driving impedance tends to result in bass rolloff while also resulting in a different set of distortion products. Top end also tends to get softer. Just adding a 1k variable resistor on the input side is just another tool in the arsenal.. Of course level variation will occur and need correction too.

 

[negaikast]

I've been searching for a transformer/color box for a bit now. Trying to add to the output of my transformer-less older Buzz Audio MA 2.2. Anyone try the 51xAudio Neumann model? Sound samples?

 

[SoundBlaster]

There is only one choice. It’s the secret of many mastering studios and a few big studios in Nashville. Western Electronic 111c. You have to strap them for 600/600. The Westwrn Electric web site has documentation on these.

Gotta love a transformer rated for 35Hz-8kHz with a real bandwidth that is over 150kHz.! I've got some 111A's. 40ohm to 600. Unless pushed, they're pretty much invisible and don't add or subtract anything. Pushed though and they add some bloom. Also consider GenRad 941-A. 600:600 they're rated from 20Hz-200kHz.

 

[JohnX]

I've been searching for a transformer/color box for a bit now. Trying to add to the output of my transformer-less older Buzz Audio MA 2.2. Anyone try the 51xAudio Neumann model? Sound samples?

I have the 51X Neumann color box - I don’t have any sound samples, but I would describe it as one of the cleaner color boxes that I have in my collection. I usually only use that one on mixes as opposed to some of my others which I tend to use on overdubs because they have more coloration.

 

[AlgoRhythms]

My buddy, Barry Rudolph, wrote a nice blog post about using transformers for color. He consulted a few manufacturers for the article and posted some schematics and wiring diagrams. https://www.sonarworks.com/blog/learn/transformers

Great article. Simple and clear. Thanks for posting.

 

[AlgoRhythms]

The WE 111C is a fantastic transformer but it's often too good for coloration! It's VERY hard to make it distort.
The WE 117D is identical except for the case.

Presently I'm using a pair of WE 101A transformers in my secondary monitor chain to tame the brittle high end of a pair of JBL 4311wxa speakers. These transformers are the grandfather of the WE 111c and are over 100 years old.

I have them terminated with a pair of 100 year old WE precision 600 ohm resistors. These are large flat wire wound resistors that are matched to 0.1 ohm. This combo sound fantastic, doing exactly what I need them to do.

I'll post a picture later today.

 

[negaikast]

I have the 51X Neumann color box - I don’t have any sound samples, but I would describe it as one of the cleaner color boxes that I have in my collection. I usually only use that one on mixes as opposed to some of my others which I tend to use on overdubs because they have more coloration.

Thanks. What other options would you recommend? The Buzz preamp is a clean and fast preamp and would love an option to add some "color" to the signal.

 

[alien25]

Hi AlgoRhythms and kags,

thank a lot for these useful informations ! We have a UREI 1178 and the manual says : " If the Model 1178 output is connected to a high impedance circuit,
we recommend shunting the +- and com output terminals with a 620 ohm, 1 / 2 watt resistor. This assures the optimal loading. "
Maybe we will try the recommended bypass switch here as well.

Kind regards, Alien 25