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Adding Transformers to the Signal
Old 25th April 2010
  #31
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"As far as experimenting goes, I feel sorry for you guys that are at the mercy of whatever you can buy pre-packaged. Kinda like eating everything out of the canned and frozen food sections."

Quote of the day, definitely.

Although I also agree with the suggestion that soldering and drilling can divert a lot of time and energy into the wrong direction. One has to watch one's attention. I have the parts, but my 12AU7/transformer sludge box might never get built.

LP
Old 25th April 2010
  #32
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Quote:
Originally Posted by slenderchap View Post
The choice between gapped and ungapped depends on its application...

If you want to simply take an "existing output signal" (one which you would quite happily send to another piece of equipment) then you would use an ungapped transformer.... like VTB2281
...... [because that output will (hopefully) have no DC offset.... it will be an AC only signal (maybe an odd microvolt of DC offset but nothing significant)..... ]

If you were going to use the transformer as part of the electronics of output circuit itself then there is a possibility that the circuit would be applying a significant amount of DC voltage to the primary winding... in which case you would have to use a gapped transformer ... like VTB2280


Now you could also use the gapped one quite happily on an "existing output signal" which has no DC..... but you will get a better low frequency response from the ungapped one because it will have a much larger inductance.... and the bigger the inductance the lower the low frequency roll off point...


So, assuming that you are not actually designing it into a circuit.... just "slapping it on the back end".... you are best with Ungapped.... VTB2281.

-----------------------------------
Just in case you are interested....

The gap is in the "magnetic circuit".

The magnetic core are made from a stack of thin laminates.... half of which are "E" shaped and half of which are "I" shaped..... the bobbin of wire is fitted on the centre "arm" of the "E" laminates.

The laminates are all stacked in a pile and you have 2 ways of doing it....

.....you can put all the "E's" directly on top of each other and all the "I's" directly on top of each other..... you then have a stack of "E's" and a seperate stack of "I's".... which you can butt together..... but there will be a minute gap between them (the size of the gap is actually controlled by the addition of a thin membrane).... you then clamp them all together with the external clamp and cover it with varnish to stop it falling apart.

.... alternately, you can vary the direction in which you stack the laminates so that they overlap..... an "E" on the left and an "I" on the right.... then the next layer will be an "I" on the left and an "E" on the right..... then the next layer will be an "E" on the left and an "I" on the right.... and so on..... there will be no gap between the laminates as they overlap.
-----------------------------------

Colin
Audio Maintenance Limited
Hey Colin.........thanks for the detailed explanation. Vey helpful
Old 7th August 2013
  #33
three years latter, anyone made a tranny farm?
Old 10th August 2013
  #34
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Bumping
Old 11th August 2013
  #35
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Quote:
Originally Posted by lame pseudonym View Post
"As far as experimenting goes, I feel sorry for you guys that are at the mercy of whatever you can buy pre-packaged. Kinda like eating everything out of the canned and frozen food sections."

Quote of the day, definitely.

Although I also agree with the suggestion that soldering and drilling can divert a lot of time and energy into the wrong direction. One has to watch one's attention. I have the parts, but my 12AU7/transformer sludge box might never get built.

LP
know thread is 5-8 yr bck . . . (nor am I fan of simple putting any ol' xfr in series with input signal) but there was a time when easiest way to find paying entry level 'audio' engineering work was to be able to read a schematic and use a soldering iron w/o permanently injuring yourself (or burning down the studio) . . . gear got flexibly more convenient off-the-shelf and the need to modify everything prior to putting it into play declined . . . whether this is/was a good thing is part of the GS non resolvable debate as to whether all music production after 1977 sucks or not (pretty sure them thar 'the beatles' telefunkens were tailor rolled
Old 11th August 2013
  #36
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Oh, while not tranny farm did add (independently & in succession not same time or series) a UTC mic-pre input xfmr and P87 @ mic output xfmr of differing ratios to an AKG batt powered phantom power box. Not sure how I'd characterize results. Might try to post short samples.

Additionally, if I remember correctly, DIYAudio (.com) has schematics/kit for solo line in xfmer that uses Cinemag xfmr you might look at for a simple not expensive approach to try it out
Old 11th August 2013
  #37
Quote:
Originally Posted by oretez View Post

Additionally, if I remember correctly, DIYAudio (.com) has schematics/kit for solo line in xfmer that uses Cinemag xfmr you might look at for a simple not expensive approach to try it out
thanks! will check it out.

i agree with everything you said.

another thing to remember is it is not just the transformer making the magic, it's the whole circuit.
Old 11th August 2013
  #38
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This is something that I want to try out. I have a crest vx console without transformers on the channels. It has trannies on the subgroups and outputs. Really curious if I add trannies to the channels, there is a place on the pcb for them. They are Jensen JT MB CP CA 8316 Is there anything else I would have to do, or can I just install the transformer and be done? I noticed that the one channel I do have that has a transformer, has different IC's than the ones without...Today, I am pulling out some channels and testing sound differences. If I like what I hear with this one modded channel, then I will be in for a treat, I hope.

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Old 11th August 2013
  #39
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Guitfiddle's Avatar
Um...tried to post a pic and it started a new line with no pic...?
Old 11th August 2013
  #40
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I've made a bunch of these. I use cinemag mix metal and all steal transformers. Mix give a little nice euphoric color, steel gives a very warm color wich is great for kick and bass. I've also used st. Ives and Sowter and some older mci transformers for mor of a iron type sound which is great for guitars in my opinion.
For most 1:1 you want to load the secondary with the same value as the transformer 600 ohm in most cases. This just means a 600 ohm resister going from the positive line to the negative line of the output of the transformer.
Old 11th August 2013
  #41
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This is a very interesting thread. Thanks guys, keep it going!



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Old 11th August 2013
  #42
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Quote:
Originally Posted by Coldsnow View Post
I've made a bunch of these. I use cinemag mix metal and all steal transformers. Mix give a little nice euphoric color, steel gives a very warm color wich is great for kick and bass. I've also used st. Ives and Sowter and some older mci transformers for mor of a iron type sound which is great for guitars in my opinion.
Great info, thanks for the voice of experience. From your description it's a little hard to tell if you are doing all line transformers, mic transformers, or some of each. I assume that these are all 1:1, rather than step-up or step-down, but from what you're saying it sounds like you've gotten some nice color out of them, with clear differences depending on what the tranny core material is. Am I reading you correctly? If you're doing both mic and line level trannies, has one been more successful than the other, or does it just work?
Old 11th August 2013
  #43
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FWIW: my Jensen 1:1 isolation transformers were utterly transparent and useless for adding "color."
Old 11th August 2013
  #44
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Quote:
Originally Posted by Bob Olhsson View Post
FWIW: my Jensen 1:1 isolation transformers were utterly transparent and useless for adding "color."
And that's a good thing!
Old 11th August 2013
  #45
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Yes 1:1 600 ohm are the safest from what I've read and been told. Also, I've used carnhill neve line input trannies wired 2.2k to 2.2 k.
Old 12th August 2013
  #46
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Quote:
Originally Posted by Coldsnow View Post
Yes 1:1 600 ohm are the safest from what I've read and been told. Also, I've used carnhill neve line input trannies wired 2.2k to 2.2 k.
As Bob Ohlsson has pointed out, 1:1 trannies like Jensens (that are designed to be clean) actually don't add any meaningful color to the signal. So clearly not all 1:1's will do this, nor should they, really. Are there other types in particular that you find do provide useful color? Do the Carnhills seem to provide the most juice?
Old 12th August 2013
  #47
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Anyone got a schematic? Ed Anderson is making dead on repos of the UTC-012, Neve LOxxxx, API 2503, ect. From $25 to $50. This sort of thing is what the tonebeast and the slate dragon (his mic pre) are doing. Ive wanted to do a "color box" for ages and cant understnd why its not been done. Having a passive summer is a good way to use different make-up stages. Even a BAxx might be interesting. I'll subscribe and hunt for a schematic.
Old 12th August 2013
  #48
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I believe Ed Anderson uses Altran to make his transformers as do a bunch of others currently. They make a nice sounding transformer. I've used the Altran 2503 replica on some API line amp pres I've made. They sound great.
Old 26th November 2013
  #49
I respect the GS rule about not linking to sites and trying to sell things, but I would like to refer you to some GS reviews of my experiment in solving this issue: how do you find the right transformer to insert in a line level signal flow? I wanted to solve this for myself and hear what would happen with the right transformers. It took some work to find a "tonal" option since so many transformers are made to be very, very clean these days. Since no one was making an affordable option for just a couple channels that I could find (very sorry if there is one somewhere) I researched and prototyped until I though I had found a solution for myself. I settled on some Cinemag transformers and a special circuit that loads the outputs for a bit more saturation, and I use two different transformers for two different tones. I hope my efforts might be of some help. If this post transgresses the rules about barking sales, someone let me know and, bam, it's gone. I love this discussion, however, and just wanted to chime in. Ben.
Old 26th November 2013
  #50
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Ive found a couple of trannies that impart a nice tonal effect on the signal, especially when you use them as a step down and drive them a little. I got a few from Layered Audio, Crimson Audio, and even Edcor. Each one has a different sound, and I have them all wired into a patch bay, so I can choose which one I want in the signal path. I have 15 different trannies in there, wired in different configurations. I think my favorite are some old Bell Systems transformers, 600/600 that I pulled from some old telephone office equipment.
Old 26th November 2013
  #51
cool.
can you post pictures?
are they in a rack or just hanging off the back of your patchbay,
macgyver style?
Old 27th December 2013
  #52
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I managed to find some UTC A-21 transformers I'd like to try on stereo mix buss. Mine do not have a diagram on the side, but pictures of units that do show 500 ohms on the outer pins, although the original spec sheet lists 50, 200/250, 500/600 ohms on input and output.

1) Why the discrepancy of information?

2) Which leads would you attach 5k linear pots to play around with driving/attenuating on either side of the trafo, and why does this change things?
Old 11th September 2018
  #53
Here for the gear
So along the same lines: I would like to take my multi-track stems line level from D/A converter output, through a multi-channel transformer(DI?) in order to convert to mic level - with the goal of hitting the Jensen input transformers of my 8 chan mic pre that has an internal summing bus. I have used the provided Line inputs and the summing mixer sounds fantastic, but the line input is all op amps and does not hit the transformers. It also has an op amp based make-up gain on the 2-bus output. I would like the option of driving individual stereo and mono stems depending on the instruments they contain.

Is there such an 8-channel DI that is made to take TRS line source to XLR mic input?
Old 11th September 2018
  #54
Here is a solution for stereo buss. If anyone has any questions feel free to pm me. TransDrive(R) – Avedis Audio
Old 11th September 2018
  #55
Gear Head
 

Has anyone tried an LVDT? Basically a transformer with a sliding core, so the coupling is variable. Would it saturate more as the core is withdrawn?

LVDT Tutorial | LVDT Basics - What is an LVDT | TE Connectivity

They are made as position sensors; the good animated figures in theme parks used LVDTs for feedback on motions. They are normally fed an audio-frequency sine wave.
Old 11th September 2018
  #56
Gear Addict
Quote:
Originally Posted by Nu-tra View Post
Here is a solution for stereo buss. If anyone has any questions feel free to pm me. TransDrive(R) – Avedis Audio
Been tryin to see or hear one
Old 11th September 2018
  #57
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Quote:
Originally Posted by Zachjj View Post
So along the same lines: I would like to take my multi-track stems line level from D/A converter output, through a multi-channel transformer(DI?) in order to convert to mic level - with the goal of hitting the Jensen input transformers of my 8 chan mic pre that has an internal summing bus. I have used the provided Line inputs and the summing mixer sounds fantastic, but the line input is all op amps and does not hit the transformers. It also has an op amp based make-up gain on the 2-bus output. I would like the option of driving individual stereo and mono stems depending on the instruments they contain.

Is there such an 8-channel DI that is made to take TRS line source to XLR mic input?
I used to do something similar to this using the EBtech Line Level Shifter ( 2-channel, but there is an eight channel version )..It has Jensen trannys and plus, you don't have to drop back to mic level, just line level into your mixer..!
Old 11th September 2018
  #58
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I recently picked up a box with 8 old Otari transformer balanced mic and line pres and one with 4 MCI JH-5 preamps (line only), $300 for each and they came with a free tape recorder. The schematics don't look too complex so I was thinking of trying some simple mods on them at some point. First I have too restore them to status quo but I was wondering if anyone was using tape preamps just for the transformers?
Old 11th September 2018
  #59
Quote:
Originally Posted by paraudio View Post
Been tryin to see or hear one
Are you in Los Angeles? I can demo one for you. They are currently loaded with a limited number of vintage Western electric transformers. We are still waiting on the Jensen's.
Old 1st October 2018
  #60
Gear Addict
Got one the other day love it!
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