Isolation transformer schematics/projects

[Brymus]

I found this whilst searching for a 1:1 transformer for my volume/panner build I am planning.

Jensen is supposed to have excellent small transformers for the price,they even provide several schematics for using them in audio projects for guitar,mic,and line level use.
http://www.jensen-transformers.com/apps_sc.htm

The hummer looks cool for testing for ground loops,but lots of other good projects on that page too.
They also sell inductors for about 5$ to prevent oscillation in op amp outputs.

AES does carry a 1:1 mains isolation transformer from Hammond
http://www.tubesandmore.com/products/P-T171B
I would like one for several uses, and gear I would like to protect,breaking ground loops.


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https://ia700809.us.archive.org/10/items/JamNite2014-03-27.JamNite2014-03-27/07HeyHey.mp3

[blackieNYC]

The Hammond looks to be a 120 v isolation transformer.  I think you get that. For a 10k:10k transformer for audio isolation there is the Edcor, which is cheaper than its Jensen equivalent and is popular.  Maybe someone can tell you the differences if any.   I bought a pair, havent used them yet, but they have a full freq response.  Claims 20hz. There are a lot of 10k:10k transformers that roll off at 300 hz or higher. Fine for noise stuff?  Low end response seems to require some iron.  Bigger. https://www.edcorusa.com/wsm10k-10k

[PRR]

What do you want, Audio or Power? Maybe you know the difference but onlookers may be confused.

What do you need a *200VA* power isolator for?? While there are uses, they would be odd. In many cases you should just build the gear so it does not need isolation. The usual "need" for a 120V isolator is the old-old death-trap guitar amps. These were all under 15VA so need a lump that costs $30, not $97.

[wavley]

What do you want, Audio or Power? Maybe you know the difference but onlookers may be confused.

What do you need a *200VA* power isolator for?? While there are uses, they would be odd. In many cases you should just build the gear so it does not need isolation. The usual "need" for a 120V isolator is the old-old death-trap guitar amps. These were all under 15VA so need a lump that costs $30, not $97.

Dirty power in a studio?

The Hammond looks to be a 120 v isolation transformer.  I think you get that. For a 10k:10k transformer for audio isolation there is the Edcor, which is cheaper than its Jensen equivalent and is popular.  Maybe someone can tell you the differences if any.   I bought a pair, havent used them yet, but they have a full freq response.  Claims 20hz. There are a lot of 10k:10k transformers that roll off at 300 hz or higher. Fine for noise stuff?  Low end response seems to require some iron.  Bigger. https://www.edcorusa.com/wsm10k-10k

I have to second Edcor, I've been happy with everything I've gotten from them from iso transformers to break ground loops, output iron for mic pres, and the custom ones they made us for work to fake three phase power for our cryogenic refrigerators.

[Brymus]

What do you want, Audio or Power? Maybe you know the difference but onlookers may be confused.

What do you need a *200VA* power isolator for?? While there are uses, they would be odd. In many cases you should just build the gear so it does not need isolation. The usual "need" for a 120V isolator is the old-old death-trap guitar amps. These were all under 15VA so need a lump that costs $30, not $97.

I guess I should have been more specific.
Including the power iso tranny in the same thread as the small signal iso trannies might be confusing to some,I found it interesting so I linked it.

I was mainly looking at the audio small signal transformers,I have a cheap one from mouser,but the Jensens are "supposed" to be better.
I haven't tried them so IDK.

Mainly I was linking the projects they supply,a lot of neat DI boxes and such,good info on using the 1:1 transforms for guitar and mic applications,the schematics should work with other brands too,there just may be some differences in the frequency response using other brands of transformers.

My thoughts on the 200VA power transformer was it would be good for the crappy wiring in my garage when using my scope or PC,would break ground loops when using two power amps (with one of the pair plugged into the iso transformer)
Also would be good (I think) for gigs where the power from the wall outlet is less than optimum,I was thinking it would protect against compressor spikes,but maybe it would just mirror the spike through.
But also I was thinking it would protect my gear from,whatever gear (amps,PA's) the other bands bring.

So Paul would it be best to use a surge/spike protector with a built in filter and plug the ISO transformer into that?
Or the reverse order of that, ISO first?

I have a couple that really do filter the AC,my flat screen has a much more stable and clearer picture when using these type vs the cheap surge protector kinds.

That way the AC into my gear would be filtered and surge protected and isolated.

And @ Wavely ,that's good to know about the Edcors.For my stereo panner/volume pedal I am going to need four small 1:1 tranformers
two for the inputs and two for the outputs.I was thinking of using the pedal to blend different FX as well.Like blending a fuzz with a diode clipper for example.I just haven't worked out the details and switching to make the one wah shell do all I want yet,then there's seeing if it will all fit,but that's something for a different thread.

[PRR]

> my flat screen has a much more stable and clearer picture when using these type vs the cheap surge protector kinds.

TV?? on Cable? If you have Hum Bars, the surge-strips do nothing. The power line and the TV cable "grounds" are at different voltages. They fight, and crap-up the TV signal.

The most direct fix is a cable-TV transformer in the cable where it enters the house or first splitter.

I had bad bars and discovered that basic hygene (bonding at the meter/cable pole dirt-rods) made it 99% better.

If your garage wiring is crappy, IMHO you should fix it (contract it out). Band-aids aren't fixes and may multiply problems.

[wavley]

Four Triad or the other 10k:10k folks use around here (I can't remember, but it's the one R.G. specs in is Hum Free ABY) might fit in a wah shell.  Four of the Edcors won't, the Edcor is physically four times the size of the Triad, they might fit if you used a Morley wah shell, kinda like this guy http://www.effectsdatabase.com/model/morley/telray/sel

I used a smaller version of the one BlackieNYC linked to when I made my tweaked version of R.G.'s Hum Free https://www.edcorusa.com/pc10k-10k Not a bad transformer for $6.37.  I play in open C a lot and I also play Bass VI/baritone guitar so the Triads just weren't giving me the low end I needed.

[Brymus]

@ PRR,no it wasn't bad bars,and it wasn't with cable,I don't watch regular TV,only discs.Blu Ray mainly and DVD.The filter/surge protector I used just made the picture sharper and removed the spurious video noise,if that makes sense.I bought it on sale a few years back for about 100$ IIRC.
But yes around here grounding is bad simply because of the earth,it's mainly sand and rock,I believe where I live was once part of the Colorado River before the dams were built back in the depression era.
I have a well so maybe grounding to the well head would work,my review of the permit showed my well is approx 200' deep,the casing should be metal of some type,IDK why I didn't think of this before.( I should probably research if that's safe first)

@ Wavely thank you for that link ,I am using a Boss FW shell so it is somewhat bigger than a crybaby shell.
The PDF for the trans you linked to showed dimensions of approx 30mm x 41mm x 16mm tall I should be able to fit four of them but it will be tight( I think I can mount them sideways).For the extra 2$ a piece I think it's worth it for the extra bandwidth of the Edcors but I will probably try one channel with the cheap Mouser ones first to see if I notice any sound degradation.I salvaged some OTA's and LM324's yesterday hopefully they still work,I removed most the solder with solder sucker then used a heat gun to get them loose without wrecking the pins.So now I have all the ICs I need,next is a layout and then etch a PCB.

Also @ Wavely,could I see a schematic of your version? did you use a 100K pot instead of the 10K RG used,or are you talking about an A/B/Y box?
I want to make a stereo volume/panner I have stereo FX that sound great through my 2 X DIY 18 Marshall watt amps,So I want to make it foot switchable between volume and pan mode,rather than make it able to bypass.

[wavley]

Also @ Wavely,could I see a schematic of your version? did you use a 100K pot instead of the 10K RG used,or are you talking about an A/B/Y box?

I actually isolated a stereo signal of my pedalboard from my amps, so if you take R.G.'s Hum Free ABY, delete the input buffer and switching so it has two inputs and two outputs. R.G. didn't spec any pots for this, but I think you're talking about the 10k feedback resistor on the op amps, yes I did replace those with trimmers to set my levels going to amps, no I don't remember what value I used but 100k is most likely what I had laying around.  On top of that, I added a phase reverse switch to the primaries of one of the transformers because the reverb channel of my vibrolux is out of phase with every other amp I own.  Also, I used two single op amps, OPA something or another I think.

Really, I just stripped his schem down to what I needed and made it a little more tweakable to deal with using different amps.