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Electric guitar - ground loop audio isolator that doesn't cost a fortune?
Electric guitar - ground loop audio isolator that doesn't cost a fortune?
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Old 28th March 2018, 06:55 PM   #11
mjbmikeb2 is offline mjbmikeb2  Australia
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Quote:
Originally Posted by leadbelly View Post
Oh for pete's sake, a no-name brand transformer isn't good enough for you, but something as nonlinear as an optoisolator is?
I referenced the IL300 which is designed as a linear opto isolator.
https://www.vishay.com/docs/83708/appn50.pdf
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Old 28th March 2018, 11:09 PM   #12
PRR is offline PRR  United States
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The $7 transformers sold for car-audio are often ample for buffered audio lines (not right from guitar). While they may cost $25 now, it IS worth owning one/several.

That *linear* opto is an old-old idea of mine. Performed poorly with 1980 devices and limited insight, though the potential was excellent. I'm glad to see it has been taken-up by a Big Dog. I doubt they can recover the development cost or keep it in production.
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Old 29th March 2018, 04:12 AM   #13
dotneck335 is offline dotneck335  United States
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Originally Posted by abraxalito View Post
All transformers are going to add distortion, particularly at lower frequencies and higher levels.
Tell that to the owners of Neve mixing consoles, or the millions of listeners who love the sound of songs recorded on those consoles, which are FULL of transformers.
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Old 29th March 2018, 04:23 AM   #14
abraxalito is offline abraxalito  United Kingdom
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I love the sound of transformers also and use them in my own designs, doesn't change what I wrote.
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Old 29th March 2018, 04:32 AM   #15
abraxalito is offline abraxalito  United Kingdom
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Quote:
Originally Posted by mjbmikeb2 View Post
The requirement is "not to sound terrible".
If a supplier says that their low cost transformers are just like the expensive Jensen transformers, but omits specs then you would have to be sceptical.
Line Input | Jensen Transformers
You won't be too likely to find out whether something sounds terrible just from THD figures as sine wave test tones are quite unlike music. I'm also skeptical that they'd be just like Jensen transformers but I do know from experience that very cheap transformers (ones I've wound myself) can sound perfectly decent.

If you want to spend more then get the transformers which have a higher nickel content - it gives better measurements. I have a couple on my desk at present and have made a rudimentary measurement of the LF distortion threshold so I know they're pukka.

2PCS / 10K:10K permalloy audio isolation transformer, balanced and unbalanced conversion audio isolator-in Transformers from Home Improvement on Aliexpress.com | Alibaba Group
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Old 29th March 2018, 04:48 AM   #16
nigelwright7557 is offline nigelwright7557  United Kingdom
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Originally Posted by turk 182 View Post
hear!hear! i can't count how many times an unregulated dc wallwart has been the source of hum in a guitar rig!
I use a wall wart with my mp3 player and the noise is terrible.
I had to earth the zero volt line to get it hum free.
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Old 29th March 2018, 03:16 PM   #17
voltwide is offline voltwide  Ireland
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Considering these linked xformers lack any magnetic field screening they are too expensive imho
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Old 30th March 2018, 01:39 PM   #18
AquaTarkus is offline AquaTarkus  Canada
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Quote:
Originally Posted by mjbmikeb2 View Post
But are they any good? The seller says they sound good, but I don't see any distortion specs or any other technical information other than the frequency response.
This is really silly. We are talking about guitar here, not Hi-fi.
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Old 30th March 2018, 02:58 PM   #19
leadbelly is offline leadbelly  Canada
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Electric guitar - ground loop audio isolator that doesn't cost a fortune?
Sorry, you seem to be getting beat up a little here. It might help to tell us what the big picture is. Are you in need of an isolated DI box to go into a mixer for a live performance? Are you just a hobbyist who likes the idea of building a DI for much cheaper than buying one? Are you trying to fight a ground loop you are experiencing right now?

I don't think that optoisolator is the way to go. It's more of a design project than just building a circuit at this point. You can fight a ground loop by just isolating individual connectors in your chain. Or another option, I think if you buffer those cheap transformers, you will be more than satisfied with performance.
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Old 30th March 2018, 03:07 PM   #20
Antoinel is offline Antoinel  United States
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Electric guitar - ground loop audio isolator that doesn't cost a fortune?
Quote:
Originally Posted by PRR View Post
The $7 transformers sold for car-audio are often ample for buffered audio lines (not right from guitar). While they may cost $25 now, it IS worth owning one/several.

That *linear* opto is an old-old idea of mine. Performed poorly with 1980 devices and limited insight, though the potential was excellent. I'm glad to see it has been taken-up by a Big Dog. I doubt they can recover the development cost or keep it in production.
Hello PRR. Most interesting to learn about your involvement in "opto" linear circuits. Thanks mjbmikeb2 for the Vishay link to its application note50.

The "unipolar" IL300 circuits by Vishay have potential applications in diy Class aP amplifiers [Passlabs Forum]; because they also operate using "unipolar" analog pulses. I'll meditate on and experiment with IL300 devices.

Best
Anton
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