Transformer Circuit to measure amp, xover, and other +40dBu devices

[NathanR]

Can someone help me (I'll even pay) design a circuit to measure amps and crossovers and other stuff like that.

I had a LinearX VI-Box that worked great, until I burned it up because of inverting the polarity accidentally.

What I want is to be able to probe anywhere in a circuit and not care about polarity or DC bias or input impedance or whatever.
I want isolation, bandwidth, high input level (50dBu max), low distortion.

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I've been reading all the schematics on Jensen-Transformers.com. Good stuff.

https://www.jensen-transformers.com/wp-content/uploads/2014/08/DIN-PB-1.pdf

I think an H or O pad to bring 50dBu signal down by 20/30/40dBu to +20dBu input into transformer will work well.

https://gcarter.us/Articles/attenuators.pdf

Ideally, I want:
8chs total
2- money channels voltage
2- money channels current
2- secondary channels voltage only
2-input power/mains (voltage + current) measurement

Ultimately, I just want to start testing and plotting. I'm tired of trying to learn/teach myself.

For now, just some basic isolation to measure xover would be plenty good IMO.

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Context:
Measure this: Danley DNA20K4 (4ch 20kw amplifier)
With this: RME ADI 2/4 Pro SE
LoadBank: hot-water-heater-element bucket(s) 4ch 2/4/8ohm with voltage divider bucket [I'll get photos later]

 

[Doodski]

Can someone help me (I'll even pay) design a circuit to measure amps and crossovers and other stuff like that.

I had a LinearX VI-Box that worked great, until I burned it up because of inverting the polarity accidentally.

What I want is to be able to probe anywhere in a circuit and not care about polarity or DC bias or input impedance or whatever.
I want isolation, bandwidth, high input level (50dBu max), low distortion.

---

I've been reading all the schematics on Jensen-Transformers.com. Good stuff.

https://www.jensen-transformers.com/wp-content/uploads/2014/08/DIN-PB-1.pdf

I think an H or O pad to bring 50dBu signal down by 20/30/40dBu to +20dBu input into transformer will work well.

https://gcarter.us/Articles/attenuators.pdf

Ultimately, I just want to start testing and plotting. I'm tired of trying to learn/teach myself.

A oscilloscope can be probing most everywhere as can a trendy Huntron Tracker and differential/balanced input oscilloscope will do even better than the others I posted.

 

[NathanR]

A oscilloscope can be probing most everywhere as can a trendy Huntron Tracker and differential/balanced input oscilloscope will do even better than the others I posted.

That's true, but it's super annoying to make pretty plots that I can do with APxFlex... or Multitone or Rew or Smaart, or ... any other full-bandwidth testing software.

 

[Doodski]

That's true, but it's super annoying to make pretty plots that I can do with APxFlex... or Multitone or Rew or Smaart, or ... any other full-bandwidth testing software.

Well... Sometimes probing with metering gear can cause a ground fault and fry your metering gear. So I would be very careful with using a one-off design.

 

[NathanR]

Well... Sometimes probing with metering gear can cause a ground fault and fry your metering gear. So I would be very careful with using a one-off design.

Yepp
Found that out the hard way :/

That's why I want transformer isolation from now on. Haven't a clue of what circuit is correct.

 

[Doodski]

Yepp
Found that out the hard way :/

That's why I want transformer isolation from now on. Haven't a clue of what circuit is correct.

IC... smart man.

 

[NathanR]

Looking into USB Isolation.

There's only a few chips. Pretty easy to tell which are better than others.

Avoid all the gimmics (reclocking, hahah whatever)

Pkane says good things about this one:
DSD TECH SH-G01L USB Isolator Supports USB 2.0 480Mbps High Speed Isolation

 

[Speedskater]

Quick and dirty.
Use an output transformer from a vacuum tube power amp.
Hook it up backwards.

 

[Cbdb2]

Are you trying to test an amp under load? Than you would need a large transformer, I dont think Jensen makes those. Why not use a resistive divider? Cheap, accurate, wont saturate, won't add distortion, easily adjustable.

 

[Cbdb2]

Looking into USB Isolation.

There's only a few chips. Pretty easy to tell which are better than others.

Avoid all the gimmics (reclocking, hahah whatever)

Pkane says good things about this one:
DSD TECH SH-G01L USB Isolator Supports USB 2.0 480Mbps High Speed Isolation

Don't think thats what you need. Your ADC will still see too high a voltage at its analog in.

 

[NathanR]

Are you trying to test an amp under load? Than you would need a large transformer, I dont think Jensen makes those. Why not use a resistive divider? Cheap, accurate, wont saturate, won't add distortion, easily adjustable.

Yep, already have -40dB network, I want isolation.

Don't think thats what you need. Your ADC will still see too high a voltage at its analog in.

USB ISO is to provide extra protection from damage.


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I think I'm asking my question incorrectly. Or people aren't reading the post thoroughly. (Likely the former).

Basically, I want to build a better version of this the SP-2SX Speaker to Line-Level DI/Converter.
I have half a mind to just buy that, but I bet we can do better.
Especially with a -40dB pad (need to figure out correct topology). I just need to go +20dBU to +20dBU line-level isolation.

Really what I'm after is just someone to tell me whichever schematic/design they'd choose from Jensen's website.

Schematics | Jensen Transformers

The following schematics are free of charge and available for your sole use by registering as a user. We ask that you do not distribute these without prior consent from Jensen Transformers Inc. We thank you for your support and understanding. Mic Preamp | Line Input | Line output | General...

www.jensen-transformers.com

 

[nagster]

I had a LinearX VI-Box that worked great, until I burned it up because of inverting the polarity accidentally.

If you want to save money.

Linearx VI-Box

Looking for Linearx VI-Box. Schematics, shots of internal parts/hardware, layouts are welcome to build a clone.

www.diyaudio.com

If you want to save effort and time.

IMP Box

www.physical-lab.com

ISO Box

www.physical-lab.com

 

[NathanR]

If you want to save money.

Linearx VI-Box

Looking for Linearx VI-Box. Schematics, shots of internal parts/hardware, layouts are welcome to build a clone.

www.diyaudio.com

If you want to save effort and time.

IMP Box

www.physical-lab.com

ISO Box

www.physical-lab.com

Hahaha, those pics are of mine.
I just repaired mine, was pretty easy all things considered.

The Physical Lab boxes are great. Just super expensive.

Hoping to build equivalent units for less than 1/4th

2022 pricing

• Imp-Box 290,00€
• ISO-Box 360,00€
• Filter-Box 495,00€

 

[Speedskater]

Are you trying to test an amp under load? Than you would need a large transformer, I dont think Jensen makes those. Why not use a resistive divider? Cheap, accurate, wont saturate, won't add distortion, easily adjustable.

No, the load is connected directly to the amp output in the normal way. The output transformer is just the first part of a voltage probe.