How to Build a Balanced Line Driver for audio testing.

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How to Build a Balanced Stereo Line Driver for audio testing.
Testing an amplifier with a balanced input is easy if you have an audio source that has balanced outputs. If you don't, then testing is still possible if you simply short the 'cold' input to ground.
However, to fully test an amplifier with balanced inputs, you really need to test it with a balanced source, and this is sometimes a problem if you want to use a signal generator, or single-ended music source.
This simple project is meant to rectify that problem on my work-bench. It accepts an RCA input and produces a balanced signal through an XLR socket, with relatively little distortion or degrading of the signal.
Elliot Sound Products has an excellent write-up on this circuit, so have a look for yourself:
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Опубликовано:

11 сен 2024

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Комментарии : 73

@ianide2480 5 лет назад

Another great episode. I'm sure I've said it before (if not I'm saying it now), I truly enjoy your videos. No goofy music in the background, logical/excellent explanations to what you do and why, and a passion for what you do. I've even used some of your ideas for inspiration in my own hobbies (the capacitor tester comes to mind right away). Thank you for sharing what you do. The simplicity of your format makes me think that I could share what I enjoy (though that is a wide spectrum of different things) and perhaps someone else would appreciate what I share; this might take some time though as my full time job keeps me rather busy. Again thanks

@electronicsoldandnew 5 лет назад

Ian Ide : thank you for your kind words. It is pleasure doing these videos, and even more so knowing that they are being enjoyed.

@tonysh0663 4 месяца назад

thanks for your reply…if its possible can you post video about XLR to input signal for amplifier circuit

@GeorgeChristofi 5 лет назад

Very nice little board and design Manuel.

@electronicsoldandnew 5 лет назад

Thanks George.

@PIXscotland 4 года назад

I recently did this as an Electret mic preamp but reversed the OpAmps. I set gain on the first one and inverted last. Works really well. I Like the simple circuit but do prefer the reverse OpAmp stages as gain can be added in as needed which affects both output signals.

@electronicsoldandnew 4 года назад

Yes, that does make it simpler. I didn’t need much gain so this one was my choice for now.

@hsasim 3 года назад

Hello! Came across your channel looking for information on how is it possible for passive direct injection boxes to balance unbalanced audio signal with no external power whatsoever. Whirlwind famous DIR model claims to do so, and I don't have a scope to verify it. I'm sorry for asking this upon my first visit to your channel, but you're the one closest to the answer I look for. Thank you!

@electronicsoldandnew 3 года назад

I have no idea 😊 The only passive way to do this is with transformers, which are fantastic solutions but quite expensive.

@johnspink6957 3 месяца назад

I came across your video while looking for information on unbalanced to balanced conversion. It's a very clear explanation, thank you. I would like to ask if this circuit could be used for moving magnet phono-cartridge levels of about 5mV? Would I need to change the input resistor to 47k to match the moving magnet cartridge? I have a phono pre-amp that has balanced XLR inputs and at the moment I am using a connector which simply shorts the cold side to ground.

@azurplex 3 года назад

Saved me time laying out this circuit myself. Eliot sound link is broken BTW.

@electronicsoldandnew 3 года назад

Pity, he’s a genius.

@slother932 3 года назад

sound-au.com/project51.htm

@slother932 3 года назад

sound-au.com/project87.htm

@alfredneumann4692 5 лет назад

I have worked with eagle, i guess its 15 years or more ago. Did not know, that its there since them. Thanks for this tip.

@electronicsoldandnew 5 лет назад

Alfred Neumann : it’s still around. I got so used to it that I am too lazy to learn Kicad.

@ragtop63 3 года назад

Great video. Would you happen to have a video or resource that shows the opposite end (receiving end) of this?

@electronicsoldandnew 3 года назад

Unfortunately not

@danielsaturnino5715 5 лет назад

Nice. I dont think I need one but its good to have a reference. Just in case. Thanks for sharing

@electronicsoldandnew 5 лет назад

you're welcome.

@maxasken Год назад

Super useful!

@electronicsoldandnew Год назад

👍

@robguyatt9602 День назад

Thanks so much for your video. I am new to differential signals. I how do you think this circuit would go at 300kHz? I am changing my small CNC lathe spindle motor to a faster AC Servo. The driver needs a differential signal each for step and direction input due to the speed. I produce those inputs from a 5V MCU.

@electronicsoldandnew День назад

Probably Ok, but can’t be sure.

@robguyatt9602 День назад

@@electronicsoldandnew Thanks for your reply. I'll give it a go. :)

@misterspot3470 3 года назад

Hi there. Never studied electronics but retirement have pushed me building Bluetooth modules and even an amplifier, with success! First. Looks like you added a resistor marked 1K+ on the PCB design, which does not appear on the schematics. It is located between the input line and pin 3 of the opamp. But on the PCB itself it looks like a 100 ohms value. Could you please confirm. Second. You also mention powering with batteries, which are + and - without ground. If I use a 12 volts DC supply, can I forget about the ground since it only provides + and - wires? Third, what would be the voltage requirement for the 100uf capacitors? Thanks for the good quality video, impeccable diction and absence of distracting music. Cheers.

@electronicsoldandnew 3 года назад

the resistors are correct. Check carefully. You need a split power supply, so the 12V battery won’t work. I normally use 25V caps for this supply range.

@misterspot3470 3 года назад

@@electronicsoldandnew Thanks for your prompt answer. Found a revised video where the 1K resistors were added and the 1000uf caps are rated 50V. If I understand, the audio ground is independent from the power supply ground. Do you have the schematics of your 12 volts DC regulated power supply using LM7812 and 7912? Yours seem to use more diodes and resistors of what I found on other sites.

@ignatiusgalihageng3370 4 года назад

Many thanks.. how about balanced to unbalanced? Would you mind to share the schematic?

@electronicsoldandnew 4 года назад

Ignatius Galih Ageng : here is a great project that explains it all very well. sound-au.com/project51.htm

@matthewramroopsingh4965 Год назад

hi what voltage is the line driver boosting the rac to xlr to?

@tonysh0663 4 месяца назад

can we use this circuit as bidirectional i mean..can we input XLR and get output audio signal for power amp

@electronicsoldandnew 4 месяца назад

@tiptop2457 3 года назад

Love it .

@electronicsoldandnew 3 года назад

👍

@angelminkov7928 4 года назад

Hi, I want to ask if the middle point of the transformer should be grounded because a crack is heard when I turn it on, I want to use it from preamp yamaha cx-630 to crown xti1002

@electronicsoldandnew 4 года назад

Transformer? I don't use one in this design at all.

@johnnsteele2886 3 года назад

Thank you for the video. I'm a bit new to some of this so forgive me if I'm asking a dumb question: I need a balanced line driver for a 12V application as the original product is discontinued, but the rest of my setup requires them and I don't want to pay the $500 asking price for ONE on eBay. Basically without the green ground wire would this still work between 12V and 14.4V DC? The cabling is a 6 pin mini din, but I think I can handle that change. Again, sorry if it's a glaringly naive question. I thought I understood electronics until I started to learn and I thank you again for sharing.

@electronicsoldandnew 3 года назад

Hi. I’m afraid I don’t understand the question. What system is it? Perhaps I would be able to answer you then.

@johnnsteele2886 3 года назад

@@electronicsoldandnew The pertinent components are car stereo active crossover network and class A amplifiers made by Soundstream. All of the inputs are 7 pin mini din balanced. There are no RCA or any other kind of input or output other than that on the crossover and thus the amplifier input is the same. The amplifiers do have RCA inputs, but not the crossover. I have the schematics for the amps. RCA to balanced mini din were manufactured by Soundstream, but are near impossible to find, so I thought I could make my own pair. I'm confused about the power coming in. The green wire makes me think it's not a DC input, but I don't see a rectifier. Is it just the audio signal itself that is powering everything? I'm trying to make sense to explain something that doesn't make sense. Sorry.

@electronicsoldandnew 3 года назад

That is a question I’m afraid I can’t answer. I haven’t played with car systems at all, so any advice I give could have drastic consequences.

@johnnsteele2886 3 года назад

@@electronicsoldandnew I understand. I went and got the schematic for the amplifier and I have a pinout for the line driver itself, so I can go from there. Do you have any suggestions on where to go for help? Again thank you for your time and help.

@electronicsoldandnew 3 года назад

I’d suggest the forums that are specific to that type of application. They can be very helpful.

@1Mrbudgood Год назад

Can this circuit work with phantom power +48v ?

@electronicsoldandnew Год назад

No,

@patrickjohncarlo 2 года назад

Hi, may i ask if this circuit can be used as a general rca to xlr converter, can it be used to drive long xlr cables?

@electronicsoldandnew 2 года назад

Yes, it can.

@patrickjohncarlo 2 года назад

@@electronicsoldandnew cool. I was planning to build this for my home theater pc.

@electronicsoldandnew 2 года назад

👍

@delgadocuenca1990 Год назад

I want to buy one. How I can get one ?

@electronicsoldandnew Год назад

It’s only DIY. I don’t sell them.

@PeterMilanovski 4 года назад

I was just looking at the back of the Gryphon and noticed that it says Zero Negative Feedback. Does it really not have a negative feedback loop?

@electronicsoldandnew 4 года назад

If I’m not mistaken, it has local feedback in the driver stage, but not global.

@PeterMilanovski 4 года назад

@@electronicsoldandnew Hmmmm, still though... I have heard the arguments over negative feedback but I have never seen one! Even if it's a local stage, I have seen circuits with global, I have seen circuits with multiple local, I have seen circuits with multiple local and global negative feedback at the same time... But I have never come across a circuit without or even just a local driver stage. Have you still got the schematic for it... This is a topic that deserves it's own video! Apparently according to some people, that an amplifier without negative feedback is possible and sounds better than an amplifier with negative feedback. While on the other side of the fence, people argue that it's not possible due to stability issues... Do you think that you can at least have a look at the schematic and see if it actually has or hasn't? I have a feeling that they didn't put zero negative feedback on the back for nothing!

@Torpengpogi 4 года назад

hello, an old video, but this is related to what i need. my question is can i used a tube low wattage amplifier with it's output transformer as a balanced source signal? as always output transformer of a tube amp tap has an 8 ohm or 16 ohm and a common usually connected to ground, whatabout if i disconnect the common tap and used it as a negative signal, and the 8-ohm tap as the positive signal, and then chassis ground as the ground? will it drive a balanced input device properly? thanks for any advise that you can provide.

@electronicsoldandnew 4 года назад

I’ve never tried that but it should work. However, you’ll have to use the common (0) as the negative signal, the 8 ohm as ground and the 16 ohm as the positive signal.

@Torpengpogi 4 года назад

@@electronicsoldandnew thanks for the advise, i'll try that and let you know if it works or not. for the moment i am using a passive direct box to interface my sca-35 dynaco tube amp to balanced drive my 2 electronic crossover of my 4-way active stereo system, but the problem is the di box is reducing the signal significantly, bec maybe of transformer used in the di box? thanks.

@electronicsoldandnew 4 года назад

I did some thinking. YOU CAN’T DO IT. The tube amp needs to see an impedance on the primary which is a direct reflection of the impedance it sees in the secondary (the speakers). It expects 8 or 16 ohms to give the high impedance that the tubes need to drive. If you don’t have that speaker on the output, the tubes will see a crazy load that will probably mess with the tubes and the actual output transformer. Not good.

@Aneesh-bd9es 4 года назад

Sir nice work, I wand to make a balance audio,( stereo) for my Rcf sub 705, I am not using a mixer ,I am using RCA to XLR wire for connecting,it is wired as a unbalanced type, in XLR pin 1&3 are connected as ground & pin 2 is Audio,the system is working but some noise, As the circuit mentioned in the video,I think it helps me to solve this problem, Do you have much more efficient circuit for RCA to XLR balance mono?

@electronicsoldandnew 4 года назад

No I don’t. There are endless articles on the net that cover the subject and you may find something that makes a difference to you. Look up “Elliot sound products” where you’ll find various articles that are really great on this subject.

@Aneesh-bd9es 4 года назад

@@electronicsoldandnewis this circuit mentioned in the video help me?

@jestinjose1381 4 года назад

Thank u

@electronicsoldandnew 4 года назад

Pleasure

@hpfctif7tx7t 7 месяцев назад

Is this good for 12v?

@electronicsoldandnew 7 месяцев назад

Should work fine.

@hpfctif7tx7t 7 месяцев назад

Thanks I'll try using this as a balanced headphone amp

@shoukathbava7682 3 года назад

👌👌👍

@electronicsoldandnew 3 года назад

👍

@x3n0n.m 4 года назад

This is maybe very nice, but simply not works after Your schematic. I don't understand why, what's the problem, but nothing comes out from them.

@electronicsoldandnew 4 года назад

X3N0N M : check that you haven’t connected something wrong. The schematic does work, and I’ve built quite a few units from it. Good luck.

@djbandubanait1816 3 года назад

uan balance too balance audi out diagram

@hintoninstruments2369 6 месяцев назад

That isn't a good balanced line driver circuit. I would have been simpler and better to have just used a line isolation transformer with 1:1 winding ratio.

@electronicsoldandnew 6 месяцев назад

Agreed, but compare the price. Good transformers are very expensive. This was presented as an alternative to transformers.