Unbalanced to Balanced conversion

[Megaken]

Hi, I have an unbalanced preamp and a balanced amp.

Why is there a converter box like this

Amazon.com

if you can just use cables like these?

Amazon.com

I am trying to understand the difference/advantages.

Thx

 

[DVDdoug]

Not all balanced outputs are designed to be connected to unbalanced inputs. Usually the "-" signal is grounded on the unbalanced side and some outputs shouldn't be shorted to ground.

Usually it's OK but it depends on the design of the preamp.

(Going the other way from unbalanced to balanced is OK... It's OK to "short" an input to ground.)

 

[voodooless]

The cables are passive, with a bit of luck they are pseudo-balanced:

Since it's advertised as star-quad, I assume it is a pseudo balanced cable.

The box is active, resulting in a truly balanced output. It also offers level control.

In general, there are pros and cons to both:
- the cable will add no distortion
- the cable will have lower output, so in some cases that may mean you can't drive your amp to full power
- cheap boxes may add distortion and noise
- the fully balanced connection will better cancel certain distortions, but generally not the ones that the box introduces
- the box had level control, if you need that, it may be useful

The specific box has a -90 dB THD and a -88 dB noise floor. That isn't particularly good. So if you can drive the amp well enough with the cable adapter, I'd use that.

 

[Megaken]

The cables are passive, with a bit of luck they are pseudo-balanced:

Since it's advertised as star-quad, I assume it is a pseudo balanced cable.

The box is active, resulting in a truly balanced output. It also offers level control.

In general, there are pros and cons to both:
- the cable will add no distortion
- the cable will have lower output, so in some cases that may mean you can't drive your amp to full power
- cheap boxes may add distortion and noise
- the fully balanced connection will better cancel certain distortions, but generally not the ones that the box introduces
- the box had level control, if you need that, it may be useful

The specific box has a -90 dB THD and a -88 dB noise floor. That isn't particularly good. So if you can drive the amp well enough with the cable adapter, I'd use that.

appreciate the explanation.

I can drive the amp using the cables but was curious about the box.
I also noticed the -90dB THD on the box. My amp has like -125db THD. If I use the box, does that mean the whole system goes to -90?

 

[voodooless]

I can drive the amp using the cables but was curious about the box.
I also noticed the -90dB THD on the box. My amp has like -125db THD. If I use the box, does that mean the whole system goes to -90?

No, your speakers are much worse than -90

But really I’d be much more worried about the SNR spec. That may be quite audible. What amp do you have? Let’s see if it can be driven by 2V RCA?

 

[Megaken]

No, your speakers are much worse than -90

But really I’d be much more worried about the SNR spec. That may be quite audible. What amp do you have? Let’s see if it can be driven by 2V RCA?

VTV AMPLIFIER NCx500 Hypex NCore Stereo with Input Buffer Options | VTV Amplifier

 

[Veri]

Hi, I have an unbalanced preamp and a balanced amp.

Why is there a converter box like this

Amazon.com

if you can just use cables like these?

Amazon.com

If you want the 2V RCA output into a balanced amp input, (pseudo) balanced cables will do the job. If you want real balanced 4V with the added volume (6dB gain) benefit, you will need a 'real' convertor box. DRV134 audio line driver based circuit is popular for this purpose, there's DIY kits around the likes of Ghent audio. It is specced around 0.0005% THD or -105dB, which is a lot better than the -90dB mentioned..

 

[voodooless]

If you want the 2V RCA output into a balanced amp input, (pseudo) balanced cables will do the job. If you want real balanced 4V with the added volume (6dB gain) benefit, you will need a 'real' convertor box. DRV134 audio line driver based circuit is popular for this purpose, there's DIY kits around the likes of Ghent audio. It is specced around 0.0005% THD or -105dB, which is a lot better than the -90dB mentioned..

On the other hand, 25 dB of gain will get you to about 40v, good for 400W into 4R. I’d say, try the cable first.

 

[Veri]

I’d say, try the cable first.

Agreed. Forgot to mention, a cable is what I went with too, works fine in my use. Am using a bit silly pricy Benchmark cables though.
https://benchmarkmedia.com/products/benchmark-rca-to-xlrm-adapter-cable $80 per pair I think they got even pricier!!

 

[jscott]

Hi, I have an unbalanced preamp and a balanced amp.

Why is there a converter box like this

Amazon.com

if you can just use cables like these?

Amazon.com

View attachment 298161

I am trying to understand the difference/advantages.

Thx

Hi. First post. I have an ART EQ 341, which has XLR and 1/4” balanced ins and outs, as well as unbalanced rca’s. I run my turntable and DAC through a Schiit SYS preamp. Would using the Rolls device seen above give me better sound from the unbalanced devices if I used them with a Douk H7 amp with XLR in’s? Right now I have a Fosi BL20C that I’m satisfied with (I have hearing loss in my left ear, so any improvement in sound clarity is appreciated). Thanks in advance. EQ

 

[Sokel]

Driven by the papers @sam_adams posted in this thread I thought I try one of the alternative conversions described there:




It's really simple,I did it with whatever I found in the drawer and tested it.
Note that this method does not add gain as a proper unbal to bal conversion would do.

Thought I test it in something susceptible to noise usually although I don't have a problem with it,so it's a diy cheap el. x-over of the several I have to play with.

Test rig is PC>Multitone analyzer>E-MU 0204 DAC>x-over> E-MU 0204 ADC>Multitone Analyzer)PC.
Settings are visible on the pics,x-over is with filters on (can't be any other way,it's analog) and I choose 40Hz so the rest of the spectrum is visible and harmonics not suppressed by the filter at 240Hz.



First unbalanced to unbalanced



and that's unbalanced to balanced with the above way.




Both for easy comparison.

H2 is 8db down with that method,everything else stays pretty much the same,maybe further improvement to it would be to built properly and not as dirty and clumsy I did for the testing.