Iso-transformer vs Amp with balanced inputs

[PermO]

Not just to be contrary but balanced (differential) interfaces are mainly found on professional gear (with the exception of low Z mic inputs). Lots of consumer and prosumer gear pass acceptable audio with unbalanced interfaces. Digital interfaces can moot this all..

JR

Is there an industry standard defenition of "acceptable audio" ?

I think everybody who records music would like to get the best performance from their gear, people would not be on this forum building all this stuff if they did not care for high quality audio.

My interface (RME) is balanced, so is my Focusrite ADAT extension box, compressor, pre amp, DAC, and my mixer exept for the insert points (I hate that, but I understand the extra cost, bypass switch, extra connections instead of the 10ct drop in switching TRS socket)

Synths are unbalanced, but those connect to either a DI or DI input on a preamp.

So it's mainly these two FX units on my auxes / mixer channels and 8 outputs from a drumachine that needed adapter cables soldered.

 

[PermO]

Yes, it looks like these guys are half-assed between pro and MI. Fortunately 100 ohms is adequate for the LL xfmrs.

Since I have a box full of those, I will apply 8 of them on the FX units, probably try some on the drummachine as well.

 

[abbey road d enfer]

Is there an industry standard defenition of "acceptable audio" ?

It's a moving target.
Many people are happy with a -3dB response of 20Hz-20 kHz.
Rupert Neve fixes a frequency response of 20Hz-20kHz at -0.1dB, which is actually a -3dB response of 3Hz-130kHz. His THD requirements are far less stringent though (coz many transformers in the signal path).
Now some people spend (waste) hours measuring the headphone output of their DAC's and want to see less than -140dB THD (0.00001%).
So, no, there is no standardized definition of acceptable. However the DIN requirements of 20Hz-20kHz and less than 0.1% THD seem to have often resulted in acceptable performance.
One thing to consider is that piling equipment results in increase of THD and narrowing of the overall frequency response.

 

[JohnRoberts]

Is there an industry standard defenition of "acceptable audio" ?

it is generally measured by sales to consumers.

I think everybody who records music would like to get the best performance from their gear, people would not be on this forum building all this stuff if they did not care for high quality audio.

never said they didn't

My interface (RME) is balanced, so is my Focusrite ADAT extension box, compressor, pre amp, DAC, and my mixer exept for the insert points (I hate that, but I understand the extra cost, bypass switch, extra connections instead of the 10ct drop in switching TRS socket)

unbalanced inserts prove my point

Synths are unbalanced, but those connect to either a DI or DI input on a preamp.

yup

So it's mainly these two FX units on my auxes / mixer channels and 8 outputs from a drumachine that needed adapter cables soldered.

do you have an interface problem? if so fix it...

JR

 

[PermO]

I don't think the consumer is a good benchmark, as junk is being pushed onto people by the tons, and the (budget) really good stuff you have to find and discover.

I don't have a problem in the sense of audible humm or noise but I would like to see my overall noise levels go down, that to me, is always a good thing, and a thing to strive for.

I have -80dB noise when I connect my mixer's masterbus to my ADC, so I have a mix going on, hit the spacebar and in Digicheck it will not drop below -80dB.
I'd like to see that lower.


On a DIY unit I have seen noise level (50Hz and 100Hz) go down from -82dB to -110dB by moving one ground connection that caused a loop.
Listening to that unit, it did not have an audible "problem" ... but I am glad I fixed that.

So this is about getting the best possible results from my setup with the stuff I have at hand.

 

[camshash]

After looking into building my own debalancer box I found this guy on redco,

Rolls MB15b | Redco Audio

Id prefer to build my own but this is cheaper than all the parts to make my own, I cant find a schematic for it but do you guys think this would be just as effective?

 

[abbey road d enfer]

After looking into building my own debalancer box I found this guy on redco,

Rolls MB15b | Redco Audio

Id prefer to build my own but this is cheaper than all the parts to make my own, I cant find a schematic for it but do you guys think this would be just as effective?

The schemo of this box is commonly available. It uses the standard 4-resistor diff amp for debal andteh dreaded "Tascam" non-floating arrangement for balancing.
I would not recommand that, except for gutting it for the case and connectors.

 

[PermO]

I made these wooden boxes when I got these FX units a couple of years back as I prefered them sitting at an angle for ergonomic reasons, they also happen to be a perfect hiding place for my transformers, my unbalanced lines are really short now.
First thing I noticed I no longer have to compensate for the level drop, wich allows better gainstaging regarding the noisefloor.
These FX are keepers for me, I love OTO machines, they are my only digital FX now, these made me sell two 19"rack Lexicons and a TC Electronics unit so it feels like a sensible thing to utilize my transformers for these connections.

Still sound amazing.

 

[Newmarket]

View attachment 93264
I made these wooden boxes when I got these FX units a couple of years back as I prefered them sitting at an angle for ergonomic reasons, they also happen to be a perfect hiding place for my transformers, my unbalanced lines are really short now.
First thing I noticed I no longer have to compensate for the level drop, wich allows better gainstaging regarding the noisefloor.
These FX are keepers for me, I love OTO machines, they are my only digital FX now, these made me sell two 19"rack Lexicons and a TC Electronics unit so it feels like a sensible thing to utilize my transformers for these connections.

Still sound amazing.

Can you expand on the level / gain aspect ? What tare the transformer ratios ?

 

[PermO]

The transformers are wired in a 1:1 ratio, I kept the signal flow as in the datasheet serial connection line input, so two transformers for the outputs are "reversed". I used pin 1 from my balanced mixer connections to all the E connections on the transformers.

http://www.lundahl.se/wp-content/uploads/datasheets/1527_7xl.pdf
I think the level drop was due to my adapter cables that did not connect pin 3 from my auxes (floating) to the inputs of my FX units. On the inputs of my mixer channels pin 3 was shorted to ground to accomodate these units.

I notice I get much hotter levels into the units at the same settings, I no longer need to apply any boost to get the FX balanced with the rest of the mix.

Would I (as a hobbyist) spend 560,- euros on 8 transformers to balance my FX connections ? .... no probably not, adapter cables work fine without noise issues, but I like this better, utilising the stuff I've got sitting around anyway.

 

[abbey road d enfer]

The transformers are wired in a 1:1 ratio, I kept the signal flow as in the datasheet serial connection line input, so two transformers for the outputs are "reversed". I used pin 1 from my balanced mixer connections to all the E connections on the transformers.

For best performance, Pin 1 of the mixer should not be directly connected to Pin 1 of the outboard, because of the potential creation of a hum loop. Depending on grounding arrangement of outboard, you may want to connect them via an RC network of 100 ohms and 0.1uF in parallels, or not.

Would I (as a hobbyist) spend 560,- euros on 8 transformers to balance my FX connections ? .... no probably not, adapter cables work fine without noise issues, but I like this better, utilising the stuff I've got sitting around anyway.

In most cases, in a relatively clean environment, you don't need both the input and output to be balanced, because most issues are due to ground loops. It takes only one xfmr to break a ground loop.

For recapitulation, it takes two xfmrs, or a pair of diff driver and receiver to create a balanced connection, which is needed only when the signal must be transported on long distances in a polluted environment.
Alternatively, only one xfmr or floating diff receiver or sender is needed for breaking a ground loop.

 

[PermO]

I connected the "E" connection on the transformers only to the screen from the balanced lines from and to the mixer.
The outboard device is unbalanced and so does not have a (pin 1) dedicated screen, so I chose to do it like this.

I did not have a groundloop, not a noticable one at least... It was more of a "level / matching / integration thing" and I am happy I solved that this way.

Sounds great and got nice hot levels now, I like it, so I am actually doing my Neo Ventilator II also, this one tends to clip really easy, so I do a 2:1 from my aux so I don't have to be so carefull on the channel aux.

Free transformers are cool