Transformer Balanced or Electronically Balanced Preamp?

[Somnium7]

I have to ask because I simply don't know. My experience in electronics design has been limited to microcontroller systems, Navy avionics and analog synthesizers so there is much that mystifies me with Pro Audio equipment.
In this realm I see circuit topologies that I am unfamiliar with and I am trying to understand the merits of the designs I see.

In researching mic preamps I have found that there seems to be two camps beyond the usual Silicon vs Tube and it adds an interesting dynamic to the subject. It is the Transformer vs Electronic balancing issue.

I have read some about the good and bad of both but really can't comment intelligently on the matter. I thought it might be interesting to see which camp has the most followers just as a rough gauge.

So which do you prefer, transformer balanced or electronically balanced?

Please feel free to carjack me if I have the wrong verbage. As I mentioned I am still learning...

 

[timthetortoise]

I'm also interested in this. Seems like something that is often argued, seldom explained.

 

[Richard Monroe]

OK, here's my limited explanation. It's limited because I am an end user, not an engineer. Somebody else will baffle and amaze you with the technical side of it. On the practical side, they say that transformer based circuits "put iron in the sound". It is easy for me to compare,
because I happen to own a Joemeek twinQ, which is why I didn't vote. My answer is- both of the above. The twinQ has a handy-dandy "iron" switch that moves the transformers in and out of the signal chain at the touch of a button. The difference is subtle, but the transformers almost add a slightly metallic edge to the sound, like a tiny little taste of the difference between acoustic and electric guitar. Which I prefer depends on the source and the mic. I also own an Avalon AD2022, which is based on big mucking transformers, and it is a truly excellent preamp. My advice? You could do a lot worse than a twinQ. It has done a lot of good things for me, even with an Avalon in the same rack.-Richie

 

[mattamatta]

If you're interested in just about anything regarding audio electronics, I'd recommend taking a look at the forums at http://www.prodigy-pro.com/forum/index.php . There's a lot of really good info there about all sorts of things, with a good mix of hobby DIY'ers and people with a background more along the lines of engineers. I've even seen the designers of consumer gear comment on questions regarding their particular schematic. As far as I've found, it's the place to be for the more technical side of audio electronics.

 

[mshilarious]

If you're interested in just about anything regarding audio electronics, I'd recommend taking a look at the forums at http://www.prodigy-pro.com/forum/index.php . There's a lot of really good info there about all sorts of things, with a good mix of hobby DIY'ers and people with a background more along the lines of engineers. I've even seen the designers of consumer gear comment on questions regarding their particular schematic. As far as I've found, it's the place to be for the more technical side of audio electronics.

It's also the cult of the transformer

With fairly good reason. Ideally speaking, an input transformer is a clever device. It will provide very high CMRR (common mode rejection ratio). That means it is exceptional at rejecting interference. It may eliminate the need for input capacitors. It can provide a few dB of gain off the bat, which can improve the effective signal to noise ratio of the following active electronics.

The primary disadvantage is cost. Good transformers are expensive, and a good low-noise, high CMRR opamp is a fraction of the price. So to get a transformer that has adequate response and low distortion across the audio band, you will pay a lot more for that preamp.

On the other hand, where transformers have nonlinearities, they are often regarded as euphonic, whereas the distortions of capacitors and active circuits are usually not thought to be desirable.

I have come to believe through experimentation that even moderately priced transformers are often worth the trouble, but even so, that would mean a $10 part rather than the $40+ (sometimes way ++) that the good ones cost. A lot more expensive than a good opamp, which you still need anyway.

Transformers and tubes are much more frequently paired together, since once you commit to a tube circuit, the cost will be high and the box will be big anyway. Transformers have natural uses in a tube circuit, more so than in solid state circuits where the transformer might be viewed as an add-on. It's possible to do a transformerless tube circuit, but that usually means a hybrid tube/solid state design, which are not regarded well by the purist.

 

[dementedchord]

MSH pretty much covered it all... electroniclly balanced circuits tend to have a more open top end to me... or seen conversly cheap transformers tend to roll off the highs...

 

[bubbagump]

MSH pretty much covered it all... electroniclly balanced circuits tend to have a more open top end to me... or seen conversly cheap transformers tend to roll off the highs...

Pretty much. I have a UA 4110 which allows the transformer to be added or removed from the input. No transformer has a bit more high end, but less gain. With transformer has more gain, a bit more mid range. However, if I compare say my cheapo ART $29 DI to my Radial you hear a huge difference in transformers. I pretty much use the transformer always except for certain percussion and stuff with LOTS of high end... otherwise I personally find good transformer designs to sound "smoother" over all.

 

[Somnium7]

So this "Iron Sound" can it also come from the line output transformers?
My console has transformers on all of it's mic inputs and each line out. It would seem that I am getting Iron Sound on anything that passes through the board then.
Looking at the block diagram for the console I can see that the direct outs for each channel are the only outputs that aren't transformer coupled. I think I am going to do some tests to compare the sound from the direct outs and the other outputs with transformers.

I do hear a very noticeable difference on the mic preamps in the console compared to my external preamps. I have a hard time describing the sound though. Compared to my crappy tube preamp (no transformers - has solid state input) it sounds much flatter, colder and the highs are attenuated. I suppose this is the iron effect.

 

[craigmorris74]

Transformer balanced pres such as those made by John Hardy can be as transparent (possibly more) than electronically balanced gear. Sure, API and Neve type transformers add coloration, usually in a way that many find pleasant. But I used crummy electronically balanced stuff for years, and I'm sure those coupling capacitors and cheap IC's colored my sound as well, but not in a positive way.

I wouldn't worry about this as much as the design and build qualilty of the pre.
Craig

 

[pandamonk]

It's also the cult of the transformer

With fairly good reason. Ideally speaking, an input transformer is a clever device. It will provide very high CMRR (common mode rejection ratio). That means it is exceptional at rejecting interference. It may eliminate the need for input capacitors. It can provide a few dB of gain off the bat, which can improve the effective signal to noise ratio of the following active electronics.

The primary disadvantage is cost. Good transformers are expensive, and a good low-noise, high CMRR opamp is a fraction of the price. So to get a transformer that has adequate response and low distortion across the audio band, you will pay a lot more for that preamp.

On the other hand, where transformers have nonlinearities, they are often regarded as euphonic, whereas the distortions of capacitors and active circuits are usually not thought to be desirable.

I have come to believe through experimentation that even moderately priced transformers are often worth the trouble, but even so, that would mean a $10 part rather than the $40+ (sometimes way ++) that the good ones cost. A lot more expensive than a good opamp, which you still need anyway.

Transformers and tubes are much more frequently paired together, since once you commit to a tube circuit, the cost will be high and the box will be big anyway. Transformers have natural uses in a tube circuit, more so than in solid state circuits where the transformer might be viewed as an add-on. It's possible to do a transformerless tube circuit, but that usually means a hybrid tube/solid state design, which are not regarded well by the purist.

Hi, sorry to hijack this thread, it's just one question. There weren't many recent posts by Mshilarious outwith the cave, this is one of the few, so i thought i'd ask here, since i can't contact via pm/email.

Mshilarious(Jon?), do naiant have distrubtion in the UK? If not, do you have any future plans to? I'd love to try out a few of your mics, and would even love to be involved in opening up the UK, and maybe european, market to Naiant. Is there any way that, when i have some money that is, i could buy a bunch of your mics, accessories, etc. in bulk and resell them in the UK? Or is there any other ways of doing this? Would this interest you at all?

Technominds(from London), and myself(Scotland), talked a little while ago about starting up a small-scale acoustics company, mainly aiming at UK ebay to begin with (seeing as there isn't much in the way of acoustics there, other than the shitty foam). Nothing has really came from this yet, but I'm still thinking about it. I would love to involve naiant in this business idea somehow.

Does this interest you in the slightest? If not, just say.

 

[Whoopysnorp]

So what does 'transformer-coupled' mean? My Eureka says it's transformer-coupled. Is that some way to cheat and get a transformer in the design without, I don't know, doing it the proper way?

 

[craigmorris74]

So what does 'transformer-coupled' mean? My Eureka says it's transformer-coupled. Is that some way to cheat and get a transformer in the design without, I don't know, doing it the proper way?

Not really. They're not like tubes in that regard. Unless of course there's really not one in there!

 

[ofajen]

So what does 'transformer-coupled' mean? My Eureka says it's transformer-coupled. Is that some way to cheat and get a transformer in the design without, I don't know, doing it the proper way?

That just means that the unit uses a transformer on the input or output, or both. In each case, the practice of using transformers was actually not begun to color the sound but to ensure the highest possible protection against coupled ground paths and to ensure maximum possible power transfer by properly matching the impedances of inputs and outputs.

Impedance matching is less of a concern now in an age where most circuits are voltage amplifiers and most output impedances are low and input impedances are very high. But the isolation a transformer gives does offer the most bulletproof protection against coupled ground paths.

As you probably know, a transformer uses coupled conducting coils and magnetic induction between the coils to transfer the signal. There is usually no direct electrical connection in the circuit path through the transformer.

What really matters is the actual audio performance of the transformer. High performance transformers are relatively expensive as has been posted already.

Cheers,

Otto

 

[Robert D]

Nice bit of info from Otto. I'll just add that circuit coupling techniques , like transformer coupling, are also called de-coupling, because of what they don't pass..... DC. Both transformers and capacitors pass only AC , and block DC. So putting them between circuits de-couples the circuits, allowing very different circuits with completely different power supplies and DC biasing to pass just the signal to each other. Transformers can do a couple of tricks that capacitors can't do though, like stepping up the signal, by way of turns ratio from primary to secondary, and doing phase splitting or phase inversion. They can be designed in to be very linear, imparting very little sound to a circuit, or they can be designed in to use various properties, such as core saturation, to significantly color the sound.
A gross generalization, but not without some merit, would be that preamps with transformer coupling are likely to fall into the colored camp, and transformerless preamps are likely to fall into the transparent camp. But certainly not always.

 

[Beck]

I couldn't answer the poll since it depends on the device/design. There are good and bad transformer balanced circuits, and good and bad electronically balanced circuits. If we were to take a handful of the best of both it would be a tough call, and like many things would come down to the sound you’re looking for.

 

[Somnium7]

If you're interested in just about anything regarding audio electronics, I'd recommend taking a look at the forums at http://www.prodigy-pro.com/forum/index.php . There's a lot of really good info there about all sorts of things, with a good mix of hobby DIY'ers and people with a background more along the lines of engineers. I've even seen the designers of consumer gear comment on questions regarding their particular schematic. As far as I've found, it's the place to be for the more technical side of audio electronics.

Been trying to get signed up with prodigy-pro forum but never recieved an acceptance email and can't login. Are these guys like Uber-Snobs or do I need to actually buy something to join up?

 

[Robert D]

I couldn't answer the poll since it depends on the device/design. There are good and bad transformer balanced circuits, and good and bad electronically balanced circuits. If we were to take a handful of the best of both it would be a tough call, and like many things would come down to the sound you’re looking for.

Same for me. There needs to be a choice of "some of each".

 

[crazydoc]

Been trying to get signed up with prodigy-pro forum but never recieved an acceptance email and can't login. Are these guys like Uber-Snobs or do I need to actually buy something to join up?

They seem to be having ongoing registration/email-change related problems. Even your dog can join. Contact the admin here webmaster@prodigy-pro.com - he can probably fix it. I changed my email a month or so ago and couldn't log back on - he fixed it in a few hours.

 

[Somnium7]

Yeah I just noticed the mention of these problems in the announcements threads.

Thanks Crazydoc