Transformers adding some "iron" to the sound

[Veri]

So I'm pretty flabbergasted how this is supposed to work, but many audio forums, gearslutz in specific seem to swear by transformers somewhere in the audio signal adding something fun/warm/vibrant/"iron". Transformers of note are Jensen, Cinemag and others.

So I got to try some Jensen Transformers CI-2RR ISO-MAX in my chain. Spent all of yesterday evening listening. It does seem to change the sound subtly, most definitely some kind of distortion, likely harmonic distortion. Good transformers are supposed to be NEAR transparent, so I can't really agree with them supposedly adding something positive to the sound.

Any thoughts from the experts here?

 

[Veri]

This post on gearslutz to me seems to wrap up this topic but I'm curious what others think.

The biggest reason you see input/output transformers in older gear is for balanced I/O. The circuit itself is almost never balanced (i.e., there's only one signal path in the circuit itself), and transformers make it very easy to convert a balanced +/- input into a single-ended signal. The output transformer converts the single-ended signal back to balanced.

The other big advantage of I/O transformers is galvanic isolation, which in some respects protects your circuit from the outside world (and vice-versa). But there are many disadvantages to transformers, most importantly cost -- good audio transformers are very expensive and big and heavy. So most new gear uses electronically-balanced I/O with op amps. You'd be very hard-pressed to tell the difference in sound.

People talk about the "transformer sound", but, generally speaking, good audio transformers are essentially transparent (look at Jensen's offerings). Not-so-good transformers add low-frequency distortion and are bandwidth limited, especially in the low end.

Edit: maybe it is the roll-off people prefer in the transformer output signal?

 

[Krunok]

This post on gearslutz to me seems to wrap up this topic but I'm curious what others think.

The biggest reason you see input/output transformers in older gear is for balanced I/O. The circuit itself is almost never balanced (i.e., there's only one signal path in the circuit itself), and transformers make it very easy to convert a balanced +/- input into a single-ended signal. The output transformer converts the single-ended signal back to balanced.

The other big advantage of I/O transformers is galvanic isolation, which in some respects protects your circuit from the outside world (and vice-versa). But there are many disadvantages to transformers, most importantly cost -- good audio transformers are very expensive and big and heavy. So most new gear uses electronically-balanced I/O with op amps. You'd be very hard-pressed to tell the difference in sound.

People talk about the "transformer sound", but, generally speaking, good audio transformers are essentially transparent (look at Jensen's offerings). Not-so-good transformers add low-frequency distortion and are bandwidth limited, especially in the low end.

Edit: maybe it is the roll-off people prefer in the transformer output signal?

My tube amp (50W in class A) has output transformes and yes, my guess would be they do cause roll-off at HF. In that perspective I don't understand post you quoted which says that output transformers are bandwidth limited in the low end. Low end roll-off may happen only in case magnetic core gets saturated so it cannot store enough energy to transport LF but typcally it's the HF that causes problems with audio output transformers.

 

[Krunok]

In addition to that, I seem to remember to haver ead that output transformers also contribute to the "warm" sound as they have elevated 2nd harmonics which is basically consider pleasant to the ear, often described by subjectivists as "musical" sound.

 

[sergeauckland]

There's considerable difference between low-level impedance matching or 1:1 balancing transformers and output transformers for valve amplifiers.

The former can be, and good ones are, transparent as their distortion is very low throughout the audio band, and with a flat frequency response. My Sowter 1:1 transformers are flat to a needle's width on my meter from 20Hz to 20kHz, and within 1dB from 10Hz to around 100kHz, so no loss of HF. However, they are limited to about +20dBu in level, and need a load of >10k for the input transformers and > 600 ohms for the outputs, and under those conditions, distortion is a little higher below 50Hz albeit still well under 0.1%. Distortion at higher frequencies is tiny, under 0.01%

Output transformers, on the other hand, have to stand a large DC voltage on the primary, which in the case of Push-Pull transformers needs to be well balanced to avoid core saturation due to different anode currents of the two output valves. The transformer has to drive a low impedance secondary, 4,8 or 16 ohms, down to 20Hz with low distortion and equally importantly, low phase shift at LF and HF to maintain stability wityh negative feedback. This is a tall order, and good output transformers are heavy and expensive, and although there are a (very) few valve amplifiers that can be audibly transparent, those are rare indeed. Even those few such amplifiers have measurements that pretty much any transformerless solid state amplifier can match or exceed at a fraction of the cost. The main push away from valves to Solid State in the 1960s was to get rid of the output transformer. Whist the earliest SS amps using germanium transistors had their problems, that was soon solved with the availability of silicon devices.

S.

 

[solderdude]

I have always been amazed about how well transformers can sound.
Back in the days I used an MC cartridge which had a transformer to get it to MM levels and after the power amp used transformers to drive my electrostatic speakers.
The sound was amazing.

As Serge mentioned. Output transformers are pretty limited in FR response compared to line transformers.
Different circumstances.
Depends on winding techniques and used core material and build.

Line transformers can be a great way to get rid of groundloops and to transform balanced connections to unbalanced and vice versa.
Just putting them in line to get some effect seems silly.
Afterall the signal does not 'improve' in fidelity when looking at it from a technical viewpoint.

 

[SIY]

There's considerable difference between low-level impedance matching or 1:1 balancing transformers and output transformers for valve amplifiers.

This.

If you run low level transformers near their saturation, bass distortion rises and they do give an effect which might be desirable in some situations. Run properly (especially regarding source and terminating impedances) and within their limits, good transformers (Jensen, Cinemag, Sowter...) are quite transparent.

And for MC phono step-up use, it is the technology of choice.

 

[Veri]

Line transformers can be a great way to get rid of groundloops and to transform balanced connections to unbalanced and vice versa.
Just putting them in line to get some effect seems silly.
Afterall the signal does not 'improve' in fidelity when looking at it from a technical viewpoint.

Yes definitely agree. But consider in the case it removes some minute hum/ground/mains noise. Once in place it does seem to add some harmonics/distortion, even if slight it does seem to add something. I'm wondering if that something is really desirable contrary to popular forum beliefs. That's all I wanted to test for myself.

But in the case of a persistent ground loop problem it seems like a good enough solution / worth a shot of course.

 

[SIY]

Yes definitely agree. But consider in the case it removes some minute hum/ground/mains noise. Once in place it does seem to add some harmonics/distortion, even if slight it does seem to add something.

I use 1:1 input transformers in my preamp, and if they're adding harmonics/distortion, the AP doesn't seem to be able to detect it. Ditto the 1:10 transformers in my phono stage.

 

[Veri]

I use 1:1 input transformers in my preamp, and if they're adding harmonics/distortion, the AP doesn't seem to be able to detect it. Ditto the 1:10 transformers in my phono stage.

Thanks for confirming that

 

[flipflop]

If you run low level transformers near their saturation, bass distortion rises and they do give an effect which might be desirable in some situations.

What? Desirable distortion? Care to elaborate on this?

 

[SIY]

Yes- we tend to get a little overly focused on reproduction, but it's an effect that is sometimes used in studio work, i.e., music production. Here's how I learned about this: a friend of mine who was making an album in Nashville brought over some of his rough mixes and pointed out exactly where he did this. It caused a noticeable thickening of guitar tone during his solo, which delighted him.

 

[Veri]

After some days of evaluation I'm keeping the Jensen Transformers CI-2RR ISO-MAX in the "chain". It removes a little background hum at (very) loud volumes. My chain is entirely single ended so not that surprising. I think it is very close to transparent so it doesn't really hurt anything. I'd almost be tempted the Jensens "burned in" really well in my system (lol).

Secondly, I'm thinking these transformer boxes might just become "rare" / novelty items so might as well hold on to it They're certainly not going become "cheap" any time soon, the higher quality ones.

 

[andreasmaaan]

After some days of evaluation I'm keeping the Jensen Transformers CI-2RR ISO-MAX in the "chain". It removes a little background hum at (very) loud volumes. My chain is entirely single ended so not that surprising. I think it is very close to transparent so it doesn't really hurt anything. I'd almost be tempted the Jensens "burned in" really well in my system (lol).

Secondly, I'm thinking these transformer boxes might just become "rare" / novelty items so might as well hold on to it They're certainly not going become "cheap" any time soon, the higher quality ones.

Where in your chain are these placed?

 

[Veri]

Where in your chain are these placed?

The CI-2RR is placed with very short cables to the amplifier. It came with a sticker warning to place as close as possible to final piece of equipment.

 

[restorer-john]

They could be useful in many situations. High quality ground loop isolating transformers are not exactly common or cheap. An example where they could be useful is monoblock amplifiers being run from separate power points in a large room to the preamp in an unbalanced system.

They could also prevent a DC coupled setup frying amp/speakers if a preamp or source component went DC.

 

[gvl]

They could also prevent a DC coupled setup frying amp/speakers if a preamp or source component went DC.

Wouldn't it defeat the purpose of DC coupling, i.e. to eliminate caps?

 

[SIY]

There's no real reason to eliminate caps. Unfortunately, the myth persists and there's some equipment out there that has significant offset or DC on start-up.

Of course, in audiophile lore, caps are BAD and iron is GOOD (people seem to love transformer volume controls, inductor loading, and interstage transformers). Except when the iron is in component leads and then it magically becomes bad. It's fine inside of tubes or as transformer cores.

Disclaimer: I used a servo instead of an output cap in my tube preamp. Fashion!

 

[restorer-john]

...I used a servo instead of an output cap in my tube preamp. Fashion!...

The truly fashionable servos are transparent these days...

 

[DonH56]

I used a servo in a tube preamp and an OTL tube power amp. The power amp was actually OK for years, but the opamp in the preamp went bad (was never sure what happened to kill it) and I ended up with a huge DC output from the preamp. Fortunately the power amp was ac-coupled; unfortunately the pop blew a couple of speakers.