Okay I'm just going to retry to type all of this. ugh.
JMan said:
That said, I don't think there's anything wrong with just using your 18i20. Those are perfectly good preamps - no, not fancy high end studio eye candy, but clean and reliable - and I suspect that any sense of a recording made through them being "less than" (assuming suboptimal mic placement, etc is not the cause) might just be a result of the perception that this is a "cheap" entry-level unit. Personally, I had one in my home studio for a number of years and recorded lots of audio through it in that time, and while I admit that I did occasionally coax the preamps into making a bad sound, most of the time it worked every bit as well as a I needed if I was looking for clean, straightforward gain.
I'm just popping back in here to say this: regarding this exact statement and philosophy.... its a compelling one.
The issue is in reality that transformerless, or "differentially balanced electronic inputs", and or any other electronically, directly-connected configuration is inherently worse, from a scientific performance perspective, as well as a musical one: My primary issue with transformerless preamps is that they have a definite, inescapable tendency to resonate, distort, or otherwise alter the motion of the diaphragm in a correllated, harmonic manner, justonically. So regardless of the music, the input signal, the scale, this mic-to-preamp configuration will ALWAYS be "resonating" in a locked justonic "key" which rears its head as the fifth (V7) of its resonance, complete with b3, M3, and b7 harmonics being the most obvious conflicts. This is very problematic for an auditioned performance, where the singer is constantly trying to adjust to this "microphone scale" which has no correllation to the intended result. How does this happen? Mostly?
Because the high impedance of the input approaches an open circuit as it appears to the microphone diaphragm (whether transformer output mic or direct to capsule...) and causes increased distortion, as well as percieved increased signal level.
(Bear with me here.... I know transformerless preamps claim to have input impedances as low as 2k but in reality it is higher than that....)
Imagine a microphone connected to nothing, and imagine a microphone shorted between pins 2+3. In the open circuit case, flyback, increased voltage, decreased current, and increased diaphragm nodes will exist much like hitting a drum and letting it ring. In the shorted condition, the "electrons" will "race around" and stop the diaphragm from resonating, or moving, much like a sail on a ship, dampened, like putting fabric over a snare drum. So from an electrical engineer's perspective, he will always prefer his microphones to be open circuit; because this generates the most voltage - which is the easiest possible charachteristic to measure with a DMM, and he will feel congratulated in himself for
"increased output." Though the only signal he will ever capture is a sine wave; the easiest possible condition for any audio equipment to reproduce. On the other hand, transformer inputs will resolve a lower voltage than differential electronic inputs:
but will do so with percieved infinite current availability.... this is a huge, notable, non-overlookable electronic phenomenon,
to be able to provide the perception of infinite current. I can't go into more details about this now, but this is very important. People go on about ground loops, etc, one of the great "transformer renaissance men" was Bill Whitlock , of course, the guy who belabored himeself to deliver this information about CMRR and power ground configurations, available in a powerpoint somewhere online. But essentially: even though your signal voltage is inherently lower with a transformer input, the noise is so much lower than a transformerless input, that its crazy. I would like to ammend what he is saying here, and claim that the issue goes beyond ground loops: and is more likely or problematic to have these Power Supply Loops which are present in bare wire connections. Imagine you have two transformerless devices connected together. One device is +/-18.5V and another device is +/-17.82V. Well, there will be a leakage between the two devices, from the output to the input or vice versa. Forget about offset, or whatever. The state of a transformerless device is different internally when nothing is connected to it, versus when something
is connected to it. With nothing connected, it is assumedly static, with maximum offset, and minimum consumption and minimum quiescent current.
When you have two transformer devices connected, OR one transformer device and one transformerless device, the wires never touch one another; as in there is no direct electrical connection between the two devices; and it is quite miraculous it works at all! Why is this such a big deal? Because that means ZERO leakage is possible in between two device's power supplys, outputs, or anything else. The only thing that is potentially (typically) connected in this situation is the grounds; Another Charachteristically Brilliant effect of transformer isolation is that the output transistors are constantly "shorting themselves" through the output transformer primary. A transformerless output which is used to seeing, say, 10-100Kohms, or nearly an open circuit, wheras a transformer output presents about 50-450 ohm load to the output transistors. The two arrangements are different, transformerless being more like Open circuit (with bleeding) and transformer outputs more like a Closed circuit.
When you connect two devices of any kind together, all the transistors in both devices operate at slight or significantly different conditions: In a transformerless-to-transformerless direct connection, the bias of the output transistors
And Every Single Transistor and Preceeding Stage is biased Colder, or "as close to OFF as possible." In the transformed arrangement, the primary of the output transformer looks more like a SHORT, making the output transistors and Every Single Preceeding Driver biased UP, and HOTTER, because each device is as ON as possible.
Another effect of this is more stability, temperature wise, which has real world effects that might be missed in quick lab testing, etc. The more energy being wasted biasing the outputs ON, the more resiliant they are to parasitics and other temperature or external variations. In a transformed device, whether the
secondary of an output transformer is OPEN or SHORTED
has little effect on the operation of the device internally, wheras, on a transformerless circuit, shorting or opening the output has
A Huge Effect on the operation of the device because it is going from Minimum power to Maximum power the second it is shorted. If you short the secondary of an output transformer, it literally doesn't matter because its galvanically buffered from the actual transistors. So when it comes to parasitics and all of this stuff. Having galvanic isolation is
orders of magnitude more stable and resiliant to external effects than direct connections (transformerless). (I probably wrote more on this but I dont have the full previous text)
Transformerless consoles came about in the 90's
soley due to cost. This was pitched to the consumers using the philosophy that removing unessential components from the signal path would attain greater purity of electronic connections. I am sure there were engineers who truly believed transformerless was better. As audio engineers this can often complement our experiences: you connect less boxes together in series, and the signal is more pure. Makes sense. You have 100 transitors in series, it might sound worse or more grainy than having only 5 transistors in series.
In reality when utilizing Transformers this is not the case, because
even though the transformer is an additional component in series with the signal,
it changes the entire operation of the device and devices connected to it in a manner that does not function equivalently to "less is more pure" or "additional component in the signal path. Because as you can see
transformers change operation of the entire device, in a manner that is not "additive". The main advantage for removing transformers from consoles was cost. Add up all of the ins and outs on a console and multiply that number by $50 or $100 additionally, per jack, and you could be looking at $10k to float a console in materials alone. In my opinion, almost every single audio jack Should have a transformer behind it, and transformerless connections are always (or almost always) an inferior connection
on every performance metric... THD, Frequency response, Noise... etc etc etc.. except (potentially) maximum voltage level.
Back to mic inputs. This is the #1 most effective place to improve the quality of a sound system or recording. Transformers do have "a resonance", but it is gentle, malleable, and versatile, being more pronounced on vintage units, but wideband. It's more of a tendency or a range than a rigid scale or harmonic structure. Remember, it is "shorting" out the microphone output, which is dampening anything but the fundamental of the signal on the mic. The mic is responding to Pressure? or Flow? of the air? this is hard to determine.... but it will respond less to pressure and more to flow when transformed. But the idea being that it doesn't favor certain notes, scales, or pitches over others is very essential to getting a good performance,
and we especially want a good sound right? Whereas the diaphragm motion and physical capsule deformations, distortions, and resonant modes of microphone capsules when transformerless connections are used leads to very rigid and locked aberrations in the sound to the point that I wouldn't even bother singing into a transformerless premap except out of necessity. No, its not cork-sniffery; if your microphone
only distorts a little bit but it
always distorts in the exact same pitch regardless of what pitch is put into it.... it just makes it so difficult to perform, and using electronic equipment is already an unnatural way to perform music. Its that big of a difference? yes, especially on voice. Its just SO MUCH EASIER to perform on a transformer preamp that I wouldn't even bother hooking a mic up to something transformerless unless that's all I had or I didn't know any better.
There is a lot more reasons as to why transformers are better than direct, bare wire connections than I listed here, but you get the main points written out fairly well. But. for a preamp? I wouldn't even consider using or buying a transformerless preamp, period. Thats just throwing money away in my opinion. the mic input transformer is more important than the output transformer.
And the mic input transformer is the most important connection in an entire recording studio, period. You can either take what I am saying as fact or not thats your decision. I really wish I didn't lose my awesome message I typed out earlier but I downloaded some RAM history recovery program didn't work too good.
Regarding the original poster: I would buy the ART TransX preamp because it has input and output transformers. or just get one of those ART T8 units which is eight transformers in a box and just dump it into the interface, buffering the preamp inputs with the transformers.
(I've never heard either unit...) Some might wonder "well what about all the extra components that make it transformerless compatible? Isn't it also better to bypass those components, such as coupling capacitors inside the device since he is using transformers?" well. not really. It doesn't make any real difference as to whether you "simply drop transformers in front of a transformerless pre" or actually mod them in properly, because the benefit of transformers has more to do with total device operation and aformentioned stability and bias than anything else.. the #2 most important place for transformers is the LR output of the console. this is also
the most cost effective placement for transformers, because you only need two of them. Actually, you are better off having FOUR, one on each end of the XLR cable, including on the 2 track recieve side. Why?
Because this forms a closed loop of balanced signal transmission, where the "electrons" have no possible extraneous entrance or egress from the locked loop between the cable, the output secondary, and the input primary.
This very simple mechanism is also extremely, extremely important as far as performance goes, and I could go into more detail but it all surrounds the ideas of Peak/RMS windows, VA & W curves, fundamental and reversing voltage expansion. etc etc etc. it sounds super simple. but. is extremely overlooked in 2024. Locked loop transmission. that "ring of wire" in a simple output transformer to input transformer connection. is extremely important in an LR scenario, especially. if you only have one pair of transformers though thats good enough, and is more of an "archival" setup.
also it should be noted that ensuring all inputs and outputs are isolated or at least all the inputs or all the outputs is the way to go, cause you dont want a single extraneous connection going through the devices and messing it all up. ugh. I wish I just didn't lose this text ugh. I'm just saying like. if you have a 12 channel mixing board, and you have 10 transformers, and you have 10 inputs on the console all isolated from the daw. and then you say "oh well i'm out of transformers let me just make the last two connections direct from the Daw" or whatever... well. that kindof defeats the purpose a bit, because now you have two devices interacting which otherwise wouldn't.... its a little complicated but not really. My point is. if ANYONE in the world is going to buy, make , or whatever.. Musical microphone preamps.... they might as well have transformer inputs otherwise you are just throwing away money. I think the ART T8 into the interface is a fine solution, and will radically change the operation of the unit for OP. and its insanely cheap. All of this basically just to say and justify that.
I can't care any more outta time.
edit 99 your only issue with the ART T8 solution is its going to block phantom so you'll need additional phantom supply boxes for your condensers not a big issue IMO
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