What is responsible for soundstage in a preamp design?

[Tubetec]

My apollogies for last nights outburst ,
I stand by the point I made about the endless repetition though ,
probably best if I go back and amend my wording ,

 

[Tubetec]

The example that comes to mind is the granular carbon mic as used in the telephone system , is it passive or active ?

Why is it wrong to express transfomer voltage gain or loss in db ?
Its obvious we cant get more power out than we put in and that bandwidth is sacrificed in the process .

 

[Newmarket]

Designing a product cannot be done by throwing parts on a bench and soldering them in random manner until it is capable of producing whatever it is supposed to produce; a design brief (as succinct as it were) has to be at the start of a design.

Yes - although the concept does invite a detour into the world of Evolutionary Electronics...
note I am not suggesting that eg a mic preamp should be designed in the same way that an FPGA may be configured to be reprogrammable many times in a second.

 

[nielsk]

I may well be overly optimistic, but I hope that all contributing here are of a similar mind that designing electronics is not alchemy, and if you are making a measurement device component specification is extremely important. Of course, in my previous post I am not delving into design, I am simply (and I hope clearly!) describing that the end result is what matters in music production, and it is often the case that a device that has outstanding "specs" does not yield the most successful results.
Following the progress of projects here (which I believe is because of this) there seems to be much more interest in devices that introduce various distortions than ones that are primarily absent from it.

 

[JohnRoberts]

The example that comes to mind is the granular carbon mic as used in the telephone system , is it passive or active ?

passive

Why is it wrong to express transfomer voltage gain or loss in db ?

The Bel is a unit of power. The decibel is 1/10th of a Bel. That said the logarithmic relationship is extremely convenient for dealing with large ratios.

Because of this convenience we routinely express voltage gains of active circuitry using decibels with implied terminations to make them valid power ratios.

Its obvious we cant get more power out than we put in and that bandwidth is sacrificed in the process .

Just for chuckles I did a quick search for audio transformers specified in dB. Here is a bullet point from a Jensen MC step up transformer. (JT44k-DX, MC2-RR).

• Provides 20dB of gain for medium to high output cartridges
• Adds 20dB of low noise, low distortion gain to RIAA preamps

I guess I need to acquiesce to the tsunami of misuse.

JR

 

[JohnRoberts]

I may well be overly optimistic, but I hope that all contributing here are of a similar mind that designing electronics is not alchemy, and if you are making a measurement device component specification is extremely important. Of course, in my previous post I am not delving into design, I am simply (and I hope clearly!) describing that the end result is what matters in music production, and it is often the case that a device that has outstanding "specs" does not yield the most successful results.
Following the progress of projects here (which I believe is because of this) there seems to be much more interest in devices that introduce various distortions and ones that are primarily absent from it.

This is a pretty old topic for me (I've been discussing this since the 1980s).

An analogy I like is use of spice in cooking. Spice can improve the flavor of dishes when used tastefully, but good cooks begin with clean pots and pans... and then add the spice as needed.

JR

 

[Mr. Moscode]

Specs' are not meaningful to the consumer / general public.

Maybe not much anymore. In the early days of Hi Fi, the Analogue Age in the mid 50s on out F response, power, distortion - both THD and IM, wow and flutter, separation were published for everything in the Allied Radio Catalogue. In the digital age the basic minimums are assumed. The only thing someone may get to choose now is the compression quality when dumping a CD into Itunes or downloading music.

But since I was reading the Allied Radio and Lafayette Radio Cats since I was about 9 or 10 they are part of my grounding in audio. Popular Electronics was another source of my education with tubes. My dad had years of them, also CQ and QST.

Then there was a law passed about BSing the public with inflated power ratings in the 60s thus RMS and IHF peak were added to the list. But consumer watchdogs no longer give a poop and you can find budget class D and analogue chip amps that are spec'd to put out way more than their input power. 400 watts RMS out of a car amp that is fused at 10 amps or less.

However specs are still published for hi end audio gear for the aficionado.

God, I'm old. . .

 

[frans]

As much as we are off topic now i find it interesting to see that a certain Lars Lundahl is in the Wiki text for magnetic amplifier.
https://en.wikipedia.org/wiki/File:Lundahl_MagAmp_schematic.png

 

[k brown]

I would think the most useful/clear distinction between 'active' and 'passive' would have nothing to do with whether something can generate a current/signal (carbon/dynamic mics for example), but simply whether a device contains transistors/ICs (or vacuum tubes) or not; 'active devices'.

 

[Gold]

i haven’t read the whole thread but I would look at the noise spectrum of the preamps under question. I could see 1/f noise masking some spacial cues that would be present in a pre with lower 1/f noise. I notice a lot of spacial cues in stereo reproduction are in the low mids.

 

[Mr. Moscode]

As much as we are off topic now i find it interesting to see that a certain Lars Lundahl is in the Wiki text for magnetic amplifier.
https://en.wikipedia.org/wiki/File:Lundahl_MagAmp_schematic.png

It seems similar to the Berning amp but not quite the same.

 

[Newmarket]

i haven’t read the whole thread but I would look at the noise spectrum of the preamps under question. I could see 1/f noise masking some spacial cues that would be present in a pre with lower 1/f noise. I notice a lot of spacial cues in stereo reproduction are in the low mids.

Yes. But the real point was the perception of depth etc from a single channel preamp.

 

[ashdot]

Look for Double Balanced mic preamplifier. Cohen was the inventor

Thank you!

 

[Newmarket]

There's a very good (as in concise) PowerPoint on this from THAT from a previous AES presentation if you Google it.

 

[JohnRoberts]

There's a very good (as in concise) PowerPoint on this from THAT from a previous AES presentation if you Google it.

About "soundstage"? Or about perceived depth from mono sources?

JR

 

[Gold]

Yes. But the real point was the perception of depth etc from a single channel preamp.

I don't understand saying there is no perception of depth in a single channel. That would mean a microphone would sound the same in a dead closet as it would in a concert hall. That isn't the case. Of course you can resolve timing differences that give a sense of space in mono. I thought the OP was asking about perceptible depth differences between two microphone preamps with the same input.

 

[user 37518]

It seems similar to the Berning amp but not quite the same.

Im guessing his inquiry is related to whether it has anything to do with Lundahl transformers

 

[Tubetec]

'Soundstage' is sometimes used by the Hifi community to describe speakers ,
but dont see why it couldnt apply to a stereo image from two mics and preamps equally well .

Mic positioning relative to the sound source can change the amount of reflected ambience , thats an obvious way we can create a sense of depth with even a single channel , a nice pre-amp with harmonically tastefull overload character pulls in the outlier peaks , and lifts the average level ,

Thats quite an interesting suggestion about stereo cues being predominantly in the low/mids ,
My go to drum mic setup incorporates acoustic filters (typically an upside down single seater sofa ) over the spaced stereo pair precisely to reduce the bleed from cymbals , a single overhead captures the high end in mono with hole in the head centre focus ,

Jimmy Page said distance is depth , your ambient pair can be moved nearer of further away to get more or less room in the picture ,
Another thing we used do is use mics set up in stairwells or corridors , a room away from the drums with the doors open , if you can pick a node where the bass drum jumps out , resonates the air , mic that spot ,apply eq as nessesary and you can add great delayed low end grunt to the sound .

If you listen to John Bonhams isolated drum tracks on youtube , its Glynn Johns behind the Helios in the rolling stones mobile . at around 13 minutes in he starts going a bit baloobas

 

[ccaudle]

stereo image from two mics...Mic positioning relative to the sound source...spaced stereo pair...ambient pair can be moved nearer of further away

I think the discussion has strayed quite a bit from the original question.

I have recorded through almost every kind of notable preamp (tube, discrete opamp, neve style, onboard IC opamps). The main difference I have noticed is not the color of the tone (warm vs cold) or (dark vs bright). All of that tone stuff seems to be covered in these modern times with new IC style opamps and even plugin emulations of hardware. The real difference I hear is (2D vs 3D). That is what it seems the newer interfaces and plugins can't replicate. I was wondering what the exact culprit to that issue is?

...the discrete designs has depth with a 3D soundstage. Conversely, the IC opamp is like watching a 2 dimensional black and white cartoon. No depth, just flat.

So what is responsible for the depth and 3D soundstage? Is it the discrete form factor (2520), Or is it the transformers that are usually associated with the 2520 form factor?

The original question was not about ambient pairs or stereo microphones, it was what gives some (single channel) preamps an impression of "3D" while some do not. The unspoken assumption was that the effect can be perceived by other people, that other people would perceive the effect as some difference in the "3D-ness," and that the OP could reliable detect the effect without knowing anything about the preamp (i.e. that it was not a purely psychological effect due to infatuation with the classic designs).

The assumptions about other people perceiving the effect in the same way is on shaky ground, there are substantial differences in how different people perceive spatial effects, so without any concrete limited examples (i.e. specific model numbers of two different preamps, or two recorded files to listen to) it is difficult to have any useful discussion regarding the original question.

 

[Tubetec]

Its not all about the preamp , mic and micing technique play a big role also ,