Rossi

trafoless microphone preamp wish list
« Reply #220 on: July 15, 2005, 04:58:13 AM »
Quote from: "analag"
Sometimes bad ideas make the best sounding device, especially if it's a mic pre...


If anyone here needs bad ideas, let me know. I got lots of 'em. :green:
"I am not a number, I'm a free man!"
"Hahahahaaaaaa!!!!!"


trafoless microphone preamp wish list
« Reply #221 on: July 15, 2005, 10:17:08 AM »
Quote from: "Winston O'Boogie"
the use of high supply rails and folded-cascodes are bad ideas

Disagree:
Gain of one stage is determined by power voltage level, because
current trough device is prescribed (by input noise characteristics)

If you want to have great gain in one stage, you can use current
source in collector or resistor with high voltage supply. But that current source degrades input noise resistance to twice.
BTW high voltage with current source not affect noise (stil sqrt(2) higher);
it is only for output voltage swing.

There is limit in high voltage using. It is cascode inner resistance.
But it may be relative high.

               xvlk

trafoless microphone preamp wish list
« Reply #222 on: July 15, 2005, 01:43:04 PM »
...
Jeffrey Toobin: "This is the most embarrassing week ever."

Rudy Giuliani: "Hold my pants..."

soundguy

trafoless microphone preamp wish list
« Reply #223 on: July 15, 2005, 03:22:13 PM »
I dont have much to contribute here besides a question:

when you guys design these things, its obvious that there is consideration paid to the way the preamp will sound, but do you ever think of where the preamp will sit?

From a recording engineer's perspective (not a designers) this is an incredible oversight.  

I dont use many transformerless pre's, but when I do its to put something on top of a mix out in front.  This is a fairly common expectation for a transformerless pre and the primary reason why I will/wont use them.

It would be really cool to design a transformerless preamp that would sit all the way at the rear of a mix just like a neve with a LO1166.  Have it sound however you like, but make it go there.  that would be very cool.  Short of that, pretty much every transformerless pre Ive used over the years all do the same boring predictable thing, they all sit and fight for the same space in the mix.

Ive learned alot from reading this thread.

dave

chips are good with dip...

PRR

trafoless microphone preamp wish list
« Reply #224 on: July 15, 2005, 03:45:48 PM »
Mike placement.

soundguy

trafoless microphone preamp wish list
« Reply #225 on: July 15, 2005, 04:14:37 PM »
Quote from: "PRR"
Mike placement.


different discussion.

If you put a sm57 1" away from a speaker and with all conditions being equal, record a guitar with that mic plugged into a langevin AM16, a neve 1073, an api 312, or virtually any transformerless mic preamp of your choice you will have a track that sits in 4 unique and different places in a mx when you combine it.

The old school logic of "mic placement" as the solution to psuedo location in a mix is valid but its also incredibly simpleton.  I dont want my recordings to sound like motown recordings- if I want something to sit in the back of a mix, I dont necessarily want to hear a bunch of room sound on that track and with the mic placement school of thought thats what you get.  Mic placement as a solution to this approach does little for you if you want your room mics to be forward in the mix while having things like a close mic on a kick drum or a bass guitar amp to sit below and to the rear of everything else.  Mic placement alone will get you nowhere with that challenge and you have to look to the circuit to deliver your space instead.

Mic placement for depth came as a result of guys making records stuck with one kind of preamp to work on.  It was a good solution.  We are playing on a much more 3-D field today as not only do we have mic placement (which really in this context should be looked at as amount of room sound or acoustic space) but we also have circuit implementation as many or some or most people have several or more than one preamp to chose from while tracking and hopefully they are using the circuits strategically to build depth into their mix instead of just plugging into what sounds cool the same way motown cats put the mic far away to give depth to their mix not just because it sounds cool.

The one quality I consistently notice with every transformerless circuit I have used is that its output will sit on top of and in front of material tracked with transformer coupled equipment.  This is useful info to have when chosing limiters for mixing as well.  It would be nice however, to have a transformermerless mic pre that put things as far back in the mix as a neve with a LO1166 does since it would be incredibly useful to have the generally "open" sounding qualities of a transformerless pre sit along side of the "rear" sitting transformer pre's that are popular instead of fighting for the most forward dimension that so many transformerless circuits tend to occupy.

Mic placement is an entirely different discussion from what Im proposing here.  If you take your 12 foot away mic and record it with a 1073, you are still going to have 12 foot away mic sitting at the back of your mix compared to if you record 12 foot away mic with a transformerless circuit using say forssell 992 opamps which will sit right on the top of anyhting that was tracked with a transformer.  From a mix perspective, its important to distinguish recorded acoustic space versus what I call recorded circuit space as transformers will and do put their output in a unique space in a mix and using them in combination with each other is the fine art of building depth to a mix, like a pyramid.  The top of the pyramid for me is always transformerless, it would be cool if someone could design something transformerless that could sit at the bottom naturally.

dave

chips are good with dip...

bcarso

trafoless microphone preamp wish list
« Reply #226 on: July 15, 2005, 05:16:04 PM »
If the phenomenon is due to frequency-dependent phase shifts, then that outght to be something that could be extracted from transformer preamps and emulated in an external module.  It would be important to make sure the source impedance effects were accurately included, including any damping interactions with the mic.

rafafredd

trafoless microphone preamp wish list
« Reply #227 on: July 15, 2005, 05:16:18 PM »
Very very nice post Dave.  :thumb:  I may say that your posts on recording tips have been very enlighetening.

I don´t have all your experience, I´m in fact just starting to explore, but I do agree that diferent preamps with different transformers put the tracks in a diferent "place" in the mix. And I also agree that transformerless recorded material sits on top of transformer coupled recorded material. I also may note that tube preamps that I´ve used, like the Langevin 5116B and the Pultec MB1, both originals and DIY version, so with diferent transformers, all seems to put the material more in the "center", more "compact", like it´s coming from one point only and discreet mic preamps, like NEVE, API, neumann, etc, all seems to put the sound more in the back or "from the sides", "away" coming from a "distant point". And transformerless designs all seems to put the sound in "front", comming from "nowhere", or "all over the place"....

Interesting to note is that I do think the active circuit has more to do with this than the transformers itself. Like, I have a tube preamp with an OEP transformer input, and I also have some discreet preamps with a OEP transformers wired the same way, and the tube preamps puts the tracks in a complete diferent place compared to the discreet ones. I may note however that the output transformers are not the same in the discreet designs and the tube designs... Still, tube pres tends to put the sound in a similar places to eachother (comming from the center, compact) regardless of diferent transformers, and discreet designs also tends to put the sound in a similar places (comming from the back, wide), regardless of using very diferent transformers, and actually "sounding" very different to each other. I mean a tube mic pre may sound very dark, and another tube mic pre may sound very bright, but the track still comes from a similar place "in the center" on both preamps. Am I getting too complex?  :?

Have anyone experienced the same thing with tubes vs discreet experiments?

I´m not very much into FET preamps yet, but I´ll start to DIY some to compare to tubed and BJT pres.

Using all your gear together in an inteligent way to get your final track to sound good, with depth and space, rather than just recording each track with what you think sounds cool in that track alone, is the real chalenge. I always found that recording all sources with the same preamp makes a little more mess in he mixing process, regardless of this being a great preamp. In the recording process, you may find that all sources sounds better in a particularly killer preamp, but you would rather use other preamps that doesn´t aparently sounds as good as the killer one, but that will inprint another "place" in the tracks. It really makes mixing way easier and way interesting. So, I do think having a pallete of mic preamps and knowing "where" they "put" the sound in the mix is a very good thing to do.

I know it´s all very subjective and maybe I may sound even superficial to most of you, but that´s what I´ve found in my recent listening sessions on three studios that I have been working on, and with big colections of diferent and very nice mics. The strange thing is that the "space" perception of diferent preamps doesn´t change too much regardless of very diferent rooms, mics, power amps, and monitors.  Each type of preamps still puts the sound in a particular "place". :shock:

[email protected]

trafoless microphone preamp wish list
« Reply #228 on: July 15, 2005, 07:08:06 PM »
Quote from: "soundguy"
...it would be cool if someone could design something transformerless that could sit at the bottom naturally.
dave


Just wondering if the two qualities "open" and "sit at the bottom" are mutually exclusive?

Learner

trafoless microphone preamp wish list
« Reply #229 on: July 15, 2005, 11:59:15 PM »
Hi Dave,
Just out of curiosity, do you use EQs to adjust the recorded material from using transformerless mic pres? or do you just avoid using transformerless mic pre altogether?
Still into audio gears!


soundguy

trafoless microphone preamp wish list
« Reply #230 on: July 16, 2005, 02:54:25 AM »
Quote from: "[email protected]"
Quote from: "soundguy"
...it would be cool if someone could design something transformerless that could sit at the bottom naturally.
dave


Just wondering if the two qualities "open" and "sit at the bottom" are mutually exclusive?



Ive thought about this all day while doing some wiring.  I still havent formulated a good opinion on this, but the one thing I keep going back to is if you take a transformerless signal and match the EQ curve that comes out mangled from a transformer, if you just roll off the top severly and maybe roll off the bottom, that signal is still not gonna just sit at the bottom of the mix, its gonna sit right on top with the bottom and top EQ'd.  I wish I understood more about all this to be of any critical help in this discussion.  I just have an idea with little to back up its feasability one way or another.  I have a lot of experience using different amps and know what they do to things but unfortunately I dont understand how each specific circuit really works to make a critical decision about WHY things are happening.  I assume the transformers have lots to do with it, perhaps Im wrong but thats the way it seems to me- for instance- Ive totally changed what an 1176 will do simply by substituting different input transformers.  The ouncer that is standard on there is nice and certainly classic, but that limiter is soooo much more with a different input transformer.

I dont think that "sit at the bottom" necessarily means neve.  There are some nice jensens Ive used (lucky for us I dont know any jensen OT model numbers...) which of course sound totally different but definitely have a "send the bottom end to the back" kind of feel to them.  I think it probably takes understand what the transformer is doing and then trying to get the transformerless circuit to emulate that but I would go with my gut and suspect that you could get an open sounding thing to still have some "stuck to the bottom" more than "floating in the air".  

learner, I dont avoid using transformerless stuff at all, just use it for what its good for as I previously described.  I'll EQ any track if it needs EQ but I dont have any transformerless EQ's, so once it passes through an EQ, it changes...

dave

chips are good with dip...

analag

trafoless microphone preamp wish list
« Reply #231 on: July 16, 2005, 04:44:01 AM »
In addition to Soundguy and rafafredd's observation I think the same can be said of electronically balanced and transformer balanced output microphones.


Have anyone built this pre...I have with great success but I did parallel Q1and Q3 and use a discrete opamp instead of the chip. Excellent headroom and transparency. For those who want to check out the article go here http://sound.westhost.com/project66.htm

Analag
Audio engineering suffers from misinformation, disinformation, and downright lying more than most fields of endeavour.

[email protected]

trafoless microphone preamp wish list
« Reply #232 on: July 16, 2005, 10:56:34 AM »
Quote from: "analag"
Have anyone built this pre...Analag


Yes. It is a very common circuit. You will find it in every Behringer mixer and most other low priced mixers and preamps out there.

bcarso

trafoless microphone preamp wish list
« Reply #233 on: July 16, 2005, 02:29:38 PM »
Quote from: "soundguy"
Quote from: "[email protected]"
Quote from: "soundguy"
...it would be cool if someone could design something transformerless that could sit at the bottom naturally.
dave


Just wondering if the two qualities "open" and "sit at the bottom" are mutually exclusive?



Ive thought about this all day while doing some wiring.  I still havent formulated a good opinion on this, but the one thing I keep going back to is if you take a transformerless signal and match the EQ curve that comes out mangled from a transformer, if you just roll off the top severly and maybe roll off the bottom, that signal is still not gonna just sit at the bottom of the mix, its gonna sit right on top with the bottom and top EQ'd.  I wish I understood more about all this to be of any critical help in this discussion.  I just have an idea with little to back up its feasability one way or another.  I have a lot of experience using different amps and know what they do to things but unfortunately I dont understand how each specific circuit really works to make a critical decision about WHY things are happening.  I assume the transformers have lots to do with it, perhaps Im wrong but thats the way it seems to me- for instance- Ive totally changed what an 1176 will do simply by substituting different input transformers.  The ouncer that is standard on there is nice and certainly classic, but that limiter is soooo much more with a different input transformer.

I dont think that "sit at the bottom" necessarily means neve.  There are some nice jensens Ive used (lucky for us I dont know any jensen OT model numbers...) which of course sound totally different but definitely have a "send the bottom end to the back" kind of feel to them.  I think it probably takes understand what the transformer is doing and then trying to get the transformerless circuit to emulate that but I would go with my gut and suspect that you could get an open sounding thing to still have some "stuck to the bottom" more than "floating in the air".  


dave


From what I've been able to gather, the psychoacoustics of spatial phenomena have to do with time delay/relative phase effects as much as magnitude vs. frequency effects, and in some cases the two conflict.

For doing soundfield virtualization out of two speakers you can get pretty close to convincing with just minimum-phase networks, especially if you are playing the material in a fairly dead acoustic.  You have to make some assumptions about the listener's pinnae, so if your ears are unusual the effect can begin to break down.  But it turns out we are fooled when the phase is close enough to what would otherwise be due to a combination of amplitude variation and time delay.  When the late Duane Cooper and Jerry Bauck developed their virtualization scheme they started out, I believe, thinking in mostly the time domain, and migrated to the frequency domain when they found it it worked well enough and, for them at the time, was easier to implement.  Iwahara (iirc) also did a scheme very similar (in fact there could be some patent problems here for C&B) although I don't know how he came to it.

John Norris, when he was with H*rm*n,  formulated a couple of schemes involving very simple processing, including explicit use of time delay.  I'm not sure if the time delay versions were ever implemented.

And then as well, we can achieve the illusion of distance by the judicious use of reverberation.

Most of the virtualization stuff is concerned with location in the horizontal plane, but you can do height virtualization as well.

Anyway, as applied to this subject regarding transformers, I suspect that if you were to do very careful time domain measurements, along with the more obvious frequency domain measurements, of the trafos involved, you could simulate their effects in post-processing.  Again, the interaction of the trafo with the source and the following electronics would have to be part of the characterization. Similar considerations apply to output trafos, presumably.

trafoless microphone preamp wish list
« Reply #234 on: July 16, 2005, 04:42:54 PM »
Quote from: "analag"

[img] use a discrete opamp instead of the chip. Excellent headroom and transparency.

Why? At first : rescale all resistors /10 and capacitors *10 around op amp
and use NE5534AP instead of TL072
And by the way; check that resistive network around op amp. May be input - impedance imbalanced. ?????????????????????

               xvlk

rodabod

trafoless microphone preamp wish list
« Reply #235 on: July 19, 2005, 07:46:52 PM »
Quote from: "bcarso"

From what I've been able to gather, the psychoacoustics of spatial phenomena have to do with time delay/relative phase effects as much as magnitude vs. frequency effects.


This is an interesting topic. I was wondering if the time domain effects of a transformer are simply "smearing" and distorting the signal to the point where the original source sounds more distant.

Psychoacoustics can be fairly complicated. I am assuming that technically, transformerless preamps are more accurate - and this translates to sounding closer in a mix. Could it have anything to do with hearing the original sound (pre reflections) with greater clarity which would in turn make it sound closer? Could a transformer-based preamp alter the initial sound enough to cause the effect of putting a sound to the back of a mix?

Or have I gone completely mad!

I would be interested to hear any more suggestions. I personlly think that time-domain effects sound as if they would have a bigger effect than frequency-domain effects (ie. you can't just eq a transformerless pre to make it sound like a transformer-based one).

Roddy
Quote from: tv
punchy fat bastard chip

[email protected]

trafoless microphone preamp wish list
« Reply #236 on: July 27, 2005, 03:20:46 AM »
Quote from: "[email protected]"
Quote from: "analag"
Have anyone built this pre...Analag

Yes. It is a very common circuit. You will find it in every Behringer mixer and most other low priced mixers and preamps out there.


There is never enough time to say everything during the day.
IMHO, that circuit gives a very decent performance. When not pushed too hard for gain and coupled with a decent condenser mic it makes for a good all around preamp. At the same time it is amazing what little budget it requires. Perhaps, we don't appreciate it because we are used to its sound and we know that it is in low budget products.

Cheers,
Tamas

Rossi

trafoless microphone preamp wish list
« Reply #237 on: July 27, 2005, 06:39:26 AM »
You'll find that kind of circuit even in a lot of mid priced gear. Probably because it's hard to come up with anything significantly better at even 2-3 times the cost. But there are differences, of course, in the choice of components and tweaking of various parameters for optimal performance.
For instance you could use super low Rbb transistors and better opamps such as NE5534/32, MC33078 or something Burr Brownish. I'd like to try the OPA1632 fully differential opamp, but I haven't found a source so far.
"I am not a number, I'm a free man!"
"Hahahahaaaaaa!!!!!"

Samuel Groner

    Zürich, Switzerland
  • Posts: 2935
trafoless microphone preamp wish list
« Reply #238 on: July 27, 2005, 07:10:00 AM »
Do you think a Cohen-style micpre would be too expensive?
Samuel

Rossi

trafoless microphone preamp wish list
« Reply #239 on: July 27, 2005, 08:04:49 AM »
I've never seen the Cohen circuit; that's the one from the AES paper, right? The schemo is not available online, is it?

If it requires real matching (other than taking transistor from the same batch) or slightly exotic components, then larger manufacturers won't be interested. For us DIYers it's mostly component cost, for them other stuff is important as well. Availability of components, cost of manual labor, and of course reliability and sturdiness. I recently talked to a guy who desings preamps & stuff for a German manufacturer. He told me they swiched from a SSM2017 input to a discrete input (probably similar to the Project 66 style circuit) not because of the sound (he liked the SSM chip) but because discrete transistors can take much more abuse than an integrated chip. Which means less repair work under warranty.
"I am not a number, I'm a free man!"
"Hahahahaaaaaa!!!!!"


 

Related Topics

  Subject / Started by Replies Last post
9 Replies
2496 Views
Last post September 03, 2005, 06:26:16 PM
by amorris3
2 Replies
1407 Views
Last post July 16, 2008, 09:17:30 AM
by mikeyB
44 Replies
10757 Views
Last post November 20, 2009, 02:07:41 PM
by danjpiscina
9 Replies
1703 Views
Last post February 02, 2013, 01:03:54 PM
by JohnRoberts