How much does a circuit matter????

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bluebird

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I've been doing a lot of listening test with all the mic pres I've been making, and some others too... like a Neve and a mackie and some other stuff.

What I started noticing is the pres that used the same input and output transformers tended to sound REALLY similar even though the circuits are totally different.

I guess what I'm trying to figure out is if a preamp with transistors or opamps is ran within its dynamic range, the sound wave or voltage will pretty much stay in tact and true to itself no matter how the circuit is designed.

I can see driving certain semiconductors beyond their limits will create different distortion characteristics from device to device. So driving a certain preamp hard will bring out the character of the circuit.

I can definitely tell the difference between transformers in a circuit but maybe not so much with the circuit.

Does it really matter what kind of amplifying circuit is used or is it mostly transformers and how hard you push a circuit?

Maybe I just can't hear to well... :?
 
hey bluebird-

you hit on a pivotal point, the place where you are most often going to hear the un-subtle differences between amplifiers is when they begin to distort, my pet monkey can tell the difference between amps then. Other stuff however is more subtle, some amps are softer and others stiffer, and this is all about the amplifier itself. The amount of slew distortion and what it is doing to transients is another place you will hear differences. The speed at which an amp will react to transients is yet another place, although you can lump this in with slew distortion if you really wanted to. Power supply and headroom issues is yet another place where you will hear some differences, although its hard to pinpoint exaclty that thats the deal... I think the quad eight stuff at +/- 28 volt rails is much bigger and open sounding compared to an api 325 at +/- 18 volts. Is it the opamp design, or is it the power rails? I think if you have a snare drum hitting a decently designed amp with +/- 28 volt swing, its going to be easier to get a BIG clean sound out of that than with an opamp of equal efficiency running with a smaller voltage swing. I dont know enough about electronics to defend that position, but thats my speculation.

In practical comparison, the hamptone Jfet pre I find to sound incredibly stiff with really edgy distortion. This amp has ruled in a way on bass because of that like no other amp I have ever used. That magic is DEFINITELY the amplifier and not the transformers.

A UA 1108 on the other hand, is the mushiest fet amp Ive ever heard and if you hit the front end really hard, you can hear the fet overloading and compressing and again, thats totally the amplifier adding the color, not the transformers alone.

Comparing a 283 AV amp to a 340 amp, the 340 can get really "spitty" sounding and can deliver a really cool "help me, Im totally overloaded" sound that Ive never heard a 283 AV do. The 283 is just BIG sounding and Im not refering to the transformers... I used to take those output transformers and hang them off of my ghost, not really the best driver in the universe, but it gave a good enough idea of what those transformers do on their own. Hearing the 283 drive it on stuff with super fast transients, a snare drum for instance, the 283 will gradually slow down the high end before it completely turns it into a square wave. On the class ab neve opamps, they sound way more consistent over a wider operating range, but go into a square wave much more abruptly on a snare and it doesnt have that pleasant slowing, it gets spitty and then distorted, and thats the opamp.

Looking at the JLM 99v, Ive been tracking with it now for a few weeks and like the 283, it has a slowing in the upper mids as it gets pushed, but it doesnt completely clamp down on the high end, there is still a nice amount of air that passes as it gets pushed harder, but gets a nice aggressive edge that isnt spitty at all when pushed to the brink. I honestly dont know what to compare this thing to, its really unique, if you can imagine the speed of a 2520 on top but with the sound of a 283, its hard to describe.

When selecting a pre for tracking, its good to think about the opamp selection in terms of behaviour and then the transformer that its driving in terms of color and control. Yes, the transformer will obviously add a tremendous amount of color to what you put through it, but take the case of the neve a/b opamps and a 2520 or a 1731, the neve is going to get spitty spitty spitty in the high end as it approaches a square wave where the 1731 will remain pretty stiff in the the highs until VERY abruptly clipping, the 2520 behaves kind of the same but is a little more gradual with the clipping on transients.

View most of my comments here in regards to transients, drums, etc. Thats where I always hear the edge of this stuff the MOST, its easy to hear what the baseline of the amplifer is at a usable gain and than judge how the opamp freaks out when you overload it for an instant with a transient, like a snare drum. You might want to push the 283 WAY hard on a snare to get a really cool effect, but with the same micing setup, it might be much cooler to record the same thing giving yourself a lot more headroom if you are using something with a 1731 opamp.

Telefunken V276 amps have a really smooth midrange but the neumann v476 is waaaay less grainy sounding, and Id put that off completely to the difference in the opamps. Those amps both have about the most unusable distortion out there, these arre circuits you want to run with plenty of headroom to make the most of, where something like a neve, on a rock record, can benefit from being run into the red, constantly for effect.

There was talk a while ago about the transformers poor headroom in a spectrasonics 610, and that very well may be the case, my experience with that box is that its clean clean clean clean then completely distorted. Ive always put this off on the transistors in the box, not the transformers, its not gradual saturation at all. From the older guys I know, they all refer to the SS amps as having poor headroom. I would also lump the neotek series two dual transistor mic pre in this category, clean clean clean then unusable squarewave distortion, but nice sounding up to the square wave. Think off it like, nice sounding, then louder, louder, louder, then unusable distortion. The top of the amp sounds just like a louder version of the bottom gain range of the amp. I find these types of amps totally boring and lifeless for rock, if I was recording classical music, however, I would want to use amps like this exclusively. Compare that to say, a 2520 where the bottom of the gain range is cool. Its gets louder, but the sound gets a little more 3-d as the lower mids get furry, more gain goes from furry to growl, more gain, high end starts to compress a little, and THEN you get some nasty distortion, but its not so nasty where it goes KRAKLE KRAKLE and ruins the track, you've got a good way to go in that "ok its really distorting now" area before KRAKLE, where the neotek type amp or the spectrasonics, its all nice and then pretty much instantly KRAKLE.

I guess one of the ways I decide upon an amp is the usable window of distortion that it can handle when you look at practicality. I cant make a 1272 or an 1108 sound bad. amps like that are like the level sponge, they can just absorb level and still churn out a pleasant sound, even if its completely distorted, its still pleasant and maybe not what you wanted, but still usable if you have to use it. Other amps sound good and get to that krakle point eventually, and others get to the krakle point pretty quickly. Some amps will give you a different frequency response (mids seem to peak more) as they overload where other amps are really linear until they go krakle. If you are doing location recording where unpredictability is a big part of the job, one type of amp might benefit you more than another, and of course other amps might be better to use if you are in a studio and can hit a talkback button and ask for another take because of operator error, many reasons to chose a pre...

A good place to see how an opamp can freak out is with a distressor. Mess around with that and you can hear the inner and outer limits of what an amplifier can handle and how it will distort when pushed over the edge. That box is transformerless, so all the distortion which you'll hear is all about the design of the amplifier blocks.

To bring this to a more maddening level, if you are thinking about tracking in terms of saturation, you can view amplifier selection when mixing in terms of presence. An amp that can pass a whole bunch more high end is often going to put stuff towards the front of a mix. An amp that has a lot of distortion in the high end can bring a bass forward in your mix. An amp that slows down the high end will seemingly bring stuff deeper into your mix, and then theres the playing with midrange distortion to move stuff around in between. Yes of course transformers will play into those decisions in all the same way, but by patching your tape out into this or that amp can very drastically change the place where your source is sitting in your mix, depending on the transient content of the source, the pre its patched to and the headroom that pre has.

Oh, and then theres tubes. anytime you need to turn something into a mess of undefined mush, run it through a tube. When I need an undefined midrange that is just a round blob, most old tube amps will get me there. Im sure a tube head will step forward right now and extoll the virtues of a new tube design to counter weigh what Im saying here, but Im talking about an LA2A or a Pultec EQ or an Altec 436, those get patched when I need the round orange blob. If you record on a computer, this can be the most awesome thing.

And then there's shitty chips. The 741 may have a demonic hate by folks out there, but I swear, a stock LA4 is about the most awesome tool for taking an edge off a vocal, not because of the wonderful smoothing power of the optical compressor, but because of the horrid slew distortion in the amplifier which will take a sharp transient and smear it all over the place. I have a hybrid QE eq which has chips in the EQ, so its really smeary sounding BUT, it uses an AM-10 on the output, so its got this MASSIVE punch to it. Good for those instances where you need a smeary punch like a click clacky low tuned bass where the player was sloppy, the slow smeary junk of the chips in the EQ can do a lot to soften the fret and finger noise without having to surgically excise those freq's with a notch EQ. Some chips however, can be fast as all hell, I think that true systems precision 8 used a burr brown chip and that mic pre was without question the fastest mic pre I have ever heard in my life, awesome awesome awesome sounding box that would IMMEDIATELY put whatever you put through it right on top of everything in your mix. Something like that would just absolutely RULE for recording flutes with ribbon mics, the tracks would be completely 3-D sounding, that box was transformerless.

hows that for a comparison? Short answer- the circuit matters a TON.

Im sure someone else can speak to other opamps, but those are the ones I use the most at my place. Add an am16 to this list which is just the wierdest amp Ive ever loved. wierd behaving little amplifier.

dave
 
Much of the sound of the Distressor is accomplished by imbalancing the DIST TRIM pot around the FET attenuator. The other part of the sound is the attack/release circuit. It's very 1176-ish, but with a few tweaks for the opto mode. The op-amps appear to be pretty clean.

With regards to transformer vs amp, I built three preamps, each using the same Sowter transformers - the Neve-style preamp ones, and they all had the same character but subtle variations within that character. I built the standard Neve 1290 clone, and it has a sound. I built one using LM833 op-amps but with the same active loading on the input transformer and the same gain staging, and the same sort of class A ouput - except the BC184C transistor stages were replaced with op-amps. The sound was almost the same, maybe a bit clearer - but very similar. I'd say 80% was the 1290 sound and 20% was different. The third preamp used the same transformers but used some high-speed low-noise linear tech preamps, and a linear tech output buffer to drive the transformer. The 'sound' was still there but it was different too - clearer transients, and lower noise. This was a substantial difference in topology and it showed. I'd say the sound had about a 50% similarity to the 1290 clone, and 50% of an Earthworks transparent mic pre sort of sound.
 
> pres that used the same input and output transformers tended to sound REALLY similar even though the circuits are totally different. I guess what I'm trying to figure out is if a preamp with transistors or opamps is ran within its dynamic range...

If an amplifier has "enough" transistors, used well, then its flaws are likely to be much less obvious than the flaws in average old-pro grade transformers. So yes: a modern chip opamp or a discrete with more than 2 or 3 transistors will likely sound "about the same" when used between the same transformers.

You can devise a 1 transistor mike amp and get barely enough gain, no feedback; it will have enough distortion to be obvious even though the transformer-sound in the signal path. 2 transistors can be better, but usually not so clean that it sounds like another amp with "enough" transistors to do the job for-sure-well.

The classic Neve and Langevin preamps, made in days when transistors were expensive, tended to use 4 stages for mike preamps working into 600 ohms. (Langevin also made boards where the mike amps worked into 10K; here 3 stages were enough.)

5534 is still a nice amp with about 10 active transistors in 4 layers of current gain. (It has a lot more transistors because on a chip, a transistor is cheaper than a resistor, also to handle a wide range of supply voltages.)

You can put 20 transistors together badly and get a sonic-signature that will cut through most other system flaws.

Tubes usually can't be put together so badly that they stink, in part because their lower gain per bottle acts as internal negative feedback and they never distort as bad as a bare-naked transistor. And mostly a tube is a tube: they tend to sound similar. But they are often used with little to no added feedback, so small circuit changes can be heard. They are never perfect, but rarely so imperfect to sound awful, so there are many ways to go.

> anytime you need to turn something into a mess of undefined mush, run it through a tube

Complicated (high-feedback) tube circuits will bite as bad as a transistor, big haze of complex and apparently unrelated overtones. But a simple tube circuit makes simple distortion, with overtones that have clear relationships to the original sound. So it is mush, but mush that is "loosely defined" by the original. When complex amps get outside their range of perfection, their overtones quickly lose any "defined by original" quality and become a smear of hash, trash, spit, grit.
 
Well I guess I got my questions answered..... :green:


This all makes feel a little bummed. what this means to me is one of two things. One, after years of recording and playing in bands my critical listening skills suck... Or my monitoring chain needs serious improvement.

I'm monitoring through NS-10m's, an old phase linear stereo power amp, and a mackie board with my sound card going through the least cluttered signal path of the mackie. My practice space is far from sound friendly. Just a desk in a square room up against a half carpeted drywall wall.

All the preamps I've tested are:

same input and output transformers...basicly:

Langevin (just a line amp) (+48V)
Philbrick/PRR weird O pre (+/- 15V)
Hamptone (one gain block) (+24V)
G9 (tube)

different input output transformers:

Neve 1272 (+24V)
Millenia 990 with lundhal input TX (+/-24V)

and finnally a mackie channel pre....

So the only ones I can tell a difference with are the Neve and 990. which basicly just seem to have a bit more high end or maybe PUNCH.


Even the mackie sounds very similar to all the rest!!!!!


Hey I'm still learning, and Dave thanks for such an educated point of view. I really trust your judgement (you too PRR). I aspire to someday know, feel and hear the things people on this forum know, feel, and HEAR!!!!! :?
 
bluebird-

if you are monitoring through the mackie, I dont care what anyone says, you are never gonna hear any kind of minor differences between this amp or that amp once the mackie gets done smearing everything. I had one, I know. I also had a ghost, which is a good enough sounding console and even THAT (which blows the doors of a mackie) does a fine job of masking tons and tons of info. You are only gonna hear the fastest thing in the chain, and the mackie, unfortunately, is the slowest. If you plug your pre's directly into your power amp, you'll definitely hear more of a difference between things. The last thing I upgraded was my console, and when I got a discrete console, after working on the gear I had for years, I honestly almost fell over when I got to hear what my amp collection ACTUALLY sounded like once I had a console that had a summing section that was fast enough to accurately represent what I was feeding it.

Its not your ears, its your console.

dave
 
[quote author="bluebird"]I'm monitoring through NS-10m's, an old phase linear stereo power amp, and a mackie board with my sound card...[/quote]

Oh my God, it's the monitoring chain from Hell!

:green:
 
[quote author="NewYorkDave"]Oh my God, it's the monitoring chain from Hell![/quote]
:green:
but definitely ... classic
not suggesting you should get rid of it but I think it might be prudent to think about adding a second monitoring option.

Some of the subtleties between the above preamps might be hard to catch inside that monitoring combination.
 
Oh my God, it's the monitoring chain from Hell!

I never thought it would happen to ME..... :shock:


Alright then that makes me feel a little better.

I think its time for an upgrade. I HATE NS-10's everything I mix through them ends up sounding like the music is playing under water on normal stereos. When I try to mix brighter the high end actually kind of hurts to listen to.

I just blew a tweeter on on of them. so maybe its time.
 
I don't think you should just dump the NS10s.

It was only last night I had a phone call with a friend where he sang the praises of the NS10 after re-discovering them. He has loaned a large ZPE amp off me and was testing it.

Lets not start another NS10 thread.

As part of your monitoring system, the NS10 does have a place. A second option is necessary. It could also be worth looking at the Phase Linear as it is old and could be in need of some TLC. Which model and when was it last looked at closely ?
 
Yep, monitor chain needs improvement, but you can hear huge differences between pres by just running straight out of your sound card into headphones. Of course this isn't a good way to mix, but it's very effective for critical listening.

I usually set up a mic in front of the source, record a sample with one pre, switch the cable over and record the same sample with the other pre, switch back and repeat. After 4 or 5 takes of each, I play them back and compare. With this many takes I can always hear the "average sound" of each pre even though there may be small discrepancies between the takes. I try different sources, too. Sometimes there's a subtle difference in male vocal and a huge difference in female vocal or vice-versa. The same goes for using an acoustic guitar and other instruments.

What kind of sound card do you have?
 
Yea.... when I think about it, having been in nice studios I've hear NS-10's sound really good. I thought it might have been the room.

I don't know what model Phase Linear I have but it looks pretty substancial. Its like a 4 space rack with a really heavy duty power transformer.

it looks just like this one:

phase.jpg


I've never upgraded the caps or anything.

I have a newer crown 50 watts per side power amp. its a one space rack size. nothing special. would this be better to use?
 
> an old phase linear stereo power amp

Hmmmm.... that was what I had in mind when I said "You can put 20 transistors together badly and get a sonic-signature that will cut through most other system flaws."

I remember when the first Phase Linears came out. They blew-away other amplifiers. Finally we could run AR-3s at high level without trimming transients. They were not mushy like most tube amps and quite a few older tranny amps. And they had sparkling detail we never heard before.

Well, a lot of that "detail" was small crossover distortion, marginal slew rate, and hard-clipping adding glitches. (Yes, we soon clipped 200 watt amps even though 35 watts had always been "enough" before.) The later PLs were better, and overall not a bad amp, but for serious monitoring of other amps I'd like you to try something else. Almost any recent home hi-fi will be equal or better and at least different, so will give you a different window into the sounds of amps. (And of course a home hi-fi is one of the major target playback systems for most producers.)

> I just blew a tweeter on on of them. so maybe its time.

That suggests gross abuse considering your small room. Unless it was a one-time freak-out in the Phase Linear (they did that), the other drivers may not be working like-new either. Again, get about-any good home hi-fi speaker, at least as a cross-check to know what the NS10s are and are not telling you. And keep a pair of "bad" home hi-fi speakers around: sometimes they highlight or reveal things that you don't notice on well-balanced speakers. (Anyway half your target audience is using "bad" speakers, and you don't want to sound worse than necessary.)

I like Mackie. Audio-fool Gold it isn't; I think it is pretty flawless. But in the process it may be dimming details. Try a day of just your preamp assortment wired straight into a decent home hi-fi amp and speakers, see what you hear.

> after years of recording and playing in bands my critical listening skills suck...

After years of carefully listening to both live sounds and amplifiers, I still say if two amps sound different then one of them is sick and should be fixed. (If not actually broken, maybe just loved-for-what-it-is.) I don't think there is a significant difference between polyprop caps and super-virgin olive-oil caps, not to my ears. (I can hear a single X7R cap in the audio chain.)

However I remember the early Phase Linears, used a Crown D-75 for years as my office rig, and just salvaged some Meridian 205s. The 205s are "smoother" than the first Phase Linears, and somewhat smoother and more detailed than the D-75. This is in very hasty testing: I need to clean some mud out of the 205s before I use them much. (They appear to have been in a flooded basement.) By my ears: the early PL needs to be fixed, for crossover and slew (not really possible within the original design, which was very good for the time). The Crown.... well, it isn't a Meridian, but isn't broke, and can be flogged mercilessly without any risk of blow-up; that may not be true of the Meridians.

EDIT Ah. I see you posted a pic of your PL. This is an original-flavor PL with the deluxe faceplate they added a few years later. It may sound better than my first-generation PL; I still would consign it to light Disco use and get something else for critical monitoring.

I'm not sure which Crown you have... there were SO many that "50W/ch" doesn't say anything. The early ones like my D-75 are inoffensive workhorses, and if you know them well very trustworthy, but would not be my first choice for critical listening. I know Crown improved every aspect of their amps over the many decades, and a recent one may be as clear as any other amp you can afford to touch (and perhaps less colored than some overpriced amps).
 
A D-75 only claims 37 watts per channel in 8 ohms (it makes more, but not a heap more). One snob called mine a "headphone amp", and indeed it is handy for driving many headphones at once through a lossy splitter. I mostly found 35-40 watts ample for my needs, but keep an eye on the overload light. If it is blinking, you are clipping peaks in the Crown and not getting perfection.

I also don't think a D-75 is a fabulously clear amp, but if it is handy try it. It is PL-400 vintage and has some of the same flaws, but I think Crown hides it better. (That may mean it hides subtle details in the many preamps you are comparing.)
 
I just went for a three weeks trip. When got back, I realized that forgot to turn off my probably 20 years old D75. Still works...
BTW, anybody has schematics?
 
Any transformers in there?!

Which Mackie? They have quite a price range , you know.

1202-cheap solution box
1604-barely passable for mixdown, should never be used for tracking
8-buss- really not bad, nicer sounding pre's , thats for sure..

Go through a headphone amp if you want to hear the difference between mic pre's, including the iron.

Some tubes are just as quiet as transistors or your best fet's.
And they can be made to sound just as good as your best transistor amp.
Yes, the Pultec and LA2 do not contain state of the art tube circuits.

Just comes down to what you want to create.
Sometimes two of the same pre's will sound different, due to minor differences in components, other times, you can change things a ton and the amp still sounds the same. What do they call that, the Monte Carlo simulation where the circuit simulator tries to analyze what will happen when certain components drift 10 percent...

Transformers certainly make a diffrence on something like the Langevin AM-16, which has probably the weirdest transformer/transistor symbiosis there is.

Anytime you have dc on the core, different transformers will probably make a difference. Also, certain transformers will sound different with different mics, so when comparing preamps, shuffle a few mics back and forth for a full comparrison.
 

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