R/E/P Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1] 2  All   Go Down

Author Topic: Fet Mic Vs. Tube Mic: Do They Sound Different?  (Read 22351 times)

rphilbeck

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 604
Fet Mic Vs. Tube Mic: Do They Sound Different?
« on: October 24, 2007, 02:47:20 PM »

Saw a thread over at GS which got me to thinking:  

All things being equal, what differences might a person expect to hear between a fet based mic and the same mic with a tube?  
Logged

Oliver Archut

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1125
Re: Good Question!
« Reply #1 on: October 24, 2007, 03:13:02 PM »

Given the fact that there is U67>M269>U87 there is a pretty good analogy about differences in sound from tube, different tube and then transistor.

The same counts KM64>84...

To hear the difference transformer to none at all U87>U77

In my view it is pointless to compare because there is not one field effect transistor that has the same technical specs than a tube.
Also like someone pointed out the difference just by swapping the tube...

One of the easiest exercises in audio is changing a russian tube EF86 with a good NOS EF86 and hear the difference...

The same applies for field effect transistor of different manufacture in a KM88, not just the noise also the response...


Best regards,

Oliver
Logged
Oliver Archut
www.tab-funkenwerk.com

We are so advanced, that we can develop technology that can determine how much damage the earth has taken from the development of that technology.

Klaus Heyne

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3154
Re: Good Question!
« Reply #2 on: October 24, 2007, 03:27:06 PM »

All things being the same, you can expect a lower, harder, uglier headroom wall when you get into, or close to, overload with a FET mic.

The above is only applicable if it's a single FET design. As soon as you get into arrays of multiple semi-conductors, as in Neumann's Gefell's and many other manufacturers' op amp /chip based designs, the headroom goes much farther out, compared to the tube, but other objectionable side effects rear up.

Logged
Klaus Heyne
German Masterworks
www.GermanMasterworks.com

J.J. Blair

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 12809
Re: Good Question!
« Reply #3 on: October 24, 2007, 04:56:14 PM »

Is not even order harmonic distortion common with the types of tubes generally used in mics?  Please correct me if I don't understand that concept correctly.

I do know this much between any SS audio circuit and any tube circuit: they might very well have the same frequency response under static conditions, but their dynamic response will be different.

Also, I hate to use esoteric descriptions such as "warmth" and "color," but those are the reasons I reach for a tube mic rather than a FET.
Logged
studio info

They say the heart of Rock & Roll is still beating, which is amazing if you consider all the blow it's done over the years.

"The Internet enables pompous blowhards to interact with other pompous blowhards in a big circle jerk of pomposity." - Bill Maher

"The negative aspects of this business, not only will continue to prevail, but will continue to accelerate in madness. Conditions aren't going to get better, because the economics of rock and roll are getting closer and closer to the economics of Big Business America." - Bill Graham

compasspnt

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 16266
Re: Fet Mic VS Tube Mic:
« Reply #4 on: October 24, 2007, 05:13:12 PM »

But I would rather use a well-designed fet mic than a poorly designed tube one.
Logged

Klaus Heyne

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3154
Re: Good Question!
« Reply #5 on: October 24, 2007, 05:40:57 PM »

J.J. Blair wrote on Wed, 24 October 2007 13:56

... I hate to use esoteric descriptions such as "warmth" and "color," but those are the reasons I reach for a tube mic rather than a FET.


As some of you know, I've been deep into trying to improve U87 fet mics for a long time. Once you  eliminate Neumann's electronic circuit mess, and also equip the mic with a better transformer, and a high headroom FET, I find this "FET Sound" no longer to be an issue. Oliver Archut helped me take my work over yet another hump- one I was dissatisfied with in all U87s, and one that kept the mic in the "FET" sounding camp in the past. Yet, with  a scaled-back high frequency extension, and a lot of work, I now have to say: A well prepped U87 equals a U67 in the "warmth" department.

With other words: I shared J.J.'s opinion for a long time, but with advanced age (worse hearing?) and better mod methods, I have now come to the conclusion that warmth (I call it emotional attraction) is not an exclusive of tube mics, but is largely determined by circuit implementation and quality of components (assuming, the same capsule is used as in the tube mic it is being compared to).

Please remember: FET mics came onto the field at a time when even tube mics began to decline: ever more bells, whistles, and "frequency compensations" of all kinds where added, and started to dilute the original purity of the old, elegant tube mics. And FET mics took off from there, with yet still more garbage in the signal chain.

The one area where the single FET mic will always do more poorly is high sound pressure. Yet, even your comment of how harmonic distortion is being processed differently between a FET and a tube mic (f. ex. recording a nicely overdriven Selmer amp with EL84s) is minimized, if not eliminated, if your FET mic:

a. stays within safe SPL's
b. uses a superb capsule, signal path, circuit, and components
Logged
Klaus Heyne
German Masterworks
www.GermanMasterworks.com

David Bock

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 333
Re: Good Question!
« Reply #6 on: October 24, 2007, 05:56:06 PM »

Quote:

      
Is not even order harmonic distortion common with the types of tubes generally used in mics?
Mostly, yes, but there are several modern (tube circuit) techniques which add higher levels of a greater number of harmonics than the old methods you refer to.

The single fet may or may not have a complex harmonic structure depending upon its implementation, but the multiple semiconductor circuits (which comprise the majority of fet mics now) almost always have an overabundance of odd harmonics. They generally exhibit higher headroom than single fets or tubes, but almost universally are more complex and ugly sounding when that headroom is exceeded even slightly, as opposed to very linear (consequently gentler) distortion vs. input of a classic tube mic circuit.
regards,
David

J.J. Blair

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 12809
Re: Fet Mic VS Tube Mic:
« Reply #7 on: October 24, 2007, 06:17:42 PM »

compasspnt wrote on Wed, 24 October 2007 14:13

But I would rather use a well-designed fet mic than a poorly designed tube one.



That goes without saying.  414 vs. an MXL tube mic, almost always means 414 is the winner, from the MXLs I've heard.

Klaus, to what would you attribute the fact that this warmth is possible, but almost nobody is implementing it?  And if somebody is, which companies do you feel are doing so?
Logged
studio info

They say the heart of Rock & Roll is still beating, which is amazing if you consider all the blow it's done over the years.

"The Internet enables pompous blowhards to interact with other pompous blowhards in a big circle jerk of pomposity." - Bill Maher

"The negative aspects of this business, not only will continue to prevail, but will continue to accelerate in madness. Conditions aren't going to get better, because the economics of rock and roll are getting closer and closer to the economics of Big Business America." - Bill Graham

rphilbeck

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 604
Re: Good Question!
« Reply #8 on: October 24, 2007, 08:55:06 PM »

Oliver Archut wrote on Wed, 24 October 2007 15:13

Given the fact that there is U67>M269>U87 there is a pretty good analogy about differences in sound from tube, different tube and then transistor.



Oliver, thanks for your insight.  So the U87 is actually a U67 in every regard with the exception of the fet?  I was not aware of that.  Am I following you correctly?
Logged

J.J. Blair

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 12809
Re: Good Question!
« Reply #9 on: October 24, 2007, 09:07:09 PM »

The K67 is the same as the K87, except the backplates are electrically separated in the K87.  

The mics sound very different to me.  U67 doesn't have that honkiness around 1kHz that I don't care for in U87s.

I just got back from selling one of my U87s to Jerry at Coast, btw.
Logged
studio info

They say the heart of Rock & Roll is still beating, which is amazing if you consider all the blow it's done over the years.

"The Internet enables pompous blowhards to interact with other pompous blowhards in a big circle jerk of pomposity." - Bill Maher

"The negative aspects of this business, not only will continue to prevail, but will continue to accelerate in madness. Conditions aren't going to get better, because the economics of rock and roll are getting closer and closer to the economics of Big Business America." - Bill Graham

megaphone

  • Newbie
  • *
  • Offline Offline
  • Posts: 22
Re: Fet Mic Vs. Tube Mic: Do They Sound Different?
« Reply #10 on: October 25, 2007, 05:14:00 AM »

I can comment about the sound difference between my Schoeps M221's and CMC-6's equiped with the same capsules (MK4's and MK2's).

Both are in the same ballpark sound wise, but what JJ refers to as "warmth" might translate in a different frequency response curve. The M221b's are a bit richer in the lows, when the mids are scooped out in a nice way. One important thing to note, this warmth is not achieved at the expenses of the high frequencies response, which are comparable.

Hope that helps.

Gerard
Logged

Schallfeldnebel

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 816
Re: Good Question!
« Reply #11 on: October 25, 2007, 05:26:21 AM »

Klaus wrote:"The one area where the single FET mic will always do more poorly is high sound pressure."

I do not agree. B&K's have had since year and day highvoltage FET's. A capsule of 50mV ref. to 1 Pa does not even need a pad at all times up to a 150dB SPL. Pads on regular FET mikes are only there because the phantom power cannot pull it and some microphone pre's cannot stand the hot signal.

I agree when you would add to it "48V phantom powered without a DC-DC converter". 48V DC-DC converter equipped designs already do a better job, but the problem with FET microphones is phantom power.

In my opinion the drawback of the new microphone generation after the tube mikes is not the FET, it is phantompower.

May I cite Rupert Neve: " For this reason I have provided a high value of input impedance that will load microphones to the smallest possible extent and makes the best possible use of that limited “Phantom” 48 volts supply.

Erik Sikkema
Logged
Bill Mueller:"Only very recently, has the availability of cheap consumer based gear popularized the concept of a rank amateur as an audio engineer. Unfortunately, this has also degraded the reputation of the audio engineer to the lowest level in its history. A sad thing indeed for those of us professionals."

Oliver Archut

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1125
Re: Fet Mic Vs. Tube Mic: Do They Sound Different?
« Reply #12 on: October 25, 2007, 09:11:33 AM »

So the U87 is actually a U67 in every regard with the exception of the fet? I was not aware of that. Am I following you correctly?

The U87 was designed with the U67 circuit in mind, please take a look at function and roll off features, the general 87 Fet circuit is derived from the 67 circuit. If you take the polarization circuit aside there are only small changes, the feedback is not buffered through the x-former and of course fet specific changes for biasing the transistor. The U87a(i) is from a technical aspect even closer to a 67 but even then there are light years in sound and function.

Some Neumann Berlin close sources point out that Neumanns next U87 revision will be a TLM version....


Logged
Oliver Archut
www.tab-funkenwerk.com

We are so advanced, that we can develop technology that can determine how much damage the earth has taken from the development of that technology.

Gustav

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 70
Re: Fet Mic Vs. Tube Mic: Do They Sound Different?
« Reply #13 on: October 25, 2007, 09:43:12 AM »

Klaus I am not sure what you mean with higher headroom fets?  Do you mean a lower gain fet from a part number and/or a different process # fet(P#).  You still have the 22V supply and the possable Pease Cohen effect to deal with with P50s. Looking at the Older Neumann KMs, U87 schematics note the drain to gate voltage and Id

 Some different numbered fets are the same dies  but selected for IDSS etc and might have different cases and pinouts.  The 1982 NS transistor book has over 20 P50 fet numbers listed.  A 2n3819 is a NS (now fairchild) P50 and has a wide varition of specs.  Some BFs are P50

 Some older Schoeps and Neumann schematics I have seen have P50 listed.  The older battery u87s have worked on had 2n3918s and a large range of source resistor values and newer battery ones grey plastic k105s (looking for my notes it was a k10something?) Not sure what NS P number the japanese fets are like.


Single fet can have higher headroom look at the KM84 circuit with the way the pad cap and stock 4pf work.  I am not a fan of the sound change with the pad in but it is a single fet.  One can always drop the capsule voltage(IIRC tlm50 has a 20V setting), yes it changes the sound sometimes but at high SPL does that matter that much?

There is more going on between a FET and tube circuit sound change but that starts to get into math.
Logged

maxdimario

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3811
Re: Fet Mic Vs. Tube Mic: Do They Sound Different?
« Reply #14 on: October 25, 2007, 12:28:19 PM »

a fet mic sounds like a fet mic.

a tube mic, like a tube mic.

there are many different tube sounds, more than 'different' fet sounds.

A fet with no feedback sounds grainy, so usually feedback is employed to reduce the enharmonic distortion.

A good tube can be used without feedback.

Even at low levels fets sound more distorted, but in a rough glassy way, especially on sibilants.


poorly designed tube mics are just as bad as poorly designed tube mics in my experience... but this is a given in any piece of gear: bad design+cheap components = lousy sound.
Logged
Pages: [1] 2  All   Go Up
 

Site Hosted By Ashdown Technologies, Inc.

Page created in 0.116 seconds with 16 queries.