How close have/can we come to tube sound emulation with SS?

[MattAnonymous]

I've seen various FET emulation circuits by the nice people at runoffgrove recently, but really how close are we to scientifically matching the soft smooth tube wave patterns.  How close can we get?  Does anyone have a theory such as an array of electronics that would clip at different times to produce a smooth wave pattern?  Just curious because I'm tired of people bashing the technology that allows me to sleep in the same room as my computer, TV, Stereo, amp, alarm clock, well you get the point.

In my opinion, people only like tube sound because it's all they've heard since the beginning of amplified music.  Also, if you think about it tubes are a lot more complicated than trannies.  Anyway, that's my $.02.  BTW any more news on those printable transistors that aron mentioned recently?

[Joe Davisson]

This is an interesting topic to me. The BJT is the closest sounding to the electron tube, when the dynamic response is limited. There's nothing inherently wrong with solid-state electronics that prevents tube sound. The bad rap is based on the general assumption that transistors and diodes "snip" the signal harshly and have no dynamic response. Those attributes can be controlled.

There's a better way to bias those JFETs than just a 1M resistor. Try using a regular voltage-divider for the bias, like 10M/1M. It improves the consistency between JFETs (which varys wildly otherwise) and prevents the inputs from locking-down, which causes hangups when playing.

I recently tested a 5-stage JFET circuit, and the diode-compression scheme helped tremendously. Later, I realized 3 stages was enough, if the drain/source resistors were increased to raise the gain. Here's the page for the diode-compression:

http://www.analogalchemy.com/diodecomp.html

This lowers the gain, so if emulating a particular tube circuit, raise the drain and source resistors until the gain level is correct. 100k/10k will get a lot of gain. As you raise these values, the source bypass cap can be lower in value for the same frequency response.  A good rule of thumb is to start with the source resistor, and bias resistors, then adjust the drain resistor until the output is at 1/2 supply voltage. This maximizes the headroom.

Unproven conjecture to follow:
Harsh sound comes from "stuttered" frequencies produced in the 30-40 hertz range. Some chords create these frequencies, even though all the notes are much higher. Our physiology produces a negative emotional response when these are severe (bears growling, babies crying, thunder, etc).

When waveforms are smooth, the low frequencies created are also smooth, preventing the stuttering effect which jars our ears. So I think there's a legitimacy to good tube tone.

-Joe

[brett]

When waveforms are smooth, the low frequencies created are also smooth, preventing the stuttering effect which jars our ears. So I think there's a legitimacy to good tube tone.

For sure.  The basic reason we make music is to create emotional and psychological responses.  Does death metal FEEL different to Bach?  Headbanging to Bach doesn't isn't in us.  

Why does SS clipping sound harsh/bad?  Because we were born to dislike that sound.  It FEELS bad.  We've spent hundreds of years designing guitars to sound sound more sweet and true and good, and rejected designs that sound buzzy or clipped or don't sustain.  There's obviously something fairly sweet and enjoyable about tube clipping for most people who like rock n roll.  Don't forget that this might not be true for people who dislike distortion, like classical musicians.

[javacody]

What is a "regular voltage-divider"?

You mean like the 10k/1k on the diode compression schem?

Also, what if you used different diodes? Would other diodes allow more signal through, thus working better with JFETs?

[Jered]

Hi Matt,
     If your playing a solid state amp and ever want it to sound like an overdriven tube amp, I've got three words for you,...meteor, meteor, meteor.
Jered

[MattAnonymous]

How 'bout those good ol' germanium transistors?  Wasn't there an inconsistancy, as there is in tubes, in the clipping and sound?  I'd think with technology today that we could at least develop something close to the sound through solid state.  Do you guys think that people will eventually get used to the solid state sound?  Most pop (at least the stupid talentless crap) is SS now and few bands are seen with marshalls and fender twins these days.  It's sad to see a vintage technology go.  I'm just planning for the future which is probably in emulation once tubes aren't profitable to make or sell.

[will]

Hi Joe,

I find your post very interesting.

There's a better way to bias those JFETs than just a 1M resistor. Try using a regular voltage-divider for the bias, like 10M/1M. It improves the consistency between JFETs (which varys wildly otherwise) and prevents the inputs from locking-down, which causes hangups when playing.

I thought the 1Meg resistor is to loosely hold the Fet input to ground. Doesn’t the source need to be positive with respect to the gate? Is this lockdown “hang-ups” causing the “stuttered” frequencies when overdriving/clipping some chords due to large amounts of low frequency content?

I wonder if this is why a lot of tube amps elevate the base (grid) on the stage before the output stage so they have more input swing headroom.

I recently tested a 5-stage JFET circuit, and the diode-compression scheme helped tremendously. Later, I realized 3 stages was enough, if the drain/source resistors were increased to raise the gain.

I would be interested in seeing your JFET circuit.

Unproven conjecture to follow:
Harsh sound comes from "stuttered" frequencies produced in the 30-40 hertz range. Some chords create these frequencies, even though all the notes are much higher. Our physiology produces a negative emotional response when these are severe (bears growling, babies crying, thunder, etc).

I’m interested in boosting the range of frequencies that produce a positive emotional response, like sonic Opium, any insight?

Regards,
Will

[Jason Stout]

The biasing arrangement that Joe is refferring to can be seen ::here::  See page 5 figure b. I call it voltage divider biasing.

[RedHouse]

I disagree that SS -vs- Tube sounds bad.

25 years going now I've heared PLENTY of crappy sounding tube amps, and plenty more crappy sounding SS amps and effects.

IMHO, SS can sound really good ...just needs care/tweaking... like for instance the miss-piggy thing going on around here which helps makes a SS FF sound SO much better than non-piggybacked SS FF.

And SS stuff can brutally over-emphasize highs, so great care can be taken to roll-off highs in a musical way. I managed to get a protoboard SS fuzzface circuit to sound very nearly the same tonally as a Ge Fuzzface but had to add a lot of pF's for HF rolloff.

[brett]

Please tell us how many and where you added those pFs to Si Fuzzface.

[bwanasonic]

I'm tired of people bashing the technology that allows me to sleep in the same room as my computer, TV, Stereo, amp, alarm clock, well you get the point.

I don't think a preference for tube amps is a condemnation of your alarm clock, but maybe thinking of this in terms of *natural* vs. synthetic fabrics would be a useful analogy. When I get on my bike, I'm prone to garb myself in spandex and other *tech* fabrics (not a wool jersey guy), but when I'm just hangin' *being me*, I'm all about well-worn 100% cotton. Sure, someday there probably won't be any real cotton left due to some enviromental catastrophe, but until then...

Kerry M

[Lonestarjohnny]

Pretty close guy's, I just listened to the 18 soundclip's over at Runoff and I'm gonna tell you those guy's are slowly changing my way of thinking about S/S AS being called " That other Sound "
JD

[Danny G]

In my experience, solid state amps (guitar or bass) tend to get drowned out in live situations.  Guitars sound shrill, bass amps produce lows that can be felt, but not really "heard."  They just don't seem to cut through.

I know EQ settings and the players themselves are alot of this problem, but for me nothing beats a good sounding tube amp.