Tubes vs SS (Your thoughts)

organ · May 2004

Just wondering what your thoughts are one the tube vs SS debate. Why each device have their own sound.

Here's what I think...Current in tubes is constantly running like a closed switch. Transistors act as switches even for amplification (not class A amps which are set to run constantly). When there is no signal, the transistor is 'off' but the problem is getting it to turn 'on' and conduct current. It takes approx 0.7V at the base to trigger the transistor. So to complete one cycle (1hz), 0.7V is lost from turning on and off. So to play a 2K hz signal, you lose quite a bit from your original signal. IMO, the voltage lost at the base during turn on and off gives SS amps a grainy characteristic compared to the smooth sound of tubes.

A transistor contains three parts: Collector, Base, and Emitter. The main power is connected to the Collector. This is where 99% of your amplified power comes from. It's just clean power with no signal from the source yet. The power from your source is connected to the Base. In order to amplify a signal, you need to push around 0.7V though the Base because it is made up of semi conductive materials. This opens up the junction and you get an output at the Emitter. So let's say you have 10V at the Collector and you push 2V through the Base. Now you have to subtract 0.7V from the Base to get your power to flow effortlessly through the semi conductive part of the transistor. So your amplified Voltage at the Emitter will be 11.3V.

Let's say this an electron conducting:

This is an electron not conducting:

You get:
Transistor in the off stage...
[COLLECTOR:( (10V)]-->[BASE]-->[EMITTER]

Thus, no current flow because there's no Voltage at the base to open up the semi conductive barrier. No output from the Emitter

Now, a transistor conducting current...
[COLLECTOR:) (10V)]-->[BASE:) (2V-0.7V)]-->[EMITTER:) (11.3V)]

Now the electrons are happy.

You have 10V from the amplifier, 2V from the pre amp, and 11.3V at the output.

The Base receives AC voltage from the pre amp. With AC Voltage you get a sinusoidal wave which rises and falls under the 0V line. Everytime the transistor have to turn on, it starts around 0.7V. After it reaches the +ve peak, the wave needs to come back down. So to complete a 1hz signal, 0.7V is lost.

I think this turn on/off stages of the transistor can be audible and we get a sound that's not as smooth as tubes which are constantly running without having to turn on or off. That's not all. I also think the distortion in tubes have an impact in the overall sound. IMO, the smoothness we hear in tube sound is due to the tubes constantly conducting power and the 'warmth', 'air', etc is from distortion in tubes.

Yeah, as you can see I'm a little bored right now:)

Let's hear your thoughts on the tube vs SS sound.

Maurice

madmax · May 2004

I think what you are describing crossover distortion in a way. I understand what you are saying about the .7V but I've seen the output signal on a scope with a sine wave as the input and you cannot see this .7V so something in your example is wrong. I should be able to tell you off the top of my head but I'll have to look into it.

My theory is (and I've read much supporting material) that tubes produce even order harmonics (ones that blend in with the original and sound pleasing) more so than odd order harmonics which clash with the original. Transistors tend to produce odd order harmonics. The idea here is that even order harmonics can be a good percentage of the sound without you noticing whereas even the smallest amount of odd order is extremely disagreeable. By the way even order harmonics are called "harmonic distortion" and odd order are called "intermodulation distortion". This was explained in one article I read by describing a choir. Everyone can be singing very loudly and all is well but if even one person is singing slightly off key (even at a very low volume) it sticks out like a sore thumb.

madmax

BTW, when I first switched to tubes I noticed a lack of this offending sound. For quite a while every time I listened to a SS amp I could hear this noise vividly. After a few years now I cannot pick it out as easily. I guess I've become used to both variations at this point. Back at the time though it was extremely annoying to listen to SS even for a very short amount of time because this noise is all I could focus on.

gmorris · May 2004

You guys seem to know your stuff, thus I have nothing to add really, just thought I'd post a link to an article you may enjoy.

Hope you like it: http://www.soundstage.com/gettingtechnical/gettingtechnical.htm

dcarlson · May 2004

Interesting article.

I don't have much to add myself except I'm diggin tubes. I don't really care about what's going on technically, it would take too much brain power to get it through my thick noggin and every new thing that goes in pushes something out.

I had a buddy over on the weekend who wanted to listen to the difference between the Dynaco and the Musical Fidelity integrated's amp. He preferred the MF because of the highs, although he is a TRUE treble **** and whenever I hear any of his stereos, be it car, boombox or whatever (all lower quality stuff), he keeps his treble at ear bleeding levels. I think he mistakes treble for detail. He didn't care about the depth the tubes presented. So, case in point, tubes were a very hard sell to him.

I've always had this thought of how I wanted my system to end up (if it ever comes). To sum it up, I'd say my goal would be a dimly lit room with a calm relaxing and natural sound accompanied by a nice cold brew. Vinyl helped quite a bit and I feel more so the dynaco has put me on my way towards that goal. It's thanks to this board that I have the dynaco. Maurice with your tube raving, Gidrah with his wife crying story, Tour with his constant and rock solid help and Madmax and Russ and...and... really everyone here. So for that I give a heart felt thanks to all of you guys. I'm still debating on a tube pre simply because of the funds got used up on the Dynaco.

steveinaz · May 2004

Like all things "audio" I'm a firm believer in pitching the spec sheets/techno-babble and listening. If it sounds good, its for you. Its all about enjoying the music, and if you get away from that principle, this hobby can drive you nuts.

disneyjoe7 · May 2004

SS my input (getting older but this is what I can remember).

The .7 volt bias forward is correct, this voltage must be over come to get any current out of collector / emitter junction. Most amps are designed with complementary pairs 1 NPN and, 1 PNP where as the emitters are tied together the collectors are tied to the voltage rails +/- one collector to + the other to -. The transistors pair will give you the positive, and negative of the sound wave. The term of A A/B biasing is just that all amps must be A/B or just pure A this is due to that .7volt base voltage needed the NPN and PNP output transistor are biased "ON" somewhat this works above that .7volt thing. This biasing "ON" will give you some heat / current draw just idling / on sound output.
Output pre drivers are the voltage of the amp where the Output transistors are given you the current of the amp output.

Now this brings up this class D amps? I really have no idea how these work. Class D when I went to school was 100% ON / 100% OFF in since a square wave not a sound wave by any means. Now class G amp wasnt even in the book I had in school or ever read.

madmax · May 2004

Great description!
I thought about it a little today and still didn't figure out the .7 volt stuff. It is something to do with how each transistor is biased but I'm not getting how exactly. I'll keep looking.
madmax

disneyjoe7 · May 2004

I have to break out a 20-year book to help describing bias even more.

disneyjoe7 · May 2004

BTW madmax,

On a scope if you ever seen the .7 difference the bias circuit / pre and or the output trans are bad. Most amp are A/B design, so a small output like .25 / .50 watt is class A meaning this level of output is under the bias voltages so both transistors are driving load.

Its the only way an amp can be distortion free at this output level.

organ · May 2004

Originally posted by steveinaz
Like all things "audio" I'm a firm believer in pitching the spec sheets/techno-babble and listening. If it sounds good, its for you. Its all about enjoying the music, and if you get away from that principle, this hobby can drive you nuts.

And that's exactly what we do. Most of the people on te 2ch forum prefer tube sound even though the specs can somtimes be inferior compared to SS.

Just trying to figure out what gives each amplification device its own unique sound. I don't need spec sheets, I'd take tubes over SS any day.

Maurice

organ · May 2004

Madmax,
I have measured voltage at the emitter with a scope to get the pk-pk value but never seen the 0.7V drop. But when you look at the numbers it's clear voltage was lost in the transistor. I think the scope should be set to 1V/Div or lower to clearly see it. I was measuring output at about 5-10V/Div, so 0.7 was too hard to see. I agree with you on the distortion. It seems like SS have a 'cold' and 'dry' sound while tubes are 'warm', 'wet' and 'splashy'.

Gmorris,
Thanks a lot for the link. I really enjoyed reading thearticle.

Derick,
Glad to hear you're really diggin the Dyna. Mine is all good again and I love the sound. Whenever I'm listening to the Dyna, I never think about upgrading the amp. The sound is just perfect.

Those treble whores are crazy. When they listen to a real system, they say it lacks detail because of the flat treble setting and complain about bass because our bass is more accurate with levels that match the rest of the system. I know a few people like that and it's not easy to impress them with a high end system but get them a ghetto blaster and they're jammin.

So do you like the sound of your Dyna more than the MF? I also find that the emotions in music comes out better through tubes.

Disneyjoe,
We discussed digital amps a few months back. I'll look for the thread later and post a link. What we found out was that the output could beconrolled using a combination of PWM (pulse width modulation) and PAM (pulse amplitude modulation).

Maurice

organ · May 2004

Originally posted by madmax
Great description!
I thought about it a little today and still didn't figure out the .7 volt stuff. It is something to do with how each transistor is biased but I'm not getting how exactly. I'll keep looking.
madmax

Easiest way to explain is to look at a dam. Pretend one side of the dam where the water level is higher is the Collector. The dam holding all that water back is the base. The other side were there's no water is the emitter. You need to open up the dam(base) to get water to flow from one side to the other.

You can look at a doorbell the same way too.

When transistors first came out, they were meant to be used as switces. What you get is a semi-conductor sandwiched between two conductors. You need a little push at the semi conductor to get current to flow throug it.

Maurice

madmax · May 2004

Yea,
I know all that but in an audio circuit, for example a push pull, one transistor outputs the positive half and the other transistor outputs the bottom half. The textbook circuit of the push pull design would act as you originally said but in the real world design it is compensated for. I looked around and here is what I found. This is one very simple method which takes care of the problem but I think most designs are much more complicated. I don't think you will ever see the .7V in any audio amplifier. Look at the first circuit and then the second one. You can skip the calculations.

http://www.ecircuitcenter.com/Circuits/pushpull/pushpull.htm

madmax

disneyjoe7 · May 2004

Madmax,

With 1 transistor on the plus side, 1 transistor on the neg side the bias voltage will get both of them to give a little current. This current should be given some voltage also, the balance of the transistor should

give the same current output so the plus one is given the neg the same output, so the output is "0" voltage in idle.

This bias voltage is there to reduce distortion.

organ · May 2004

Madmax,
I'll have a look later tonight. I'm at school right now.

Disneyjoe,
Here's a link to class D amplification we discussed before. My explanation is close to the bottom of the 1st page... http://clubpolk.polkaudio.com/forum/showthread.php?threadid=17326&highlight=pwm

Maurice

dcarlson · May 2004

I can say I like them both, right?

With MF acting as a pre for the Dynaco, I'm not sure it's fair to judge the two against each other just yet. I also haven't done much side by side comparisons and have yet to change the power cord on the Dyna. I do like the sound the tubes bring, hence the push for me to find a tube pre. The Dynaco seems to give much more realism all around and adds a very nice 3D depth to the music. The MF on it's own brings a little more sparkle which isn't a bad thing. The soundstage does seem more 2D and the MF is probably suited better for difficult material. So for now, I'd say it's a bit of a toss up with the Dynaco being favored.

organ · May 2004

That's cool. I'm also using a SS pre right now because the ASL is messed up. The NAD pre is Class A. It doesn't sound as good as having a tube pre/tube amp but I'm still getting half the tube sound with a little SS signature in the high frequency. Is your MF's pre section a Class A?

Maurice

Tubes vs SS (Your thoughts)

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