Panzerlord,
unless you have already done it, I think it very wise to always
make additional simulations where you put signal sources
in series with the rails voltage sources and do an AC sweep
with these, both one at a time and both simulataneously. It
probably won't tell you the whole truth about sensitivity to
rail noise and variations, but I have found such simulations
very interesting and revealing in some cases. It is probably
a good idea to also try pulse sources and do transient analysis.
unless you have already done it, I think it very wise to always
make additional simulations where you put signal sources
in series with the rails voltage sources and do an AC sweep
with these, both one at a time and both simulataneously. It
probably won't tell you the whole truth about sensitivity to
rail noise and variations, but I have found such simulations
very interesting and revealing in some cases. It is probably
a good idea to also try pulse sources and do transient analysis.
What`s the source of the higher THD tube amplifiers then?
This is my first contribution, hope you enjoy it.
Well, it's been said much on transistor sound, tubes, odd and even harmonics etc.
Personally, I not only belive in, but also can hear the diference between solid state and tube amplifiers.
Why? Although electronics design rules applied to audio amplifier design seem to lack
any revolutionary concepts since late 50-s and later "transistorized" tube designs
undergo many "improvements", there are still significant differences in designs around tubes
compared to solid state solutions. Let us disentangle some mysteries:
1. The emphesized "low THD" is NOT the exclusive attribute of transistor amplifier.
2. We have bipolar and (MOS)FET transistors and triode/penthode types of tubes. There
are some similarities between both worlds, but this worlds lay far apart of each other.
3. I could imagine to build a tube amplifier simulating a transistor amplifier.
4. If I had to build a transistor amplifier simulating a tube amplifier, I have a big trouble.
5. I belive what a musician says, when he says "this amplifier is not for me". In most cases
it is a transistor amplifier.
6. (MOS)FET is the sole generic transistor corresponding to a penthode-tube; I never heard of solid
state device comparable to a triode.
7. U/I characteristics are by far different, when comparing transistors and tubes (excluding
RF power tubes, as used in radio or TV transmitters).
This points (especially pt.6) are the main reason of differing sounds of the "two different worlds".
This is my first contribution, hope you enjoy it.
Well, it's been said much on transistor sound, tubes, odd and even harmonics etc.
Personally, I not only belive in, but also can hear the diference between solid state and tube amplifiers.
Why? Although electronics design rules applied to audio amplifier design seem to lack
any revolutionary concepts since late 50-s and later "transistorized" tube designs
undergo many "improvements", there are still significant differences in designs around tubes
compared to solid state solutions. Let us disentangle some mysteries:
1. The emphesized "low THD" is NOT the exclusive attribute of transistor amplifier.
2. We have bipolar and (MOS)FET transistors and triode/penthode types of tubes. There
are some similarities between both worlds, but this worlds lay far apart of each other.
3. I could imagine to build a tube amplifier simulating a transistor amplifier.
4. If I had to build a transistor amplifier simulating a tube amplifier, I have a big trouble.
5. I belive what a musician says, when he says "this amplifier is not for me". In most cases
it is a transistor amplifier.
6. (MOS)FET is the sole generic transistor corresponding to a penthode-tube; I never heard of solid
state device comparable to a triode.
7. U/I characteristics are by far different, when comparing transistors and tubes (excluding
RF power tubes, as used in radio or TV transmitters).
This points (especially pt.6) are the main reason of differing sounds of the "two different worlds".
Well, I`m through testing (at least for the moment), and the results where somwhere close to what I ecxpected.
But I was wrong about the JFET though, so I have to give Steven credit for that one!!
.
I also have second thoughs about the wilson current mirror as a current source for my amp after this....
Here what I`ve tested:
1.Wilson current mirror, with JFET current source (my "design")
2.Wilson current mirror as a current source
3.Vbe current source
4.Current source with transistor and two diodes Iref=0,7/R
dI=current variation through R3!
Numbers 1-3 where close, actally nr 1 came 3rd with dI=1.uA, nr. 2 had dI=0.67uA and nr. 1 dI=0.3uA.
Number 4 was so large I didnt bother to read the values, but I think the variations where around 30uA or something...
But I was wrong about the JFET though, so I have to give Steven credit for that one!!
.I also have second thoughs about the wilson current mirror as a current source for my amp after this....
Here what I`ve tested:
1.Wilson current mirror, with JFET current source (my "design")
2.Wilson current mirror as a current source
3.Vbe current source
4.Current source with transistor and two diodes Iref=0,7/R
dI=current variation through R3!
Numbers 1-3 where close, actally nr 1 came 3rd with dI=1.uA, nr. 2 had dI=0.67uA and nr. 1 dI=0.3uA.
Number 4 was so large I didnt bother to read the values, but I think the variations where around 30uA or something...
Re: What`s the source of the higher THD tube amplifiers then?
may be there is a difference between performance under "repeatitive" sine waves, vs. real world music. transient reponses, for example, isn't as important with sine waves but is with music.
I am not sure about this. There are empirical tests where people cannot tell the two amps apart. and I haven't seen the other way around.
that would be meaningful if the "configuration" of a tube contributes differences in sound.
it may be too early to conclude that there is a "tube" sound (vs. ss amps of similar performance). tube amps tend not to performance well in higher frequencies so that may contribute to their "perceived" sound characteristics. Plus they do performn differently in clipping but that can be dealt with in a SS amp as well.
Lelak53 said:
may be there is a difference between performance under "repeatitive" sine waves, vs. real world music. transient reponses, for example, isn't as important with sine waves but is with music.
Lelak53 said:
I am not sure about this. There are empirical tests where people cannot tell the two amps apart. and I haven't seen the other way around.
Lelak53 said:
that would be meaningful if the "configuration" of a tube contributes differences in sound.
Lelak53 said:
it may be too early to conclude that there is a "tube" sound (vs. ss amps of similar performance). tube amps tend not to performance well in higher frequencies so that may contribute to their "perceived" sound characteristics. Plus they do performn differently in clipping but that can be dealt with in a SS amp as well.
Aside from clip performance, another major difference with a tube amp is damping factor, which contributes to the soft bass and long decay of tube amps.
If you take global feedback from the drivers (or the voltage amplifier) of a SS amplifier, you obviously increase the output impedance. You also improve its tolerance to reactive loads enormously. What is not realized is that the sonics then become very like a tube amp, with marvellous imaging, long decay and soggy bass. Some people love this sound of course; others don't. But it can actually be configured as fully adjustable; now that's an interesting concept!
Cheers,
Hugh
If you take global feedback from the drivers (or the voltage amplifier) of a SS amplifier, you obviously increase the output impedance. You also improve its tolerance to reactive loads enormously. What is not realized is that the sonics then become very like a tube amp, with marvellous imaging, long decay and soggy bass. Some people love this sound of course; others don't. But it can actually be configured as fully adjustable; now that's an interesting concept!
Cheers,
Hugh
I agree Hugh
moreover, a high output impedance (low damping factor)
makes the freq. response of the amplifier very sensitive to variation in the impedance modulus vs. freq. curve of the speaker system.
once I had a Carver unit with a very low damping factor (8)
to emulate tube amp. sound. The result, was a lucid brilliant
sound in the range 2k-3k Hz where my speakers have a impedance peak, and a soft bass. However, it did not succed
to emulate well a tube amp. In any case, I think it is possible.
Federico
moreover, a high output impedance (low damping factor)
makes the freq. response of the amplifier very sensitive to variation in the impedance modulus vs. freq. curve of the speaker system.
once I had a Carver unit with a very low damping factor (8)
to emulate tube amp. sound. The result, was a lucid brilliant
sound in the range 2k-3k Hz where my speakers have a impedance peak, and a soft bass. However, it did not succed
to emulate well a tube amp. In any case, I think it is possible.
Federico
Dear Hugh:
Some time in the 1980s, Luxman released a kit power amp called (I think) the A901. It was designed so that, at the touch of a front-panel switch, the user could choose between global feedback from the output devices, or a smaller feedback loop from the driver stage. You could also select between stereo and BTL mono, full Class A and rich Class AB.
From memory, the topology was input N-channel LTP with current-mirror summing, into a single PNP folded-cascode with an active load on the negative side, and then a Darlington PP output stage.
Fun toy to play with if you can find one.
best, jonathan carr
Some time in the 1980s, Luxman released a kit power amp called (I think) the A901. It was designed so that, at the touch of a front-panel switch, the user could choose between global feedback from the output devices, or a smaller feedback loop from the driver stage. You could also select between stereo and BTL mono, full Class A and rich Class AB.
From memory, the topology was input N-channel LTP with current-mirror summing, into a single PNP folded-cascode with an active load on the negative side, and then a Darlington PP output stage.
Fun toy to play with if you can find one.
best, jonathan carr
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.