WHY do tube preamps sound different than Solid State?

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rollo

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Re: WHY do tube preamps sound different than Solid State?
« Reply #20 on: 18 Feb 2019, 07:58 pm »
Hi,
     does vacuum tube rectification vs. silicone diodes for rectification have anything to do with the sound?....Mark Korda

   Why certainly. They argue mostly accuracy and noise over tonality and harmonics. Both can be executed expertly for measurements however can sound totally different.


charles

Norman Tracy

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Re: WHY do tube preamps sound different than Solid State?
« Reply #21 on: 18 Feb 2019, 09:15 pm »
Naimnut questioned:

Q1. "I've read comments to the effect that "as you approach the state of the art, solid state and tube equipment begins to sound very similar".

I would agree with that, however then hasten to add that "as you approach the state of the art” smaller differences have a greater effect. An analogy is wet sanding then polishing a high gloss finish on a speaker or car, the more one polishes the better all the details (and alas defects) are revealed. Thus a paradox, they sound more alike but the perfectionist builders and owners of high-end hi-fi care ever more about the ever smaller differences. Also keep in mind there is a niche branch of hi-fi tube electronics designed for a very specific house sound; beauty first, accuracy second. The sound of a Shindo Masseto Tube Preamplifier will never converge with a Boulder 3010’s.

Q2. “I've read that tube equipment tends to generate more even-ordered harmonic distortion. Does this mean that distortion in a tube preamp can cause the sound to come across as "richer" and "fatter"?”

Yes, and a universally recognized master of solid state hi-fi design Nelson Pass has shared his insight that the phase of the distortion harmonics vs. signal also has an effect.

Q3. “I've read with interest Roger Sanders excellent white paper on tubes vs. solid state, and his comments make sense, for power amps. But what about preamps? Do preamps clip?”

I would say in 99.9% of the use cases that hi-fi stereo preamps do not clip. Typical power amps only require 0.5 to 2 volts of signal input to output their hard clipping maximum power and preamps can supply 10 times that.

Q4. “It seems that several factors greatly influence the sound any preamp - the quality of the power supply (bigger, stiffer and isolated in a separate box seem to be important), the quality of the volume control, the quality of the transformers...Frankly I'm out of my depth here, but some of you might be able to help me understand this better.”

That is not so much a question as an outline for a master thesis on hi-fi electronics design. I would agree with your list adding quality of all parts to it while noting that personally I have come to doubt isolating the power supply in a separate box is always necessary. Back to the tube vs solid state question one of my pet theories is that a good chunk of the seemingly intrinsic difference flows from the fact they operate in such different voltage domains. The passive components (resistors, capacitors, diodes, switch contacts, etc.) in the tube circuit have 100s of volts on then compared to the solid state circuit with 10s of volts. Thus the ratios of the signal voltage to the parts’ non-ideal secondary characteristics are very different in the two types of circuits.

Q5. “Some highly rated tube preamps have multiple tubes, and use some in the power supply. Others have very few. How should a person think about this?”

Engineering design takes a design requirement in this case ‘sounds amazingly like real music, interfaces with my existing equipment, is reliable, X inputs, to Y outputs in format(s) Z, user interface like this all achieved in a cost budget of so-much’. Then one considers every circuit ever devised (and newly invented if one is feeling especially confident this week) these weighted towards what has worked for the designer(s) in previous designs. Fitting all that together is very much an art of weighing the compromises of the various options and picking the tradeoffs that best deliver the desired results. These tradeoffs’ weighting also very much include the designer’s and brand’s overall philosophy. As an example I highly value ‘transparency to the source’ and that tends to be easier (and less expensive and potentially more reliable) to achieve with fewer tubes as few as one per channel for a line stage. HOWEVER, if the design requirement also includes the ability to drive low impedance loads like 600 ohm pro-audio gear or (quite likely in 2019) headphones that calls for more tubes with some providing voltage gain and others following later in the circuit providing current drive.

Naimnut observed “use some (tubes) in the power supply” and Mark Korda asked “does vacuum tube rectification vs. silicone diodes for rectification have anything to do with the sound?”

First short answer is across all types power supplies have everything to do with the sound. Sometimes we find tubes in the power supplies simply because the designer(s) and/or the brand and/or their customers are dogmatic ALL TUBES, NO SOLID STATE. Sometimes because they look cool, I am thinking the blue glow of mercury vapor rectifiers. Technically using a tube in a place like the pass element of a regulator can be justified because it is regulating the 100s of volts it was designed for and in such an application if a fault develops a 6550 will survive while a MOSFET dies immediately. In rectification when compared to silicon diodes tube rectifiers generate less high frequency noise when they turn on 50 or 60 times a second. The solid state designer can answer that with filters around the silicon diodes or by using Schottky diodes. The tube rectifier can be quieter, but it will likely not deliver as much current as quickly as a solid state design.

The above just touches the questions asked above from a decidedly engineering perspective. To rework the old saying about real estate what counts is ‘implementation, implementation, implementation’. As you consider your upgrade it is fun to count the tubes like a watch collector counts the complications in a mechanical watch movement. I council to consider that as part of the story while also weighing the capability of those who take a clever design and turn it into the actual thing you unbox and wire into your hi-fi rig.

twitch54

Re: WHY do tube preamps sound different than Solid State?
« Reply #22 on: 18 Feb 2019, 10:06 pm »
Thank you Norman, good read .....  :thumb:

Naimnut

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Re: WHY do tube preamps sound different than Solid State?
« Reply #23 on: 18 Feb 2019, 11:49 pm »
Norman,
That is very helpful.
Markus / naimnut

UncleMeat

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Re: WHY do tube preamps sound different than Solid State?
« Reply #24 on: 2 May 2019, 05:47 am »
I've slowly transitioned from SS preamps, amps over to tube equipment.  I started with tube buffers and tube output CD players and immediately noticed a sound that was much closer to the sound of my vinyl.  From there I went into modding a dual-mono guitar amp and it was a bit of a chore/challenge but the result was an improvement as well.  I've added a tube phono pre and tube linestage and the result is simply stunning.  The music sounds much more 'real' with no noticeable loss of detail and an improvement in imaging as well.

If tube amplification is adding even order harmonic distortion, then I would say that harmonics are what were lost/missing in the original recordings.  I listen to everything from 50's jazz/blues/country/pop to new releases and it all sounds better to me with good tube amplification.

We're talking about small amounts of harmonics, the ear can tolerate up to about 5% harmonic distortion before it's noticeable as a 'flaw', but the harmonic distortion added by a tube amp or preamp is much lower.

Tyson

Re: WHY do tube preamps sound different than Solid State?
« Reply #25 on: 3 May 2019, 01:21 am »
Let's not forget the role of feedback.  I have a pet theory that it's the lack of large amounts of feedback in a tube design that makes it sound so good, not necessarily 'second order harmonics' being added.  The human ear is very sensitive to this type of feedback, so removing equipment that uses medium-to-lots of negative feedback (most SS gear) from the signal path usually results in things sounding 'more real'.

Steve

Re: WHY do tube preamps sound different than Solid State?
« Reply #26 on: 3 May 2019, 03:11 am »
Many excellent answers and I would like to add a few more. Implementation is extremely important.

1) Besides even vs odd distortion products, some tubes have much less distortion than others. For instance,
JJ's E88cc has some 1/9th the distortion of any other tube I have ever tested. As a reference, where as a typical
tube, say Bugleboy or a 6sn7 might measure 0,1%, the JJ measures .012%, some 19 db less. -60db vs -79db is
quite a difference.

However, there is a negative. Where as one may vary critical parts with typical tubes and not notice any changes in sound
(sonic signature problem), the JJ is extremely critical. Besides the correct parts value, a must, the JJ E88cc requires the tightest tolerance parts, 0,5%, or one will not achieve sonic consistency from component to component.

2) Both tubes and solid state parts (let us use FETs as example) have interelectrode capacitances. Vacuum tubes have  metal parts with low resistance/inductance and a vacuum as the dielectric (1.0000) of the internal capacitances.
 
Solid state parts (transistors in our example) have semiconductor material with much much higher resistance/impedance, and dielectric constant. Silicon, itself, has a dielectric constant of 11.0 or so.
Doping materials are also high. FETs have varying junction capacitances, often up to 25 DC volts between Drain and Gate. So as the signal amplitude varies, and voltage varies the capacitances varies.

Then we have to contend with Miller capacitance, which is 1 + device gain times the grid to plate (collector to base, drain to gate) capacitance. This FET junction capacitance can become quite large, varies with voltage as previously stated, thus Miller capacitance can become huge.

3) Differences in the power supplies. Solid state generally has filter capacitors for each stage, no chokes, and gigantic capacitors in the output stage of said amplifier. Preamplifiers, generally no gigantic capacitors.

Gigantic capacitors have a tendency to become inductive as low as a couple of khz. Not good. In otherwards, they resonate as low as a couple of khz. Becoming inductive means the high frequencies might become exaggerated.

4) Tube power supplies tend to have smaller capacitors, which results in much higher frequencies before becoming
inductive. This is good. Smaller size ufd means one may be able to use polypropylend vs electrolytic type capacitors.

However, many tube components use chokes which is a bad thing. Chokes cause variable isolation between filter capacitors, which is especially important between the decoupling capacitor C2, and previous filter capacitor C1. The musical signal directly sees the decoupling capacitor, C2. For instance, suppose we use two 50 ufd filter capacitors, C1 and C2, separated by a 10 henry choke.

At 20 khz, the choke has a reactance of 1,256,000 ohms. There is huge isolation between C1 and C2
At 2000 hz, the choke has a reactance of 125,600 ohms. The isolation is lowering, but still pretty good.
At 200 hz, the choke has a reactance of only 12,560 ohms. Isolation is not that good.
At 20 hz, the choke has a reactance of only 1,256 ohms, hardly any isolation between C1 and C2. As a result,
C1 will interact with C2. So C2 is not C2 anymore. Yet at 20 khz, virtually no interaction between the capacitors.

Solid state power supplies, on the other had, use resistors, generally do not chokes in the power supply filtering system, thus much more constant isolation between filter capacitors, even if not complete isolation between capacitors. Because of the inferiority of chokes, and number of filtering stages, interactions occur between the musical stages and power rectifiers, power transformer, even power cords. Rollo is quite correct.

That is one way you can tell if the power supply has been adequately designed. Heavy weight is not always important, especially in preamplifiers. Yes, in amplifiers, the power transformer size and weight is important (except for possibly toroidal vs EI core types).

5) Generally, fewer stages are used in tube designs vs solid stage. Fewer stages can mean less distortion, interaction between stages due to common power supply. There is more to distortion than harmonic and intermodulation. There are frequency distortion, phase distortion, transient distortion, dynamic range distortion, scale distortion etc.

6) There is a difference in output impedances (Z) between tube and solid state amplifiers, that of damping factor.

Cheers and hope this helps.

steve







bladesmith

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Re: WHY do tube preamps sound different than Solid State?
« Reply #27 on: 3 May 2019, 03:27 am »
Tubes are better, that's why..!!

 :? :lol: 8)

audioengr

Re: WHY do tube preamps sound different than Solid State?
« Reply #28 on: 3 May 2019, 04:10 am »
Tubes are not affected by local heating effects like transistors.  Transistors also don't behave the same with small signals versus large signals. Their bandwidth and linearity is often different for small versus large signals.

Since tubes work off high voltage, the voltage range of the signal is usually a small percentage of the plate voltage.  This make tubes inherently more linear.  Their bandwidth is mostly identical for small and large signals.  Transistors use almost their entire voltage range for the signal voltage.

Steve N.

« Last Edit: 3 May 2019, 04:19 pm by audioengr »

Naimnut

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Re: WHY do tube preamps sound different than Solid State?
« Reply #29 on: 8 May 2019, 03:03 am »
Hey you guys -
Thanks for continuing to share such useful information, observations and comments on this thread. Based on everything I've read on the various fora, I'm strongly leaning towards a Supratek or Don Sachs preamp. Both sound like what I'm looking for.

bladesmith

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Re: WHY do tube preamps sound different than Solid State?
« Reply #30 on: 8 May 2019, 08:05 am »
Another advantage I like about tube
equipment, that I never realized before.
You can change the dynamics of your
Soundstage, Of course..  but, I recently
moved my equipment into a much
smaller room. And changing tubes now,
Means a lot more. Means adjusting the dynamics , with
Different tubes to help fit the room size..
I never heard anyone mention this advantage before,  and I've never had to use tubes this way. But, its works.
"OB speakers,  and a little tube equipment,  sounds
Amazing..."

Just saying... :popcorn:

rollo

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Re: WHY do tube preamps sound different than Solid State?
« Reply #31 on: 9 May 2019, 07:14 pm »
  All great input but you will never know until you hear both types in your system period end of story. Opinions are just that. LISTEN yourself.

charles

Tyson

Re: WHY do tube preamps sound different than Solid State?
« Reply #32 on: 9 May 2019, 08:08 pm »
Another advantage I like about tube
equipment, that I never realized before.
You can change the dynamics of your
Soundstage, Of course..  but, I recently
moved my equipment into a much
smaller room. And changing tubes now,
Means a lot more. Means adjusting the dynamics , with
Different tubes to help fit the room size..
I never heard anyone mention this advantage before,  and I've never had to use tubes this way. But, its works.
"OB speakers,  and a little tube equipment,  sounds
Amazing..."

Just saying... :popcorn:

Agreed!  Some amps/preamps can also roll different rectifiers too.  For example with my Dennis Had Inspire MB12 monoblocks, I can use a 5ar4, 5R4, 5V5, 5Y3, or a Type 80 (with adapter), this changes the voltage getting to the rest of the circuit and definitely has an affect on dynamics.  However, this type of rectifier rolling is very unusual, most tube circuits CANNOT step down a 5AR4 for anything lower voltage, and vice versa.  So unless your manufacturer specifically says you can do it, don't even try it. 

But even if you're rolling just a single type of rectifier, it makes a difference.  Going from an old stock Mullard 5AR4 to a new stock Gold Lion 5AR4 (GZ34), makes a difference.  Which just gives more ability to tailor the sound to your room and your preferences.  Love that about tubes.

OzarkTom

Re: WHY do tube preamps sound different than Solid State?
« Reply #33 on: 10 May 2019, 12:46 am »
I prefer tube preamps over SS, but passive can sound even better at very cheap prices if it will drive your system.

Early B.

Re: WHY do tube preamps sound different than Solid State?
« Reply #34 on: 10 May 2019, 02:34 pm »
The good thing about tubes is that they can significantly alter the sound. The bad thing about tubes is that they can significantly alter the sound. 

audioengr

Re: WHY do tube preamps sound different than Solid State?
« Reply #35 on: 10 May 2019, 04:53 pm »
The good thing about tubes is that they can significantly alter the sound. The bad thing about tubes is that they can significantly alter the sound.

Depends entirely on the circuit design and power subsystem.  My tube SET monoblocks sound like SS only better.

Steve N.

FullRangeMan

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Re: WHY do tube preamps sound different than Solid State?
« Reply #36 on: 10 May 2019, 07:17 pm »
1. I've read comments to the effect that "as you approach the state of the art, solid state and tube equipment begins to sound very similar".
Cant say its good or bad, however on the other side of low priced equip, tube amps are always better sound than SS imo.
2. I've read that tube equipment tends to generate more even-ordered harmonic distortion. Does this mean that distortion in a tube preamp can cause the sound to come across as "richer" and "fatter"?
Correct, this is opinion also.
3. I've read with interest Roger Sanders excellent white paper on tubes vs. solid state, and his comments make sense, for power amps. But what about preamps? Do preamps clip?
In the 1990s after replace a 8Ω 92dB by a 4Ω 88dB speaker after a some weeks my preamp blew a diode when running the same power amp.

bladesmith

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Re: WHY do tube preamps sound different than Solid State?
« Reply #37 on: 10 May 2019, 07:35 pm »
The good thing about tubes is that they can significantly alter the sound. The bad thing about tubes is that they can significantly alter the sound.

😎👊 :popcorn:

Thank you for explaining that so perfectly..friend..

Blade..

rollo

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Re: WHY do tube preamps sound different than Solid State?
« Reply #38 on: 10 May 2019, 07:47 pm »
They sound different because they are different approaches. The preamp or any other component should not have a SS or tubed character. Should add as close to zero coloration as possible. Examples of color are;  bright, warm, dry, dark, sweet or hard. Music should flow with a linear presentation with proper tonality and harmonic structure. No part of the frequency range should stand out over another.
  Not easy to find as most components have a house sound. So we look for synergy of components to find our satisfaction. That is why I recommend components from one manufacsturer.



charle
 

FullRangeMan

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Re: WHY do tube preamps sound different than Solid State?
« Reply #39 on: 10 May 2019, 08:03 pm »
Worth remember vacuum tubes was invented to reproduce voice and music in movie theaters and transistors was created to commercial and military applications.