SS Sound vs. Tube Sound (for the umpteenth time)

[mep]

He has absorption panels for reflections , not bass traps , so nothing of interest towards your debate ....

Micro-What A.wayne says is true. I have absorption panels and no bass traps. So if that means my room is "untreated," I guess it's untreated. I tried bass traps before, but eventually they would build up so much pressure from all the bass they trapped I would have to let the bass out and then it would blow everything off of my shelves.

 

[opus111]

What I am qualified to discuss is the sonic effect that certain power line devices, dedicated conditioning, grounding schemes, and attention to connection quality, as related to a achieving a lower "noise-floor" within my system ... irrespective of amplifier types.

What you say here about grounding outside equipment boxes (inter-equipment grounding) also goes for grounding within equipment boxes (intra-equipment grounding) in my experience. I've achieved subjectively significant gains from rewiring the insides of my (relatively mid-fi) kit.

One point of interest here between SS and valves. Normally valves use point to point wiring internally, SS generally uses PCBs. It seems to me much easier to get the grounding wrong when using a PCB. With point to point there's not the assumption that a ground is really 'ground' as there does seem to be on the many PCBs I've modified.

 

[mep]

Normally valves use point to point wiring internally, SS generally uses PCBs.

I would dispute that statement. Lots of tube gear uses PCBs and not point-to-point. ARC, VTL, and VAC for starters all use PCBs. My Jadis Defy 7 MKII amp also used a PCB.

 

[opus111]

OK, I stand corrected as my experience of tube gear is clearly more limited than yours, thanks. Did you notice if the gear you mention uses a ground fill?

 

[mep]

OK, I stand corrected as my experience of tube gear is clearly more limited than yours, thanks. Did you notice if the gear you mention uses a ground fill?

I will profess my ignorance and tell you that I don't know what a "ground fill" is.

 

[amirm]

OK, I stand corrected as my experience of tube gear is clearly more limited than yours, thanks. Did you notice if the gear you mention uses a ground fill?

Looks like they don't from my quick googling. This is the VTL:

 

[amirm]

Another view:

 

[opus111]

A ground fill is where there's an area of copper which is filling in the space between other tracks. Software is used nowadays to design PCBs and with a couple of clicks of the mouse you can 'pour' copper into the remaining spaces between tracks. Then the fill is used as a common ground but doesn't have star topology, so you end up with common-impedance ground coupling.

I've attached an image Google found for me - on the left you see the PCB with the bottom side tracks in green, top side in red. On the right after the ground fill (in red) has been added. The fill is on the top side so the underside tracks don't show through it.



I should have talked about the nature of the grounding rather than talking about PCBs earlier, so thanks for your correction. Its not about PCBs per se, its about grounding topology - whether a true star ground is used. PCBs can be used with point-to-point topology too but its impossible to have a ground fill when using point to point wiring. I'd hazard that the products you've seen with both valves and PCBs don't use ground fills, they use point to point topology on PCBs. But I'm open to correction on this too

 

[opus111]

Looks like they don't form my quick googling.

Thanks Amir - looks like they don't, I agree. So they are using point to point wiring, but on PCBs. Best of both worlds.

Now l very much doubt that Google can find a digital product that uses point to point wiring on PCBs

 

[microstrip]

Thanks Amir - looks like they don't, I agree. So they are using point to point wiring, but on PCBs. Best of both worlds.

IMHO Point to point wiring means wiring using terminal strips or similar, but no PCB. As soon as equipment uses PCB there is no point to point wiring.

Many Jadis amplifiers use point to point wiring for the amplifier circuits and PCBs for the power supplies. Atmasphere also use point to point wiring - my MA2 has forty separate long wires connecting the the power tubes cathode and anodes to the power supply and the speaker terminals. The old MC275s were built using point to point wiring, modern versions use a PCB - it is why the mint old ones reach used prices around three times higher than recent ones.

Also I would not expect PCBs for tube circuits to have ground fills - tube circuits usually have high impedance and ground fills increase significantly capacitance, reducing the bandwidth.

You can get plenty of information at Wikipedia:
http://en.wikipedia.org/wiki/Point-to-point_construction

 

[opus111]

IMHO Point to point wiring means wiring using terminal strips or similar, but no PCB. As soon as use a PCB there is no point to point wiring.

Perhaps my terminology here is non-standard, hence the confusion. I'm clear in my own mind though - in this context by point to point I'm referring to the topology not the physical implementation of that.

Many Jadis amplifiers use point to point wiring for the amplifier circuits and PCBs for the power supplies. Atmasphere also use point to point wiring. My MA2 has forty separate long wires connecting the the power tubes cathode and anodes to the power supply and the speaker terminals.

Forty separate wires? I wonder why they do that? If they want separate wires there's always litz. Or are there 20 valves involved here?

Also I would not expect PCBs for tube circuits to have ground fills - tube circuits usually have high impedance and ground fills increase significantly capacitance, reducing the bandwidth.

Yes, but more capacitance in SS can only reduce the bandwidth too. Admittedly the effect is less because the impedances are lower. So presumably designers do feel there's some advantage from using it in SS. Perhaps tube designers never got into the habit of using it, coming as they do from physical point to point? Rather like the first car designers made cars to look like the horse drawn carts they replaced.

 

[A.wayne]

http://www.dwfearn.com/tubes_vs_transistors.html

 

[MylesBAstor]

http://www.dwfearn.com/tubes_vs_transistors.html

That paper and more about tube electronics can also be found in the now long OOP Understanding Tube Electronics by the late Harvey Rosenberg (1984).

 

[DonH50]

Hmmm... Both tubes and SS generate odd and even harmonics. The harmonic structure is probably determined more by design and biasing than device; although there are intrinsic differences. Expanding the series for each device, you'll find bipolar transistors have an exponential characteristic, and tubes factorial, meaning fundamentally tubes have lower distortion. Ideal FETs have only 2nd-order distortion, but real FETs exhibit higher-order products that trend toward exponential when running at high power. In practice, tube preamps often have distortion comparable to SS, while tube power amps have much more, limited primarily by the output transformer (I think). Tube amplifiers typically have much (orders of magnitude) higher output impedance, making them more sensitive to the load (that would be your speakers).

Tubes also (usually) have less gain and higher noise, are not as stable over temperature and supply voltage, and of course are much more sensitive to vibration. Tubes often have much higher voltage headroom. Transistor circuits are often differential, which tends to cancel even harmonics, whilst most tube circuits are (or were, I have not looked in a while) single-ended and thus exhibited more even-order harmonics. That means in many tube circuits second harmonic distortion dominates, while in transistors third-order. Many attribute tube's more pleasing sound to this facet of tube amplifier design. It would be interesting to tweak some of my simulations and generate sound files so people could hear the difference. Another facet in tube amplifiers is that tube circuits tend to clip more "softly" than transistor designs for a variety of reasons.

Tube circuits often have less global feedback than transistor circuits; I am not sure exactly how much audible difference this makes. I am well aware of the claims, less sure of the reality; a lot of amplifiers of either type appear to have feedback factors in the 20 dB or less range, but that is a foggy memory of some analysis done decades ago so I could be way off. A lot depends upon the topology of the gain stages, natch.

I dunno', I miss the sound of my tube gear but know by and large it was much less accurate than my SS gear, especially the power amps; I measured around 0.5% to 1% from my ARC D-79 driving my Magnepans, IIRC it was 5% or more driving a pair of B&W 801s. Again IIRC the Krell and ML I had for comparison were well under 0.05% at the same SPL level. In contrast, I measured the THD of my SP3a1 (tube preamp) at one time and it was vanishingly low, well under 0.005% at 2 Vrms output.

IMO, circuit topology accounts for much of the tube vs. SS sound in preamps, and output impedance much of the difference for power amps. I built a differential tube preamp once that was criticized for being too SS, and a single-ended transistor preamp people thought had tubes in it.

Random thoughts - Don

 

[treitz3]

Nice post, DonH50.

Tom

 

[MylesBAstor]

Tubes often have much higher voltage headroom.

Dan D'Agostino once told me one area that he admired most about tube amplifiers and tried to emulate in his designs were their voltage swings.

 

[microstrip]

(...) IMO, circuit topology accounts for much of the tube vs. SS sound in preamps, and output impedance much of the difference for power amps. I built a differential tube preamp once that was criticized for being too SS, and a single-ended transistor preamp people thought had tubes in it.

Random thoughts - Don

Excellent summary. May be we can consider that tubes are large, expensive and generate a lot of heat; transistors are small, inexpensive and efficient - these practical factors also favor simple circuits with few components in tube designs and complicated circuits with many transistors in SS designs.

Some designers enjoy breaking my previous rule - just for example, Ralph Karsteen designs a differential preamplier with many tubes and Nelson Pass has designed SS amplifiers with few components.

 

[FrantzM]

Nice post, DonH50.

Tom

+1

 

[valkyrie]

Hmmm... Both tubes and SS generate odd and even harmonics. The harmonic structure is probably determined more by design and biasing than device; although there are intrinsic differences. Expanding the series for each device, you'll find bipolar transistors have an exponential characteristic, and tubes factorial, meaning fundamentally tubes have lower distortion.

Oh - sorry Don but a factorial characteristic expands to much larger values, much more quickly as "n" increases than ANY exponential series. This is a basic fact of complexity analysis in terms of defining problem limits. If in fact your "expansion of the series" for each device does yield a "exponential expansion" for solid state while tubes provide a factorial expansion then such would indicate ABSOLUTELY that the tubes are much higher in distortion. Which btw, they in fact ARE.

The real argument for employing tubes is NOT their accuracy as amplification devices - for they are not extremely accurate in a 10 octave bandwidth amplifier especially when the very non-linear coupling transformers are employed. However tubes do seem to produce a sound that human hearing (in all its glorious non-linear and completely misunderstood behavior) enjoys greatly. So the purpose of a sound system - regardless of cost - is ultimately human enjoyment. So rather than argue about the "accuracy" of a "hollow state" device vis a vi its solid state brethren it would seem far more appropriate for euphonic tube lovers to praise the characteristics of the bloated, ringy sound that tubes provide.

Something that I learned many years ago about transformers and their characteristics is that transformers are very non-linear depending on whether the field is being discharged or charged (collapsing or expanding the field). This learning was done during development of software for a certain type of missile that used a YIG (Yttrium-Iron-Garnet) oscillator - this particular crystal would oscillate with a frequency that was proportional to the B (field density) of a set of coils surrounding the crystal - compact little device about as large as the smaller (B4 I think) C ration cans. What we found was that to tune the oscillator "up" (or increase field density) in frequency was an order of magnitude faster than tuning the frequency down (decreasing field strength). In fact to "down tune" we had to create timing loops that would provide us with the "wait" factors necessary. In fact no coil (be it transformer or choke) is linear in terms of this charge/discharge phenomena.

Of course the "tube" types never mention this behavior - when in fact it is exactly this non-linearity that provides a tube amplifier with its "soggy, ringing" sound. But this gets, shall we say, glossed over in glowing descriptions of "sustains" and a "full sound".

I often hear so-called "high end" systems which generally in this era comprise a set of screechy, lean, bright, brittle speakers (sometimes costing as much as a ordinary house). This "high end" system is then coupled to soft, bloated and ringing tube amps and fed a generous diet of rolled-off vinyl to calm the result down to something approaching listenable. For if you play digital on this monstrosity (expensive monstrosity but still a monstrosity) it will take the tartar off your teeth at 10 paces.

Geez guys - accuracy? You expect accuracy from an active device that starts decaying the moment power is supplied? You expect accuracy from an amplifier that has to rely on huge piles of windings to couple to a real world load?

Yes you may get a much more enjoyable sound from your hollow state wonders - no question there. But it is NOT ABOUT ACCURACY.

 

[MylesBAstor]

Hmmm... Both tubes and SS generate odd and even harmonics. The harmonic structure is probably determined more by design and biasing than device; although there are intrinsic differences. Expanding the series for each device, you'll find bipolar transistors have an exponential characteristic, and tubes factorial, meaning fundamentally tubes have lower distortion.

Oh - sorry Don but a factorial characteristic expands to much larger values, much more quickly as "n" increases than ANY exponential series. This is a basic fact of complexity analysis in terms of defining problem limits. If in fact your "expansion of the series" for each device does yield a "exponential expansion" for solid state while tubes provide a factorial expansion then such would indicate ABSOLUTELY that the tubes are much higher in distortion. Which btw, they in fact ARE.

The real argument for employing tubes is NOT their accuracy as amplification devices - for they are not extremely accurate in a 10 octave bandwidth amplifier especially when the very non-linear coupling transformers are employed. However tubes do seem to produce a sound that human hearing (in all its glorious non-linear and completely misunderstood behavior) enjoys greatly. So the purpose of a sound system - regardless of cost - is ultimately human enjoyment. So rather than argue about the "accuracy" of a "hollow state" device vis a vi its solid state brethren it would seem far more appropriate for euphonic tube lovers to praise the characteristics of the bloated, ringy sound that tubes provide.

Something that I learned many years ago about transformers and their characteristics is that transformers are very non-linear depending on whether the field is being discharged or charged (collapsing or expanding the field). This learning was done during development of software for a certain type of missile that used a YIG (Yttrium-Iron-Garnet) oscillator - this particular crystal would oscillate with a frequency that was proportional to the B (field density) of a set of coils surrounding the crystal - compact little device about as large as the smaller (B4 I think) C ration cans. What we found was that to tune the oscillator "up" (or increase field density) in frequency was an order of magnitude faster than tuning the frequency down (decreasing field strength). In fact to "down tune" we had to create timing loops that would provide us with the "wait" factors necessary. In fact no coil (be it transformer or choke) is linear in terms of this charge/discharge phenomena.

Of course the "tube" types never mention this behavior - when in fact it is exactly this non-linearity that provides a tube amplifier with its "soggy, ringing" sound. But this gets, shall we say, glossed over in glowing descriptions of "sustains" and a "full sound".

I often hear so-called "high end" systems which generally in this era comprise a set of screechy, lean, bright, brittle speakers (sometimes costing as much as a ordinary house). This "high end" system is then coupled to soft, bloated and ringing tube amps and fed a generous diet of rolled-off vinyl to calm the result down to something approaching listenable. For if you play digital on this monstrosity (expensive monstrosity but still a monstrosity) it will take the tartar off your teeth at 10 paces.

Geez guys - accuracy? You expect accuracy from an active device that starts decaying the moment power is supplied? You expect accuracy from an amplifier that has to rely on huge piles of windings to couple to a real world load?

Yes you may get a much more enjoyable sound from your hollow state wonders - no question there. But it is NOT ABOUT ACCURACY.

It's very hard to take this seriously when you make a sweeping comment, "so-called "high end" systems which generally in this era comprise a set of screechy, lean, bright, brittle speakers (sometimes costing as much as a ordinary house)."