Tube Amp soundstage


I hope everyone is safe and healthy during these strange times. I wondering if someone could explain to me the reason my tube amp has a deeper soundstage than my SS amps? Two years back I built an Elekit 8200 which puts out around 8-10w/c in ultra linear mode, depending on the power tubes. I usually run KT88’s or 6L6’s, and less often EL34’s. It powers a pair of Tekton Enzo 2.7’s which are quite efficient at a claimed 98db. The SS amps I’ve used with these speakers include a vintage NAD 35w receiver, a Musical Fidelity m3si @ 85w, a Rogue Sphinx @ 100w and a Hegel H80. Now granted, non of these amps are what I would consider high end audio, but no matter what, the little tube amp always seems to have a deeper, more 3-D soundstage and the SS amps sound a little flatter. Same source, same DAC, same speakers and cables. There are things I appreciate about the SS sound, such as tighter, better defined bass and an effortless ability to play louder (which I do less and less), but every time I rotate the little tube amp back in, I hear a slightly more organic sound and that deeper soundstage.
dtapo
MC says "Designers never came up in my post at all. Now you’re pretending it did. Crazy."

Look...the inconvenient truth is that when talking about tubes vs SS You CANNOT separate the equipment from the design if you want to discuss the harmonics that are produced. Period!

Any device, tube or transistor, will display the same basic character with respect to odd or even harmonic distortions depending on how it is used. In a single ended design there is one amplifying device covering the entire musical signal while in a push pull or complimentary design there are two: one for one half of the signal and the other the remaining half. The simple fact that second order harmonics are louder than third order harmonics in most any device dominates the single ended approach while push pull and complimentary designs cancel these distortions by the very nature of their operation. What this means is that any device, tube or transistor, will display the same basic character with respect to odd or even harmonic distortions depending on how it is used.

MC makes these erroneous claims about even harmonics being attributable to the tubes themselves...and SS gear (w/o any design considerations) produces more odd harmonics. This is just plain wrong regardless of how MC chooses to spin it. It’s not about a tube vs a transistor - it’s all about implementation...yes, the friggin’ design!

From a practical standpoint most SS designs are not single-ended and lend themselves to producing odd harmonics so MC falls into the trap of believing it must be due to the gear using SS components instead of valves. Wrong. So very wrong. This isn’t word play MC, this isn’t a game, this isn’t dastardly use of a Cusinart...this is just you not understanding something.

The Sylvania 6L6 is very nice indeed.

Ralph post is a Phd,

of course SS with a tube front end SS output , liquid cooling, no emiter resistors, etc and a few other tricks can sound incredible, see Vandersteen M5, M7
of course soundstage depends on preserving those subtle time and phase related cues as well as not burying them in whatever flavor of distortion you may prefer.... lots of feedback kills image depth, easy test with an SPL meter, genius ( mindful designer ) Roger Modjeski designed RM-9 with variable feedback :-) ears are required
@dtapo
You may have already answered your own question, comparing first hand. Trust your ears. Maybe there is some magic in the distortion and 2nd and 3rd order harmonics.   

Gotta ask oneself why many of the high-end class A solid state designers and amp builders continue to try and build circuits and test various output transistor types to try and make their amps sound like valve tube amps. Getting closer, not fully 3D or as layered yet.   
Ralph’s post is perfect to demonstrate how the design and implementation are applied to get the desired outcome from an amp. Designers of both tubes and transistors make choices and tradeoffs to achieve their goals. Tubes have a relatively high output impedance and are not easily capable of driving a loudspeaker directly – where the opposite is true for transistors. This is why most tube power amplifiers have large output transformers and transistor amplifiers do not. The transformer addresses the tube output issue but certainly has sonic drawbacks. This is why a number of Ralph’s designs "fix" this problem by creating output transformerless amplifiers. It’s all about the implementation.
lots of feedback kills image depth, easy test with an SPL meter, genius ( mindful designer ) Roger Modjeski designed RM-9 with variable feedback :-) ears are required
A bit of a correction here- feedback, properly implemented, does not kill image depth. **Improperly** implemented feedback does that and other things (brightness, harshness) as well.


For feedback to really do its job, it needs to be really a lot. Like over 35dB or so. Less than that and you have those problems above. One thing about sound stage BTW- to do it right you need zero phase shift in the audio band. This is why in our tube amps we've had 2Hz to 200KHz bandwidth, since you need to go 1/10x or 10x the cutoff frequency to prevent phase shift components in the passband - in this case the audio band of 20Hz to 20KHz.

But you can get around this with a class D implementation, since you can apply a lot of feedback with class D- so much that the amp goes into oscillation. The trick is to use the oscillation as the switching frequency. Then the amp might only have good bandwidth to 20KHz, but it can have so much feedback that its able to correct for phase shift that might otherwise be present on account of the filter at the output of the amp. Class D distortion is caused by errors in the the encoding and by something called 'dead time' (topic for another thread) but both tend to cause lower ordered harmonics. Because of this, a class D amp with a lot of feedback can have as much depth and stage width as a tube amplifier.