SEX 3.0 Amp vrs Stereomour II 2A3 which gives warmer sound

[johne]

I have a 7 to 8 year old SEX Amp and Fourplay preamp setup.  I want to build replacements.  I am trying to decide between the new SEX 3.0 Amp kit or the Stereomour II 2A3 kit.

I am looking for that warm tube sound that I experienced as a kid.  As a boy I was in love with the tube radio I had by my bed.  Later I came to tube equipment because transister equipment never souednd at all warm and likable to me.  My question is which of the two Amps above will give me that warm sound? 

And should I just run my system through the Amps and not use a preamp or build a pre-amp such as the Submissive volume/source Control kit or the Smash DHT preamp kit?

[Paul Joppa]

A part of the answer depends on how efficient your speakers are, and how loud you like to listen.

Does the SEX amp you are currently using provide adequate warmth in the midrange? The newer amps have more, and cleaner, deep-bass capability than the SEX 2.0 which I believe is what you have. The midrange and most of the treble will be comparable with the SEX 3.0.

[johne]

Paul,

Thanks for your answer. 

I have two HornShoppe speakers which are single driver 4.5" cones, with folded horn cabinets.  They are spec.ed to peak at 98-100 db. I also have a Dayton Audio sub-woofer setup comprised of 2 sub-woofer amps and two speaker boxes.  I play my music usually not loud and definitely not super loud.

I am assuming by your answer that I should look toward building a new SEX 3.0 Amp?

Additional Question:  To get more sound warmth should I play through a Pre-Amp or just go straight through the SEX Amp?

johne

johne

[Paul Birkeland]

For loudspeakers, the only reason I would ever use the SEX over the Stereomour would be for something that's more than 110dB efficient.   If you plan to use both speakers and headphones, the SEX is a great choice.

Otherwise, the Stereomour is the better sounding speaker amp by far, and will offer you some power headroom that certainly won't hurt with the FE126. 

If you want to experiment with warmth generated by higher THD, you can try running your 8 Ohm speakers with the amp setup for 16 Ohms.  It's also possible (though not advisable) to raise THD by removing the C4S loads and using plate loading resistors.  We have found the improvement to be so significant that including C4S loads with the kit goes all the way back to the Paramour days.

-PB

[Paul Joppa]

I totally agree with PB, who was posting at the same time. I'll go ahead with my post anyhow, as a  different perspective on the same issues:

====================================

I am hesitant to recommend anything, because "warmth" does not translate easily to measurable effects or design details. We can all hear it, but it's not clear we are hearing the same thing even if we are using the same words to describe it.

The most nearly measurable effect is distortion, specifically second order distortion. To many people, the right amount of second harmonic distortion sounds warm. (Too much just sounds muddy.) Second harmonic distortion in SET amps increases with signal level, reaching a maximum at full power. So an amp with more headroom will sound less distorted, all other things being equal. And the SEX amp has a bit more distortion at full power than the Stereomour, because the 6DN7 is not as linear as a 2A3.

Amp output impedance (damping) also plays a role. The SEX amp has slightly greater output impedance (a lower damping factor) than Stereomour, so its effect on speaker bass tuning is stronger. This will often exacerbate some bass resonances, lending a completely different form of "warmth". But this is highly variable depending on the speaker.

The more gain stages you have, the greater the high-order distortions become. That's why in theory a passive preamp is better. But many people seem to hear improvements with a good preamp, so there must be other things going on that I for one do not understand (yet). So - again - use your ears; there is no better answer than "try it and see".