[Ultralight]

A bit curious.  For some amps, one should run the amps somewhere in the middle range of their power output for maximum quality.  Is this true for single ended tube (SET) amps?  Say someone has a 98db efficient pair of Omegas, and run at one or two watts, would having a superb 50 watt SET amp be foolhardy?  or would a 50 watt (just for illustration's sake) be inappropriate match? 

Curious.

Thanks!

[mick wolfe]

I run my Omega Omni's(98 db) with a LM 218ia. Rated at 22 watts using 845's. Plenty of headroom and a superb sense of ease. Plus this power to efficiency ratio gets you closer to the dynamics of live music. If you like the flavor of the output tube, the additional power is all positive to my ear. If I were fortunate enough to afford an amp upgrade in the future, I'd strongly consider the LM 508ia.... which has double the power of the 218ia. One final bonus in regard to a higher powered amp is that it lets you experiment with a MUCH wider variety of speakers if you choose.

[seikosha]

I believe that with some amps, distortion is actually higher when the amp is putting out very little power.  However, those specs/measurements aren't readily available.

Historically I've run my Omegas (3xrs and SAM) with a Decware Mini Torii and UFO Zen.  Recently I picked up some Quicksilver Horn Monos which are 25 watt amp monoblocks designed for high efficiency speakers; it's the first amp I've had in years that doesn't make me miss my Zen.

[Early B.]

While I don't own Omegas, I do have a pair of 98dB speakers. I use a solid state amp that puts out 300 wpc. A few years ago, a buddy of mine was using high efficiency speakers with a Decware amp that output 18wpc, I believe. Sounded OK, but then I put my amp on his system and it came alive. Lesson learned -- I don't get hung up on the specs because they don't tell the whole story. 

[Docere]

A bit curious.  For some amps, one should run the amps somewhere in the middle range of their power output for maximum quality.  Is this true for single ended tube (SET) amps?  Say someone has a 98db efficient pair of Omegas, and run at one or two watts, would having a superb 50 watt SET amp be foolhardy?  or would a 50 watt (just for illustration's sake) be inappropriate match? 

SET distortion increases with output level: play quietly, the distortion is lower; turn it up and the distortion increases. WRT Omegas, they are by all accounts I have read, easy to drive and their bass alignments appear to suit a wide range of source impedances. A 50W SET amp is unlikely to be an issue; it should run at low distortion (may or may not matter to you), but it will burn up power and you will have to be careful with the volume control.

For sonic and practical reasons, my preference for Omegas would be a lower power SET with quality power supply and components... but that does not suit everyone. Failing that, running additional SET power as you and others have suggested would be a valid option.

Cheers.

[Canada Rob]

I have a customer who just bought a UFO2 from me to replace a Line Magnetic LM518 and he is thus far very happy with the Decware.  His speakers are SAMs on Skylan 4 post stands.

[Beatlebum]

Just received my Dennis Had Inspire Fire Bottle PSE amplifier yesterday. I had a Blue Alps volume control added as I don't need a preamplifier (other than my Herron VTPH-2 phonostage). My PSE was voiced and furnished with KT66 output tubes. My Omega's sound amazing with this amplifier!

[Ultralight]

I have a customer who just bought a UFO2 from me to replace a Line Magnetic LM518 and he is thus far very happy with the Decware.  His speakers are SAMs on Skylan 4 post stands.

Thanks everyone for the response.  Learned something.

Mick, let me know if you get the 508. Love to hear your comments.

Rob, so you mean your client preferred the UFO2 over the 518?  Assuming that the 518 is using quality tubes, that's remarkable as the 518 is an excellent amp.

Thanks.

[Canada Rob]

Beatlebum,

What a beautiful looking system.  Very tastefully done. 

[Canada Rob]

Thanks everyone for the response.  Learned something.

Mick, let me know if you get the 508. Love to hear your comments.

Rob, so you mean your client preferred the UFO2 over the 518?  Assuming that the 518 is using quality tubes, that's remarkable as the 518 is an excellent amp.

Thanks.

It has a stepped attenuator and $405USD worth of high end V-Caps.  They are not on the Decware website but can be ordered.  To my ear, UFO or not, the V-Caps make a stunning sounding Zen.  Going back to 2009 I've been ordering V-Caps in the all Zens I've brought into my place.

[jorgen]

Im keen to hear what kind of Decware amp you are referring to

[gregfisk]

Beatlebum, Very nice looking system indeed!

What type of wood is on your turntable and what kind of wood is on the speakers? I'm building an audio rack and would love to use that veneer for the shelves, the posts will be 2" square brushed stainless.

Now, back to your regular programming

Thanks,

Greg

[maxima95]

...  Recently I picked up some Quicksilver Horn Monos which are 25 watt amp monoblocks designed for high efficiency speakers; it's the first amp I've had in years that doesn't make me miss my Zen.

Are you using the EL-34's, or have you tried another output tube that you prefer?

[seikosha]

Still using the EL-34s.  I'm going to live with these for awhile before I start rolling other tube types.

[DaveC113]

It has a stepped attenuator and $405USD worth of high end V-Caps.  They are not on the Decware website but can be ordered.  To my ear, UFO or not, the V-Caps make a stunning sounding Zen.  Going back to 2009 I've been ordering V-Caps in the all Zens I've brought into my place.

IMO, they are key parts... If you can get Steve to use Clarity TC caps in the last stage of the power supply that makes an amazing difference vs electrolytics.

I think the power issue is a personal decision, big and high quality SET amps are usually 3-stage and cost a lot more vs lower power 2-stage amps if the quality of parts are the same. I'd have built one by now if price wasn't a HUGE issue. I mean, I can't have an increase in power and a decrease in sound quality, so I was looking at many thousands of $ in parts, and some might say an intrinsic decrease in sq due to the 3rd stage, but with good parts this is minimized.

What you gain with more power is more SPL before clipping, as the Omega speakers can handle more than a few watts. How many depends on the music, an RS5 can actually handle a lot of watts, like 50+ if it doesn't have to handle anything under 400 Hz. With bass heavy music run full-range maybe as little as 5-10 watts. The larger drivers can handle more power, so especially with the 1.5 way speakers I can definitely see wanting a larger amp. It just depends if you want the SPLs. If you frequently run your small amp near it's limits then I'd definitely consider a more powerful amp.

Another option to achieve higher SPL vs a larger amp is to limit low-end frequency response of the speaker, there's a few ways to do that... Even a very low xo around 60 Hz makes a big difference and might result in clearer sounding speakers, I say might because depending on how it's done it's likely to result in detrimental side effects. With most tube pres and SET amps you can usually change a coupling/output cap value and get a 1st order roll-off, speaker level cap, DSP, etc... 

[roscoe65]

IMO, they are key parts... If you can get Steve to use Clarity TC caps in the last stage of the power supply that makes an amazing difference vs electrolytics.

I think the power issue is a personal decision, big and high quality SET amps are usually 3-stage and cost a lot more vs lower power 2-stage amps if the quality of parts are the same. I'd have built one by now if price wasn't a HUGE issue. I mean, I can't have an increase in power and a decrease in sound quality, so I was looking at many thousands of $ in parts, and some might say an intrinsic decrease in sq due to the 3rd stage, but with good parts this is minimized.

What you gain with more power is more SPL before clipping, as the Omega speakers can handle more than a few watts. How many depends on the music, an RS5 can actually handle a lot of watts, like 50+ if it doesn't have to handle anything under 400 Hz. With bass heavy music run full-range maybe as little as 5-10 watts. The larger drivers can handle more power, so especially with the 1.5 way speakers I can definitely see wanting a larger amp. It just depends if you want the SPLs. If you frequently run your small amp near it's limits then I'd definitely consider a more powerful amp.

Another option to achieve higher SPL vs a larger amp is to limit low-end frequency response of the speaker, there's a few ways to do that... Even a very low xo around 60 Hz makes a big difference and might result in clearer sounding speakers, I say might because depending on how it's done it's likely to result in detrimental side effects. With most tube pres and SET amps you can usually change a coupling/output cap value and get a 1st order roll-off, speaker level cap, DSP, etc...

Interesting comments Dave.

Of note is not only the power that a SET puts out but its gain.  I have a 6SL7/421A amp that puts out 4.5 watts with 0.6 volts input.  It has only two stages but each one is relatively high gain.  On the other hand, I have a 20wpc Inspire PSE amp with 6SN7/SEP that has less gain and "needs" a preamp to reach full output.  The accompanying preamp offers 10-14 dB of gain.  IIRC, your preamp and amps function as an integrated, with the Aikido driver stage built into your preamp.

WRT the power handling of the Omega drivers, I agree.  I do wonder exactly how loud a speaker would be putting 50 watts into an RS5 above 400hz.  It seems analogous to a JBL L100, with the LE5 5" midrange coming in at about 2,500 hz, almost acting like a tweeter.  Doubling up the RS5's below 500hz would probably let them take about 30 watts steady state.  Even though this translates to 100-112dB max output, I don't think we would get the visceral bass impact we would want.  For that, I would expect the need for a much larger driver and/or active bass reinforcement.

I have a pair of Altec 414A's in 614 cabinets.  This 99dB 12" driver still only gets down to about 40hz or so, albeit with great speed and impact.  For really deep bass, I'm convinced we need dedicated bass drivers either crossed over at speaker level or actively crossed over at line level.  I've recently picked up a pair of Rhythmik F8 subwoofers (2 8" drivers per side, each driver by 300 watts) and realize that in my room there is really no substitute to active bass to get the acoustic power below 50hz. 

[DaveC113]

My comments were wrt a 211/845 type SET amp, but there are other options of course that won't cost what a really nice big SET does. To drive those amps requires a driver that has some power so I think they've gotta be 3 stage unless you use some sort of SS assist for the driver.

50 watts for the RS5 is an estimate, but 120 dB peaks at the LP are no problem...    The RS5's efficiency is boosted 6 dBish by the waveguide too, it plays strong to 15 kHz then a Fostex T500AmkII fills in. 

Agreed on the bass, I'm using Acoustic Elegance TD15H+ in a front ported cabinet, run active. People often use the 15M for it's higher efficiency and ability to play into the midrange but the 15H+ is spectacular, it shames the 15M under 250 Hz or so... For reference I also have Pioneer S-1EX and the AE woofers crush them, it's not even close. Way less distortion measured down low too. With 32mm xmax you have overhead for eq if needed.

[roscoe65]

Yeah, thr 845/211 triodes actually need the equivalent of a power amp to drive them., typically a 300B or EL34.

Your implementation of the RS5 is interesting.  It reminds me of Bruce Edgar's original Edgarhorn midrange horns in which the JBL LE5 was a preferred cone driver.  Someone on DIYAudio did a similar arrangement with the AE TDM woofer, LE5, and Fostex supertweeters.  I would imagine the RS5 would be better behaved on the top but would maybe need the supertweeter to come in a little earlier.

[Beatlebum]

Beatlebum, Very nice looking system indeed!

What type of wood is on your turntable and what kind of wood is on the speakers? I'm building an audio rack and would love to use that veneer for the shelves, the posts will be 2" square brushed stainless.

Now, back to your regular programming

Thanks,

Greg

Hey Greg,

The finish is called Macassar Ebony.

Tim

[Beatlebum]

Beatlebum,

What a beautiful looking system.  Very tastefully done. 

Thank you Rob!