Tube amps for Revelations

Double Ugly · « **Reply #20 on:** 30 Mar 2008, 10:11 pm »

Quote from: SP Pres on 30 Mar 2008, 09:24 pm

If you want to go to Carnegie Hall without ever leaving your listening chair, then get the Revs or something as close to them as you can find.

That's a fact! You feed them well and you are there!

All standard caveats apply: YMMV, IMHO, to my ears, in my system, etc. etc..

Springbok10 · « **Reply #21 on:** 3 Apr 2008, 03:11 am »

So I just came home from a trip and was gung-ho to order the Revs over the Coincident Total Reference that I found used (flat 8 ohm impedance curve, 97 db sensitive), but thought that I have to heed what Ralph Karsten says about his OTLs liking 8 ohms so much more (plus the fact that I don't think any current Rev owner is using tubes or are they?), and carried my Mark-Daniel Maximus from my second system, upstairs and hooked them up to the Atmaspheres. Oh, Oh. Compared with the sound downstairs, biamped with 2 Moscode 401 HRs, 300 WPC into 4 ohms, they sounded b-a-a-ad - mushy bass, incoherent lower midrange and even fragmented at 90-plus dbs (metered). Recordings: Genius Loves Company, Eleanor Macay - both brilliant recordings - So I am in a quandary - taking this kind of expensive leap with this taste of A-S/4 ohm speaker in my ears, is, at the least,....dicey.........
So, if anyone is driving their Revs with an OTL amp and they live anywhere with a few hours of Connecticut, I'll come listen, (with his/her permission, of course!!)
The Maximus has a nominal impedance of 4 ohms, lowest 2.8 ohms with average efficiency being 85 db/2.83V/1m.
I realise that one's system should be built around the speakers, and I hear such great things about the Revs from all of you (and even on the GR-Research forum), that I realise that I could change my amps to a hybrid like the Moscodes. But I love the A-S amps and have built the room around the 7ft coffin they reside in.
Comments?

Double Ugly · « **Reply #22 on:** 3 Apr 2008, 04:42 am »

A very nice gentleman in the city owned a pair, but unfortunately he took ill and had to sell them a few months back.

Karsten (Denmark SP Tech dealer) might've tried tubes, but it'd be best to discuss his amp adventures directly. You can send him a PM, or an e-mail to info *at* studiosound *dot* dk.

I know you're terribly enamored with the OTLs, but in absence of hearing the Revelations, you can't know how truly good they are. I don't recall hearing them with anything but SS amps, and I've been floored each and every time.

Regardless, I hope you find the information you seek, and best of luck with the decision.

Karsten · « **Reply #23 on:** 3 Apr 2008, 10:10 am »

Springbok,

The M-D speakers are very difficult to drive, much harder than the Revelations. I'm currently evaluating a set of Sapphire here, and they really need some juice to behave.

I have been running my Revelatons with both Berning ZH-270 ZOTL and Joule Electra OTL without any problems whatsoever, so I don't think you would be disappointed at all.

Karsten

Aether Audio · « **Reply #24 on:** 3 Apr 2008, 03:54 pm »

Springbok10,

I don't want to confuse you, but the "2.8-Ohm" spec of the M&Ds doesn't really tell the whole story. Yes... out of the gate that's a pretty low value and the Revs never go that low. But, "the rest of the story" has to do with both sensitivity AND phase angle. 3dB more sensitivity in the speaker makes your amp look like it has twice the output power! Conversely, that means the Revs look like half the power load of the M&Ds. What would the M&Ds sound like if you replaced your 200W/ch. Atmosphere amps with ones of the exact same construction from the same manufacturer, except that now they are 400W/ch.? See my point? That's a huge difference. Add to that the fact that the Revs impedance only goes down to about 3.5-Ohms and you end up almost comparing apples to oranges.

Another big issue is the electrical phase-angle question. This one is fairly complex in nature and would take quite a bit more explaining in order to convey its importance. It all comes down to the fact that "impedance" is a byproduct of the vector sum of two factors - resistance & reactance. Pure resistance is constant regardless of frequency. An 8-Ohm resistor is 8-Ohms at any frequency.

Reactance is totally dependant on frequency. A simple example is that a capacitor of a certain value that exhibits 8-Ohms of reactance at 1KHz will have 16-Ohms of reactance at 500Hz and 4-Ohms at 2KHz. An inductor (coil) will do the same in reverse, i.e. the reactance in "Ohms" will go up as the frequency is increased and go down as the frequency is decreased.

Well, as I said... a speaker's impedance is the result of both resistance and reactance and is therefore complex with regards to changing frequency. In order to REALLY know how hard a given speaker's impedance is to drive, you also need to know the reactance component in degrees of phase as well as the absolute value in Ohms at a given frequency. The question becomes: "What is the electrical phase angle at the point where the M&Ds exhibit their 2.8-Ohm impedance?"

We find in electrical engineering that when the phase angle begins to approach -45 degrees (negative phase angles are the result of capacitance), the speaker's impedance is becoming highly capacitive. Well, a capacitor hooked directly across the output of an amp is the most difficult load that you can possibly have. In fact, I don't recommend that anybody try this as there is a good chance you could blow up your amp.

So... we find that the phase angle (in degrees) at a give impedance value is just as important - if not more so - than the actual "Ohm" rating of the speaker at that frequency. I don't know what the phase angle of the M&Ds are, but I can tell you that the Rev's never exceed -35 degrees at ANY frequency. A difference of 10 degrees may not sound like much, but to an amplifier that's a lot.

The upshot is that compared to the M&Ds, the Revs are a piece of cake to drive. In fact, this is also true when comparing the Revs to our own TP3.0s. So far, we have tried a couple of amps that started to audibly distort when being pushed to higher SPLs on the 3.0s, but when connected to the Revs they seem to have way more power and a total lack of distortion. Like the M&Ds, our TP 3.0s are 85dB sensitivity as well. To a large degree, that example represents what you would likely hear when switching from the M&Ds to the Revelations as well.

Just thought I'd try to help.

Take care,
-Bob

bhobba · « **Reply #25 on:** 3 Apr 2008, 09:59 pm »

Quote from: Karsten on 3 Apr 2008, 10:10 am

The M-D speakers are very difficult to drive, much harder than the Revelations. I'm currently evaluating a set of Sapphire here, and they really need some juice to behave.

They certainly are. Before deciding on the Timepiece mini I investigated them - but gave then away for two reasons. First Danny Richie both measured and pulled one apart and was not happy at all with what he found. Secondly the are devils to drive.
The best advice I have heard is to always bi amp them. I hasten to add that Danny had the exact opposite comments to say about Bobs speakers - I think the words were along the lines of great build and bloody accurate.

Thanks
Bill

konut · « **Reply #26 on:** 3 Apr 2008, 10:57 pm »

Quote from: SP Pres on 3 Apr 2008, 03:54 pm

I don't know what the phase angle of the M&Ds are, but I can tell you that the Rev's never exceed -35 degrees at ANY frequency. A difference of 10 degrees may not sound like much, but to an amplifier that's a lot.

-Bob

Sorry to go off topic, but this begs the question, what is the phase angle of the Minis?

Springbok10 · « **Reply #27 on:** 4 Apr 2008, 04:42 am »

What if I were to bi-amp the Revs with the Atma-Spheres for the HF and either a digital amp (Nuforce, DNA, Bel cantoCanto) for the LF? Would that work? Best of both worlds, or coherence problem with 2 different amps and different output gain, since they would be horizontally bi-amped? I would have to change preamps, since the A-S MP-1 is fully balanced and has only one XLR output.
Bob, Duke, Karsten?????
This may be the answer. Of course I could try the MA-2 first.
Steve Chang had an MA-2 with his Revs. Why did you change, Steve?
Karsten, have you tried ss amps gainst the Bernbing and Joule - if so, what was the difference? When you say you used both Berning and Joule, you meant separately, not bi-amped, right?

Karsten · « **Reply #28 on:** 4 Apr 2008, 02:52 pm »

Springbok,

I have done the bi-amp experiment with OTL and SS based amplifiers as well. It does work but there is some compromise in the coherence.

Frankly speaking I find most of the virtues from the good tube amplifiers in the new generation class-D designs, like NuForce V2 and Spectron, and they do have a much better grip on the speakers, plus of course several practical advantages. You might find it interesting to do an evaluation of these designs. And yes, the Berning and Joule were used seperately.

Karsten

Double Ugly · « **Reply #29 on:** 4 Apr 2008, 04:11 pm »

Hi Springbok,

I can't speak for Steve, and though I haven't received my Revelations yet, I think it's reasonable to assume some similarity between his reasoning and mine.

For frame of reference, I used a pair of Butler Audio Monad monoblocks (hybrid design, 300B direct-coupled to output stage, 110W/Ch @ 8 ohms) with my Timepieces for almost 3 years, but I sold them after hearing the Spectron @ Steve's place last October.

First (and most importantly IMHO), the speakers are as good as your supporting equipment will allow. IOW, if your source is good or better, you don't need tube amps to smooth an edge, provide midrange depth, fill in the soundstage or produce that organic presence we all seek. The speakers do just fine on their own, thankyouverymuch.

Secondly, as is the case with virtually any speaker, the Revelations respond positively to more and better power. Micro- and macro-dynamics are impressive, even with amps producing 'average' power (like my Monads). But when tethered to an amp with more and better power (Spectron MIII SE, McCormack DNA-500), their dynamics are startling by any frame of reference.

Their coherence, tonal accuracy and linearity are world class, but it's the dynamics most notice first. They've been described as having the speed of an electrostatic, but with the dynamics of a jackhammer, and I can't think of a more apt description. (well done, Mike

)

Lastly, the proprietary T-line produces the best, most articulate bass I've ever heard from a speaker or sub. I'm not a bass freak, but like another member here (lonewolfny42), I consider bass the foundation for the rest of the presentation. Aside from the possible rare exception (never say never), SS amps are going to handle the low frequencies better than a pure tube amplifier. Hybrid designs can compete (my Monads were the best LF amps I've heard), but generally speaking, a classic tube design simply can't provide the same measure of control.

Nevertheless, several of us plan on using tubes elsewhere in the system. Yes, I've sold the Monads and their glorious 300Bs, but my Slim Devices Transporter is en route to Dan Wright (ModWright) for his "Truth" modifications. I haven't used a preamp in almost 3 years, but I'm eyeing Dan's LS36.5/PS36.5 combo very closely.

That's the exact set-up ted_b is using with his Revelations, and I doubt you'll find a disparaging word about the results. Frank S. seems awfully happy with the Audio Research Ref 3 preamp and ModWright Transporter he's using with a pair of Continuum 2.5s, and I suspect he'll continue using them if he decides to upgrade to Revelations or Grand Masters.

That's my take, Springbok. I wasn't asked, but since I believe Karsten and Steve are using the same amp as I (Spectron MIII SE), I thought I'd offer. I hope you find it helpful.

Regards,

-Jim

reefrus · « **Reply #30 on:** 4 Apr 2008, 04:22 pm »

Quote from: Springbok10 on 4 Apr 2008, 04:42 am

This may be the answer. Of course I could try the MA-2 first.
Steve Chang had an MA-2 with his Revs. Why did you change, Steve?

Springbok10,

Just make it clear! I used MA-2 II driving the Sound Labs A-1. That was before SP Tech's speakers. I sold them before I discovered the SP Tech TP 2.0.
Atma-Sphere MA-2 still one of my favorite amp and I think it's more than enough power to driving the Revelation III as we discussed on the phone. You don't need to bi-amp at all. You can try but I don't think you need it. Revelations sound better with one amp, it's better intergrated. It's trcicky to mess around with the amp's gain when it's bi-amp.

Steve Chang

Springbok10 · « **Reply #31 on:** 4 Apr 2008, 05:44 pm »

Steve, Sorry I misunderstood you. I thought you drove Revs with the MA-2. I agree that bi-amping is a tough proposition unless it's vertical with identical amps. Thanks for clarifying the MA-2 issue.

Aether Audio · « **Reply #32 on:** 4 Apr 2008, 05:47 pm »

Springbok10,

Actually, I think your idea would make a great starting point. I know Karsten's view on combining amps is somewhat negative, but you must remember... he is a tweak-o nut to the "nth" degree!

I have always thought that in lieu of the "perfect" amplifier, that would be one upgrade path that should yield a significant improvement. Of course, it all depends on the synergy and quality of amplifiers, but I do know that a good solid-state amp and particularly the new digital ones are ideal for maintaining control over the woofers - at least in our designs.

The NuForce (I know for a fact) and Spectron (I highly suspect) both have very high damping factors. That really keeps your woofers from "flopping around" and delivers the fastest, tightest and most realistic bass you're going to find.

The only time you really don't necessarily want an amp with high damping is when the speakers rely on a low damping amp to produce bass. One type of these are "high Q" designs wherein the woofer basically has a weak motor (magnet). If the amp has too much damping it will basically "kill" the bass output. The other type is a very "low Q" design. Those have very strong magnets and typically rely on reflex tuning to get any extension at all. They're usually high sensitivity models that don't go very deep and are often used with SET amps.

All of our designs are "moderate Q" and really benefit from high amplifier damping. Such damping won't kill the extension but it will keep everything fast and tight. If you use an amp with low damping on the Revs they will still be pretty fast and tight because of the t-line loading, but they really excel when the amp has good damping. The drawback with most tube amps is that they often don't offer much in the way of damoping factor. That's why I say combining tube on the highs with SS on the lows could really give you the best of both worlds. But... as Karsten has pinted out, your milage may vary a bit.

On a similar note, NuForce does offer their $1.00 audition deal where you get to try out their amps in your own home for a weekend (or something to that effect). That may just be the ticket for you to find out what works best. Heck, you might find that you like the NuForce better from top to bottom and it would only cost you a buck in the process.

Take care,
-Bob

PS. We could easily provide a means to balance the gain for you... if need be.

mcullinan · « **Reply #33 on:** 4 Apr 2008, 05:53 pm »

Bob,
who knew there were so many things to look at when choosing an amp and a speaker. Why dont more manufacturers mention these point in order to get the best sound out of the plether of combinations out there. That would narrow your choice and certainly make things a bit easier on the buyer. Ehich you just did.

Mike

bhobba · « **Reply #34 on:** 4 Apr 2008, 08:24 pm »

Quote from: mcullinan on 4 Apr 2008, 05:53 pm

who knew there were so many things to look at when choosing an amp and a speaker. Why dont more manufacturers mention these point in order to get the best sound out of the plether of combinations out there. That would narrow your choice and certainly make things a bit easier on the buyer. Ehich you just did.

Just one of the many advantages of buying from a small outfit that gives a personalised service. I know you can get good speakers cheaper than Bob's, but it is hard to get this kind of service at any price.

Thanks
Bill

DeadFan · « **Reply #35 on:** 6 Apr 2008, 10:52 am »

I second that Bill. I have been a "lurker" on AudioCircle for more than 2 years and Bobs integrity, as shown via his posts, shines through like a beacon. It has so impressed me (along with the enthusiasm shown by owners such as Lonewolf and Double Ugly ), that I too have become an SP devotee. As soon as finances (had huge setback with my daughter being badly hurt in "hit n run" accident) allow, I will be purchasing sight unseen and unheard, a fully Mundorfed pair of Revelations.

Bob, never quit "saying how it is" (or at least how you see things). It may turn a few off, but to those who can read between the lines, your honesty will win more fans than it turns off.

There!! I've had my say. I'll shut up again for another two years.

Regards, Graham

Aether Audio · « **Reply #36 on:** 6 Apr 2008, 09:10 pm »

Bill & Graham,

Thanks for your kind words. I try to be as honest and forthrite as possible. I guess it comes from being too busy to think up "alternate" truths.

In some ways I can be my own worst enemy as I have a tendency to "wear my heart on my shirt sleeve" and spill my guts about whatever I'm thinking before I think things through a little more. Sometimes its best to keep your mouth shut.

Nevertheless, I'm still human and fall short many times. I guess if I could be remembered for speaking any truth, I'd rather it be for and about something & SOMEONE "higher" than speakers... or anything that I am personally able to accomplish. Ever since I was a kid I've always been preoccupied with finding the "truth," whether it be in science and the material world or the genesis and nature of all reality.

Unlike many in our modern world (and the statistical world of Quantum Mechanics), I believe in an "absolute" form of truth. I believe that it can be discovered and known both by science and in a very personal way by each of us. In fact, I guess I'd say that I've sort of always hoped my speaker designs would give testimony to this - a type of metaphorical representation that can be experienced in a very tangible way. Maybe we've accomplished that... maybe not. I guess that's for others to determine.

I do know this though: No "truth" can be truly known outside of that which is experienced and no experience can be had unless one's perception is attune and open to it. "For those that have ears to hear..."

God bless,
-Bob

lonewolfny42 · « **Reply #37 on:** 7 Apr 2008, 01:25 am »

Graham....

Quote

As soon as finances (had huge setback with my daughter being badly hurt in "hit n run" accident) allow, I will be purchasing sight unseen and unheard, a fully Mundorfed pair of Revelations.

Best wishes for a quick and healthy recovery for your daughter Graham....

Good luck....and thanks....
Chris

2bigears · « **Reply #38 on:** 7 Apr 2008, 02:17 am »

Graham,hit and runs are more than bad,best wishes for yours.... ,,,, Bob,"all we are saying is give peace a chance"

i am glad i have a set of your speakers and still in the tuning stage.

alotaklipsch · « **Reply #39 on:** 7 Apr 2008, 06:35 am »

I have had my revelations for a couple weeks now, finally, received my NWO 3.0 GO, and am waiting for a set of custom amps from Gary Dodd, I will let you kn ow within a couple weeks(hopefully) if tubes do it. I will tell you, right noe i am using 60 watt custom kt88 amps, and since my NWO came home........WOW.......just need better bass. On time, i will tell more.

Bob....keep up the great work

711smilin