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I'm considering the purchase of one of these two amps. Both are about the same price on the used market, but I won't have an opportunity to compare them before purchase. Can anyone who has auditioned both briefly compare them and suggest which one might be the better choice? I'll be using a tubed preamp (a Hovland HP-100) and will be driving either a pair of Martin Logan CLSes or SL3s.
Follow Ups:
The Pass X2.5 / X250 driving Logans delivered maximum articulation (level of clarity, transparency, resolving qualities, etc.) with no fat (warmth, forgiveness, margin for errors). I’m not sure if the Hovland and Pass x-250 are compatable, but sonically the Hovland or something Hovland-ish may make things more palatable than the somewhat drier tube preamps I tried.
Believe what your ears say - not hearsay.
which input are you using on the Hovland?
I'm using the MC phono input.
I like the Radia and Lamms.
That is a super bad impedance mismatch. The Hovland's, which I think is only single-ended, output impedance measured at a very high 4.3k at 20Hz. The Pass amps input impedance is a rather low 11k for unbalanced input. This is almost a 1:2 ratio, you need at least AT LEAST 1:10, so with the hovland you should look for an amp with an input impedance of 47k plus, 100k would be even better. If not you bass will be compromised.
You're right, I didn't realize how low an input impedance the Pass Labs amplifiers have in SE mode. I guess I'll have to, um, Pass ;-)
"I guess I'll have to, um, Pass ;-) "
Or get a tube preamp with lower output impedance. The Cary SLP-05 performed great with my Pass Labs X150.
That thought crossed my mind, but I'm very happy with the Hovland and listen to analog almost exclusively, so the builtin MC phono stage is a plus.
Might I suggest the Van Alstine Ultra 550? Cheaper than the Pass, super high input impedance as a result of the tube input stage, and a glorious reproduction of music to boot. The last drop of icing is a 30 money back trial.
Not a dealer, but an owner of the Ultra 550. I think it's one of the biggest high end bargains ever. Ironically, I run a Pass X1 into mine!
Second the vote for a Van Alstine.
- Another Ultra 550 owner
How does Van Alstine claim 250wpc for the Ultra 550 amp with such a small power supply transformer and a SHIPPING WEIGHT of only 38 pounds (which means the amp itself weighs closer to 30 pounds)?
I would question this power supply's ability to deliver on that 250wpc wattage spec as this is not a Class D "switching amp" but a more traditional design. I noticed that their website doesn't say at what impedance they deliver 250wpc. Most manufacturers are proud to show off their wattage ratings at 8 ohms, 4 ohms, and some at 2 ohms. And even though Van Alstine says they can drive a 2 Ohm load, they don't say at what wattage.
The last 250wpc amp that I owned had a 2000-VA power transformer and weighed 64 pounds on it's own - with a shipping weight of 74 pounds. It doubled power to 4 Ohms and doubled power yet again to 2 Ohms. And it didn't have a thick metal faceplate or chassis to add weight. It was mostly power supply. I suspect the transformer alone in this amp weighed more than the entire "250wpc" Van Alstine Ultra 550..
Similarly, the Pass Labs X250.5 (also rated at 250wpc) weighs in at about 100 pounds. How does Van Alstine do 250wpc in the 30 pound range?
There must be some "smoke and mirrors" going on with Van Alstine's 250wpc rating on their Ultra 550 amp and I would also question it's ability to adequately drive the Martin Logan speakers that the original poster is considering.
Some quotes from Stereophile's review of the ML SL3 speakers: "While the SL3 is revealing of every link in the chain before it, it is particularly demanding of power amplifiers..... This meant that high-powered or high-current amplifiers—such as the Plinius SA-100, or the Krell KAS or Full Power Balanced 600—were required to control the speakers and energize the room.". These amps are clearly in a different class vs the lightweight Van Alstine. Also note the 8 Ohm nominal but 1.5 Ohm minimum impedance on these Martin Logan speakers. The ML CLS maybe even more demanding with impedance drops as low as 1 Ohm.
While the Van Alstine amps may sound wonderful, I doubt their ability to adequately drive the speakers under consideration. And I am highly suspect of Van Alstine's power specs for their amps.
Van Alstine Ultra 550: Ultra tiny transformer for "250wpc":
and clearly the amp is not a heavily Class A biased amp like the Pass X250, which is maybe 25 or 30 watts Class A. From this picture it looks like the transformer is about 1000 watts or so, which is ample if the amp is about 60% efficient as a heavily Class B amp would be. This is how profi amps can generate a lot of power with not so impressive power supplies as they are nearly pure Class B.
Probably the Van Alstine amp cannot "double down" but unless your speakers are Apogee Scintillas or electrostats (maybe not a problem depending on the type) I don't see amp having difficulty with too many speakers.
You have to remember also that a big part of the Pass labs weight is chassis and heat sinks, both of which are necessary with a high bias SS amplifier. The Van Alstine, being more Class B, can get away with much less heat dissipation (although with high sustained levels it could be a problem but how often do you listen to 60Hz sine waves at 100db for 30 minutes straight??) and the chassis is clearly less elaborate and lighter weight. So is the price.
Class B can deliver more power with less constant draw on the power supply, requiring a much smaller power supply. I guess I'm just accustomed to thinking of high-end amps biased more into class A territory with the ability to "double down" as the impedance is halved.
While the Pass Labs does use a sizable thick faceplate and steel chassis, the Krell KAV-2250 that I mentioned uses a thin aluminum chassis all around. Yet the 250wpc Krell has a 2000-VA power transformer that accounts for most of the amp's total weight.
But you're right, I'm comparing an amp that can "double down" as the impedance drops to one that probably cannot (and as such does not have published specs for this capability).
I suspect the amp makes it's 250 watts at 4 ohms (the reason for limited specs), while the Krell makes 500 watts at 4 ohms (the reason for the 2KVA transformer).
I had a small Krell (Kav-500) with 1 kva transformer....120 watts at 8 ohm rated..... 240 watts at 4 ohm.
Tricks of the trade I guess?
Dave
I currently have a pair of 1,000 watt ICE module monos in for review. They are about the size of a shoebox. I see no reason to doubt their claims for power output. These technologies do not require the traditional size of large SS amps ... as to their performance, be your own judge. It is, however, quite possible.
Doctor S.
Who cares how much it weighs? Does it perform? From what I have read over at AC, it does. From what I heard at last years RMAF, AVA gear performs wonderfully. If you stated that the posted output was less, and had proof to back that, I would listen. But using the, "it doesn't weigh enough", arguement seems pretty weak to me. I don't own any AVA gear, so I really have no idea if the amps can drive difficult loads without strain. I have always enjoyed reading your posts Abe. Intelligent, informed posts from you have been informative. But this one, in my opinion, is reaching at best. Weight of an amp has no bearing on perfomance. I understand you questioning the ability of the transfomer to produce the speced wattage, but because one company used a transfomer that weighed more, does it really mean it performed better? Just my thoughts on the post, useless as they may be.
JCarney
An amp's ability to deliver power is directly related to it's power supply and most of the weight in a traditional power supply is in the transformer.
And since most 250wpc amps have much larger and heavier power transformers than the "250wpc" rated Ultra 550, I don't think I'm "reaching". I'm bringing up a legitimate concern.
You may be right. The transformer may or may not be up to the task. I really have no idea. Just throwin my 2 cents into the fray.
As an example, I had a pair of S&B step-ups for my Benz LP. On a recommendation from a friend, I tried a pair of Lundahls. Both of the Lundahls do not equal the size or weight of one of the S&Bs. But in my system, and to my ears, the Lundahls are better. I know the step-ups are a passive device, but bigger does not always translate into better.
I also wonder if the Mosfet devices have anything to do with the speced wattage. Maybe the circuitry in the hybrid design doesn't need a massive transformer to get that kind of power.
JCarney
AbeCollins wrote: How does Van Alstine claim 250wpc for the Ultra 550 amp with such a small power supply transformer and a SHIPPING WEIGHT of only 38 pounds (which means the amp itself weighs closer to 30 pounds)?
I have the box my 550 came in, the shipping weight is 42 pounds, for what it's worth.
I am sorry you feel that because the Van Alstine does not have a three quarter inch thick face plate and 20 pounds of heat sink that "smoke and mirrors" simply must be involved in the numbers, but since I actually do have a Van Alstine amp (that drives a pair of speakers that present a known challenging load to lesser amplifiers), I am going to stick to what I know works and not worry about your surprisingly bitter rant about an amp that apparently gets under your skin.
Sorry about that.
It was just an observation on my part that the Ultra 550 seemed rather lightweight to stand up to Van Alstine's 250wpc claim. It's also curious that they offer very little technical information relative to other highly reputable high-end amp makers. And that 38-Lb. shipping weight spec I mentioned for the Ultra 550 was taken right off the Van Alstine website.
One of the 250wpc amps I was comparing the Ultra 550 to did not have a thick faceplate or unusually heavy chassis. The Krell KAV-2250 has a 2000-VA power supply transformer that weighs more than the entire Ultra 550.
Take it for what it's worth but in my opinion, there's some "smoke and mirrors" going on here with the Ultra 550's 250wpc rating... At what impedance is it rated at 250wpc? What is it's output power rating while driving lower impedance loads?
I feel these are legitimate concerns when pairing an amp to a difficult load such as the Martin Logan speakers under consideration.
And just out of curiosity, how many different monikers do you post under Doolin Dalton, MeTwo, Darwin's Other Uncle , and what else?
Whatever seems humorously appropriate. This board could use some.
Desperately.
Put your money where your mouth is Abe, call up Frank and get a 550, you have a 30 day right-of-return. Take the amp to your local den of oscillscopery and have the specs measured for yourself, and then tell us all how much smoke there is and how many mirrors there are. I for one would love to find out.
I have nothing against Frank but it would seem to me that he should be the one to put his money where his mouth is. I don't see detailed specs for his amps, only excuses on his website as to why he thinks specs are meaningless (per the FAQ section of the website).
Hi Abe,
A Kell-400xi is a 200 watts amp and it is only 31lbs !! IMHO, the majority of the weight of those heavy amps is related to "heat sink" not the power supply itself. FYI, a 1000va (more or less good for 250w) tranformer is only about 15 lbs.
Ken
"A Kell-400xi is a 200 watts amp and it is only 31lbs"And the measured performance was below par for low impedances. Neither the amplifier perform well during the thermal tests. IOW, they cut corners.
Abe's concerns here are legitimate, Don't stick your head in the sand wishing that the issues will go away.
Music making the painting, recording it the photograph
"A Kell-400xi is a 200 watts amp and it is only 31lbs"
And the measured performance was below par for low impedances. Neither the amplifier perform well during the thermal tests. IOW, they cut corners.
Abe's concerns here are legitimate, Don't stick your head in the sand wishing that the issues will go away. "
Well did the 400xi gives out 200watts @ 8ohm? Yes according to the Stereophile - "No fewer than 290W were available with both channels driven into 8 ohms (24.6dBW) at our normal 1% THD definition of clipping, with 350W available into 4 ohms (22.4dBW)." It might overhead during party but nevertheless it can produce 200watt!!
How about MF5CR gives out 255w at 42lbs!
It appears you are the one that stick your head in the sand. Not every 250w amp has to weight over 100 lbs
I think the issue is the amp's ability to double power into 4 Ohms then double again into 2 Ohms. It takes a hefty power supply in order to do this and some speakers appreciate the added power at these lower impedances.
Without more detailed published specs, it's impossible to determine if an amp can do this. And when the specs are missing, you have to assume the amp can't.
Hi Abe,
This I have to agree with you as I don't think the amp can double down without a hefty power supply/heatsink. Based on the weight I think it could do 250wpc and it is unfair to call them "smoke and mirrors" as they never claimed double down.
Ken
Abe, I can only suggest you swing over to the AVA forum on audiocircle and ask Frank. As to the Ultra's ability to handle difficult loads, my Shahinian Diapasons spec out nominally at a little under 6 Ohms, and in the lower end of the frequency range drop to around 2 Ohms. My Ultra 550 can drive them to very loud levels without a hint of strain. The phase relationship of my speakers may be a bit more gentle, however, than the average electrostat. I'm not discounting your comments; a lot of current takes a big transformer and a lot of output devices. All I know is that I've tried plenty of amps in my system over the years - including Krell, Muse, Bryston, NYAL, Adcom, and others - and I'm happy with what I'm hearing out of the AVA Ultra.
Keep the Hovland and get the appropriate power amp.
You will be happier in the long run.
Enjoy,
Mike
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