Best measuring tube amp

[Strumbringer]

The measurement resolution here is not good enough to show the weird sideband behavior.

Interesting. OK. I'm going to go to the manufacturer's shop this weekend to hear it with my headphones and DAC.

 

[SIY]

Interesting. OK. I'm going to go to the manufacturer's shop this weekend to hear it with my headphones and DAC.

I haven't tested that particular one from LTA, but the model I did test showed very good distortion behavior and bandwidth for a tube power amp, but performed less well on complex signals. Poor enough to fuzz things up compared to a less expensive engineered amp? Or not bad enough to screw up the sound? That I didn't have time to test, but unless I was spending for the sake of acquiring interesting objects (and Berning's amps are interesting objects) rather than for sound, I'd put my money elsewhere.

 

[Blumlein 88]

I haven't tested that particular one from LTA, but the model I did test showed very good distortion behavior and bandwidth for a tube power amp, but performed less well on complex signals. Poor enough to fuzz things up compared to a less expensive engineered amp? Or not bad enough to screw up the sound? That I didn't have time to test, but unless I was spending for the sake of acquiring interesting objects (and Berning's amps are interesting objects) rather than for sound, I'd put my money elsewhere.

Yes David Berning's designs were interesting for sure. I'd rather like to try one, but they are not common and are quite expensive so never pulled the trigger on amp or preamp.

 

[Sokel]

Mactone are said to measure well,near 1% at their rated power but I can't find any measurements online.
However I know that they come with some measurements in their box,I'll ask the friend who has them to find it and give it to me.

 

[anmpr1]

Wolcott tube amps were probably the best measuring tube amps. I seem to recall, depending upon the model, THD of .01% at rated power, and these were powerful amps. Easily drive Soundlabs big esl panels.

Interesting that no one has discussed the EAR 509. Measurement wise it is up there with best.

A colleague drove dual (I think they were mono--doing this from ancient memory) Wolcott amps with his rather large SL panels. At start up the amplifier utilized a 'computer' circuit that biased its tubes (and the amps had a lot of them, for sure). So although it took a while for the Wolcott to POST, once done they certainly drove the panels to loud SPL. Subjectively I didn't recognize anything 'tubey' about them, when listening.

On the other hand, my dealer sold large floor to ceiling Acoustats. Once while slumming, a customer brought in his EAR amplifier for a demo. I was happy, because I'd read so much about them in the tweako press. Attempted to navigate the Acoustat's impedances, it was clear to all how the amp was distorting badly (although it sounded 'good', liquid and all that).

One of my amps at the time was Jim Strickland's 200 watt/ch MOSFET design. It certainly drove Acoustat panels as loud as they would play before the panels bottomed out. My guess is that the TNT would have been a good 'fit' for Sound Labs. Subjectively, some folks criticized the 200 for being on the 'dry' side. It is one amplifier that I wished I still owned, BTW.

When it comes to tubes, I always had luck using higher sensitivity loudspeakers. But I grew up on JBL, and not AR. Consider La Scalas (probably in the 'honest' 100 dB/watt/meter range--don't trust Klipsch's 105dB 'official' value, and Hi Fi News measured about 102dB with a recent sample). But 100dB sensitivity is loud, however you cut it, and a 12 watt per side tube amp is really all I need. The AHB2 is better..., you can turn the Benchmark up to 11, stick your ear in the horn and not hear any noise. Tube amp doesn't work like that. I'd say that visually, and from a tactile standpoint, tube amp looks a lot cooler, but runs a lot hotter. So it's a mixed bag, depending upon priorities.

I don't understand the idea of 'measuring' a tube amplifier. Other than to make fun of it. I don't like kicking a dog that is down, either.

 

[SIY]

I don't understand the idea of 'measuring' a tube amplifier. Other than to make fun of it. I don't like kicking a dog that is down, either.

Or to see if it was well-engineered within its constraints. If one has the goal to have a tube esthetic but not have the actual perceived sound fouled up, measurements are essential.

 

[anmpr1]

Or to see if it was well-engineered within its constraints. If one has the goal to have a tube esthetic but not have the actual perceived sound fouled up, measurements are essential.

I know. I was being cynically funny. But really, in 2022 there's not much else to discover, other than whether the thing will electrocute you when you plug it in, that is not known or at least expected.

It's not even much of an issue with anyone who might be considering a purchase. At least I don't think it is. Most folks buy a tube amp because it looks cool, or because it is something that is within their skill level to build at home, in their spare time.

From an ASR standpoint, tube amps really need to be in a distinct category. That would make sense, by way of comparison. I don't know how hybrids would fit in. A lot of tube amps are hybrids.

 

[Tom C]

I chose mine on the basis of this:

McIntosh MC275 power amplifier Measurements

Sidebar 3: Measurements

www.stereophile.com

 

[DMill]

I bet more people on this site than you think own a tube amp/pre amp or integrated. And the majority of them are well aware of their shortcomings and measurements. I won’t speak for them but why do I still have mine and haven’t sold it off? Looks, sounds good especially at low to medium volumes, fun to tweak tubes, built like tank and will last forever (at least as long as the transformers hold out). I have to say in most circumstances where life is happening all around us in our house, kids running around, tv on in the other room, wife in the kitchen, etc. I can’t really tell much of a difference between it and my better measuring system. Surprising how little 40db difference in SINAD is in the real world. But no doubt, the 1-2 hours a week that I can sneak away from distractions and crank it up, my solid state rig sounds better and I’m sure measures better. Might be interesting to have a poll to see how many ASR folks still own tube gear?

 

[Snafu]

Marantz 9 and 8B also met the under 0.1% THD 20-20kHz at rated output ppower benchmark.

I have Nelson Audio Image M9 monoblocks that are based on Marantz 9 (i don't know how much, this from Nelson Audio)
manual says:
70W
THD 0.8% (20Hz-20kHz)
20Hz-30kHz +/- 2dB
S/N >85dB
18kg each

imo very good tube amps

 

[anmpr1]

I chose mine on the basis of this:

McIntosh MC275 power amplifier Measurements

Sidebar 3: Measurements

www.stereophile.com

True story (I say that because half the stuff I write is tongue in cheek): I was at another colleague's house for a cook out, and he was showing me around. He was most proud of a custom home theater, built by one of the local installers. Movies are not my thing, so I was nodding indifferently when on one of the shelves in the room I spied a somewhat beat up, vintage MC275. Just sitting there. I asked him about it and he said he didn't know anything. It was his dad's from years past, and after dad beamed up he just took it as a memento.

He said he never used it, but simply kept it as a 'decoration'. I told him that he should take care of it, and if he was interested he might be able to sell it for some serious money. He laughed incredulously. Then replied, "Let me show you my home office. If you think this thing is important, wait until you see my old Royal typewriter I found at a garage sale? Some of the keys still work, but I need to find a new ribbon for it!"

 

[mhardy6647]

He said he never used it, but simply kept it as a 'decoration'. I told him that he should take care of it, and if he was interested he might be able to sell it for some serious money. He laughed incredulously. Then replied, "Let me show you my home office. If you think this thing is important, wait until you see my old Royal typewriter I found at a garage sale? Some of the keys still work, but I need to find a new ribbon for it!"

mmm... typewriters...

I did actually manage to find these two good homes.

Still have a couple of Selectrics, though.

 

[Blumlein 88]

A colleague drove dual (I think they were mono--doing this from ancient memory) Wolcott amps with his rather large SL panels. At start up the amplifier utilized a 'computer' circuit that biased its tubes (and the amps had a lot of them, for sure). So although it took a while for the Wolcott to POST, once done they certainly drove the panels to loud SPL. Subjectively I didn't recognize anything 'tubey' about them, when listening.

On the other hand, my dealer sold large floor to ceiling Acoustats. Once while slumming, a customer brought in his EAR amplifier for a demo. I was happy, because I'd read so much about them in the tweako press. Attempted to navigate the Acoustat's impedances, it was clear to all how the amp was distorting badly (although it sounded 'good', liquid and all that).

One of my amps at the time was Jim Strickland's 200 watt/ch MOSFET design. It certainly drove Acoustat panels as loud as they would play before the panels bottomed out. My guess is that the TNT would have been a good 'fit' for Sound Labs. Subjectively, some folks criticized the 200 for being on the 'dry' side. It is one amplifier that I wished I still owned, BTW.

When it comes to tubes, I always had luck using higher sensitivity loudspeakers. But I grew up on JBL, and not AR. Consider La Scalas (probably in the 'honest' 100 dB/watt/meter range--don't trust Klipsch's 105dB 'official' value, and Hi Fi News measured about 102dB with a recent sample). But 100dB sensitivity is loud, however you cut it, and a 12 watt per side tube amp is really all I need. The AHB2 is better..., you can turn the Benchmark up to 11, stick your ear in the horn and not hear any noise. Tube amp doesn't work like that. I'd say that visually, and from a tactile standpoint, tube amp looks a lot cooler, but runs a lot hotter. So it's a mixed bag, depending upon priorities.

I don't understand the idea of 'measuring' a tube amplifier. Other than to make fun of it. I don't like kicking a dog that is down, either.

Acoustats and SLs used the same split xfmr arrangement with similar impedance. Very high at low frequencies and less than an ohm at 20 khz. I could have told you the EAR would be less than good on either. I've never had hands on with Wolcott. Big mosfet amps and tube amps usually work. VTLs, ARs, C-Js. The best thing I've found for them is class D amps. With some large bipolar amps I've found adding a .5 ohm or 1 ohm power resistor in series will make the amp happy. If you intend to make it permanent you can just put it in series with the high frequency transformers.

 

[anmpr1]

Still have a couple of Selectrics, though.

The Selectric was the McIntosh of typewriters. IBM was at the top of their game with those. Probably survive a nuclear hit.

 

[mhardy6647]

The Selectric was the McIntosh of typewriters. IBM was at the top of their game with those. Probably survive a nuclear hit.

Great to type on, as well.
I didn't acquire a few for no reason
I think I am down to only two here now, though.
I think.

No tubes in them, though, so I suppose I've drifted a bit off-topic...

 

[Deleted member 50971]

I don't really know but yes, McIntosh have ALWAYS been known for good sound. I'd expect the noise to be inaudible and the distortion and frequency response should be better than human hearing. They should be as good as any solid state amp.

But IMO - It's silly to buy something made with technology that's been outdated for at least 50 years. It's expensive, especially if you want power (Watts), it's very energy inefficient, and the tubes age, their characteristics change*, and they eventually die.

Transistors and MOSFETs are "naturally" low impedance which makes them more suited for driving 4 or 8-Ohm speakers, and that means they can drive the speakers directly without an output transformer. (An audio transformer doesn't necessarily degrade sound, but it's "difficult" to make a transformer that covers the full 20-20kHz range, and even more difficult and more expensive if it has to handle power without distortion.)

Back in the tube days, most audio equipment wasn't that great. It was never cheap or easy to get good sound, especially from a power amp (or a power-output stage) since that requires a transformer. With solid state it's been pretty easy from the beginning, and it's just been getting cheaper and easier with integrated circuits.



...Guitar amplifiers may be an exception. Guitar amplifiers are not meant to be high fidelity, the tube circuitry and the output transformer are designed to distort in a "pleasing way", especially when overdriven. Electric guitar doesn't sound right when played through a hi-fi amplifier. This makes the amplifier "part of the instrument". It also means that they all sound different and every guitar player has their favorite amp as well as their favorite guitar. Of course there are also solid state guitar amps, and they are also not high-fidelity. And, there are some that can "model" a variety of other famous amps.


* A GOOD amplifier CAN be built so that as long as the tubes remain in-spec the sound won't deteriorate or change. I'm sure McIntosh amps are built this way. Although transistors & MOSFETs don't age, their characteristics (such as gain) varies from part-to-part. So solid stage amps are usually built with the same philosophy.... So every amplifier off the production line performs consistently even though the parts vary.

Good morning/afternoon. I’ve never owned a Mac before, word on the street is they are more looks than performance, and some are mesmerized by the blue glow. Maybe I’m misinformed because I’ve never owned one, are you saying that the older ones, like the touted 275 are as good as it gets in the tube amp world? I own Wilson Audio speakers although mine are 20+ years old, and the only Wilsons I have ever heard. I believe mine are not over the top, and I honestly believe that they put some good engineering into them, because they measured pretty well in one of the magazines back in the day.

Anyway are Mac amps getting a bad rap online and they are actually good?

I have a 1964 Fisher integrated amp that is all tubes. I never measured it but from the manufacturer at full power which is roughly 20 W per channel there is .8 harmonic distortion. It’s a great conversation piece, looks cool, works well for what it is.

 

[SIY]

Anyway are Mac amps getting a bad rap online and they are actually good?

They are very, very good, well into the "sonically transparent in most situations" area. Very smart engineering. I would be happy to stumble on a set of multifilar output transformers to work with that design.

 

[Deleted member 50971]

They are very, very good, well into the "sonically transparent in most situations" area. Very smart engineering. I would be happy to stumble on a set of multifilar output transformers to work with that design.

I appreciate that thanks. We hear so much talk online but I’m glad I know the truth.

Their tube amps are beautiful looking.

Not to put you on the spot, but if you chose a reasonably priced tube amp roughly 75 WPC what would you pick? Is there something newer that would be up to standard? I’m asking because the Mac 275 is really pricey.

I believe from reading a lot of threads on here that you make your own, so I will leave those out of it.

 

[SIY]

I appreciate that thanks. We hear so much talk online but I’m glad I know the truth.

Their tube amps are beautiful looking.

Not to put you on the spot, but if you chose a reasonably priced tube amp roughly 75 WPC what would you pick? Is there something newer that would be up to standard? I’m asking because the Mac 275 is really pricey.

I believe from reading a lot of threads on here that you make your own, so I will leave those out of it.

Yeah, I am VERY negative about the newer amps- most of them are cut and paste designs of poorly-understood 1950s circuits. And I have been pretty vocal that unless you are knowledgeable about tube electronics and have decent test gear (scopes, DVMs, at least a soundcard-based spectrum analyzer), you shouldn't mess with tubes in 2022. It's like having a classic Triumph or Austin-Healy; you need to be proficient with tools to keep them running properly.

So if you're not a tube amp design maven, there's two choices: a well-restored classic amp like the old Macs or H-K or similar, or build from a proven kit like Pete Millet's Engineer's Amp.

There is no inexpensive, no-hassle way to do tubes well in 2022. It is unfortunate, but it's true. Money or hassle, you're doing fetish objects, not electronics.

 

[Deleted member 50971]

Yeah, I am VERY negative about the newer amps- most of them are cut and paste designs of poorly-understood 1950s circuits. And I have been pretty vocal that unless you are knowledgeable about tube electronics and have decent test gear (scopes, DVMs, at least a soundcard-based spectrum analyzer), you shouldn't mess with tubes in 2022. It's like having a classic Triumph or Austin-Healy; you need to be proficient with tools to keep them running properly.

So if you're not a tube amp design maven, there's two choices: a well-restored classic amp like the old Macs or H-K or similar, or build from a proven kit like Pete Millet's Engineer's Amp.

There is no inexpensive, no-hassle way to do tubes well in 2022. It is unfortunate, but it's true. Money or hassle, you're doing fetish objects, not electronics.

I understand what you’re saying, and I appreciate the honesty. I have a tube tester, and I can set the bias, and do simple repairs, clean with deoxit, and that’s the extent of my knowledge, and repair ability.

Maybe one day, until then I’ll tinker with my Fisher integrated tube amp.

Thanks again.