Tube amps & speaker efficiency

 

New member
Username: Big_luni

Hartford, CT

Post Number: 7
Registered: Jan-05
I know this is a speaker question, but there seem to be more tube amp guys on this board than on the speaker board. I'm looking to get speakers for my tube monoblocks (on a budget), but I read that I should look for efficiency well into the 90s. My Marantz Model 2 amps are rated at 40 watts each. Am I asking for trouble if I get, for example, B&W 303 speakers rated at 88db sensitivity? I want to make sure I get speakers that sound good, and make my amps sound good. As modern speakers seem to be designed with more powerful Solid-State receivers in mind, I want to make sure I choose wisely.
 

New member
Username: Big_luni

Hartford, CT

Post Number: 8
Registered: Jan-05
Sorry about the double post- I didn't think the other one went through!
 

J. Vigne
Unregistered guest

With 40 watts of tube power, you can pick almost any speaker you wish. Though the output transformers on the tube amp provide some allowance for the speakers impedance, you will do best to avoid speakers that show the amplifier a complex load with wide variance from the lowest to the highest point of the impedance curve. Frequency variations can result from this type of speaker whether you are running a tube or a solid state amplifier. The B&W's will match well with your tubes. Try using the various impedance taps the amplifier provides as the sound will vary somewhat with each tap. Using an 8 Ohm speaker on the 4 Ohm tap will give a slightly drier sound more like transistors; while the 16 Ohm tap will soften the sound. Power and distortion product also vary slightly when the taps and the speaker are mismatched. How much depends on the combination. Try each and find the one you think sounds best with your speakers.

A WORD OF CAUTION!!!

Never let the amp run powered up with no speaker load on the amplifier. Speakers must always be connected while the amp is on, and, the amp must be turned off if the speakers will be disconnected for even a moment.


 

PLAN B
Unregistered guest
Thanks for the word of caution. I'm trying purchase amps right now, and didn't know anything about that.
 

Silver Member
Username: Varney

BirminghamEngland, UK

Post Number: 273
Registered: Sep-04
No, I didn't, either.

Does this apply to tubes only, or transistor amps as well?

V
 

J. Vigne
Unregistered guest

Just tubes; though it's a good idea to turn off any amplifier when making connections. A tube amp will go into self induced oscillation and will eventually destroy itself.


 

Silver Member
Username: Touche6784

Post Number: 101
Registered: Nov-04
just out of curiosity, what would be the difference in a tube amp compared to a transistor amp that would make me want to buy the tube amp? i know there are some other threads in here about it but i would rather get a concise general answer here. thanks.
 

J. Vigne
Unregistered guest

The sound. Sorry, that's the best, most concise answer.


 

Gold Member
Username: Kegger

MICHIGAN

Post Number: 2146
Registered: Dec-03
Christopher Lee: check this link out and the thread tube talk is nice!

For anyone who may be interested , a little fine reading on tubes!

http://home.comcast.net/~enghenry/diy/taste.pdf

(you'll nead acrobat reader , but can download it for free)
 

Gold Member
Username: Kegger

MICHIGAN

Post Number: 2147
Registered: Dec-03
Big Luni with 40 watts a channel as low as I'd go on speaker eficency
is about 88db but as jan has mentioned the complexity of the xover
and the impedence swing play a big part to.

If your looking for a lot of volume out of the speakers I'd stay around 93db on up.

I'm running about 25 to 40 watts a channel on different tube amps and the
klipsch reference series line of speakers have some great efficency and for me
work really well. (not everyone is a klipsch fan though) The lower lines of
klipsch skeakers you generally see at the chain stores don't do the reference
series justice though, the drivers on those are very different from the reference!

If your content with not really jamin then a lower effecincy speaker will
work fine just at a reduced volume!

I know it's been posted all over the place but speaker efficency and watts
basicly determine your spl and it takes double the power to gain 3db in spl.

Take a 93 db sensitivity speaker!

1 watt = 93 db
2 watt = 96
4 watt = 99
8 watt = 102
16 watt = 105
32 watt = 108
64 watt = 111
128 watt = 114
256 watts = 117 db

See as you go up in sens. on your speakers you don't need a high powered amplifier
to get loud music. You "could" get louder music with a 40 watt amp and really
sensitive speakers verse a 200 watt amp and speakers that aren't sensitive!
 

J. Vigne
Unregistered guest


http://www.myhometheater.homestead.com/splcalculator.html


 

PLAN B
Unregistered guest
Thanks for that link. I was worried that 50watts a channel for surround wasn't going to be enough, but it looks to be decent
 

Anonymous
 
joeman12
 

nout
Unregistered guest
What is this?
Some kind of pathetic voodoo spell?
For it to work it must be spelled Yo Man 12 (12 stands for the amount of joints smoked).
 

Silver Member
Username: Varney

BirminghamEngland, UK

Post Number: 305
Registered: Sep-04
"Just out of curiosity, what would be the difference in a tube amp compared to a transistor amp that would make me want to buy the tube amp? i know there are some other threads in here about it but i would rather get a concise general answer here. thanks."

"The sound. Sorry, that's the best, most concise answer."

But how would you describe that sound?
More dynamic? More rounded in the bass area? Sharper in the highs? More controlled? Better detail in the mids? Or is it this elusive term: 'musicality' again? Does that possibly equate to 'soft', I wonder?

I know you'll tell me to listen, but something tells me tubes are more of a long term investment in sound, rather than an immediate impression upon first hearing.

I am also interested to know what 'Joeman's' game is.... Could be looking to become a silver member through amount of posts. As it is, 'Anonymous' is already something of a 'member'.

V
 

J. Vigne
Unregistered guest

Sorry, Varney, there is no way to describe "tube sound" since there is nothing I consider typical tube sound. I find the asumption tubes will sound this way or that to be ill informed. Soft is a possibility just as is hard, or clean, or dynamic. There are good tube amps, bad tube amps and excellent tube amps along with most everything between. Tube products sound different from one another because tubes themself sound different from one another. A McIntosh tube amp doesn't sound like a Dynaco tube amp any more than a PS Audio amp sounds like a Krell. Triodes, Ultralinear and Unity Coupled all are schemes of design which affect the sound. Transformers are a large part of a tube amp and the skill with which the designer uses and manufactures transformers will, to a large extent, determine how a tube amplifier sounds. Not everyone is willing, or can, produce a good transformer.

Some people will immediately find tubes to their liking, some will not. Tubes will become more interesting to some poeple as they spend time with a tube product. Certainly tubes tend to be less "impressive" than transistor products. that alone is why many prefer tubes.

There is no answer I can give to the question since anyone who doesn't listen in the same fashion I do may not hear what I hear. I'm afraid the best answer is what I gave and the only way to experience that sound is to listen for yourself.



 

Silver Member
Username: Varney

BirminghamEngland, UK

Post Number: 307
Registered: Sep-04
Thanks J. Yes, I can well imagine it's something which grows on you with time. It actually took me a while to realise the real 'character' of my first NAD and how it was dealing with complex music. The reason I got interested in tubes, in the first place, is because of the notion I have that perhaps transistors were the reason mass-market equipment can exist; that something cheaper and maintainance free was required to bring the units in line with practicality and affordability in a consumer society. Equally true could be the idea that solid state sought to make improvements upon the performance of the valve. I'm sure I will start thinking about buying a tube-amp sometime in the future, because the ideas surrounding this older technology still continues to fascinate me.

Alas, for now I have a compressed air problem which will distract my finances away from buying more hi-fi.... Boo! Whether to invest in more machinery or open an account with BOC for bottled air.

Regards,

V
 

Gold Member
Username: John_a

Post Number: 2773
Registered: Dec-03
Varney,

There are various direct-sale valve amp manufacturers and distributors in UK. Like you, I am considering this route. Icon Audio in Leicester have a amp rated highly by HiFi News. It is 2 x 40W, switchable to 2 x 17 W in triode mode, all for about £1000. WIthout the triode option and without a tape pre-out it is about £600. If you look at this and other makers' customer testimonials all you find is ecstatic praise; it is impossible to make a sensible judgement. I understand from J.V., Kegger and others that one cannot make an instant judgement, and have to live with an amp to decide how you like it. So auditioning at a dealer is difficult, even if you could find one. There is also "The Affordable Valve Company" in Kent; simlar prices and specs. How they compare for sound, I have no idea. All offer 30-day refunds if not satisfied. If you ever learn more on these, I should appreciate your views. There are also PrimaLuna Prologue amps, made in China and distributed from the Netherlands. These can be auditioned but you need to find a specialist dealer. There is also a UK (Cambridge) company called "Papworth" making valve amps with McIntosh circuitry. They are in a different price league, however.
 

Silver Member
Username: Varney

BirminghamEngland, UK

Post Number: 310
Registered: Sep-04
Thanks for the links, John. Shame though - I am halted in buying anymore hi-fi by the afformentioned problem. I have a £400 machine here which is playing up.

£1000 remains rather out of my price bracket at the moment. I'd be looking more within the £3-500 area for amplification.

Cheers,

V
 

Silver Member
Username: Kano

Post Number: 297
Registered: Oct-04
"There is no answer I can give to the question since anyone who doesn't listen in the same fashion I do may not hear what I hear. I'm afraid the best answer is what I gave and the only way to experience that sound is to listen for yourself."

What equipment do you own?


 

Gold Member
Username: Kegger

MICHIGAN

Post Number: 2167
Registered: Dec-03
Kano:

Jan runs mac tube amps and an audible illusions preamp.

But he's been an audio sales men for quite some time and has had/heard many
different pieces of tube audio equipment.

And I agree with him it's very difficult to describe the sound.
As I run tube audio equipment also. And all I can say is that to me it's
just more enjoyable to listen to and seems more realistic with the harmonics.
 

J. Vigne
Unregistered guest

Kegger may be tired of hearing me say this but tubes are all about how the note starts and stops and all the moments in between those two points.

I have owned the same basic system for quite a few years, 2 McIntosh MC240 power amps that are strapped into mono, an Audible Illusions pre amp and either Spica Angelus or Rogers LS3/5a speakers. I have owned or borrowed several tube products through the years, though I am by far not an expert on tubes. I was fortunate to work with a few people that had been around tubes for much longer than I and they were generous in sharing their knowledge. I happened to find a system I like at a price I could afford and have stayed with it. I have definitely heard better systems at far higher cost, but my system has enough in common with these systems that I can be satisfied at home.
There are bad tube products on the market, or at least tube products that may not suit what any one person is looking for in a system. Tubes are not for everyone and shouldn't be considered a panacea for a poorly put together system. In the right context tubes will fascinate the listener, but the same can be said of very good transistors also.

The used market offers some good values in tube products, though I have found the product that retains its price through the years is probably the best buy in audio equipment. I was fortunate in buying my amplifiers at a very good price, but I also enjoy the fact that the McIntosh tube amps are worth ten times their original selling price. The Quads and Radfords are much the same and they are products you should hear if you are curious about tubes because they set the standard forty to fifty years ago and are still considered competitive. As John, Kegger and I have discussed on another thread, listen to a Mercury recording played on a Quad system of that vintage and consider how far the industry has moved in the last few decades.




 

Silver Member
Username: Frank_abela

Berkshire UK

Post Number: 317
Registered: Sep-04
Tube amps vary in sound as much as any other amp nowadays. There was a time long ago when all tube amps sounded warm and lush. I believe that part of the reason for his is that a lot of amps in the 50s and 60s were based on Mullard designs - since the design is from the same house, the sound has similarities. This is not the case any more and they sound as varied as any transistor amps.

For £500 you could be looking at Affordable Valve Company who have cheap looking ads in HiFi News; they make big claims for themselves and offer a money-back guarantee.

It's difficult to get below £500. Valve amps need to have some very high power components. In particular, the transformers in valve amps have to deal with a lot more power than you'd expect. Typically, valve amps are class A. A 40watt stereo amp will consume 400 watts of power. The voltages across the tubes themselves are very high (~400 volts), so the components have to have some serious power handling as well as built-in longevity. For that, you need quality components and they cost money.

I believe Audio Note make a £500 integrated too. I'd go with them before I went with AVC simply because Audio Note have a long established reputation and I quite like the sound of their kit.

Regards,
Frank.
 

J. Vigne
Unregistered guest

Frank, I would disagree with your comment about tube amps running in Class A. My experience has been most tube amps run in the same Class A-B mode that transistor amps use. It is done for efficiency in tube amps just as it is with transistors. A simple check of a tube amplifiers construction will determine quite often whether the amp is in Class A or A-B. If there is more than one power tube per channel, the amplifier is probably running in Class A-B. It is very uncommon to see more than one tube per channel being run in parallel hook up in Class A. So, one output tube per channel is likely to be Class A. Two or more output tubes per channel is likely Class A-B. Not a hard and fast rule, but a good start.

It is true that a single ended amplifier will be in Class A since that is the only way to make that amplifier with one output tube per channel. With no cut off between + and - sides of the wave form, which is the description of single ended, the amp can do nothing but run in Class A.

I have found it rare to have a Class A tube amp because of the large amounts of heat and the expensive transformers needed for that mode. If a tube amp is going to be designed around Class A operation, I find it will typically be a small wattage amplifier.

It is true that a tube amp will run at high voltages internally with 450 volts DC being common. But there is little current in a tube amplifier and that reduces the stress on the components. To find a tube amplifier that produces more than a few amps of current is also an anomaly, though the trend from certain manufacturers has been to get more current out of the designs to meet the needs of the odd speakers that dip to 1 Ohm. These amps are typically quite expensive due to the heavy duty components needed to run at high voltages/high current.

If you read the after market literature on replacement components, particularly capacitors, you will see what many consider the biggest difference between today's amplifiers and those of forty years ago. A paper in oil cap sounds very different from a polystyrene cap. Which sound you prefer is a matter of taste. It is true that you can group tube amplifiers into certain "sounds" such as Williamson, Mullard, Ultralinear and Unity Coupled, but that still leaves large amount of room between manufacturers for variations in circuitry. Looking at the schematics of tube amplifiers, and the technical papers, from the 1940-60's will show a tremendous amount of experiementation with circuit design. Each design having its advantages and disadvantages. I do think, however, if you discuss tube amps of the Golden Age with a tube collector you will find more emphasis on the passive components themself than on the overall design category.


 

Silver Member
Username: Varney

BirminghamEngland, UK

Post Number: 317
Registered: Sep-04
".... tubes are all about how the note starts and stops and all the moments in between those two points."

That really is all I need to know so far without actually hearing them. So far, so good.... If that's the case, then it's enough to warrant a further look.

V
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