Crazy idea from a CHEAPSKATE (Me) - Low powered tube amp?

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soundacct

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Hi All,
I have been positively itching for a tube amp, but I just can't afford an all tube system for daily use...

Specifically I was wondering if anyone has actually tried something like this, not whether it's possible or not (though, opinions are welcome of course).

Has anyone tried one of those low power tube amps (such as the Miniwatt N3 / Appj, or other Chinese like Quinpu, Music Angel, Yaqin, etc). Specifically, they are SET tube amps with output power from the 3.5 - 15 watt range.

My crazy idea is to bi-amp my Aeons with the tube amp on the panel, and try out different solid state amps on the woofer.

This idea is not to replace my SS amp, but to be an alternative for lower volume listening such as late night, or when entertaining guests.

ML specs my Aeons at 89db sensitivity - not bad actually. Does anyone know if that's for the panel as well as the woofer? Some kind of average?



Though I hung up the tights years ago, my schooling and early employment was fixing electronics, so I'm sure I can brush up enough to handle a tube amp.

Thanks all!
 
yes....crazy idea, a SET tube amp for a highly capacitive load like what's present on our panels is........crazy !
 
Please enlighten me?

What would happen with the SET amp arrangement? Would it let the smoke out of something?

Honestly, I've been able to drive my Aeon's with everything I've tried. From a tired old 1991 junky pioneer receiver to an OK-ish Sony TA-N55ES Power amp...even a 25 watt car stereo amp running off a battery & charger.

Though I keep reading that electrostats are hard to drive, I keep finding that every amp I try handles it with ease.

I'd hate to buy a new amp just to ruin it though..
 
soundacct said:
This idea is not to replace my SS amp, but to be an alternative for lower volume listening such as late night, or when entertaining guests.
Click to expand...
What's the point in a special amp when entertaining guests? You're using the music as background, so not paying attention to it.
 
Here are a couple of old threads involving low-powered tube amplifiers driving the Logan panels:
  1. Power requirement for tube amp to drive Summit
  2. Summits and a 15w Tube Amp
I think the general consensus is that you'll need at least 30 watts per channel (on the panels) for the Logans.

Though I keep reading that electrostats are hard to drive, I keep finding that every amp I try handles it with ease.
Click to expand...
Don't mistake audible sound versus high-quality music coming from the panels. All amplifiers with a couple of watts are capable of getting the panels to make sound, but that is a far cry from getting the most that the Logan panels can offer. Here's a thread on power requirement for the Logans:
Dynamic range and power claim

This idea is not to replace my SS amp, but to be an alternative for lower volume listening such as late night, or when entertaining guests.
Click to expand...
Lastly, I don't get this point of "entertaining guests" with tube amp. If it's going to be background music, why waste tube life when it's unnecessary? You could just turn down the volume of your solid-state amplifier and nobody would even notice the difference. Am I missing something here?
 
Bernard said:
What's the point in a special amp when entertaining guests? You're using the music as background, so not paying attention to it.
Click to expand...

conversation piece, believe me nobody I know has ever seen a working tube amp.

anyhow I think you've narrowed in on the wrong part - I've been itching to try a tube amp, and there are occasions when I dont need loud volume, like when guests are in the house for example.
 
Spike said:
Here are a couple of old threads involving low-powered tube amplifiers driving the Logan panels:
  1. Power requirement for tube amp to drive Summit
  2. Summits and a 15w Tube Amp
I think the general consensus is that you'll need at least 30 watts per channel (on the panels) for the Logans.


Don't mistake audible sound versus high-quality music coming from the panels. All amplifiers with a couple of watts are capable of getting the panels to make sound, but that is a far cry from getting the most that the Logan panels can offer. Here's a thread on power requirement for the Logans:
Dynamic range and power claim


Lastly, I don't get this point of "entertaining guests" with tube amp. If it's going to be background music, why waste tube life when it's unnecessary? You could just turn down the volume of your solid-state amplifier and nobody would even notice the difference. Am I missing something here?
Click to expand...



Spike, thank you very much for the links!
There is so much information on MLO that I find it difficult to navigate, it's not for lack of trying to answer my own questions by searching. Being that I dont get to spend as much time as I'd like on various forums, maybe I'm just no good at sifting through all the posts yet.

anyhow, yes kind of missing the point - I think tube amps look cool...just like the Martin Logan panels don't need to be transparent, but they are, and i purposely place things on the wall behind so you can see them through the speaker from different vantage points...just because I think it looks cool.
I also have a line on a 30 or 35 watt push pull type with el34 tubes (not sure what kind, but the owner does have a lot of top notch equipment so probably not junk)
Lastly, there's the thing about volume level...basically i have no self control! I just want to keep turning it up and up! Maybe a small amp would help keep me in check in the later hours of the evening.
 
It would be fun to try. But realistically, it would be 0kay for background music only. I like the Miniwatt N3. I'm thinking about buying one myself for fun...
 
edwinr said:
It would be fun to try. But realistically, it would be 0kay for background music only. I like the Miniwatt N3. I'm thinking about buying one myself for fun...
Click to expand...

Yep, that's it...just for fun.

Well put, you took the words out of my mouth ...er...keyboard...er...you know what i mean.


I cant wait for my brother-in-law to come over for christmas and ask me how I got a bunch of light bulbs to make music come out of a couple window screens!

the blessing and the curse for me is that I know literally nobody into high end audio.
 
soundacct said:
...the blessing and the curse for me is that I know literally nobody into high end audio.
Click to expand...

That was my situation a few years ago. Absolutely nobody I knew well was into hi fi. I pretty much taught myself - making my own mistakes (some expensive ones too!).

But now it's all good. All three of my close neighbors are about the same age as me, and after laughing and poking fun at me for years, they've all been bitten by the bug. One neighbor now owns Dali Helicon 800s with appropriate electronics, another owns B&W 802s with a tube/mosfet hybrid power amp. It's nice swapping stories and experiences...
 
Indeed...it could be helpful to hear other setups.

Back in the car stereo days (sorry, neighbors!) that's how i did it, and i must say it was easier to hear and decide than it is to read online and decide.

This being the main reason I joined MLO (thanks Tom).
 
A few things to keep in mind, soundacct.

Remember that stats present a mostly reactive (ie capacitive) load to an amplifier and, therefore, operate on volts and not watts. You have to be very careful when looking at an amp’s wattage rating when it is being used to drive a stat panel. Watts is far less important than the amp’s power supply voltage rating! An amp with an inadequate power supply voltage performance will easily clip when hooked up to a stat …. despite its wattage rating.

Also keep in mind that a stat’s highly reactive behaviour means that it has weird phase angles and sends electrical current back to the amp (when signal reverses polarity). Many amps tend to be unstable under such conditions so you need to make sure the amp is stable with reactive loads.

Furthermore, because a stat acts like a capacitor, its impedance is inversely proportional to the frequency it sees. So a stat will have a high impedance (say a couple hundred) at low frequencies and a very low impedance (say around 2 ohms) at high frequencies.

Note that come time for an amp to perform, we want it to be ideally impedance matched to the speaker load it is asked to drive. This will ensure the amp performs with a flat frequency response and delivers maximum power. We know that impedance matching is a severe challenge for tube amps due to the impedance variations a stat load presents to it. In order to help remedy this issue tube amps use output transformers which have impedance (1, 2, 4, 8, 16 ohm) taps on them to allow for a better impedance match. Though helpful, such taps are still a compromise due to the fact that stats do not have constant impedance across their full frequency bandwidth.

As an example. A tube amp will be able to drive the high impedance frequency bandwidth - the midrange and lower highs - of a stat with a flat frequency response. However, at higher frequencies – when the impedance of the stat drops to below the impedance taps used on the amp - we will encounter rolled off the highs to some degree. To minimize this impedance mismatch, one generally uses a lower impedance tap on the amp.

However, there is a (major) problem when you use a tube amp’s lower impedance tap …… the amp’s drive voltage drops proportionally. The lower the tap value the lower the drive voltage.

We know from previously that (when driving a stat) voltage is the #1 key for an amp. So, when you use a lower tap on the amp - to better match the impedance of the speaker – you will have less output voltage to drive the stat speaker properly. And this is not good!
 
Last edited:
Pneumonic said:
A few things to keep in mind, soundacct.

Remember that stats present a mostly reactive (ie capacitive) load to an amplifier and, therefore, operate on volts and not watts. You have to be very careful when looking at an amp’s wattage rating when it is being used to drive a stat panel. Watts is far less important than the amp’s power supply voltage rating! An amp with an inadequate power supply voltage performance will easily clip when hooked up to a stat …. despite its wattage rating.

Also keep in mind that a stat’s highly reactive behaviour means that it has weird phase angles and sends electrical current back to the amp (when signal reverses polarity). Many amps tend to be unstable under such conditions so you need to make sure the amp is stable with reactive loads.

Furthermore, because a stat acts like a capacitor, its impedance is inversely proportional to the frequency it sees. So a stat will have a high impedance (say a couple hundred) at low frequencies and a very low impedance (say around 2 ohms) at high frequencies.

Note that come time for an amp to perform, we want it to be ideally impedance matched to the speaker load it is asked to drive. This will ensure the amp performs with a flat frequency response and delivers maximum power. We know that impedance matching is a severe challenge for tube amps due to the impedance variations a stat load presents to it. In order to help remedy this issue tube amps use output transformers which have impedance (1, 2, 4, 8, 16 ohm) taps on them to allow for a better impedance match. Though helpful, such taps are still a compromise due to the fact that stats do not have constant impedance across their full frequency bandwidth.

As an example. A tube amp will be able to drive the high impedance frequency bandwidth - the midrange and lower highs - of a stat with a flat frequency response. However, at higher frequencies – when the impedance of the stat drops to below the impedance taps used on the amp - we will encounter rolled off the highs to some degree. To minimize this impedance mismatch, one generally uses a lower impedance tap on the amp.

However, there is a (major) problem when you use a tube amp’s lower impedance tap …… the amp’s drive voltage drops proportionally. The lower the tap value the lower the drive voltage.

We know from previously that (when driving a stat) voltage is the #1 key for an amp. So, when you use a lower tap on the amp - to better match the impedance of the speaker – you will have less output voltage to drive the stat speaker properly. And this is not good!
Click to expand...

OK, now we're talkin!

I've got some reading to do I see.
 
One sided argument?

Furthermore, because a stat acts like a capacitor, its impedance is inversely proportional to the frequency it sees. So a stat will have a high impedance (say a couple hundred) at low frequencies and a very low impedance (say around 2 ohms) at high frequencies.
Click to expand...
Pneumonic, you are focusing on the low impedance at high frequencies to argue against the case for tube amplifiers and you're conveniently leaving out the high impedance part. Let's focus on the high impedance at low frequencies for the time being. Let's say that the impedance will be 64 ohms at low frequencies and the solid-state amplifier in question is rated at 200 watts per channel into 8-ohms. This same amplifier will do:
  1. 100 watts into 16 ohms
  2. 50 watts into 32 ohms
  3. 25 watts into 64 ohms
  4. 12.5 watts into 128 ohms
Basically, about 1/10th of its power around the lower male vocal range, if its power supply is robust enough to deal with such a wild range of impedance swing. This frequency range is still considered critical since it falls into the sensitive audible range for human hearing. Just base on this pure fact, the solid-state amplifier does not look too attractive, does it? This is where the output transformers come in to address the impedance swing and the taps are configured as nominal overall impedance, not to be looked at as a narrow range.
The moral of the story? Amplifier topologies means little on paper. You really need to audition the potential amplifier yourself in order to come to your own conclusion. There are excellent products in both camps, and you'll need to trust your own ears!
 
soundacct said:
OK, now we're talkin!

I've got some reading to do I see.
Click to expand...

Mr Sanders described it here pretty good: esl-amp

or here: tubes-vs-transistors

In short: "In short, tube amps can't drive ESLs linearly, cleanly, without clipping, to high output levels. So why put up with all their problems of heat, cost, maintenance, and unreliability when a properly-designed, solid state amp solves all these problems?"
 
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I'm not sure I understand the capacitive load part. Isn't that precisely why there's a transformer inside the speaker? To present the amplifier with a load it is designed to drive and step that up to the very high voltage that charges the panel? If all we needed was good control over high voltages, why bother with all that power? Why not build half an amp and skip all the heavy and expensive power gain stages?

It's because we're trying to get the speaker to do work (make NOISE!! Yeah!), correct? Work takes power...voltage and current are two sides of the same coin.

Though I've killed my share of brain cells between electronics school and now... am I missing something?
 
So,

Do I understand correctly that you recognize the limitations of SET amps and the issues regarding sound quality (low wattage tube amps don't work with ML speakers) but your main desire is to have a tube amp to show / impress your friends and guests when they visit?

GG
 
Gordon Gray said:
So,

Do I understand correctly that you recognize the limitations of SET amps and the issues regarding sound quality (low wattage tube amps don't work with ML speakers) but your main desire is to have a tube amp to show / impress your friends and guests when they visit?

GG
Click to expand...

Nah, Gordon, I think you're focusing too much on the "when guests are over" part . I think I'm not getting my point across...I'm not trying to show off to anyone, I just like to try things. That's just one of many appeals, with no particular importance. If you saw my garage, you'd see all the crazy hodge-podge of projects, just chuckle and understand.

As for showing off? not really my style, but conversation piece? of course. Curiosity about the "tube sound"? sure! Looks cool? CHECK. nostalgia? of course. just plain ol' variety? why not. I do gravitate towards uncommon / unusual & unique things of all types.
May I go out on a limb and gather that you're question is designed to find out what sort of person I am? It's not to put words in your mouth, but I can't help but get that impression.
So let me answer that in story form: The guy that sits next to me at work bought a Rolex...I bought a pickup truck for half that price. I guarantee you that I like my truck better than he likes his watch, and my truck fits me better. Oh...and he keeps asking me to haul stuff for him.
Anyhow, for every reason listed, and just because I plain old just want to try something new...why does anyone want to try anything - I just wanna, thats all. But at this point I am planning on either building a kit or buying a $500 -ish 30 watt unit.
 
Damn..... I have to change my friends for more appreciative group of people....when they come over and I try to explain a reason for my madness they look at me in this funny way, like I just escaped from mental institution....
 
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