| amplifier class - Click HERE for Original Thread |
| willyhoho |
I am looking for a amp to drive my esl. I am confused when looking in this forum as to the class designation the amp should have. Can someone please clarify this? Do tube amps have different classes too?
Thanks |
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| SkySeeker |
I am just a beginner on this forum, but it is my impression that Class-D amplifiers are best suited to ESLs.
For example the Hypex (http://www.hypex.nl) modules use a 90V supply voltage, which means that in most cases a 1:50 audio transformer should be sufficient.
Also the output of a Class-D amplifier (see here: http://sound.westhost.com/articles/pwm.htm) needs a capacitor. So the ESL will be just an capacitor parallel to the internal capacitor of the amplifier. |
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| arend-jan |
Yes, tube amps have different classes too. Google a bit and you will find enough info about different classes and what it means.
I'm having good success with a push-pull class A tube amplifier and ESLs. |
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| willyhoho |
| I did not realize there was so many classes of amplifiers.I did some surfing and found more info (some confusing) on amps and I thought a amp was a amp. Thanks for the replys. Some say you can't go wrong with a class AB. I will do more research. |
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| AndrewT |
Hi,
when Quad brought out their SS amp specifically designed to power their ELS they used ClassAB.
All their subsequent SS designs suit the ELS and ESL and still they are ClassAB, but with a funny feedback system called current dumping.
That must say something. |
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| arend-jan |
I had the best results with tubes in push-pull running deep into class A.
I'm running my Quad ESLs with this http://www.nutshellhifi.com/triode1.html DIY PP 300B amp and I can say that it sounds much better than the Quad 303 or 405. No doubt about it. |
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| willyhoho |
| I heard a AMC tube amp today and I think it was a Class A.What a clear,distinct sound. If the amp has no Class designation on the back,is there another way of telling?Age maybe? |
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| AndrewT |
Hi,
Solid state ClassA get so hot you can tell it's not normal bias ClassAB.
There are a few high bias ClassAB around but these usually have heatsinks that get warm to hot due to their smaller size.
Tube/valve amps are difficult to tell apart.
But our tube experts could probably tell from the valve type and B+ voltage. |
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| Few |
I too am looking for an amp for ESL's. My venerable B&K ST-140 amp, which I was using to drive my ESL's, died last week---at the same time that my DEQ2496 decided it was no longer interested in turning on. I haven't yet figured out what happened in this chain of events, but I find I'm in the market for another amp to drive my ESL panels. I'd rather stick to solid state and not spend a fortune. Have any class D modules been shown to be particularly cost effective and suitable for ESL service? Or as a more conventional (and less diy) alternative has anyone tried either the Behringer EP1500 or A500
amp? I've read some positive things about them, and the price is certainly right. I understand they can handle a low impedance load, but I haven't seen anything about their ability to drive a highly reactive load. Also, I have a feeling the Behringer DEQ2496 brought about the demise of my old amp so I'm a bit wary of Behringer at the moment. |
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| Calvin |
Hi,
I can wholeheartedly recommend the HiFi-Akademie amps.
They are a stereo class-d pre-filter-feedback concept for DIY. So freq-response depends on the speakers impedance, but filter components can be easily tuned to suit Your demands.
Capacity (as ESL-manufacturer) recommends and uses them with his panels and they have proved to work exceptionally stable with my panels, which are a real proof with low impedance values and phase angles reaching more than 80°!!! B&Os Ice-Power-modules are for example not specified for the capacitive loads that typical ESLs represent and would start swinging with my panels (or ML-Panels)
I like that the H-As are built with a very straightforward simple signal-path and allow for higher currents than most other designs in their wattage-class. Price is similar to UCDs with Power-supply and You can purchase nice housings too.
Up till now their sonic performance in my setup was just topped by the enigmatic KR-Audio Kronzilla...at slightly elevated costs of course ;) Price/Performance-value is very good.
As an interesing feature it is equipped with a slot where You can put optional crossover modules in (analog as well as digital). So You can easily create a fully active 2way ESL-version.
jauu
Calvin |
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| Capaciti |
Hi Folks,
Calvin i fully agree !
take a look here, unfortunately just german language.
www.hifiakademie.de
Capaciti |
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| Few |
| Thanks for the info Calvin. Now I just need to brush up on my German so I can read their site (it will actually take more than a brushing up...). I've emailed HiFi Akademie to ask if they have any information for those of us who are linguistically challenged. I've found the online language translations to be pretty cumbersome. I sure wish I had paid more attention in my German classes all those years ago! |
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| SkySeeker |
Calvin, I read somewhere that H-A will also have a project with DSPs. Do you know anything about this?
<dreaming>
I would be overjoyed if H-A would do a class-D with integrated DSP.
I.e. digital in, EQ and Xover with DSP then feed digitally into a class-D.
</dreaming> |
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| Calvin |
Hi,
I know nothing definite, but as You said, a digital crossover module is said to be short before release.
jauu
Calvin |
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| Capaciti |
Hi Folks,
in germany its not a secret that Capaciti works together with HiFiAkademie.
I have some information about the upcoming (in November) DSP-modul:
1. 2 analog inputs, 2 analog outputs
2. The DSP is rather small since it got no own power supply.
3. The modul can only be used in combination with their Preamp or poweramp. You just stick it into an excisting slot, thats it
4. I have moduls in use in my company for testing. I need to say that the outstanding options of such moduls by far exceed the possible losses, which people mention when discussing about A/D - D/A conversion.
5. Using DSP for "standard" loudspeakers is fine, using it for ESL is the perfect match.
6. For example our "Element 160" which is a small Fullrange ESL shows a fundamental resonance between 35 -40 Hz. And as a principle of small baffle width and limited membrane area ii plays "lean" in the lower midrange. Using the Dsp you lift the lower midrange resulting in significant more volume and body. In addition you set a perfect notch to the resonance, which will increase max soundpressure significant.
7. You connect the modul to the parallel port of a PC and do the programming by software. It shows you anything and you can load excisting graphs of measurements.
Out of my experience there are DSP's which really compromise sound quality at all, but the HiFiAkadamie is close to just a wire connection of components!
It might appear that i "glorify" their components due to my business connection, but if you would read all the feedbacks in different german web-chats, you will know why.
Capaciti |
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| SkySeeker |
Thanks Capacity,
Considering that a class-D amplifier is not really a D/A converter, having the DSP as a drop-in solution seems ok to me.
[Note: A feedback loop in the class-D would necessitate an A/D if it were to use a digital input]
A DSP in a class-D sounds great. I am looking for something like that but will wait for november :-) |
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| GRollins |
| quote: | Originally posted by willyhoho
I am looking for a amp to drive my esl. I am confused when looking in this forum as to the class designation the amp should have. Can someone please clarify this? Do tube amps have different classes too?
Thanks |
It appears that this thread has accumulated a great deal of speculation, but not much in the way of actual response to the original questions.
1) There's not a class that an amplifier "should" have in order to drive electrostatic speakers. Any of them can do the trick.
2) The most common classes are A, AB, B, and D. Yes, there are others, but those four cover 99.999% of the commercial amplifiers on the market. In case you were wondering, yes, there is a class C, but it's only of use for radio transmitters; it's not something you'd want to use as a high fidelity amplifier.
3) Tube amplifiers have classes, too. A, AB, and B. It's technically possible to have a class D tube amp, but why on Earth would you want to?
4) Class A is the best from all sonic points of view, but it runs much hotter, is larger and heavier, and costs more.
5) Class AB and class B each have their adherents, but they argue endlessly over the crossover distortion (when one set of devices hands the signal over to another set of devices and turns off) and other technical points that may or may not interest you. In general, it's better to have as much class A as you can get, so in a race between a class AB amp and a class B amp, I'd favor the class AB.
6) Class D? Well, let's see, they're lightweight, often cheaper, run cooler...and there we run out of benefits. Sound quality? If you put music in, sound will come out, but I don't know of a single critical listener who would take a class D over A, AB, or even B. The technology just isn't ready for prime time. On the other hand, if you're just looking for a lot of cheap watts so you can get loud, maybe they're the ticket. But if someone gave me one, I'd use it for background music in my shop, not in my audio system.
7) DSP is conceptually seductive, but not quite ready for high end use. The same thing can be accomplished with analog circuitry, albeit with a little more work on the part of the user.
8) Class D and DSP together? Shudder... I've got sandpaper in my shop. It would be cheaper and simpler to scrub my ears with 100 grit rather than go to all the trouble and expense to put those two together in a high fidelity system.
Grey |
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| Few |
In case other non-German speaking audiophiles are considering the class-d Hi-Fi Akademie products to drive their ESLs I thought I'd pass on the response I received from them when inquiring about product information in English. Perhaps others with more experience with the amps can offer an opinion about whether they would be a reasonable option even without access to the information. Based on this response it doesn't sound promising.
| quote: | I have all documentation in German only. Currently I have no plans to make an English version available. Whilst I could provide you with a price list and brief product information, this would probably not help much because you would also need the remaining information to actually build and operate the amps.
Thank you for your interest and apologies that I cannot help you further.
Best regards
Hubert Reith |
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| Tosh |
If they made everything available in English, they would experience explosive growth in interest, and that would kill their reputation from the negative word-of-mouth due to the backlog. A fledging company needs very controlled expansion, so let's give them some time...
Or is there more behind their reasoning? (This goes for Capaciti-DIY also?) |
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| Few |
| Emails and postings are notoriously easy to misinterpret. In fact, I may be misinterpreting Tosh's. Just to be clear, it was not my intent to impugn the folks at Hi-Fi Akademie. They responded politely and promptly to my question and I'm sure they have good reasons for their policy. I was just passing on the message I received from them in the hope it might save someone else the trouble of emailing Hi-Fi Akademie---and save Hi-Fi Akademie the trouble of responding again. |
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| Kontra |
Greetings
I read here 1 year
I have built the panel the sizes of 1000 mm * 700ėė
Backlash of 5 mm + 5 mm
Coverage of stators - teflon
The film - mylar 8 micron is covered with graphite and from above pool nylon
Tried to use the transformer. It was not pleasant to me.
Whether who has the amplifier on tube without the transformer on an exit?
Direct-coupled the amplifier.
If for whom such is - tell more in detail.
Whether who uses the amplifier of class D direct-coupled?
Whether who knows about the transformer of impedances?
I ask to excuse for my the poor English. My basic language - Russian.
Andre from Russia |
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| Calvin |
Hi Andre,
To make sure I understood You right:
- Your panel is of size 1000x700m and has a membrane-to-stator distance of 5mm?
-- If so, 5mm (+-5mm=10mm stator-stator) is far too much!
Reduce the distance to less than 2.5mm (e.g. +-2.5mm=5mm).
The distance is far too great to get acceptable results!
- Teflon is not the best material as insulator for ESL-stators!
-- It has a too high value in resistivity and a too low value in dielectric constant. Materials like PVC, Nylon, Polyurethane, Acrylics are better.
- Do You mix graphite and Nylon as coating for the membrane?
-- My experiences with graphite were rather disappointing, though some readers report successful usage of the stuff. I havenīt tried the Nylon and will not, because to my taste it adds to much mass and there are too many negative reports on that material (some people tried hard to get a working emulsion, but failed constantely). I prefer easier to handle materials which are not poisonous or smelly and that can be tuned in resistivity and -if needed- can be coated on a second or third time, and that can be brushed on or sprayed.
Using a transformer as coupling device between amp and ESL is the easiest way. and I recommend this way for every beginner!
But to function correctly the transformer needs to fullfill strikt requirements. You canīt just use any transformer simply because it has 2 or 3 windings on!
To get an idea what transformation-factor would be needed I calculate or measure the capacitance of the panel and calculate the impedance value at 20kHz. Now I take the square root of this impedance value. This value equals the transformation factor of the transformer. Connecting the transformer with the calculated value means that this results in an impedance of 1Ohm@20kHz (theoretically, in practise itīll be more). This is the lowest value Iīd recommend.
Now estimate how much drive voltage Your panel can take. Assuming ~2kV/mm as flashover treshold for air, a panel with 10mm stator-stator distance would need 20kVpp=7kVrms. A typical amp will push out about 20Vrms to 35Vrms. So we need a transformer with an transformation factor of 200 to 350 here!!!
A panel of 1000x7000x10mm has a calculated capacitance of just 620pF. This translates to ~12.8kOhm@20kHz. Taking the square root we get a transformation factor of 113. This is just half of what is needed.
It is much easier to reach the high voltages needed in an ESL with an transformer than with a direct coupled amplifier. Only small headphones could be driven directly by connecting the panel to the Anodes of the output tubes. Larger panels need higher voltages, so that a specially designed amplifier is needed that works with plate voltages of 2kV-5kV. Still these amps are more suited to drive hybrid-ESL-panels rather than FullRange-ESL-panels.
At this time direct coupled D-amps are ot of range. There are no such fast output devices (in solid state) that can withstand such high voltages and besides the switching transients would be a great problem (interference with radio). I havenīt seen a direct coupled high voltage tube class-d amp yet.
So Andre, if I understood Your infos about Your panelīs dimension right, I can only suggest You to rebuild the panel using much less distance between the stators. If (as example) You use a distance of 3mm (+-1.5mm) the panel would show a capacitance of ~2nF. That translates to an impedance value of 3.85kOhm@20kHz.
Square rooting gives a value of 62.
A pair of standard toroidal power transformers of ~100VA rating and 230V/6V (6V-winding connected in parallel, 230V-windings connected in series) will result in a transformer with an factor of ~1:65 to 1:70 (depending on the losses of the trannies)
The panel will be able to take a signal voltage of 6kVpp = 2.1kVrms before flashovers occur.
The amplifier will have to supply up to 32Vrms (just slightly more than 100W@8Ohms). As an example a UCD180 could be of interest here!
The panel would be useful above ~200Hz and should be augmented with a subwoofer! This hybrid ESL will yield very high SPLs (~120dB@4m should be realistic!) with low distortion (most of the distortion will be produced by the transformers) without demanding excessive power!
jauu
Calvin |
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| Kontra |
You right:
in my panel distance a membrane to stators - 5 mm and distance stator to stator - 10 mm
Teflon I use as a covering of metal (steel thickness of 1 mm R3V4) instead of a paint thickness of a covering of 10 micron
I apply teflon to apply a variable voltage between plates stators in size 8Kvolt - 10 Kvolt and a voltage I submit on a film 12Kvolt constant
The big distance between plates stators is made that the film at moving on frequency 40 herz did not touch stators at me there is no in the panel of crosspieces (supports) I made the low-frequency panel. That the full range I sounded has made 2 small panels of 500 mm * 300 mm that they radiated high and average frequencies
I Tested the panel with the special DIY transformer. At my handmade transformer the secondary winding is divided{shared} into 6 parts to reduce capacitanse between windings. To receive the necessary variable voltage I has connected such 2 special transformers. Initial windings in parallel and secondary it is consecutive. Thus the secondary winding of my common transformer will consist of 12 parts. A material of the core - special amorphous steel. Not crystal structure of metal
Whether means your text, what you did not do{make} never lamp direct-drive amplifer?
To be as much as possible understood I is compelled to write shortly and primitively. Therefore not diplomatic. But it is not rough. I polite.
Again I want to ask - whether who did{made} the amplifier with an anodi voltage 15 Kvolt?
About coating:
First I have rubred with graphite a film, have washed off surpluses isopropanol spirit, have then measured resistance. Measured a current between two copper coins as the "fathers founders" learned. Rehorst for example.
Then I have covered a graphite grid with liquid nylon (a solution in phenol)
Sorry for my pimguin and non diplomatic eng |
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