Which First Watt Amp for Electrostatic Headphone with step-up Tr? - diyAudio
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Old 14th November 2008, 01:41 AM   #1
rdk845 is offline rdk845  United States
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Default Which First Watt Amp for Electrostatic Headphone with step-up Tr?

Hi All,

I'm planning to build a first watt amp to drive my electrostatic headphone. 1:25 ratio step-up transformer will be used to couple amp and headphone. I prefer balanced amp. Which one of possible First Watt configuraiotn would be the best for this application? For headphone, I won't need more than 10W.

F1 is balanced but I wonder whether it is suitable for dring transformer / ESL.

2 F4 stock can be configured balanced, but it will give me 90W more than I need.

F5 seems to be simplest to make, but I wonder whether it is worth put toghether 2 stock circuit to make balanced.

Please let me know what you think.

Thanks!
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Old 14th November 2008, 04:16 AM   #2
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Why go to all the trouble to build a great amp with and then use a transformer? I would say that the F1 would be ideal for the electrostats and has been reviewed thoroughly on the net. This goes as well for other FW amps. Do a search.
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Old 14th November 2008, 02:06 PM   #3
rdk845 is offline rdk845  United States
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Quote:
Originally posted by khundude
Why go to all the trouble to build a great amp with and then use a transformer? I would say that the F1 would be ideal for the electrostats and has been reviewed thoroughly on the net. This goes as well for other FW amps. Do a search.

Can you comment on why you think F1 would be ideal? Some people say perfect voltage source would be perfect amp for electrostatic. Which First watt amp would be close to that?

Transformer is needed since electrostatic headphones are high in impedance (~100K) and capacitive loads, so step-up transformer is needed to couple with normal speaker amp, unless amp is designed to output hundreds of votlage.

First watt is thoroughly reviewed but those are with dynamic speakers. I saw some sporadic comments that some First watt amps drives electrostatic speakers well, but I don't remember which first watt amp it was...
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Old 18th November 2008, 03:18 AM   #4
rdk845 is offline rdk845  United States
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Any reply?
Here is what I heard about driving electrostatic speaker or headphone. It is the voltage that drive them, not current like dynamic speaker or headphone. But driving them comparatively become difficult since ESL impedance drops rapidly for low and high frequencies, so stiff power supply and good constant current source is a plus. Finally since the diaphram moves in a push-pull way from voltage on 2 stators, push-pull type or balanced type are better.
What would be my best of option for such load. It seems F4 and F5 may fit the bill best, but I don't know which one would be more suitable for such load and neither are balanced.
Thanks.
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Old 18th November 2008, 03:59 AM   #5
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Neither are balanced. Do you mean input balanced or output baalnced?

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Old 18th November 2008, 04:07 AM   #6
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Saying that electrostats are voltage driven applies only if you're driving the panels directly; no transformers. Once you add a transformer to the mix, the situation gets much more complicated. Often, in the real world, you find that electrostatic speakers are some of the worst current hogs you could imagine.
The idea that a push-pull amp is best because the speaker element is push-pull is like those folks who used to claim that a speaker shaped like a violin would reproduce violins better. It's not really relevant.
The defining amplifier characteristics that are best for electrostatic speakers are pretty much the same as for any other speaker:
--You want enough voltage swing to reach reasonable volumes without clipping.
--You want enough current to back up those voltage swings into the lowest impedance that the speaker has to offer.
--You want as low a distortion as you can get and to have what distortion remains be relatively benign in nature, meaning lower harmonics rather than higher.
--Once you've got the above settled, you can begin fretting over how many angels can dance on the head of a pin. I come from the land of tubes, where simple circuits and low rates of feedback prevail. That idea stuck with me when I moved over to solid state. Many other people have come to much the same conclusions, though the roads they traveled varied from mine. Nelson spends a lot of time working on simple solid state circuits, and the First Watt circuits are good examples.
I'd suggest that you determine what your actual load will be. Honestly, headphones probably won't be that bad, but it never hurts to think it through. Are these commercial headphones or DIY?
Balanced circuitry is fine--I like it myself--but don't get hung up on it. There are plenty of other amps out there that will do just fine.

Grey
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Old 18th November 2008, 02:26 PM   #7
rdk845 is offline rdk845  United States
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Thanks for the reply.
Quote:
Originally posted by Nelson Pass
Neither are balanced. Do you mean input balanced or output baalnced?
I meant output balanced. I thought one could do balanced F4 and F5, although for headphone use, 100w would be waste of energy so I will need to learn how to step down those closer to 10-20W.

Quote:
Originally posted by GRollins
I'd suggest that you determine what your actual load will be. Honestly, headphones probably won't be that bad, but it never hurts to think it through. Are these commercial headphones or DIY?Grey
The 25W for Single Ended F4 and F5 should provide more than enough headroom that these headphones will ever need. The headphone is sort of like DIY product, but load wise similar to commercial ones like Stax Omega II. The transformer would be 8ohm speaker side and 25 step-up to headphone side. Initially I will be using those from stax sold in the past for exactly the use I intend to do and they are rated maximum handling power of 8W. Later I will change to some designed for electrostatic speakers, since it should be of higher quality, and they would handle much higher power for headroom. The impedance of headphone would be of order of 120K ohm.

Again Issue is whether which first watt amplifier will bettern handle the varying impedance and current under this transformer + capacitive load of headphone.

I'm interested in Balanced output amp since, Kevin Gilmore who designed great electrostatic headphone amplifiers wrote that coupling single ended with such step transformer poses some problems. regarding specifilcally what problem, I do not know.
Any comment would be appreciated.

Thanks!
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