Tube amp and electrostatic speakers.

[specialx]

To bring this topic out of the grave, which I thought would be better than starting my own thread, I have a question but first my situation.

I am in the process of building a pair of ESL's at the moment, and I will need an amp to drive them for normal use, other than my Technics amp at the moment, which is a great party boomer but hardly classified as hi-fi.

Now for the question, can a tube amp skip it's step-down transformer and the ESL skip it's step-up transformer and just use one smaller ratio step-up transformer?

I have looked at OTL amplifiers and I am not sure if these are the same as directly-coupled amplifiers but they still seem a bit too dangerous for me as I am new to this game as directly-coupled amplifiers do (stressfully pointed out by Ultranalog, thanks ).

-Mike

 

[ultranalog]

Now for the question, can a tube amp skip it's step-down transformer and the ESL skip it's step-up transformer and just use one smaller ratio step-up transformer?

I don't see why not. You'll probably have to order a custom wound and cough up serious dough for a good one.
Remember though, that the ESL capacitance is multiplied by the square of the Xformer ratio and hence you will need a stable amplifier. Since the ESL is more a capacitor than a resistor, power is what gives you bandwidth. By determining the capacitance of the ESL and applying Q=C*V or C*V = I*T, you can derive how much power you need for a certain bandwidth.

(stressfully pointed out by Ultranalog, thanks ).

You're welcome! I sure am glad you took the advise to heart. Remember however that all tube amps can kill. 1250V though is really agressive and can even be harmful at a distance (I've seen it shoot capacitors across the room).

Regards,
Remco

 

[jan.didden]

Re: Active crossover

Active crossovers are the worst things of audio electronics.
Any high-pass filter significantly increases the crest factor of a musical signal(this is apparently not the sine wave). The sharp spikes enter the input of the power amplifier and overload it. Active crossovers often result in harsh and dirty sound. Their use in professional sound reinforcement systems is often dictated by the complex driver matching problems includind time alignment. For the latter purpose and the simplicity of adjustments they often operate in digital domain.
For QUAD ESLs it is essential not to omit their own passive crossover and not to split it for biamping! The best amplifier will be a classical pentode push-pull one rated at least at 10-15 watts. You may look for a circuit like QUAD II.
THe wideband output transformer is not a problem if properly designed. I think any attempt to drive the electrostats directly from the tubes will result in complex and far more expensive circuit, and the sonic benefits will be obscure.
I also do not recommend SET amplifiers with any kind of capacitative load.
Sorry, but you will spend at least $200 for just a pair of acceptable output transformers.

Hi Denis,

I just happened to stumble on your post, wasn't following this thread.
I fully agree with your comments to keep the passive xover of the QUAD ESL's. They are fundamental to the speaker performance.
What I don't get is your comment on the crest factor from a high pass filter. Presumably the spike you refer to is the hi-freq component of the music signal?

Cheers, Jan Didden

 

[fdegrove]

ESL + OTL

Hello,

I have looked at OTL amplifiers and I am not sure if these are the same as directly-coupled amplifiers

I don't think anyone meant OTL as direct coupled here.
OTL's do couple the output tubes directly to the dynamic family of speakers.
They are no more daunting to make then any other amplifier IMO and in that case you could opt for a more conventional xformer to use with your ESL speakers.

Best regards,

 

[specialx]

A recommendation?

Anyone know of any good amplifiers for driving ESL's?
http://www.worldaudiodesign.co.uk/taps.html from that URL I am unsure which amp would be suitable if any.

This amplifier looks nice both from a price perspective and feature perspective as it also is a preamp to itself saving some money as this is my first ESL project I don't want to be coughing up too much money.
http://www.worldaudiodesign.co.uk/wadproducts/kel84.html

Any comments, suggestions?

I am based in Australia as my info on the elft says so perhaps even any locally available kits?

 

[fdegrove]

ESL

SpecialX,

This amp has been commented on before in this section.I think it was Rarkov asking about it.
All I can say is that it will drive your ESL speakers adequately and not break the bank.
Do not expect ear shattering levels from it though.

Rgds,

 

[specialx]

Can anyone recommend any tube amplifier kits suitable for driving ESL's? Doesn't have to be a super high quality setup, as these are my first pair of ESL speakers and it would be pointless to jump ahead of myself.

http://www.worldaudiodesign.co.uk/wadproducts/kel84.html
This kit looks good for the price, and it is also a preamp to itself thus saving me costs of another project, as I am also anxious to get this actual setup working.

Or any local Australian tube amplifier kits would be better, or schematics with not so expensive/hard-to-find parts.
Most kits I found are too expensive for me, I guess my budget is about $350-$400USD

-Mike

PS: Can someone delete the above post... my proxy has been playing up here at work and it said to me the last post didn't go through. Sorry about that.

And thanks fdegrove... I will give them an email and see what happens.

 

[fdegrove]

Hi,

Your proxy was upsetting mine simultaneously.Strange.
Got all fuzzy,nothing crashed though.

Rgds,

 

[specialx]

Proxies suck ***.

But on topic, I emailed them, read the thread by Rarkov and I think I will get it. At $684AUD that's just two weeks pay with $$$ to spare to finish my ESL speakers. Bye-bye idea of buying a car anytime soon!

Thanks for the help however
Best regards
-Mike

 

[Denis]

Re: Re: Active crossover

Hi Denis,

I just happened to stumble on your post, wasn't following this thread.
I fully agree with your comments to keep the passive xover of the QUAD ESL's. They are fundamental to the speaker performance.
What I don't get is your comment on the crest factor from a high pass filter. Presumably the spike you refer to is the hi-freq component of the music signal?

Cheers, Jan Didden

Yes, the crest factor increases at the output of the high-pass filter due to its differentiating action. This means the total energy of the audio signal redistributes between LF and HF regions. For instance, the derivative of a square wave is just two sharp spikes corresponding to front and trail edges of it. The low-pass filter, in contrary, reduces the crest facor of complex audio signal bringing it close to 3 dB i.e. that of sine wave. If one compares the waveforms of the input signal and that passed through a high-pass filter, the amplitudes of those transient spikes will be at least the same, while the RMS value of the highpass-filtered signal will be obviously lower. But the amplifier is to be chosen to pass through these peaks without clipping.

Cheers, Denis Afanassyev.

 

[yup]

pentode or triode

I am working on a set of custom ESL's which I plan to drive with an old Marantz 8B (6ca7's if I recall correctly). My question is should I run it in pentode or triode mode?

Thanks,
Jeff

 

[fdegrove]

SAUL MARANTZ

Hi,

Either way should work but will:

-sound different from each other.

-depending on the effeciency of the ESL you may prefer the more powerful penthode mode.


Ciao,