What amp best for ESL's..?

In the first place, I would like to say hello to everyone, since I am
actually a newbie here...now let's comne to the gist of the matter...
I can't listen to my (Densen B-100) amp anymore. It simply
doesn't cope withe my Martin Logan's. So there's the question...

What schematics...

Beacause now I have a lot of free time, I finally decided to
stop reading and start soldering some stuff, not afraid
of anything more complicated :)

My objectives are :
100 W / 8 ohm 200W/4 (Logans need some power)
Maybe it will sound a little bit stupid, but I want tu use the
best circuit available, not the second best (I mean, in terms
of *objective* sound quality) :cool:


Any Krell schematics, Maybe ML posted in the other thread would be ok..?
What about Erno Borberly Class A modules..? I must admit it appeals to me :)

Any suggestions...?

Thanks!!!

Adam
 
Adam, I have also Martin Logan (SL3) and my advice here is: Use an amp with good ability to handle capacitve loads. Avoid amps with too much foldback current limitation (hard to know that maybe if you don't have the schematics before you buy the amp). My QRO amp can withstand 10 µF without a problem. I'm totally sure of the value. I tested this long time ago. My amp has also "vertical" current limitation (same current independant of voltage).

One other important thing is that the amp has little global feedback in the 1 MHz region and above. See the Leach amp for details.

http://users.ece.gatech.edu:80/~mleach/lowtim/

I forgot: Why don't you take a look at Mr Pass' amps since you are here? I imagine that they can take difficult loads, don't know that though, but I'm sure someone here knows more about it.
 
Yes, JHL would be a nice idea, but I am not sure whether
33 V p-p would be enough for me (I am going to stay in
ESL's family for a while). Please bear in mind that I plan
to buy bigger ESL which are much more power hungry than
orginal Quad's...

I'll ask again - what about some Krell and ML schemas mentioned
in other threads..?

Best regards,

Adam
 

MRehorst

Member
2002-05-17 8:48 pm
Lisandro_P said:
What about the version of the JLH amp for ESL speakers?

http://www.gmweb.btinternet.co.uk/jlhesl.htm


Call me a wuss, but I would not want to connect ANY speakers to a direct coupled amp with no protection circuits. A component failure can easily send the power supply current through the primary winding of the transformer in the speaker. Most transformers won't last very long with a few amps DC running through them.

MR
 
Adam said:
How does your QRO sounds with SL3...?

Hint: I have designed the amp myself. Can you guess?

Right, I am very pleased. The amp is switched on every day(almost), worked like clockwork since 1989. I have the TV connected to my stereo. Martin Logan + digital TV sound(NICAM) is cool.

Later I will make QRO Mark II public, future project (to some people: This is not an add!).

I have a feeling of that ML fits most amps except for those which are sensitive for capacitive load. I have seen a figure about the capacitance, is it 10 nF in ML?
 
MRehorst said:

Call me a wuss, but I would not want to connect ANY speakers to a direct coupled amp with no protection circuits. A component failure can easily send the power supply current through the primary winding of the transformer in the speaker. Most transformers won't last very long with a few amps DC running through them.

I totally agree! What happens when my older MOSFET amp (without DC protection of course) puts + 75 V DC out to my three 5" wideband speakers? Which happened three times!

The speaker will be destroyd in less then 3 seconds, fire smoke! SMELL!:bawling:

My QRO amp has an advanced DC-protection (4th order Tjebutjev at 7 Hz, max DC 1.5 V and response time of <1 second. The protection circuits are fed from a separate PS in order to get an extra safe function but it's possible to feed them from the high driver voltage. +-80 V. This is one more reason to get complex.
 
I don't like more DC through my speakers than the absolute necessary too :) Check Rod Elliot's site ( www.sound.westhost.com ) for a very good relay based output protection. A lot of people diss relays here, but if you're fine with them it's an excellent project which disconnects the output in case of ANY dc failure. Plus, it gives you turn-on and off thump protection (the amp is muted for 3 seconds after turn on and inmediatly after turn off). I don't know how ESL take thumps, but in any case, i like to avoid them whenever's possible :)
If you like the design you could take the original JLH amp (which is capacitor coupled) and modify it on the same manner, but i dunno...

As for the power, yes, the JLH is not a very powerful amp... this depends more on the sensitivity of your speakers. My (regular) JLH does almost 20w on a couple of 90db/w and i NEVER needed full power through them, not even near. It's a sweet, very "tube-sounding" amp, and right there in the class-a hall of fame with Pass amps and others!
 
Hello everyone!
Yeah, the idea with protection circuitry is good, I would even say
that extra safety is obligatory when used ESL's.

That's right, Peranders, ML will be a party animal at 20-30 W.
And the capacitance isn't so very hight (but still much higher
than in most *conventional* speakers).
Currently, I am using
an amp with 60W/8 ohm 110W/4 ohm. I never actually needed
the full power. However, it doesn't have the 'right' sound with
ML.
I feel the true reason is, well yes - the capacitance.
I was wondering what's going on till I saw a test somewhere,
which gave every indication that my Densen would ossicalte
at capacitive loads.
The other aspect is bass. I feel thas as long as the ESL panel
working from few hundreds Hz up reguires a stable amp, the
RockfordFosgate bass driver requires some serious WATTS
as well as control in bass area.
That's why looking at some big-power-regulated-whatever
amps makes me drool.

Please remember that ML uses a sealed bass enclosure,
so the lowest frequency spectrum is very controlled, but on the
other hand shows how amp behave in that region, so...

As told, it will sing at 20-30 W. The question is how will it sing...

ps. sorry guys it something in this post was of the topic, I just
woku up :eek:

Best regards,
Adam
 
quote

Yeah, the idea with protection circuitry is good, I would even say that extra safety is obligatory when used ESL's.

what's so special about ESLs? if anything they're quite immune to DC. The step-up will take many amps before it sizzles and the primary's wire is way thicker than any speaker coil. Plus it's likely fused.
where you really need to be careful is with high efficiency full range drivers.
does anyone have recommendations for a relay that doesn't screw up the sound too much?

peter
 
analog_sa said:
what's so special about ESLs? if anything they're quite immune to DC. The step-up will take many amps before it sizzles and the primary's wire is way thicker than any speaker coil. Plus it's likely fused.

I don't know how or if the transformer is fused but the woofer(Martin Logan) is a ordinary speaker which don't like DC.
 
My high voltage esl amp is for driving esl headphones directly
without a transformer. It is good for about 1200 volts of
differential swing. It does not have sufficient drive to directly
drive a quad or any other esl speaker however. I do have
a schematics of a few direct drive tube designs that work
great for the purpose.

In all cases you remove the input transformer.