ESL57 - a difficult load?
 

I rescued a Rotel RA930AX amp from the junk shop.
The manual says:
"Do not use speakers that have a very high capacitive load,
say over 0.1 microfarads, as it may cause a damage to the
power amplifier section."

So I shan't be connecting it to my ESLs.
Any idea what would happen?

--
Eiron.

ESL57 - a difficult load?
 

Probably the output transistors would go short circuit followed by the
fuse(s) blowing. However, there wouldn't be much chance of this in practice
unless you drive the amp with a square wave at high power. Also, it's
probably OK with Quad ESLs as according to this link
http://user.tninet.se/~vhw129w/mt_au...uad_repair.htm they're only
568pF capacitance.


"Eiron" wrote in message
...

I rescued a Rotel RA930AX amp from the junk shop.
The manual says:
"Do not use speakers that have a very high capacitive load,
say over 0.1 microfarads, as it may cause a damage to the
power amplifier section."

So I shan't be connecting it to my ESLs.
Any idea what would happen?

--
Eiron.

ESL57 - a difficult load?
 

In article ,
SteveB sbrads@nildramDOTcoDOTuk wrote:
Probably the output transistors would go short circuit followed by the
fuse(s) blowing. However, there wouldn't be much chance of this in
practice unless you drive the amp with a square wave at high power.

Heh heh. Remember blowing up a then new NAP 250 when driving '57s. Julian
wasn't impressed when I postulated it was sold as a pro amp.

--
*Sorry, I don't date outside my species.

Dave Plowman London SW
To e-mail, change noise into sound.

ESL57 - a difficult load?
 

On Mon, 14 Mar 2005 19:22:54 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
SteveB sbrads@nildramDOTcoDOTuk wrote:
Probably the output transistors would go short circuit followed by the
fuse(s) blowing. However, there wouldn't be much chance of this in
practice unless you drive the amp with a square wave at high power.

Heh heh. Remember blowing up a then new NAP 250 when driving '57s. Julian
wasn't impressed when I postulated it was sold as a pro amp.

It's not nice to speak ill of the dead, but Julian Vereker was an
incompetent arsehole who couldn't design his way out of a paper bag.
He crapped his frilly knickers when the warranty claims started coming
in for the NAP250, in the era when Litz wire was first touted as the
ultimate speaker cable (which, theoretically, it is).
--

Stewart Pinkerton | Music is Art - Audio is Engineering

ESL57 - a difficult load?
 

"Eiron" wrote in message
...

I rescued a Rotel RA930AX amp from the junk shop.
The manual says:
"Do not use speakers that have a very high capacitive load,
say over 0.1 microfarads, as it may cause a damage to the
power amplifier section."

So I shan't be connecting it to my ESLs.
Any idea what would happen?

**Actually, you're likely to experience fewer problems with the Rotel, than
with most other amps. I am a Rotel service agent and part of the testing
procedure I use on ALL amps (except Naim of course) is to connect a 1uF cap
across the load, to check for instability issues. Rotels do not exhibit
problems.


--
Trevor Wilson
www.rageaudio.com.au

ESL57 - a difficult load?
 

"Trevor Wilson" wrote in message
...

"Eiron" wrote in message
...

I rescued a Rotel RA930AX amp from the junk shop.
The manual says:
"Do not use speakers that have a very high capacitive load,
say over 0.1 microfarads, as it may cause a damage to the
power amplifier section."

So I shan't be connecting it to my ESLs.
Any idea what would happen?

**Actually, you're likely to experience fewer problems with the Rotel,
than with most other amps. I am a Rotel service agent and part of the
testing procedure I use on ALL amps (except Naim of course) is to connect
a 1uF cap across the load, to check for instability issues. Rotels do not
exhibit problems.

**Typo alert! Sorry. That would be a 0.1uF cap.


--
Trevor Wilson
www.rageaudio.com.au

ESL57 - a difficult load?
 

Trevor Wilson wrote:

I rescued a Rotel RA930AX amp from the junk shop.
The manual says:
"Do not use speakers that have a very high capacitive load,
say over 0.1 microfarads, as it may cause a damage to the
power amplifier section."

So I shan't be connecting it to my ESLs.
Any idea what would happen?

**Actually, you're likely to experience fewer problems with the Rotel,
than with most other amps. I am a Rotel service agent and part of the
testing procedure I use on ALL amps (except Naim of course) is to connect
a 1uF cap across the load, to check for instability issues. Rotels do not
exhibit problems.


**Typo alert! Sorry. That would be a 0.1uF cap.

Thanks. So it's a power issue rather than instability.
I have mislaid my ESL handbook but I seen to remember that
it presents a similar load to 16ohm in parallel with 2uF.
It should be OK if I keep the volume down.

--
Eiron.

ESL57 - a difficult load?
 

In article , Eiron
wrote:
Trevor Wilson wrote:

I rescued a Rotel RA930AX amp from the junk shop. The manual says:
"Do not use speakers that have a very high capacitive load, say over
0.1 microfarads, as it may cause a damage to the power amplifier
section."

So I shan't be connecting it to my ESLs. Any idea what would happen?

**Actually, you're likely to experience fewer problems with the Rotel,
than with most other amps. I am a Rotel service agent and part of the
testing procedure I use on ALL amps (except Naim of course) is to
connect a 1uF cap across the load, to check for instability issues.
Rotels do not exhibit problems.


**Typo alert! Sorry. That would be a 0.1uF cap.

Thanks. So it's a power issue rather than instability. I have mislaid my
ESL handbook but I seen to remember that it presents a similar load to
16ohm in parallel with 2uF. It should be OK if I keep the volume down.

The matter may be more complex pun :-) that that...

A model of the impedance of the ESL57 is described on the 'Audio Misc'
pages on the 57 and 303. IIRC It was common to test amps for suitability by
using a load like 8 - 16 Ohms shunted by 1 - 2.2 microF. However sometimes
*smaller* capacitances might invoke instabilities which don't appear with
large capacitances. Hence unless the amp is specified as 'unconditionally
stable' there might be a risk.

Slainte

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html