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In article ,
tony sayer wrote:
In article , Dave Plowman (News)
scribeth thus
In article ,
Fredxx wrote:
On 21/04/2019 00:15, Dave Plowman (News) wrote:
In article ,
tony sayer wrote:
I can't be certain the Behringer unit is faulty. The amplifiers
are home made, and it could be some interaction I've not fathomed
out.


Right!, so the crossover then goes to some home-brew amps if so
what are they and are they bal or unbal inputs?..

Balanced. Using THAT1240 ICs. The whole idea being to avoid ground
loop problems...


They have some serious CMRR.


I doubt the X/O has anything like that?


I didn't recognise the number on the balance ICs in the X/O.

I have loads of SSM 2143 I could try, though, on the amp. But I've not
had problems with either before.



Wouldn't surprised if they were pin compatible!..


They are. I was led to believe the THAT had a better performance than the
SSM.

Because the cable run is so short, I've just used the most basic
circuit for the THAT1240.

But

It really shouldn't matter those sorts of chip can take balanced lines
up to miles long if need be!..


Quite. I've used them for lots of things with no problems. I have 5 stereo
pairs of audio running round the house. Cable is multicore telephone cable
- no screens at all. Driven by SSM2142, and picked up in several locations
by either SSM2143 or THAT1246. Can have 8 sitting across the same line
with absolutely no problems at all.


I've got/getting rather then theres something odd with the power supply
for these somewhere?..


Can you describe it in more detail?..


Mains ground goes to the closest chassis point. All the DC grounds and
signal grounds go to a star ground point which is in turn grounded to the
chassis at only one point.

--
*Just give me chocolate and nobody gets hurt

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

In article , Dave Plowman (News)
scribeth thus
In article ,
tony sayer wrote:
In article , Dave Plowman (News)
scribeth thus
In article ,
tony sayer wrote:
I can't be certain the Behringer unit is faulty. The amplifiers are
home made, and it could be some interaction I've not fathomed out.


Right!, so the crossover then goes to some home-brew amps if so what
are they and are they bal or unbal inputs?..

Balanced. Using THAT1240 ICs. The whole idea being to avoid ground loop
problems...


They fed by a + volt and a neg volt supply centre tapped or floating do
you know?..


Of course I know. I built them. ;-) +/-15v.


So transformer - separate windings- bridge rectifier- single three pin
Voltage REG pos and neg points connected to appropriate pins and other
ends come to a central earth or rather 0 Volt point?..???




http://www.thatcorp.com/1240-series_...iver_ICs.shtml



--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.


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Default Electronics funny.

In article ,
tony sayer wrote:
They fed by a + volt and a neg volt supply centre tapped or floating do
you know?..


Of course I know. I built them. ;-) +/-15v.


So transformer - separate windings- bridge rectifier- single three pin
Voltage REG pos and neg points connected to appropriate pins and other
ends come to a central earth or rather 0 Volt point?..???


Not quite.

The amp PCBs include the balance IC. The +/- 15 v derived from the amp
+/-50v. Same as Quad used on the 405 PCB for their op-amp.

--
*Don't squat with your spurs on *

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

On Sat, 13 Apr 2019 13:00:37 +0100, "Dave Plowman (News)"
wrote:


Difficult to tell if the buzz is from all three speaker units, as when you
get your ear close enough to each one, it stops.


A similar problem of detecting which of a number of speakers was
producing sound from a device which changed characteristics when you
approached it was diagnosed by a length of hosepipe taped near the
device on one end and held near the observers ear at the other so you
could listen closely without interfering with the equipment. In that
case the problem was with the infamous Sinclair X10 broadband jammer
which altered its characteristics as someone across the street moved
around their lounge.



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In article ,
Peter Parry wrote:
On Sat, 13 Apr 2019 13:00:37 +0100, "Dave Plowman (News)"
wrote:



Difficult to tell if the buzz is from all three speaker units, as when you
get your ear close enough to each one, it stops.


A similar problem of detecting which of a number of speakers was
producing sound from a device which changed characteristics when you
approached it was diagnosed by a length of hosepipe taped near the
device on one end and held near the observers ear at the other so you
could listen closely without interfering with the equipment.


Yup. Bit the same as balancing twin SU carbs. ;-)

But in this case anything seemed to stop the buzz as you got it near.
Which was what was so odd - I've never come across anything like it on
audio gear. That was with the XLR screens floating at one end. Connecting
them made the buzz permanent. And it was coming from all three speaker
units. Removed the mains ground from the X/O, silent as the grave. ;-)

In that
case the problem was with the infamous Sinclair X10 broadband jammer
which altered its characteristics as someone across the street moved
around their lounge.


--
*Does fuzzy logic tickle? *

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


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On Sat, 20 Apr 2019 15:18:48 +0100, "Dave Plowman (News)"
wrote:

In article ,
tony sayer wrote:
Quad at that time only grounded the pre-amp. Everything else had two
core mains leads. Using 110v mains plugs. ;-)


There is IIRC a 2.2 Ohm ressy in the quad to prevent that problem if a
three pin mains lead of the IEC type is used


Can I ask where that 2.2 ohm resistor went?

Hopefully up the back passage of the courier.
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