Just curious about these - how were they used? All that is known is they
came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me, from
surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
diameter. Some sort of multiple series and parallel for 2 ohm etc or with L
and C for speaker simulation ?

On 6/23/2010 3:48 AM, N_Cook wrote:
Just curious about these - how were they used? All that is known is they
came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me, from
surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
diameter. Some sort of multiple series and parallel for 2 ohm etc or with L
and C for speaker simulation ?



Nigel,

To me 2.8 ohms is an odd value. I have DALE 8 ohm 250 watt, non
inductive winding resistors. With four of them, I have 8 ohms at 250
watts, or 4 ohms at 500 watts. If I had felt the need I could have done
some more complicated switching and also had 16 ohms at 500 watts.

They are very useful as you can hook them up as a dummy load and view
on your scope, and run rather large amp right up to clipping, all while
not having to listen to any of it. It also makes it easy to measure
power at clipping, as long as you also monitor your mains voltage. (At
clipping, you have to watch the voltage drop at your bench outlet, as
you might be feeding the amp a lower mains voltage than it is specified
for, which will reduce power output. I have a VARIAC to correct for this.)

I have seen one manufactured unit that used 7.87 ohm resistors, as they
figured out the resistance of the wiring and switching. I put together
my own, and did not feel the need for that level of accuracy.

The loads that I have are resistive, so not as difficult to drive as a
speaker might be, but again, good enough for my needs.

You did not specify the make or model of the resistors, or how they
were wired up.

Regards,
Tim Schwartz
Bristol Electronics

On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook �ʇoɹ�:

Just curious about these - how were they used? All that is known is they
came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
from surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
diameter. Some sort of multiple series and parallel for 2 ohm etc or
with L and C for speaker simulation ?

Most newer SS amps are rated to a minimum of 2 ohms.

Tim Schwartz wrote in message
...
On 6/23/2010 3:48 AM, N_Cook wrote:
Just curious about these - how were they used? All that is known is they
came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
from
surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
diameter. Some sort of multiple series and parallel for 2 ohm etc or
with L
and C for speaker simulation ?



Nigel,

To me 2.8 ohms is an odd value. I have DALE 8 ohm 250 watt, non
inductive winding resistors. With four of them, I have 8 ohms at 250
watts, or 4 ohms at 500 watts. If I had felt the need I could have done
some more complicated switching and also had 16 ohms at 500 watts.

They are very useful as you can hook them up as a dummy load and view
on your scope, and run rather large amp right up to clipping, all while
not having to listen to any of it. It also makes it easy to measure
power at clipping, as long as you also monitor your mains voltage. (At
clipping, you have to watch the voltage drop at your bench outlet, as
you might be feeding the amp a lower mains voltage than it is specified
for, which will reduce power output. I have a VARIAC to correct for
this.)

I have seen one manufactured unit that used 7.87 ohm resistors, as they
figured out the resistance of the wiring and switching. I put together
my own, and did not feel the need for that level of accuracy.

The loads that I have are resistive, so not as difficult to drive as a
speaker might be, but again, good enough for my needs.

You did not specify the make or model of the resistors, or how they
were wired up.

Regards,
Tim Schwartz
Bristol Electronics


Marked neatly on the curve 2R8 +/-5 % and then 87.31 perhaps 31/52 of 1987.
I picked up the last 3 at a hamfest on Sunday, I did not think to ask how
many he had originally.
I'd not googled the Arcol name stamped on the brackets as they did not look
original to the resistor section, thinking it was just a maker of steel
brackets.
Crinkle form type at top of this image
http://www.arcolresistors.com/images...tubular-family.
jpg
but still leaves mystery of 2R8

On Wed, 23 Jun 2010 13:23:04 +0000 (UTC), Meat Plow wrote:

On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook ??o??:

Just curious about these - how were they used? All that is known is they
came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
from surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
diameter. Some sort of multiple series and parallel for 2 ohm etc or
with L and C for speaker simulation ?

Most newer SS amps are rated to a minimum of 2 ohms.

And cheapie meter leads might account for the extra 0.8 Ohms?
--
Grant.
--
http://bugs.id.au/

On Thu, 24 Jun 2010 00:30:47 +1000, Grant �ʇoɹ�:

On Wed, 23 Jun 2010 13:23:04 +0000 (UTC), Meat Plow
wrote:

On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook ??o??:

Just curious about these - how were they used? All that is known is
they came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
from surface area scaling of 2.5 and 6W ones, these are 210 mm long
35mm diameter. Some sort of multiple series and parallel for 2 ohm etc
or with L and C for speaker simulation ?

Most newer SS amps are rated to a minimum of 2 ohms.

And cheapie meter leads might account for the extra 0.8 Ohms? --
Grant.

They'd have to be very cheap. Mr. Kook is a talented technician so I
think that we can rule out that factor.

I use a pair of finned 300 watt 8 ohm resistors mounted on a giant power
supply heat sink to raise their continuous rating. Got them from Yamaha
way back in the 80's when I did warranty work for their pro-audio line.
They aren't branded Yamaha. They sent them to our warranty station along
with some other equipment they required to authorize us. If I recall the
total startup cost was a couple thousand bucks but we also had a credit
line with their service/parts dept.

On Thu, 24 Jun 2010 00:30:47 +1000, Grant wrote:
On Wed, 23 Jun 2010 13:23:04 +0000 (UTC), Meat Plow wrote:

On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook ??o??:

Just curious about these - how were they used? All that is known is they
came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
from surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
diameter. Some sort of multiple series and parallel for 2 ohm etc or
with L and C for speaker simulation ?

Most newer SS amps are rated to a minimum of 2 ohms.

And cheapie meter leads might account for the extra 0.8 Ohms?

You'd need at least 90' of them (at 20 AWG)

or 8' of 30AWG, but I've never heard of such slim wire
being used for probes.

In article , AZ Nomad wrote:
On Thu, 24 Jun 2010 00:30:47 +1000, Grant wrote:
On Wed, 23 Jun 2010 13:23:04 +0000 (UTC), Meat Plow wrote:

On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook ??o??:

Just curious about these - how were they used? All that is known is they
came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
from surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
diameter. Some sort of multiple series and parallel for 2 ohm etc or
with L and C for speaker simulation ?

Most newer SS amps are rated to a minimum of 2 ohms.

CAR AMPS

And cheapie meter leads might account for the extra 0.8 Ohms?

You'd need at least 90' of them (at 20 AWG)

or 8' of 30AWG, but I've never heard of such slim wire
being used for probes.

I typically get .3 ohms on the Fluke.

I have a couple dummy loads. One with 8- 50 watt gold
chassis resistors attached to sink with fan.
I have four more separate sinks without fan.
I either choose 8 ohms or 4.

greg

N_Cook wrote:
Just curious about these - how were they used? All that is known is they
came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me, from
surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
diameter. Some sort of multiple series and parallel for 2 ohm etc or with L
and C for speaker simulation ?

the ones I used were just large (hundreds of watts) ceramic wirewound
resistor mounted in heatsinks. They had to have been 8 ohms or something
really close as to not blow up 1970s and 1980s equipment.

you could hear the music though them if you got close enough.

"GregS" wrote in message
...
In article , AZ
Nomad wrote:
On Thu, 24 Jun 2010 00:30:47 +1000, Grant wrote:
On Wed, 23 Jun 2010 13:23:04 +0000 (UTC), Meat Plow
wrote:

On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook ??o??:

Just curious about these - how were they used? All that is known is
they
came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
from surface area scaling of 2.5 and 6W ones, these are 210 mm long
35mm
diameter. Some sort of multiple series and parallel for 2 ohm etc or
with L and C for speaker simulation ?

Most newer SS amps are rated to a minimum of 2 ohms.

CAR AMPS

And cheapie meter leads might account for the extra 0.8 Ohms?

You'd need at least 90' of them (at 20 AWG)

or 8' of 30AWG, but I've never heard of such slim wire
being used for probes.

I typically get .3 ohms on the Fluke.

I have a couple dummy loads. One with 8- 50 watt gold
chassis resistors attached to sink with fan.
I have four more separate sinks without fan.
I either choose 8 ohms or 4.

greg



My highest power dummy load is a (hacked) 3KW fan heater.



Gareth.

On Wed, 23 Jun 2010 11:10:17 -0500, AZ Nomad wrote:

On Thu, 24 Jun 2010 00:30:47 +1000, Grant wrote:
On Wed, 23 Jun 2010 13:23:04 +0000 (UTC), Meat Plow wrote:

On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook ??o??:

Just curious about these - how were they used? All that is known is they
came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
from surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
diameter. Some sort of multiple series and parallel for 2 ohm etc or
with L and C for speaker simulation ?

Most newer SS amps are rated to a minimum of 2 ohms.

And cheapie meter leads might account for the extra 0.8 Ohms?

You'd need at least 90' of them (at 20 AWG)

or 8' of 30AWG, but I've never heard of such slim wire
being used for probes.

I got a cheapie with that much resistance, is why the number rang a
bell. A cheapie no name meter that measures .8 or .9 ohm for short
circuit with its skinny leads

But, the OP mentioned upthread the 2.8ohm value was marked on the
resistor, the size of his resistors are similar to some 5ohm 300W
resistors I have here (Ohmite C300K5R0E).

Grant.
--
http://bugs.id.au/