Quad ESL 57 Dummy load - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Radio Wrangler · 29th May 2020, 12:14 am

Quote:

Originally Posted by rontech

I seem to recall that QUAD used to state that their amplifiers were unconditionally stable into any load.

They had to be! the range of impedance their electrostatic speaker wandered over across the audible range is really quite an obstacle course.

But ANY load? I wouldn't put anything expensive ner an intermittent load with a bad connection or sparking. It fits under the 'Any' banner, but would cause fatalities in many amplifiers.

David

Diabolical Artificer · 29th May 2020, 5:32 am

I use 8 of those Arcol resistors - 2r - on an old welder tunnel HS with a fan on for loads of 200w or so, mine is in stereo DL and has, two 4mm banana jacks as OP, with 3 more so I can use a jumper bar to select speaker/DL, + also 3 BNC's per channel + 10:1 attenuator.

All you need for a simple is a suitable beefy HS, two banana jacks for OP, a drill and 8 self tappers to make a mono dummy load. I then made up two suitable beefy leads for testing.

The OP power for a Quad 2 is given as 20w if certain changes are made, so that's 12.5v RMS approx.

Andy.

Herald1360 · 29th May 2020, 11:33 am

12.5V rms into 8R. Into 15R it'll be around 17.5V rms.

Bufo Bill · 29th May 2020, 1:39 pm

Thanks for the info guys.

Andy, that sounds like a great device, very ingenious of you.

Cheers from Bill.

audiomm · 29th May 2020, 10:52 pm

For what it's worth, I have a dummy load set up which is built into my workbench. Uses 4 x 8 Ohm resistors each rated at 300watts so probably a bit overkill for most domestic amplifiers I get to fix

The resistors are wire into a switching set up which allows me to select 8 or 16 ohms (I was also going to incorporate 4 ohms as well but haven't got 'a round tuit' yet), plus switching from load to spkrs and also a set of BNC's so I can also monitor on 'scope regardless. I made this about 25 years ago and it has been through 3 house shifts and 3 purpose built benches.When not in use I repurposed the cut out from benchtop as a cover. Methinks it might need tarting up a bit now as it has been well raced & rallied over that time.
Pix are below.
Mike

Bufo Bill · 29th May 2020, 10:55 pm

Great set up Mike, congrats! I really like seeing the things you guys come up with!
Cheers from Bill.

Radio Wrangler · 29th May 2020, 11:34 pm

Some classic stuff there. 180 scope family (tunnel diodes and all) 8601A sweeper, and that little LCR bridge with the phase detector to tell you which way to crank the handle to find the null. TMS500 as well.

Nice!

David

Bufo Bill · 29th May 2020, 11:41 pm

I've got a 180A on my list of repair projects. Will definitely need some help with that one!
Cheers from Bill.

audiomm · 30th May 2020, 12:45 am

Quote:

Originally Posted by Radio Wrangler

Some classic stuff there. 180 scope family (tunnel diodes and all) 8601A sweeper, and that little LCR bridge with the phase detector to tell you which way to crank the handle to find the null. TMS500 as well.

Nice!

David

Thanks David. Yup - I like that era HP & Tek stuff - very reliable, well built and easy to use. Being a typical Yorkshireman (short arms & deep pockets) I didn't pay much(if anything) for any of that gear

-I somehow seemed to be on the receiving end of 'donor's from friends who were upgrading. The dummy load gizmo came together from bits & bobs out of what was lying around. Thinking about it now I would say the materials for the benches I have built would easily cover the cost of what sits on them.
Mike

rontech · 30th May 2020, 11:01 am

Quote:

Originally Posted by Radio Wrangler

Quote:

Originally Posted by rontech

I seem to recall that QUAD used to state that their amplifiers were unconditionally stable into any load.

They had to be! the range of impedance their electrostatic speaker wandered over across the audible range is really quite an obstacle course.

But ANY load? I wouldn't put anything expensive ner an intermittent load with a bad connection or sparking. It fits under the 'Any' banner, but would cause fatalities in many amplifiers.

David

I quite agree!

29th May 2020, 5:32 am	#22
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,657	Re: Quad ESL 57 Dummy load I use 8 of those Arcol resistors - 2r - on an old welder tunnel HS with a fan on for loads of 200w or so, mine is in stereo DL and has, two 4mm banana jacks as OP, with 3 more so I can use a jumper bar to select speaker/DL, + also 3 BNC's per channel + 10:1 attenuator. All you need for a simple is a suitable beefy HS, two banana jacks for OP, a drill and 8 self tappers to make a mono dummy load. I then made up two suitable beefy leads for testing. The OP power for a Quad 2 is given as 20w if certain changes are made, so that's 12.5v RMS approx. Andy. __________________ Curiosity hasn't killed this cat...so far.

29th May 2020, 11:33 am	#23
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Quad ESL 57 Dummy load 12.5V rms into 8R. Into 15R it'll be around 17.5V rms. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

29th May 2020, 1:39 pm	#24
Bufo Bill Heptode Join Date: Jan 2016 Location: Wolverhampton, West Midlands, UK. Posts: 777	Re: Quad ESL 57 Dummy load Thanks for the info guys. Andy, that sounds like a great device, very ingenious of you. Cheers from Bill.

29th May 2020, 10:52 pm	#25
audiomm Pentode Join Date: Sep 2007 Location: Ranfurly, New Zealand Posts: 170	Re: Quad ESL 57 Dummy load For what it's worth, I have a dummy load set up which is built into my workbench. Uses 4 x 8 Ohm resistors each rated at 300watts so probably a bit overkill for most domestic amplifiers I get to fix The resistors are wire into a switching set up which allows me to select 8 or 16 ohms (I was also going to incorporate 4 ohms as well but haven't got 'a round tuit' yet), plus switching from load to spkrs and also a set of BNC's so I can also monitor on 'scope regardless. I made this about 25 years ago and it has been through 3 house shifts and 3 purpose built benches.When not in use I repurposed the cut out from benchtop as a cover. Methinks it might need tarting up a bit now as it has been well raced & rallied over that time. Pix are below. Mike Attached Thumbnails

29th May 2020, 10:55 pm	#26
Bufo Bill Heptode Join Date: Jan 2016 Location: Wolverhampton, West Midlands, UK. Posts: 777	Re: Quad ESL 57 Dummy load Great set up Mike, congrats! I really like seeing the things you guys come up with! Cheers from Bill.

29th May 2020, 11:34 pm	#27
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,857	Re: Quad ESL 57 Dummy load Some classic stuff there. 180 scope family (tunnel diodes and all) 8601A sweeper, and that little LCR bridge with the phase detector to tell you which way to crank the handle to find the null. TMS500 as well. Nice! David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

29th May 2020, 11:41 pm	#28
Bufo Bill Heptode Join Date: Jan 2016 Location: Wolverhampton, West Midlands, UK. Posts: 777	Re: Quad ESL 57 Dummy load I've got a 180A on my list of repair projects. Will definitely need some help with that one! Cheers from Bill.