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Old 1st October 2021, 12:44 PM
Riggers Riggers is offline
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Join Date: Aug 2012
Location: Brisbane, Queensland. Aus
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Default Dummy load for testing Pre 3 on 'scope.

Hi all

After a long overdue chance to review my 8 year old WD PRE3 build and tidy up some lead dress and the like I wanted to test its performance on my oscilloscope. Being as it is a transformer output stage am I correct in saying it should run through a load before being attached to the input of the oscilloscope? And would we be talking in the order of 50K or 100K ohms? Would half watt resistors do?

Cheers in advance.

Phil.
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Old 1st October 2021, 04:46 PM
Richard Richard is offline
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Join Date: Dec 2005
Location: Notts
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Default Re: Dummy load for testing Pre 3 on 'scope.

Hi Phil, yes as you say, ideally test it with the OP loaded by a similar load to your power amp input; typically 20K for solid state and 47K to 1M for a valve power amp and see if the loading makes much difference. Half watt resistors will be fine as it is 5V max out and power dissipated will be (V squared) divided by R, so a fraction of a watt. If you have the WD CD there are some tests results by Noel on there in the 3 Series review or send me a PM with your address and I'll email it as I'm sure Matthew would be happy for you to have it.
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