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Dummy load for adjusting a Yamaha A-1 integrated

H

Hifibythekg

Super Member
Please could anyone direct me to the simplest and most economical way of using a dummy load to set the adjustments of bias and offset on an integrated amplifier?
The service manual just say connect a "dummy load resistance (70W) to the speaker terminals."
Searched but just can't find any visuals of how it can look at its simplest.
Many thanks.
 
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Typically, speakers are 8ohm connected between red and black terminals, a dummy load is to "simulate" the speaker, ie, be 8 ohms and have sufficient power handling for the amp. However since bias is checked with volume at minimum the need for 70W rating is overkill, you can get by with 10-20W. EDIT:mouser and others stock such resistors.
 
thanks MBZ, so is it just those gold coloured components with fins? And do I need two of them, one for each pair of speaker terminals?
And just wire them up? Simple as that..
 
The Yamaha SM just say 70W.
But it should be 70W and 8 ohms?
And, like you say, one can get away with 10-20W, again at 8 ohms?
 
Hifibythekg said:
Something like these but with the correct spec..

https://www.mouser.co.uk/ProductDetail/ARCOL-Ohmite/HS15-8R-F?qs=bvCpHSZmQjm6R2O%2BtPlEcw==&mgh=1&vip=1&gclid=EAIaIQobChMIjf_OtNqx8wIVh7TtCh3Viw1eEAQYBSABEgLUt_D_BwE
Click to expand...
Yeah, something like that. Carefully solder wires to each end then connect wires to spkr posts. Depends if this is a one off use or your likely to do further tinkering/repairs in which case you might go up market or larger. 70-100W items can be found/not that expensive then mount onto a heat sink from any old amp etc... You might want to use the dummy load/heat sink for some sort of load test rather than testing on your spkrs .
 
I have no knowledge of the A-1, but I know on some cap coupled units like my 2000A you actually use the dummy load to drive the amp into clipping (so you can adjust it to clip symmetrically) so yeah you do need either high wattage, more cooling, or both.
 
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N8Nagel said:
I have no knowledge of the A-1, but I know on some cap coupled units like my 2000A you actually use the dummy load to drive the amp into clipping (so you can adjust it to clip symmetrically) so yeah you do need either high wattage, more cooling, or both.
Click to expand...
Thanks, appreciated.
 
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