Stereomour input AC voltage

[8452]

Can the Stereomour handle input AC voltages from 123 to 129 VAC? I had to variac my Paramounts else the power transformers got hot enough to burn you. Same issue for Stereomours?

[Paul Birkeland]

The Paramounts will take 123-129V.  The power transformers are rated to run at temperatures much hotter than your hand will tolerate, that's not a particularly strong indicator.

The Stereomour power transformer will generally run cooler than the Paramount transformers.

-PB

[8452]

Thanks for your response.

The question I was trying asking, and not very well, was will those voltages put undo stress on the Stereomour's parts, regardless of the transformer temps?

[Paul Birkeland]

Neither amp is going to mind the excess line voltage.

[Paul Joppa]

It's my current intent to design for acceptable operation with 120+/-10%, which accords more or less with traditional tube design for consumer electronics from the old days. I don't always get there, but I get close at least.

The best tubes usually call for +/-5% on filament/heater voltage, which means the same applies to line voltage unless the filament/heater is regulated. EML specifies 4%. So it's an unresolved issue, really. In the higher end designs we've incorporated more and more regulation (it sounds better as well as stabilizing the tube conditions), but that is not appropriate for the entry level where cost is really important.

I've been thinking maybe we should put together a voltage-adjusting kit, some day.

[Grainger49]

Maybe some power resistors on the primary of the transformer to adjust all the secondary voltages at once?  That would be an easier voltage rating to find than resistors on the secondary for each winding.

[8452]

Thanks for your replies. I will probably use my Variac to be safe. My Paramounts ran best around 118 VAC, so I will experiment.