[Felipe]

Hi guys,

I finally found the time to work on my LF55. After all the case work and wood cutting prior to the wedding, i left the electrical stuff for after the holiday season. So i am back and struggling to find the time to jiggle with my new amp.

Last night i wired the PS and "retouched" the modules with Hugh's tricks. Only thing left is connect modules to PS. QUESTION :

I have +/- 37.3V across the rails instead of the regular 36V. Will this be overkill or will it cause any problems? I do not intend to max the volume, i will probably never exceed the 20%...
My mains are typically 234V...a little over the nominal V.


Can't wait to turn it on and hear it with my brand new modded SB.....aaarrgg the silent pain of anxiety !!!

[aurelius]

Felipe,

Go for it!  I think that you will find that your supply voltage will drop under load conditions...

There is no such thing as a perfect voltage supply (0 output resistance, voltage invariable under load); all real-world power supplies include series resistance (for example, from the 10s of metres of wire used in the transformer, etc).

Remebering that Power (RMS) = (Vp X Ip)/2, we can rearrange to get Ip= 2 x Power/Vp = 2 x 55 / 36 =  3.06Amps (peak) or 2.16A (RMS)

If the power supply resistance is 0.2 ohm, and the average current through the power supply is 2.16A, then the voltage on the rails will drop 0.2 x 2.16 = 0.432V.  Your experience may be more, it may be less, but either way, it will be close enough to 36 volts to not worry the LF output stage.

Please let us know what you think when you are done!

[AKSA]

Felipe,

Aurelius (thanks Mark!) is right - go for it.  A voltage on the rail from 24 to 42 has no effect on the operation of the LF55 except to alter the quiescent (bias) current of the output stage, which can generally be adjusted to the specified 60mV with the trimpot.

This amp uses current source feed to the front end, unlike the AKSA, making it highly flexible for under and overvoltage rails.

Cheers,

Hugh