Required equipment for Leach build?

[WithTarragon]

I am contemplating building a Leach amplifier (possibly using the chassis, heat sink and transformer from a Hafler DH200).

I have a two channel scope (Tektronix) and a decent DMM.

I do not have a Variac not do I have a bench power supply.

Are both these items critical? Can I substitute a light bulb in series to slowly bring up the amp?
Thanks,
-Tom

 

[BobEllis]

Although a Variac makes it nicer, the light bulb trickworks well. Also use some 1/4W 100R resistors in place of the rail fuses the first time, as Professor Leach suggests. That's all I had, and they saved me when I had swapped the output devices to the wrong rail...

 

[Leolabs]

If the bench power supply able to provide enough voltage/current,then it's a better choice than variac.

 

[WithTarragon]

Thanks for answering.
What does a bench supply typically cost for what I need (eBay).

It looks like the cost is a function of the number of channels, the number of volts and the number of amps. What is a reasonable choice?

Or, How realistic is it to substitute with a variac or the light bulb trick?

Thanks again,
-Tom

 

[jaycee]

The lightbulb in series with the live wire will do, as well as some resistors in place of fuses for the first time.

The main tool thats useful you have - a scope! Building the amp into an old Hafler chassis takes care of the heatsinking too. If you use Professor Leach's boards you should have no trouble 🙂

 

[WithTarragon]

Jaycee,
Thanks!
The light bulb "instrumentation" will save some trouble. I was not sure if the preliminary adjustments on the amp could be made in under this configuration.

The Hafler amps are plentiful - they must have sold a million and they are already drilled for the TO3's.

-Tom