Required equipment for Leach build?

WithTarragon · 4th February 2008, 08:33 PM

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 · 5th February 2008, 12:55 PM

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 · 5th February 2008, 01:38 PM

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

WithTarragon · 5th February 2008, 02:18 PM

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 · 5th February 2008, 11:33 PM

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 · 6th February 2008, 12:03 AM

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

4th February 2008, 08:33 PM	#1
WithTarragon diyAudio Member Join Date: Jun 2007	Required equipment for Leach build? 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

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5th February 2008, 12:55 PM	#2
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	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...

5th February 2008, 01:38 PM	#3
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	If the bench power supply able to provide enough voltage/current,then it's a better choice than variac.

5th February 2008, 02:18 PM	#4
WithTarragon diyAudio Member Join Date: Jun 2007	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

5th February 2008, 11:33 PM	#5
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	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

6th February 2008, 12:03 AM	#6
WithTarragon diyAudio Member Join Date: Jun 2007	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

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