Can I use-35-0-35 volt DC for Leach Amp?

Wynand · 8th August 2005, 03:10 PM

The subject line saiz it all...if not, what is the minimum voltage rails required? ANY info will be appreciated.

loek · 8th August 2005, 03:25 PM

My old Leach(1980) runs fine on 2x 40v DC...
Loek

AndrewT · 8th August 2005, 06:26 PM

Hi,
your peak output voltage will be about 28V.
this limits your power to about 50W into 8r, about 90W into 4r and about 130W into 2r. I have assumed a 300VA transformer driving both channels at the same time.
All these speakers can be of the severe rating (60degree phase angle) since the low voltage rails do not stress the output transistors.
Since it performs so well into 2r you could consider bridging if you need more power;- 180W into 8r at 60degree phase angle. The 300VA and two PCBs now form a single channel amp. It would be cheaper to buy a higher voltage transformer for more power.

BobEllis · 8th August 2005, 06:57 PM

Leach version 4.5 needs in excess of 40 volts to perform at its best - that is the reference voltage for the input stage cascode. Earlier versions did not use these zeners, and may perform well on lower rails. IIRC, Dr. Leach recommends >45V minimum.

djk · 9th August 2005, 07:56 AM

Easy to change the zener, or run a high voltage tier for the front end.

skaara · 9th August 2005, 10:31 AM

Just change the zeners and it should work fine, i did that once for +-36V supply voltage and it worked well.

jacco vermeulen · 9th August 2005, 01:55 PM

Quote:

Originally posted by AndrewT
you could consider bridging if you need more power

Now, what would be the slewrate of a bridged Leach amplifier ?

djk · 10th August 2005, 07:10 AM

Slew rate is not important.

Since good audio performance is 2V/µS per peak volt of output, what we are specifing is rise time.

The rise time is substantially unchanged in bridge mode, as the slew rate doubles to go along with the doubling of the voltage swing.

jacco vermeulen · 10th August 2005, 10:41 AM

And if voltage of the output rails is halved, then bridged ?
Same output, double slewrate, halve the risetime ?

djk · 11th August 2005, 07:24 AM

The rise time shouldn't really change, and that's all that matters.

8th August 2005, 03:10 PM	#1
Wynand diyAudio Member Join Date: Mar 2005 Location: Cape Town	Can I use-35-0-35 volt DC for Leach Amp? The subject line saiz it all...if not, what is the minimum voltage rails required? ANY info will be appreciated.

8th August 2005, 03:25 PM	#2
loek diyAudio Member Join Date: Feb 2005 Location: The Hague	leach psu My old Leach(1980) runs fine on 2x 40v DC... Loek

8th August 2005, 06:26 PM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, your peak output voltage will be about 28V. this limits your power to about 50W into 8r, about 90W into 4r and about 130W into 2r. I have assumed a 300VA transformer driving both channels at the same time. All these speakers can be of the severe rating (60degree phase angle) since the low voltage rails do not stress the output transistors. Since it performs so well into 2r you could consider bridging if you need more power;- 180W into 8r at 60degree phase angle. The 300VA and two PCBs now form a single channel amp. It would be cheaper to buy a higher voltage transformer for more power. __________________ regards Andrew T.

10th August 2005, 10:41 AM	#9
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, just under Rotterdam	And if voltage of the output rails is halved, then bridged ? Same output, double slewrate, halve the risetime ? __________________ Looks like Sponge Bob has killed another thread.

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8th August 2005, 06:57 PM	#4
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	Leach version 4.5 needs in excess of 40 volts to perform at its best - that is the reference voltage for the input stage cascode. Earlier versions did not use these zeners, and may perform well on lower rails. IIRC, Dr. Leach recommends >45V minimum.

9th August 2005, 07:56 AM	#5
djk diyAudio Member Join Date: Feb 2001 Location: USA	Easy to change the zener, or run a high voltage tier for the front end.

9th August 2005, 10:31 AM	#6
skaara diyAudio Member Join Date: Jun 2002 Location: Europe, Slovenia	Just change the zeners and it should work fine, i did that once for +-36V supply voltage and it worked well.

10th August 2005, 07:10 AM	#8
djk diyAudio Member Join Date: Feb 2001 Location: USA	Slew rate is not important. Since good audio performance is 2V/µS per peak volt of output, what we are specifing is rise time. The rise time is substantially unchanged in bridge mode, as the slew rate doubles to go along with the doubling of the voltage swing.

11th August 2005, 07:24 AM	#10
djk diyAudio Member Join Date: Feb 2001 Location: USA	The rise time shouldn't really change, and that's all that matters.

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