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

[Wynand]

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

 

[loek]

leach psu

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

 

[AndrewT]

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]

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]

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

 

[skaara]

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

 

[jacco vermeulen]

you could consider bridging if you need more power

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

 

[djk]

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]

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

 

[djk]

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