using 2 ohm loads on leach amp

Wagener · 29th March 2004, 08:58 AM

Is the leach amp capable of doing this?

For instance running four 8 ohm speakers on one channel?

If I have a 4 channel amp and I want to run 2 ohm loads (2 parllaled 4ohm speakers) what VA transformer will I require?

Please comment on this

Christer · 29th March 2004, 01:31 PM

If you just want to run four speakers, why don't you make
a series-parallell connection, ie. two in series parallelled with
two in series, which will give you 8 Ohms. For the case of
two 4 Ohm speakers you may use them in series and get 8 Ohms.

BobEllis · 29th March 2004, 02:50 PM

The protection circuit will limit the current/power you can deliver to two ohm loads. Doubling the output stage and running rails on the low side ought to work to cure this, assuming that the driver stage can deliver enough current to run them. I've heard of people running 3 pairs of output devices. Not sure if there are any other issues with 2 ohm stability, though.

Eva · 31st March 2004, 07:08 AM

Looking at the circuit, I think it would happily drive 2 ohms and less with no problem provided that output devices [and its related base and emitter resistors] and heatsinks are doubled

No more modifications seem to be necesary since the drivers [MJE15030/1] have enough current capability and the current limiting circuit senses the current through a single output transistor instead of the full output current [ie: the limiting thershold is proportional to the number of output devices used]

[Halving and/or reducing even further the value of the resistor placed between the emitters of the drivers may help if oscillation problems arise. This will speed up output device turn-off at the expense of higher driver heatsinking requirements]

Power supply may also be taken into account but the difference will be only more or less sagging

djk · 1st April 2004, 07:02 AM

"Is the leach amp capable of doing this?

For instance running four 8 ohm speakers on one channel?

If I have a 4 channel amp and I want to run 2 ohm loads (2 parllaled 4ohm speakers) what VA transformer will I require?"

I built a Leach output stage to run a 1 ohm load with ±80V rails.

It had ten pairs of MJ15024/25 outputs per channel, another pair as drivers, and a pair of 2N3585/2N6421 for predrivers.

The transformer should be rated at 2VA for every 1W out at the lowest expected impedance.

29th March 2004, 08:58 AM	#1
Wagener diyAudio Member Join Date: Mar 2004 Location: Paarl	using 2 ohm loads on leach amp Is the leach amp capable of doing this? For instance running four 8 ohm speakers on one channel? If I have a 4 channel amp and I want to run 2 ohm loads (2 parllaled 4ohm speakers) what VA transformer will I require? Please comment on this

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29th March 2004, 01:31 PM	#2
Christer diyAudio Member Join Date: Sep 2002 Location: Sweden	If you just want to run four speakers, why don't you make a series-parallell connection, ie. two in series parallelled with two in series, which will give you 8 Ohms. For the case of two 4 Ohm speakers you may use them in series and get 8 Ohms.

29th March 2004, 02:50 PM	#3
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	The protection circuit will limit the current/power you can deliver to two ohm loads. Doubling the output stage and running rails on the low side ought to work to cure this, assuming that the driver stage can deliver enough current to run them. I've heard of people running 3 pairs of output devices. Not sure if there are any other issues with 2 ohm stability, though.

31st March 2004, 07:08 AM	#4
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	Looking at the circuit, I think it would happily drive 2 ohms and less with no problem provided that output devices [and its related base and emitter resistors] and heatsinks are doubled No more modifications seem to be necesary since the drivers [MJE15030/1] have enough current capability and the current limiting circuit senses the current through a single output transistor instead of the full output current [ie: the limiting thershold is proportional to the number of output devices used] [Halving and/or reducing even further the value of the resistor placed between the emitters of the drivers may help if oscillation problems arise. This will speed up output device turn-off at the expense of higher driver heatsinking requirements] Power supply may also be taken into account but the difference will be only more or less sagging

1st April 2004, 07:02 AM	#5
djk diyAudio Member Join Date: Feb 2001 Location: USA	"Is the leach amp capable of doing this? For instance running four 8 ohm speakers on one channel? If I have a 4 channel amp and I want to run 2 ohm loads (2 parllaled 4ohm speakers) what VA transformer will I require?" I built a Leach output stage to run a 1 ohm load with ±80V rails. It had ten pairs of MJ15024/25 outputs per channel, another pair as drivers, and a pair of 2N3585/2N6421 for predrivers. The transformer should be rated at 2VA for every 1W out at the lowest expected impedance.