Standby

[NHul]

Hi


If I'm not wrong, Mr Pass "X" series amplifiers are all with standby approach. I'm not familiar with that kind of device. I tried to search for standby on the forum, but I could not find any threads relative to this.
Iwould like to know if anyone has same existing standby circuit.
Would it be possible to built someone, and put it in the Aleph series?

Thanks for any input,


NHul

 

[leroy]

I think the X-series use the same topology as Mark Levinson amplifiers. That means when you switch from 'on' to 'standby' the power stage is switched off while the pre-amplifier stage remains biased.

 

[Nelson Pass]

Please do not refer to the topology of X amps as
having any similarity to the Harmon products. I
have schematics of those, and no two types of
amplifiers could be more dissimilar.

The standby in the X amps leaves the supply charged,
but shuts down the bias and front end.

 

[leroy]

Is the reason of leaving the supply charged to prevent the capacitors getting deformed?

 

[Nelson Pass]

No, simply to avoid the monster inrush.

 

[BrianGT]

For standby mode, could you simply put a dual pole switch on the + and - voltage lines coming out of your capacitors?

Would that cause problems? Would a 20A switch be enough for this?

--
Brian

 

[NHul]

For shuts down this stage, where exactly in way of bias and frontend put the relays ?

NHul

 

[leroy]

Place a relay between the supply capacitors and the rest of the amplifier. Just make sure the supply for the relay coil is taken from the capacitors of before, otherwise you can switch your amp standby but can never turn it on anymore

 

[Pboden]

Stanby on Aleph

For standby mode, could you simply put a dual pole switch on the + and - voltage lines coming out of your capacitors?

Would that cause problems? Would a 20A switch be enough for this?

--
Brian

I can't find an answer to Brians question regarding stanby mode on the Aleph. There shouldn't be a problem to place a switch between the capacitors and the main board?
That would stop the massive inrush to the transistors?

As a result, there would be no need for a soft start module, i.m.o.

 

[Blues]

Re: Stanby on Aleph

I can't find an answer to Brians question regarding stanby mode on the Aleph. There shouldn't be a problem to place a switch between the capacitors and the main board?
That would stop the massive inrush to the transistors?

As a result, there would be no need for a soft start module, i.m.o.

Works like a charm on my Zv4 with 90mF/ch of caps. Requires a main power switch and On-On Standby/Play switch. The latter keeps the caps charged with a standby LED lit orange and in play mode turns blue and plays music. I also don't have to keep replacing 3A fuses every power-on. Initial power on (make sure PSU is ok) requires a bigger fuse. Let it soak for a few minutes then power off and change-out to specified fuse value

 

[Blues]

sweet music in blue!

 

[Pboden]

sweet music in blue!

Thanks for your reply.
Nice amp you got there. I bet your topplate gets kind of dry.

 

[LBHajdu]

An even simpler way would be to short out the bias transistor by placing a switch across it. The Alephs don’t have such a section so on these amps something more complex would be needed.

I can’t help wondering that this stand-by mode shortens the life of the caps. They still have to flatten the ac coming in and there is still a voltage across them.

Alternatively you could switch the rail to the output section off with mosfets and you could hook this into a dc detection unit, in order to shut off power to the output stage in the even that dc is detected on the outputs. So it would serve two functions.

I don’t know how popular the standby function is, the amp still has to heat up again before sounding its best, thermal equilibrium must be reached.

 

[Blues]

Thanks for your reply.
Nice amp you got there. I bet your topplate gets kind of dry.

Pboden, I laminated the top plate with polyvarnish before it got too dry. Thanks...

I don’t know how popular the standby function is, the amp still has to heat up again before sounding its best, thermal equilibrium must be reached.

Like NP said, this is to prevent the monster inrush of current everytime the caps charge from empty...even with 5A thermistors my lights still dim and that's just 180mF of capacitance.