Industrial AlephX High Power version

[Netlist]

Originally posted by Edwin Dorre
very very nice!
I noticed you used a kind of silvered wire for your second version of the Aleph-X instead of normal 2.5mm^2 . Notice any difference in sound?
Edwin

Thanks
It is not silver wire, just plain ordinary stripped wire.
To me the amps play the same, and if there would be any difference it will be difficult to say if it's coming from the wires.

/Hugo

[Netlist]

Over the past few weeks I noticed strange behaviour from the toroids. You all know the buzz a toroid makes at start-up, drawing a lot of current for a few seconds.
This buzz comes up randomly now, when the amps are powered up. Maybe it has always been like that except I only start notice it a couple of weeks ago. Suddenly both transformers start to buzz, very equally for about 5 to 20 seconds, then the noise disappears and comes back few seconds or minutes later and so on. Doesn’t matter if they play or not. There's no vast timing for the effect, it can happen twice in a minute, or twice in 10 minutes, more or less. Both amps are hooked up on the same power line so I started measuring it. Voltage varies between 228-236V. Frequency is a stable 50Hz, +/- 0.01Hz. Positive and negative dutycycle point is 50.25 and 49.75. DC +/- 1mV. I also measured the current trough the amp but it sits there nice and stable at about 6A all the time.
The funny thing is that no difference can be measured in all these conditions when the Buzz comes up. I then connected one amp to another socket from another circuit. Same problem.

Any thoughts?

/Hugo

[macka]

Hugo,

I have had the same noises / effects using large toroidals.....

My understanding is the noise you hear is core attemtping to saturate, and this is due in part to the very high efficiency of toroidals where there are no losses.

This is not unusual for toroidals and for audio applications the design can be varied to minimise the effect by using larger the normal core size for the given VA rating, hence toroidals for audio are often more expensive.

Also, power factor problems on your immediate mains power grid can give rise to transformer noise

Ian

[Bensen]

Hugo,

I've the same problem with my two 500VA toroid's from Amplimo in my Crescendo amp (1982). First a thought the cause was that I mounted the tow toroid's on each other.

I've read a thread on this forum a while ago where there was the same problem, this person had changed the normal rectifiers to fast recovery ones or something. Than his buzz no longer appears. I never tryed that.

Ciao

Ben

[Netlist]

Thanks
I might have found the cause.
My neighbour has a big electric welding machine.
His workplace is located in a part of the factory were we live and taps from the same source.
I also noticed that when the transformers is buzzing, the dutycycle changes more from the ideal 50%. From 50.3 to 50.8 .
So if I would change the recifiers, could that solve (part) of the problem?

Nice amp you made there, Ben

/Hugo

[roddyama]

Originally posted by Netlist
Thanks
I might have found the cause.
My neighbour has a big electric welding machine.
His workplace is located in a part of the factory were we live and taps from the same source.
I also noticed that when the transformers is buzzing, the dutycycle changes more from the ideal 50%. From 50.3 to 50.8 .
So if I would change the recifiers, could that solve (part) of the problem?

Nice amp you made there, Ben

/Hugo

Hi Hugo,

I was going to post that we all share the power lines with our neighbors. What they do in their homes and shops will have an affect on our listening. Maybe you might want to try some of those high dollar line cords?? ... or maybe not?

[Netlist]

Rodd
I'm open minded enough to let the guy in who sells powercords that would pretend to eliminate my problem. After all, it will not take more then 2 minutes to test if it works

I just had a look inside my neighbours machine. The trafo is about the size of two of my AlephX's He doesn't want to convert it into an amp he says...

/Hugo

[wuffwaff]

Hi Hugo,

my Aleph 5 (2 x 600VA) has the same problem. It can be very quiet, then suddenly it humms very loud and almost vibrates out of my rack.
Changing my ac power to balanced took care of the problem for a few weeks but now it has returned again
It is sometimes started by very small things like connecting my P-3A DA converter wich must have a very nasty power supply.
I will try some things like snubbers on the rectifiers iun the next few weeks (I also read the thread) but I´m not shure this´ll help.
I would like to find a sollution before I start the power supply of my X (I´ve got the trafos already).

william

[Nelson Pass]

There are three typical causes for intermittent mechanical hum
from the transformer.

1) Your circuit might intermittently draw very large amounts of
current. This is not very likely.

2) Your AC line might have some DC type noise on it, which
saturates the transformer. Lamp dimmers and other Variac
type controlled equipment are the usual culprit, and a filter
network is the usual answer.

3) Your secondary system might be drawing, on average, more
current from one rail than the other, in other words, different
+ to ground than - to ground. If the secondary windings are
mismatched and you are using only 1 rectifier bridge for the
two polarities, this can cause the same kind of saturation as
in (2). This is common when there is high DC offset at the
output through the speaker. Besides balancing out the draw,
you can also cure it by providing one rectifier bridge for each
rail polarity, assuming that you have dual secondaries and
not just a center-tapped secondary.

[wuffwaff]

1) your right

2) not possible with a balanced ac power

3) this was the cause for quite a bit of mechanical humm from my Ono where the plus draws more current than the minus side but it doesn´t work for my Aleph with two bridges per channel and quite low (30mV) DC offset

Any explanation for the bad influence of connecting a 9V AC transformer to the same 230V power line????

william