Thanks Henrik
The floating ground and the chassis ground of the analyser
can be separated. Here's a manual of the analyser: http://www.slack.com/pdf/HP334A.pdf
Pictures here: http://www.diyaudio.com/forums/showthread.php?postid=249597#post249597
When I connect the AlephX that way, +Out to +In of analyser and -Out to floating ground of analyser things become different.
You can imagine what happens when the chassis of the analyser is connected to -Out of the AlephX.
However, it seems not possible to do proper measurements then.
The analyser behaves in a very strange way, no way to calibrate it or to measure something decent.
Hugo - will find out in the end...with a little help from his friends
The floating ground and the chassis ground of the analyser
can be separated. Here's a manual of the analyser: http://www.slack.com/pdf/HP334A.pdf
Pictures here: http://www.diyaudio.com/forums/showthread.php?postid=249597#post249597
When I connect the AlephX that way, +Out to +In of analyser and -Out to floating ground of analyser things become different.
You can imagine what happens when the chassis of the analyser is connected to -Out of the AlephX.
However, it seems not possible to do proper measurements then.
The analyser behaves in a very strange way, no way to calibrate it or to measure something decent.
Hugo - will find out in the end...with a little help from his friends
Did you try this ...
Hugo,
When I mentioned floating ground I meant
disconnecting the earth lead from the analyser but this has its own safety implications !!!
The manual would seem to indicate that a differential measurement is possible by unstrapping signal / chassis GND - a much safer technique.
Is this the way you tried to do the differential measurment (with signal / chassis GND unstrapped) ?
X-Amp + out -> Signal in
X-Amp - out -> Signal in gnd
X-Amp GND -> Chassis GND
(I would add some series resistors - just in case !)
Dave
Hugo,
When I mentioned floating ground I meant
disconnecting the earth lead from the analyser but this has its own safety implications !!!The manual would seem to indicate that a differential measurement is possible by unstrapping signal / chassis GND - a much safer technique.
Is this the way you tried to do the differential measurment (with signal / chassis GND unstrapped) ?
X-Amp + out -> Signal in
X-Amp - out -> Signal in gnd
X-Amp GND -> Chassis GND
(I would add some series resistors - just in case !)
Dave
Re: Did you try this ...
Thanks for the safety warnings; indeed that's the way.
Unfortunately the analyser can't be calibrated in a proper way then. When you read the manual, Page 3-2, section 3-19, step 'm' and 'n' the coarse and fine balance are fully clockwise and the feeling exists that the meter in not enough nulled out.
When switching to automatic, the meter then indicates 5% distortion at 1Khz. Not correct IMO. Connecting X-AMP GND to Chassis GND makes no difference.
/Hugo
DRC said:
Thanks for the safety warnings; indeed that's the way.
Unfortunately the analyser can't be calibrated in a proper way then. When you read the manual, Page 3-2, section 3-19, step 'm' and 'n' the coarse and fine balance are fully clockwise and the feeling exists that the meter in not enough nulled out.
When switching to automatic, the meter then indicates 5% distortion at 1Khz. Not correct IMO. Connecting X-AMP GND to Chassis GND makes no difference.
/Hugo
Much to do about nothing?
I connected a LOAD to the amp’s output.
No things become completely different.
100Hz: 0.25%
1Khz: 0.39%
10Khz: 0.35%
20Khz: 0.4%
50Khz: 4.8%
This is much more realistic and I think I can live with that.
So please tell me that the load is required when measuring distortion.
/Hugo – not at all unhappy with AlephX anymore.
I connected a LOAD to the amp’s output.
No things become completely different.
100Hz: 0.25%
1Khz: 0.39%
10Khz: 0.35%
20Khz: 0.4%
50Khz: 4.8%
This is much more realistic and I think I can live with that.
So please tell me that the load is required when measuring distortion.
/Hugo – not at all unhappy with AlephX anymore.
That looks better
Hugo,
Oh yes - you will need a dummy load.
Did you compare these results to those obtained making a single ended measurement (with a dummy load this time
) ? It would be interesting to see how much error cancellation is occuring (and can be measured).
BTW what power level did you take measurements (and at what load impedance) ? Have you tried altering power levels ?
Sorry for all the questions but I need to make some similar measurements myself (unfortunately I WILL have to make a diff amp
) so this is most interesting to me.
Dave
Hugo,
Oh yes - you will need a dummy load.
Did you compare these results to those obtained making a single ended measurement (with a dummy load this time
) ? It would be interesting to see how much error cancellation is occuring (and can be measured). BTW what power level did you take measurements (and at what load impedance) ? Have you tried altering power levels ?
Sorry for all the questions but I need to make some similar measurements myself (unfortunately I WILL have to make a diff amp
) so this is most interesting to me.Dave
"No things" should have been "Now things" in my previous post.
Too excited to bring the news I guess.
A lot of good questions and help so far. Thanks a lot for that.
The load was just a normal speaker in the workplace.
Nothing dummy, so I only connected at low output.
You beat me to it so I'll post results with the SE measurements
and at different power levels.
/Hugo
Too excited to bring the news I guess.
A lot of good questions and help so far. Thanks a lot for that.
The load was just a normal speaker in the workplace.
Nothing dummy, so I only connected at low output.
You beat me to it so I'll post results with the SE measurements
and at different power levels.
/Hugo
Just like a few other people who send their picture to Desmond,
my AlephX's are now too in the 'Gallery of Fame'.
It's a great pleasure to see them there.
Thanks to the whole Passdiy team
/Hugo
my AlephX's are now too in the 'Gallery of Fame'.
It's a great pleasure to see them there.
Thanks to the whole Passdiy team
/Hugo
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
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
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
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
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
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
Attachments
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
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,Netlist said: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
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?
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
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
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
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
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.
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.
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
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
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