Hi John, in hindsight I should have rejected it sooner. But like someone else mentioned on this thread: the dealer did a very good job of keeping me busy waiting for their sending me a Multimeter, then a Hobotester and finally a Mains Regenerator. Then I had to spend some time compiling readings from my mains at different times of the day and night. Suddenly one realises that a lot of time has elapsed. I really wanted to solve this issue so was reluctant to not give the dealer/pass labs time to sort it out. Thanks.
I think this thread is all about cult 'A' vs. cult 'B', and nothing to do with the product. Just saying...
Hi MEPER, earlier in this thread, I believe I mentioned disconnecting my speakers and all other items and it made no difference. The noise is coming from the amp. Volume is at zero.
Hi Mooly, Unfortunately the noise floor is from my rode lavalier microphone. I didn't want to do any processing in post [final cut]. I wanted to give you the raw sound.
I took a listen. That is not transformer ‘growl’ due to DC on the mains or core saturation - most likely the result of a non- stabilised core running a heavy load.
Stabilised toroidal cores are made by vacuum impregnating the laminations inside the plastic core covering. In non stabilised cores, this step is omitted for cost reasons. Non-stabilised cores are ok for industrial applications, but can be problematic for audio and especially so with heavy loads as in class A.
Hopefully you can resolve your issue with the dealer amicably.
NB it’s much easier to just use your mobile phone to record this kind of noise
Stabilised toroidal cores are made by vacuum impregnating the laminations inside the plastic core covering. In non stabilised cores, this step is omitted for cost reasons. Non-stabilised cores are ok for industrial applications, but can be problematic for audio and especially so with heavy loads as in class A.
Hopefully you can resolve your issue with the dealer amicably.
NB it’s much easier to just use your mobile phone to record this kind of noise
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The humming sound we hear on the recording is that what you hear in listening position 3-4 m away?
Because questions/problems regarding toroidal power supply transformers pop up repeatedly, here once more what I posted over three years ago:
"The difference between stock toroidal power supply transformers and so called "audiograde" toroidal power supply transformers is not specified.
What generally is meant with "audiograde" is that manufacturers use transformers with higher power rating than necessary for the job.
Toroids are very efficient transformers because of their electromagnetic geometry; form and absence of air gap mean comparatively low power loss.
This means that, for a given power, toroids are smaller than their EI or whatever counterparts.
Another "technical" advantage is that toroids have rather low strayfields.
Dimension and weight are important economic reasons to use toroids.
The problem however with many toroids is core excitation, expressed in flux density T.
Everyone using toroids is familiar with the inrush "oomph", requiring NTC resistors or other means not to blow fuses, and sometimes "DC blockers" to prevent core saturation.
This high inrush current comes from the fact that, because of the efficient electromagnetics, the toroid responds instantaneously when line voltage is switched on.
EI, and other transformers with some sort of airgap and/or less efficient geometry respond less brutal; they therefore have less inrush current.
Winding toroids with less inrush current is not so difficult but normally not done.
To do so, flux density must remain low, preferably maximum 1 T, instead of the "standard" 1,7-1,8 T for off the shelve toroids.
For lower flux density it is necessary to wind more turns on a given core.
More turns mean more required winding space, hence a larger core is required for a low T toroid with the same power as a "stock" high T toroid.
So here "better" is larger, heavier, more expensive.
When you need a high quality toroid with even lower strayfields, find one with low T, and preferably a screen between primary and secondaries (ask the manufacturer for the specs).
A very good, but less acknowledged alternative in the "audiophile" arena is a power supply transformer wound on a c-core (in between toroid and EI for efficiency).
With a c-core it is easy to apply minor air gapping to prevent hectic inrush current, so we don't need NTC resistors or other "inrush current fighters" and DC blockers.
Besides, unlike toroids, c-core transformers (like EI transformers) can be wound tightly, with no "crossing" of windings, so there is less risk of noise caused by resonance (Monolith Magnetics is a manufacturer doing high quality c-core transformers)."
At that time member Bonsai recommended a British brand of toroids (Tiger?) exactly because of their lower core excitation and screen between primary and secondary.
"The difference between stock toroidal power supply transformers and so called "audiograde" toroidal power supply transformers is not specified.
What generally is meant with "audiograde" is that manufacturers use transformers with higher power rating than necessary for the job.
Toroids are very efficient transformers because of their electromagnetic geometry; form and absence of air gap mean comparatively low power loss.
This means that, for a given power, toroids are smaller than their EI or whatever counterparts.
Another "technical" advantage is that toroids have rather low strayfields.
Dimension and weight are important economic reasons to use toroids.
The problem however with many toroids is core excitation, expressed in flux density T.
Everyone using toroids is familiar with the inrush "oomph", requiring NTC resistors or other means not to blow fuses, and sometimes "DC blockers" to prevent core saturation.
This high inrush current comes from the fact that, because of the efficient electromagnetics, the toroid responds instantaneously when line voltage is switched on.
EI, and other transformers with some sort of airgap and/or less efficient geometry respond less brutal; they therefore have less inrush current.
Winding toroids with less inrush current is not so difficult but normally not done.
To do so, flux density must remain low, preferably maximum 1 T, instead of the "standard" 1,7-1,8 T for off the shelve toroids.
For lower flux density it is necessary to wind more turns on a given core.
More turns mean more required winding space, hence a larger core is required for a low T toroid with the same power as a "stock" high T toroid.
So here "better" is larger, heavier, more expensive.
When you need a high quality toroid with even lower strayfields, find one with low T, and preferably a screen between primary and secondaries (ask the manufacturer for the specs).
A very good, but less acknowledged alternative in the "audiophile" arena is a power supply transformer wound on a c-core (in between toroid and EI for efficiency).
With a c-core it is easy to apply minor air gapping to prevent hectic inrush current, so we don't need NTC resistors or other "inrush current fighters" and DC blockers.
Besides, unlike toroids, c-core transformers (like EI transformers) can be wound tightly, with no "crossing" of windings, so there is less risk of noise caused by resonance (Monolith Magnetics is a manufacturer doing high quality c-core transformers)."
At that time member Bonsai recommended a British brand of toroids (Tiger?) exactly because of their lower core excitation and screen between primary and secondary.
I still recommend Tiger Toroids. I specify the flux density at 1T and always have a GOSS band fitted and an interwinding screen.
😊
😊
R-core transformers are the way to go but they are more difficult to find in Europe certainly in higher power versions. If one gets to know these then there is no turning back to toroids. Since I use low power amplifiers I can get away with sub 100VA types.
http://kitamura-kiden.co.jp/
Kitamura Kiden makes them even till 1000VA:
http://kitamura-kiden.co.jp/common/img/product/pdf/01_Rcoretrance.pdf
All a bit useless info as the devices are new and equipped with toroids that do hum 🙂 A customer is not supposed to think in technical solutions when devices are under warranty.
http://kitamura-kiden.co.jp/
Kitamura Kiden makes them even till 1000VA:
http://kitamura-kiden.co.jp/common/img/product/pdf/01_Rcoretrance.pdf
All a bit useless info as the devices are new and equipped with toroids that do hum 🙂 A customer is not supposed to think in technical solutions when devices are under warranty.
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Maybe we should start a separate thread in Solid State on transformers and not pollute the Pass Labs forum?
I opened a new thread over there https://www.diyaudio.com/community/threads/all-about-transformers.398342/#post-7327141
I opened a new thread over there https://www.diyaudio.com/community/threads/all-about-transformers.398342/#post-7327141
Hi MEPER, My listening position is 2 metres away. I don't have a shotgun microphone to record the sound from the distance you mention, although I can hear it clearly.
In post #167 it was said that the amplifiers are silent when no current is flowing to the loudspeakers.
This is contradictory with reality when it is about humming toroids and also with post #173.
BTW this thread won’t add anything to solve anything of issues as there is only 1 solution. You got confirmation by many and need to sort it out asap with the supplier. Please let us know when you have solved the return of the devices.
This is contradictory with reality when it is about humming toroids and also with post #173.
BTW this thread won’t add anything to solve anything of issues as there is only 1 solution. You got confirmation by many and need to sort it out asap with the supplier. Please let us know when you have solved the return of the devices.
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@jean-paul I keep being asked if the noise is coming from my speakers or if the volume is set at zero. I was trying to clarify, but I'm failing to be understood as I keep getting asked the same questions. I'm not technical, but I know where the abominable sound is coming from. It emanates from the amp. The noise does not change, no matter what the volume control position is. For the recording, I put it at zero.
It is well understood but other factors are of influence.
You are not satisfied about the purchase and the products have an error which really are 2 good and valid reasons to undo a deal. Just put your fist on the table and send them back/get your money back. You are barking up the wrong tree here.
Tip: transformers often hum as that is their nature. However the hum increases with their VA rating. Class A amplifiers consume a lot of power so their transformers are larger than the usual. Higher power class A amplifiers have a higher chance on humming transformers. Since toroids are used mostly and these have the highest chance of hum either mechanically or by any DC on the mains voltage and this only adds up. Now imagine you have 2 of such devices. What do you think that will result in!?
Therefor low power and/or class AB and D devices usually have less issues with humming transformers. These may hum but to a level that is not noticed. Check what power you need and buy accordingly. Now you know you dislike hum you’ll appreciate 1 amplifier instead of 2 as that is 1 transformer less that can hum.
You are not satisfied about the purchase and the products have an error which really are 2 good and valid reasons to undo a deal. Just put your fist on the table and send them back/get your money back. You are barking up the wrong tree here.
Tip: transformers often hum as that is their nature. However the hum increases with their VA rating. Class A amplifiers consume a lot of power so their transformers are larger than the usual. Higher power class A amplifiers have a higher chance on humming transformers. Since toroids are used mostly and these have the highest chance of hum either mechanically or by any DC on the mains voltage and this only adds up. Now imagine you have 2 of such devices. What do you think that will result in!?
Therefor low power and/or class AB and D devices usually have less issues with humming transformers. These may hum but to a level that is not noticed. Check what power you need and buy accordingly. Now you know you dislike hum you’ll appreciate 1 amplifier instead of 2 as that is 1 transformer less that can hum.
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The recording sounds like a predominant 100Hz buzz to me (see photo), with additional extra (quieter) harmonics that I can not figure out... it does not sound like the 50Hz buzz I would expect to hear from the toroidal transformer (see photo).
When I did a bit of research around what that INT-25 is, and its innards, I saw a few posts where people complained about cooking bridge rectifier heatsink (the colour of the heatsink in question changed.... due to excessive heat...). The (section of the) heatsink in question is shown with the red arrow (see photo).
So, if you touch that section of the heatsink and it seems much hotter than the rest of the heatsink area (on the right-hand side)... you know that there might be something wrong with... maybe quiescent current... the toroidal transformer might be okay (I think it is).
The above is just FYI... and I do believe that you should send the amplifier back to your dealer... they'll handle it.
When I did a bit of research around what that INT-25 is, and its innards, I saw a few posts where people complained about cooking bridge rectifier heatsink (the colour of the heatsink in question changed.... due to excessive heat...). The (section of the) heatsink in question is shown with the red arrow (see photo).
So, if you touch that section of the heatsink and it seems much hotter than the rest of the heatsink area (on the right-hand side)... you know that there might be something wrong with... maybe quiescent current... the toroidal transformer might be okay (I think it is).
The above is just FYI... and I do believe that you should send the amplifier back to your dealer... they'll handle it.
- Opening the device still under warranty by a layman is not good advice.
- Secondly you advise a layman to touch heatsinks in a powered up electronic device…..
- Thirdly it will make returning the amplifiers impossible so OP gets stuck with humming amplifiers.
Cooking bridge rectifiers…. If true this only justifies rejection of the devices.
- Secondly you advise a layman to touch heatsinks in a powered up electronic device…..
- Thirdly it will make returning the amplifiers impossible so OP gets stuck with humming amplifiers.
Cooking bridge rectifiers…. If true this only justifies rejection of the devices.
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Andy does not have to open the device to check heatsink temperature; he can check without opening.
Andy should send the amp back to the dealer ASAP.
Solving the problem is the responsibility of the dealer; Wayne should take action here also (he is too silent IMO).
When the problem remains....get your money back.
It does not help to continue speculating here.
@Extreme_Boky: your picture shows the power amp, not the Int25. The Int25 does not have the rectifier at the spot you indicated.
Andy should send the amp back to the dealer ASAP.
Solving the problem is the responsibility of the dealer; Wayne should take action here also (he is too silent IMO).
When the problem remains....get your money back.
It does not help to continue speculating here.
@Extreme_Boky: your picture shows the power amp, not the Int25. The Int25 does not have the rectifier at the spot you indicated.
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