Here is the formula
B = 1/(4.44.f.E.Ae.N)
The flux density is B, f= frequency (50 or 60 Hz), E = applied voltage, Ae = core cross sectional area and N = no. of turns.
The load current does not appear in the equation. The transformer size is selected based on temperature rise, copper winding fit, desired regulation etc. there are a lot of trade-offs but thankfully core manufacturers have that part of the donkey work so you just select the VA core you want. Note that for a given core size, the main thing you have to play with is N. One of the checks you have to make is the magnetizing current (no load primary current) Which you want to keep as low as possible so this puts some constraint on the range B and N can take given Ae.
IMHO, the magnetostriction noises of the core is only dependant of its amplitudes of variations, you can verify it by using fast trascients with large currents.
Just have a test 😉
Just have a test 😉
@MEPER hi, no direct contact. I didn't use my good mic from the Church as I intended. I used a rode lavalier inside a rubber housing for micing a person without the mic making contact with clothing or body. The recorder was my Sound Devices MixPre 3ii. Ironically at the time of recording, my amp was relatively quiet! Typical!
That sounds... unbelievably bad tbh. I didn't say much when it was first suggested to try and record the noise because I thought it would just not be possible without special conditions and mic/preamp etc. The fact you can actually get a recording from it seems at face value to suggest it is very noisy.
So where are you up to with rejecting it? I think its been a week since you emailed the dealer.
So where are you up to with rejecting it? I think its been a week since you emailed the dealer.
@Mooly I emailed my dealer [Audio Emotion, Scotland] last Sunday. I've had no response from them. I only wished I was getting their silent treatment from my amp! I did get a reply from the official UK Distributor [Select Audio], who I copied into the same email rejecting the amp and asking for a refund and collection of all their peripheral items [Multimeter, Hobotester, Mains Regenerator]. He denies Audio Emotion's claim that Pass Labs amps are "sensitive" to some mains supplies.
COPY OF MY EMAIL TO MY DEALER:
Dear Audio Emotion, Scotland.
Following a lot of advice on the hi-fi forum I have today informed my credit card company that I am in dispute with Audio Emotion.
I feel it is irrelevant if the amp works quietly at the other end of the country in Scotland or hundreds of miles away at Select Audio. My listening room is at home here in Milton Keynes and that's where it needs to work as expected.
I've had many different amps here over the past 20 years and they've performed silently and it is fair to expect that the Pass Labs Amp would too. I do not feel it is fair to expect me to pay thousands for additional equipment to get the Pass Labs to function here as it reportedly functions elsewhere. Plus there is no guarantee that after spending possibly thousands that I would successfully get the amp to perform as expected. As you have admitted previously: the Pass Labs amp is "sensitive" to certain electric supplies [unlike my other amps!] but Audio Emotion should have made me aware of this at the point of sale. I should have been warned that the amp may not be suitable for me due to it's "sensitivity" to some electric supplies and may put me on an endless shopping spree to try and fix its "sensitivity".
I would like the amp collected please and a full refund issued to my payment method.
It is three months to the day that I tried in vain to purchase an amp from Audio Emotion that was either undamaged or worked as expected. If the Leema's would have arrived undamaged I would have been perfectly happy with the first one. The Leema incident should not be counted in Audio Emotions 'Satisfaction Guarantee' as to quote a forum comment I did not reject it "because I wasn't fond of the bass", I rejected it due to being damaged on arrival.
I've already ended up paying Audio Emotion an extra £1700 over the Leema [due to never receiving an undamaged example] and understandably losing faith in the Leema brand.
I feel I've shown more patience than most would have. But now after three months of endless hassle and stress I feel there is no option for me than to be refunded.
Yours sincerely,
Andy Burton
Milton Keynes
Dear Audio Emotion, Scotland.
Following a lot of advice on the hi-fi forum I have today informed my credit card company that I am in dispute with Audio Emotion.
I feel it is irrelevant if the amp works quietly at the other end of the country in Scotland or hundreds of miles away at Select Audio. My listening room is at home here in Milton Keynes and that's where it needs to work as expected.
I've had many different amps here over the past 20 years and they've performed silently and it is fair to expect that the Pass Labs Amp would too. I do not feel it is fair to expect me to pay thousands for additional equipment to get the Pass Labs to function here as it reportedly functions elsewhere. Plus there is no guarantee that after spending possibly thousands that I would successfully get the amp to perform as expected. As you have admitted previously: the Pass Labs amp is "sensitive" to certain electric supplies [unlike my other amps!] but Audio Emotion should have made me aware of this at the point of sale. I should have been warned that the amp may not be suitable for me due to it's "sensitivity" to some electric supplies and may put me on an endless shopping spree to try and fix its "sensitivity".
I would like the amp collected please and a full refund issued to my payment method.
It is three months to the day that I tried in vain to purchase an amp from Audio Emotion that was either undamaged or worked as expected. If the Leema's would have arrived undamaged I would have been perfectly happy with the first one. The Leema incident should not be counted in Audio Emotions 'Satisfaction Guarantee' as to quote a forum comment I did not reject it "because I wasn't fond of the bass", I rejected it due to being damaged on arrival.
I've already ended up paying Audio Emotion an extra £1700 over the Leema [due to never receiving an undamaged example] and understandably losing faith in the Leema brand.
I feel I've shown more patience than most would have. But now after three months of endless hassle and stress I feel there is no option for me than to be refunded.
Yours sincerely,
Andy Burton
Milton Keynes
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That is a good email to the dealer. I think I would follow that up by telling them you are putting it in writing and sending it to their registered head office. I think you also have to now tell the credit card company this needs sorting out and ask for their advice. You have to keep the pressure up but remember the consumer law is on your side as long as you don't leave it all to long.
By them saying 'it is sensitive to mains etc' (which I think is nonsense tbh) also works in your favour as they are effectively admitting they know there are problems (again I think its nonsense but they have actually said it and so it can be used as evidence they should have told you)
By them saying 'it is sensitive to mains etc' (which I think is nonsense tbh) also works in your favour as they are effectively admitting they know there are problems (again I think its nonsense but they have actually said it and so it can be used as evidence they should have told you)
Sorry for your troubles, Andy, but you should have returned the amp earlier as many have posted.
Reading through this I'm still not sure whether the hum is 50Hz, 100Hz or 150Hz or something else which would give an indication of ths source of the trouble (I haven't listened to your recording others may have).
Toroidals were preferred by just about everyone compared to EI because they allowed higher maximum flux density. That meant manufacturers could make them smaller (see Bonsai's equation). But along with that there are two considerations - the flux density cannot be exceeded or the iron will certainly complain. First is that UK is 50Hz while states-side it is 60Hz. That means the transformer has to be bigger in the UK for the same power. Second the max voltage is 230+10% (253V) and whether there is an internal tap or not that should be the maximum input voltage for UK customers. (actually before harmonisation UK had 240V+6%=254.4V which in practice meant the supply never had to change.) I'm sure transformer manufacturers would be aware of usage requirements for different countries, which raises the question whether you have a rogue unit from a manufacturing "escapee".
It is a pity you did not follow up earlier advice for checking with someone else's setup as hum can be caused by earth loops in your inter-amp (CD, record deck etc) connections. That would have eliminated the doubt some expressed about the transformer.
It does seem that this is the problem. But it would not matter if the transformer were toriod or EI as someone posted. You can get EI's to suffer in the same way. I'm sure Wayne would help resolve this.
I think at least you have started the ball rolling to solve this issue.
Reading through this I'm still not sure whether the hum is 50Hz, 100Hz or 150Hz or something else which would give an indication of ths source of the trouble (I haven't listened to your recording others may have).
Toroidals were preferred by just about everyone compared to EI because they allowed higher maximum flux density. That meant manufacturers could make them smaller (see Bonsai's equation). But along with that there are two considerations - the flux density cannot be exceeded or the iron will certainly complain. First is that UK is 50Hz while states-side it is 60Hz. That means the transformer has to be bigger in the UK for the same power. Second the max voltage is 230+10% (253V) and whether there is an internal tap or not that should be the maximum input voltage for UK customers. (actually before harmonisation UK had 240V+6%=254.4V which in practice meant the supply never had to change.) I'm sure transformer manufacturers would be aware of usage requirements for different countries, which raises the question whether you have a rogue unit from a manufacturing "escapee".
It is a pity you did not follow up earlier advice for checking with someone else's setup as hum can be caused by earth loops in your inter-amp (CD, record deck etc) connections. That would have eliminated the doubt some expressed about the transformer.
It does seem that this is the problem. But it would not matter if the transformer were toriod or EI as someone posted. You can get EI's to suffer in the same way. I'm sure Wayne would help resolve this.
I think at least you have started the ball rolling to solve this issue.
"Reading through this I'm still not sure whether the hum is 50Hz, 100Hz or 150Hz or something else which would give an indication of ths source of the trouble (I haven't listened to your recording others may have).:
Perfect example of what is called "cooked air" here 🙂
Perfect example of what is called "cooked air" here 🙂
Swiping the audio into Audacity shows the dominant 100Hz peak (well actually 400Hz looks higher). The noise floor is very high of course.
Can we assume that noise is not from the speakers?
Volumen is turned all the way down or speakers disconnected?
Volumen is turned all the way down or speakers disconnected?
I also have my doubts, as I cannot assign this noise to any transformer, at least not at such a high sound level. I am confused about this recording.