Same here.
In fact I get regularly invited to their Conventions to show my stuff and talk about "how to resist the Chinese onslaught" or "how to keep a small Electronics Company running" , go figure.
In fact I get regularly invited to their Conventions to show my stuff and talk about "how to resist the Chinese onslaught" or "how to keep a small Electronics Company running" , go figure.
Τhe first Chines compact stereo sets contained in the same wooden case a cassette player, a radio and the amplifier.
In addition to the power transformer, they also contained one
smaller unconnected.
I believe that the only reason they installed the extra transformer was the increase in weight. 😉
Μany people believe that weight is a criterion of quality.
In addition to the power transformer, they also contained one
smaller unconnected.
I believe that the only reason they installed the extra transformer was the increase in weight. 😉
Μany people believe that weight is a criterion of quality.
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That's supported by consumer psychology as well. It's one of the few variables that shows a gender split. Male participants rated heavier products as higher in quality. Female participants didn't show this effect. Go figure...
Tom
That is true. Historically heavier things were considered of higher quality, better made. Even today I still have that bias, regardless of the fact that it is not always the case.
There actually is an indicative quality aspect borne of quantity when it comes to transformers. I'm surprised it's being overlooked here. Transformer capacity can be determined relatively just by weight. For example a 100wpch amp weighing 30lbs compared to a 100wpch amp weighing 50lbs will very likely have a performance rating difference in terms of over all capability. The heavier one most probably has a much bigger power transformer indicating a lot more over all capability. This will probably result in better peak performance. I would challenge anyone here to name a bad, or even mediocre sounding mid power amp with large trannys and heavy. They are all upper tier examples. A faceplate or chassis may add a few lbs but noithing like the difference a tranny can make. Hence the Chinese hoodwink.
Several years ago when I too much time on my hands recovering from shoulder surgery, I compiled a list, by weight, of a hundred or so transformers and used Excel to fit a curve to the weight/VA ratio; the formula for which is :
y = 0.4708569301x2 + 20.6319462703x - 8.8450005793
where y = the VA rating of the transformer, and x is the weight in lbs.
Seems to be accurate within 10% or so on average. As always, YMMV...
Note: this is for standard EI core transformers without an exterior shield.
Hal
y = 0.4708569301x2 + 20.6319462703x - 8.8450005793
where y = the VA rating of the transformer, and x is the weight in lbs.
Seems to be accurate within 10% or so on average. As always, YMMV...
Note: this is for standard EI core transformers without an exterior shield.
Hal
May be. The area core of a trafo is related to sqrt of its power, and the weight must be related to core size^3 times the iron specific wheight.
Yes - I did one as well based on the core cross sectional area but never was really happy with it as the errors grew too large at increased sizes. Mostly a problem with finding enough valid data to make a workable sample size. Just decided to concentrate on the weight as that was readily available in trustworthy form from Stancor, Hamond and such.
Hal
Note: the formula for the weight is accurate through about 40 lbs / 1500 VA - after that if follows the average of the samples I had but the samples themselves vary more than I'm comfortable with at larger weights. Then again, how often are transformers of that size even used? I use it to get a feel for salvaged transformers or when I am trying to find a replacement for an unspecified one. To be sure I made a test fixture that plots the regulation vs load - I wish I had been saving that data to plot. I think I remember seeing somewhere online the relationship of the VA capacity vs acceptable regulation but I don't remember where.
Hal
Hal
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There are three other alternate functions that also will fit the data - some do better with smaller values and some are better at larger. The one given previously offers a good middle of the road fit for all cases. On the SS I made I use a function that uses a combination of all of them depending on the weight.
y=(16*(POWER(x,1.22)))-1.25
y=1.2484521+(15.977198*POWER(x,1.2178647))
y=EXP(2.6341138+(1.2806771*LN(x)))
y=(16*(POWER(x,1.22)))-1.25
y=1.2484521+(15.977198*POWER(x,1.2178647))
y=EXP(2.6341138+(1.2806771*LN(x)))
Thanks for both your data ad Mark Johnson´s, plus the added effort of finding a Math Rule/Law (beyond plain stating number "tables").
Very useful to a lot of people.
Personally I am a dyed in the wool oldtimer guy who always needed design data "now" to design stuff which had to be built and delivered to customers in a short time, so regularly used graphs, nomographs, tables, etc. which I measured myself using available stuff, as in measuring unknown maker EI steel; available graphs in (US printed) books and magazines showed US only available Armco, Permalloy, Allegheny steel which for us was the stuff of dreams.
No simulation either, available computer for me was (time shared of course, had 1 hour a week available as a student) a weak IBM1620 or a mighty IBM360, so like it or not I had to roll up my sleeves, measure and graph, no other practical option, that´s why appreciate so much you guys doing the same 🙂
Simulation is fine, a mighty time saving tool, but first you need good models, and then check whatever you bought last week and is sitting on your bench does match them ... not always happening 🙁
Very useful to a lot of people.
Personally I am a dyed in the wool oldtimer guy who always needed design data "now" to design stuff which had to be built and delivered to customers in a short time, so regularly used graphs, nomographs, tables, etc. which I measured myself using available stuff, as in measuring unknown maker EI steel; available graphs in (US printed) books and magazines showed US only available Armco, Permalloy, Allegheny steel which for us was the stuff of dreams.
No simulation either, available computer for me was (time shared of course, had 1 hour a week available as a student) a weak IBM1620 or a mighty IBM360, so like it or not I had to roll up my sleeves, measure and graph, no other practical option, that´s why appreciate so much you guys doing the same 🙂
Simulation is fine, a mighty time saving tool, but first you need good models, and then check whatever you bought last week and is sitting on your bench does match them ... not always happening 🙁
If there is actual interest I could perhaps do some simulations on the core topic here, slapping an unused transformer ontop of a working one and seeing the change in field distribution. I have access to some fancy simulation software and remote computing power so it shouldn't be too hard to whip up something.
We've already agreed that doing this has no purpose besides maybe helping mechanically dampen transformers that would rather be paint mixers, but maybe I could help shed some insight into the actual impact of the field lines that have been so discussed over the last almost 200 replies 😂
We've already agreed that doing this has no purpose besides maybe helping mechanically dampen transformers that would rather be paint mixers, but maybe I could help shed some insight into the actual impact of the field lines that have been so discussed over the last almost 200 replies 😂
Got access to Ansys? The microwave version I can run (HFSS) unfortunately is **** poor at a low frequency solution.
I’m sure the field lines do change visibly. But do the actual terminal characteristics change? If so by how much? If an amp really is sensitive to -80dB external fields, maybe it should be avoided. Living under HT power lines would probably eff it up too.
I’m sure the field lines do change visibly. But do the actual terminal characteristics change? If so by how much? If an amp really is sensitive to -80dB external fields, maybe it should be avoided. Living under HT power lines would probably eff it up too.
I've got access to Comsol Multiphysics, I could probably run this at pretty decent resolution if I just leave it to do its thing for an hour or two. Not really sure if I could do terminal characteristics extensively but I could probably look for any changes in inductance in the windings.
Either way it's a few hours of work, not going to bother if there are not several people who would be interested in the probably next to zero change
If you calculate the self and mutual inductances, one could calculate if there is going to be a difference in DC voltage coming off the power supply.
Not a simple undertaking. So far at least a couple of EM related effects due to proximity of soft magnetic mass have been mentioned :
1. Change of transformer behavior measurable on output of PSU.
2. Change of stray field distribution that interact with other parts with EM field sensitive component such as other transformers, inductors,, plates and filaments on the tubes, ferromagnetic leads, interconnects and perhaps a few more with net effect measurable on amp output.
An expert may know a few more than an amateur like me.
Also the sim does not touch probable microphony issue.
Best to rectify a pathological system on the bench.