Topic: Surplus amps

[ATJr.]

the choice of which components, caps in this case, to use depends on, availability, costs at the time of the design and production run of the amps, i can not think of any other consideration.

ah, amps rated for 8ohms will have lower capacitance values than amps rated for 4ohms, likewise, caps will be smaller in value for amps rated at 40watts say, than that for 200watts say.

[ATJr.]

Toroids have less weight than EI for the same power rating.  For it to be heaveir than an EI, must have greater power rating. 

agreed, but this is not to say that torrroids are better tha EI's... not by a mile...

[dana]

the positive and negative rails will surely give you a definite clue as to power ratings. just to give you examples:

rails of +/- 35volts will give you about 40 watts at 8ohms,
rails of +/- 42volts will give you about 80 watts at 8ohms,
rails of +/- 55volts will give you about 120 wattts at 8ohms,
rails of +/- 75volts will give you about 200 watts at 8 ohms,
rails of +/- 85volts will give you about 300 watts at 8 ohms,
rails of +/- 160 volts will give you about 1500 watts at 8ohms.

so if you look at the filter caps you will surely get an idea as to its power rating.
 there is more, the number of output power devices will likewise give you a clue as to the robustness of the power amps, while many amps get by with just a pair for a stereo setup, this indicates that the amp is most likely for 8ohm loads only, amps rated for 4ohms will have more than just a pair of output devices.

Sir TonyT,

What is the formula u used to get that estimate?Mahirap i-memorize them . Is it (VCC^2/RL=8ohms)(efficiency factor)?
Also, just by looking at the Filter Caps,  is it safe to say that the working voltage label is about times 2 of the actual?
Trying to refresh my electronics...wala na kasi sa mainstream e...

Thanks

[ATJr.]

the formula is not that important,i do not memorise them, it is the principle involved that will guide you through....

for sine waves: Erms = Vpk to pk/2.8, example, 220volts = 630/2.8,
Vpk to pk in our case is the absolute value of +/- Vrail, so a rail of +/-35 = 70volts. this is first consideration.
we also need to take into consideration the saturation value of the output transistors which can be 2.5volts say, and also the regulation of the power transformer used. these are taken into consideration when designing power amp output stages.

are you still with me?

now Erms = 70/2.8 = 25

for an 8ohm load power then becomes P = (Erms)sqaured/8ohms = (25x25)/8 = 78 watts

so then why is it that i said it is good for 40 watts?

it is because, the 25volt is ideal, in practice we will get lower than than 25 volts because of sag in voltage of the power transformer, losses in power transistor output, and distortion limitations.

[ATJr.]

just by looking at the Filter Caps,  is it safe to say that the working voltage label is about times 2 of the actual?

look at it this way, suppose the amps has two capacitors with lables, 47,000/50volts, then we know right away that the rails can not be 50 or more volts, it will be less, up to 35~42volts most likely.

[aHobbit]

agreed, but this is not to say that torrroids are better tha EI's... not by a mile...

       

My dual monoblock NEC is EI !!!     

Pahawak AU-D907Limited        

[ATJr.]

      

My dual monoblock NEC is EI !!!     

Pahawak AU-D907Limited        

i hope you will find this interesting. http://www.parasound.com/pdfs/JCinterview.pdf#search='john%20curl%20interview'

[dana]

Sir TonyT,

Thanks for refreshing  that principle   ,very well explained formula estimate. ..Pout rms= VCCrms^2/RL...(with sag/load/distortion considerations....).

It will surely come handy to those who are into 'pier hunting' and peeping at the innards of those amps.
BTW, the pier people/sellers label their amps power based on the consumption label at the back .

[av_phile1]

agreed, but this is not to say that torrroids are better tha EI's... not by a mile...

If we're talking about efficiency, they are better by more than a mile. 

[aHobbit]

i hope you will find this interesting. http://www.parasound.com/pdfs/JCinterview.pdf#search='john%20curl%20interview'

Thanks for the read! Buti na lang, I have not started on the circuit of my DIY pre-amp.

[ATJr.]

BTW, the pier people/sellers label their amps power based on the consumption label at the back

 ;Dkaya nga sana atin-atin na lang to at huwag nang makarating sa kanila....

[ATJr.]

If we're talking about efficiency, they are better by more than a mile.

this is highly debateable, trust me.

[bulletman]

Can I ask where to buy amplifier just for passive subwoofer?

[parasmi]

sir, I have a Sony power amp pwede stereo or mono. pm me if your interested  Or are you looking for a subwoofer plate amp?

Can I ask where to buy amplifier just for passive subwoofer?

[aHobbit]

sir, I have a Sony power amp pwede stereo or mono. pm me if your interested  Or are you looking for a subwoofer plate amp?

parasmi, what model and how much?

[av_phile1]

this is highly debateable, trust me.

If there's anything I can distinctly recall from my Electrical Engineering days, it's this fact that both textbooks and my professors at UP drumbeat on my head -  the superior efficiency of toroids.  

[ATJr.]

the alleged superiority of torroids is nothing but HYPE... me i don't believe everything my professor tells me..it's a case by case basis anyhow

[rascal101]

For switching power supplies at least, the preference of torroids over EI cores is due to size constraints.

[aHobbit]

the alleged superiority of torroids is nothing but HYPE... me i don't believe everything my professor tells me..it's a case by case basis anyhow

     he he he! Me too!

Sometimes, I have to tell them!    

For power supplies at least, the preference of torroids over EI cores is due to size constraints.

probably cheaper! It can carry more power for its size ... but at what trade-off! 

translation: to cut manufacturers' cost at consumers' expense! ... and to have it unnoticed, advertise the hype! ... what's new! 

[av_phile1]

the alleged superiority of torroids is nothing but HYPE... me i don't believe everything my professor tells me..it's a case by case

Really? Says who?   tell me I might recommend him for a nobel prize in physics.    Show me any scholarly works that says so. 

[aHobbit]

maybe anybody can site what is the typical efficiency of an EI core - transformer being a stationary motor itself & and then proceed to tell what is the efficiency of the torroid - and last, show what you really mean SUPERIOR efficiency (e.g. space usage, sonic application, welding application)

[av_phile1]

That shouldn't be too difficult.  I was amazed  google returned sites that are clearly unanimous about toroids being more efficient - just confiming, affirming with unmistakable unambiguity what my professors and textbooks told me 30 years ago.    It was interesting to relearn online. I'll let them speak for themselves.

Here's a sampling from specific manufacturers:

The key to all toroidal transformer advantages is its efficiency.

Toroids are far more efficient than conventional laminated types. Toroidal transformers can offer extremely high efficiency, and figures of 96% and better are achievable

The toroid is the ideal shape for producing a transformer with the minimum of material

Gaps are bad in most power transformer applications. Tape-wound toroidal cores don’t have any

Toroidal transformers are quieter and more efficient than conventional EI transformers ....

The magnetic flux in a toroid is confined to the core, preventing its energy from being absorbed by nearby objects.

Because they are more efficient, toroids are generally up to 50% lighter than conventional E-I type transformers

The circular tape wound core, with no airgaps, and with primary and secondary windings uniformly distributed around the core, "locks in" the magnetic field and makes the transformer very quiet and efficient. The overall efficiency is typically 95%.

40% more efficient than EI type.

Toroidal Power Transformers are made with tape wound cores. The tape wound cores provide an almost perfect magnetic circuits to minimize losses, fringing, leakage, distortion, and provide good magnetic shielding. It also decreases the magnetization force required to produce a given flux density. It is much more efficient than E-type lamination cores

Due to its unique construction, toroids are typically between 15 and 30%more efficicent than the conventional type. Higher VA rating makes toroids more efficient.


From neutral  technical discussions:

Toroidal Transformers employacylindrical core wound with a copper wire. This transformer does not suffer from magnetic fluxleakages which usually occurin the coil of thetransformer. Hence,thecoils of the toroidal transformers arecharacterized with higher efficiency,and there is no interference in operationby leakage fluxes originating in the coil.

C-cores are not as efficient as toroidal cores, but are easier to wind with conventional coil winding machines. The overall efficiency lies between the E-I core and the toroidal......The toroidal core has no air gap at all, and is therefore more efficient (magnetically speaking)

Because of their construction tape-wound toroidal transformers are more efficient and produce less acoustical and electromagnetic noise than standard E-I transformers.

The strip construction ensures that the grain boundaries are optimally aligned, improving the transformer's efficiency by reducing the core's reluctance. The closed ring shape eliminates air gaps inherent in the construction of an EI core

From a tube DIYer

l chose the Plitron toroidal transformer because of its exceptional bandwidth: -3 dB at over 200 kHz, the result of high primary inductance (the good stuff) and low leakage inductance (the bad stuff-- kind of like HDL and LDL cholesterol)-- much better than can be achieved with a conventional EI transformer.

I probably could go on forever.  But this is getting to be a bore.    

[aHobbit]

what my professors and textbooks told me 30 years ago ... 40% more efficient than EI type ... 

Honestly speaking, I refuse to doubt you.   

based on the post, the toroid can have as high as 96%, and toroid is 40% more efficient than EI. doing the math, this puts the EI core at about 69%. 

If it is power efficiency you are talking about, this is easy
            Pout
eff = ------------- x 100
             Pin
(do you remember your textbook?)     

And transformer (EI or torroids) are basically efficient motors averaging more than 90% in efficiencies. 69% efficiencies are worse than motors’ efficiencies averaging 70-80% - and this is simply not true! 

Our 3-phase HV adaptation transformers on our new 160KVA UPSs are not torroids. I look up at the post beside out building and really, I wonder whether it has an oil-cooled torroids inside it. I peek in the substation beside the former Manuela in EDSA/SHAW – could it be torroids in there? Honestly, I don’t know. I have to confirm with my brother in Meralco to verify it for me, and will report it back to you.   

If you mean by efficiency as the amount of material you put into it vis-à-vis the power output, probably you are right      – but power losses, no, you’re not (they average basically the same as torroids)! SO this should clear that cloud of your ‘so called’ efficiency.    

Toroidal Transformers employacylindrical core wound with a copper wire. This transformer does not suffer from magnetic fluxleakages which usually occurin the coil of thetransformer. Hence,thecoils of the toroidal transformers arecharacterized with higher efficiency,and there is no interference in operationby leakage fluxes originating in the coil.

The overall efficiency lies between the E-I core and the toroidal......The toroidal core has no air gap at all, and is therefore more efficient (magnetically speaking)

Because of their construction tape-wound toroidal transformers are more efficient and produce less acoustical and electromagnetic noise than standard E-I transformers.

The strip construction ensures that the grain boundaries are optimally aligned, improving the transformer's efficiency by reducing the core's reluctance. The closed ring shape eliminates air gaps inherent in the construction of an EI core

I will also ‘paste’ my source finding regarding the torroid performance in a sound gear – but will reserve it for now until I search my ‘mahiwagang baul’. 

l chose the Plitron toroidal transformer because of its exceptional bandwidth: -3 dB at over 200 kHz, the result of high primary inductance (the good stuff) and low leakage inductance (the bad stuff-- kind of like HDL and LDL cholesterol)-- much better than can be achieved with a conventional EI transformer.

I probably could go on forever.  But this is getting to be a bore.    

Also, your tube DIYer – whats the purpose of his torroid, for power output or for audio output? if it is for power output, I dont know what the bandwidth has got to do with it!      If it is for audio output, oh well, its not my taste for amplification, sorry – but the tube amp need it by force, not by choice!


Don't worry ... i am not getting bored ... now I am having more fun !     

[av_phile1]

By all means, do.   I was just talking about efficiency anyway.  Just so happens those sites I pasted talked about other advantages of toroids which are just fine and simply confirm what I've learned.   And that DIYer has his reasons.  Everyone has his reasons for doing what he thinks is right.  And if you think you've discovered something contradicting what those textbooks, professors and other pundits  have written about regarding the superior qualities of toroids, by all means post them. Not just here but have it published in a scientific journal.  Like I said, someone just might nominate you for a Nobel prize in physics.   

[ATJr.]

Honestly speaking, I refuse to doubt you.   

me too.

small EI's will have lower efficiency than torroids of the same va capacity, this i will grant...but as transformers grow in va capacity efficiency approaches 100% thus torroids will have no advantage as far as efficiency is concerned.

the claim that torroids are superior to EI's is a general comment and so i refuse to accept that.

[JojoD818]

sa Audio Lies and Myth thread ba ang bagsak niyan? 

[rascal101]

From our magnetics dept. Take your pick ...

Bobbin Type Transformer

Advantages:

A.  Low Leakage

B.  Low Capacitance


Disadvantages:

A.  High On Thermal

B.  High Noise

Toroidal Type Transformer

Advantages:

A.  Lower On Thermal

B.  Low magnetic strayfield emission level

D.  Less Noise magnetic level

Disadvantages:

A.  High Leakage

B. High Capacitance

[aHobbit]

...   I was just talking about efficiency anyway.  ... And if you think you've discovered something contradicting what those textbooks, professors and other pundits  have written about regarding the superior ... huh, whats that again - EFFICIENCY?

I have not read it from my textbooks ... probably your school uses another text than my school!    Probably, you missed something, superior efficiency in what? (power handling?) or probably you meant a difference of 2% in power handling efficiency is superior? (para kung semantics lang ito, we need not clarify anything at all).

.. And that DIYer has his reasons.  Everyone has his reasons for doing what he thinks is right.  ...

Yup! and we don't question them ... the idea is, I did not get what you mean SUPERIOR efficiency from that DIYer! it is that simple!  Unless you want me to reaadily believe in his observation/ assessment/ opinion/ or imagination. 

..  Like I said, someone just might nominate you for a Nobel prize in physics.   

I will tell that person - dont do that ... you might end up a joke ... the fact that you refer to me and will nominate me for, is part of the general textbook.    My head is still spinning - what is this SUPERIOR efficiency in the first place?


... ok, i want to be sober!  ... Meralco uses 'O' core type in substations & posts - probably due to ease of maintenance? Windings are separate from each other, not on top of each other! dual bobbin?

[aHobbit]

as promised, indulge yourself ...

http://www.pearl-hifi.com/06_Lit_Archive/07_Misc_Downloads/Toroidal_Trans_Myths.pdf

“In solid state it is generally accepted that a good toroid is the best thing going…”

It is? I must have missed that.

So you consider a transformer "a good thing" which has the following fundamental flaws:

1) no airgap (an EI Transformer invariably has a distributed airgap even if tiny) and very little iron in the core, leading to early saturation, waveform distortion and high sensitivity to DC offset in the mains and "flattopping" and which in the real world as a result run hot, often hum and are inefficient, unless extensive external circuitry is appended to offset these issues which do not exist in EI Transformers

2) low primary inductance which as a result stores little energy which could be used to "bulk up" the current flow on the rectification peaks (measure the primary current waveform of EI vs. Torroid to see what I mean)

3) Exteremely high coupling capacity between sections which makes sure all mains related junk sweeps right through the PSU and onto the supply rails.

4) Due to construction and the problems around high shunt capacitance and low leakage inductance makes snubbing out the ringing from the reverse switching all the more difficult

Given the drawbacks compared to more traditional shapes of mains transformers it strikes me that the only thing Torroids offer is more profit to the transformer maker and/or equipment maker as they are MUCH CHEAPER to make and in materials than EI Types.

I use torroids where I have no no real choice and fit the required circuits to reduce their drawbacks but would prefer to use EI transformers of suitable construction instead and to just connect them.

====

“So if Toroids are cheap to make why are they many times more expensive than conventional designs? Is it because a lot of us fall into the newer is better trap?”

It seems in the US the market supports a higher pricing for torroids than for EI Transformers, in Asia and Europe this is not the case. If cost/size/weight is a concern you fit a torroidal, if quality is more important R-Core, C-Core or EI types are used.

toroids aren't necessarily more expensive.

I agree with you on large cross EI section core....but there are advantages with toroids......far lower winding resistance and Z for the same VA with an EI and the regulation factor is nearly halved. What many don't realise .....most toroids are pile wound and have a temp rise limitation whereas a well wound EI can gracefully stew.

[aHobbit]

My last take ... torroids are used to cut your gears' manufacturing cost, and sell it to you at higher consumer cost ... translated to the bigger seller profits