Because the valves see the combined loads of each component which are clearly frequency dependent.
The loading on the output transformer changes in a frequency dependent manner using all or part of the windings.
This substantially changes the interwinding capacitance.
This is not a deniable phenomenon, but D Gillespie confirmed he had never tested it.
A component such as a typical multi winding 70v, 70V + CT, and 25V and 25V + CT wound transformer has the capacity to meet these needs, which I found by careful measurement.
(eg the brilliant MO200 amp, which was originally never designed for hifi).
In that case I could find a solid output to almost 23-30khz pretty flat, which normally could not exist.
So you are scaling the secondary windings to get approximately equal output from each driver so you don't have to pad any down?
NO I'm not. I don't need to do that.
Yes it's one of the most intelligent things Broskie wrote in years, after many ramblings and a practically non existent search engine on his site.
B-Wiring Part Two
That depends if you want to follow the crowd, or simply do things much better.
Your question?
I suggest you contact Jack at electraprint for a horse's mouth opinion of Broskie and his designs. (it's not polite).
It was a bit like my suggestions about the only place for Dynaco amps was,- heavy door stops to keep doors open...which he largely agreed with.
These obsessions with this "Aikido" thingy and PSRR leads to some twisted ideas, which were much easier resolved with proper power supply design.
Let's say, most of the ideas suggested were never tried, which Jack pointed out rather well, and if they had been, would not work as thought or planned.
Elliano is one of the half dozen or so people in the world I rate as being worth listening to, and they are not getting younger.
His obsession is with IMD, a not unhealthy thing, when you see the terrible results from KT66 and KT88, or those Russian "KT90, KT120"...et al.
This also happens in the standard configuration.
Yeah, that's not specific to what you're speaking of.
A Dynaco ST-70 is better than -1dB at 35kHz. A Citation II is -1dB at 80kHz/1W.
Unused copper on the secondary isn't helpful, that much I agree with, but if you have a 4 ohm speaker, how is what's being done here better than just using a single 4 ohm winding? (or having a pair of tapped 4 ohm windings so you can get multiple different secondaries)
I have no interest at all in what a Dynaco or Cit 11 can theoretically do.
I am certainly not interested in what they do at 1W.
I always measure my amps at full power on both channels.
It's that, that divided the sheep from the goats.
As for windings.
a 16 ohm winding with a tap at 4 ohms IS 2 windings.
The 4 ohm winding is the centre tap of the 16 ohm winding.
That gives you 2 x 4 ohm sections.
0-4 and 4-16, or maybe you haven't thought of that?
A 25V CT winding is the same principle exactly. - 2 x half 12.5V windings.
Talking in terms of voltage out makes much more sense, especially if the transformer maker has sensibly wound it, and used the same wire gauge everywhere.
I admit it's a black art, hence why I have no interest in Dynaco or Cit 11.
I have an excellent modern wound transformer from the USA which is an absolute replica reverse engineered from the original.
(won't say the make)
Why shouldn't I carry on using them?
I simply asked you to show some examples of Broskies claimed stupidity.
I asked for YOUR proof, you claimed it and you have the responsibility to provide proof, not Jack.
Also, your statement :
The 4 ohm winding is the centre tap of the 16 ohm winding.
That gives you 2 x 4 ohm sections.
0-4 and 4-16, or maybe you haven't thought of that?
Looks like it is YOU that has not thought about that
There is no such thing as 2x4ohm sections.
There are 2 windings with the same voltage, but this does not make them 2x4 ohm sections. There can only be either 1 section ( with or without the other section in parallel) loadable with 4 ohms, or 2 sections in serial loaded with 16 ohm, or 2 sections loadable with 8 ohm each. 2x4 ohm sections loaded as such would cut primary impedance into half as you sure know (or should know)
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You lack some basic understanding....
https://www.electronics-tutorials.ws/transformer/audio-transformer.html
Audio Impedance matching:
Function is of square, not linear relationship, I stand corrected-
However- How does this affect the physical space required difference of single 16 ohm V (2) 8 ohm windings?
Jim
One can use 2 half length wires of the full 16 ohm winding and load each length (winding) with 8 ohm and HALF the power over the FULL frequency band
Or:
Ideally, at the crossover frequency, load each winding presenting 2 loads, each 8 ohm and half power.
At frequencies far below or above cross over, one winding deliver the full power and the other winding none.
The fully loaded winding would have to see a 4 ohm load whilst the unloaded winding would have to see a infinite load.
So one could argue, is it 2 x 8ohm, or 4 ohm + infinite or 2 x 4ohm
As brought forward already, I also think it is easier to look at voltage ratios instead of impedance
Or:
Ideally, at the crossover frequency, load each winding presenting 2 loads, each 8 ohm and half power.
At frequencies far below or above cross over, one winding deliver the full power and the other winding none.
The fully loaded winding would have to see a 4 ohm load whilst the unloaded winding would have to see a infinite load.
So one could argue, is it 2 x 8ohm, or 4 ohm + infinite or 2 x 4ohm
As brought forward already, I also think it is easier to look at voltage ratios instead of impedance
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I don't have to do anything of the sort.
Lot's of people share info.
That doesn't give you a right to have it.
I most certainly have, and proved it works.
wrong.
It certainly does make them Match 2 x 4 ohm impedances.
You can chose either 0-4 (classic) or 4-16 (nobody thinks of).
Don't knock it 'til you try it.
Also wrong,
loading 2 x 4 ohm sections with 8 ohms would certainly NOT cut primary impedance in half.
You claim Broskie as being stupid and choose now not to back up your claim.
No wonder, pretty difficult if not impossible, he is a smart dude.
But you could at least have the decency to take back such an unsupported and insulting claim!
I said:
2x4 ohm sections loaded as such would cut primary impedance into half as you sure know (or should know)
According to you loading 0-4-16 or, what you call 2x4ohm sections with 8 ohm would not cut the seen primary in half, fine, have it your way, I prefer to put 2x8ohm instead of 2x4=8 ohm loads onto a 0-4-16 output
In my books 8 is half of 16 and a load half of what it should be cuts seen primary impedance into half
No wonder, pretty difficult if not impossible, he is a smart dude.
But you could at least have the decency to take back such an unsupported and insulting claim!
I said:
2x4 ohm sections loaded as such would cut primary impedance into half as you sure know (or should know)
According to you loading 0-4-16 or, what you call 2x4ohm sections with 8 ohm would not cut the seen primary in half, fine, have it your way, I prefer to put 2x8ohm instead of 2x4=8 ohm loads onto a 0-4-16 output
In my books 8 is half of 16 and a load half of what it should be cuts seen primary impedance into half
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I would not want to knock your discovery, you discovered something that is new for you and you are proud of it, enjoy, and hopefully you will make much greater discoveries in your future life.
But trust me, I really do not need to try it
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You still don't get it.
It's nothing to do with primary impedance.
If unequal speakers (ie a pair of dissimilar speakers) are used or one half is used for LF and the other for HF, on the secondary, the story is totally different, which is why it sounds different, and even measures (on studio mics differently).
(I can show you the traces)
Wiring 2 x 8 ohm speakers in series across the 16 ohm tap is what you are claiming to do.
That load is highly variable with frequency, and is essentially uncontrolled.
Anything from 32 ohms to 6 ohms is roughly the going rate.
That means the total impedance varies anything from 12-64 ohms from close to resonant frequency to 1khz, which is why valve amps are heavily criticised (by Harbeth amongst others) for being unresolvably boomy and impossible to correct.
Let's say 25v comes out of the 16ohm terminals when faced with a 16 ohm resistor, which is how all amps are measured.
The amp may measure flat.
When faced with an inductive load which has a frequency dependent element, things are totally a different story. (quite apart from NFB which can make things pure guess work).
It doesn't take a nobel prize scientist to figure out the nominal 39W it should make on a real speaker can vary from 9W into 64 ohms to 52W at 12 ohms (if it can supply the current).
Add to the fact each speaker would deliver HALF the power, would make it vary from 4.5W per driver to 26W each, which is way over +/-3dB.
As SPL is directly proportional to cone area it's clear the larger cone area you have at LF, the greater the SPL irrespective of input power.
By contrast
The 4 ohm tap is the CT of the 16 ohm winding.
If instead it's loaded with 8 ohms the 12.5V AC load will deliver 19.5W each, but,-
big but,- in practice many nominally 8 ohm drivers are anything from 4 -6ohms at LF,and LF is where all the energy is.
If you use 2 dissimilar speakers across each secondary half, the chances of variation are reduced by a lot.
so, if it follows each half of the secondary is loaded with bi wiring apart from one half being used for the LF, while the other half is used for the HF, - the amp then sees a totally different load line proportional to freq.
In theory both if drivers drop to 6ohms they will deliver 26W each, but in reality...
If the bass (LF) unit then go to 32ohms it delivers 4.8W. (poor bass), then it returns to normality around 60-150hz (great big boom).
This phenomemon is exactly what many in the BBC criticised very heavily, (they were using LEAK, Radford and others there), and why they took such efforts to try to equalise the speakers across the entire range.
Harbeth, Rogers, et al are all old ex-Beeb people.
Abbey road used the same sort of combos for many years, but with QUAD ESLs which have their own quirks worsened by a massive voltage step up with massive capacitive loading at anything from 15khz up...
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You were asserting that your HF performance was some kind of ground breaking achievement. It is not.
For me this would depend on how it was wound. If you bifilar wound the secondary to have two identical 4 ohm windings, sure. If you wind some turns on the secondary, pull a tap, then keep winding to make the rest of the secondary, I would be more hesitant to consider that two separate windings.
Have you ever measured the end to end system?
It's the only approach I use.
All consumer amps inc those you quoted, only measure into a load resistor at 1W.
This is an entirely false methodology, which accounts for a lot of that atrocious "tuby" sound.
If you start by measuring with high power outputs into true inductive loads with studio microphones (at the same time as recording the waveform and output into a DAW for posterity) not cheapy smart phones or other kludges, the world is a very different place.
I base my observations on objective measurement in a scientific way.
The fact is wiring a valve amp differently from the way you are used to, creates entirely different results which can only be explained by the stray capacitances and leakage inductance of the output transformer.
It's well known, loading up a whole winding, rather than just 50% or 70% of it - let alone a transformer with 3 or more seperate windings for NFB, CFB, 70/140V line or more very substantially affects its behaviour.
Fact is, you like others refuse to entertain such a notion, which is why few test for it, and even fewer know how to conduct a proper validated IMD and FR +THD scan test in proper real world conditions. (Not 1W at 1khz!)
Quote:
"If you start by measuring with high power outputs into true inductive loads with studio microphones (at the same time as recording the waveform and output into a DAW for posterity) I base my observations on objective measurement in a scientific way."
I've often wondered about resultant accuracy of tube OT outs into non inductive (resistive) loads w/ 'scope sweep conclusions...
Not saying this method isn't informative- but perhaps it's just a tool in the development stage??
IMO-
Substituting 'real world' inductive coils (speakers)... ranged from min to max output punched into a standardized studio full of audio pickups recorded on a spectrum analyzer would be a better basis for final evaluation?
Then,
We could debate those 'standardized' criteria- lol
Jim
"If you start by measuring with high power outputs into true inductive loads with studio microphones (at the same time as recording the waveform and output into a DAW for posterity) I base my observations on objective measurement in a scientific way."
I've often wondered about resultant accuracy of tube OT outs into non inductive (resistive) loads w/ 'scope sweep conclusions...
Not saying this method isn't informative- but perhaps it's just a tool in the development stage??
IMO-
Substituting 'real world' inductive coils (speakers)... ranged from min to max output punched into a standardized studio full of audio pickups recorded on a spectrum analyzer would be a better basis for final evaluation?
Then,
We could debate those 'standardized' criteria- lol
Jim
It doesn't take a nobel prize scientist to figure out that a transformer TRANSFORMS the secondary load impedance to the primary.
But since you seem to have not yet understood what I said earlier, I will give you a example:
Suppose we have a transformer optimized for a load of either 4 or 16 ohm (0-4-16)
The transformer has 2 equal secondary windings winding ratio is 10:1+1
Disregarding Rdc,Rac, coupling and other minor influences
winding ratio and secondary connected load impedance is all you need for defining the appearing primary impedance.
Reflected primary imp with 1x4 ohm load = 4 x 10:1 x 10:1 = 400 ohm
Reflected primary imp with 1x16 ohm load = 16 x 10:2 x 10:2 = 400 ohm
Reflected primary imp with 2x8 ohm load = 2x8 x 10:2 x 10:2 = 400 ohm
you can connect one 8 ohm load to 0-4 and the other to 4-16
Now, what happens if you load with 2 x 4 ohm instead of 2 x 8?
Should not be much of a surprise that the primary appearing impedance gets cut into half = 200 ohm
That a speakers real impedance is what it is, and will also get reflected to the primary as such, may have come
as a surprise to you and well be the reason for your rambling, but hey, life is full of surprises, get over it.
I will not take part in any further arguments about stuff that should be self evident.
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