It's in that article...I quoted the part that has to do with the response of a system to a change from equilibrium..
Are you saying this isn't accurate? And if so, why do you say that?
It's an odd conclusion based on anecdotal evidence - user preferences - gathered by the author. Transient response is related to bandwidth, and is usually viewed in terms of the upper frequency limit or the HF response, not LF. If you do not have the inductance necessary, you won't be able to produce the LF, you could of course argue there is not much music "down there", or you may even prefer the "quicker" sound, but not for the reason that the author suggested - the lower inductance somwhow makes the sound "better", it is simply that you are not hearing the low notes, if you like it that way, then more power to you, and your wallet will also thank you! 😉
I kinda thought there was a lot of mathematical basis for the argument, not just anecdotal evidence.
Take the term transient response out of the equation.. Is the cause and effect of the following not accurate?
Will the primary inductance of this kind of output transformer not affect the operating point current from one value to one much higher, thereby affecting the response of transitions from low frequencies to high frequencies?
Take the term transient response out of the equation.. Is the cause and effect of the following not accurate?
When the current in an inductor suddenly changes, there is an induced voltage in the inductor proportional to the inductance and the rate of current change. The magnitude of this voltage is to oppose the change in current. Normally this is written as:
...
This voltage acts to oppose the B+ voltage and hence limit the plate current in the output stage. Once this happens, the current begins to increase exponentially until the steady state dynamic operating point is reached
...
Because of the relation above, it can be seen that the larger the primary inductance of the output transformer, the slower the "transient response" will be.
Will the primary inductance of this kind of output transformer not affect the operating point current from one value to one much higher, thereby affecting the response of transitions from low frequencies to high frequencies?
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It "works" if you filter the low frequencies otherwise you get core saturation and high distortion.
In reality it sounds thin.
If you want good transtients you have to have a good high frequencie response without resonance. Nothing in that article is about that.
In reality it sounds thin.
If you want good transtients you have to have a good high frequencie response without resonance. Nothing in that article is about that.
Okay, so as I just asked jazbo8, if you take the term "transient response" out of the equation will the primary inductance of the output transformer not still affect the time response (for lack of a better term) from LF to HF and vice versa because of the induced voltage in the inductor proportional to the inductance and the rate of current change?
I realize it's not an inductor, but the winding has an inductance.. That inductance is a factor isn't it?
But the primary winding also has an inductance.. Also I see mr. Aiken refers to "leakage inductance" of the output transformer affecting transient response.
http://www.aikenamps.com/index.php/output-transformers-explained
Am I crazy here? (don't answer that.. lol)
And "when the current in an inductor suddenly changes, there is an induced voltage in the inductor proportional to the inductance and the rate of current change"
How about an alternate source of information on that subject:
Transients in an Inductor
Also, jazbo8, you said
I don't think the article I originally posted is saying that transient response affects LF.. It is saying that it affects HF response, but the fact that a larger primary inductance adversely affects that HF response gives weight to the argument that it's a tradeoff between high inductance/LF response, and low inductance/HF response.
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I guess he's actually saying the inductance affects transient response across the frequency spectrum.
The transformer has inductance when measured open-circuit... but it's not operated open-circuit. The coupled load from the secondary dominates. A single-ended amp will be operated class A - no net change in DC current with a transient (unless it's driven into a non-linear region or saturation, of course). A transient may cause a net increase in current in a class AB amp, but current is split between both power tubes, so it doesn't 'see' any inductance - the magnetic field cancels. Drive it into clipping or saturation and it's a different story... so don't do that.
So, if you want a " fast " transformer take the one with the highest hf rollof . That could be a transformer with a high inductance, all depends how good the transformer is made.
Of course the response should be with out resonance. Look at the 10kHz squarewave to get an impression of absance of resonance or not.
Of course the response should be with out resonance. Look at the 10kHz squarewave to get an impression of absance of resonance or not.
No, I don't believe so. At high frequencies, the primary inductance's reactance is so large, it can be treated as an open circuit, i.e., no longer having an effect on the output response. It is the leakage inductance of the primary and secondary windings along with the stray capacitance of the OPT that determine the HF response. There is nothing wrong with the equation he used for the inductance, but it's just applied at the wrong place... The equivalent circuit of the OPT at high frequencies is shown below, as you can see, Lp (the primary inductance) does not appear in it at all:
An externally hosted image should be here but it was not working when we last tested it.
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This makes me consider this statement from the article again.. And maybe I'm not understanding it that well. But it makes me think..
It seems as though he's suggesting that because there will be even harmonic distortion in this type of amp, this shift in bias current will occur especially when the output tube is being driven hard, and so there may be some effect to transition response?.. Any thoughts on that?
I'm enjoying this line of discussion.
Forum NoteThere is no need to quote the entire post just above yours. Please refrain from doing so.
I have cleaned up the clutter.
Kimbal....If you physically insulate a output transformer to allow operation at higher plate voltages, that may handle the primary to case problem, but what about the case of primary to secondary short where the secondary is floated and HT gets superimposed on speaker leads...that could be dangerous...
Modulation transformers (for AM radio transmitters) were often put up on 2 x 4's if a winding to case short occurred, and the radio station management was too cheap to have a spare on hand or order one in...but in this application, the primary and secondary operated off the same HT supply, which was around 2-3 kv for a 1 kw transmitter and 5 kv for a 5 to 10 kw transmitter....and the load was the RF final amplifier, not a speaker...
Edcor should build its products for 2500 v rms, which would save a lot of problems....
Modulation transformers (for AM radio transmitters) were often put up on 2 x 4's if a winding to case short occurred, and the radio station management was too cheap to have a spare on hand or order one in...but in this application, the primary and secondary operated off the same HT supply, which was around 2-3 kv for a 1 kw transmitter and 5 kv for a 5 to 10 kw transmitter....and the load was the RF final amplifier, not a speaker...
Edcor should build its products for 2500 v rms, which would save a lot of problems....
How do you know that they don't build them to withstand much higher voltages than they rate them for? They may not want to state the fact in order to avoid people pushing things to and beyond the limit. (Think about the voltages end to end in a high voltage plate supply transformer, and one of their larger PP transformers.)
I have purchased a number of transformers from them rated at 800VCT as well as 700V single secondaries and have had no issues with one rare exception.
I suspect building transformers to pass 2.5kV AC high pot testing could drive up the cost substantially.
I have purchased a number of transformers from them rated at 800VCT as well as 700V single secondaries and have had no issues with one rare exception.
I suspect building transformers to pass 2.5kV AC high pot testing could drive up the cost substantially.
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