When Using 4, 8, or 16 Ohm Taps....??

[zozoe]

Greetings, I'm trying to get a trusted opinion, or fact, about any possible sound/performance issues when using one's 4 ohm tap with the appropriate 4 ohm load as opposed to the 16 ohm tap with an appropriate 16 ohm load.....
I once read that the more windings of the PT that are used (16 ohm), the better the sound...
Truth or bunk??
Thnx 🕉

[xtian]

Small data point: I've never detected a difference.

[dorrisant]

I have read that when using the 16 Ohm tap as opposed to any others, that the more turns around the core can effectively squeeze more harmonics out of an OT. Don't know if that is true, never tested it.

[martin manning]

Zozoe, you asked this same question or something close to it a couple of years ago: https://ampgarage.com/forum/viewtopic.p ... 81#p417881

[Stevem]

If you don’t think it sounds better that’s fine and dandy, but then let’s look at wattage and the heat it produces and dissipating that heat and transformer life due to heat.

In particular where looking at the secondary side of the output transformer here.

All three taps can produce the same peak wattage, but would you rather load all of the amps power thru a short length of wire, or a long length of wire.

This is the difference between using the 4 ohm secondary tap and the 16 ohm tap.

[wpaulvogel]

It really depends on how it’s wound but most guitar amps output transformers are just a series connection where the 4 ohm tap is half the secondary, 8 ohms is 1.14 times the 4 ohm and 16 is the full length. The important thing is that when series wound, the full secondary conducts all the current and therefore it should be better. A properly wound transformer most completely fills the whole lamination window with copper wire so it’s as efficient as possible. Some transformers are wound with the 4 ohm being the whole winding split and connected parallel and 16 ohm series which would use the whole secondary in either case but this is uncommon and simple switching is difficult.

[brewdude]

I understand the rationale behind the idea that more winding might be beneficial…
Does this imply that a multi tap OT played at 4 Ohms would sound different then an OT wound strictly for 4 Ohms?

Then there is the old school stereo solid state school of thought that expected more power run at lower Ohms.

[pdf64]

… let’s look at wattage and the heat it produces and dissipating that heat and transformer life due to heat.
In particular where looking at the secondary side of the output transformer here.

Ok, what info do you have in regard of the above?

… would you rather load all of the amps power thru a short length of wire, or a long length of wire.

I don’t understand how the length of wire is relevant here? It just needs to be sufficient.
That’s largely determined by the number of turns required for the desired ratio and the wire gauge.

This is the difference between using the 4 ohm secondary tap and the 16 ohm tap.

I think that the differences go somewhat beyond the relative wire lengths used for the windings.
From my very limited understanding, transformer design has a multitude of constraints and compromises, and the results of the choices made may not be intuitive or obvious.

Some recently revised Hammond info contains bode plots that may confound generic presumptions regarding the topic of this thread, eg https://www.hammfg.com/files/parts/pdf/1750N.pdf
(full secondary winding has poorer performance than taps)
https://www.hammfg.com/files/parts/pdf/1760K.pdf
(full secondary winding has better performance than taps)

… any possible sound/performance issues when using one's 4 ohm tap with the appropriate 4 ohm load as opposed to the 16 ohm tap with an appropriate 16 ohm load.....
I once read that the more windings of the PT that are used (16 ohm), the better the sound...
Truth or bunk??

My understanding is that humans are genetically programmed for pattern recognition, even to the point of thinking they perceive them where none exist.
Also they apply a smattering of knowledge to complex subjects to try and make some sense of them.
Whichever, hence the heap of baseless hypothesising on this and countless other topics.

[Stevem]

Mass by means of wire diameter or lenght is still potentially available for use as a heat sink.

[pdf64]

Mass by means of wire diameter or lenght is still potentially available for use as a heat sink.

I don’t understand the relevance? The winding mass is there whether or not all the turns are in circuit.

[Phil_S]

I feel reasonably certain the answer to the OP's question is that it is the sound of one hand clapping, or possibly a tree falling in the woods with no one there to hear it. Seriously, I don't honestly believe that anyone over about 25 years old is capable of perceiving any difference, if there is one, with the naked ear because, after about age 20, gradual and lifelong hearing decline sets in. If you play out using a 50W or higher amp without any loss prevention precautions (like ear plugs or muffs,) your hearing will go downhill faster. It's a fine and moot point. I suggest doing whatever is most convenient and to never think about it again!

[R.G.]

Greetings, I'm trying to get a trusted opinion, or fact, about any possible sound/performance issues when using one's 4 ohm tap with the appropriate 4 ohm load as opposed to the 16 ohm tap with an appropriate 16 ohm load.....
I once read that the more windings of the PT that are used (16 ohm), the better the sound...
Truth or bunk??

Bunk. Other factors, notably speakers reacting to drive impedance, have a real, measurable effect, though. This is probably what's behind the "more wires is gooder wires" myth.

I have read that when using the 16 Ohm tap as opposed to any others, that the more turns around the core can effectively squeeze more harmonics out of an OT. Don't know if that is true, never tested it.

Not true. "More harmonics" could only come from either more distortion or exciting different resonances to make the existing harmonics more prominent. Transformers do have distortion, from the effect of the iron loading in the primary inductance (... B-H curve nonlinearity) and the drive impedance(not the load impedance on the secondary), but this is entirely a volt-time (or volts-frequency) effect on the primary side. Secondary turns have nothing to do with it.
Reading nearly anything at all is possible on the net, as everyone feels like an expert. Dunning-Kruger rules the net.

It really depends on how it’s wound

Put a full stop right there and you're completely right!

I understand the rationale behind the idea that more winding might be beneficial…
Does this imply that a multi tap OT played at 4 Ohms would sound different then an OT wound strictly for 4 Ohms?
Then there is the old school stereo solid state school of thought that expected more power run at lower Ohms.

That rationale is one of those things that seems like it ought to be right - but just isn't.
There is a multi-way tradeoff in designing transformers. You have to balance how much iron area is encircled by each turn, the total path length of the magnetic flux through the iron, any air gaps in the magnetic field path through the iron, window area through the iron to put turns of wire into, primary to secondary turns ratio, heating in the iron, heating in the copper, total magnetic field intensity in the iron, and then inter- and intra-winding inductances and capacitances. With all of those to consider, people who haven't wasted a goody chunk of their lives studying and practicing transformer design fall back on what humans do - guessing and opining on what they think they see. Humans are pattern matchers - they automatically generate patterns to perceive. I believe that this set of ideas is one of those perceived patterns.
So no, it doesn't imply that a multi-tap secondary > necessarily < sounds different than another OT wound just for 4 ohms. But two such transformers might well sound different. Or the same - what matters to the sound of a transformer is where each turn of wire sits compared to all the other turns. That directly affects self- and distributed capacitance and leakage inductance, which really does affect the frequency response.
A more accurate generalization is that no two OTs even of the same manufacturer and part number sound the same unless the quality control of the coils during winding is very, very tight. It's easy to find tonal differences, but hard to accurately pin those to anything visible on the outside of the transformer.

[...]
I don’t understand how the length of wire is relevant here? It just needs to be sufficient.
That’s largely determined by the number of turns required for the desired ratio and the wire gauge.

Agree. I think Stevem was getting at the idea of complete window filling with turns, which is kind of right.

I think that the differences go somewhat beyond the relative wire lengths used for the windings.
From my very limited understanding, transformer design has a multitude of constraints and compromises, and the results of the choices made may not be intuitive or obvious.

Yeah. I wrote my rant on transformer design before reading your post. Yep - it's complicated.

My understanding is that humans are genetically programmed for pattern recognition, even to the point of thinking they perceive them where none exist.
Also they apply a smattering of knowledge to complex subjects to try and make some sense of them.
Whichever, hence the heap of baseless hypothesising on this and countless other topics.

Check! Again, I didn't get to your post before writing my comments. Agree.

I feel reasonably certain the answer to the OP's question is that it is the sound of one hand clapping, or possibly a tree falling in the woods with no one there to hear it.[...] I suggest doing whatever is most convenient and to never think about it again!

Agree. The OP has probably read something, somewhere on the net, by someone who thinks they understand transformers, or think that trying different amps with different OT output types is sufficient to generalize to how winding affects tone. There are lots of those comments choking the net. I suspect that real, technical details and processes are too tedious and dull to dig through. Perhaps rightly so. I do love the section of the Atomic Rockets web site under the heading of "Respecting Science". (Atomic Rockets is a site whose reason for existing is providing factual science information for authors of science fiction to hang their stories on. Here's an excerpt, itself a quote from wikipedia.)

Ultracrepidarianism is the habit of giving opinions and advice on matters outside of one's knowledge. The term ultracrepidarian was first publicly recorded in 1819 by the essayist William Hazlitt in an open Letter to William Gifford, the editor of the Quarterly Review: "You have been well called an Ultra-Crepidarian critic." It was used again four years later in 1823, in the satire by Hazlitt's friend Leigh Hunt, Ultra-Crepidarius: a Satire on William Gifford.

The term draws from a famous comment purportedly made by Apelles, a famous Greek artist, to a shoemaker who presumed to criticise his painting. The Latin phrase "Sutor, ne ultra crepidam", as set down by Pliny and later altered by other Latin writers to "Ne ultra crepidam judicaret", can be taken to mean that a shoemaker ought not to judge beyond his own soles. That is to say, critics should only comment on things they know something about.

[dorrisant]

Well, I didn't swear by what I read, only that it seemed plausible. One could certainly test the theory by running into dummy loads for each of the output taps while monitoring the result on a scope or spectrum analyzer. Not that I have time to do so and my ears have never heard any difference.

[bepone]

several points to think about /who wants to use brain/:

- what is the damping factor on 4 to 4 ohms and what is on the 16 to 16 ohms?

- what is the frequency response on 4 to 4 and 16 to 16 ohms?

- what is the efficiency of tranformer (losses in primary+secondary) also meaning speaker volume (!), on 4 to 4 compared to 16 to 16 ohms?

is it all the same=? somebody did some calculation and measurements or real transformer? and what are the conclusions?

reading this to me looks like people idealising too much passive and lossy guitar output transformer ..

[R.G.]

- what is the damping factor on 4 to 4 ohms and what is on the 16 to 16 ohms?

Good question, but much more complicated to answer than it would seem to be.
Damping factor is the ratio of the amplifier's output impedance to the speaker's impedance. Easy as long as there is only one speaker involved; just measure both, take the ratio, and you're done. But with tube amps and multi-speaker cabinets, it gets complicated. Notice that the OT was not in that description. In a typical guitar amp, negative feedback is taken off of the speaker side of the OT. This reduces the output impedance of the whole amplifier, and the resistances of the OT windings are hidden inside the amplifier's feedback loop, lowered by the feedback factor. In an amp without feedback, the damping is whatever it is, and the equivalent resistances of the OT windings are much less than the secondary-referred impedances of the tubes driving the primary. There is not a direct way to generalize 4 to 4 ohms or 16 to 16 ohms without specifying the rest of the amplifier.
Then there is the case of multi-speaker cabs. Paralleled speakers act like a lower load, and the damping factor is the ratio of the paralleled speakers to the amplifier output impedance, with the same complications as above.
Series speakers each act like an added impedance in series with the other speaker, so the damping factor of the amp could be zero and the speakers would still lowered by being in series with each other. This is true even if the proper or improper output impedance tap is used.
This issue does not generalize down to questions of an OT setup.

- what is the frequency response on 4 to 4 and 16 to 16 ohms?

Again, not amenable to a definite answer based only on the OT. The whole amplifier, including the OT, and especially the amount of feedback have to be taken into account.

- what is the efficiency of tranformer (losses in primary+secondary) also meaning speaker volume (!), on 4 to 4 compared to 16 to 16 ohms?

If both transformers are well designed, no change in efficiency at all. Speaker volume depends on the speaker setup (individual speaker watts-to-SPL efficiency) and any series/parallel hookups. If the speaker setup is properly matched to the output impedance setting, almost no change for the speakers.
Here's why. When designing a transformer, one picks a core that experience, or charts and graphs suggests will be "big enough". One then figures out the amount of window area inside the core to put wire in, leaves out a bit of that area for the former bobbin and some spare area because wires don't perfectly fill area nor wind to perfectly even winding lengths. The remaining wire fill area (often about 85% for guitar OT type trannies) you then divide that in half and allocate one half to primary and one half to secondary. This is because you want the current density to be the same for primary and secondary to even out the power dissipation. The turns ratio has little if any to do with this.
The secondary area is then further subdivided into areas based on the power through each section. As noted earlier a 16 ohm winding has twice the turns of a 4 ohm winding. If this is wound as two identical windings, you can get exactly equal efficiency by switching the windings from series to parallel. If you take a tap for 4 and don't use the other half for 16, there is some juggling of wire gauges and winding area to make the wire current densities come out close. But in practice, OTs are done for lowest cost, so the fine points of juggling for equality are skipped. In any case, it makes very little difference once you get outside the whole amplifier circuit and feedback, as mentioned above.

is it all the same=? somebody did some calculation and measurements or real transformer? and what are the conclusions?

It's much like asking if, when a person takes multiple flights from London to Rome, will wearing red socks versus blue socks result in shorter flight times? It is certain that some flights will be shorter, some longer...