Just out of interest.. How much does this change?

[VTypeV4]

I was wondering how much the frequency response of a valve amplifiers' output transformer changes with respect to output level?

Looking at typical specs, most output transformers are referenced at low level, usually one watt (not unlike speakers) but i was wondering how much these deviate by the time they're at rated power / half power or whatever. I assume high quality transformers maintain their low level characteristics as the power rises better than cheaper / lower spec units? For example, I expect my Leak output units to be a smoother response curve than the one in the Linear L30..

I appreciate that difference in designs, Class A, Class A/B, Single ended, Push-pull, Ultra-Linear etc designs will also dictate the overall response and of-course coupling of the appropriate load on the secondary etc. My question is aimed at the output transformer itself assuming all other parts to be an 'ideal world scenario' including any distortion whithin the amp, not the coupling device..

Many thanks, Matt

[longtimefred]

U got nothing better to think about youth?

[VTypeV4]

Nope, not at the time..

I always find it fascinating how much each component contributes to a particular sound, you know how it is man, I can't help it!

[umph]

basically the output transformer is a bottleneck and how much it limits the response depends on how it's wound. They're normally pretty linear up to the rated wattage in my experience

[VTypeV4]

Cheers Umph,

You say 'how it's wound' can you expand a bit more on that? For example, guage of wire, distance between windings, thickness of insulator, density of iron core?

[Mr. Foxen]

Composition of the core is one thing. Laminated or C core has an effect. The actual pattern the wire is wound in has some effect, the famous Partridge transformers have some sort of woven looking thing going on.

[VTypeV4]

Cheers Man.

[umph]

[quote name='VTypeV4' timestamp='1362967118' post='2006921']
Cheers Umph,

You say 'how it's wound' can you expand a bit more on that? For example, guage of wire, distance between windings, thickness of insulator, density of iron core?
[/quote]

with guage of wire the thicker it is the better the current handling and thus, low end and power, but obviously you can't get as many turns on so it means bigger transformers. Thickness of insulation is just there to stop interaction between windings and shorts. The quality of the iron used tends to also effect the frequency response mainly in the top end. It's why they use the lower grade in the svt to get rid of the top end to get the svt sound.

To go on from what mr foxen was saying, also the way you wind it has an effect on the performance, putting on winding after another often leads to quite big imbalances etc. So its good to interleave the windings to get them more equal.

Alot more thought goes into designing a good transformer than you think

[Mr. Foxen]

[quote name='umph' timestamp='1363037446' post='2007514']
It's why they use the lower grade in the svt to get rid of the top end to get the svt sound.
[/quote]

Fairly sure the because part is down to being cheaper.

[VTypeV4]

I remember reading something about windings on secondaries causing a head ache for designers for use at 8 ohm due to a potential imbalance.?

I think it was something to do with two sets of windings in parallel driving current into one another potentially causing output losses and errors?

.

[Mr. Foxen]

Headache for amp designers if the transformer designer didn't know what they were up to maybe. Sort of goes along with any other cheaping out on components.

[VTypeV4]

Cool..

It's difficult to say whether I can hear any differences when operating different loads on any of my amps as any difference can likely be attributed to the change of speakers. Plus I expect the freq range of the amp to be greater than that of any speakers I have at home..