Does output transformer make a difference?

[Alan0354]

I just installed a Magnetic Components output transformer, it is supposed to be cheap. Does it make a difference in sound quality compare to the expensive ones that is over double the price? Or is it just snake oil?

[Austin]

It depends on the rating of it, there is a max dc milliamps before it saturates and a frequency range from lowest hertz to highest hertz in addition to the power rating. Is it single ended air gapped type or center tapped primary for balanced push pull type? The more milliamps ran through the primary is going to decrease the frequency response of any output transformer.

In short the specs are going to be what you pay for.

[Alan0354]

Thanks for the reply. I am compare the similar type transformer. Say, there are quite a few manufacturers that make the 40W 4K to 4,8,16ohm, about the same size push pull transformer. This is quite a common transformer for Fender Vibrolux, Pro Reverb and Bandmaster. This is quite different from say Bassman or Super Reverb where the size is bigger.

What is the reason the more DC current through the Tx, the frequency response decrease? I thought core saturation will cause compression.

[imaradiostar]

Yes it makes a difference. I wouldn't say it's price that makes the difference though.

As an example, Mercury Magnetics makes excellent products, but I feel they are priced in excess of their performance.

I would take Magnetic Components Inc or Heyboer any day and they're a good bit cheaper than Mercury. My main amp has a MCI transformer and I love it!

JT

[Austin]

Thanks for the reply. I am compare the similar type transformer. Say, there are quite a few manufacturers that make the 40W 4K to 4,8,16ohm, about the same size push pull transformer. This is quite a common transformer for Fender Vibrolux, Pro Reverb and Bandmaster. This is quite different from say Bassman or Super Reverb where the size is bigger.

What is the reason the more DC current through the Tx, the frequency response decrease? I thought core saturation will cause compression.

Somebody who knows more than I will surely chime in but DC current reduces the low frequency response of the transformer... I am just learning. The inductance in the primary gets used up by the standing dc current and that affects the way it can transfer the electro-magnetic energy to the secondary. Again, somebody else can explain it better than I..

[Alan0354]

Thanks.

Anyone ever open an output transformer. How do they wind the primary wires? Are they wound smooth from first end to the second end, put a piece of paper on top and then wind back from the second end back to the first end. Or is the primary scattered wound or some special pattern? How about the secondary winding?

The reason I ask is because if they wind from one end to the other and then back, there should be minimal difference between different brands as long as the other parameters are the same. I am back to the 40W Vibrolux transformers that all brand pretty much have the same size transformer so it is fare to A B comparison.

[Enzo]

The other parameters are not the same though. The iron formulations differ. The lamination dimensions differ. The winding form size can be different. The wire size differs. Some transformers have dual wires wound, then they connect one end of each together for a center tap, so both sides of the winding are hte same length wire. others wind half the turns, splice on a center tap wire, then complete the winding. The outer layer has the same number of turns, but the wire is much longter,so higher DC resistance. The transformer runs on turns ratios, not resistance, but it still affects the system.

[Alan0354]

Somebody who knows more than I will surely chime in but DC current reduces the low frequency response of the transformer... I am just learning. The inductance in the primary gets used up by the standing dc current and that affects the way it can transfer the electro-magnetic energy to the secondary. Again, somebody else can explain it better than I..

That's what I was thinking that the DC current eat up the core saturation headroom so if you further increase the current ( in one direction) the core get into saturation sooner and the effect of the core disappear. But does that has anything to do with frequency response?

[Alan0354]

The other parameters are not the same though. The iron formulations differ. The lamination dimensions differ. The winding form size can be different. The wire size differs. Some transformers have dual wires wound, then they connect one end of each together for a center tap, so both sides of the winding are hte same length wire. others wind half the turns, splice on a center tap wire, then complete the winding. The outer layer has the same number of turns, but the wire is much longter,so higher DC resistance. The transformer runs on turns ratios, not resistance, but it still affects the system.

I measured the resistance of the 40W transformer, it was quite low, I forgot, I think it's below 100ohm. So in the big picture of say 4K primary, that only cause slight imbalance. I just posted on the other thread, what is the winding pattern of OT, are they just simple layers winding from one side to the other and back, or are they scattered winding. If they are all uniform winding from one side to the other and back, there is very little room to play with to change the characteristics.

What can they do to the metal core that can make a difference in the quality?

[J M Fahey]

Core: different alloys, heat treatment, lamination thickness.
Great variation in quality and price.
Winding: cheapest and worst: scattered winding. Acceptable in a cheap wall wart, unacceptable in an amplifier.
Cheap: all primary wound at once, then all secondary at once (what you mentioned)
Better: split and interleave windings.
Different levels of complexity:
a) half primary/single secondary/half primary. (cheaper Fender)
b) much better: 1/4P - 4 ohm winding - 1/4P - 4 to 8 - 1/4P - 8 to 16 - 1/4P (old English amps)
c) primary split in, say, 8 windings; secondary split in 7 or 8 , *all* interlaced (P-S-P-S .... P-S) and all coils exit individually to a complex tag board. Windings can be connected in series/parallel in various combinations.
*Very* expensive, overkill in Guitar amps, used in Hi end HI FI stuff.

[Alan0354]

Core: different alloys, heat treatment, lamination thickness.
Great variation in quality and price.
Winding: cheapest and worst: scattered winding. Acceptable in a cheap wall wart, unacceptable in an amplifier.
Cheap: all primary wound at once, then all secondary at once (what you mentioned)
Better: split and interleave windings.
Different levels of complexity:
a) half primary/single secondary/half primary. (cheaper Fender)
b) much better: 1/4P - 4 ohm winding - 1/4P - 4 to 8 - 1/4P - 8 to 16 - 1/4P (old English amps)
c) primary split in, say, 8 windings; secondary split in 7 or 8 , *all* interlaced (P-S-P-S .... P-S) and all coils exit individually to a complex tag board. Windings can be connected in series/parallel in various combinations.
*Very* expensive, overkill in Guitar amps, used in Hi end HI FI stuff.

Like you said, all the technique you mentioned are for lowering capacitance and better coupling. I can see these are very valid for audiophile that you want response from below 20Hz to 20KHz, not a guitar amp which mainly is from 50Hz to 10KHz max out. In fact, guitar speak hardly respond to anything over 5KHz. So with this limitation, does it really matter how the coil is wound?

[Austin]

Like you said, all the technique you mentioned are for lowering capacitance and better coupling. I can see these are very valid for audiophile that you want response from below 20Hz to 20KHz, not a guitar amp which mainly is from 50Hz to 10KHz max out. In fact, guitar speak hardly respond to anything over 5KHz. So with this limitation, does it really matter how the coil is wound?

Hehe it depends on who you ask, some people on youtube I have seen have made good sounding home brew guitar amps using wall wart power transformers as output tranformers with good results. Those malibu low voltage lighting transformers are 10:1 ratio and air gapped and could make a output transformer for a single ended guitar amp. I hope to try it in the next few weeks myself.

[Enzo]

Whether it matters or not is one thing, depends on if it affects something you care about. Whether two different transformers are the same is a separate issue. Differences are more than simple freq response. Saturation can be an important issue for example.

[Enzo]

Hehe it depends on who you ask, some people on youtube I have seen have made good sounding home brew guitar amps using wall wart power transformers

Sure, and there are people who poke a bunch of pencil holes in their speaker cones, because they like the sound. But now we are getting over into off the wall stuff rather than good effective design practice. SOmeone may LIKE the non-linearities of a "poorly" wound transformer, or they may like the gritty sound of a little tranny that really isn't up to the job. But that doeswn't mean it is solid practice.

[Alan0354]

Sure, and there are people who poke a bunch of pencil holes in their speaker cones, because they like the sound. But now we are getting over into off the wall stuff rather than good effective design practice. SOmeone may LIKE the non-linearities of a "poorly" wound transformer, or they may like the gritty sound of a little tranny that really isn't up to the job. But that doeswn't mean it is solid practice.

Let me put some limit in the comparison as you can have the best vs the mickey mouse stuff. Let say I am comparing the 40W transformer from Magnetic Component that is only $43 to the more expensive brand that cost over double. That's would be a more realistic comparison.