Transformer Question

[TunaFish]

Hi all expert,

I know most of the transformer used in tube amp is EI type.

But what is the benefit of EI type transformer compare to circular transformer?

I know some tube amp using circular transformer in the Power Transformer and Output Transformer as well.

Does the Circular type Output Transformer performance much worst than EI type? Is that still within "Acceptable" limit?

Thank you for your help.

Tuna Fish

[fdegrove]

Hi,

Does the Circular type Output Transformer performance much worst than EI type? Is that still within "Acceptable" limit?

Provided the toroidal OPT is well designed I don't see any reason why it would be worse than a comparable EI design.

A company that's well known for its excellent toroidal OPTs is Plitron, these designs are based on the work of Dutch engineer Menno van der Veen.

Cheers,

[ray_moth]

The toroidal ('circular') transformer is very efficient, which means you get better performance in a smaller and lighter package then would be the case with an equivalent E-I transformer. Provided that it's evenly wound, the toroid also gives off much less stray magnetic field that could interfere with nearby components. I like them, especailly as power transformers.

The toroid has two main disadvantages compared to the E-I design, namely:

1. It's more difficult to make than an E-I, therefore more expensive.

2. The core is very susceptible to DC and easily becomes saturated, ruining its performance. This means that the two halves of push-pull amplifier must be very well balanced when using a toroidal OP transformer.

Regards, Ray

[TunaFish]

In such a case, why most of the tube amp is still using EI transformer?

[promitheus]

I think the main reason is that Toroids are very hard to make when comparing them to EI transformers. EI transformers you can make them with hand achieving this way alot better quality. You can´t do that with a toroid.

What is a lot better than EI transformers and can be hand made are C-Core Transfomers. I have heard Tube amlifiers with C-Core and I can say I was very impressed.

[HDTVman]

Cost. EI is much less lower cost to make.

[promitheus]

EI cost a lot less than a toroid to make. Even hand made will cost cheaper.

[fdegrove]

Hi,

I like them, especailly as power transformers.

Funny you'd say that, I don't like toroids as powerxformers at all.

They have way too much bandwidth, letting all the crud from the mains through, they buzz like yellowjackets in the wind when they see some DC component at the input and, last but don't least, they often sound much slower than a good EI cored one.

Mind you, a good EI xformer isn't, or let me say, shouldn't be cheap, should come with a static shield between primary and secondary and should be well overrated.

Cheers,

[TunaFish]

But why even Jadis is still using EI transformer?

I know some cheap tube DIY set from China is using 3 toroidal transformers......

[ray_moth]

I know toroids don't like DC (who does?!! ) and they certainly pass on noise very efficiently from the mains supply. However, if that's a big problem, you could neutralize and condition the power by using a nice big 1:1 EI-core isolation Xformer with a capacitor (say 0.01uF, 1000v AC) across its secondary. While you're at it, why not just buy a stabilizer and fix the supply voltage as well? Conditioning the supply can be an advantage whatever type of power tranny you use.