Quality difference between output transformers

[mikeyyy]

I'm a bit of a noobie here, so please be gentle!
I've read a lot about how different components such as resistors and capacitors can effect the quality of the sound from a tube amp, but I can't find any comparisons between output transformers.

Say I'm building an amp from a schematic and I find two different output transformers of the same spec - one priced at, say, 50 quid and another at 100. Is the more expensive one better value in terms of sound quality, or would I be better off buying the cheaper one and spending the money on the other components instead?

[andyjevans]

There have been a few threads giving comparisons of output transformers. Some names you could input for a search are:
James
Lundahl
Tribute
Hammond
Electraprint
Sowter
O-netics
Tamura

[kevinkr]

Originally posted by andyjevans
There have been a few threads giving comparisons of output transformers. Some names you could input for a search are:
James
Lundahl
Tribute
Hammond
Electraprint
Sowter
O-netics
Tamura

Iso Tango
Hashimoto
Magnequest

EIFL is a good place to get this stuff as well:
http://www.eifl.co.jp/index/export/export2.htm

Being in Japan I would focus on Hashimoto, Iso Tango and Tamura. I would recommend looking at the ads in MJ (Musen-to-Jikken from Seibundo IIRC) as well for local vendors - there are also some obscure Japanese transformer vendors not well known in the West. (I'll look in some of my back copies and see if I can find them.)

[boywonder]

I also a tube newbie but here are some basic transformer parameters that are important.

Power rating (W): You may find several transformers that have equivalent primary impedance but have different power ratings. If your circuit design pushes the limit of the transformer power, the core will saturate resulting in distortion.

I have no idea if there are any advantages/disadvantages of "over spec-ing" the power rating of the transformer. I think insertion losses may go up but I don't know if there are any other downsides.

Typical 8000 ohm transformers for EL84 PP designs are available in 10W, 15W, and 20W sizes for example.

Bandwidth is also a common transformer spec. (ie 40hz-60Khz, etc). Sometimes largers transformers of the same primary impedance have flat response over a wider bandwidth, especially the bottom octave.

How the windings are actually wound is also another parameter, although my knowledge is a little thin here. Higher quality transformers tend to have lots of separate windings for the various taps, some transformers have several taps on a single winding.

Then there are cores, EI core, toroidal, C cores etc.

Quality of the OT definately has an impact on sound quality.

Other output transformer brands not previously listed are Magnaquest, Tango, Hashimoto

Morgan Jones' book "valve amplifiers" has lots of transformer info; and there is lots of info on this forum.

[Bandersnatch]

Originally posted by mikeyyy
I'm a bit of a noobie here, so please be gentle!
I've read a lot about how different components such as resistors and capacitors can effect the quality of the sound from a tube amp, but I can't find any comparisons between output transformers.

Say I'm building an amp from a schematic and I find two different output transformers of the same spec - one priced at, say, 50 quid and another at 100. Is the more expensive one better value in terms of sound quality, or would I be better off buying the cheaper one and spending the money on the other components instead?

I'd go one step further with the worries. I've been quoted price varying more than 3:1 for the same vintage design. The expensive one claimed to be hand wound, the other from a NC winding machine. Care to guess which one I got... And the NC shop can do mods if I request.
cheers,
Douglas

That shop is Heyboer TX in Grand Haven MI.

[sorenj07]

This isn't a thread about brands but Edcor deserves to be up there along with the others. They've measured better than Hammonds in many cases.

[Richard Ellis]

Two more for ya.
One-Electron, a conventional EI type
Plitron, A hyper expensive toroidal
____________________________________________Rick.. ......