Sowter 1010 vs 1290

Hi all,

Anyone with experience know the sonic difference between the two, if any? I know that the 1010 is larger and has more nickel whereas the 1290 is slightly smaller and has more M6 Grain Oriented Silicon Iron.

Thanks.

Andrew

Hi do you have any feedback in the last years? I'm buying some parts for an LA-2A and have the same question.
I think the 1010 should be better - but this is just a feeling... unfortunately...

In most transformers, the distortion starts to rise below 100Hz. Steel can take more flux density than nickel so it distorts less at low frequencies. Above 100Hz, Nickel distorts less than steel. As in most engineering it is a trade off between cost, size and performance.

Cheers

Ian

I have no experience with either of the Sowters.

The output transformer in the LA-2a (A24) was/is no great performer in the headroom bedroom department when driven single ended. It isn't a particularly big coil.
A possible clue as to the logic behind why it was initially chosen for the LA-2a might be that the unit is a compressor.


I remember an AES show many years ago where Eva Manley was giggling over the the advertising sheet for an LA-2a type clone from a well known (at the time) manufacturer - one of the "features" listed on sheet for it was "Compressor with HUGE Dynamic Range"

They meant HUGE dynamic range going in - not coming out

mjrippe said:

They meant HUGE dynamic range going in - not coming out

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Yep. Sorry. Folks should just ignore some of the garbage I write

No excuse for a man of my age to still be finding "Compressor with HUGE Dynamic Range' funny enough to post on here! Childish really.
Sorry to Andrew, the OP.

ruffrecords said:

In most transformers, the distortion starts to rise below 100Hz. Steel can take more flux density than nickel so it distorts less at low frequencies. Above 100Hz, Nickel distorts less than steel. As in most engineering it is a trade off between cost, size and performance.

Cheers

Ian

Click to expand...

All transformers, regardless of core material, create distortion as a function of both frequency and signal level. For any given input voltage, the strength of the magnetic field in the core increases linearly (6 dB/octave) as frequency goes down. This makes handling large, low-frequency signals a worst-case. At any given input frequency, distortion is a not-so-linear function of signal amplitude. Although "steel" (generally refers to M6 or steel with 6% silicon) can handle higher field strengths without magnetically "saturating" (distortion), it also has something called "hysteresis" distortion at low signal levels - which gets worse as signals get smaller. Although nickel alloys (commonly 50% or 80% nickel will handle a few dB less signal when saturation begins, it can have vanishingly small hysteresis distortion at low signal levels. The hysteresis distortion is highly dependent on the heat treatment of the core material (Jensen has a carefully guarded method that makes low-level distortion essentially unmeasurable). Unfortunately, nickel is much more expensive than steel, so cheap transformers usually have steel cores and most have cores that are too small to support truly low frequencies at low distortion. When I owned Jensen, and published highly-detailed data sheets, we always specified level-handling at 20 Hz. Our competitors would make their "level-handling" measurements at 30 Hz or even 50 Hz - which, for those who don't understand the distortion characteristics, made their products look like a real bargain. If you compare apples to apples, the Jensen will look better and better. If you want to dig deeper, the "Audio Transformers" chapter I wrote for Ballou's "Handbook for Sound Engineers" is available for free download at https://www.jensen-transformers.com/wp-content/uploads/2014/08/Audio-Transformers-Chapter.pdf. As you said, audio transformer design is driven by a very complex set of interactions and tradeoffs!

thanks for that Bill

MisterCMRR said:

Although nickel alloys (commonly 50% or 80% nickel will handle a few dB less signal when saturation begins, it can have vanishingly small hysteresis distortion at low signal levels.

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Assuming sane signal levels, your signal spends most of its time quite a bit below magnetic saturation. I always found that Hi-Nickel output transformers just plain sound better, and the extra cost was worth the price of admission. Good ones are still OK for +24dBu before saturation anyway so I never felt there was any real harm done there.

I suppose a lot on here are looking for colour from their transformers, in which case M6 or 50% Nickel (or 'pinstripe') is probably a decent and less expensive option.