OT Laminations - does thickness really matter?

[Gregg]

Hi,

For an OT usually 0.35mm laminations are recommended. maybe for HiFi it's important but I'm not convinced it so critical for a guitar amp.
Could someone please explain what's behind this 0.35mm recommendation and how it would affect the sound /if at all/ if 0.5mm laminations are used?

Thanks in advance.

[R.G.]

Hi,

For an OT usually 0.35mm laminations are recommended. maybe for HiFi it's important but I'm not convinced it so critical for a guitar amp.
Could someone please explain what's behind this 0.35mm recommendation and how it would affect the sound /if at all/ if 0.5mm laminations are used?

Thanks in advance.

It is not as crucial for a guitar OT as it is for a hifi OT. There is much less treble in a guitar's output than in a hifi setup.

Lamination thinness affects eddy current losses and treble linearity. The thinner the lamination, the less eddy current loss, and the less such losses and other eddy current processes can affect linearity.

Besides, guitar equipment is NOT hifi equipment. Make one both ways. Shoot, make one with thicker lams and see if you like the change. It's really a matter of taste. There's no one "goodness ruler".

[Gregg]

Thanks for the answer. I guess I'll have to do som A/B tests when I find myself with a lot of free time and when I get some 0.35mm laminations.
What about some current production guitar amp OTs? What do they use?

[Steve Conner]

I built one amp around a PT and OT set that came from an old 50 watt PA amp. The OT had very thin laminations, that looked about half the thickness of the PT.

A while later I got hold of another 50 watt amp where they obviously made the PT and OT out of the same laminations to save money. The OT just has a smaller stack height. (I think that's how most guitar and bass OTs are done.) I'd have expected the iron losses to suck treble, but this amp actually seems to have a better high end.