Airgap experiments

Discussions and experiences with user adjustable gaps.
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Thermio
Posts: 6
Joined: Mon Jun 27, 2011 4:24 am

Airgap experiments

Post by Thermio »

Hi Guys,

I am building some single stage, differential amps with a bit of a twist in that they use plate chokes. I originally routed these directly to the plates and then tried them through the OPT and the latter had a smoother midrange and more "natural" sound. The inductance of the OPT is unknown as they were made for a parafeed.

I have now tried butt gapping them from 1x1 and the sound moved further along the above lines so I am onto post it notes next... I should point out that there was some trade off in grip and slam here although they have retained most of what they had in that department.
Thermio
Posts: 6
Joined: Mon Jun 27, 2011 4:24 am

Onward

Post by Thermio »

So, if a butt gap is equivalent to 0.0005 inch (variables noted) then try more. The little, shop down stairs in the grocery store that sells school supplies did not have 3M Post It notes (Dave's field repair aid for calibration) so onto water colouring paper. Best I can tell with an analogue calliper: about .25mm or a little under .01".

In order to get some western style, discernible results .02" was the first try. Whoa, OK, now I get it. Greater air and space as well as that compelling thing that happens in the midrange with SE amps. It is a signature sound. Smoother and much more emotionally engaging, grossly preferable (IMHO) at first blush as well as extended listening. A little more grip and slam was lost but there is still more than enough to go around, they are still single stage, differential amps and remember that inductance is being provided by plate chokes. A compelling compromise.
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