[AMRadio] Sound advice

Donald Chester k4kyv at charter.net
Thu Aug 25 13:24:13 EDT 2016

> If
> you have ever done research on mic preamps for a project like this,
> apparently the audiophile crowd that pays 60 bucks for a 12AX7 are just as
> nutty over mic preamps.  
> Charlie, W4MEC in NC

You don't have to pay that.  Some guy was selling 12AX7s at the Huntsville
hamfest for about $9 each.  I use 6F5s in my pre-amp. The 6F5, a metal octal
tube, is practically identical electrically to one section of a 12AX7, and
they have the advantage of two separate tubes that can be swapped around to
achieve better balance in a push-pull circuit.  Another otherwise identical
tube is the 6SF5, which has a different pin-out and the grid comes out at
the base instead of a grid cap on top.

Don k4kyv

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