If they glow, this is the place to be
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Posts: 137
Joined: Thu Jul 08, 2010 11:29 am
Location: South Tankerton.


Post by ACPEN »

I wonder if anyone has pressed these early 4v triodes into use - at first sight a use for them might seem hard to imagine. They were intended as drivers for electrostatically scanned 405 line tv receivers before electromagnetic scanning became the norm. I've had a couple for some years but have only just found a use for them .
I've built several se amps using early Mazda's - currently using trioded pentodes as O.P's, not hard to drive with ML4's etc but looking for a use for the AC/P4 found them to be a better alternative having a higher mu of 20 compared to 12 for the ML4.
Their ra is very similar at 2.8k with a gm of 7 makes them.useful driving a Hammond 150H choke (the 8mA one).
The AC/P4 is happy to run at around 5mA so matches well.
If you're into early Mazda's give them a try, sonically a treat!
This amp uses a non Mazda first stage, a US type 01a - the combination of 01a, AC/P4 and AC4/PEN provides a good balance of overall gain and sonic ability. I did try the MH4 inplace of ML4 but at 40, mu is too high ( for me!)
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