Bottlehead Forum

General Category => General Discussion => Topic started by: hron61 on February 21, 2025, 04:56:47 PM

Title: Can a 12au7 and 12au7a be used at the same time?
Post by: hron61 on February 21, 2025, 04:56:47 PM

Silly question i know.
I have a foreplay ll and am wondering if a 12au7 and a 12au7a tube can be used at the same time together.
I usually use either 12au7 or 12au7a but have never mixed them. Curious as to what the implications (good or bad) might be.

Title: Re: Can a 12au7 and 12au7a be used at the same time?
Post by: Paul Birkeland on February 21, 2025, 05:12:59 PM

There are no issues with doing this in anything we have made that uses the 12AU7.  The "A" just denotes a controlled heater warm up time that is helpful when you have heaters wired in series, and this just doesn't have any impact on any of our circuits. 

Title: Re: Can a 12au7 and 12au7a be used at the same time?
Post by: hron61 on February 21, 2025, 07:03:49 PM

Thanks Paul, much appreciated.