Anyone tried using a 5U4 instead of the 5AR4 for the SE9

ninja2586 · « **on:** 23 Aug 2003, 06:21 pm »

I've heard some really good things about the 5u4 in the ST70 as a replacement for the 5AR4. But that tube draws about an amp more from the power transformer.

I was wondering if the SE9's power transformer can handle the extra load from the 5U4. Anyone tried this sub??

albee · « **Reply #1 on:** 26 Aug 2003, 02:42 am »

Don't be brave enough to be the first to try it!

Those two tubes are usually aren't interchangeable in any rig. See if Mike can find out for you first.

ninja2586 · « **Reply #2 on:** 1 Sep 2003, 04:52 pm »

Quote from: albee

Don't be brave enough to be the first to try it!

Those two tubes are usually aren't interchangeable in any rig. See if Mike can find out for you first.

Yeah, that's my first thought. I emailed Mike Barnes and he referred me to Yuths in his office. Yuth finally got hold of the manufacturer and told me that we can use the 5U4 w/o modifications. This is good as I'm told that the 5U4 can produce better sound than the 5AR4/GZ34 can ... at least in this one application of a modified ST70.

Besides, the 5U4 NOS seems to be MUCH cheaper than the 5AR4/GZ34 tubes as well. I've got one on order and will give it a try. Anyone else??

JohnR · « **Reply #3 on:** 1 Sep 2003, 11:31 pm »

5U4 is directly heated and the amp will start up faster than a 5AR4.

FWIW....

ninja2586 · « **Reply #4 on:** 1 Sep 2003, 11:41 pm »

Quote from: JohnR

5U4 is directly heated and the amp will start up faster than a 5AR4.

FWIW....

If I were to use it, what's your recommendation as for the startup issue?? Wait a couple of extra seconds before turning up the volume??

JohnR · « **Reply #5 on:** 1 Sep 2003, 11:58 pm »

Don't really have a recommendation...

yeldarb · « **Reply #6 on:** 14 Apr 2005, 02:53 pm »

ok, those of you that have tried this tube instead of the standard, what were the results?

AudiophileBob · « **Reply #7 on:** 16 Apr 2005, 02:54 am »

The 5U4 uses nearly 1.5 amps more heater current.
This will result in more watts of extra heat and minimal sonic difference.
IMHO, I wouldn't stress my filament transformer for the doubtful gain.
The rectifier's output is filtered before it is used anyhow.

crossroadazn · « **Reply #8 on:** 20 May 2005, 04:44 pm »

I wouldnot put 5U4 in ST-70 because of higher curent and heat it will shorten the life of other tubes. I got this problem in one of my ST-70s.