Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jerrydyer on July 02, 2011, 03:45:35 pm

Title: 5881 and plate voltage
Post by: jerrydyer on July 02, 2011, 03:45:35 pm

Im running these guys in a 50 watt. around 398  sounds great. My 100 watters use a magnetics corp PT and I like to use the extra windings. it averages 520..Im thinking these guys aint gunna cut it. too bad.. i like the tone..... can they really be pushed or should i use a different tube?
tanx 

Title: Re: 5881 and plate voltage
Post by: jjasilli on July 02, 2011, 04:12:37 pm

True old fashion 5881 max out @ 400V.  Many new production are re-labeled 6L6GC, which max out @ 500V.  Either way you're over voltage, but probably OK.  Otherwise, use EL34, KT88 or 6550; or drop the voltage a bit: power resistor; reverse zener; bucking tranny.

Title: Re: 5881 and plate voltage
Post by: tubeswell on July 02, 2011, 06:08:52 pm

If they sound good already they probably won't sound much better at higher voltages.  As jjasilli pointed out, it depends on the '5881' you have, and you really need to work out what type of '5881' it is.

If its a re-branded Sovtek, or a Russian 6P3Se (with the wafer thin black base), these are nominally 20W tubes, but  will handle more. If its a 6P3S (without the 'e'), or a Chinese '6L6G', then don't run it above 400 and don't run it above 20W.

http://timelesson.blogspot.com/2010/02/6p3-beam-power-tetrode.html (http://timelesson.blogspot.com/2010/02/6p3-beam-power-tetrode.html)

More detail on the 6P3S and 6P3Se

http://www.rutubes.com/index.php?productID=176 (http://www.rutubes.com/index.php?productID=176)

http://www.rutubes.com/index.php?productID=177 (http://www.rutubes.com/index.php?productID=177)

Title: Re: 5881 and plate voltage
Post by: mac0611 on July 13, 2011, 12:03:37 pm

I consider a true old fashioned 5881 to be a tung-sol which easily can survive a 500vdc environment. 6G6 bassmans ran at this level all day long.

Title: Re: 5881 and plate voltage
Post by: HotBluePlates on July 13, 2011, 04:53:40 pm

Yeah, you really have to qualify you're statement with what exactly you mean by "5881."

For most folks, that means various new production tubes, which can vary somewhat in capability. I tend to think 50-60's Tung Sol 5881's (and some of the relabels by RCA, etc), just because I have a small handful of them.

I'd bet the older versions are more robust (at least more than the data sheet claims, just cause they had to be guaranteed to meet/exceed spec), but I'd still tend to use them in situations where they weren't pushed. That's just because it's not as easy to get ahold of more.