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Author Topic: Question about 5881s  (Read 7063 times)
pine
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« on: April 23, 2009, 05:46:05 PM »
Everything I read about 5881s states a maximum plate voltage of 400V or less, well below that which is found in the OTS, yet several people are using this tube, it seems. Do I need to mod the amp to use these tubes?
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bluesfendermanblues
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« Reply #1 on: April 23, 2009, 05:48:33 PM »
I use Sowtek 5881 WT with no problems. 5881 used to be the stable of old fender tweed amps running at 400-460 VDC. ...
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pine
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« Reply #2 on: April 23, 2009, 06:05:25 PM »
I was reading about them on a tube dealers website and they have said that

 "There are some important things to know about the reissue Tungsol 5881 tube before you decide to use it. The Tungsol 5881 is a 23 watt tube and is rated for a maximum plate voltage of 400Vdc. The many amplifiers that have higher plate voltage but use a tube rectifier can use the Tungsol 5881 tubes without issue. A prime example is the ’59 Bassman LTD. However it is also critical to rebias the amp heeding the 5881’s 23W rating. This will provide a vintage tone and less clean headroom. Leaving the bias set to a 6L6GC setting and/or using the Tungsol 5881 in a high voltage amp with a solid-state rectifier, will likely cause problems and are not covered by warranty."

I'm not adverse to pushing the limits a little bit, I just wanted to check and see if anyone HAS had a problem from the high plate voltage/solid state rectifier issue.
« Last Edit: April 23, 2009, 06:08:14 PM by pine » Logged
JD0x0
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« Reply #3 on: April 24, 2009, 12:16:22 AM »
i swapped the JJ 6L6GC's for tungsol 5881's and DID NOT BIAS my amp is still at the original 37mA i believe and it runs fine
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JohnE
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« Reply #4 on: April 25, 2009, 08:24:52 PM »
I am running Tung Sol 5881's. When I put them in the bias changed from 32mA with the Tung Sol 6L6s that Nik provided to 35-36mA. I left it that way and it sounds pretty good. A slight improvement (kind of smoothed things a bit)  over the 6L6's.
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wyatt
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« Reply #5 on: April 25, 2009, 11:26:10 PM »
Quote from: bluesfendermanblues on April 23, 2009, 05:48:33 PM
I use Sowtek 5881 WT with no problems. 5881 used to be the stable of old fender tweed amps running at 400-460 VDC. ...

Back when Fender used 5881's, in the '50's, their typical B+ voltage was around 350-390VDC.  By the Blonde era, when Leo started to crank up the plate voltages for more headroom, he had switched to a 30-watt tube...the RCA 6L6GC.

An original Tung Sol had a maximum plate voltage of 400VDC...I wouldn't exceed 425VDC for a real 5881 or 6L6GB .  The RI's?  I dunno, they aren't the same tube..never will be.  But they are cheap, so as long as the amp was built robust enough, who knows? 

The Sovtek 5881 isn't a 5881 at all.  It's a Soviet Air Force tube that performed similar to a  5881, it's not build the same as an original 5881, it doesn't sound the same as an original 5881 - on paper the only source I can find says it has a max plate voltage of 483VDC.
« Last Edit: April 25, 2009, 11:38:14 PM by wyatt » Logged
wyatt
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« Reply #6 on: April 25, 2009, 11:33:31 PM »
Quote from: JohnE on April 25, 2009, 08:24:52 PM
I am running Tung Sol 5881's. When I put them in the bias changed from 32mA with the Tung Sol 6L6s that Nik provided to 35-36mA. I left it that way and it sounds pretty good. A slight improvement (kind of smoothed things a bit)  over the 6L6's.

That would be around 60% dissipation...which is what Nik seems to be setting the GC's at.  37mA is around 70%, which shouldn't kill a tube either.  So, really it all comes down to the maximum plate voltage. 

It should be important to note most modern 6L6GC's are only 25-watt tubes anyway...all the Russian tubes.  I believe on the Shugunag and JJ are 30-watt tubes.
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JD0x0
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« Reply #7 on: February 18, 2010, 06:23:00 PM »
Quote from: ToneQuest on February 18, 2010, 04:20:04 PM
Apologies for reviving an old thread but this is exactly my question, so I thought there's no point starting a new thread.

I have a couple of Tung Sol 5881 RIs lying around with me and for a while I've been toying with the idea of trying them out in my 50 watt S&M Special.
I read all about the max. plate voltage issue and yet some of you use Tung Sol 5881s apparently without problems. I'd love to hear more opinions, please.

Furthermore: What tonal differences are there with the 5881 tubes? At what value would you rebias the amp the the 5881s? And what bias value would you recommend for the stock JJ 6L6s?


Like i said i've used them without rebaising and they run fine. Since im pushing these very hard i lost a small amount of clean headroom but the sound was tighter and added a bit of smooth compression. At higher volumes they added a small amount of "grain" which you may or may not like. For low volume playing i like the 6L6's better but after a certain point they sound too loose and the bass is too flabby for me.
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