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Old 29th November 2006, 06:14 AM   #1
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Default Tung-Sol (new production) 6550s

Hello everybody

I am looking to get some new power tubes to take advantage of my power supply headroom. I am currently running el34s in triode mode, and would love to upgrade to a pair of new production Tung-Sol 6550s. so I want to know how hard these tubes can be ridden. Tung-sol doesn't have a datasheet for their new production (if someone has found it please show me!) and I want to see what everyone thinks.


Thanks a bunch
Moose
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Old 29th November 2006, 01:20 PM   #2
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The new production "Tung Sol" 6550's are made in the Russian Reflector factory along with Sovtek, Electro Harmonix, the new Svetlana and others. I recently bought a large quantity of "previously auditioned" Russian tubes, cheap ($10 each). Included in this lot were a pair of the "Tung Sol" 6550's, and several other power pentodes. The "Tung Sol" 6550's looked exactly like the Sovtek KT88.

I stuffed each tube into my SimpleSE amp and tested them at the nominal rated power dissipation level, and in my usual style, I cranked each tube up until the glow of death showed, and then backed up a little. I did not make any measurements, just listening and meltdown testing. Each pair of tubes got at least an hour of operation at the "just below glow" level with multiple music sources.

The "Tung Sol" 6550's and the Sovtek KT88 biased up similar, and tested the same. These tubes sounded good, and one pair of each type ran for an hour each at 33 watts dissipation. A pale glow appeared at the 35 watt level.

I tried several other tube types, but the ones that got my attention were the Electro Harmonix KT88EH and the Electro Harmonix 6550EH. These appear to be the same tube, and I have one of each in my amp currently. These have extra heat radiating fins welded to the plates which allow these tubes to handle more power than a conventional KT88. These tubes will dissipate 45 watts before any hint of glow appears. I have been running 2 at this level (despite protests from the power transformer) for about 3 weeks. No issues yet. These have the best bass and make the most power of any tube tested.

Also worth noting were the Sovtek 6L6WXT's and Electro Harmonix 6L6GC tubes.

See the following thread for the testing details:

Sovtek 5Y3 Issues

See the last post in this thread for a picture of the 6550EH's cranked to 11:

Why are Hammond SE OPTs dissed? Heavier than the competition...
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Old 29th November 2006, 01:31 PM   #3
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to top is off, the Electro-Harmonixs are far cheaper!

How much power have you squeezed out of these kt88s in Triode mode?

those pictures of it glowing pretty much sold me, those are amazing, my power transformer has the current to do it to.

Thanks a bunch

-Moose
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Old 29th November 2006, 05:02 PM   #4
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I have not measured power yet. I have been out of town for 6 out of the last 7 weekends, and chained to my computer at work. My newest amp (another SimpleSE) hasn't been turned on in almost 2 weeks

The transformer in my older amp (which hasn't been on either) is only rated for 150 mA. I have had the KT88's running at 110 mA each + 20 mA for the drivers. The poor power transformer really doesn't like this!

I am already contemplating a replacement in the new amp. I have a BIG toroid and Antique Electronics has some scratch and dent 400-0-400 volt 465 mA Hammonds on sale........ Decisions, decisions, decisions.
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Old 30th November 2006, 06:28 PM   #5
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There are physical differences between TS 6550 and Sovtek KT88 tubes.

The new Tungsol 6550 has only one support post per side, 3 getters, and thicker glass (it weighs more and thuds when tapped).

The Sovtek Kt88 definitely has the same plate but has two supports per side, one getter, and thinner glass.
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Old 30th November 2006, 06:47 PM   #6
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Default Re: Tung-Sol (new production) 6550s

Quote:
Originally posted by alexmoose
Hello everybody

I am looking to get some new power tubes to take advantage of my power supply headroom.
Moose
Whats the B+ you intend to push'em to ?

In my150W amp I'm pushing new Svet KT88's at 530V poked at 70mA each and things are beginning to go slight sweaty orange. Suprise suprise thinking on the fly I decided to put in a set of original NOS EL34's and with same conditions they didn't glow one bit and they gave the same power o/p. One takes what one gets. The later ones -no way.
I wouldn't go over 450V for the 6550 whatever version. There are so many clones about. In my other amp which runs class A at 265V these sound better in UL at lower voltages with even higher currents at 100mA each. I get the impression that the 6550B/C behave with somewhat lower internal impedance than the KT88. o.m.o


richj
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Old 30th November 2006, 09:48 PM   #7
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my B+ runs at 398, at 55ma on EACH el34, but i am going to boost it to 110 each, which will probably drop the B+ to somewhere around 380.

The EH Kt88s look like a deal, good price, and tubelab has tested them .

I use the Hammond 272HX for a power transformer, so I am going to be pulling (about) an extra 30ma out of it, will this be okay? (its rated at 200ma) I might drop a heat-sink ontop of it for good measure.
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