Searching this thread for "5998A" doesn't turn up any results and isn't listed as a compatible tube in the manual.
I couldn't find much technical difference from the 5998 so I'm trying one now. It seems similar to a 7236 or 5998 in terms of power or loudness but I'd have to listen a lot longer to compare how they sound.
I see that the maximum grid circuit resistance is .25 megohms on the 5998A vs 500,000 ohms on the 5998
Am I going to damage the amplifier or the tube?
I have a Tung-Sol 5998 too, it's a great tube for this amp. This one is a little different. The glass and internal construction look like a 6AS7GA or 6080. Maybe it's like Odin's GE 5998A JAN. Mine is Sylvania JAN branded. I found a pdf description from Tung-Sol that says "The 5998A is a low-mu twin triode designed for service as a series regulator in DC power supplies. Except for the use of the T-12 envelope and a different base, the 5998A is identical to the 5998." Their documentation describes the 5998 as medium mu but I don't know what that means.
I have a Tung-Sol 5998 too, it's a great tube for this amp. This one is a little different. The glass and internal construction look like a 6AS7GA or 6080. Maybe it's like Odin's GE 5998A JAN. Mine is Sylvania JAN branded. I found a pdf description from Tung-Sol that says "The 5998A is a low-mu twin triode designed for service as a series regulator in DC power supplies. Except for the use of the T-12 envelope and a different base, the 5998A is identical to the 5998." Their documentation describes the 5998 as medium mu but I don't know what that means.
Thank you! So far I've been enjoying it but I haven't tried comparing it to the 5998, but I think it sounds better than my 6AS7Gs, 6080s, or 7236s. It came in a pack of 5 all in similar condition.
Today I got a pair of RCA 6922s which are marked "RCA 6DJ8/ECC88 Made in Japan" with "7835." on one tube and "HA" on the other. I've never heard anything about Japanese tubes but they supposedly tested strong (10,750/10,600 11,000/10,500), and they were only $25 each. They sound great with the 5998A!
Here's a photo of one of them. It has a sort of L shaped piece of mica over the top of the grid frame that I haven't seen on my tubes made in the USA, Holland, or Russia. I'll try to get some better photos when I swap them for the Sylvania or Siemens tubes I've got coming.
Well, here's the newest batch from EBay. A bunch of cheap rectifier tubes and some power tubes too.
First the Rectifiers:
First image is a set of 6N1P-EV shipped from Ukraine but one makes a hum, waiting on a response from the seller about that. The labels look great at least...
Next is a set of 6N23P Voskhod Rockets. I noticed the tubes are built differently and have different labels but both are 6N23P and tested fairly close. They sound good but I already had a nice set of 6N23P-EV so I didn't listen long enough to make a lasting impression.
3rd, CBS Siemens 6DJ8s. These sound great. Very clear, with powerful bass right down to the really low frequencies. One of my favorite sets. I noticed the tube on the right flashes on cold starts, maybe the left one does too but I don't see it because it's facing the other way? The same thing happens with the Japanese RCAs.
The last ones are a set of Sylvania 6DJ8s made in USA. They sound good but I didn't get much of an impression of those ones either. I keep going back to the CBS Siemens.
The Power Tubes:
That last Tung-Sol 7236 I posted was good, and the seller updated to say the tested the tubes as 5998s on their tube tester (I guess they had no settings for 7236? idk) so I bought another. It looks almost identical to the first one so I didn't bother with photos. It has triple mica, rectangular getters, and enclosed grids. They both have writing inside on the plates so I wonder if they were part of a testing or development batch. This one says "L3X." I will have to compare this tube more against the 5998, 5998As, and the Sylvania 7236. It sounds great and powers my HD700s better than any of the 6080s or 6AS7Gs.
5th and 6th photos are a Cetron JAN-5998A from a seller in Taiwan. It looks like it shares a lot of parts with the Tung-Sol 7236. It sounds good. I didn't listen a lot but it's similar to the other 5998As and 7236s that I have.
Last two photos are of a NOS Sylvania 7236 in great condition that I found and I went for it. It sounds good but I already had one so I didn't listen much.
That is probably going to be the end of my collection for this amp, unless I can find a deal on another 5998 or a 421a, or maybe some Telefunkens... Maybe I'll try one of those adapters for the rectifier tubes...
• Woo WA3 was due for a dose of routine maintenance. Of what does this consist? Well: cleaning adapter pins, tube pins, headphone socket, rear RCA input sockets, IEC power socket prongs. Even the opened fuse (SR Purple) holder gets a going over, as does the disassembled volume shaft / volume knob.
• With all that done, it is only fitting that WA3 be ‘tubed to kill’ …
[Chatham JAN 5998, pair Brimar CV455 (KB/FB Footscray)]
• Woo WA3 was due for a dose of routine maintenance. Of what does this consist? Well: cleaning adapter pins, tube pins, headphone socket, rear RCA input sockets, IEC power socket prongs. Even the opened fuse (SR Purple) holder gets a going over, as does the disassembled volume shaft / volume knob.
• With all that done, it is only fitting that WA3 be ‘tubed to kill’ … [Chatham JAN 5998, pair Brimar CV455 (KB/FB Footscray)]
I've only had the WA3 for a week now but it's quickly becoming a favorite of mine. There's a musicality there that i'm finding irresistible. The AC and WA3 have been my work happy place haha. I need to bring it back home to run it against the Stratus and Kenzie!
I've only had the WA3 for a week now but it's quickly becoming a favorite of mine. There's a musicality there that i'm finding irresistible. The AC and WA3 have been my work happy place haha. I need to bring it back home to run it against the Stratus and Kenzie!
• What tubes are you using in WA3? I have found that I certainly prefer a variety of ECC81 / 12AT7 tubes, with Pulse Tube Store adapters, over ECC88 / 6922 / 7308.
• In any event, you are right about WA3’s musicality. I actually prefer the WA3 to its bigger OTL sibling, WA2.
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[Chatham JAN 5998, pair Brimar CV455 (KB/FB Footscray)]
