Substution for 5842 input tube?

[neonthecat]

Hey George...
That's a good story how the Tubelab SE came to be. Thanks for sharing.

Just last night I had a friend over to listen to some music. I was all set to play some records with the "main" system. Then he spied the table where I have my DIY amps sitting. He was intrigued by just the 4 tubes sticking out of my SSE, and insisted on hearing it. Now, I'm on the hook to build him one!
It may be "simple", but it sounds very good!

[rknize]

Yeah, the D3a is not cheap and most of the eBay sellers are outside the US and so the shipping charges approach the cost of the tube.

Keep an eye out for a seller selling sleeves of 5 Raytheon 5842s. He tests them all and he had enough at the time that he could even sell a sleeve with 5 tubes that match fairly close. The consistency of these Raytheon military grade tubes is not the best. I was able to contact him directly and buy a couple of sleeves. This was about a year ago and he mode it sound like he was swimming in these things.

[tubelab.com]

Now I can't sleep.

Uh Oh, you are in for a really long night. I have some circuits breadboarded, and several more ideas that remain untested. I have this mega powered P-P amp breadboarded, but missing a power supply. I have a tweaked up red board that makes 100 WPC, again, missing a power supply. I have a dual Simple P-P board that needs a screen regulator, and of course both the Simple SE and the Tubelab SE could benefit from an external regulated supply. Now the complicated part is making one device to fulfill all of these requirements. Yeah, and I leave town on Wednesday for 2 weeks.

Yeah, the D3a is not cheap and most of the eBay sellers are outside the US and so the shipping charges approach the cost of the tube.

I think my pair cost me about $25 each with shipping. I got them at SY's insistence to build an early version of his phono stage. They are very quiet tubes.

Keep an eye out for a seller selling sleeves of 5 Raytheon 5842s.....The consistency of these Raytheon military grade tubes is not the best....This was about a year ago and he mode it sound like he was swimming in these things.

I had a box with about 50 used Raytheons in it that I used to make my original amps. They are highly variable tubes. These tubes are the reason for the trimmer pot in the cathode circuit. The WE versions are not much better. While digging through the warehouse last weekend, I found another box with about 20 5842's.

[jrenkin]

anyone try an E180F? I have a couple that I guess I may try when my Raytheon 5842s crap out...

[matt82609]

Thanks again George! Can't wait to get started on the TubelabSE!!

[bear]

Not to get off the track, but the popularity of that tube can be traced to some "NY audio mafia" phono stage work from the early 1980s. Prior to that it was used in its original design application which is/was a VHF type tube as a gain stage or in a high IF section... some people liked the way they sounded run for AF... Western Electric developed the tube - an interesting read on the design - and Raytheon went on to use it for various military applications. The "urban legend" has it that they are/were used in the front end of a certain anti-missle system fairly recently, maybe even still... where they seem to vary the most is in self-noise which becomes evident when you try to use them in a low noise circuit, you'd better have a big batch on hand to select from.

Btw, they work a very very long time... very reliable tubes.

_-_-bear

[Evenharmonics]

Originally Posted by bear

Btw, they work a very very long time... very reliable tubes.

I'm guessing that's for the lifespan of their cathode, filament or other things inside. I had one of Raytheon 5842 in my TSE dead after about 100 hours of use. The bottom of glass cracked and the silver coat in the tube burnt out. Hopefully it's an isolated case.

[rknize]

Did you...err...exercise your new sockets with a junk tube?

I've actually heard that the Raytheon 5842s don't last as long as some of the older stock. Don't remember where I read that, but it was on the Interwebs, so it must be true.

[Evenharmonics]

Originally Posted by rknize

Did you...err...exercise your new sockets with a junk tube?

Yes but it didn't feel different by much before and after. The other Raytheon 5842 had no problem though which led to my conclusion of structural defect of glass.

[jrenkin]

Has anyone tried the D3a or the E180F in the Tubelab SE yet? I was thinking about it for fun, but my "TubeCad" models show a poor high frequency response due to the large mu and miller capacitance.
Maybe the answer is to wire it up and measure...