[triod750]

Here are some spoils from the mail today.

GEC A2293. I don't know why I bought these...I think I was going to consider an OTL prototype with them? I will check them out on the curve tracer soon, two pairs.



More NIB Hytron 841, because these are cheap in Japan and you never know when they'll go extinct.



Speaking of extinct, here is a pair of 5998 I bought only because they are getting so rare! For a good price.



And I got all kinds of DarkVoice modification knick knacks. Output caps, Alps pot, resevoir cap and clamp, cathode resistors...I'll spare you from individual photos of all of the resistors, transistors, diodes, etc.



I am not really 100% sure those caps are going to fit. Highly unlikely to fit three per channel, but they are a bit taller than anticipated as well, soon we will find out.

At this point I just need my gyrator PCBs to give the DarkVoice mods a test run, it will probably be another week or so but I might get the HV regulator up and running this weekend.

Those A2293 sound really good with 12AU7 as driver. Powerful and relaxed.

 

[bcowen]

Those A2293 sound really good with 12AU7 as driver. Powerful and relaxed.

What 12AU7 are you using? I've been a bit underwhelmed with the A2293's in the Darkvoice so far, but have not given them much of a chance with different driver tubes. Going to fish my 12AU7 adapter out of the box now...

 

[triod750]

I've tried one Telefunken and two Philips. I might have a few others but I have just started to experiment. What drivers have you used?

 

[bcowen]

I've tried one Telefunken and two Philips. I might have a few others but I have just started to experiment. What drivers have you used?

I've only tried them so far with a pair of Hytron 7A4's and a Melz 1578 (6SN7). The Darkvoice uses a 6SN7 natively as the driver tube, but I have adapters for bunches of different tubes. Have a WE 396A in the driver's seat as we speak, but not with the A2293's.

 

[Galapac]

Fixed it for you...
Yeah - a German eBay seller that I bought from in 2019, is banning the US. He will not sell to US buyers because according to him couple packages (sent by German post) are several months (!) late and still not arrived to the US buyers.

Thanks yes, 2020. If it is the same guy I’m thinking of he has some nice 6080 Telefunkens I cannot get my hands on.

 

[johnjen]

You may have a great discovery there! If the stuff totally corroded all the internal elements the tube wouldn't work, it would be very quiet as a result, and that would be a major improvement! Good thinking, Zachi!

And speaking of dead/dying tubes…

Have any of you associated the last track of Daft Punks, Random Access Memories album, (starting at 4min mark of Contact) with a tube amp in it's death throws? It sounds to me like section after section (input driver, output section, psu) of a tube power amp consuming itself.
It makes me laugh every time I hear it…

JJ

 

[L0rdGwyn]

Here are the operating curves for the A2293.

 

[triod750]

Here are the operating curves for the A2293.

Thanks. I'm worthless at seeing how curves sound. I even have difficulties converting notes to sound. But I enjoy the music. And I like some curves more than others.

 

[triod750]

I've only tried them so far with a pair of Hytron 7A4's and a Melz 1578 (6SN7). The Darkvoice uses a 6SN7 natively as the driver tube, but I have adapters for bunches of different tubes. Have a WE 396A in the driver's seat as we speak, but not with the A2293's.

Please let us know the result of your experiments.

 

[bcowen]

Here are the operating curves for the A2293.

OK, so here's where things get weird with these tubes. There is *very* little info available on the web. Below is what I've found so far. Not suggesting either are correct, just showing what I've found. I have a China-made adapter (dual A2293's on top to 6SN7 socket on the bottom) that is wired (mostly) like the first diagram: Pins 1,2 and 7 are all tied together on one A2293 socket, and pins 1,2,7 and 8 are tied together on the other. Pins 3 and 9 are tied together on both sockets. The heaters on pins 4 and 5 are the same, and the grid on pin 6 is the same and by itself. This China adapter works fine in the Darkvoice, but does not work in the Incubus amp creating a very loud buzzing in both channels. Biggest difference I see is that your tracer info shows the cathode at pin 1 (versus pin 2 in the AVO tester info), and the anode at pin 3 (instead of pin 9 in the AVO info). Perhaps this is irrelevant since they are tied together? What confuses me is why all the pins that have no internal element are connected together. There's really only 5 of the 9 pins that should have (need?) a connection.

 

[L0rdGwyn]

OK, so here's where things get weird with these tubes. There is *very* little info available on the web. Below is what I've found so far. Not suggesting either are correct, just showing what I've found. I have a China-made adapter (dual A2293's on top to 6SN7 socket on the bottom) that is wired (mostly) like the first diagram: Pins 1,2 and 7 are all tied together on one A2293 socket, and pins 1,2,7 and 8 are tied together on the other. Pins 3 and 9 are tied together on both sockets. The heaters on pins 4 and 5 are the same, and the grid on pin 6 is the same and by itself. This China adapter works fine in the Darkvoice, but does not work in the Incubus amp creating a very loud buzzing in both channels. Biggest difference I see is that your tracer info shows the cathode at pin 1 (versus pin 2 in the AVO tester info), and the anode at pin 3 (instead of pin 9 in the AVO info). Perhaps this is irrelevant since they are tied together? What confuses me is why all the pins that have no internal element are connected together. There's really only 5 of the 9 pins that should have (need?) a connection.

I used the wiring diagram you posted above as a guide from Radiomuseum. If any of the electrodes have multiple pin connections, you need only connect one, either pins 1,2, or 7 for the cathode and either pin 3 or 9 for the plate, doesn't matter which ones. On octal tubes, the pins are often physically missing, like on a 6J5, I assume they were left in place on noval 9-pin tubes since the pins themselves are thinner and more delicate, so removing some pins might increase the physical stress imposed on the others, just a guess. A second guess is this tube was made as a possible replacement for a competing series pass regulator tube with a 9-pin base, so maybe it was beneficial to have multiple connection alternatives.

 

[bcowen]

I used the wiring diagram you posted above as a guide from Radiomuseum. If any of the electrodes have multiple pin connections, you need only connect one, either pins 1,2, or 7 for the cathode and either pin 3 or 9 for the plate, doesn't matter which ones. On octal tubes, the pins are often physically missing, like on a 6J5, I assume they were left in place on noval 9-pin tubes since the pins themselves are thinner and more delicate, so removing some pins might increase the physical stress imposed on the others, just a guess. A second guess is this tube was made as a possible replacement for a competing series pass regulator tube with a 9-pin base, so maybe it was beneficial to have multiple connection alternatives.

OK, that makes sense. And I misspoke earlier -- the adapter is for dual A2293's to a 6080 base (although a 6080 and 6SN7 are identical on base pin connections). I'm still wondering why this buzzing in the Incubus. I have no settings for testing these in my Hickok, so have basically plugged them into the adapter and tested them with 6080 settings. Although much lower in GM, no faults popped up while testing like that. Do you offhand know of a (more known) tube that is similar enough electrically that the Hickok might have settings for? Perhaps one of the two A2293 tubes has a problem that the Hickok is not indicating that is causing the issue.

 

[triod750]

Does all of your A2293 have the same getters? Round or square?

 

[L0rdGwyn]

OK, that makes sense. And I misspoke earlier -- the adapter is for dual A2293's to a 6080 base (although a 6080 and 6SN7 are identical on base pin connections). I'm still wondering why this buzzing in the Incubus. I have no settings for testing these in my Hickok, so have basically plugged them into the adapter and tested them with 6080 settings. Although much lower in GM, no faults popped up while testing like that. Do you offhand know of a (more known) tube that is similar enough electrically that the Hickok might have settings for? Perhaps one of the two A2293 tubes has a problem that the Hickok is not indicating that is causing the issue.

My question would be this: what is different about the wiring of the 6080 socket between the DarkVoice and the Incubus? I'd imagine that would get you the answer as to why it is not working, but sounds like a short to me. Something else you could do is put the adapter in the Incubus and check pin-to-pin continuity with a DMM to make sure there isn't a short between the electrodes of the A2293. I'm not aware of any near-equivalents to the A2293, sorry! I would check for shorts first and compare the pinout of the 6080 sockets between the two amps.

 

[JazzVinyl]

Awesome, thanks! I think I am going to ditch the carbon filter and add isopropyl alcohol to my solution, so I will downgrading to the 1 micron sediment filter I believe Ilfotol has anti-static properties as well, hopefully we the process right on the first try. Need to find a particularly dirty record for a before-and-after test

Wood Glue and patience is all you need!