Can I use my pair of Siemens 7308 Gold Pin in the Freya + ?
If so, what adapter would you recommend?
Thanks Mark
If so, what adapter would you recommend?
Thanks Mark
No.
If you want to try the super duper tube-rolling dream, get some RCA 5692 for the Freya.
Or just realize that the 6SN7 is one of the very best tubes made for audio, ever, and be happy.
If you want to try the super duper tube-rolling dream, get some RCA 5692 for the Freya.
Or just realize that the 6SN7 is one of the very best tubes made for audio, ever, and be happy.
No worries thanks. Just called the Australian importer and they ave no date for arrival. they have been on order for 18 months, so no rush........Covid!!!
The 7308 is a 9-pin miniature specialty tube in the 6DJ8/6922/ECC88 family and is not compatible with the 6SN7 type. What is electrical;y equivalent in the 9-pin miniature is the 12AU7 and its variants. So if you want to roll 9-pin into the two right-hand octal sockets you'll need a "12AU7 to 6SN7" adapter found on eBay. I have a slew of NOS matched pair 12AU7 types purchased for rolling in my Rogue RP1 preamp. I now have the Freya+ AND noticed there was such a thing as a 12AU7=>6SN7 adapter. Hmmm. Sure enough the two are very close or same spec-sheet-wise. The big diff is that when connected for 6.3V operation the 12AU7 (center-tapped 12.6V heater with the two halves connected in-parallel) would draw 1/2 the heater current of the 6SN7 from the Freya's heater supply 300mA vs 600mA, resp. Sounds like a good thing but I knew that some heater supplies depend on the hot resistance of the usual tube for regulation (i.e. a series resistor). In that case the 12AU7 would see a heater over-voltage so I contacted Schiit. But they didn't want to tell me about their supply (was it regulated?) and blew me off. But I had a hunch and tried the adapter and it does indeed function normally. By that I mean the two 12AU7s lit up normally, look normal when fully hot, no misbehavior and there's no change in appearance of the two left-hand 6SN7s. So there's another outlet for the tube rolling junkie like me. And if you have deep pockets and want to go straight to the very top shelf you should seek the 7316 - thought by many to be the finest 12AU7 ever made, according to my reading.
Yes, the 6F8-G is the very first edition of the dual-triode 6SN7. The "industry" at that time in the 30's loved the 6J5 single triode. What would be loved even more would be two 6J5s in one bottle so RCA did that circa 1937. One camp in the industry wanted better grid isolation for one of the triodes so a grid was brought out to a top cap - all housed in the big ST-12 envelope. Have you noticed what's happened to the pricing over the past couple of years!?
PS>
There's a good history of and listening test for the NOS 6SN7 written-up in the 1999 edition of Vacuum Tube Valley magazine, attached.
There's a good history of and listening test for the NOS 6SN7 written-up in the 1999 edition of Vacuum Tube Valley magazine, attached.
I think I heard them refer to it as "semi-otl" or something like that. I did swap out the coupling caps and HV bridge with some "upgraded parts".
Probably wouldn't take much to deduce what they're doing.
Probably wouldn't take much to deduce what they're doing.
If it is or like the Aikido it looks (to me at least) like the circuit would invert the input. Do folks talk about that...?
Back to tube rolling. Does anyone know how Schiit powers the tube heaters? I read on diyAudio.de that the heater supplies are simple R-C filters - meaning there's a series R and a C that feeds the heater. That shakes my idea of using 12AU7s b/c they don't draw enough current to draw down the voltage.