Tube rolling is a fun aspect of the audio hobby. It only gets tedious when audiophiles start splitting hairs about a VT231, 5692, etc. I draw the line when an audiophool claims, "...my line stage preamp resolves the R train rumble under Carnegie Hall better when I use a 6AS7 in place of the original 6SN7..." 🙄
Those two tubes may be pin compatible BUT a power transformer 🔥melt-down🔥is imminent since the 6AS7/6080 draws 2.5 amps @ 6.3V. That's over 4 times more filament current drawn by a 6SN7, which only draws 0.6 amps @ 6.3V.
💣 💣 💣 Rolling tubes is dangerous unless you have a working knowledge of electronics to comprehend tube data/specs. 💣 💣 💣
It's been a while since I listened through Telefunken 12AX7 smooth plates on an RCA phono. Since I used to graft this circuit on a Dyna PAS preamp, I ordered a pair of 12AU7/12AX7 > 6SN7/6SL7 adapters to relive the experience on my RCA octal preamp.
Back in the 90s, Steve @ Angela Instruments had a boatload of Raytheon 5755s and shared a sleeve with me. Since I never found a project requiring these tubes, I got a pair of 5755/WE420 > 12AX7 adapters to listen to them in the Shure M65 clone. Piggy-backed to 12AX7>6SL7 adapters, they also worked nicely with the octal phono preamp.
Despite slight differences in transconductance and plate impedance between the 6SL7/7F7 and their younger 9-pin siblings (ECC83, 12AD7, 5751 and 5755), there was no visible variation in square waves nor frequency response aberration when I bench tested those tubes in both circuits.
Admittedly, loctals don't look as glamorous as their octal cousins with bakelite bases. But I'm very fond of them to the extent that I built and use a full function loctal preamp. I've been adopting unloved loctals at radio shows and hamfests. Essentially the industrial looking 7F7 and 7N7 are rebased 6SL7 and 6SN7, respectively! My only issue with loctals is, the tube pins are prone to corrosion. This is easily remedied by a wire brush + DeoxIT before use.
I purchased these tube adapters from the seller xulingmrs. They are very well made and fairly priced. Shipping cost and transit time from China was also reasonable. Highly recommended!
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