Hey guys, some of you may remember my old post on the Shure M65 Phono Pre:
https://www.diyaudio.com/community/...tage-a-tasty-m65-preamp-for-under-200.363607/
It's a good DIY kit that uses a pair of 12AX7 in anode-follower. Some impedance issues with certain amps but good for the price. Here's a schematic of one channel:
Well with the cost of 12AX7s these days, I thought I'd try a build with some 6N2P tubes I got for a song. The regular version heats the tubes with 12.6v on pins 4&5, with 14v coming off the transformer. I had a custom transformer made with a 7v 2a secondary so it delivers 6.3v to pins 4&5. So I built this thing now, and hooked it up to my system, and most of the audio band sounds correct, but the highest frequencies, like cymbal crashes, are gone/mangled, so I'm thinking the "pole" might be in the wrong place now? The b+ for this thing is only 100v, so the tubes are running at the low end of their range, and the load lines for the 12ax7 vs 6n2p are rather different grades when we're this far down the charts... Any thoughts?
thanks!
https://www.diyaudio.com/community/...tage-a-tasty-m65-preamp-for-under-200.363607/
It's a good DIY kit that uses a pair of 12AX7 in anode-follower. Some impedance issues with certain amps but good for the price. Here's a schematic of one channel:
Well with the cost of 12AX7s these days, I thought I'd try a build with some 6N2P tubes I got for a song. The regular version heats the tubes with 12.6v on pins 4&5, with 14v coming off the transformer. I had a custom transformer made with a 7v 2a secondary so it delivers 6.3v to pins 4&5. So I built this thing now, and hooked it up to my system, and most of the audio band sounds correct, but the highest frequencies, like cymbal crashes, are gone/mangled, so I'm thinking the "pole" might be in the wrong place now? The b+ for this thing is only 100v, so the tubes are running at the low end of their range, and the load lines for the 12ax7 vs 6n2p are rather different grades when we're this far down the charts... Any thoughts?
thanks!