Tube DIY Asylum

Just goes to show you never can tell.

24.174.113.158

In Reply to: RE: Interesting parafeed observations. posted by Caucasian Blackplate on June 30, 2008 at 14:40:46

This started out as an experiment on cheap, so we purposely didn't use the most appropriate iron, the choke load is 2 cheap 150H Hammond chokes for each triode section, mounted base to base, with windings wired in series and out of phase with each other to reduce hum, and lower capacitance. I got that from a post by Gary Primm.

This transformer was definitely not meant to be used this way, we just wanted to see what it'd do as a parafeed output. The guy who initiated this project tested the 124B frequency response as a parafeed, and got a 20 - 15K bandwidth with it.

His version of it had one 150H choke per triode and a supplemental load resistor. It's just a parafeed 6SN7 triode gain stage with a cap loaded power supply with resistors between sections (no chokes) using cheap electrolytics. With the Alps pots, I bet he doesn't have more than $135 in the whole project. The crazy thing about it is that he says it sounds better than his highly regarded single ended preamp, which has some very high dollar iron in it. He said he took it to a friend's house and it bested a $2k commercial preamp the guy had.

The project my bud and I did was an "upgrade" (choke loaded PDM supply with PIO caps, double plate chokes, DACT attenuators, and different operating points) of the original design. When my friend came up with this experiment, I doubt he ever dreamed this thing would sound all that great, it really has no business sounding as good as it does. Often he will build projects only to dismantle and reuse the parts on another project. He also built a PP transformer output preamp using this transformer as a load for LTP phase splitter. He called it the Nickel Wonder, but it doesn't sound as nice as the parafeed design.

I'm building a 6n1p-E version of it, so we all three will have one. I have some 1960s vintage flat black plates to try. I figure I'll have a whopping $330 in it less chassis. I guess we'll have to have a 124B parafeed preamp shootout!8^)

twystd

Follow Ups:

RE: Just goes to show you never can tell. - Caucasian Blackplate 17:56:25 06/30/08 (1)
- Cool! - twystd 18:11:22 06/30/08 (0)

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