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In Reply to: RE: How about the lowly Realistic SAF-24B (4x6BM8) posted by GRH on January 26, 2015 at 14:06:31
Gary,
Please do get it running and tell us what it sounds like.
If you have the schematic, post or link to the drawing. Please post a clear photo of the jack set.
As it's P2P construction, you can "go to town" on modifications and/or upgrades.
I'm guessing the phono section uses AC heating. If you switch to SS rectified B+ and combination biased "finals", you gain more than enough extra 6.3 VAC current to build a DC heater supply, for the phono section.
Decent "iron" is always promising. After refurbishment and mating with suitable speakers, you rate to end up with something nice.
Eli D.
Follow Ups:
Here's a pic of the rear. It is interesting in that you can mix the Aux, Tuner, and "Preamp" inputs. The Pre input is selectable between phono and tape head.
I don't have a schematic but I did find one for the earlier SAF-24. The 24B has full wave bias rectification and a separate hum pot for each channel.
So, true fixed bias (no trim pots.). :> ( Switching to SS rectified B+ will yield a "taller" B+ rail. Those extra volts could allow for self biased "finals", along the lines of the ASL AV-8. FWIW, I'd use a shared RC bias network in each channel. A shared network will compensate for minor imbalances in the PP pair.
Balls to the wall refurbishment might include elimination of signal shaping circuitry, a rotary source selector switch, and installation of a tweaked RCA phono section. Unlike the wimpy OEM circuitry, the tweaked RCA setup really can drive the recording O/Ps.
Eli D.
I'll try it with my Altec 604E's. It should have plenty of power. I replaced the selenium rectifier and added series resistance to get the bias at slightly less than -24V. I'm not sure where it should be. Couldn't find a good recommendation for PP. The selenium rectifier produced -26.5V. It's certainly easy to beef up the power supply cap's. Not sure I'll bother to add DC heater or not.
Gary
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