by Rob-NYC »
Thu Aug 13, 2015 1:51 pm
Faza, there are two basic problems; one is the input point and the other is powering the B+ transformer without powering the mech motor.
When I bypass the existing preamp with a modern one the input point I use is C107 (top and C146 (bottom) on this schematic:
http://www.verntisdale.com/schem/shfa1.jpg If you choose to go in through the pickup input, you'll need to reduce the level and bass on the signal from the MP3 player to a level similar to the cart.
The problem of powering the amp independent of the mech requires connecting the B+ tran's primary to a SPDT switch or relay.
I can pretty much guarantee that the limits of the system will be disappointing compared to what digital audio can produce through modern equipment. Adding a tweeter to each channel will help a bit though.
The people selling these machines with "Pod-Mods" (as i call them) are basically hucksters trying to make a sale to potential clients who probably shouldn't bother buying one if it requires that extent of modification to justify the purchase.
Frankly, I would treat this as what it is, a near 60 year old automatic record player with mediocre pickup and speakers, but which taken as a unit is enjoyable as-is. A better use of your efforts (IMO) would be to incorporate the later tonearm and cart, add an outboard preamp and two horn tweeters. Even just a better preamp and tweeters will make a big improvement.
Rob/NYC
Rob-NYC
"If we believe absurdities, we shall commit atrocities" -- Voltaire
