Robin or Rodin Mod of an ARC SP3-A1???

Topic: Robin or Rodin Mod of an ARC SP3-A1???

I just purchased a modded SP3A-1 on ebay, item number 310503686812. On the transformer are the words "Robin or Rodin Full Mod". It has a completely different tube power supply with a tube rectifier 6BE3. Also, the number 1 main out does not have contour or bass/treble connected, only balance. This line output sounds like a SP8?? clean, open, transparent...especially on the phono stage where it appears the circuit has been updated. The number 2 main/line out has all the tone controls connected and sounds like a vintage SP3! deeper soundstage and rich/warm. How did this guy do this? It's like having two different sounding preamps in one. Has anyone ever heard of doing this to a SP3? Also, the problem in one channel appears to have been from a Beldon wire touching a resistor on the phono board...can been seen in one of the pics. I may have lucked out on this one..after getting the wires not to touch it has played perfectly for several hours.... Any comments would be welcome. Thank You.
Interesting. The SP-3A1 had a tone defeat switch for the tone controls. It does not however have a tube rectifier in it. I have an SP-3C preamp. The preamp uses a newly designed ARC FET regulated power supply which IMO is vastly superior to the old power supply with it's lousy twist lock lytic filter caps and it's string of zener diode regulators. They can easily go out of voltage tolerance and the FET supply is eminently quieter. I recommend the upgrade without reservation.
Thanks for the tip Geek,your full of surprises and excellent advice.If I ever score an ARC product I'll be a knocking one day,Merry Christmas,James
I am commenting for my cousin who is traveling today. Together we both have an original SP3A-1 and I also own a SP-3C. Yes the SP3C sounds more modern....but late at night after the original warms up at least 3-4 by speakers. Maybe it takes that long for the old power supply caps to charge?? Harry Pearson always thought the complicated circuit in the original added depth, I agree.

But back to this odd bird he/we bought on ebay....basically we were curious what the hell was done to this preamp. FYI, when he pushes the tone control defeat on MAIN LINE OUT2 sounds like an very old tube preamp. Using MAIN LINE OUT1 good grief modern sound, in fact maybe the best SP3 he/we have heard. The closest preamp that we have heard that sounds like this is an SP8 version 1. FYI, the tech who did the mod upgraded the wire to ASHA??? large black wire on Main1 out, he left the old grey beldon on Main2 out. After we have played with this thing we are going to take it to our Tech and have him look the power supply over and see what the hell this Mr. Robin/Rodin did?? I forgot to mention he added an extra small transformer over the A-1 sticker, I assume for the tube power supply.

We were hoping someone in audioland would recognize his name. The preamp was modified in the state of Washington. The sticker inside the preamp is smudged where the B or D is in the middle of the name. This is one strange / unique SP3.....
Thank you for the kind words. Happy Holidays and a joyous New Year to you!

I loved your story about comparing the old SP3A1 to the SP3C. It confirms what I had suspected just from reading the description of the "C" update. I can definitely imagine different reactions with one person preferring the "modern" sound and another the vintage sound. That's been my experience with many vintage vs. modern comparisons, and it's one of the reasons this hobby can be so much fun. At least you have both so you can choose whichever one fits your mood at the moment.