Tube Preamps...I'm sold

John: I agree the AR SP-10 needs some modification to bring it to the MK II status. My SP-10 MK II was modified by Gary Muffely , a fellow who knows more about circuits than anyone I have ever met , and at my age that's saying something . Sorry, I can't say that I have had the same experience as you. My "10" was carefully re-worked and select tubes replaced the factory set. Images appear to float in the air... Of course my set-up may account for the experience. In real $$$$ terms one would have to spend 12K to duplicate the "10". You are on the Mo'Money " Top-tier performave does not come cheap" .

Jafox :
After sliding into the slumber position for the night , my foggy-bottom mind woke me up. One tweak, that I failed to mention, that has an impact on what you hear , I have performed since The Absolute Sound wrote of it in '93 is shooting a tad of DC current into the "10's" imputs. Nothing extreme, just using a Mc demagger as TAS outlined. That smack of DC helps to eliminate AC eddies that form around the leads of almost all compoments within the case. The sound is transformed as is the unit. XLO also put out a CD that roughtly producees the same results. The process is performed every month or so 5 seconds on 5 seconds off via a interrconnect. Remarkable results for tube preamps. Enought ... Golden Slumber Time.

Crem1 - Thanks for the tip on the MC demag device. I never heard of this process. Now I have the itch to try.

I always wonder where my SP-10 might be today ... no doubt it has changed hands a few times since I sold it in 95. You describe this very well as portraying floating images. This is why it took me so long to find a product that had the SP-10 magic but then went to the next level of refinement. It was no surprise that it took the LS5, a return to an all-tubed line stage since the SP-10 a decade before, to bring back that musicality. All of the ARC "hybrid" designs from the SP-11 through the LS2 were too sterile for me.

As for SP-10 MK II status, as I recall, one can tell of this by seeing 2 pairs of 1 or 2-watt resistors, each pair in series and sitting on the board in a teepee fashion. I have since forgotten what the benefit or "fix" that came with the MK II update.

I would be reluctant to do any serious circuit design changes but rather simply focus to replace passive components in "critical" areas. But I would also be aware that some of the musicality/dimensionality might be lost for the sake of greater resolution and detail with "refined" passive parts. Getting both of these improvements would likely require a change to a different product.

I made one slight change in the MCP-33 to allow for the MC load to be as high as 200 ohms instead of the maximum 100 ohms. The MCP-33 owner's manual talks about this as a possible limitation of this product for some cartridges. And ideally my Clearaudio and Koetsu cartridges perform their best at a 500 ohm load but they work very well with the MCP-33 with a 200 ohm load...even the 100 load. I am reluctant to change the one resistor value any higher as this could affect any number of critical circuit parameters. And I would be reluctant to do anything similar in the SP-10. Having a circuit guru helps a lot.

John

Jafox ( John) : For the sake of transparency & accuracy , The demagg tweak was proposed by Thomas O. Miller , " Tweak of the Year" , " The Absolute Sound ", Volume 18, Issue 92 Winter , page 103. The tweak came to the attention of Mr. Miller via Roger Skoff of XlO Electric who co-produced the CD "The Sheffield/XlO Test & Burn-in CD" (adv.p.35). The XLO CD also contains calabration frequencies ( sec.6 & 7) that appear to do the same. According to XLO , the CD can be adapted for use with phono imputs.. Use either tweak only at very low listening levels-- afterward no problem , only jaw dropping sound . XLO is still around I believe , p/h 909-466-0382.

The demag device ran an audio waveform- not DC.