It appears that some of my personal emails to various parties about the AP-120 have found there way into the Circle. I thought I should post and clarify. I was a previous owner of an AP-110 which was professionally modded. I purchased the 120 w/trade from Sekei. Andrew was great to deal with. Since then several of you have emailed me about the mods and my impressions.
Both the 110 and the 120 had high gain. My 120 's gain was lowered by adding resistors into the circuit before the gain switch. I believe Wayne at Boulder accomplished this in another fashion. I am not an electrical engineer so I can't say which is better. Either may work fine.
My unit, when bench tested had channel imbalance, which was corrected by adjusting the pots to the correct value (for 12AX7). If someone puts in 12AT or 12AU that value is different and those tubes may have some different sonic characteristics. The stock units may be fine, or may have been set up for the Chinese tubes but if changed I would check this.
My 120 when bench tested also showed some change in frequency response when using the gain selector switch. With the addition of the resistors to lower the gain in my unit the flattest response is now at -3. There is slight emphasis in bass at -6 and a slight high end bump at 0. Since we don't have schematics or input from Audcom I don't know if this is designed in or just a result of the electronic components.
The caps used in the 120 are an upgrade of the caps that were in the 110. I said that they may be a copy of the Auricap but I have been told by people smarter than I that there are better Chinese caps, as well as other brands including those installed by Wayne at Boulder. It appears different professionals have personal experience with caps and I would not choose to second guess them.
I don't recommend tubes as they are a personal choice. I believe the tubes sound is different in different systems and may be somewhat dependent on the amp, interconnects, and speaker resistance. I have tested most 12AX7 tubes in both units and IN MY SYSTEM I like the Mullards for NOS and the Sovtek 12AX7LPS. Others may be better in your system. Finding the right one for your ear is part of the fun.
The only other mod I have done is replace the plastic window with glass, a farily easy project. I' had the glass cut at Home Depot, masked and spray painted a black line on it and replaced it with the handy glue gun.
I am not an expert and can't afford to be a true audiophile, but I love good equipment at great prices. I really like the 120. I believe it to be a great bargin for a remote controlled tubed preamp. Aestetically it is quite a step up, better power supply than the 110, better stock caps (don't buy it for the phono section). Hope this sets the record straight.
