The ARC LS-7 is an ideal line stage to upgrade. I upgraded mine with the help of two long time Audio Research employees / friends in their spare time around 10 years ago. One was Ward Fiebiger an ARC engineer who has since passed away. The other was a since retired ARC service tech who worked there for many years. The power cord was replaced with a Furutech gold plated IEC ( used with audiophile grade power cord) , Two (2) 4 mf 425 V Stealth brand coupling caps ( mounted on underside of circuit board) replaced the stock caps. Steath brand (sourced from Peter Montcrief owner of Wonder caps) bypasses were also used ( mounted on top side of board). The stock ( V1-V4) 6922 Sovtek tubes were replaced with 1960’s Amperex 7308’s ( NOS). The two power supply caps were replaced with higher value ( low ESR) Mundorf caps 680uf and 220uf . The 680 uf electrolytic power supply capacitor was bypassed with a 2 mf reference grade V Cap ( mounted on underside of circuit board). Another smaller value teflon cap was used as well for bypassing the Mundorf 220 uf electrolytic capacitor. The rectifier stage was upgraded with Schottky zero recovery diodes. The power transformer in this modified line stage remained stock. The opamp in the power regular stage was replaced with a discrete Burson V5. Damping material was added to the border of the top cover ( underside). A 100K Goldpoint brand stepped attenuator replaced the stock Alps brand gain control. The chassis was damped ( isodamp) and the stock tube sockets were replaced with ARC gold plated sockets. The stock rubber ARC feet were replaced with brass still points. The unit sits on a 2D Sieismic sink for isolation. This line stage is currently used with an ARC VS 115 amp ( using Vandersteen 3A signature loudspeakers) with outstanding playback resolution. The sound stage is deep and very wide with a lush top end and excellent mid and low end bass. Parts cost was pricey ( around 2 grand as I recall) but worth every penny and essentially turned the LS-7 into a small chassis single ended Reference Line stage.
