Any firms that do mod's to amplifiers?

Check out The Great Northern Sound Company at http://www.greatnorthernsound.com/home.htm

Andy Bartha in Davie Florida has done several mods for me on different equipment. He builds his own amp and mods just about any others on the market. Go to abaudio.com for more info.

Wrong link .Andy Bartha website is :http://www.ecommercemarket.com/audiomods/

I just received my Hafler Dh500 back from musical concepts(musicalconcepts.com). I had extensive mods done to it. A 599.00 front end circuit board with extensive use of schottky rectifiers and black gate caps. Gold rca jacks and copper binding posts installed. An interchangable power cord was fitted, and two 500 watt torroidal transformers were installed to replace the 680 watt block transformer. In addition the TWO power storage caps. were replaced with four superior musical concepts caps and the system was set up for a totally dual mono design with 156000uf of storage capacity. It was not cheap but I would put the musicality of this amp up against ANYTHING at ANY PRICE!! It is that good!! You can not reach the level of strain it just stays sweet and solid at all volumes and every last bit of grainy brightness that it had originally is now non-existent. Since I have had it back for only 3 weeks I am informed that it will get only sweeter for the next month or so. I can hardly wait to hear the full break in. I would recommend this amp upgrade at twice the cost I paid it is truly excellent.