It might not be necessarily the new wire. With analog there are other billion reasons why it might not sound as it should. Still, I personally can’t stay listening “new” wire with MC cartridges. If you recently futzed with the arm wire then you might try to break-in the entire assembly.
Disconnect the cable from preamp and load it with a resistor roughly equal to input impedance of your phonocorrector. Then run from a separate voltage source directly to the “cartridge” some “formatting” AC signal that you prefer. The Purist System Enhancer works very nice; the XLO’s RX-100 track 9 is very good or juts a straightforward pink/white noses will do. You will need to do it for a long time, so to convert it to 20bit WAV file and loop it from PC is a comfortable idea. BTW, when I said “directly to the cartridge” I hope you understand that I meant not the cartridge itself but the wire’s cartridge terminators. Surely your cartridge should be completely disconnected. I made years ago for this purpose a dummy head with 4 males cartridges - like pins … very comfortable to “cook” the analog lines….
If you need to ‘cook” the entire chain, it what I would do, then you need to feed it with RIAA Signal. The Granite Audio has CD-101 where some higher tracks have are good noises at ~4mV. You might rip them off and loop from PC (they are 1 min each or so). The solution that I personally use even more Moronic. Jim Hagerman that is posting at this site has an absolutely ridicules devise. It is a simple filter that takes you line level signal, droops to minus 60dB and writhe up inverted RIAA curve, so you can feed it directly to your cartridge side wire. The ridicules in this devise its amassing effectiveness and absolutely insulting price. In fact over my entire audio life I hardly had so many benefits for $50 I spent in audio. The irony is that anti- RIAA thing despite its offensive simplicity and cost has the RIAA precision much higher then most of phonostages, has less noise then most of phonostages and …. this damn thing also sound quite nice!!!
Sure it is not perfect-perfect, it has all indispensable problems of a poor passive preamp. (I have done some substantial sonic testing of this devise in past, do not ask me why). However, it is perfectly ACCEPTABLE to listen through this thing and even to make some conclusions. So, for a few weeks while am “blowing” my analog chain I load my DAW’s DAC output to this RIAA encoder and then it’s output I feed right to the tonearm input (I usually put the Sovtek “training” tubes into my phonocorrector). It wonderfully “blows” the entire chain and it usually is auditable when the chain begins to sound “softer”….In fact, after dealing with all those issuers, it become my strong conviction that any phonostage that pretend to be a High-End phonostage MUST have an inverted RIAA filer built in. If Hagerman can make if for $50 then I am sure the Boulder 2008 phonostage (BTW, not bad phonocorrector) should have it on board. Probably they did not put it in because they would like to keep price under $33.000.00….
"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche