Check this out, 840 users.
I always say "Don't leave home without your ART Levelar", so this might apply to you too.
Looking at this pile of ďdead bugsĒ on my desk reminds me of something I would like to pass on to our fellow Planeteers who are brave enough for Slowieís mod:
Replacing the sub-par op amps in youíre ART Tube MP and Levelar!
They used TL072, TL074 and NE5532 op amps. Yuck. I pulled them, put in gold machined sockets and plugged in AD712 and AD713 op amps and they seem to sound a bit more transparent, especially the MP. I am a bit concerned about the current draw on the AD parts since there does not appear to be much headroom in the supply (the heat sink runs HOT). Would like to try an OP470 for the quads (the venerable, powerful, revered and lovely OP27 in a quad pack!!!) and some Ď275ís for the duals, but Iím a bit short on Ď275ís at the momentÖ
The tube is the main gain stage in the MP and at least one channel of the op amps is used to control the phantom power, but I believe that there is at least 20dB of op amp gain when the gain switch is pressed. Perhaps other op amp channels are used to control grid and filament voltages, I donít know. Most likely some line driving for the outputs as well.
The Levelar does not provide much gain (low mu 12AT7 rather than the 12AX7 in the MP), so I donít know how much changing the op amps does here, but I managed to break one of the interconnecting cables (no connectors!) and had to pull it out and make a new one.
Be careful with this stuff, itís not made for multiple re-assembly! (Especially when you're watching X-Files and working on it at the same time.)
I donít know if the higher grade ART stuff uses these same op amps. Iíd be surprised and disappointed if they did.
Anybody else out there tried this? Hey, these things are only about $100 each, so if you really screw it up youíre not out that much.
Iíll post on 1680 and OT. Let me know!
Don't forget to leave good footprints behind.