tchgtr
Well-known member
I recently acquired a 2nd MXL 9000 on the used market for under $90, and wanted to share some things I do to them.
There is another thread somewhere in the archives about this basic cardioid tube mic, which has a lot of good advice from the local gurus, but I'm too lazy to dig it up. If people are interested, jsut search "MXL 9000". I'll put the schematic up here.
It's an odd circuit, with the typically odd choices by whoever designed it regarding the output caps - a 33uf electro in parallel with a .1uf film cap - so I replace those with a single 1.85 uf film cap, and remove all the RF filtering junk just prior to the output transformer.
It also calls for a 12AT7 in the schemo, but often comes with a 12AX7 installed. I now have some 12AV7s in both of mine, which keeps them nice and clean-sounding, but I may try some AT7s soon.
After all this, they sound better with the original capsules, but (as the smart people around here constantly remind us), the capsule is largely responsible for the sound of a mic, and I just can't get around these Chinese U67-style capsules.
I am using the original output tranny, and have not measured the stock tranny, nor does the schemo have any info about it. I think driving them with 12AX7 probably pushes them too hard, and the AT7 or AV7s are cleaner.
Enter the M-Audio Nova. I had one of these and recently got another used one (for only $25!-there are a few good things about being in SoCal, besides the weather). They don't sound great, but have the nicer, white-ringed "47-style" capsules in them, and they are solidly built, with a solid-state circuit. Whoever designed these put a 10uf output cap on them, probably to tame the brightness of this capsule in the circuit, but actually squashing it, IMHO. Seems to be the practice with these cheaper mics, to push the electronics hard to make people think they sound good. Perhaps putting a .1 film across this cap (similar to the original 9000 circuit) would make for a simple mod, but screw that, I took out the capsule, and put it in my first modded 9000.
Much better.
It fits in the 9000 mount, and opens up the sound of the mic very well.
Once I found the 2nd used 9000 and the 2nd Nova, I did the same thing, and then put the capsule from the 9000 into the Nova. Surprisingly, it sounds about the same, which showed me how much the circuit in the Nova was filtering.
I need to spend some more time with these mics in use to really get a handle on them, but already like them much better.
The first Nova was used as a donor body for a Royer dual-capsule mod (see thread below for photos), and many of the other parts were used also, including the Nova output tranny. We use ALL the parts of the mic here....
For now, I think I'll keep the 2nd Nova with the 67-clone capsule, and try it on a few things.
Some notes for anyone wanting to do something similar:
Both Novas I had were of differing ages, and one of them used SMD components. The first was more "old school", and had two circuit boards, while the SMD version had only one. Either way, you still get two 1G resistors and the output transformer which measures @7:1 reading Ohms. If you can get 'em cheap, they make nice donor bodies, with a somewhat U-67 shape.
As can be seen in the photo, I removed the inner layers of mesh on the first 9000, trying to get a better sound with the original capsule. I agree with all the people who say "Don't do that!". Now that I have a nicer-sounding capsule in there, I think the mic would sound better with the mesh back in, and the 2nd mic proves this, as I get it closer and closer to the other one. Also, the grill is weaker, and care must be taken when handling the mic not to deform it. Gus has already pointed all this out.
If you buy one used, make sure it comes with it's 7-pin cable, as these can be expensive to replace.
All in all, it's a pretty nice deal to get all the basic components of a cardioid tube mic for under $90, and it would be easy to alter the circuit to a more conventional design, if someone wanted to imitate a better-known circuit. Eventually, I will deal with the difference in grill mesh, and hope to have a nice stereo pair for under $200.
Thanks for reading..
There is another thread somewhere in the archives about this basic cardioid tube mic, which has a lot of good advice from the local gurus, but I'm too lazy to dig it up. If people are interested, jsut search "MXL 9000". I'll put the schematic up here.
It's an odd circuit, with the typically odd choices by whoever designed it regarding the output caps - a 33uf electro in parallel with a .1uf film cap - so I replace those with a single 1.85 uf film cap, and remove all the RF filtering junk just prior to the output transformer.
It also calls for a 12AT7 in the schemo, but often comes with a 12AX7 installed. I now have some 12AV7s in both of mine, which keeps them nice and clean-sounding, but I may try some AT7s soon.
After all this, they sound better with the original capsules, but (as the smart people around here constantly remind us), the capsule is largely responsible for the sound of a mic, and I just can't get around these Chinese U67-style capsules.
I am using the original output tranny, and have not measured the stock tranny, nor does the schemo have any info about it. I think driving them with 12AX7 probably pushes them too hard, and the AT7 or AV7s are cleaner.
Enter the M-Audio Nova. I had one of these and recently got another used one (for only $25!-there are a few good things about being in SoCal, besides the weather). They don't sound great, but have the nicer, white-ringed "47-style" capsules in them, and they are solidly built, with a solid-state circuit. Whoever designed these put a 10uf output cap on them, probably to tame the brightness of this capsule in the circuit, but actually squashing it, IMHO. Seems to be the practice with these cheaper mics, to push the electronics hard to make people think they sound good. Perhaps putting a .1 film across this cap (similar to the original 9000 circuit) would make for a simple mod, but screw that, I took out the capsule, and put it in my first modded 9000.
Much better.
It fits in the 9000 mount, and opens up the sound of the mic very well.
Once I found the 2nd used 9000 and the 2nd Nova, I did the same thing, and then put the capsule from the 9000 into the Nova. Surprisingly, it sounds about the same, which showed me how much the circuit in the Nova was filtering.
I need to spend some more time with these mics in use to really get a handle on them, but already like them much better.
The first Nova was used as a donor body for a Royer dual-capsule mod (see thread below for photos), and many of the other parts were used also, including the Nova output tranny. We use ALL the parts of the mic here....
For now, I think I'll keep the 2nd Nova with the 67-clone capsule, and try it on a few things.
Some notes for anyone wanting to do something similar:
Both Novas I had were of differing ages, and one of them used SMD components. The first was more "old school", and had two circuit boards, while the SMD version had only one. Either way, you still get two 1G resistors and the output transformer which measures @7:1 reading Ohms. If you can get 'em cheap, they make nice donor bodies, with a somewhat U-67 shape.
As can be seen in the photo, I removed the inner layers of mesh on the first 9000, trying to get a better sound with the original capsule. I agree with all the people who say "Don't do that!". Now that I have a nicer-sounding capsule in there, I think the mic would sound better with the mesh back in, and the 2nd mic proves this, as I get it closer and closer to the other one. Also, the grill is weaker, and care must be taken when handling the mic not to deform it. Gus has already pointed all this out.
If you buy one used, make sure it comes with it's 7-pin cable, as these can be expensive to replace.
All in all, it's a pretty nice deal to get all the basic components of a cardioid tube mic for under $90, and it would be easy to alter the circuit to a more conventional design, if someone wanted to imitate a better-known circuit. Eventually, I will deal with the difference in grill mesh, and hope to have a nice stereo pair for under $200.
Thanks for reading..
