^ Thank you both for the info, a lot. I think this Aphex thingy might do the trick.

This issue cropped up and I said, man, I wish the Tech Room still existed right now. Lo and behold. I guess this is the new Little Tech Questions From Your Day thread?

Anyway, this past year I picked up a couple of Rane ML-1 preamps. IMO these are a real sleeper--clean, good two-channel rackmount preamps with Burr-Brown chips, with an option to send them S/PDIF out, and one of the few Rane items that uses a standard power cable (instead of their weird phone cable power situations) --as long as you don't mind getting behind it to adjust the gain with a tiny screwdriver. Since there are plenty of opportunities for usually set-and-forget, I think they're an incredible deal. They very occasionally pop up for about $100 (for two nice channels) lately.

I've been using this one with a condenser (4033) on one and a dynamic (635a) on the other. A few days ago when I fired it up, the 635a made a crackling speaker noise out the mic (going the wrong way). That's not great, but I noticed the mic (and pre) was still passing sound, so I winced and shrugged it off. (I'm going to need to check that mic out more closely.) Then yesterday I noticed when I swapped out the condenser for another condenser that the phantom seems to not be working. Both condensers themselves are still fine, glad to say.

So it seems that the phantom has crapped out. Gain is still working on the dynamic, and it's still sending to the S/PDIF.

When I've glanced ignorantly at other simple preamp build schematics and info, it has seemed that getting phantom going is one of the easier things to do.

Sure, I didn't pay much for this, and I have another, but I hate the idea of letting something go to crap just because a fix is too expensive. Any basic advice on how I can trace out fixing this phantom with limited skills? My dad is a retired EE but he doesn't really enjoy messing with this stuff on my behalf.

https://www.ranecommercial.com/legacy/p ... ml1sch.pdf

There’s the schematic. The last page shows the power supply, and it looks like the +48V comes from the +15V rail via boost circuit. (Assuming you’re comfortable doing so) check the voltage coming from the boost circuit first and work your way downstream. Could be a switch or blocking cap…there won’t be too much in that path.

Also, external phantom supplies are inexpensive and readily available.

This is super helpful, thanks very much.

Adam P wrote: Thu Sep 30, 2021 9:33 pm Also, external phantom supplies are inexpensive and readily available.

Agreed! But my notion is --maybe I'm wrong and it could be coincidental-- if I'm also getting a crackle sent out of the dynamic diaphragm, I'd better get in there and remedy it. (The fact that phantom is now down seems to indicate to me it wasn't just a bad cord or something like that.)

Bubber wrote: Fri Oct 01, 2021 7:27 am This is super helpful, thanks very much.

Adam P wrote: Thu Sep 30, 2021 9:33 pm Also, external phantom supplies are inexpensive and readily available.

Agreed! But my notion is --maybe I'm wrong and it could be coincidental-- if I'm also getting a crackle sent out of the dynamic diaphragm, I'd better get in there and remedy it. (The fact that phantom is now down seems to indicate to me it wasn't just a bad cord or something like that.)

If I’m understanding correctly and you’re getting a physical sound coming from the diaphragm I’d the mic when phantom is engaged, my first instinct would be that one of the signal conductors does not have 48V on it anymore and the diaphragm of the mic is getting 48V across it, exciting it (similar to testing a speaker with a 9V battery). I would think that if it was crackling that would indicate an intermittent issue…constant DC across the element would cause it to move and then stay, I’d expect. But I don’t know for sure. Do you have a meter that you can use to see if each of pins 2 and 3 on the preamp show 48V with respect to pin 1?

Kniferide wrote: Fri Jul 30, 2021 2:41 pm I've been playing my Jazzmaster since 1994 and I never use the top circuit. Always found it to be a totally useless tone. I've considered installing something weird up there, but in the end, when I finally end up doing a refin on it, I'm probably just going to have a custom pickguard made with no top circuit, and no tone knob at all. Just switch, and a volume pot.

Simplify:



Recommended!

Dr Tony Balls wrote: Tue Sep 14, 2021 9:39 am

Garth wrote: Tue Sep 14, 2021 8:47 am Neal used my Marshall JMP 2204 in practice Thursday, sounded great. Took it to the Campout Friday and it was DOA.

Symptoms: Not getting power for some reason. Power indicator light on the mains switch did not come on.

What I had time to check: Fuses all appear to all be in order

What I feel like are the next logical things to check and within my skill level: the light bulb in the switch (admittedly, in the stress of the moment I didn't think to check to see if the tubes actually lit up), and the power cable itself which I believe is original and admittedly not the best-looking upon visual inspection. I'll probably clip the end of a good IEC and wire that in there.

Any other easy/obvious suggestions I should consider? I didn't reseat the tubes because it still has the back on and I didn't really have time to futz w/ it but regardless the power light should still have come on.

You're correct. If the Mains fuse is good, about the only things that could be at fault are the switch itself (either the contacts or the bulb) or the power cable or socket, if you have one. MAYBE a connection inside opened up but that seems unlikely unless it's been modified.

I wouldnt focus on anything tube-related. If there was a problem there it would blow a fuse.

Confirmed, this was just the hot lead came out of the plug. I need to get off my ass and wire a good cord in there.

Thanks!

LBx wrote: Fri Oct 01, 2021 1:15 pm Simplify:

Recommended!

All my switches and shit are still in place, but this is exactly how my JM is wired up. Upper stuff is bypassed, only a 3way switch and a volume pot. It is correct.

Kniferide wrote: Sun Oct 03, 2021 9:26 pm

LBx wrote: Fri Oct 01, 2021 1:15 pm Simplify:

Recommended!

All my switches and shit are still in place, but this is exactly how my JM is wired up. Upper stuff is bypassed, only a 3way switch and a volume pot. It is correct.

Do you people of no tone knob also not use distortion, or use a very low powered amp? I can’t imagine the lack of a tone knob being listenable with even mild overdrive unless you’re also only using the neck pickup.

biscuitdough wrote: Sun Oct 03, 2021 11:20 pm

Kniferide wrote: Sun Oct 03, 2021 9:26 pm

LBx wrote: Fri Oct 01, 2021 1:15 pm Simplify:

Recommended!

All my switches and shit are still in place, but this is exactly how my JM is wired up. Upper stuff is bypassed, only a 3way switch and a volume pot. It is correct.

Do you people of no tone knob also not use distortion, or use a very low powered amp? I can’t imagine the lack of a tone knob being listenable with even mild overdrive unless you’re also only using the neck pickup.

Hmmm. I usually use distortions that don't add a bunch of extra high, or I use the eq on the pedal to balance it. If I feel like my tone is too bright I reach for the amp eq. I've never found a guitars tone knob useful for anything but getting 90s big muff smashing pumpkins tone, which I hate.
But to each his own.