Volume pot on mic, balanced or unbalanced - how?

[Guitarist]

I've a friend coming over later. He plays steel drum and is set on me making him a passive volume pot for his '57. We could go unbalanced but might be better to stay balanced. I have a couple higher K pots but other ideas might work better. It's for live use and most of the XLR inputs are taken up so he's hinting at 1/4.

Ideas:
A low Ω pot across + and - so going for out of phase cancellation, kinda like a Trainwreck MV after the PI?
Adding a cap + 1kΩ resistor thereby protecting the phantom power?
Modify a mic - transformer - 1/4 out, barrel adapter.

[The Dude]

A '57 steel drum?

[Guitarist]

Ha, it may be but a Shure '57 mic!

[The Dude]

Here's how Shure does the 520DX with volume control.



You're going to want to shut off phantom power on that channel, or turning the volume control will create noise. I don't think you'll get enough gain out of any 1/4" input on a modern mixer. Most are not mic level inputs. Another option would be making the device active for 1/4" inputs.

[Leo_Gnardo]

Why why why why why .... whyyyyyyyyyyyy?

OK there are some mics meant for harmonica players that have built in volume controls, unbalanced, intended for a 10 - 15 foot run to an amp. You know, the kind that Mississippi saxophone players like. Typically a guitar combo, sometimes a specially built "harp" amp. Whatever. That doesn't inform us much here.

I could see solution #1, gradually shorting the + to the - side of the balanced line. Why have phantom on it? Only if it's being plugged into one of those cheap mixers that has a phantom-to-all-inputs switch. Feh, I don't like them. Leave the phantom off. Anyway, it shouldn't hurt your phantom power anyway but why take chances, right?

Another solution might be, get a couple cheap mini mic to line transformers, just the bare transformer not the mic/line adapters. Mouser has these dead cheap, I think they assigned them the Xicon brand. And don't worry about their poor low frequency response specs, that's rated at full output. I've used 'em for all sorts of things and hard to tell any frequency loss unless you're ramming large signals through. They're fingertip size and you could mount a pair on a piece of perf board. So, a box maybe Hammond 1590B, size of your standard MXR pedal. XLR in > 600 ohm transformer winding > Hi impedance transformer secondary > Volume pot say 50K audio taper > second transformer hi impedance winding > second transformer low impedance winding 600 ohm > output XLR. Whew... now WHY is this necessary?

[The Dude]

This (or something like it) might be an easier solution.

https://www.fullcompass.com/prod/012...SABEgLBU_D_BwE

[Enzo]

I know the premise is passive, but really. I can buy an inexpensive tiny mixer with an XLR input for $50 or less. I can open the box and plug it in and use it. I won't have to hack into a mic or create special cords.

https://www.sweetwater.com/store/det...enyx-502-mixer

As a bonus, you get some EQ, even a pan pot. Plus a couple extra line level channels so you can play along with something. It has headphones jack, so you can listen to what the mic hears.


A number of brands make small mixers like this.

[TomCarlos]

The Harbinger L502 is at the same price point (<$50) and it even has Phantom Power. So you could use this mixer with a condenser mic if you choose.

https://www.musiciansfriend.com/pro-...xlr-mic-preamp

[J M Fahey]

I've a friend coming over later. He plays steel drum and is set on me making him a passive volume pot for his '57. We could go unbalanced but might be better to stay balanced. I have a couple higher K pots but other ideas might work better. It's for live use and most of the XLR inputs are taken up so he's hinting at 1/4.

Ideas:
A low Ω pot across + and - so going for out of phase cancellation, kinda like a Trainwreck MV after the PI?
Adding a cap + 1kΩ resistor thereby protecting the phantom power?
Modify a mic - transformer - 1/4 out, barrel adapter.

To begin with, itīs a bad idea to adjust an instrumentīs volume by attenuating (weak) microphone signal at the very beginning ... and leaving full volume noise/buzz/hum/RF/interference which appear after it, in the lon g path between it and mixer.
And as noticed above, modern mixer Jack inputs are very insensitive.

The old style microphones (and Iīm talking the 50īs) with built-in volume controls were very crude attempts at having some control when your "PA" was a Fender Tweed amp or similar, where you shared inputs (in the same channel) with a guitar ... as crude as can be.

I remember a friendīs band (late 60īs) where they played live shows using a "60W" (2 x 6L6) amplifier driving 4 cheesy 10" speakers.
2 guitars into the "effects" (tremolo) channel, vocal Mic and Bass into the other one.
There a volume control on the Mic would have been fine ... specially to avoid constant feedback squeals .

Everybody was happy when we upgraded adding a separate "Voice only" 40W Geloso amplifier, 2 x top cap EL36 or something, driving a 4 x 8" speaker column.
Everybody envied our "crystal clear PA" where you could at least understand the words being sung.
Plus we boasted using orange (dyed potato sack hemp bag) grill cloth

Notice the 520 microphone shown above already has about 10X "gain" courtesy of the step up transformer, and is meant to drive a 12AX7 or EF86 type grid, originally meant for a "crystal microphone", but a low impedance SM57 has already a weak (speaking in mV) output ... you do NOT want to attenuate that even more.

[olddawg]

Get an Art preamp.. They are on sale for $29 free shipping all of the time and are VERY versatile. You can plug virtually anything into anything. It has input and output level controls and and it can be used as a DI box too. Also very transparent.
https://www.musiciansfriend.com/pro-...oaAgZmEALw_wcB

[Guitarist]

I love hearing these stories.

Well, the gent is actually a master builder luthier it turns out. He was just here in the shop and I ended up tagging on a 3K pot across the mic and that works, surprisingly.
I tried to talk him into the mixer and even lent him a Hedway for the gig and to compare but he's anti wires at this stage. He can try both approaches and report back.
I might talk him into using a AKG C1000 with the built-in 9V battery. Then the phase-out volume control might work even better. Even a wireless mic!

So, this application will savagely work with a 2KΩ linear pot placed across pins 2 and 3. Adding a cap (to safeguard phantom power) is better.

Thanks so much for your insights.

[Guitarist]

Funny you mention that, I already called a bud for one of those and he had a Shark. But "you can lead a horse to water..."