Dc30 guitar microphone pre amp

[mus1k_freak]

This is what happens when i get bored and have some free time, something i thought some of you might find interesting. I build alot of weird guitar effects boxes, pedals, along with lots of studio gear im always tinkering with something, this started out as a matchless DC30 preamp stage in a guitar pedal, 300v transformer, ef86 tube etc. sounded pretty cool was running it into a serial effects line return of a marshall jtm60. Anyway got bored with it and had some spare parts laying around so i wired in a cinemag cm2480 backwards as a mic input transformer and have just a capacitor output. The only mic i had laying around was a sm57 next to me so i ran some acoustic guitar to it just see how it would sound, not to bad! im sure if i tweaked the circuit from guitar preamp oriented a little more towards mic pre amp i could get some nice sounds out of it, this was pretty much all spare parts. since a picture is a thousand words here is some pictures and 2 sound samples of it. The first one is dry, just the unprocessed acoustic, the second has a little compression and reverb and eq on it, see what ya think would love to hear some feedback!

unprocessed file  https://soundcloud.com/mike-cantilina/dry

processed file https://soundcloud.com/mike-cantilina/wet

 

[joaquins]

Nice one! and just adding a tx to a guitar pre, little mods and a dedicated tx and it should beat many preamps, in fact you could find some nice uses as it is I think...

I'd bad experience with EH tubes, way better ones with JJ... how they turn out to you? seen you have both around...

JS

 

[mus1k_freak]

Thanks gonna do some more testing tonight record some electric maybe use it on a snare etc see how it does pretty neat! The EH tube was very microphonic so I picked up a JJ unfortunately it's not to much better but from what  hear ef86 tubes are hard to get good ones.  Normally I'm a big fan of JJ tubes for for the price you can't beat them!

 

[critterkllr]

For EF86, you really need to get tested NOS. They're all slightly microphonic, but some are better than others. Mike at KCA has some NOS Tesla EF86s that perform great. I have Mullard, Amperex Bugle Boy, Dario Miniwatt and a few others. The Tesla hangs just fine with the rest and is a quarter of the price.

You could also try grabbing some #14 o-rings from the plumbing section of your local hardware store. These can help tame the glass a little, but won't deal with internal vibrations.

 

[mus1k_freak]

Thanks for the heads up never heard of Kca,  if I end up keeping this as a mic pre I'll pick up a Tesla tube seems like a pretty nice collection he has! Why are ef86 so expensive bummer.  I'm gonna try and run this into a 12au7 buffer to get the impedance closer to where it needs to be as well. 

 

[joaquins]

EF86 has some trouble with it, true, but I've got problems (microphonics) with a couple 12A-7 EH tubes... that's not so common...

One guru here that builds guitar amps decided to not used any more in his AC-like amps because of this, but he also told me that when he get an amp with one of this inside because the owner complains about microphonics but loves the sound (I do love the sound of mine) he damped it in two ways, one is as critterkllr said and the other is to get the socket and hang it on some rubber too, maybe with some other piece in the middle, so it doesn't get directly the vibration from the chasis, but a damper in the middle. I did this with an amp with this problem (not a EF but really high gain with a couple of 12AX7) and any tube I tryed solved the issue, then, I did this and helped, the microphonics get filtered as a LPF but still HF is where the problem is more anoying and get feedback because being over the guitar cab.

JS