Wish I Had… Another Preamp

Now, now, you weren’t there and didn’t hear what he heard.

Pour yourself a good stiff drink and settle down !

The question is… What’s cheaper? The crack habit or the gear habit? Unfortunately, I might suggest the crack habit!

There definitely was not some massive WOW difference, but space-filling difference on some level was definitely happening. Also, the bass note hits on the piano were definitely more real-to-life-like; bigger.

i would love to see some pictures. And also whats under the hood.
This stuff always intrigues me. Cheers

I didn’t even pull out my phone to take a picture the entire time. I’ll have to ask about taking a few pics of the inside to post on here when he brings it back over in a couple weeks; he took it with him to do a couple tweaks. He plans to come every other Tuesday night for us to play with it, until we’re confident we’re completely happy with it, so obviously we’re in no rush at all.

The plan is for stereo and supply in the same box, but right now it’s mono in a 2-rack space and a supply built into an old receiver case. Faceplate layout ergonomics and artsy designs still have to be done as well. We’re slow.

So far, a common-mode choke (if I remember correctly), small custom input transformer (don’t remember the ratio, but not 1:1, so that’s a gain-stage), adjustable pad after the transformer, tube gain-stage, pad-able (and adjustable) tube output gain-stage, (2) unity-gain tubes for impedance-matching to be able to use a 1:1 output transformer. In this case, a Jensen. At some point, I’d like to see if he can make an H-Pad work at the output too, as to not change the tone and still have reasonable levels for whatever comes after the preamp; converter or otherwise. We’ll see there. Anyhow, overall, that’s 104dB of gain! Want clean hi-fi? It’ll do that. Want a fuzz bass? It’ll do that! DI goes to the first tube gain-stage; it’s input is switchable between 100k and 1 Meg.

There’s an extremely wide-range of input impedance options... 50-30k and a lot between. Sometimes there’s quite a difference in tone, sometimes not really at all. This is done both through input transformer windings and with resistors.

There’s standard P48, P48H, and his own take on phantom. I still need to get more details on that.

John McCormack, owner of Rainbow Electronics in Sacramento, designed and built it. It started many years ago when he designed a swiss-army MicroAmp for guitar; just selling out of his repair shop. I encouraged him to clean it up to use as a mic preamp with a cheap 1/4”-XLR transformer. For a while he even advertised it in TapeOp in exchange for some repair services. From there, the idea of a mic preamp, designed from the beginning as a mic preamp started to form. He slowly designed and built it over a year. We played with for a few times over a year, then the whole thing went into hibernation for 10-years. This current version is a big redesign of the original, inspired by the fact that the custom output transformer manufacturer retired.

I did record what we did, but we were all other the place. I’ll have to make much much more organized recordings to share.

Don't forget the Great River, and its infamous Evil Fraternal Twin...

The mighty ART Tube MP PRO!
Chris

Why post about a preamp we can't see or hear unless you can post some tracks comparing. It's no fun this way.

I already have a staunch opinion on this Pre.
Even though I haven't seen or heard it!

Oops. Sorry guys.
Wrong website.
Chris