Premier Rock Forum

Garth wrote: Fri Oct 22, 2021 7:40 am

VaticanShotglass wrote: Thu Oct 21, 2021 11:21 pm That looks cool. What is it?

Also curious and don't mind doing a little guessing. They look a little more interesting than just a standard tube pre-amp.
That top one uses a tube I don't recognize and can't make out because of the reflection.
Bottom one looks setup to take an IEC so I guess that's what that (rather serious-looking) transformer is for?

Correct except they arent that much more, or more interesting, than a standard tube pre-amp.

#1 is an Ampeg B-15N style preamp built for all around homie and FM Major (maybe he's a previous FM? Not sure if he made the jump). It uses a creative gimmick for the power supply where it is powered by a 12VAC external source. Filaments of a standard 12AX7 type tube can be heated directly from the source voltage, and then a small internal transformer (the blue thing) steps that up to high voltage for the tube plates. The Ampeg uses a 6SL7 preamp tube which needs 6V filament voltage so i used a 12SL7 which is identical but made for 12V filaments. Controls are Volume, Bass, Treble.



#2 is a pretty simple EF86 preamp. An acquaintance who was/is guitar-teching* for a number of bands asked me if I could make a small tube preamp just to juice up a stale signal. So that's really all it is. An EF86 gain stage with volume control and switchable bright cap. I eschewed the odd power trick and just went with a standard 120VAC input using a pretty standard transformer. Its overkill in terms of size, but probably the best fit I could find at the time.



*Turns out the act he was teching for at the time was Bruno Mars, and he wound up buying two of these, either for Bruno himself or his guitar player, who was Phred Brown at the time. When I was done with the initial unit I tried shipping it to the tech, but he said he was gonna be in NYC soon and asked if I could deliver it. So I got to deliver it to the Apollo theater and got to actually stand on the stage of that place, which was really cool. I forgot to touch the stump, though.

Alright...off to go watch Dune.

Dr Tony Balls wrote: Fri Oct 22, 2021 9:44 am #1 is an Ampeg B-15N style preamp

I would love one of these.

Kniferide wrote: Fri Oct 22, 2021 2:32 pm

Dr Tony Balls wrote: Fri Oct 22, 2021 9:44 am #1 is an Ampeg B-15N style preamp

I would love one of these.

Yeah, I was thinking the same thing, although I'm not experienced enough w/ these amps to know where the magic happens. I just know that they sound perfect - in the way a P-bass sounds like like the benchmark then the portaflex is part of that equation.

Photo looks like there's also a balanced output? Drool.

Both of those units are rad and I imagine pretty useful.

The digging up of those old builds wound up with a new Pentode Boost build for FM Airloom.

What's the advantage of mounting the tube socket and associated components in that daughter box, rather than, say, on a piece of angle stock in the main enclosure? Do you find that the shielding is better?

Nate Dort wrote: Mon Nov 01, 2021 11:32 am What's the advantage of mounting the tube socket and associated components in that daughter box, rather than, say, on a piece of angle stock in the main enclosure? Do you find that the shielding is better?

Zero advantage, its just a pretty easy way of doing it, at least for me. I could make a bracket out of angle stock, but it'd be some extra work and I'd have to have someplace to store the remaining angle stock when done. I do everything in one room of a 2br apartment, so I try to keep the excess materials down. The only exception to that is the wood-shop i'm graciously allowed to use to build amp cabs, but they dont really need me storing excess stuff there. If I was building 20 of these, maybe i'd fab some brackets, but i'm not.

But also I think it looks decently slick.

Ha. they arent that close and at the end of the day its an EF86....not a lot of heat put out. The box would probably get warmer from sitting on a hot amp than from running that tube.

I am now a proud owner of a Beluga Fuzz and a Pentode booster.
HOLY COW ARE THEY COOL YOU GUYS.
Pentode will be in heavy rotation at the studio with all of these DI synth and strat assholes.

I would really like to see the side with all the sodering too in these posts.