A DIY 1/2 Rack Bass Preamp

[Passinwind]

I should have known! I love those powercons. I've never used one in an amp. I've seen them in lighting applications.

My SpeakerPower amp has a Powercon pass-through that has a right angle IEC connector on one end and mates with various preamps I rack with the amp. I might add that feature if/when I get a back panel made for the amp. Powercons make custom line cord sizing a breeze.

 

[beans-on-toast]

Very nice. I like that it locks. For a few extra dollars, all amps should be built that way.

 

[juledude]

During test fitting of the new front panel a few new rabbit holes appeared due to slightly different control placements. Metalworking is really not my forte, but I got it done OK and all the filing and grinding is invisible once everything is assembled. Need different trim washers for the switches too, but that's nothing too tragic. Edit: now sorted.

So I've had the preamp/power amp rig out at two open mikes so far, with very good results on both EUB and fretless slab. It'll be interesting to see how the preamp works with passive basses now that I've installed a 330K ohm input option.

Geez! That is beautiful. Congratulations.

I share your pain with the metal work. KC Sheet Metal does all my work very well, but I have difficulty describing what I want some of the time.

This really is beautiful.

 

[Passinwind]

Rather than do a whole new thread, here's this year's all-in-one version, with slightly revised circuit boards and a different set of opamp choices just because I can. Dimensions are 12" x 9.75" x 3.3", weight is 8.8 pounds. The enclosure is a fully custom all aluminum job from Protocase in Canada, w/ welded seams, powder coated finish and digitally printed graphics. Good times!

 

[rufus.K]

I want one.
Don't need it, maybe can't afford it, but I want it.

 

[BadExample]

And on to some cosmetic detailing. New front panel for power amp module:

I've played out with this mini stack quite a few times over the last few months and everything seems to work just as expected. I found a decent hard case for the preamp on eBay and a great laptop bag at the Salvation Army that holds the power amp perfectly, plus cables, tuner, etc. in other compartments. Maybe a slightly less convenient schlep in some ways than a rack case, but I'm still at a very easy two trip load in or out, as good as it's ever likely to get for me really.

Beautiful, inside and out!

 

[OldogNewTrick]

Just soooo awsome !

 

[javableak]

Very good job, interesting.

 

[A9X]

Just found this thread from your onboard preamp one. Very impressive work. Your pre, as well as Rod Elliott's bass amp idea have inspired me to go ahead with a similar-ish 1RU pre, as sort of amalgam of both your designs and a PSU for the bass onboard pre. I have a near new Yamaha PX5 to power a biamp rig.

Some interesting things happened in the decade I was away.

 

[Passinwind]

Just found this thread from your onboard preamp one. Very impressive work. Your pre, as well as Rod Elliott's bass amp idea have inspired me to go ahead with a similar-ish 1RU pre, as sort of amalgam of both your designs and a PSU for the bass onboard pre. I have a near new Yamaha PX5 to power a biamp rig.

Some interesting things happened in the decade I was away.

Rod's bass amp has some some great features, wish it had been posted back when I was developing my early rack preamps.

As far as outboard power for basses, perhaps you saw this one of mine in the other thread?

 

[A9X]

Rod's bass amp has some some great features, wish it had been posted back when I was developing my early rack preamps.

It's very well thought out, and typically for RE he actually gets the details correct as the 1H/2H relationship and LF extension required for the cab and how it sounds is very important. The rest is very well thought out too.

I just wish he'd made PCBs for all the subsections. If I have time in the near future, I'll make some up, but I'm well out of practice on PCB design.

As far as outboard power for basses, perhaps you saw this one of mine in the other thread?

No, I didn't. I'm glad to see I'm not the only one interested in this rabbit hole. I'll flesh out the details of how I want to use your onboard LPFs and post it in the other thread later, but just as battery powered. I'll re-read the thread again as I scanned it quite quickly and was recovering from a monster hangover yesterday and most likely missed a lot.

 

[MarkA]

Cool beans. Perhaps one of these days I'll get to try one of Charlie's designs. Whether this happens before or after I learn to solder semi-properly remains (as do many things) to be seen.

 

[Passinwind]

Cool beans. Perhaps one of these days I'll get to try one of Charlie's designs. Whether this happens before or after I learn to solder semi-properly remains (as do many things) to be seen.

Heh, you'll get to that if and when it's important to you, I'm sure. I'm down the SMT rabbit hole these days and mostly doing onboard preamps at the moment.

FWIW, I recently got the 1/2 rack format pieces back from the third owner in trade for an older DIY rack preamp/amp build. Both owners eventually decided they preferred an all in one format as seen in post #64, and my spare one made the rounds to both of them, and even ended up in a friend's busy NAMM booth a few years ago. Goofy, since I have no intention of making any more or ever selling Class D bass amps. And then this year my luthier friend decided he wanted to use an even older DIY build of mine in his booth, so I managed to trade back for my favorite DIY build I've yet done. The older one was based on one of Rod Elliot's projects, with a Fender-based tone stack, a much simpler and more slap friendly vibe, and more power. I'd still recommend Rod's Project 27 as a great entree to DIY preamp building, FWIW. I tarted the original design up a bit but Rod has addressed some of the same territory in his revisions over the years.