The rack preamp continues...

[Tony]

Seen as the original thread is in the old place time to get it back up here.

Main update is I found a transformer that is both suitable and will fit in a 1u rack.

Still not decided on boost & geq but I'm leaving towards a mkiic+ style but gyrator based rather than inductive.

[JJ Rodriguez]

[Tony]

Get your baggy pants ready. More to come soon.

[James]

Beautiful work as every Tony

[JJ Rodriguez]

Get your baggy pants ready. More to come soon.

I wear sweat pants, because the world should know when I'm erect.

[zepp]

Nice.

[Mahler]

This is going to be good!

[Petrogli]

Looking forward to seeing this come to fruition.

[noodles]

[Mahler]

Look out, look out, there's more developments on this beautiful rackmount!

EDIT: A full size pic of this really makes it shine. Didn't expect it to compress so much on here lol

[Tony]

Look out, look out, there's more developments on this beautiful rackmount!

Thanks. Much appreciate your CAD & design work on this.

[zepp]

Looks fantastic and easy to use.

[JJ Rodriguez]

What's the difference between light and hard?

You can sleep with a light on, and you definitely ruined my sleep tonight.

[JJ Rodriguez]

Oh, and how many are going to be available? You think there will be enough for all interested parties?

[Leon]

EGGPLANT EMOJI

[Coop]

Very cool! I will be keeping an eye on this for sure.

[Tony]

Oh, and how many are going to be available? You think there will be enough for all interested parties?

I've got to get up into the loft to check where I put stashed the other pcbs should be 3 minimum.

I can also check with the guy who made the pcbs as he was struggling to sell them and had about 90 left last time I checked.

Worst comes to the worst its a ridiculously simple circuit and could be slapped together on some tagstrip.

I'll have to figure out the logistics etc as brexit is screwing me from every direction with fees and people that just outright won't deal with me due to the fact I'm in the UK.

Might turn out to be easier to just have a community BOM and some well written instructions & the boards sent out.

[Adam]

Where is the pcb from Tony? It if its easy enough to build I may look at putting one together myself at some point. Does the pcb maker do different preamps?

[James]

That front panel layout looks great

[Tony]

Where is the pcb from Tony? It if its easy enough to build I may look at putting one together myself at some point. Does the pcb maker do different preamps?

It's a guy called MSI on sloclone. He does all kinds of things. I think currently he's doing Vh4, mkiic+ engl fireball full amp boards & these slo lead preamp pcbs.

Fair warning though his schematics are often a bit messy and take a little figuring out.

I was going to redraw it if I can get all the kit stuff together.

Currently in discussions about getting the rack front panel laser etched vs a faceplate.

If the laser etching works out it will be great as it opens up all the anodised options.

[JJ Rodriguez]

How many tubes does this use? Assuming 2-3? If it's going to be short supply or the logistics of shipping it across the pond are too much of a pain maybe I'll just have to replace the preamp components for my next AX84 build and have a 5W SLO.

[Adam]

It's a guy called MSI on sloclone. He does all kinds of things. I think currently he's doing Vh4, mkiic+ engl fireball full amp boards & these slo lead preamp pcbs.

Ah cool, ive tried a few times to sign up there, but it never lets me sign up

im currently using the VH4 pedal for my main tone and enjoying it - i was tempated to look at making a vh4 preamp, so that could be cool if its something he can offer.

[zepp]

I guess places like oshpark or pcbway aren’t good options for this sort of thing?

[Tony]

I guess places like oshpark or pcbway aren’t good options for this sort of thing?

They would be fine but it's his board design and I don't have the gerbers

[Tony]

Tiny bit more progress. After trying every decent PCB mount noval socket I had I realised they just weren't going to play ball with all of them having pins way too chunky to fit.

So random eBay China purchase to the rescue. Got 6 sockets for £3.40 took forever to get here 3 of them were a bit mangled with the pin holes being blocked/partially blocked. Luckily 3 were fine and fit like a glove.

Not done the large electrolytic caps yet due to being undecided about how I'm going to mount the board. It's designed to screw onto the front panel behind the pots with 40mm standoffs but that leaves me with 6 screws jutting out in random spots from the front.

I'm thinking of getting some 37x37mm aluminium angle brackets and mounting further back keeping the front panel clean and also giving me more space to do the final wiring which I aren't looking forward to. If i do this I can keep them on the component side of the board which also increases the safety factor not having electros with 300v hanging around when trying to change valves.

Did some continuity testing from the pins to the solder joints and everything is decent. Just need to clean up the back of the board now and wait on the rack enclosure.

Also minor updates regarding the boost & GEQ
Boost is going to be based on the Fuzz Dog Candyman Overdrive - Drive, Level, Bass Cut, Treble Cut controls.

GEQ i'm going to do based on the TH Custom 5 Band EQ board because the one I was planning on using from Australia the Rock Bottom EQ they won't ship anything to the UK post Brexit - 79hz, 235hz, 728hz, 2.1khz, 6khz. These are a bit off from the front panel design but the closest I could get them with real part values including using parallel caps for the 6.6k but they're still way closer than the actual mk series frequencies!