G9 51x DIY tube mic preamp

What is the G9 51x?

G9 51x tube mic preamp

I bought a PCB for a tube mic preamp some time ago: a G9 51X. The G9 is a famous tube preamp design from Gyraf Audio in Denmark. It has been tweaked so that it fits in a single 51x module. What a feat!

The 51x format is kind of an extension from the API500 format. 2 more pins which deliver +/- 24V. You can learn more about it here: GroupDIY 51X Alliance.

The 51x format is well regarded and used on the GroupDIY forum. You can find a list of 51x projects here: list of DIY 500 and 51x projects.

Build

I closely followed the advices from the designer of the board on GroupDIY. Those were important and helped having a smooth building process.

Basically, how to solder the little lugs so that your tube will fit when you insert it (you can ignore this and take the risk to break your tube of course), fitting from the elements on the faceplate, some mods are required so that the pre works better, how to solder the high voltage converter, and so on.

The build itself is easy if you proceed carefully. Solder from the smallest to the tallest elements. 

There is a vertical diode which is not silkscreened really clearly between the 2 caps C502 and C504.

For the HV converter, I would advice to solder C503, then D501, then the inductor L501 because D501 will get on the way of C503. Well at least keep an eye on C503 because you need to solder it flush to the PCB or you'll have clearance issues.

I used the OEP transformers because I had them laying around (well and because I couldn't afford to buy expensive transformers when I have cheap ones available).

Costs

I bought the PCB+frontplate long ago. I think I paid 25-40€. The faceplate is a new one from http://frontpanels.de which explains why it's different from the original faceplate.

Tubes Westinghouse NOS: 40€

Components: 61,30€ 

I used the BOM from the first post of the thread on GroupDIY about G9 51x. It was fine even though I had to find some replacement parts because some weren't in stock.

Transformers: roughly 30€

Total cost 150-200€

Well and I bought a 51x rack from Vandaal, so it's 550€ more expensive.

Pictures

You can use those pictures as a reference because the unit is in working condition.

Yeah, power supply is working!

Hi there,
I'm pleased to announce that I managed to have the power supply for the innersonix lucidity preamp work.
As I had a bit of respect for 220V, a friend helped me wire the transformer and explained roughly how such a supply is working. After that I got power but the 3,3V was missing and the LED wasn't working. After a message to Alex from Innersonix he told me I should cut pin 7 from one of the regulator. It was written in the groupdiy forums but I somehow missed it ( or forgot about it). so I cut the pin and it worked...

I just need to wire everything now and let you know

Short update

Hi there,
yes i'm alive!
And I just ordered some more components in order to continue the lucidity pres and start the Alice mics
Stay tuned, I hope I can give you all some news soon

Delay delay

Hi all, i'm suite busy those days, so I have no updates for y ou ait thé moment. I'm drawing the case using Draftsight and have it produced by a relative.
I hope to be able to update soon.

Lucidity, what's not in the BOM

Edit: after getting the components here, I'm not entirely happy with all of them. The jack are cheap (I'll choose Neutrik next time), and some wire connectors don't fit. Please check and double check before using those. I'll update this list soon

Ok, so I'm a real beginner when it comes to DIY audio. I can buy what I'm told to buy, but there are a few things that I don't think about, so here is a list of what I needed to order that was not in the BOM
Tools:
Those I had at least
Soldering iron (or soldering station)
Solder (I used good silver solder for the pres, and normal lead-free solder for the front panel and the PSU).
Things to bend and cut wires

Components:
it helps to have some ribbon cable in order to wire the pres and the front panel: Here it is
And some "plugs" for those cables: here and here, it's matching the 2x5P headers from the pres (Thanks i3j0rn from GroupDIY). Those are for the 3,96 x6 (power) & x3 (output)
I also bought this wire to connect the output signal. Talking about output signal, I decided to use 6,35mm jack as it takes less room on the backplate.

I nearly forgot the toroid transformer...


Alex from Innersonix advises to thermo-isolate the regulators (TO220) from the PSU with this kind of stuff.

I also needed a switch to turn the preamp on and off. I got this one.

Wire:
I obviously needed wires to connect everything. I already talked about the ribbon cable to control the pres.
I used some cables from an electric plug that I stripped bare. Using a drilling machine, I made this :

I obviously need a case and some front and back panel drilling. Don't know yet what to do, I'll probably go the modushop way.

Innersonix Lucidity, first steps

The lucidity PCBs

I start populating

Soo, I got everything I need so far, at least enough to start. I checked every component for its value. Took care to match (as much as I could) the resistors R1 & R2, R4 & R5, R7 & R8, and R9 & R10, to improve common mode rejection ratio (CMRR). So far so good, it seems quite easy.
I started with the resistors, then added those small yellow capacitors. That way, I don't have to think about polarity yet and they are all small components, the board is still easy to manipulate.

I added the diodes, I needed to take care of polarity, don't want to burn everything... After the diodes, I looked at what components had a low profile and decided to solder the adapters for the chips.
I soldered then the red capacitors. BTW, in the original BOM,  C20 and C21 are rated
180pF and in the mouser BOM, they are 150pF. The innersonix team said it's not a problem, and they used the 150pF.

After the red WIMA capacitors, I soldered the relays and the resistors which are to be soldered straight (hard to get them straight). Now it starts to look like a real board, with lots of stuff on it.

Here the relays

The wima capacitors

To be continued...

Innersonix Lucidity mic preamp

Hi there, I'm starting a 2 channels Lucidity preamp from Innersonix. It should be a really clean, great sounding pre. As I mainly record traditionnal acoustic  instruments (voice, violin, hurdy-gurdy, french/irish bagpipes etc.) it should be perfect for my needs.
I'm entirely new to audio DIY, I just have a soldering station, and that's all...

Why DIY?
Well, mainly because I'm curious, because Lucidity is much cheaper to the pres it compares with (Millenia for example)

A few words about the costs:
PCB + THATDip adaptor + THAT Chips (2 channels, PSU, Front panel) 180€ (with VAT)

PSU Components 29,20€
Front panel components 15,66€
Preamp components 29,67€ *2

Total: 254,53 for the electronic.

More later (with pictures and build steps)