So it is what it is. I couldn't find a fully complete build photo diary, so i'm going to do my best to keep this one up all the way to the end. I'm going to skip the purchasing part, as complex as it was, instead I'll start with the preparation.

Upon arrival, I organized all of the tiny bits into marked separate bags containing resistors, capacitors, static sensitive parts, and enclosure hardware.


When the box from Hairball arrived, the enclosure was first. I did receive 8 screws fewer than i needed, so after a short trip to the hardware store i was back in business.


First into the enclosure was the external connectors; two XLR, one IEC. Followed by the power transformer and the output transformer.


More to come tomorrow.

Next came the VU meter. I used a function generator that i made a few weeks ago to send a signal through to confirm needle operation.



After I got the VU set in place, i moved to the input, output, attack, and release pots. The first bit of soldering was done to mount the input pot to its pc board.



Next up was the Meter button assembly. 3.6k and 8.2k resistors each need soldering to the surface, followed by the buttons. Make sure to attach the button assembly to it's case flange, then to the case. It is next to impossible to attach the buttons to the flange after the flange is attached to the case.

sweet. I have REV A too.. but have a problem with the Qbias. it seems not working.. will post the detail later.. any clue maybe about the Qbias?

I'm not even remotely into that territory yet. Hopefully you figure it out by the time I get to that point, but if not, I'll try to address it when I get there.

One bit of advice that I've found somewhere on the mnats or hairball sites is to measure EVERY piece and part and system with a DMM every step of the way, to be sure of continuity and correct values. It does take a bit more time, but it should prevent any slip ups from occurring. I'm sitting here about to work some more on the thing so I'll be continuously updating tonight.

Does anyone have any idea what the variance of resistor values is acceptable? I'm about to wire up my ratio switch pcb with the resistors, but the information in the chart in this pdf from Hairball conflicts with the BOM.

http://hairballaudio.com/docs/FET_Co...rd_Info_V2.pdf

The BOM I have includes mostly values from the Rev. A, but the values for R1= 120 instead of 180 (120 is lower than the 150 for Rev D,G) , R8= 68k instead of 130k (rev D,G are 68k), and R9= 47k instead of 56k (rev D,G are 47k).

Is this ok?

Here is the ratio button assembly. Had a bit of a scuffle with the resistor values and which were correct, but with a quick look at the schematic, the right values are clearly marked.

Input transformer attached to it's pcb. Black dot corresponds to pin 1 marked on the pcb.



I think now that everything that mounts to the enclosure is mounted or otherwise, its time to hit the main pcb. Onward to the power section.

Power section stuffed. Each part tested for continuity and proper value. All is good for now.

This is really cool. I have a stereo kit that has been sitting unbuilt for a while as i havent had the time for it but this thread looks like it should be very helpful!

Sent from my XOOM 2

Thanks for taking the time to post this! I'm expecting my rev A kit any day now!!!!

What is the verdict?

I compared the schematic to the BOM and as it turns out, the BOM does call for the appropriate resistor values for the switch. The chart outlining the values across the different revisions seems to be incorrect/incomplete. Though the way it looks, I think Hairball is shipping out rev. D button assemblies for the rev A kits.

The two super duper important grounds connected. Two AC leads to front panel off switch.



It is extremely important to know the proper way to wire your individual transformer- they are not all the same.

So this is somewhat unexpected. I'm working on populating the signal line amp portion of the pcb, and for caps' c8, and c10, which holes do i put the caps leads through? And are these caps polarized? There is not one lead longer than the other to identify it.

So upon ridiculously close inspection, it seems that all of the thru holes are redundant, and linked to one another horizontally.

These both are one 1uf and one 150nf poly cap and they are not polarised. It looks that the holes in a row give just a few options for caps with different space sizes between the outgoing leads which is a nice thought from the designer

Signal Line Amp is complete. Organization has been a key player in keeping my head straight through this portion of the build.



Onward to the gain reduction control amp! Meat & potatoes.

Thanks for clearing that up for me. I felt pretty sure about that being the case, but now i can rest easy. I was making efforts to get my electrical engineer friend in Philadelphia on the phone about that one ;p

Silly question but did you have to buy any wires for this build? I've ordered everything through hairball and mnats but wasn't clear on wires? Thanks and sorry but ill probably have a ton if questions for you if you don't mind in a few weeks once I start my build, just waiting in the Austrailia shipment

Not silly at all! I did buy a LOT of hook up wire. Mostly because this is NOT going to be my last build, but also because I messed up and bought the wrong stuff the first time around lol. All in all I got myself some good quality tinned 22 gauge hookup wire, some 12 gauge cable, though this has only made it to the chassis ground wire because it is a bit too large for most of the rest of the build. I scored some 18-ish gauge from an extra IEC cable (somehow I have accumulated a gazillion of them) for hooking up the IEC connector to the "off" switch. I also got some 24 gauge two-conductor shielded cable for some of the audio runs. Most of the wiring will be using the 22 gauge high quality cable I have.

Also I forgot to add... I'm kind of suprised about how few questions I'm actually needing addressed. All of the documentation I have found has answered just about all of my questions. This is my first major build ever, so I'm kind of in the same boat you are. I've got myself a first-term electrical engineering text book to read, but have not started it yet. The web has soooo much good information all within the realm of hairball and mnats' pages. Some of the info is hard to find, but it is almost all there.

This is my form of organizing these numerous tiny things. A piece of tape sticky side up helps manage the resistors. Makes for easy testing of these components too.

Thank you! Do you think if I just got a couple feet of 22 gauge I should be good?

All done with the gain reduction control amp, minus the transistors. Need to figure out how to measure the hfe value.

Does anyone know how to measure this with a 'standard' DMM?

I got the part number 2N3708 transistors which mnats site says are 'selected for high beta'. If anyone can explain briefly what that means and why it matters that would be great ;p


Micah421: you'll need more than a few feet to complete the build, and it should be of the highest quality per the outline again on mnats' site. The sparkfun wire dispenser in the image is what i went with. It has multiple colors to aid in keeping organized. So far I've not had to create additional wiring, but only because I decided early on to not run any wires that go from chassis to pcb until the pcb is completely ready to be connected.

You can see in the other image the shielding and tinning on the hook up wire. It's good stuff. Only like 16 bucks for the box of 6 colors, 25 ft each.

Thank you! I just ordered the Sparkfun wire dispenser!

Gain reduction meter section stuffed. Be sure with the revision A trimmer pot's to mount them in the 90 degrees position. All is well, moving on to the preamp!

All done! Capacitor C22 was a little weird. The posts on the cap were set wider than the thru-holes for them. Had to squeeze them in a bit and solder without much if any post actually through the hole. A bit awkward, and kind of felt like I broke the cap. So we'll see what happens when i power it up.

So i measured the resistance on C22 and found that it is indeed passing signal, so i think i'm safe.

Here we are pcb mounted to the standoffs. Ready to start the input.

Here is the input wiring, completed. Wiring the ground around the transformer was quite an adventure. More so was the cable i fashioned for leading from the transformer to the pcb.

Glad to be done with this step.