DU67 Tube Microphone

DU67 Tube Microphone

M ai n PCB. Don't instal the following parts yet: R1 5,R1 3,R9,R1 2,C7,C4,C2 and C1 7 **** Don 't u se th e h ol es m aked i n red Start By I nstalling the parts that are shown to the left. I like to stuff all the parts, bending the lead s on the bottom such that they are not overlapping other traces to avoid any brid ging. Cl i p al l of th e l ead s of th e i n stal l ed parts, th en sol d er.

The next few parts will be installed so that the High Z (impedance) is built in the air. This will ensure a low noise build. I n stal l C7 Leave th e top l ead strai g h t an d u n -sol d ered I n stal l C4 Leave th e top l ead strai g h t an d u n -sol d ered

I n stal l C2 Leave th e top l ead strai g h t an d u n soldered I n stal l R1 5 Leave th e top l ead strai g h t an d u n sol d ered

Ben d th e lead of R13 Tri m th e lead of R1 3. Do th i s to both si d es.

Sol d er R1 3 to C4 an d R1 5 Install R9 in the hole with the circle arou nd it then solder. Bend the lead towards C7

Form a Hook on R9 Hook the one end of R9 to the end of C7 and solder.

Do the same for R1 2 an d sol der the hooked end to C4

Use the drawing below to install tube socket parts. The silkscreen may confuse you. Notice that the colors match the colors on the schematic on the following page.

I n stal l th e insulated tu rrets by pressi n g th em i n to th e h ol e circled i n red

When installing th e parts on th e top si d e of th e Tube Socket PCB, be sure to l eave en ou g h room (¼ or 6mm ) to solder the tube socket. *** N ote: Tu be socket sh own for reference on l y. Don t in stal l tu be socket yet. I n stal l C8 an d R1 clip the leads and solder

Prepare R2 by form i n g a h ook on one en d. Leave The Other en d l on g Solder th e hook to th e Turret as shown

Prepare C1 Leave the other end long. This will get connected to the Tube socket Install R1 6 but leave one end long. This long lead is coded red on the schematic

Prepare R8 by forming a loop on one end around the other turret. Leave the other end long. If you plan on cleaning off the flux, don't install C1 0 (styroflex) cap until after clean ing the flux off is done I n stal l tu be socket an d sol d er

Form a 90 d eg re an g l e of C1 toward s the grid pi n Bend th e lead down towards the tube socket pi n

Cl i p the lead of C1 and solder to the tube socket pin

Form a 90 degree angle of R8 towards the grid pin. Form a hook. trim and solder

BLU E RED YELLOW

RED BLU E YELLOW BLU E RED GREEN YELLOW GREEN

I n sert th e Tu be Socket PCB i n to th e sl ot on th e main PCB Sol d er on e set of pad s su ch th at th e two PCBs form a ri g h t an g l e. ****Don't try to "bend" the angle without reflowing the solder joint. Now solder th e two remaining joints circled i n red

Form a 90 d eg re an g l e with R2 toward s C4 (yellow n et) Form a hook. trim and solder

Form a 90 d eg re an g l e of C2 toward s th e Backpl ate tu rret. Form a hook around the Backplate tu rret (g reen n et) Tri m an d sol d er

Con n ect C7 (bl u e n et) an d R8 by form i n g inter connecting h ooks. Trim an d sol d er. Form a ri g h t an g l e wi th th e l on g l ead of R1 6 toward s R1 5. J oi n R1 5 an d R16 (red n et) by form i n g i n tercon n ecti n g h ooks. Tri m an d sol d er.

Solder To Link HZ Bridge Reference

Install C10 Solder from top Pad on tube Socket PCB and then to grid turret

Find the three position switch and install in the "PAT position and solder. Take care to solder the Switches so they are flush to the PCB and aligned to the silkscreen I n stal l th e rem ai n g swi tch es (two posi \tion ) an d sol d er. Test fi t th e switch PCB i n th e assembled m i c bod y. M ake su re th e pattern switch i n not obstructed by th e m i c bod y

Sol d er si x d i fferen t col ored wi res as sh own. (abou t 3 i n ch es l on g ) Solder the rear diaphragm wire to the other side.

REFERENCE PAD SWI TCH REAR CAPSU LE M ODI FI ED RAI L LOW CU T SWI TCH COM PON EN T SI DE OF PCB PATTERN SWI TCH FRON T CAPSU LE

Backplate Back

Feed th e rear capsule wi re through the si n g l e one of th e center h ol es. Attach switch PCB With the 3 screws and standoffs. Install m ai n m i c PCBs i n to m i c bod y on th e Same side of th e rai l th at h as been modified to fit AM I T67 tran sform er.

Feed the backplate wire from the Switch PCB and tri m to length. Leave some slack. Strip the en d, tin with solder, an d form a hook.

Solder Backplate wire to the insulated turret. Feed th e PAD wi re from th e Swi tch PCB an d tri m to l en g th. Leave som e sl ack. Stri p th e en d, ti n wi th sol d er, an d i n stal l, an d sol d er to PCB

Trim the Low Cut wires to length. Strip the ends back, tin with solder. Solder to two pin header labeled "LC" Trim the Omni wire from the "PAT" switch to length. Form a hook and install to the Front diaphragm turret.

Tri m th e Bl u e Fi g u re 8 wi re to l en g th. Stri p th e en d s back, tin wi th sol d er. I n stal l an d sol d er to the h ol e ci rcl ed i n red bel ow.

Cu t two m ore wi res to abou t 2-3 i n ch es l on g. Sol der one to th e Front d i aph ram capsule tu rret an d ru n u p th rou g h the capsule m ou n ti n g base. Do th i s th e same for th e backplate wi re an d rear capsule wi re. Carefu l l y I n stal l th e capsu l e. Cover the d i aph ram to protect it from th e sol d eri n g process. H eat an d fl u x can ru i n a capsu l e. Th i s i s very important. Now Careful l y sol d er th e three wires to th e capsu l e.

Remove the 7 pin XLR connector from the bottom of the mic body by turning the screw clockwise. You may have to push it out from the inside of the mic. You can cut a section from your tube mic cable for the internal wiring. Teflon insulation wire is better because the insulation won' t melt when soldering. Use this wiring chart for XLR pin-out. to tube mic. Cut about 3 inches of wire. Strip, tin and solder to Male XLR connector.

It should look similar to this after soldering. I t's a g ood i d ea to h eatsh ri n k th e wi res.

The AMI T67 transformer is a tad too big for the mic rails. Remove the head basket. Remove the bottom four screws to remove the XLR/ shock mount base. Use your favorite tool (My favorite is a 4 Inch angle grinder) or Dremel to grind away part of the rail. Test fit the T67 transformer and PCB to the Mic rails. Make sure there is clearance between the laminations and the rails.

Install the T67 transformer to the adapter PCB. Be sure to align the black mark on the transformer to the marking circled in red on the PCB.

Verify that the black making on the transformer and the marking on the PCB are located inside the red circle. Solder the transformer to the PCB. Screw the transformer PCB to the rails. Feed the wires between the transformer and PCB as shown. Attach the base to the rails with the four screws.

Trim and Solder the XLR wires to the Mic PCB

Sol d er wires as sh own ~2 i n ch es l on g to th e tran sform er PCB. Solder "1 " on the transf. PCB to "T44" on Main PCB Solder "7" to "T1 01 0" Solder "5" to "T1 21 2" Solder "1 2" to "T55" Solder "1 0" to "T77" Sol d er "4" to "T1 1 "

Now you should have eveyth ing soldered on the PSU and the Mic. En su re th at th e m i c i s u n pl u g g ed from th e PSU. Appl y power to th e PSU. Ch eck vol tag es at th e AC i n pu t of th e PSU PCB. 20VAC for th e h eater ~270VAC at th e H T i n pu t N ow Ch eck DC vol tag es. Unloaded, my mic meau sres -1 6VDC at H- and 250VDC at B+ If your Voltages check out, power down the PSU, plug in the Mic Do not install the tube. Turn on the PSU. Check Voltages at H- B+ on the mic. Use the screw mounting holes as Gnd ref. Voltages should be very close to the read ings at the PSU. Verify that there is less than one ohm between the mic body and the chassis of the PSU Turn off the PSU. turn down the pots on the PSU to the highest resistance settings. Install the EF86 tube (you can use a cheap one for setting voltages. Be carefu ll to not disturb the wiring at n ear the

Check the voltages at the mic with the tube installed and the PSU turned on. The voltage will start high and drop as the tube warms up. Ch eck th e B+ Vol tag e. I t sh ou l d be j u st u n d er 21 0VDC Check the H- Voltage. It should be arou nd -6.3V (negative) I t's a g ood i d ea to be u n d er vol tag e by a few vol ts. Let the tube warm u p for about 20 minutes N ow ad j u st th e vol tag es u si n g th e pots i n th e PSU. Ad just Rtrim H - until you reach -6. 3VDC Ad j u st Rtri m Pl ate u n ti l B+ read s 21 0VDC Con ti n u e to m on i tor th e vol tag es an d peri od i cl y sm el l th e el ectron i cs for an yth i n g th at sm el l s. Don 't l et th e m ag i c sm oke out! Power off th e m i c. In stall th e bod y Power on the mic and check the LC, Pad, and pattern switches by listen ing through a mic preamp and headphones as you toggle the switches. You should now be pleasantly suprised with the great sound of your voice through a tube mic, Enjoy!