Kalamazoo Model 1 Revision: 1 Tube Amp Data Repository Bill of Materials / 22 May 1999 Item Quantity Reference Part 1 2 C1, C3 .01uF/400V electrolytic 2 1 C2 .0047/400V Orange Drop 3 1 C4 10uF/10uF/20uF/350V min. (450V recommended) electrolytic (2) 4 1 C5 .022/600V electrolytic 5 2 R1, R2 47K 1/2W (1) 6 2 R3, R7 2.2K 1/2W (1) 7 3 R4, R8, R11 100K 1/2W (1) 8 2 R5, R6 1M Audio taper 9 1 R9 330K 1/2W (1) 10 1 R10 150 1W (1) 11 1 R12 1K 1/2W (1) 12 1 V1 12AX7A high-mu, dual triode (3) 13 1 V2 6BQ5 Power amp pentode (4) 14 (el84) 1 V3 6X4 Full wave rectifier (5) 15 1 T1 Power transformer, 250-0-250V@40mA, 6.3V@1.5A (6) 16 1 T2 Output transformer, 5 watt min., Pri: 4K, Sec: 8 17 2 @1, @2 9 pin miniature tube socket 18 1 @3 7 pin miniature tube socket 19 1 J1 1/4" mono phone plug with switch 20 1 J2 1/4" mono phone plug 21 1 S1 Switch, SPST, 125V 1A (7) 22 1 DS1 117V neon pilot lamp assembly 23 1 F1 Fuse, 250V 1A 24 2 TS1, TS2 Terminal strip, 2 lug no ground 25 1 P1 Power cord (8) Notes: 1.All fixed resistors are carbon composition 2.May be replaced with separate electrolytics, somewhat larger values acceptable (such as 20/30/40) 3.Lower gain tubes not recommended 4.or EL84 5.or 6063 or 6X6GT 6.specs derived from observed voltages, tube manual 7.original was piggybacked to tone control 8.original was 2 conductor, 3 conductor recommended polyester foil tubular caps as having the best "vintage" sound, since the original, paper caps are no longer available. If possible multi-tap transformer MODIFICATION Easy line out jack ------------------ A small amp like this can make a great overdrive effect for another amp. It's not a good idea to run the speaker output directly into the input of another amp. (It's really bad for the output transformer.) Fortunately, adding a line out isn't very hard. You will need: a 1/4" phone jack (like your guitar cable plugs into) a foot or so of two-conductor speaker cable a 100 or 390 ohm, 1/2 watt resistor and a 2.2k, 1/2 watt resistor or a 470 ohm, 1/2 watt resistor and a 47k, 1/2 watt resistor ( Gerald Weber suggests in one of his books a 2.2k/100 pair of resistors for an old Fender, and later a 2.2k/400 pair for another old Fender. A couple of Gibson amps from the Kalamazoo era use the 47k/470 pair, and I plan to try that first.) Anything in the neighborhood of these resistor values should work. And keep the speaker plugged in! Connect the speaker cable in parallel with the speaker. You can run the wires off the speaker or splice them into the speaker cable. I'd suggest using spade clips, which just slip right onto the extra set of ears on the speaker terminals. Connect one wire to one end of the 2.2k resistor. Solder the other end of this resistor, and one end of the 390 ohm resistor, to the phone jack's tip lug. Solder the other end of the 390 ohm resistor and the other wire to the phone jack's ring lug. It's ready. Mount the jack in your chosen location, and you're set. NOTE: This is not a pre-amp out! It's a quick and dirty hack taken off the speaker outputs. As such it will not be as good an impedance match, or as clean, as a real line out. But it works. But keep the speaker plugged in! Otherwise, you may well fry your output transformer or the 6BQ5! Run the preamp filaments on regulated DC, not AC, starting with the input tubes Rewire the grounding so the amp is star grounded, and does not use the chassis as a ground bus Use coax cable in the signal path, at least in the early sections where noise counts the most. Tie one end of the shield to ground and terminate the other end with some shrink tube so it cannot touch anything. This way the coax shield acts as an antenna and conducts the RF to ground (as well as Faraday shielding hum out). If you tie both ends to ground you set up some capacitance (and the possibility of ground loops) you're better off without. The shield should be tied to the star ground point individually, and bypassed to the chassis locally with a good RF cap of about 0.001 to 0.01. Try a 240vac fan running from the 120 vac line supply, which will run much slower and quieter than a 120vac one. For the adventurous, add a separate filament transformer/rectifier/ filter capacitor to make 9-12VDC at several amps and then use a three terminal rectifier to regulate this down to 6.3VDC, and feed this to your preamp tube filaments. Hum from filaments will drop right through the floor. Gerald Weber advocates using a 270K/27K resistor divider from B+ to raise the filament windings in a DC sense above ground. This keeps electrons from the filament from hitting the plate, another source of hum. "choke". Inductors look like small transformers, but only have two connecting wires. Inductors store energy in the form of a magnetic field. When current flows through the windings in the inductor, energy is stored in the magnetic field. When the amount of current coming in through the windings drops, the magnetic field collapses and produces current in the wires, hopefully long enough to maintain a constant level of current. In reality, the current produced by the collapse isn't enough to completely smooth out the pulsing. ------------- inductor ---------| |-------------->|-------- | | \ ===== | transformer |----- to ground ------OOOOO--> to ground | | / ---------| |-------------->|-------- -------------