Vacuum Tube Guitar Amplifiers – Part III

The tough part about doing anything with this much detail, the first time, is that every time I thought I had every part listed in the bill of materials, I found a few more parts that I needed but are not on the list.  The BOM Im listing below is most of what I need, short of a few hardware items and tools.

Resistor BOM

 

The following is a complete (I hope) list of resistors, with the component value on the left in Ohms, a note as to where it is in the circuit, if needed, and quantity.

I don’t know yet how to edit a table in WordPress, will fix up the table with headers at some point. All resistors not marked are 1/2 watt, metal film, with 350v/500v peak ratings.  The higher wattage resistors are at the bottom of the list.  I am going to use higher wattage value resistors in the “power rail”, than were specified on the original schematic.

 

47 End of LTP 1
470 1
820 Feedback 2
1500 3
2700 1
6800 2
10k 1
22k long tail pair 1
27k
68k 4
100k 10
220k 4
1m 6
2.2m 1
10m 1
10K 1 WATT 1
27K 1 WATT 1
82K 1 WATT 1
100k 1 WATT 1
470 3 WATT 3

 

Since these are mostly very inexpensive components,  around 15 cents each and up, I will order a few  more than I need for this amp build since I know I will be building another amp and most are common values.

Ordering 10 of each resistor, which will leave me with some extra,  is about $20.00 plus shipping.   I have these resistors in a web shopping card at Hoffman amps.

You can find a little cheaper resistors on bigger electronics warehouses web sites, but the pain of sifting through literally tens of thousands of parts, and not finding the exact value you want, is not worth saving a few dollars.

Resistors: cost about $20.00.

 

Capacitor BOM

This is the complete (hopefully) list of capacitors for a Fender Deluxe AB763 style amp build, less the big electrolytic filter caps.   You can find exact values for all of these capacitors.    I decided to buy Sozo Blue, pricey boutique signal caps, of which there are only 8, and the rest are as specified on a fender chassis (using photographs and blog posts).

0.00025 250pf 2 Ceramic
47 PF 1 Ceramic
0.001 1 Ceramic
0.01 2 Ceramic (tremolo)
0.02 1 Ceramic (tremolo)
0.047 3 mallory150 or Sozo
0.1 5 mallory150 or Sozo

The total cost of all capacitors, not including the big filter caps, is about $45.00, if I use pricey Sozo or similar signal caps, and about $20.00 if I use Mallory 150’s.    There is only one distributor for Sozo Blue,  Antique Electronic Supply:

Antique Electronic Supply

In addition to capacitors, they sell just about everything you would need to build a vacuum tube guitar amplifier. I have not dealt with them yet, will probably buy the signal caps and some other components.

All caps minus filter caps: about $45.00.

Filter Capactors and other electrolytics

Since electrolytics are harder to source with exact values specified in the Deluxe AB763 schematic,  I listed them separately.   As mentioned in other amp posts, I know I don’t have the electrical engineering chops to decide how far a given component can be from the design value, so I will use parts as close as I can find.

25uf 25v  Cathode cap 5
25uf 50v Bias cap 1
16uf  450v  Filter cap 5

The 16uf main filter caps are about 5.00 each total cost 25.00 + shipping.    I bought these from Amplified Parts.com  The remaining 6 24uf I bought from Mouser, more or less exact replacement axial lead 3.00 each, total cost about $43.00.

Electrolytics: about $43.00 + shipping.

Pot BOM

Even potentiometers are difficult to source.   There are literally thousands of different  styles, various shaft styles some knurled, split, solid, plastic, with varying lengths, different lead configurations.     The best I could find is that CTS makes the best potentiometer for these amplifiers,  they have the voltage ratings, are well made, but a bit pricey.    They sell for about 3.50 each, best price I could find was Amplified Parts.com.     Each channel pair has volume, bass, treble, and the tremolo input has speed and level for tremolo as well so total 8 pots, at 3.5 each, or about 28.00.

The black ‘witch hat’ knobs are about 2.5 each, so about $50.00 for pots and knobs.   I decided to put a mid pot in the reverb hole in the front panel, so total 56.00 for pots and knobs (ouch).     The only place I could find that sells CTS pots with all metal shafts, at the best price is amplified parts.com.   The other sites sell plastic shaft, no good for a music amp that gets beat around a little.

Pots and knobs:   $56.00 + shipping.

 

Total so far, about $170.00 for components, more to come

Transformers

Since I decided to go with Hamond transformers, and the prices are all fairly close,

the stock transformer, output transformer, and choke set from Mouser:

291BX power trans 89.91
194A Choke 18.49
1750H Output Trans 39.99
 Sub total 148.39
ship 22.2
 Total 170.59

 

 

 

Misc components

Everything not covered someplace else.

Tube Socket 8 pin chassis 3
Tube Socket 9 pin chassis 4
Mounting offsets for circuit boards + screws.   1″? 14
Pilot light and jewel (6.3v) 1
Lugs for grounding (think about solder point on chassis for grounding) 2
 Solder, and Flux
main eyelet board 1
filter cap eyelet board 1
bias eyelet board 1
Jack Shorting spkr 1
Jack Non shorting ext spkr 1
Jack shorting input 4
RCA jack for Tremolo Pedal 1
Switch SPST Paddle Standby 1
Switch SPST Paddle ON/OFF 1
Fuse Holder for 1 amp. 1
Fuses  1amp slo blo 5
 Braided ground wire.
AC Power Cord 1
AC Cord Strain Relief 1
 Heat Shrink Tubing.
Pack of washers for pots and jacks 20
 ‘Dog House’ cover for filter cap board.
Self Tapping screws for Tube Sockets
Screws/bolts for transformers
Hookup wire: 22ga for ckt board (at last 5 colors)
Hookup wire: 18ga for heater wiring (solid core)

That covers most of the “I know I need” small parts, from looking at the chassis photos, and schematics and layouts.

 

Chassis + face plate

As mentioned in a previous article,  about $67.00 from Zachmdhunter’s ebay store, includes shipping.  This is the “Fender Deluxe reverb AB763” chassis, although I am not building the reverb circuit.

 

Combo Cabinet – 1 x 12

I will source this from TRM Guitar Cabs.   I bought the unfinished bare bones cabinet.  The price is $190.00 which includes shipping.   I will also buy casters for about $25.00 from amplified parts, so I can roll the amp around without having to lift it.

 

Final Review

I have web carts setup at

  • Mouser – the transformers and small electrolytic caps
  • Amplified Parts.com – pots, knobs, signal caps, lamp, jewel switches, casters.
  • Hoffman amps – remaining eyelet boards, full set of resistors, diode, some of the wire tremolo opto isolator.

Already purchased:

  • TRM Guitar cabs – purchased cabinet already.
  • Zachmdhunter – chassis
  • Main eyelet board – Hoffman.

 

Only need to review the entire list again, check for errors recording part values and counts, make sure I didn’t duplicate anything, then send the orders.

 

Next on the todo list after the parts review is to look for a good soldering station, and better meter than I have now, and get some practice soldering, and make a plan for assembling and soldering the amp together.

 

 

 

 

 

 

 

 

 

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