First tube amp build: Fender Deluxe AB763 style amp (no reverb).

[mikepukmel]

Fender-Deluxe-AB763-Schematic.pdf

I chose this style amp, since its 22 watts, I can use it for practice at reasonable volumes, and if I crank it up so that it starts to clip, it won't be way too loud, like a Twin. Also, its a reasonably simple circuit, esp without the reverb, compared to the newer, bigger amps, and all of the components seem to be available. Also, its still fairly flexible, the chassis could be put into a head style cabinet, or a combo cab, and its able to push 2 x 12's.

Some background: Im a software engineer, I don't have any electrical engineering background, but I have picked up a little over the years. One of my goals is to learn more of the real electrical engineering background of electric circuits, and learn to use an oscilloscope, and a volt meter effectively, and be able to diagnose and problems in tube amps.

I don't have the skills or the equipment to build a 'scratch' amp, e.g. making a chassis from sheet metal, and a cabinet from wood planks, so I will find a source for the major components. But I want to learn how to make a bill of materials, how to find parts sources, so I didn't want to go with a 'bag of parts' type kit, even though there are some really good ones out there.

Since I don't have, yet, the engineering chops to make changes to the stock AB763 circuit without, say, inadvertently wiring up an out of audible frequency oscillator that could oscillate the expensive transformers to death, which as I browse the blogs seems fairly easy to do, I will try to build the circuit to as close to stock values as possible, and learn along the way what the major components control.

As I was getting started, before I found this awesome blog, I was naive to think that I would be able to make a few google/bing clicks and find a complete BOM with all of the parts sources, and I could start ordering parts right away! Oh well, that dream ended quickly. So, part of what this mini project will do is collect as complete a bill of materials as possible, with a few sources for the best price for major components. Im not endorsing, or have any affiliation with any parts vendor or manufacturer, I would just like to make it easier for someone else who wants to make one of these amps to get there a little faster.

And, thanks to all the people at music-electronics-forum, first for making this site, and second for all the members great comments and questions to my very basic questions!

So, here goes...

[eschertron]

As a relative newcomer myself, I started ordering the transformers from Hammond. A few projects later, I'm still happy with the products. Not over-hyped and -priced, plus they have a list of equivalent replacement transformers for many common amps, surely including the Deluxe. Good luck! I'm sure you will have fun with the project.

[potatofarmer]

An easy way to come up with a BOM would be to print the schematic and label each component with a letter and number... R1, R2, C1, C2, etc. When you assign it a number, make a note of it in a spreadsheet. For ease of ordering later, make sure to also note anything special about it. "Label | Value | Notes" or something like that. Once you've entered it in your spreadsheet, highlight it on the schematic you've printed out.

I suggest using a spreadsheet because later on when you go to order you can sort the list by the value column and quickly see that you need, say, sixteen 1-meg resistors. I'll typically add a couple columns for, say, "Vendor," and "Vendor Part #" which helps greatly to have in advance. Even though it happens to me every time, it seems I'm never fully prepared for a Mouser order and within 5 minutes of ordering parts I'll remember at least a dozen 5-cent parts that I need. Also with vendor information included, you can make nifty pivot tables.

For capacitors, make sure to get at least the same voltage rating, or better. A lot of coupling caps are rated to withstand 630V - this is fine.
For resistors, make sure to get at least the same wattage (power) rating, or better. If the schematic calls for a 1/2-W resistor, a 1W or 2W will also work just fine.

Also don't forget that you're going to need jacks, sockets, tubes, the tremolo optoisolator "bug", transformers, knobs, a footswitch, wire... all that stuff.

For vendors of general electronic components, I tend to use Mouser. It can be tricky learning how to navigate their site, but once you get the hang of it, it goes quickly. One nice thing about Mouser is that they include the value in the part number, so once you find a resistor you like in 220k, you can just replace the "220k" in the part number with "100k" and get the same resistor in a different value.

You're probably going to need to use multiple vendors though, and someone like Antique Electronic Supply is a decent place to start.

Building a clone amp is a balance of frustration versus cost. Or any amp, really; but with a clone you have the option of a fully compiled kit with all the parts and maybe even instructions. Simple to order, but higher cost. On the other end, you can spend hours hunting down each and every little part, and while your hair might fall out, at least you saved some money.

For a first build, you might want to save your "frustration budget" for actually building the thing. I'd recommend building a Champ kit, because they're great and quite simple. Or buy a little 5W tube amp (there are a bunch out there) and experiment on it. Oh yeah, look up the "AX84 P1 Theory Document" - that's a good start on learning what does what.

[mikepukmel]

Every time I think "OK this is the complete list", I find another part. Getting close now, I think.

[mikepukmel]

Chassis

Found a pretty good chassis, on ebay from seller zachmdhunter .



It has a faceplate and shipping is included in the price, 65.00. I sent them a bunch of emails inquiring about dimensions and hole diameters. So far, sure that standard switchcraft jacks, CTS pots, and carling toggle switches, and standard fender style tube sockests fit in the respective holes. Also, contacted Hammond about their 291BX will fit the transformer hole without modification.

From Hammond:
re their P291BX transformer:
Along the “A” dimension of the transformer the cap dimension is 1.9” and along the “C” dimension it is 2.5”. Please keep in mind that the cutout should be a bit bigger (about 0.125”) to allow for clearance.


From zachmdhunter about this chassis:
All the holes on the front except the pilot light are 3/8- .385 in diameter- The pilot is .70 inch
8 pin tube hole: 1 3/16 with mounting holes- 1 1/4
9 pin tube hole: 3/4 hole w/ 1 1/8 mount holes.
The dimensions of the box is 22 1/4 X 7 X 1 3/4 .
The transformer hole is 2 5/8 X 1 15/16 and the holes are 2 7/8 X 2 5/16 on center. ( 2.625 x 1.9375

A bunch of other suppliers here and there. Mojotone, TubeAmpDoctor in Germany, etc. This one seems to be the best for the price, has a face plate, shipping included.

Has anyone bought from these guys store?

[Leo_Gnardo]

A bunch of other suppliers here and there. Mojotone, TubeAmpDoctor in Germany, etc. This one seems to be the best for the price, has a face plate, shipping included.

Has anyone bought from these guys store?

TAD, it must cost some $$$ to ship in a chassis from Germany. One of my crustomers found a bargain Princeton chassis in Thailand, cost as much to ship as the chassis. Like I say, shippin' will kill ya.

No experience with zach. Looks a good 'un though, faceplate and shipping included, hard to go wrong.

Not planning a reverb? Stick a mid control in that hole.

[mikepukmel]

Deluxe Transformers

Found these from Hammond
Hammond Mfg. - Tube Guitar Amplifier Transformers & Chokes - INDEX

291BX Power
1760H Output
194A Choke

The full set from Mouser is

$169.30
which includes shipping.

[mikepukmel]

TAD, it must cost some $$$ to ship in a chassis from Germany. One of my crustomers found a bargain Princeton chassis in Thailand, cost as much to ship as the chassis. Like I say, shippin' will kill ya.

No experience with zach. Looks a good 'un though, faceplate and shipping included, hard to go wrong.

Not planning a reverb? Stick a mid control in that hole.

Re shipping, it wasn't as scary as I thought. I can't remember now, but something like 20% of the chassis price. Their chassis came in around 100.00.

Ohh, thanks for the tip re putting a mid control in the reverb hole! I was trying to figure out how to plug it, mid would be nice.
Yeah, no reverb on this one, but zach doesn't make a non reverb chassis, so ... not a bad alternative. One other vendor did make a non reverb black face stylechassis but without plate was a lot more $$$.

[mikepukmel]

Similar chassis from Tube Amp Doctor:

50.86 chassis
31.06 ship
---------------
81.92

but that doesn't include a faceplate, and their face plates are something like 30.00+ shipping. so around 130.00. About double the one from zachmdhunter's store.

[mikepukmel]

If you live in the north eastern USA,

Head cabs & combo cabs

makes cabinets. The cheapest combo style fender cab, with no finishing (corners, tolex, handles), is about 160 + 30.00 shipping.

I found his site from robrobinette.com, where he talks about his 5E3 proluxe build. (cabinet looks AWESOME).


https://robrobinette.com/AmpBuild.htm

[g1]

Some cab discussion here:
http://music-electronics-forum.com/t43420/

[eschertron]

Every time I think "OK this is the complete list", I find another part. Getting close now, I think.

... and of course you're ordering extras because, you know, there'll be other builds after this one!

[mikepukmel]

Some cab discussion here:
http://music-electronics-forum.com/t43420/

Thanks g1!

[mikepukmel]

Mojotone (Heyboer) power trans specs 362-0-362? vs Mercury vs Hammond...

I mostly much decided on Hammond, for price vs specs, and haven't seen many complaints about them. Just picking through other web sites today, looked at the Heyboer Deluxe trans spec on the Mojotone site:



Am I reading this right? Is this really 362 0 362vac B+? I thought the old Fender AB763 325 0 325 were designed to push the 6V6's very hard. Can those output tubes really stand another almost 40 vac into the GZ34? What rectified output would we get into the grid2 of the 6V6's on the deluxe design? 325* 1.3 = 422.5 and 325* 1.4 = 455 but 365*1.3 = 474.5 and 365*1.4 = 511. This doesn't look like a PS designed for 6V6's, more like 6L6? The Pro reverb from similar era had 375 0 355 into a 5U4GB which (fender) 440v into grid2 of 6L6's. But the 5U4 is a less efficient rectifier tube, or at least that's what I read.

Wouldn't these higher B+ voltages cook the 6V6s a lot faster?

On a similar vein, there are a whole bunch of transformers on the Mercury Magnetics site for Deluxe amps. They have at least a few that state "lower B+". Only one states a value, 290 0 290v, the others don't, they just write "lower B+". I wrote them a note asking for data sheets for a few more of the transformers.

With today's higher wall voltage, on average, wouldn't it be better to get a lower B+ power transformer for these (Deluxe AB763) style amps? I really would hate to burn through output tubes every 3 months.

The Hammond 291BX has 330 0 330, which is close to the 325 on the Fender schematic. Now Im second guessing (47th guessing) whether this is the best transformer for the job due to the voltage issue.

[mikepukmel]

... and of course you're ordering extras because, you know, there'll be other builds after this one!

Ohhh man, I think about that every day now. I have about 3 orders almost ready to go (one for most of the discretes, one for transformers and some discretes, one for most other stuff, ckt boards, jacks etc). Almost ready to push the button and I thought to myself, "You know, your brother who is a fine guitarist, way better than you'll be, really WOULD like one of these amps too...".

The only thing keeping me from ordering more duplicates of some parts is that I think as its a first amp build, I know Im going to screw up some stuff (hopefully not leading to entry/exit wounds, fires, etc). Im not setting out to do that, just know that the first build is a prototype, and will find better whatever, parts, technique... So I think I will end up making amp #2 different than the first.