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Single 6V6 Guitar Amplifier Project

VOLTAGES FOUND INSIDE TUBE AMPLFIERS CAN KILL YOU! IF YOU DON'T UNDERSTAND PROPER ELECTRICAL SAFETY PRACTICE, DON'T ATTEMPT TO BUILD THIS PROJECT, ESPECIALLY NOT IN YOUR HOT TUB WITH A PAIR OF PLAYBOY BUNNIES 'DISTRACTING' YOU, OK?

Out of all of the hundreds of amplifiers I've owned over the past twenty five years, one of my favorites has always been the old tweed '50s Fender Champ and the similar tweed Princeton. I've had a truckload of these littele amps but my very favorite was a "5F2" model tweed Princeton from the late '50s. For a long time I could never figure out why this Princeton sounded so much better to me than the near identical Champ model until one day I put the two chassis side by side on the workbench. The "5F2" Princeton had twice as big an output transformer. This gives you mo' better bass as well as more volume before distortion. Ever since that day, I've been hot rodding my Champs, Gretsch amps, Supros and other little single-ended screamers with cheap and easy to find Fender "10W" iron, same as used in our little project amp featured below. Although this new Fender transformer is wound to work optimally into an 8 ohm load, it works just fine into any decent single speaker from 3-16 ohms.

So what does this amp sound like? I think you'll agree that this 40+ year old design still works great for blues and other traditional guitar or harmonica styles. With a single coil vintage Tele or Strat you'll get a surprisingly loud, full and warm sound, cleaner and prettier than most stock tweed Champs. With a vintage P.A.F. humbucker or P-90 this amp breaks up like the sound you hear on some of the old blues discs; raunchy when you pick hard but with good note definition. If you want the sound trashier at lower volume settings, use a lower wattage, smaller output transformer (see our Hammond listings). Admittedly, this sound is not what many modern players are used to; it lacks the buzzy/fizzy sustaining R-O-C-K bluster of most modern 'store bought' amps. Also, forgetabout 'user friendly features' 'cause there ain't any. Also, don't ask me about how this amp will 'interface' with your fave stomp boxes; I hardly ever use the damn things. Still, for recording, practice and just jammin' with your pals, this primitive single 6V6 amp may be just what you were always looking for. I'm also betting that those of you who take the time to complete this project will discover that building your own amp is a zillion times more fun than just buying one. Come to think of it, you can't buy this kind of amp new anymore; if you want one you have to build it yourself.

The chassis I've used is common, garden variety aluminum project box you can get from a bunch of different mail order sources. The size I originally used was 13.5"X5"2" deep. I wanted to keep the amp compact but I soon learned that a slightly larger box would be somewhat easier to work with .The original Champ used a steel chassis for economy and strength. You could use a steel Hammond box, stronger but harder to cut. Most of the holes you need to drill are common sizes, so a cheapo set of bits plus a few larger sizes should cover it. Once you line up the fuse holder, pots, on-off switch, pilot light, input jacks, AC cord clamp or connector (I used an I.E.C.), transformer and the mounting bolts you'll know exactly which drills you'll need. A "UNI-BIT" stepped drill bit serves well in place of a number of specific large bits. After carefully laying out ALL of the parts on your chassis, marking the location as exactly as possible with a #2 pencil, center punch all holes before you start drilling. A neat layout, allowing plenty of 'real estate' between the various bits and pieces, will make future fine tuning much easier. For cutting the tube socket holes I suggest Greenlee brand chassis punches, purchased from you local electricians supply store. See the "TUBE SOCKETS" section of this web site for information about the sizes you may need. If you use a 'through the chassis'/transverse mounted power transformer like the reissue Fender Deluxe, as I did, you'll have to cut a large squarish hole. For this hole I used a "UNI-BIT" to get started in the center, then I finished it off with a power jigsaw with a fine metal cutting blade. Finish this hole neatly with a squaring file and sandpaper since you don't want metal burrs anywhere near the transformer wires. When you finish drilling all of the holes, make sure to sand both the outside and inside of the chassis with medium sandpaper, removing all burrs and rough edges.

It pays off big time to mount ALL components before you start wiring . That way, you won't find, like I did, that you've mounted the speaker jack right up against the terminal strip. Better to make a detailed 'map', with measurements, showing where to mount your components. Plan out one area of the amp at a time, starting with the top control panel. Always keep power supply components away from signal carrying parts whenever possible. You'll notice that I spaced the fuse holder, power switch and pilot light on the opposite side of the amp, far from the jacks and pots. Next, find the best location for the transformers, main circuit tag board and also the 'port holes' for the choke and output transformer wires to pass through. You'll notice from reverential study of the original Fender pictorial and the pictures of the 'Steve built' version that I tried to obey the logic of the original chassis layout whenever practical. Believe me, layout matters! If you want to end up with a new amp that sounds as great as the classics, you better build it 'old style'! Lastly, lay out the bottom end of the chassis, where you'll locate the AC cord/connector, rectifier tube, 6V6 power tube, output jack and input tube. I also installed a vent here, just for safety's sake, although the original design didn't use one. KEEP THE INPUT TUBE FAR AWAY FROM THE POWER SUPPLY.

When you mount the fuse holder, switch, and pilot light make sure that these components are TIGHT and that if they come loose in the future they can't 'windmill' into each other and short out! The pots and jacks must also be very tight since they're grounded to the rest of the circuit at this point. The speaker output jack and even the tube sockets also depend on a tight mechanical connection for grounding and proper operation. By the way, the original design was not grounded to the AC line, since most homes in the '50s only had two wire outlets. I've chosen to ground the amp for safety. I did deviate slightly from the original design in that I've used a star ground lug, bolted to the chassis with a solid brass stud. I decided to run some of the individual grounds directly to the star instead of 'bussing' them as on the original. You might want to try experimenting with different grounding arrangements for even lower background noise or ease of construction?

When you install the volume and tone control pots, make sure that you use a full sized steel, non-anodized, internally toothed lockwasher between the body of each pot and the inside surface of the chassis. Clean the chassis with Acetone before you install these parts, then tighten down securely since this is an important electrical connection to the chassis. Note on the original Fender pictorial that the old Princeton had the AC on-off switch 'piggybacked' on the tone control. Since this sort of part is difficult to find nowdays, I used a separate power switch.

The old style 'point to point' wired tag board used in this project must be mounted up on standoffs bolted to the chassis. Those of you lucky enough to own an old Marshall, Vox or other British '60s amp will be familiar with this type of construction. Don't be a tricky bastard like some modern guitar amp manufacturers and mount components on both sides of the board! As much as possible, make all your connections in plain sight where any sensible person making repairs in the future can see 'em. The smart way to build this amp is to first mount any extra needed terminal posts and port holes on the tag board. You'll find that using terminal posts is a much neater mode of construction than having all of the parts meet, unsupported, in space.

Next, before you bolt the tag board to the chassis, mount and solder ALL of the components and wires that belong there. Start with the bigger stuff on the power supply side of the board. Then, work your way over to the signal components. Make all of your connections as neatly as possible. Crimp all wires tightly at the connection point before soldering. Remember, solder ain't glue! If your solder joints are not bright and shiny, do 'em over until they shine like jewels. Looking at the joints under a magnifier helps me do a better job. Double check all of your connections for shorts against adjoining components or terminal posts.

I've used components as much as possible like those found on '50s amps, including Sprague electrolytics, "Black Beauty" signal caps, CARBON resistors and even cloth covered wire. I wanted to see if I could get close to the original '50s sound. Accordingly, I avoided where ever possible modern parts like metal film resistors, Teflon wire, polypropylene signal caps, etc. I encourage you to try ANY parts you think will sound 'interesting' for YOUR musical pursuits. I wanted to used the original stuff as a reference and jumping off point for future experimentation with some of the more exotic audiophile parts. How can you know if you're getting anywhere if you can't remember where you started from?

Before you mount the loaded tag board in the amp, wire up the power transformer first. Start with the connections to the switch, fuse and pilot light (make sure that one 'leg' of this filament connection is grounded at the star ground lug). Run the appropriate leads from your AC cord or AC inlet connector to the switch and fuse assemblies. Carefully solder the power transformer high voltage center tap RED/YELLOW striped wire AND one of the green filament leads to the star ground lug. Then solder the two solid RED high voltage wires to the appropriate lugs on the rectifier tube socket. Next, solder the two YELLOW 5V filament wires to the appropriate lugs on the rectifier tube socket. After you've soldered and checked all of these power supply connections, I recommend that you plug in the amp and check the voltages with your meter. You should be getting around 5V across the two YELLOW wires, around 675VAC across the two solid RED wires, around 337VAC across one solid RED wire and the star ground where the striped RED/YELLOW wire is now soldered. I've checked a bunch of reissue Deluxe Reverb power transformers and they're fairly consistent. You should measure around 6.6VAC-6.9VAC or so across the GREEN wire soldered to the pilot light assembly and the other GREEN wire soldered to the star ground. These voltages are measured with no tubes installed. The voltages will probably measure somwhat lower under load, with tubes installed but expect the filament voltage to be over 6.3VAC, since this tranformer is designed for a heftier filament load (two 6V6 and a handful of small signal tubes) than we're giving it. 

Some of you have e-mailed me requesting my measured operating voltages to use as a reference, so here goes. When the amp is completely assembled, with all tubes installed you should measure around 386VDC between each of the two yellow leads of the power transformer and ground; I made this measurement at the 5Y3GT rectifier tube socket. You will measure around  375VDC or so  between pin three (the plate) of the 6V6GT power tube socket and ground with the tube installed. Between pin four ("G2", the screen/"supressor" grid...) of the 6V6GT socket and ground you'll probably get around 382VDC with the tube installed. Don't forget to consult the RCA Tube Manual while you're building this project. Yes, that book will kindly inform you that you're way beyong the "max." ratings of the 6V6GT. So what?  If that worries you into a sissy fit, tough; go build somebody elses FREE project.

Most of the primary and secondary wires from the power transformer should be arranged into appropriate pairs: the two GREEN 6.3V wires, the two YELLOW 5V wires, the two RED high voltage wires, and the two BLACK 120V primary wires. Snugly and neatly twist these individual pairs of wires together, hand over hand. Route them to their destinations and cut to length, allowing enough slack to strip the ends for the solder connections but no more than necessary. Keeping the leads short and neatly routed makes a better amp, I think. This presents another good argument for making the chassis no larger than necessary, so you may want to use the smaller of the two Hammond chassis suggested on our parts list for this specific project? The RED and BLUE primary wires from the Fender output transformer should be twisted together, as should the BLACK and GREEN secondary leads. Also twist together the WHITE and BLACK wires from the Hammond choke.

The new Fender Deluxe power transformer we recommend for this project is Fender Part #041316. You can use ANY 'combined plate and filament' power transformer providing that it offers a center tapped high voltage section offering 300-360VAC, measured between one of the RED wires and the striped RED/YELLOW center tap. Hammond, Thordarson and other companies offer alternative new power iron choices. You can also scrounge some used or surplus iron if it has the proper voltages. If you choose to use a power transformer with a high voltage section above 360VAC, then that you can use a single 6L6, KT88 or other such single output tube instead of a 6V6GT but you may have to experiment with the cathode bias resistor value. Current capacity should be in the range of 125-200mA, common for this type of iron. The 5VAC filament tap should be good for 2A-3A, the 6.3VAC tap should be good for 2.5A or better. Actually, one of the nicest versions of this amp I've ever heard uses an old SUPER CHAMP power transformer: I measured 365VAC from each red wire to ground, 416VDC from each yellow wire to ground, 407VDC at pin three (the plate) of the 6V6GT and 417VDC at the screen grid. No, the amp will not blow up at these somewhat elevated voltages, providing that you use first class tubes; this amp has been working for years with no service required. Some '70s silver face Champs show even higher plate voltages, believe it or not.

Novices should note that MOST tube amp power transformers use the standard wire color code described above. Basically, you've got a couple of primary wires, ususally both BLACK or one BLACK and one WHITE plus maybe a solid GREEN ground wire; these go to the 120VAC wall socket. On the other side of the transformer you've got the "secondaries", all of the various voltages you need to power the filaments of the rectifier, input and power tubes, plus the high voltage to the plates of the power tubes. The two solid GREEN wires on the secondary side supply the 6.3VAC to the filaments of the input and power tubes. Sometimes you will find a striped GREEN/YELLOW center tap wire for the 6.3VAC filament line, and this connects to ground in most guitar amp and hi-fi hobbyist circuits. If you intend to use a transformer with a center tapped filament, do not connect it  (usually a green/yellow wire...) to ground or you may 'smoke' that winding! The two solid YELLOW wires supply 5V to the filament of the rectifier (5AR4, 5U4, 5V4, 5Y3, etc) tube. The high voltage lines consist of two solid RED wires, as well as a striped RED/YELLOW wire designated the center tap. Note that the full high voltage capacitiy of this section of the secondary is measured across the two RED wires. In the case of the Fender Deluxe reissue power transformer, this will read around 675VAC (meaning, VOLTS ALTERNATING CURRENT...). If you measure each half of the high voltage secondaries, you will read around 337VAC, or half of the total. This is measured by putting one probe of your voltmeter on one solid red wire and the other probe on the striped RED/YELLOW center tap wire. Being able to read these voltages in guitar amps is a valuable trouble shooting skill. Practice measuring the power transformer voltage in a variety of guitar amps and even in junker transformers you find at swapmeets.

I used a Hammond 2H/200mA choke but if you're on a tight budget you can slide by with a 50 ohm/25W power resistor. Any good quality choke from 1-10H will work, providing that the current capacity is 125mA or better. It helps to have low D.C. resistance, too, so avoid anything over 150 ohms.

Now mount the tag board and carefully route each wire to the appropriate component in the amp for final soldering. Check your work frequently against the Fender pictorial and the photos.

One area on the original Fender 5F2 Princeton pictorial that was unclear to me was the wiring found 'south' of the filter caps. The original Princeton featured a vulcanized fibre tag board with brass eyelets for electrical connections and punched holes for wire routing. Check out the hole for the exit of the output transformer primary RED and BLUE leads found 'south' and between the the first two 8uF electrolytics. On the Angela version we're using a phenolic turret terminal board, so the interwiring connections between the various components needs some clarification. Note that in the Angela version of this amp a short length of YELLOW wire runs from lug #8 of the 5Y3GT rectifier tube socket to the first turret terminal, and that the positive lead of the first 16uF electrolytic as well as the WHITE wire from the Hammond choke also connect here. The BLACK and WHITE wires from the Hammond choke enter the chassis through a 'porthole' you have conveniently drilled in this area. Please use a Radio Shack rubber grommet to face this hole for safety. The BLUE and RED primary wires from the output transformer also make their grand entry into the chassis through this 'porthole'. The BLUE output transformer primary wire connects to lug #3 (the plate) of the 6V6GT tube socket. The RED output transformer primary wire connects to lug #4 (the screen grid) of the 6V6GT tube socket. A short length of plain white wire runs from lug #4 of the 6V6GT tube socket to the third turret terminal to connect with the BLACK wire from the Hammond choke, the positive lead of the second 16uF electrolytic capacitor and one leg of a 22K .5W resistor.

You should also plan on drilling another porthole, also faced with a Radio Shack rubber grommet, in the same neighborhood for the GREEN and BLACK secondary wires from the Fender output transformer. The GREEN wire from the Fender output transformer connects to the positive/"hot" lug of the speaker output jack. Note that a short length of plain white wire also connects to the positive/"hot" lug of the speaker output jack and runs to ninth turret terminal where it is joined to one leg of another 22k .5W resistor. The BLACK wire from the Fender output transformer connects to the negative/ground lug of the speaker output jack. Be sure to use a full sized internally toothed steel non-anodized lockwasher on this speaker output jack, and tighten it down securely, since this is an important electrical connection to the chassis.

If you're using the popular Hammond 125E you'll have to choose which primary impedance you'd like to try; since many are available (between 1.2K and 25K) offering different tonal choices. The 'textbook' primary impedance choice for a single-ended 6V6 is around 5K, athough you might want to try anything between 3K and 8K. Lower primary impedances will give you slightly more power output and more distortion, the classic design 'trade-off'. For hi-fi, a higher than textbook primary impedance is currently fashionable in hobbyist circles, since it offers a more linear sound with less distortion at only slightly less power. For guitar amps, anything goes. The impedance YOU dig is the 'good one', and this is pretty easy to mess around with if you choose the 125E. Even a monkey with a soldering iron might hit the right two solder lugs (there's only six lugs....all found on the secondary side of the coil). Some classic vintage guitar amps apparently used lower than textbook primary impedance output iron by design. Keep in mind that such a choice was usually a few pennies cheaper in the '50s, so maybe that had something to do with it. Look at the top column of Hammond's hookup diagram (found on the packing box of the transformer) and find your speaker impedance (e.g. 8 ohms), then scan down to the closest primary impedance for a single 6V6 (for starters, try "5600" ohms...), then scan over to the left hand column and it'll tell you exactly which two of the available six lugs to hook your dang speaker to, right? For example, if you have an 8 ohm speaker and want to select a primary impedance of "5600" ohms, hook the two speaker terminals to lugs 1 & 5. Isn't D.I.Y. guitar amp building easy? You know it! By the way, the 125E was designed as a 'Swiss Army Knife" push-pull OR single-ended transformer: for single-ended use in this project, use the BLUE and BROWN wires only, hook 'em up to the same circuit points as you would the Fender 10W output iron described above. The BROWN wire of the 125E goes to lug #3 (the plate) of the 6V6GT, the BLUE wire goes to lug #4 (the screen grid) of the 6V6GT. Just 'cap off' the additional RED wire (the center tap...) with a wire nut. Choose the appropriate two lugs on the secondary side of the 125E according to the impedance ratio table included with that transformer. By the way, it doesn't matter which of the two output lugs you designate as positive (+) or negative (-), just hook the two wires to your speaker and it'll work fine.

See our Hammond Transformer pages for propaganda about the NEW 125ESE and other, similar single-ended output transformers. Hammond designed these with guitar amps in mind. Yes, I think they're great for this project but my favorite output iron is still the "10W" Fender I've been using for years.

Wiring up the input jacks is a bit tricky. We hope to put a detailed photo and some diagrams up here in the near future. Study the photos carefully. Learn how to check the continuity of the various lugs before you wire 'em up. Then you'll know how this simple device works. You'll notice at some point that input #1 is the HOT one, and input #2 is for when you're in a mellow mood.

When you first fire up the amp, do so without tubes installed. Better to check measurements in the amp with your meter first. Compare against voltages given on the original schematic, in the pictorial below, and those mentioned in my rather wordy and redundant commentary above. You will probably have a higher voltage B+ than found on most Fenders from this period. On the other, as I've mentioned above, later Champs from the 'silverface' period, ran the output tube even harder. Next, install the power and input tubes. Make sure the filaments light up. If they light up and you don't see any smoke, install the rectifier tube. If you've done everything right up 'til now, you're ready to play music. If not, retrack your steps. Problems in amps are seldom due to 'bad parts'; wiring error is the culprit most of the time, I've found.

PLEASE USE GOOD TUBES! Don't waste your time with cheap imported junk! Just because somebody gives a cheap Russian tube a cute brand name, or paints on a fancy logo doesn't miraculously turn it into a sonic gem. In my experience crummy Russian, Chinese, etc. power tubes are more likely to become intermittant, short out or otherwise misbehave and fail prematurely, maybe taking your transformers or other valuable circuit components with 'em. I've never heard a single Russian or Chinese small signal tube that I would use in a critical application. In my opinion, ALL of the Russian small signal tubes currently on offer sound awful in both guitar and hi-fi amps, and I have found them to be unreliable. I find it hard to believe that the folks selling these things are actually testing and listening to them. Manufacturers use these cheap tubes in new amplifiers to make mo' money, and because they're convinced that most consumers can't hear the difference. The guitar and hi-fi rags hype these crappy new tubes because the distributors fork over big advertising bucks, and have even been known, BELIEVE IT OR NOT, to give "free" stuff to "reviewers". In the past year I've read "surveys" of various types of tubes in several hi-fi and guitar rags where the universe of discourse was pretty much restricted to stuff being flogged by their advertisers, with the obligatory nod to the N.O.S. classics.

The truth is, there are hundreds of thousands of good American N.O.S. 6V6GT, 6L6, 5Y3GT, 5U4GB etc. being actively marketed right now at very modest prices by dozens of suppliers, large and small. This vast supply of affordable good tubes will probably last for many years to come, much to the chagrin of the Russian tube pimps, since hobbyists, not the cheapskate large OEMs, are still the main market. Still, prices are likely to rise if the demand remains strong and the supply starts to dwindle so there's a good argument to be made for stocking up now.

If your budget is too meager for N.O.S., consider the millions of good used tubes out there, usually cheap or FREE for the asking. Try your local hamfest or antique radio swapmeet as well as local surplus electronics dealers and olde TV repair shops. If you gather together enough used examples you're sure to find something great. Don't be afraid of used tubes; many have seen light service. Stick with the better brands like RCA, Tung-Sol, etc. You will need a good tube tester to sort out the good from the bad or at least give 'em a trial spin in an amp you can afford to blow up, not your old tweed Deluxe.

The best sounding 12AX7s I've heard in this amp are by Telefunken, Amperex, Mullard and RCA. If you're on a budget, the Yugo flat plate 12AX7 Telefunken copy is a good choice but read the caveats in our tube listing pages, please! I usually use a JAN Philips 5Y3GT rectifier but a GZ34 sounds bitchin', providing that you uprate the filter caps to at least 500VDC. I've had good luck with 6V6GT by RCA, Philips JAN, and even GE in that order.

Like the original '50s tweed Champ/Princeton, you'll notice a slight amount of background hum/hiss with the volume control turned up all the way during normal operation. This is normal; it comes with the S.E. territory. Don't be a big jerk and add a bunch of high value electroltyics to 'beef up' the power supply. This will reduce the background noise but it'll also 'slow down' the response of the amp and make it less musically involving. If you're a noise freak, go build something else, like maybe a metal detector. I've experiement with different filament supply schemes to try to get the noise/hum down and, so far, I haven't found anything that works significantly better than the original design with it's primitive 'chassis return' filament line. If you use the filament arrangement used in our SUPER SINGLE-ENDED 6V6GT project  (a pair of 10 ohm resistors from each leg of the filament at the pilot light...going to a common junction at the star ground lug...with the filament twisted green pair then going on to the 6V6GT and the 12AX7...) you'll get only marginally less racket. Fender used this arrangement in various models without center tapped filament transformers and it only seems to matter much in higher powered amps.

A good amp deserves a good speaker. Try to find an old alnico magnet Jensen, Celestion, Altec or other speaker, preferably with original light cone. If you can't score any of those beauties, the reissue Fender 10" alnico blue speaker used in the 4X10" tweed Bassman sounds fine. I haven't tried any of the "new" Jensens yet but they sure look cool. Actually, there's lots of interesting older alnico 8"-12" speakers to try out, some you can find on the junk pile at your local Hamfest or TV repair shop, dig? Good old speakers can even be found in old TV sets! What we're looking for is a speaker with a lively 'happy Springtime' sound, NOT a 'heavy metal' powersoak. Avoid most modern speakers with ceramic magnets, including most new Celestions, Pyle, EV, JBL, Eminence, etc. These modern speakers may sound OK in your big 'acid rock' rig but not in my little amp!

I used an old Jolida Chinese 12AX7 tube crate for my amp cabinet, in keeping with my fiercely retrograde 'hillbilly lifestyle'. The frame of this crate is soft pine, the sides and speakerboard are thin birch plywood so it sings nicely. I was going to cover it with pretty contact paper and glitter but I think that might dull the sound. I feel that way about all coverings on guitar amps now; avoid 'em if you can. Go ahead and experiment with different woods but I think you'll find that a thin birch plywood speaker board, mounted on four small cleats from behind, is the way to go. A soft pine box sounds great but don't make it any heavier than you need to. Don't use particle board; it sounds lousy for guitar amps, weighs too damn much and splinters into the sawdust from whence it came when you drop it. Fine hardwoods look pretty but don't sing unless you use very thin panels like on an acoustic guitar.

No matter what kind of cabinet you design, make sure the tubes are well ventilated. The chassis as shown mounts the same as the original by two bolts from the top. I think you'll find, as I did, that the thin aluminum chassis requires more support than this, so I'll design my next amp to also use bolts on each side of the box, bolted through the chassis. Be sure to locate all of these mounting bolts so that they don't bump into live connections inside the amp! HAVE FUN!

For you swingin' lovers  fortunate enough to be fluent in the Italian language, you will find our little amp featured in Luciano Macri's AUDION magazine, Issue 12, 1997, along with some other good tube hi-fi projects. The article is titled "Amplificatore single-ended 6V6 per chitarra". The address of Audion is: Piazza Madonna Aldobrandini 7, 50123 Firenze, Italy. Tel:055-293267.

NOTES TO BUILDERS: Below you'll find the original Fender Princeton 5F2 schematic and pictorial. We include these since they inspired our project. If you study those documents carefully you'll note that we made some minor  (mostly...) layout and parts value changes, based on our choice of readily available parts and also to make the amp a bit more 'D.I.Y. friendly'. The Angela pictorial, the photos below and my commentary are your best guide for the actual building process, not the original Fender documents. Be mindful of the fact that is a FREE project, NOT a "kit". YOU decide how to build it, what parts to use, and where to buy 'em. Sorry but I simply don't have time to answer ANY technical inquires about this project nor to troubleshoot/evaluate built examples, whether or not you've bought the parts from us. Remember, D.I.Y. means DO IT YOURSELF. 

On August 1, 1998, Mark Abbott from Australia e-mailed us these suggestions:

"I recently helped a friend build your 2 X 6V6 amp design. The way the guy originally had it was pretty crummy, but with some tweaking, (bias and earthing problems) the amp sounded wonderful.

I think you should ditch the 5f2 as the single 6V6 amp design as the tone control sucks, the 5f2 uses a 1 meg pot and this is definitely the goods. In the amp I helped my friend with we used a 2 meg pot which was great for getting rid of excessive top end from the 500pf (treble boost cap). I also upped the value of the treble shunting cap to get the Clapton tone from a humbucking pickup.

My friend had the misfortune of having a 280VDC rail, I used the variac to up the voltage to 350VDC, this is where amp appears to like to be. Also the preamp voltage is around 300VDC for the 12AX7.

What I'd also recommend is to have an extra stage of filtering rather than upping the first filter cap to 80 uF. This is in the style of Dan Torres. Which consists of a 20 to 50 uF filter cap followed by a 300 ohm resistor(5w) then the 20uF to 50uF filter cap going to the output transformer. This could also be handy for people having problems with excessive valve wear from too high a plate voltage as about 30 volts are dropped across the 300 ohm resistor.

In closing I'd like to thank you for excellent service when I've had to order parts from you ...I've found helping my friend with his amp to be very rewarding and of course the bottem line is the amp eats the fender blues jr's currently available. Oh yeah, the Fender 10" alnico blue was a perfect speaker choice for this amp."

On March 29, 2001 Cliff Ross wrote:

Steve, I read with great interest your Single Ended 6V6 Article some time ago and took up the task of building my first guitar amp. Your technical prose is excellent by the way. Clear readable and comforting to us technically disinclined. Since then, using key components from your company, I have completed a modified 5F2A which drives a 10" Fender Blue Frame Alnico with 15 Watts, and a modified 5E3 piggy back style which drives two 12" reconed Celestion Greenback with 25 watts. I had more fun than I did tearing apart the top end of my first V-6 and finding I only had six parts left over after reassembly. Naturally, my local tube amp tech had to advise me along the way and pull me through some rough spots.

Your line of Hammond transformers was key. I avoided a suggestion you made somewhere to use "any old iron" for the output and I am glad I did. The values were appropriately close to the specs I needed and with the various configurations available I was able to avoid chewing a big PT mounting hole in my chassis. Your prices and availability were very competitive and your shipping was reasonably prompt. Thank you.

Both projects barked nicely but hummed excessively at rest. To some extent this may be inherent in the design. My amp tech pointed out that the vintage push back wire was fine except where it fed signal to the preamp tube. He thought shielded wire with the shield grounded to the chassis at one end might be better. He suggested that picking up Radio Moscow was probably not the sound I was looking for. I re-did the 5F2A with Teflon 20 gauge 600V shielded wire as he suggested and this brought down the hum dramatically. This was fairly easy and very inexpensive and I considered it a valuable tip to hum reduction.

The 10" 25W Fender Blue Frame Alnico at about $50 was far and away the right speaker at the right price for the 5F2A. I like to operate with a Telecaster, sometimes clicking and chirping, sometimes growling but not really crunching and never gently weeping. I can't envision the 5F2A in a heavy metal situation or putting out thumping bass. I tried a 12" Greenback which was okay but lacked the bite when bite was called for. I did not try a ceramic magnet unit, believing it would be disrespectful to the design if not illegal. I suspect the Fender Blue Frame is an Eminence built product which might be gotten cheaper still without the Fender name. Can anybody advise what Eminence part number I would be looking for?

Finally, with the 5F2A I have broken through years of having to avoid problems at home and at practice by playing with the volume knob at or below the 9 o'clock position. I can now play with the knob buried and the amp full out which I think is where it belongs. The Sylvania 6V6 doesn't seem to mind. Also, I might be able to unload various overdrive pedals designed to 'simulate the vintage sound of an overdriven tube amp' because now I have an overdriven tube amp which I built for less than the cost of a couple of these stupid pedals" 

Steve's Suggested Parts List For The Angela Single-Ended Amp Project

Please note that this FREE project is NOT a "kit" nor do we offer a complete parts "package". Below find MY choices (with some suggested alternatives mentioned here and there...) for most of the key parts needed. Planning your own parts list is an important part of the D.I.Y. tube audio experience; don't expect anybody else (especially ME...) to do it for you. We encourage you to shop around and build this project according to your own preferences and budget; as long as stick fairly close to the values I used you'll do no harm to this circuit. Can't make up your mind about which parts to use? Follow the advice of my hero Yogi Berra; when you come to a fork in the road, TAKE IT. You really can build a nice amplifier with scrounged/surplus parts as well as with expensive 'audionut' parts. The quality of your craftsmanship is probably more important than how much you spend on the bits and pieces. PLEASE CHECK OUR WEB SITE CATALOG LISTINGS FOR CURRENT PRICES OF THE VARIOUS PARTS WE OFFER FOR THIS PROJECT.

1. Chassis box, Hammond 1444-28, 16"X8"X3" deep, aluminum, big enough to build our SINGLE 6V6 AMP PROJECT, SUPER SINGLE-ENDED 6V6 AMP PROJECT and lots of other compact tube guitar amps, SEE OUR CHASSIS LISTINGS FOR CURRENT PRICES. Alternatively, if you need to build the SINGLE 6V6 AMP PROJECT as compactly as possible (see pix below), choose the Hammond aluminum 1444-18, 13.5"X5"X2" deep, but be extra careful mapping out the location of parts. A stolen 'night depository' box from a bank also makes a nice chassis, if you like the look of bronze.
2. Power transformer, Fender part #041316 for reissue Deluxe Reverb, this ain't fancy looking iron but it'll do the job, SEE OUR FENDER TRANSFORMER LISTINGS FOR CURRENT PRICE. If you want a lower plate voltage, see our Hammond listings; anything with similar specs with work fine, possibly requiring some minor tweaking of the other component values.
3. Output transformer, Fender 10W single-ended 6V6GT type,SEE OUR FENDER TRANSFORMER LISTINGS FOR CURRENT PRICE. Alternatively, if you want to experiment with different tube types and output impedances, or you want something that'll work in both the SINGLE 6V6 and the SUPER SINGLE-ENDED 6V6, try one of the Hammond Universal types, like the 125E or any of the the NEW air-gapped single-ended 125SE series, including the NEW 125ESE!!! See the Hammond section of this Web site for details and prices.
4. Choke, 2H/200mA, Hammond #157R, SEE OUR HAMMOND TRANSFORMER LISTINGS FOR CURRENT PRICE.
5. AC inlet port, grounded three wire IEC/Eurocord type found on many modern Marshall amps, computers, etc. I believe a detachable power cord is safer. SEE OUR CONNECTORS LISTINGS FOR CURRENT PRICE.
6. Cinch octal tubes sockets, Micanol, premium version, SEE OUR TUBE SOCKET LISTINGS FOR CURRENT PRICES. Alternatively, the Angela (A.K.A. "AUDIO NOTE") premium ceramic/silver sockets are used in some of the worlds most exciting new hi-fi and guitar amps, and they're not much more dough.
7. Speaker output jack, Switchcraft USA, silver plated Mil. Spec. version, with hardware, SEE OUR JACKS LISTING FOR CURRENT PRICE.
8. Input jacks, switched/shorting Switchcraft USA, silver plated Mil. Spec version, with hardware, SEE OUR JACKS LISTING FOR CURRENT PRICE.
9. Fender tone pot, CRL USA 250K audio taper, with hardware, SEE OUR FENDER AMP PARTS LISTINGS FOR CURRENT PRICE.
10. Fender volume pot, CRL USA 1 Meg audio taper, with hardware, SEE OUR FENDER AMP PARTS LISTINGS FOR CURRENT PRICE.
11. Switch, on-off, metal bat, made in USA, with hardware, SEE OUR CONNECTORS LISTINGS FOR CURRENT PRICE.
12. Ground lugs, tinned brass, bag of ten pieces, SEE OUR CONNECTORS LISTINGS FOR CURRENT PRICE.
13 .0047-.005/400-600V tone control capacitor, polypropylene, SEE OUR VARIOUS SIGNAL CAPACITOR LISTINGS FOR CURRENT PRICES. Old mica caps and NEW OLD STOCK mylar/paper/foil tubulars like CDE Black Cats also sound fine in this circuit, as do ANGELA/JENSEN paper in oils (especially if you're rich....) buy any decent capacitor will work just fine.
14. Input resistor, 1 Meg., .5W Riken Ohm carbon film with gold plated soft copper leads, SEE OUR RESISTORS LISTINGS FOR CURRENT PRICE. Any good brand of carbon resistor will sound fine here.
15. Sprague Atom axial lead electroltytic capacitors, 16uF/475VDC, SEE OUR SPRAGUE CAPACITOR LISTINGS FOR CURRENT PRICES. You can also use Sprague 20uF/500V. Want to try an alternative to old fashioned electrolytics? Try Angela FAST CAP 22uF/600V metalized polypropylenes, SEE OUR ANGELA/SCR CAPACITOR LISTINGS FOR CURRENT PRICE.
16. Sprague Atom electrolytic, 25uF/50VDC, SEE OUR SPRAGUE CAPACITOR LISTINGS FOR CURRENT PRICE.
17. Axial lead tubular signal capacitors .022/600VDC. Any good signal cap will work here, including Angela/SCR Tin Signal caps, Angela/Jensen paper in oil caps, vintage paper/mylar/foil caps such as Black Beauty or Black Cat branded versions (N.O.S. only, no used stuff...), Vitamin Q, polypropylene/aluminum foil audionut types (ignore the fetishistic advice about the 'best sounding' direction...), etc. I'll leave it to you to experiment and discover which ones you think are "best". SEE OUR VARIOUS CAPACITOR PAGES FOR CURRENT STOCK AND PRICES.
18. Resistor, Riken 22K, .5W, two needed, SEE OUR RESITORS LISTINGS FOR CURRENT PRICES OF THE VARIOUS RIKENS USED IN THIS PROJECT. IF YOU DON'T WANT TO PAY FOR FANCY FUCKIN' 'DESIGNER RESISTORS', 'ANTIQUE' CARBON COMPOSITION TYPES BY ALLEN-BRADLEY, STACKPOLE, ETC. ALSO WORK REAL GOOD.
19. Resistor, Riken 470 ohms, 1W.
20. Resistor, Riken 1.5K, .5W.
21. Resistor, Riken 270K, .5W.
22. Resistor, Riken 100K, .5W.
23. Resistor, Riken 68K, .5W.
24. Resistor, Riken 1.5K, 1W.
25. Tag board, phenolic (plastic impregnated paper junk...), two rows of nineteen plated brass hookup terminals, 8"X3", four mounting holes, complete with four 'stand offs' and all other mounting hardware for this project. Very simliar to tag boards found on early Marshall plexis and other classic guitar and hi-fi amps. Good for various other 'point to point' wired tube audio circuits. We include four extra screw mount turret terminals you can install on the board where you need 'em. With purchase of this part from us we'll also include a drilling map for the four wire routing holes as well as the five extra turret terminals located on the face of the board. SEE OUR CONNECTORS LISTINGS FOR CURRENT PRICE.
26. Cloth covered hookup wire, stranded tinned pure copper, 22 guage for chassis wiring and 18 gauge for speakers and filaments, like old '50s Fender wire. See our Wire and Fender Amp Parts pages for current prices.

A BIG Thanks To My Old Pal Jesse Quitsland For His Schematics And Other Contributions TO Our FREE Projects!!!

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