5E3 Build (first tube amp)

geetah

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Hi everyone,

My name is Josh and this is my first post. I have learned so much from reading this great forum over the years and want to thank you all for sharing such rich, useful information.

I feel a need for tweed and am gathering parts for a 5e3. It's my first tube amp build.
I have built pedals and solid state amps over the last 10 years, can solder reasonably neat and shiny, and have read a lot about safety - and will keep revising along each step of the way.


So far I have:

Classictone 40-18078 Power Transformer
Classictone 40-18022 Output Transformer

TAD 5Y3GT, 12AX7A, 12AY7, matched pair of 6V6GT-CZ

Sprague 50v caps, yellow Mallory 600v caps


Notable parts in my cart:

F & T 22uf 500v caps
Carling SPST switches
CTS pots
Switchcraft jacks
sockets

Eyelet and backing board
Chinese import drilled chassis


Some undecided/unsure/to get parts:

Wire type
Resistors
tweed material
Wood
Speaker
Power strain relief, clamp



I would love to get the eyelet board populated - so want to make a decision on the resistors types. I love the look of the carbon comp resistors.

So many great songs would have been recorded using amps with these old style resistors but I have been reading the threads about noise.


Also wondering any changes I should be making. I read about putting the screen resistors in to help prolong power tube life, but then read it takes some of the 'nasty' away from the overdrive.

I love that wild 50s sound so I think I should leave them off?

Then there was the standby switch being harsh on tubes? etc etc. Many choices.


Any thoughts, ideas or anything else will be much appreciated. Many questions and dribblings I know :)
Glad to be taking part in the fun!

Thanks for reading,

Josh
 

2L man

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Welcome! That looks good plan!

What comes to "grounding" I recommend you use Robrob "optimized" which uses single ground bus for all return current and Chassis is a shield/safety earth.

Soldering for example 220k resistor over Stby Switch contact keep small anode current flowing and no "cathode poisoning" should not happen.

If you wan't a bleeder resistor improve it to two series and use middle point for filement elevate voltage. Usually power tube cathode is used but there is some signal on lows and voltage is only 20V. There is recent thread of this.

I think it is worth using metal film resistors on pre amp to reduce hiss. Also it looks like using shielded cables from jacks and soldering 68k resistors direct to control grids improve signal/noise ratio. This also save some room on board.
 

King Fan

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Welcome. You're off to a good start. Random thoughts:

1. You may get a lot of ground scheme argument. Rob's split ground scheme is quiet; his optimized build is also quiet but needs a custom board with re-arranged layout. A third option is a single ground without the optimized board. That would be quiet too!! and not too hard. For both noise and safety, any one of the three would work.

2. Carbon comps do *look* cool, but here looks and sound may trade off. Is your amp gonna be a looker or a player? My first boutique-built 5E3 had all CCs in the signal chain. Guess what, it hissed until I put metal films in the input chain. Endless topic of debate, but here at least there's some logic. For logical (and totally optional) use of a *few, selective* carbon comps for possible sonic mojo, Google "Geofex carbon comp". Logically, this means you could build a 5E3 with just a few carbon comps in selected spots. I did. But many smart folks build nice amps with none.

3. Re standby, Google "Valve Wizard standby." Not needed or wanted, possibly slightly bad for tubes in extended use. This is an easy feature (no standby) to copy from Rob's optimized version! FWIW Fender didn't use one in the 5E3, either.

4. Screen-grid resistors (and possibly a 470K PI grid stopper, on Rob's page): If you like the wild '50s sound, start without them but try to leave room to add (the grid stopper is easy, the sockets are harder). If the OD is too harsh, I'd add the grid stopper first, then maybe the screen-grid resistors.

5. Wire -- important in a 5E3, since you want wire that will shape well and lie down neatly in that small space. Stateside, the two big winners seem to be either cloth-covered Fender-style solid core or 'topcoat' stranded/plastic wire where the neatly twisted strands are given a topcoat of tinning. Oh, and 22ga will work almost everywhere (I use PT cutoffs for B+ to the board).

Afterthought: Wire the AC mains Rob's way (with Oz wire colors of course).
 

Ricky D.

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You might want to reinvent the wheel but you don’t have to. The original circuit and layout from 1959 works just fine. Build to the original design and get to know it for a month or two before you modify.

Solid core cloth wire is easy to work with.

B+ will be too high with a new production 5Y3. Use a NOS 5Y3 to get the 360 volt B+ you need.
 

King Fan

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I agree -- I *mostly* wire my board to the Fender layout, upsize a few resistor watt ratings, then wire the grounds and AC mains like Rob. And except for power and safety update mods, the stock 5E3 needs a *long* shakedown cruise to learn both channels, all the interactive knob settings (hint -- sweet hides in the first 3-4 lines on the active volume dial, clean can involve 9-11 on the inactive dial, and many kinds of dirt, nicer and nastier, lie all around). Oh, and an extra month to check out jumper options... then you can mod with some idea of actual destinations.
 

geetah

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Welcome! That looks good plan!

What comes to "grounding" I recommend you use Robrob "optimized" which uses single ground bus for all return current and Chassis is a shield/safety earth.

Soldering for example 220k resistor over Stby Switch contact keep small anode current flowing and no "cathode poisoning" should not happen.

If you wan't a bleeder resistor improve it to two series and use middle point for filement elevate voltage. Usually power tube cathode is used but there is some signal on lows and voltage is only 20V. There is recent thread of this.

I think it is worth using metal film resistors on pre amp to reduce hiss. Also it looks like using shielded cables from jacks and soldering 68k resistors direct to control grids improve signal/noise ratio. This also save some room on board.
Thanks 2L Man,

I think I am going to follow the standard layout Rob has on his site. I have printed this and the original Fender schematic and layout to get familiar with.

I am interested in the bleeder resistor if it doesn't affect the sound of the amp. I will dive into that when the time comes.

I think I will just put the carbon comps in the places where they make the difference, as R.G writes about in the link. Thanks for all the information.

5e3_Deluxe_Amp_Layout_small.png



Welcome. You're off to a good start. Random thoughts:

1. You may get a lot of ground scheme argument. Rob's split ground scheme is quiet; his optimized build is also quiet but needs a custom board with re-arranged layout. A third option is a single ground without the optimized board. That would be quiet too!! and not too hard. For both noise and safety, any one of the three would work.

2. Carbon comps do *look* cool, but here looks and sound may trade off. Is your amp gonna be a looker or a player? My first boutique-built 5E3 had all CCs in the signal chain. Guess what, it hissed until I put metal films in the input chain. Endless topic of debate, but here at least there's some logic. For logical (and totally optional) use of a *few, selective* carbon comps for possible sonic mojo, Google "Geofex carbon comp". Logically, this means you could build a 5E3 with just a few carbon comps in selected spots. I did. But many smart folks build nice amps with none.

3. Re standby, Google "Valve Wizard standby." Not needed or wanted, possibly slightly bad for tubes in extended use. This is an easy feature (no standby) to copy from Rob's optimized version! FWIW Fender didn't use one in the 5E3, either.

4. Screen-grid resistors (and possibly a 470K PI grid stopper, on Rob's page): If you like the wild '50s sound, start without them but try to leave room to add (the grid stopper is easy, the sockets are harder). If the OD is too harsh, I'd add the grid stopper first, then maybe the screen-grid resistors.

5. Wire -- important in a 5E3, since you want wire that will shape well and lie down neatly in that small space. Stateside, the two big winners seem to be either cloth-covered Fender-style solid core or 'topcoat' stranded/plastic wire where the neatly twisted strands are given a topcoat of tinning. Oh, and 22ga will work almost everywhere (I use PT cutoffs for B+ to the board).

Afterthought: Wire the AC mains Rob's way (with Oz wire colors of course).
Thanks for your reply King Fan so much gold here,

1. Is the layout I posted about the split ground scheme? I think I am going to go that way. I will likely experiment with the other two in future builds.

2. Thanks, that article is great and it you have clearly experimented with it. I will use metal film except in those spots.

3. Thanks I'll check this out. I think I will just leave the ground/standby switch disconnected - left for looks like on the stewmac kit?

4. That's helpful to know. I will start stock and be mindful of leaving room to add those mods.

5. That narrows it down well. Hmm, the cloth looks cool but I am guessing the top coat is easier and better to work with?

Rob's way has the fuse first? I remember reading about the shortcomings in Fender's design. Thanks again King Fan


You might want to reinvent the wheel but you don’t have to. The original circuit and layout from 1959 works just fine. Build to the original design and get to know it for a month or two before you modify.

Solid core cloth wire is easy to work with.

B+ will be too high with a new production 5Y3. Use a NOS 5Y3 to get the 360 volt B+ you need.
Thanks Ricky D,
Yeah I would love to keep in as close to the original as possible. In time I might make two, one I mod, and one I keep stock.

Thanks, I will try the cloth wire on my first build I think.

Hmm, I will try to chase one up. Is there any way around this?
 

geetah

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I agree -- I *mostly* wire my board to the Fender layout, upsize a few resistor watt ratings, then wire the grounds and AC mains like Rob. And except for power and safety update mods, the stock 5E3 needs a *long* shakedown cruise to learn both channels, all the interactive knob settings (hint -- sweet hides in the first 3-4 lines on the active volume dial, clean can involve 9-11 on the inactive dial, and many kinds of dirt, nicer and nastier, lie all around). Oh, and an extra month to check out jumper options... then you can mod with some idea of actual destinations.
I like your style. I am going to love this amp! Very exciting. Thanks for the hints. We haven't even began to discuss tweed cabinet covering yet :p
 

2L man

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Thanks 2L Man,

I think I am going to follow the standard layout Rob has on his site. I have printed this and the original Fender schematic and layout to get familiar with.

I am interested in the bleeder resistor if it doesn't affect the sound of the amp. I will dive into that when the time comes.

5e3_Deluxe_Amp_Layout_small.png
This layout make phase inverter and pre amp return current flow thru chassis! It is not good idea to make pulsating current flow thru amp input jack because guitar signal is lowest there AND amp will amplify everything the most what it get there. Also guitar cable is symmetrical source and this pulsating current comes to cold and it reach the guitar. Sign of this is that hum lessen when you touch guitar strings and then you act as a "ground" damping the noise from half of the instrument cable.

However it is very easy to fix and make amp also simpler soldering 1" of wire between second and third filter capacitor negatives and removing green and black wires from "power amp ground". Amp comes simpler when you get rid of more wire than this 1" you need for this simple improvement. Also one ground lug is not needed. But best feature is that amp hums less :)

Green wire the filament CT is good to elevate. Bleed resistor does not effect sound! If you don't want to use twomresistor circuit you can connect filament CT to power tube cathode resistor where about 20V is better than zero volts although there is some signal.
 
Last edited:

dan40

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Aug 19, 2015
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Notable parts in my cart:

F & T 22uf 500v caps
Carling SPST switches
CTS pots
Switchcraft jacks
sockets

Eyelet and backing board
Chinese import drilled chassis

Before you purchase the chassis, double check the dimensions on the Classictone transformers. Some of those Chinese chassis have different cutout dimensions.
 

pfarrell

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Great amp!
We built this version. Deleted the standby switch and put the NFB switch mod in it's place—which has a really nice effect on this amp, kinda "dirty, clean (stock), extra clean" thing happening. The power cut we use too. Have a Weber alnico in it. This build is freakishly quiet (shielded cables, 1 end grounded, for vols, NFB runs, inputs). You can't tell it's on sitting right next to it—fantastic versatile amp.
 

geetah

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This layout make phase inverter and pre amp return current flow thru chassis! It is not good idea to make pulsating current flow thru amp input jack because guitar signal is lowest there AND amp will amplify everything the most what it get there. Also guitar cable is symmetrical source and this pulsating current comes to cold and it reach the guitar. Sign of this is that hum lessen when you touch guitar strings and then you act as a "ground" damping the noise from half of the instrument cable.

However it is very easy to fix and make amp also simpler soldering 1" of wire between second and third filter capacitor negatives and removing green and black wires from "power amp ground". Amp comes simpler when you get rid of more wire than this 1" you need for this simple improvement. Also one ground lug is not needed. But best feature is that amp hums less :)

Green wire the filament CT is good to elevate. Bleed resistor does not effect sound! If you don't want to use twomresistor circuit you can connect filament CT to power tube cathode resistor where about 20V is better than zero volts although there is some signal.
Thanks 2L man, I will keep reading about grounding methods, but I am keen to keep things pretty much stock. The bleed resistor is a good idea and I will probably put it in.

Before you purchase the chassis, double check the dimensions on the Classictone transformers. Some of those Chinese chassis have different cutout dimensions.
Thanks dan40, I will check that before I order. The metal on the chassis I am looking at is thick and apparently hard to cut or drill through.

Great amp!
We built this version. Deleted the standby switch and put the NFB switch mod in it's place—which has a really nice effect on this amp, kinda "dirty, clean (stock), extra clean" thing happening. The power cut we use too. Have a Weber alnico in it. This build is freakishly quiet (shielded cables, 1 end grounded, for vols, NFB runs, inputs). You can't tell it's on sitting right next to it—fantastic versatile amp.
That sounds like a cool idea to utilise the unused switch. I will check out the NFB mod. What's the power cut about? The RobRob deluxe is great, I would like to build that one too.
 

King Fan

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@geetah, you are getting *so* much good advice here. Are you starting a 'build ideas and notes' file on your computer? By all means use cloth if you want. I do. But... if you want easiest and quickest to strip, the 'good' topcoat wins. Solid 'vintage' cloth is hard to strip neatly and tends to fray -- but it does hold shape and lie down even a bit better than topcoat.

In either case, you want to get 'the right stuff,' and I have no clue who carries it where you are. If you do go with cloth, a few hints for handling:

"Pushback" works, but creates a bulge of insulation on shorter runs, so better used under the board or for longer runs where the python can fully digest the pig.

You want good diagonal wire cutters and strippers. Even then, the inner white strands may 'hang out' -- tiny nail / iris / penknife scissors can trim them.

I buy a bottle of cheap clear nail polish at the grocery store -- the fast-dry kind -- and dab/blot/dry for 10sec before *and* after stripping/trimming. Prevents fraying.
 

geetah

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@geetah, you are getting *so* much good advice here. Are you starting a 'build ideas and notes' file on your computer? By all means use cloth if you want. I do. But... if you want easiest and quickest to strip, the 'good' topcoat wins. Solid 'vintage' cloth is hard to strip neatly and tends to fray -- but it does hold shape and lie down even a bit better than topcoat.

In either case, you want to get 'the right stuff,' and I have no clue who carries it where you are. If you do go with cloth, a few hints for handling:

"Pushback" works, but creates a bulge of insulation on shorter runs, so better used under the board or for longer runs where the python can fully digest the pig.

You want good diagonal wire cutters and strippers. Even then, the inner white strands may 'hang out' -- tiny nail / iris / penknife scissors can trim them.

I buy a bottle of cheap clear nail polish at the grocery store -- the fast-dry kind -- and dab/blot/dry for 10sec before *and* after stripping/trimming. Prevents fraying.
I know right?! I appreciate all the wisdom and experience here so much. Good idea - I just started a note on my computer and put the choices and considerations I face.

I'd love to go cloth for looks and to be 'PC' (period correct 😁) - I will just need some practise working with it. I can see 'pushing back' being tempting instead of stripping, and easily getting 'bulgy' in places. The topcoat seems like good stuff, that I can see myself using after the novelty of trying to be 'PC' wears off.


I think my wire cutters and strippers are ok, but I will check with you all before I start and show you my workspace (that needs a fair bit of work to tidy up 😬.

I searched google to find out more about the nail polishing to prevent fraying and found your process.


King Fan said:
  1. The right cloth wire -- I use Doug's which I think is Mojo's
  2. Really sharp diagonal wire snips
  3. Pushback; if you're dealing with enough wire to spread out the caterpillar
  4. O/W, high quality 22ga stripper
  5. Nail, iris, or Swiss-army penknife scissors to trim stray white inner threads
  6. A bottle of cheap clear nail polish from the grocery store -- apply after snip, before strip -- let dry 10sec, blot away with scrap of paper towel
  7. Polish, pinch, blot to 'touch up' any later fray from, ahem, excess handling...


It's hard to picture where/how you are applying as I have't dealt with the material and it's fraying, but I'm sure I will be able to once I start.

What are the reasons you use the cloth wire over the top coated?

Thanks!
 

King Fan

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What are the reasons you use the cloth wire over the top coated?
Sorry, I thought I said: it takes and holds shape even better. Sure, I like the vintage look of the cloth, but I especially like the look of the neat wire routing in the original Fender amps. Topcoat is at least 95% as tractable, but it's a bit fatter and the plastic jacket is a bit stiffer.

And sorry if I'm not being, um, clear about the clear nail polish -- I only apply to the small area I'm going to cut or strip and blot off excess. I just want to stiffen the cloth to avoid fraying. Not a big deal -- here's before I adopted nail polish... (*but* note the evil whisker of stranded wire -- this stuff can make crazy noises and dangerous shorts -- compressed air is your friend).

1649610604572.jpeg


Here's a later amp with nail polish (the burnt bit? swapping out coupling caps). Not a huge difference.

1649610763717.jpeg
 

geetah

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Sorry yes you did say that - which makes sound like a good choice. Thanks for those pictures, it all makes 'clear' sense now! The polish really tidies those ends up on the cloth.
 

pfarrell

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That sounds like a cool idea to utilise the unused switch. I will check out the NFB mod. What's the power cut about? The RobRob deluxe is great, I would like to build that one too.
Here’s @robrob page with 5E3 mods. several power cut options. Push the amp to breakup at lower volumes.. great for in the house at times…and practice…
 

geetah

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Here’s @robrob page with 5E3 mods. several power cut options. Push the amp to breakup at lower volumes.. great for in the house at times…and practice…
Thanks pfarrell, I have checked this out at Rob's page before. So many useful mods.

I am going to make a nice stock version first with tweed covering. Then later on down the track, I would like the build another with all the mods, probably uncovered. A rat rod :).

As for home, practice and very small gigs - the 5f1 will be the next project.
 

geetah

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So at this point I have a chassis, eyelet board, caps, knobs, jacks, wire, sockets, lamp, fuse etc. in the mail.

I need to clear out a space to build it. I am in the process of setting up my shop so this project should give me a kick to get it done.
 

pfarrell

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I made 2 5F1s (first guitar amps ever)... one was a gift, we tried them with a greenback and a Weber alnico (12" speakers) blind A/B, we all had different opinions but my daughter and I liked the greenback—both were fantastic though. Definitely DO NOT use the power switch plus volume pot part per the original design... Of course do exactly what you want—that's just my opinion—but the amp got 100% quieter after I split those functions. It's totally worth building—sounds great—and different from P/P in my opinion. It's unique, we love it. We have thought about adding a tone pot just cause.
 

geetah

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Thanks for the heads up, I have a vox ac15 with a greenback I can test it with when the time comes. The volume/power switch has sure got me reading, thanks!
So many amps, so little time ha ha.
While I am waiting for my parts I am checking other people's threads, and studying sites like Rob's, Hoffman and Geofx.
 




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