Tools for building an amp?

Engine Swap

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I can understand how a Variac could help as I get farther down the line and start designing on my own, same as an oscilloscope, but why do you suggest those as requisite tools from the beginning?

Additionally, I have a load resister (8ohm headphones) and signal generator (guitar) already. Is there any reason not to use these and to get something specialized instead?

If you aren’t going to make any errors in your build, then you won’t need a scope.

If you are going to apply full power to the build, that has no errors, then you won’t need a variac.

What is the wattage of your headphones? (asking for a friend)

Test the amp using the guitar as a signal generator and get back to me.
 

Will_Darden

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If you aren’t going to make any errors in your build, then you won’t need a scope.

If you are going to apply full power to the build, that has no errors, then you won’t need a variac.

What is the wattage of your headphones? (asking for a friend)

Test the amp using the guitar as a signal generator and get back to me.

What I hear you saying is that I’ll need these things because I’ll make mistakes but that doesn’t tell me how I need to be prepared to use them. If you’re not up to answering that question that’s cool.

I’m putting myself out there asking honestly for advice and I feel like you’ve belittled me for asking.
 

corliss1

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I general, I just don't see how a scope or signal generator would help a beginner. Even with a lot of amp work, I don't use a scope a whole lot. I like a signal tracer tool, but some guys live on the scope - just different methods.

A light bulb limiter can be made for $10-20 and takes the place of the variac for proper startup procedures.
 

dogmeat

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I would add a capacitor meter of some kind. takes out all doubt when sorting a bag full of caps. also good for testing old ones when doing repairs. meters like this one are 20-30 bucks on evilbay

1643572131544.png
 

Engine Swap

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What I hear you saying is that I’ll need these things because I’ll make mistakes but that doesn’t tell me how I need to be prepared to use them. If you’re not up to answering that question that’s cool.

I’m putting myself out there asking honestly for advice and I feel like you’ve belittled me for asking.

Seems like you have and know everything you need - best of luck
 

Milspec

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My toolbox only has a checkbook and a pen in it.

I would like to be able to DYI an amp, but after being struck dead of lightning (twice!), I do not like electricity all that match. Just hearing the hum when I power up my Twin makes me sweat.
 

owlexifry

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interesting how tools for building, and tools for diagnostics/troubleshooting, have been lumped together in this thread....

as a beginner, the fanciest tool you'll need to get started is a decent multimeter.

for building, minimum:

-soldering iron
-side cutters / wire cutters
-a really good wire stripper
-small needle nose pliers
-"lead wrapping pliers"
-step drill bit (if drilling own chassis)
-something to firmly mount the chassis on
-usual hand tools for dealing with hardware (nuts, bolts)
- 'snuffer stick' - for discharging filter caps


the only thing I ever needed a scope for, was to determine/confirm the 'outer foil' lead for coupling caps. (i used a cheap <$100 digital one)

slapping power on a new amp build, without a bulb limiter or variac, shouldn't be an issue if the filter caps are of good quality and brand new.
(assuming you're sensible and triple-check all leads/polarities are 100% correct before doing so)

if you're dealing with old/used/NOS(?) filter caps, well... maybe not...
 

SerpentRuss

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I can understand how a Variac could help as I get farther down the line and start designing on my own, same as an oscilloscope, but why do you suggest those as requisite tools from the beginning?

Additionally, I have a load resister (8ohm headphones) and signal generator (guitar) already. Is there any reason not to use these and to get something specialized instead?
Personally, I find a signal generator very valuable. I have always used an app for this, with a 1/4 inch to 1/8 inch adapter so I can plug it from my phone's headphone jack into the input jack of the amp I'm working on.

Here is the reason for using a signal generator. A guitar is a complex audio signal with decaying amplitude that will confuse a multimeter's AC voltage reading. Most meters aren't going to give you an accurate AC measurement while you strum your guitar and an accurate reading is still going to be all over the place. You can't strum consistently AND it ties up your hands.

If you want to chase a signal through your amp, having a nice steady 50 to 100 mv sine wave adjustable for various frequencies is extremely helpful. Using a signal generator in conjunction with an AC voltage reading will tell you if your gain stages are working correctly. You can see how that bright switch changes your response at 5K. You can see how that icepick cap in your feedback loop filters out highs at our speaker. You can see how much your tone stack attenuates the signal at different frequencies by measuring before and after. I have used a signal generator app for commissioning the half dozen projects that I've completed. The downfall of a phone is the voltage does not seem to be constant across frequencies and varies with charge. I would like to have a better resource so I'm watchin eBay for an old audio function generator.

Where a scope comes in handy is looking at waveforms, distortion, phase inversion, phase inverter balance, etc. Are you cold clipping? Hot clipping? If you have two channels you can find out if your PI output is balanced. I don't own one. I sold mine years ago before I started this hobby and could shoot myself now. I have two very good graphing meters that are identical, so I can get by... sort of.

At any rate, you don't need a scope. The signal generator is practically free, you just need a PC or phone and a cable.

Here is the one I use. This guy has a windows app and a phone app.

 

corliss1

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Totally useful, but if I first-timebuilder is doing a known circuit, like a Champ or Princeton or Deluxe, we shouldn't have to get to the point of "I need to trace AC voltages through each stage." 99.9% of the time, checking plate and cathode voltages will get us where we need to go.
 

Will_Darden

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Personally, I find a signal generator very valuable. I have always used an app for this, with a 1/4 inch to 1/8 inch adapter so I can plug it from my phone's headphone jack into the input jack of the amp I'm working on.

Here is the reason for using a signal generator. A guitar is a complex audio signal with decaying amplitude that will confuse a multimeter's AC voltage reading. Most meters aren't going to give you an accurate AC measurement while you strum your guitar and an accurate reading is still going to be all over the place. You can't strum consistently AND it ties up your hands.

If you want to chase a signal through your amp, having a nice steady 50 to 100 mv sine wave adjustable for various frequencies is extremely helpful. Using a signal generator in conjunction with an AC voltage reading will tell you if your gain stages are working correctly. You can see how that bright switch changes your response at 5K. You can see how that icepick cap in your feedback loop filters out highs at our speaker. You can see how much your tone stack attenuates the signal at different frequencies by measuring before and after. I have used a signal generator app for commissioning the half dozen projects that I've completed. The downfall of a phone is the voltage does not seem to be constant across frequencies and varies with charge. I would like to have a better resource so I'm watchin eBay for an old audio function generator.

Where a scope comes in handy is looking at waveforms, distortion, phase inversion, phase inverter balance, etc. Are you cold clipping? Hot clipping? If you have two channels you can find out if your PI output is balanced. I don't own one. I sold mine years ago before I started this hobby and could shoot myself now. I have two very good graphing meters that are identical, so I can get by... sort of.

At any rate, you don't need a scope. The signal generator is practically free, you just need a PC or phone and a cable.

Here is the one I use. This guy has a windows app and a phone app.

Thank you for your detailed explanation. That was really helpful!

I can see where generating a static tone would be really good. I can also see where pushing that out of speakers could get really irritating really fast -- which explains the need for a resistance load.
 

The Ballzz

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Light bulb limiter can save components and frustration. An amp cradle is very handy, cheap and easy to build, if you are semi-versed in wood working!

IMG_1975.jpg

IMG_1976.JPG
 

Will_Darden

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Since there's been a lot of discussion so far, I'm going to sum up as much as I can so far.

Nice wire stripper like Hanlong HT 5023R (my favorite)
Helping hand fixture
Needle nose pliers
Flush cutter
Hemostat with holding catch
Step drill bit
Dentist pick for undoing wires when soldering
Maybe a sheet metal nibbler
Maybe a couple 50w 8 ohm dummy load resistors
A frame (can be homemade) for supporting the chassis at a comfortable angle.
Automatic (spring loaded) center punch for piloting holes.
Chassis punch for tube base holes
A second multimeter
set of small machine taps
machinist tri square
I have a lot of this stuff from my great grandfather's toolkit -- he was a pipe fitter. I cannot tell you how much I swear by his measuring tools which are undoubtedly 100+ years old and still use them in my woodworking projects. Since I have a basic MM I'll probably get a second one that's nicer along with a couple of the other hand tools you mention. Thank you for the specific recommendations!

The dentist pick in particular is brilliant. I had often used a black stick (one of those plastic soldering tools), but they're not terribly precise.
-Flux. No Ko Rode. Helps immensely for soldering to chassis or pots etc.
-Solder sucker (The piston type not the rubber bulb type)
-A good set of Dikes.
-Good needle nose pliers, short and longer. Make sure the tips align well when closed.
-A good stapler for tolexing etc. The T10 works fine with 5/16" staple length.
-You will want a bias tap (inserts into a tube socket) for ease of biasing. You can do without it though. They are cheap.
-Your multi meter needs some long leads and alligator ends to attach. Some cheapies have very short leads.
-Your multi meter needs to read Milliamps for biasing. Many dont.
Bias tap and piston-type solder sucker added to the list. Stapler I have, but I'm still reading up on wood cabinets (esp solid wood vs composite/ply) and may want to do something nicer. I have some old wood cabinets with solid veneer that look amazing and could make for an excellent speaker / amp cab as long as they're not unduly influencing the tone. Being from Portland, it would be fun to find some PDX Carpet tolex for a smaller project. One of my projects is converting an old organ into an amp/cab setup. Would likely use the wood from that to build.

I've always called Dikes "nippers" and they're definitely on the list of hand tools I'm going to get.

All of the electronic solder I've used is rosin-core and I was advised *not* to use flux. Why do you recommend it?
Deep well nut driver sets are nice for installing pots.
Flush cut wire cutters.
Magnifying visor is a game changer for soldering in tight confines.
A resistor, wire, ink pen, and alligator clip to make your own capacitor drain tool.
A small hobby vise for the times when you need 3 hands.
I have been wanting some nut drivers with deeper wells. Maybe now is the time. I'm horribly nearsighted so I might forego the magnifying visor or just use my readers for when I have my contacts in. That said, I believe my dad may have a pair he uses for lapidary work.

I've also seen a lot of recommendations for the following:

- Light bulb limiter and/or Variac (thank you to everyone for your explanations of usage -- I can now understand why these are both helpful and why the Variac might be a better option on later builds. The limiter is going in my project list right away. and if I want something more granular, I can upgrade to a Variac.
- 8Ω 50W load -- thinking this might be a fun project build but they're so cheap I might just buy it.
- Oscilloscope -- sounds like this is for some pretty granular testing. Going on my "maybe" list.
 

Greg70

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Also, please wear safety glasses when cutting the excess lead wire from components and when testing electrical circuits. The cut wire ends tend to fly across the room. If you short circuit something while testing they can tend to explode. Neither is good for your eyes.
 

schmee

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Since there's been a lot of discussion so far, I'm going to sum up as much as I can so far.
Bias tap and piston-type solder sucker added to the list. Stapler I have, but I'm still reading up on wood cabinets (esp solid wood vs composite/ply) and may want to do something nicer. I have some old wood cabinets with solid veneer that look amazing and could make for an excellent speaker / amp cab as long as they're not unduly influencing the tone. Being from Portland, it would be fun to find some PDX Carpet tolex for a smaller project. One of my projects is converting an old organ into an amp/cab setup. Would likely use the wood from that to build.
All of the electronic solder I've used is rosin-core and I was advised *not* to use flux. Why do you recommend it?

I have been wanting some nut drivers with deeper wells. Maybe now is the time. I'm horribly nearsighted so I might forego the magnifying visor or just use my readers for when I have my contacts in. That said, I believe my dad may have a pair he uses for lapidary work.
I've also seen a lot of recommendations for the following:

- Light bulb limiter and/or Variac (thank you to everyone for your explanations of usage -- I can now understand why these are both helpful and why the Variac might be a better option on later builds. The limiter is going in my project list right away. and if I want something more granular, I can upgrade to a Variac.
- 8Ω 50W load -- thinking this might be a fun project build but they're so cheap I might just buy it.
- Oscilloscope -- sounds like this is for some pretty granular testing. Going on my "maybe" list.
I just find it simplifies soldering. Allows you to not use too much heat on pots etc. I've used it for 40 years.
It also will help if you are trying to desolder old things like the Organ amp you mention. Some of those old Hammond amps just wont even melt with a 40 watt iron! One tiny hint of flux and ouila! it flows.

If those old organ cabs you're talking about are Hammond. It's very cool "ply" they used. It's a hardwood core of maybe 5/8" solid wood and a veneer on each side of maybe 1/16" making 3/4" total. Not plywood, and solid as heck!

I have three empty cabs and some amps out there right now.
Better take a drive up sometime, I'll give em to ya.
 

sds1

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All of the electronic solder I've used is rosin-core and I was advised *not* to use flux. Why do you recommend it?
Flux is awesome. You were maybe advised not to use a corrosive flux, as is used in plumbing and other commercial applications? Or maybe that was the intent of the advisory. Otherwise I can't think of why a warning about flux would be issued, like you said it's already in the solder we use...

You want to get a no-clean flux meant for electronics. Stay way from rosin flux, it's a mess. No-clean solder isn't actually no-clean, it should be called "can-clean" IMO because it in fact does leave behind a tiny mess... but can (optionally) be mopped up completely with 99.9% ISO*. This is like your cheapest Amazon option here, the flux itself is great but you have to be careful not to wear down the tip:

Chip Quik CQ4LF Liquid Flux No-Clean in 10ml (0.34oz) Pen w/tip

(ad-blocker must be disabled to view the Amazon link below)



I use flux like @schmee does, it's like a super-boost to the soldering process when you need it -- when you need to get in and out of the joint ASAP (so you don't overheat the board, the insulation, etc), when there's a a lot of heatsinking working against you (like [de]soldering to chassis or other large pieces of metal), working on ancient or leadfree solder, etc. I also will sometimes load up a blob of solder on the tip of my iron, then transfer to joint prepped with flux -- the solder will flow from iron to the joint real nicely. This technique I use when I need my other hand to hold a wire in place...

I now always add flux to solder wick, the wicking action is superior compared to without.

Joints with a little help from flux are always so shiny! IMO it would not be a waste of time to use flux everywhere...

* add 99.9% ISO to your list! I don't remember seeing that mentioned...
 

VintageSG

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Masking tape.
If you start doing PCB or Vero builds, insert a row of components, then masking tape the buggers to the board. They don't fall out when you invert the board, a bit of heat isn't an issue, and it leaves no residue.

Hilighter pens.
When you complete a section of wiring, or add a few components, meter them for sensible purposes. Double check then, write any applicable values on your schematic, then go over the schematic with a hilighter to show you've done and checked each connection.

A 'phone with a decent-ish camera. Photograph each stage in close up. PSU, pre-amp, tone stack, inverter, output stage, transformer wiring. You now have a reference. The schematic and the photographs.
 




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