PCB's v. Hand Wired Amp Construction: The Real Deal

LEFT: Eyelet Board hand-wired construction / RIGHT: PCB hand-assembly construction

I hear a lot about the debate between PCB's and "hand-wired" eyelet or turret board construction. So I thought I would give you some real info, and fill you in on fact v. fiction. For starters, what are these things? Well, every amplifier has electronic circuits. They are made up of resistors and capacitors (and a few other electronic components). Rs&Cs go into the circuit such that the electronic signal passes through the R or C and gets altered. Hence, they go "in line" much the same way that water passes through a water filter before making it out of the faucet. But there's a fair number of them in line in your amplifier so there has to be some way to connect them all together. There's basically 4 ways to do it.

1) PCB (Printed Circuit Board). Here, the designer/engineer has laid out the circuit in the desired manner. The "traces" are like your wire that connects everything (the water supply line) and there are holes where all the components go so that they go in the exact same place every time. See Image 1 (A).

2) Hand-wired (no board of any kind). Here you see a lot of wire tying everything together with all the necessary components cut in where they go. It is very time consuming, but essentially the wires take the place of the "traces" on a PCB, which are the same as the wires, but laminated inside the board. Hand-wired can look a bit like spaghetti. See Image 1 (B).

3) Eyelet or Turret Board. This is a "board" with eyelets down each side (holes) that you can place the components in, then connect them together directly, or use wire on the underside of the board to do so. A "turret" board simply replaces the eyelets with "turrets" that stand up off the board instead of the thru-hole eyelets. See Image 1 (C) Eyelet (D) Turret.

4) Breadboard. If you're old enough, you may remember "Lite-Brite" kits. Well, that's a breadboard. If not, it's a bunch of holes that you can use to "layout" your circuit. It's really used for prototyping and never used for stable, long-use production. See Image 2.

cont. . .

Image 1. (A) PCB, (B) Hand-wired, (C) Eyelet board, (D) Turret board

Image 2 - Prototyping Breadboard

Why do amp designers choose 1 over the others? Oh, who knows. But here's the general reasons. Let's start with PCB's. In the old days, PCB's weren't around. Ok, so skip that one. But now they are. Why use it? Advantages: Well, if you make more than a few, it cuts the assembly time down immeasurably. Second, it is FAR FAR FAR more stable long-term. It creates a tested platform that is stable and ensures everything goes exactly where it needs to, every time. Further, it radically limits the margin for assembly error. If you leave a component out, you can see it by simple glance at the board. Further, it radically limits the probability of bad solder joints, wires that become disconnected, etc. Drawback? Well, there's some engineering involved. You have to know how to lay it out, program it in and then they have to be tested for trace proximity causing noise, oscillation etc. You have to know the size traces to use, construction method etc. Many people don't. So they're scared of it, or are a smaller designer and don't have the time or available tools to do it. 

Next to fully hand-wired. Advantages: Only the voodoo that there seems to still be some mysterious allure to "hand-wired" amongst guitar players as if they sound better because someone did it all by hand. In the end, it's the same components, same circuit. If I do the job correctly as hand-wired, and did my job correctly on a PCB, there will NOT be any sonic difference. Let me say that again, there will NOT be any sonic difference. It's like making a guitar body - on a CNC, they're the same every time. By hand, it can be the same, but either way, the guitar isn't going to sound better if you took 3x longer to cut it by hand, provided it's the same quality wood, etc. I had to buy a new mattress the other day. I found 2 identical ones. Same construction, coils, etc. One was $1000 more. I asked why. They said it was "hand-made," as if THAT is important in a bed. People used to think that the hand-wired nature of amps is why they had such sonic differences, even among models. Essentially, the thought was that old-school Marshalls sounded different from amp to amp of the same model because they were hand-wired. Well, no. In those days, you couldn't find components with much less than about 10% tolerance. If you have 2 and one is 10% higher and the other is 10% lower, you have a 20% difference. Nowadays, we can get 1% components. So the sonic variance is much less. Drawbacks: Takes forever to make it, thereby increasing cost due to radically increased time. As well, it significantly ups the margin for assembly error.

Eyelet/Turret Boards. Kind of a nice middle ground in a way. You sort of shorten the time involved. You sort of reduce the margin for error. But they are not good for more complicated assemblies, which is true for nearly every channel changing amp. Since they lay out in a line, on more complicated builds you may have a railroad tie-sized 2-channel amp. LOL. 

So here's the real deal. NONE of these methods will make your amp sound better or worse on their own. What does make it sound better or worse is a few things and only a couple of them have anything to do with the assembly method. Here's a non-exhaustive list:

1) Um, circuit design and transformers. That's number 1) for a reason.

2) The quality of the components. Nothing to do with assembly methods. You can use good or not-good components on any of these assembly methods.

3) Was it put together properly. Well, this can be greatly affected by the assembly method.

4) Did the designer layout the assembly or PCB correctly.

What is the best choice? Well it depends. At Diamond, we use the PCB because we've tested and tested and tested our designs. And they've had MASSIVE road testing. So we KNOW it's stable and it reduced assembly time as well. If we were only making a few, we probably wouldn't spend the extra R&D time to develop the PCB and just go hand-wired. But by only a few, I mean like 10. Anything more, develop the PCB. We've chosen eyelet boards on some of our older Class A more vintage designs, but they were simple, low-wattage amps that didn't require as much, so we used the eyelet boards and had to put everything through extra testing to avoid field failures. 

What's the best choice for you? Well, the one that sounds best in your rig, but also one that has a track record for reliability, and most hand-wired amps do not (some do, however so it's not a universal rule). Do not choose your amp on the assembly method, or even be swayed by it. It will make no difference to your ear or the ears of your many fans. Choose on sound, then reliability. Just about everything else has more affect on your amp's tone than the assembly method. 

Hope this helps.

THE INTERPLAY OF VOLUME AND GAIN - all new tones!

The interplay between the volume and gain dictates your tone more than any other controls.  As with any amp, the gain control dictates the amount of saturation, break up or distortion of the channel.  The higher the gain, the more the channel distorts. Think of it like a car, the more you press down on the gas, the more then engine turns over, hence, the car goes faster.  Well your pickups are your gas pedal.  The hotter the pickup, the more crunch you’ll get out of the amp.  So, with a low output (maybe, say, a single coil), the more sweep you have on the gain knob before the amp will start to provide more crunch. For us metal players, our super high output pickups will cause this channel to distort much more quickly.

For gain settings, generally your cleaner tones will be lower on the gain knob and the higher you run it up, the more crunch you’ll get out of the channel.  But volume and gain interplay.  Assume you dime the gain, but set the volume to 1.  You’ll hear the distortion, but not like you want.  As you roll the volume up, the true tone will emerge.  

Keeping with our analogy, think this time of the gain as the gas pedal.  How many times have we raced go karts as a kid?  Can you remember mashing the gas pedal as hard as you could but the go kart just didn’t want to go as fast as you wanted it to?  Well often those go karts came with some sort of governing device.  You can put the proverbial pedal to the metal, but the kart will only go so fast.  So dime your gain.  But when it’s not fast enough, open up that governor by introducing some volume.  As you bring up the volume and heat up the channel, mashing that gas pedal starts to really get that machine moving.

When deciding how to run your volume/gain settings, try some things first.  Bring the gain up to around 7 and volume to around 3.  After you’ve made mental note of the tone, start rolling that volume up and listening for the tonal changes (although you’ll assuredly also hear volume changes).  When the volume hits around 6 or 7, you’ll really hear a difference from the tone when the volume was on 3.   Now let’s reverse it somewhat.  Bring the gain down to 2 or 3 and set the volume at 3.  Rinse and repeat.

What will we have learned?  Most likely, this test will have resulted in few observations:  (1) the tone is brighter, tighter and punchier when the gain is down on the gain channel; (2) the tone is cleaner and rounder when the gain is down on the clean channel; (3) the tone is mean and nasty when the gain is up on the crunch channel; (4) the higher the volume, the fuller the amp is and the more punch you’ll get from the channel; and (5) there is a lot you can do tonally by simply varying these two controls.  So don't just treat them like discreet controls - gain = distortion and volume = volume.  Realize they both affect your tone and experiment with them!

SO YOU WANT IT MAS QUIET? A WORD ON ATTENUATORS

Seems like a good place to start.  It's a question I get a lot.  "I want to play my amp at a lower volume, but get the same tone.  How about an attenuator?"  OK.  Let's start with what an attenuator does.  Simply, it goes between your amp and your cabinet, allowing you to turn your amp up to get all the preamp and power amp tone or distortion out of it, then lower the volume before it gets to your cab.  Some people prefer it because it let's you get that power tube gain but running the amp really hot, then simply stepping down the volume.  

So the question is, will your tone be the same?  Simple answer:  No.  Why not?  Well, it does "preserve" the tone of your amp.  But your guitar sound is a combination of a lot of things, and a HUGE part of that tone is your cabinets and speakers.  For a lesson on the importance of your cab and speakers, check out the videos page and watch the episode entitled "A Dissertation on Cabinets and Speakers."  But when you use an attenuator, you aren't driving the speakers as hard, so you move less air and as well, the breakup of your speakers (or at least their tone that's created from physically driving the cone).  So while it's better than simply using the master volume on your amp if you're trying to preserve your tone, it will never be the same - just closer than turning the volume down.  

Now, if you're going to use one one, get a good one.   Because of what an attenuator does, it is necessarily impacting the load your amp is seeing (or needing to see) from the cabinet.  So the attenuator also has to supply the correct load or you can fry your amp.  Make sure, therefore, that you get one that is rated at the correct impedance for your rig.  As well, make sure that the attenuator you purchase can also handle your amp.  I have literally seen attenuators smoke output transformers because the attenuator wasn't rated to handle the plate current rating of the amp.  Remember, when an attenuator creates the load for your amp, it's literally doing that through the equivalent of a big resistor.  If that resistor can't handle the load you're putting on it, it can cause it to fail, thereby leaving your amp without a proper load. 

Side note, one place attenuators can be very useful is home recording.  If you can't turn up at home, the proper attenuator can help a lot. . .

CHANGING YOUR TUBES (way more frequently than you think. . .)

Since we're on the subject, let's talk about changing your tubes. . . 

Preamp tubes have a much longer life than power tubes.  You are not likely to have to replace them unless one or more tubes fail.  Preamp tubes can have a life span of at least two to three years and usually much longer.  If it’s been a few years or you regularly change your power tubes and feel like the amp has become lifeless, it may be time to freshen up your preamp tubes. 

If you play regularly, power tubes should be changed every 6 months to a year.  If you don’t play frequently, they can last longer.  NOTE:  While power tubes can simply and suddenly fail, they generally degrade over time.  So while your tubes may be working, they will not sound the same as they get older.  People often go years with the same power tubes and never replace them claiming, “Well, they still work fine.”  You can be assured that the amp, however, does not sound the same as it does with new, functioning tubes.  DON’T WAIT UNTIL YOU HEAR A DIFFERENCE.  FOLLOW A REGIMENTED TUBE CHANGING SCHEDULE TO AVOID HEARING A DIFFERENCE.

When it is time to change power tubes, bias should always be checked.  It is easiest to have a qualified tech retube and rebias your amp. 

What is a buffer and why are they used?

For a quick and inexpensive buffer option - check out the Kill Switch Plus!

Here's a great excerpt from Bob Bradshaw on buffers.  Everyone should know this.  FYI - the Diamond Amps Kill Switch + is an affordable, easy to get buffer and also acts as a kill switch, signal splitter and always on tuner out for on the fly or silent tuning. . .  Find it here!

Buffers are extremely important in a multi-component system. They are often misunderstood and often get a bad rap by those who are uninformed. In a CAE system, a buffer is a unity gain (input level equals output level) impedance converting circuit. It essentially protects your high impedance guitar output (or any other high impedance source, such as an amps' effects loop send) from being loaded down by the input it is connected to. In effect, it converts high impedance to low, which means subsequent stages are then driven by a low impedance source (the buffer's output). High impedance sources such as your guitar's output (assuming you have passive pickups) has very little current drive capability and it's signal is subject to a harsh environment once it leaves the guitar. You already know the adverse affect a long cable has on your tone. Same thing happens if you pass your signal through a bunch of effects pedals. Even if they have "true bypass" (an ugly, over-used term), each one will suck a little more of your signal along with the cables and connectors, mainly due to capacitive loading of your high impedance guitar signal. The end result is a muffled weak signal that lacks clarity. But once your high impedance guitar signal hits a properly designed buffer with a high input impedance, the buffer takes over, and uses its higher current capability (remember, its an active circuit that requires a power supply) to drive all subsequent stages, thus preserving your instrument's tone. This brings us to buffer quality. Buffers come in all types of designs, from discrete transistor, op-amp, to esoteric tube designs. All have their own unique sonic stamp. At CAE we use the op-amp approach. It has served us well for years, is low noise, and is extremely transparent to our ears. Buffers often get blamed for causing an overly bright sound, but we feel if its designed properly, any perceived "brightness" is because now the guitar is not being loaded down by subsequent stages!

Buffers can cause problems, too. There are some effects devices that don't like to see the low output impedance of a buffer. These are typically discrete transistor designed fuzz circuits (such as the Dallas Arbiter Fuzz Face). They react better to the high impedance output of the guitar. In fact, the guitar output, cable and input stage of the Fuzz Face complete a circuit that is highly dependent of those 3 components to work correctly. Fuzz Faces clean up nicely when you roll back the guitar volume control... not so if a buffer is between the guitar and Fuzz Face input. So if you have a pedal board with a Fuzz Face on it , put it first! Other pedals may react the same way. Experiment to see what works best for you. Keep in mind all active pedals (such as Boss, Ibanez, etc...) act as buffers and will impart their own sonic stamp even when bypassed. This is what started the whole "true bypass" (ugh! that term again) craze. See? Too much of a good thing can be "bad". Which brings us to how we utilize buffers in CAE custom switchers. We only use buffers where absolutely necessary. Typically, in a pedal based system we will not buffer until after the first 4-5 loops, which is usually just prior to sending the signal down to the pedal board (via a long cable run, hence the need to buffer) to hit the wah/volume pedals. Any more than 4 or 5 loops, and the guitar signal may be affected by capacitive loading. So the first few loops is where you would put any impedance sensitive effects. This also means your guitar will go through fuzz, overdrive or distortion pedals BEFORE the wah. We prefer this order because the wah then has a more harmonically rich signal to filter. Try it yourself. Of course, if a specific order is required, we will do everything we can to make it happen. Buffers are also necessary to drive isolation transformers, since the relatively low primary impedance of the transformers may be detrimental to whatever circuit is feeding it. This is also why amp splitter circuits must be buffered. You can't drive multiple amps with a relatively high impedance source. So there usually is a buffer somewhere in the output stage of your custom switcher. That's usually it. 2 places minimum. There may be more active stages depending on your system requirements.