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. . .

DIAGNOSING TUBE PROBLEMS

Most tube amp problems relate to the tubes themselves.  After all, tubes are not the cutting edge of technological advancement.  Tube problems are not infrequent occurrences.  But before you have to worry about shipping your amp for repairs, learning to diagnose a tube problem can keep you rockin’.  

I can not stress enough the importance of changing tubes to keep your amp running optimally.  But even with regular maintenance, you can still have tube problems.  If you are playing out regularly, I suggest you keep a spare set of power tubes in your gig bag and maybe a few preamp tubes just in case.

Crackling, squeals and feedback, excessive noise and muddiness or low output are all evidence of tube problems.  

Power tubes.  The two main symptoms of a power tube problem are a blown fuse or a tube that begins to glow cherry red.  Either are typically indicative of a power tube failure.  Some failures can be an intermittent short and some can be a tube failure.  If you blow a fuse, replace it.  If it happens again, replace your power tubes.  If the tube glows cherry red, shut the amp off immediately.  As power tubes are wired in pairs, a failure of this nature in one tube can cause the other tube in the pair to fail with it.  If you encounter this problem, as noted, shut the amp down immediately.  Wait a few minutes and fire it back up.  If it happens again, replace the tubes before using the amp again.  If not, you should probably still replace the tubes soon, but you should be able to operate the amp for a short period of time.

In the event you have one or two power tube failures, you can replace that one tube or two tubes to get you through a show, but then replace all four with a matched set (see the preceding section).

If you are hearing noise and/or crackling, you can rule out (or in) a power tube with a simple test.  Gently tap on the power tubes, one at a time.  They should not make noise.  If noise changes with the tapping, you may have a failing power tube.  Always be prepared to shut the amp off in case you have a failing tube and the tap causes it to short.  If so, shut the amp off immediately and replace the tubes.

Preamp Tubes.  Preamp tubes usually cause problems through noise or microphonics.  If noise, you will hear hiss, crackling, popping or similar issues.  If you hear squeal, hum or feedback, it is typically a microphonic tube.  Noise from microphonic tubes will typically increase with a volume increase.

To diagnose which tube is bad, if you have a two channel amp, the most important thing is to determine, if possible, whether the problem is on both channels or just one.  If you can tell that it is in both channels (even if only slightly on one channel), it is most likely V1, which is common to both channels.  A noisy or microphonic tube in this position will affect the entire amp.  Microphonic or noisy tubes in several other positions may not be audible at all.  You can try tapping the tubes like you did the power tubes and see if the problem worsens.  It is normal to hear a slight ring when you tap on preamp tubes.  This test is only to see if the identified problem changes when tapping.  This test is NOT outcome determinative.

If the problem is only on one channel or the other, you’ll know which tube is the problem.  If it’s only on the clean channel, it’s usually the tube dedicated to that channel.  If it’s on the crunch channel, then you've narrowed it down even further.  NOTE:  V1 usually is the culprit.  Even if you don’t hear it on both channels, you should check V1 anyway.  Tube problems are much more dramatic on V1 than any other position.  When you think you have determined the culprit, put the amp on standby and change that tube.  Retest.

NOTE:  It is always advisable to change preamp tubes one at a time.  It is a good idea to keep at least one known good preamp tube for this purpose.  Then you will know for sure if you have found the problem.  Having a know, working reference tube (or better yet, a set) makes life much easier.  PS - it's helpful to number the tubes before testing.  People OFTEN get them confused and simply keep moving the bad tube down the line, thereby mistakenly thinking it's not a tube problem.  So change them one at a time.  If it doesn't resolve the issue, put the tube back into the position it came out of, then move to the next tube.  It'll save you a lot of headache. . .

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. 

10 Easy Ways to Improve your Tone for Under $10

1)  Try a new pick.  Yes, a pick can change your tone.  Try thicker or thinner as well as different materials.  Rumor has it that Billy Gibbons got his tone using a Mexican Peso as a pick.

2)  Change string gauge/type.  Coated v. uncoated, and different materials can quickly change brightness, punch and related tonal properties.  Changing gauge can add thickness or bottom end to your tone as well.  Remember, changing gauge requires neck AND intonation adjustments.

3)  Vary your pickup height.  Back your pickup down even a turn or two and you can add clarity while slightly reducing output, which changes how your amps sounds as well.  Bringing your pickup up can add output and gain, but watch out for feedback if you get the pickup too close.

4)  Re-dial your amp!  Turning the knobs is a great way to change tone of course!  Remember, the guitar is a predominately mid-range instrument.  Suck out the mids and you suck out the key frequencies of your instrument.  Don't "dial with your eyes."  The numbers on the dials are kinda arbitrary.  Not all amps are alike and just because you think it should be dialed a certain way doesn't mean it should.  Mids are critical, gain is best when rolled back for a thicker sound and as important, understand the difference between presence and treble!  Remember - vary the volume and gain to get different tones.  See my other post on the relationship between volume and gain here:  

5)  Eliminate all your effects.  Most pedal boards or rack systems will eat tone also if they're not set up properly.  So take them out for a while and get all your tone back.  Then start to add back in only what you NEED.

6)  Double your tone.  Use your delay pedal and just add a quick, single repeat, slap-back delay.  It creates the effect of two guitars.  Don't put this in your loop.  Drop it in front.  The delay time should be something very short.  You're not trying to hear the echo so much as create the feel of two guitar players playing at the same time.

7)  Change the volume pot in your guitar.  Varying values can wildly change the way your guitar sounds.  Many hum/hum guitars come standard with a 250K pot.  Using a 500K can create a very different feel.  If you play with EMG's, try chaining the 25K pot for a 250K and get a warmer, more organic sound.

8)  Vary your pick technique and fretting.  Holding the pick too loose will create a weaker sound and too tight your tone may get too harsh.  Keep in mind that good picking should have the pick crossing the strings at a bit of an angle.  Vary it.  If your pick hits the string too flat, not so bueno.  On fretting, remember that you should fret just behind the fret, as close as possible but not on the fret.  If you're on the fret, you'll mute or dull your tone.  Vary these things for optimal results.

9)  Check your amp's bias.  If it's too low, your amp will sound cold, dull and lifeless.  If it's too hot, the amp will sound bright and harsh.  Oh, and you're tubes will fail faster.  Check with your amp's manufacturer for appropriate bias.  Enlist the help of a qualified tech if you don't know what you're doing.  Tubes change over time, so bias should be frequently checked!!! 

10)  Get a new cable!  Cheap cables (or cables that are too long) can eat tone.  And remember, fancy jackets don't mean high quality.  The guts of the cable matters.  Cheap cables always have lame guts.  Try a high quality Mogami or a 4 conductor Beldon Brilliant from CBI.  These can add juice back in.  It's kinda like towing a heavy gear trailer with a VW bug versus a GMC 8 cylinder truck.   Ok, this one may not be under $10.  So I'll give ya a freebie. . .

11)  Practice!  Remember, most tone is in your fingers. . .

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.

Series v. Parallel Effects Loops

Here's a GREAT discussion of series vs. parallel effects loops and what you need to know from Mike Soldano (Soldano Custom Amplification). 

Up until just recently, almost all guitar amplifier effects loops were series effects loops. A series loop interrupts the signal path between the preamp and the power amp and inserts the effect processor signal into that path. This means the entire signal from the preamp travels through the processor and re-enters the power stage. It’s basically a one-lane road going from one place to another.

Parallel effects loops have just recently begun to surface. A parallel loop offers two paths from the preamp to the power amp. One path is a direct connection from the preamp to the power amp as if the amp had no loop at all. The other path sends the preamp signal to the effect processor (via the loop) and then routes it back to the power amp, mixing it with the direct (dry) signal. Most amps that offer a parallel effects loop have a variable mix knob, so that you can control how much of the effect you want mixed in with the dry signal.

How do you choose one over the other? In a series loop, many modern, high quality effects processors can be used effectively without any problems because the sound quality will not be degraded when traveling through the processor. Additionally, there is a mix control that allows the user to adjust the dry and wet signal within the processor itself. A series loop works fine in this case. Even though the entire signal is being routed through the effects unit, the tone is still coming out of it uncompromised.

The parallel loop is useful when using vintage effects and other effects that don’t have any kind of mix function and that sometimes suffer from bad signal-to-noise-ratios, which can lead to tone degradation. Lately it seems that there has been a return to vintage effects and stomp boxes, which has probably caused more of an interest in the parallel loop.

I think that a parallel effect loop is a good thing and the ability to be able to adjust the mix is nice. However, they don’t work well if you are using effects that change the volume of the signal (such as tremolo, compression, or noise gates), or when mixing the wet and dry signals causes an out of phase situation. Technically, if you turn the mix to 100% in a parallel effect loop, it should operate exactly like a series loop, although this is not the case with all amplifiers on the market.

In my opinion, if you don’t need a parallel loop, don’t bother. It’s generally a lot more circuitry, and can end up costing more money. However, if you do use older effects or stomp boxes, I highly recommend a parallel loop for its flexibility.