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Sunday, December 30, 2012

What's ahead?

I find it interesting that when I read some interviews with musicians, they talk about looking for their sound, getting a different sound, or searching for something new. Yet when you get to the description of the gear they used on their last recording, it's almost impossible not to find the word "old" or "vintage."  They're trying to think outside of the box while being planted firmly inside of it. On the other hand, some people are already so far outside that I have a hard time keeping up with what they're doing. Instead I find myself wondering how the box we're in is going to grow.

One technology area that's overdue for a good idea is loudspeakers. If you look at a speaker objectively, it's pretty crude--very inefficient, limited in the range of frequencies it can reproduce, delicate--it's made of paper!  Certainly there must be better ideas out there to move air. Piezos may be a first step, and I've read about thin speakers and vibrating membranes, but don't know of any commercial products.

Similarly, magnetic pickups are due for an upgrade. The signal they produce is tiny and prone to noise, plus the magnetic field can interact with the string if it's too close. What about optical sensors? There are several out there already that offer better sensing of the string's vibration and are immune to electrical interference from lamp dimmers and other devices.

Digital signal processing offers some exciting possibilities to make a guitar a better instrument. Here I'm referring to something like the Antares auto tune circuitry that does pitch correction on the notes you play so the guitar plays in tune when it's not, and intonates perfectly. It doesn't have to change the sound of the guitar, although it can (like making an electric sound like an acoustic). But think of the restrictions this removes:
  • the 25.5" scale length of a Fender is critical to its sound, but if you may prefer the 24.5" scale of a Gibson there was no way up until now that you could get the tone 
  • intonation doesn't need to be perfect on the guitar, so you don't need a Buzz Feiten tuning system or Plek setup
  • transposing a song won't affect the chord voicings
Digital modeling amps are a great idea on paper, but the reality of it hasn't panned out. There's something a little off in the sound and the feel. Maybe that's the Turing Test for amps when you can't tell whether you're plugged into a blackface Super Reverb or a digital model of it. Similarly I heard that playing a Variax guitar felt "wrong" for some of the sounds--like playing an electric guitar, but  hearing a 12 string acoustic is "wrong." (Maybe that point above about scale length won't hold true.)

So as the calendar clicks off one more year, I'm wondering what the future will bring.

Thursday, December 20, 2012

Trainwreck amps demo

Just watched a great demo of 3 classic amps built by Ken Fischer, the 2 Trainwreck Express and 1 Liverpool. One Express were owned by George Lynch and the other was Ken's amp until he sold it to Billy Gibbons. The demo is great, using a Strat and Les Paul with different settings and playing. You can really hear the difference among the amps and guitars. Check it out:

Friday, December 14, 2012

The role of rectifiers

The job of a rectifier is to convert alternating current (AC) to pulsating direct current (DC). The filter capacitors that follow it in the circuit remove the pulsations, and provide a smooth DC power source. It seems pretty basic, yet how this is done has an effect on tone.

There are two types of rectifiers: tubes and solid state diodes. In the early vacuum tube days, solid state diodes weren't powerful enough or readily available, so rectifier tubes were used. In the 1960's, solid state technology had advanced enough where silicon diodes could be used. Sometimes several would be strung together to get the voltage rating needed, but now that's no longer the case.

One difference between the two devices is that a vacuum tube rectifier has an internal resistance (which is different depending on the type of rectifier tube used). Another is that tubes are sensitive to the amount of capacitance that is used to filter the pulsations out of the DC, and have a limit to the amount that can be used.

The way these two factors affect tone shows up as:
  • sag or compression in volume when playing loud, and
  • the amount of bass the amp can reproduce.

Both loud volume and/or bass frequencies pull more current through the power supply. Current through the resistance in a rectifier tube produces a voltage drop at the tube (Ohm's law), so the power supply voltage sags below what it is when the amp is idling. If the capacitors following the rectifier tube can't make this voltage up, the B+ voltage dips and the volume goes down slightly. When you're playing loud, or hit a loud note, this sounds like a little bit of compression. Or if there's a lot of bass, the tone changes because the bass is amplified less than the other frequencies.

Diodes don't do this. The voltage drop across a diode is constant and very small in comparison to a tube. They also don't care how much capacitance is at their output, so larger capacitors are often used. This makes an amp play "tighter." Metal players usually prefer diode rectification for its tightness, while many blues players like the looser tube rectification because the compression makes the amp sound like it is singing.

Diodes are cheaper and will last longer then rectifier tubes, but amps still use rectifier tubes for tonal purposes. Most of the time the rectifier type is built into the amp design, but some amps (Mesa) allow switching between tube and solid state rectification. There's also a mod that uses a diode to isolate the preamp and power amp capacitors. This allows the preamp to stay tight, since it stops the power amp's filter capacitors from drawing on the stored voltage in the preamp capacitors when the amp is working hard. It's also possible to build  or buy a rectifier tube socket with solid state diodes wired into it to change the rectification method. (You need to be careful here as this also raises the B+ voltage slightly and may stress aging filter capacitors.) And there are even some solid state rectifiers that have a resistance built into them so you get solid state longevity with tube-like tone.

Sunday, November 25, 2012

What to do with that extra channel

Almost all the Fender blackface and silverface amps have 2 channels, a Normal and a Vibrato (which may also have reverb). This is a historical feature. In the early days, one amp was used for the guitar, microphone, and possibly an accordian. Now with the one-amp-per-instrument model, having two similar channels is not the most flexible setup.

For one thing, the Normal channel requires a 7025/12AX7 tube, and if you're not going to use it, why buy one? You can not install the first preamp tube, but there's a subtle difference in sound. The B+ voltage goes up a hair (probably not sonically noticeable), but because the cathode resistor one the second triode in the tube is shared between the Normal and Vibrato channel, the Vibrato channel's tube is now set up differently. Instead of the cathode resistor being 1500 ohms, it drops to 820, which changes the bias and makes it distort a little easier. Try it and see if you hear a difference.

What about running the channels in parallel by plugging into #1 on the Vibrato channel and running a short patch cord from Vibrato #2 to Normal #1? On the non-reverb amps like the Band Master and Dual Showman, this works, and is an interesting sound. But on the reverb amps, the two channels are out of phase and there is some cancellation which doesn't sound good. Each time the audio signal passes through a tube stage, its phase is inverted. The tubes used in the reverb circuitry invert the phase of the signal when compared to the Normal channel signal, so this isn't a good idea for most uses. (Maybe you're one of the few that has a use for the phase cancellation sound.)

Running the preamps in parallel works really well for Marshall 4-input amps. A lot of players jumper the two channels of a SuperLead as a standard way of setting up the amp. This came about for another reason (see my June 20, 2012 post) but creates a nice thick tone.
There's a simple mod that lets you use the Normal channel for finer reverb control (on amps that have reverb). Run a shielded cable from the output of the reverb tank to the input on the Normal channel (you'll need and RCA to 1/4" cable). The Volume knob is now similar to the Reverb knob in function, but you have tone controls. Easy enough to try without a big commitment.

For more intrusive uses, you can cascade the channels, which was the idea Randall Smith had in the '70's which became Mesa Boogie. This is a bit of an art, as you can't get a good sound by just running one channel into the other (see the Marshall One-Wire mod on my website). Distortion sounds better if it's built up over several tube stages, so you'll need to attenuate the signal. Plus bass muddies the tone, so you'll also have to add a high-pass filter to get something usable.

Another thought is to re-voice the channel so it sounds different. One idea on my website is to turn it into a Tweed style preamp. Other people change the tone stack components, or add a Marshall style preamp (where the tone controls are after the 2nd triode stage). Something to give a different sound and make the amp more flexible. By using an A-B switch box you can add channel switching to these amps.

Consider it--it might be a fun way to play with your sound. But be cautious about modifying these amps in a way that can't be returned to stock (like by drilling holes). As they get older they're becoming more valuable, and sometimes it's better to mod your amp ownership rather than your amp.

Monday, November 5, 2012

If it's too loud, you're too old

Made by Dr. Lex
I read a really well-done article by Dr. Lex describing a trend of reduced dynamic range in music recordings for the sake of perceived loudness. The graph here is from his web site, and shows this trend starting about 1990, and getting increasingly more apparent over the next 20 years.

I started paying attention to music seriously in the '70s which was a relatively stable period for dynamic range--it was present in recordings. The vinyl albums I was listening to had a lower possible dynamic range than CDs have, but still it was used to effect--there were quiet parts and drastically different loud parts. The first album that I remember being extra loud was Alice Cooper's "Killer" in 1971. At the time I didn't understand why or how this could be, but it fit with the nature of the album and was cool. I wasn't alone, my friends noticed it too. But this may have been one of the first shots fired in what Dr. Lex calls the "volume wars."

I think the ear training that I received in the '70s colors the way I hear contemporary mixes--they're less interesting. Younger people are growing up with this reduced dynamic range which will be their ear training that they will take forward with them. It will be interesting to see where it goes.

It's ironic that modern media has the ability to reproduce a greater dynamic range than was available in the '70s, but it isn't being used due to the nature of how the data is delivered and consumed--MP3s, earbuds, etc.

In the meantime, I must be too old, because it's too loud. I miss dynamic range.

Saturday, October 20, 2012

What a difference a (tube) stage makes

Blackface Fender Deluxe amps sell for much less than blackface Deluxe Reverbs. An informal survey of completed Ebay sales shows about $1000 difference between the two.

This is due to more than the lack of reverb; the Deluxe Reverb has just a touch more gain to it, giving it a slightly different sound. There is one extra triode that's used to mix the reverb return with the dry signal, and even with the reverb knob set to 0, it's still in the signal path of the Vibrato channel. This, I think, is what endears it to a lot of guitar players.

When you add the reverb into the picture, the signal now goes through 3 additional stages, so the reverb adds additional coloration to the amp. I've read newsgroup posts where the Deluxe's fans feel they can get the same thing through a reverb pedal or other effect, but it doesn't duplicate the the signal path. There's reverb, but it's not achieved the same way.

The Deluxe is a great amp and has great sound. Although it's similar in name to the Deluxe Reverb, it's a different amp, and not as flexible. Its two channels are differentiated by one having tremolo, and the other not. A Deluxe Reverb's channels on the other hand, are almost like having two amps. The normal channel is a Deluxe with the tremolo turned off, and the vibrato channel adds a gain stage, reverb, and tremolo.

Wednesday, October 10, 2012

Another take on using your ears

Just came across a Gibson online article that is similar to two of my early postings, the July 2, 2012 On Using Your Ears, and the July 19, 2012 More On Using Your Ears. In the Gibson article, Dave Hunter talks about "home tone" vs. "gig tone." The take-away line for me is

"When you get “your tone” set up and ready to go in sound check, then find it is lost in the ether once the band kicks in, don’t be too proud—or too stubborn—to change it."

 And he sums it up with

"...get your tone out there to the ears that matter most to the live performance: someone else’s."

 It's a good read for another take on this topic.

Friday, October 5, 2012

Selection strategy

Knobs courtesy Derek Jensen (Tysto) WikiMedia Commons
A lot of digital gear comes with hundreds of preset patches or at least hundreds of spaces for you to record your own patches. For live playing, this is overwhelming; at best you can remember a handful of your favorites. One way to deal is to simplify and memorize a just a small bunch at at time. But you need a way to call these up quickly, and that's where things get interesting, how to map the list to a control device. I think the best schemes provide an analogy (visual or mental), and simplify (reduce) the number of choices.

I've heard that there are 128 pickup combinations on a Strat (pickup(s) chosen, series wiring, parallel wiring, phasing) yet the original Strat wiring simplified by provided just 3 with a lever switch. The switch pretty much pointed at the pickup that was being selected, providing the analogy. That's since been expanded to 5, and uses the same position analogy. But even if you only consider the parallel wiring that's so commonly used, there are 7 combinations, so some simplification is still happening.

In trying to get at more of the possibilities, I wired in a 3 position mode selector to one Strat that ups the combinations to 10. The 5 position selector switch is still the same, but the mode switch changes what 5 pickup combinations you get. This makes it a lot easier for me, since I only need to remember 5 things at a time, and the position of the switch tip uses the traditional analogy to sort of point at the pickups being selected. There is still some simplification going on, as this setup can theoretically have 15 selections, but wiring limitations lower that number. Also the groupings are meant to be functional not exhaustive. The modes group pickup selections into usable groups. Mode 1 is the stock wiring, so you don't need to remember anything new. Mode 2 gets at the missing 2 combinations--neck+bridge, and all 3 pickups on. The 4th and 5th positions are rewired, but positions 1-3 still give you the stock combinations. I think of mode 3 as a 2 pickup humbucker guitar. It's louder, and has only 3 pickup combinations.

Some people choose to implement pickup wiring with a set of 3 or more switches to individually control the pickups. This doesn't work for me, there's no visual or mental analogy that I can lock into. It also isn't simple, it takes several switch throws to select a pickup combination. A compromise is to provide a switch that just turns on the bridge pickup so it can be added to any combination selected by the pickup selector. I tried this for a while, and didn't like it because selecting pickups is still a 2 step operation--use the lever switch and check or throw the bridge pickup switch.

Another example came up with a Marshall JMP1 preamp. This has 100 patches. On its front panel, these are laid out linearly using a knob to sequentially scroll through them. I originally started out using a MIDI foot controller that allowed me to access any patch. I noticed however that I never used more than 5 patches in any situation. I think Marshall realized this too, because in addition to MIDI switching, they have a footswitch connection that puts just 4 patches at your disposal (simplification). You can map the 4 buttons on the footswitch to any patch. I made a footswitch for it and laid out the switches with the idea that the cleanest patch  was at the left side, and the highest gain at the right. This mental analogy, like the visual image on the Strat pickup selector switch, helps me keep things straight.

There's another way to remember patches that works for me, and that's a table layout. Patches are arranged in banks, with the patches in a bank being a variation on the theme of the bank. Way back when, I set up my Zoom 9002 that way. There is a distortion bank, a time based bank (chorus, flange), a weirdness bank (envelope follower, arpeggio generator), and a harmony bank (added octaves, fifths). The patches in a bank use other effects like distortion, reverb, and compression, but the main flavor of the patch was what got it added to a particular bank. Doing this, I was able to remember a 4x4 array, or 16 patches.

The MIDI controller for the JMP1 also used table layout. However remembering the large array needed for 100 patches (10x10?) misses the  idea of simplifying. Still this layout has the advantage of making it quicker to get at patches at different ends of the spectrum. On the JMP1 itself, going from patch 1 to patch 50 involves scrolling through 49 patches (still, it's fairly quick with Marshall's spin knob). With the MIDI foot controller, you step on the bank switch to get to the correct bank, then select the patch in that bank.

I think the inability to hold all the possibilities in our heads is what contributed to the decline in popularity of rack effects processors in live guitar rigs, and the return to stomp boxes with analog style controls. The stomp box provides the simplicity of a few knobs to control parameters, and a visual indication of where those parameters are set. This has extended into audio recording software where there is often an optional interface for effects plug ins that looks like a stompbox. Somewhere along the way the technology parted ways with the way we think and we went back to the tried and true.

Saturday, September 22, 2012


Most people don't use the standby switch on their amp correctly, at least in the way that I understand things. I wonder why these are still being put on amps. Yes, I understand the reasoning, but I haven't really seen tubes wearing out that much faster. Maybe it's a subtle difference.

The idea behind a standby switch is to give the tube heaters a chance to warm up to operating temperature before you apply the B+ voltage and the tube starts working. Failure to do so leads to cathode stripping (whatever that is), and is detrimental to tube life. What I've read, and believe enough to follow myself, is you should
  1. turn on the power switch
  2. wait at least 30-60 seconds
  3. turn on the standby switch, and make noise.
Powering down is the opposite:
  1. turn off the standby switch,
  2. wait at least 30-60 seconds,
  3. turn off the power switch
But where most people go wrong is the time in between those two events. At the end of the first set, don't use the standby switch. Leave the amp on. Unplug your guitar or turn the volume down at the end of a set, but leave the amp on the whole night. Component failures are most likely to happen at start up--caps are uncharged and there's a large current surge, things are cold and need to heat up, etc. Think about a light bulb. How many times have you seen one fail when it's been on a while? Most fail when you turn them on.

Leaving your amp on the whole night is easier on the amp because there's only one startup. After everything is warmed up and ready to go, it coasts along until the end of the night. If you're turning it off because it's getting warm and you don't want to cook the components, consider installing a small fan. Even a little air movement will help immensely. I've installed fans in my Fender amps because I don't like the idea of the downward hanging tubes cooking the components in the chassis above them. I think this is a drawback for combo amps, but then it can't be too big a deal because there are so many combo amps doing just fine. If you what to install one, you can run a 12 volt fan off the 6.3 volt heater supply. Sometimes you can hook it up directly, while other times you may need to add a diode and capacitor to give it a DC voltage. It will run slower than it was designed to, but if you can feel any air movement, it will move the heat out. Running it slower has the benefit of making it quieter.

If heat is a concern, you may have bigger problems. The tubes will get hot enough to burn you, but nothing else should be so hot that you can't touch it for a few seconds. Especially watch the transformers, as they are the most expensive items in the amp. Heat means too much current is being drawn, and you need to find out why. Sometimes it's as simple as a bias adjustment, other times it might be rusty laminations in the transformers causing eddy currents and robbing power.

Friday, September 7, 2012

Fender Pro Tube series Twin repair story

Got a Fender Professional Tube Twin for repair, the owner says it's lost a lot of its volume. Here's how the repair unfolded.

Most common cause of failure is the tubes. Checking the bias on the power tubes will show if they are all working (a dead tube doesn't draw any current), and also see if the amp is set up correctly. The amp is set up a little cool (460V plate, 26-30mA/tube), but this isn't terrible and isn't the cause of the problem. It's time to look inside.

This amp is a full-featured amp. Lots of settings and switches. 8 preamp tubes and 4 power tubes. Inside there are 4 circuit boards, 2 of which are mounted component side down so you can't see the parts. A schematic would be helpful, but I couldn't find one online so I started with the basics.

Checking the plate voltages on each tube is a good diagnostic test for the overall circuit. Pins 1 and 6 are the plates on 12A_7 tubes, and you don't need a schematic to find those. You should also get a pop as you touch the probe to the plate to indicate that the signal is going through the amp. If it doesn't pop, something is wrong downstream. Unfortunately (or fortunately), all the plate voltages were reasonable for a Fender amp.

This amp has two channels, plus a gain boost on one of the channels which probably adds in another tube stage. Since the low volume problem is happening on both the channels and with the gain boost, the problem has to be either after the preamp or in a shared tube stage. Often the first preamp tube stage is common to all the channels. Checking the first tube would just involve substituting a known good 12AX7 tube to see if the problem went away, but I decided to check the power amp first for no good reason--had to start somewhere.

This amp has Preamp Out and Power Amp In jacks. There are switches in these jacks that can oxidize, and it's possible that some resistance built up which could cause a volume drop. Usually this problem shows itself as variation in volume, or crackles, not a consistent volume drop. A quick check is to hook a guitar cable between these and get around the switches. If this brings the volume up, then some DeOxit will usually clean the switches. Doing this had no effect, so that wasn't the problem.

I have some experience with the plate resistors on the phase inverter of some newer Fender amps opening up. If one opens up, you lose half the power. This would have shown up as no voltage on the plate when I checked it earlier, but I still re-checked it. The failure on the amps I saw was due to what I think is a too-low power rating for the resistor. (As a side note, I've learned that if one of these resistors opens, BOTH plate resistors should be replaced while you're in there. It's usually just a matter of time before the other one goes.) But on this amp, the plates are 1 watt resistors which is a good design upgrade on Fender's part.

What's interesting on this amp is it seems that the two tube stages needed for a long-tailled phase inverter are split over two tubes. Normally one 12A_7 tube with its two tube stages is used. I wasn't sure what the other tube stage in each tube was doing, so I spent a little time trying to follow the circuit path with a continuity/resistance meter. In doing so, I found one resistor that looked fine but was open. In looking at the circuit, it appears that this tube stage is a cathode follower, and this is the cathode resistor. That made sense because the plate had voltage on it, but the signal is coming off the cathode, something that I hadn't checked earlier. This is where a schematic would have saved some time in identifying this.

Since the resistor was open, I bridged it with a good resistor and the volume came back. Looking at other Pro Tube schematics, this tube stage is possibly the recovery tube for the effects loop.

To repair it, I decided not to remove the circuit board to get at the solder traces underneath. Due to the complexity of the amp, this would have added time (raised the cost), and there is also some risk to flexing the ribbon cable connectors as you remove the circuit board. By clipping out the resistor, leaving as much of the leads intact as possible, you can form the leads into loops, and use these as sockets for the replacement resistor. The replacement resistor's leads wrap around the loops and provide a good mechanical connection. When soldered, the repair is very strong. I feel good about doing it this way on my amps, so I think it's the best way to go. Total billable time: 2 hour

Saturday, August 25, 2012

Amp distortion

In the '50s, guitar amps were available in what is now considered to be the lower power range for amps. This means they had less headroom and were more prone to distortion. Since there was less clean headroom, when you needed a little more volume, or you had hotter humbucker pickups, you entered the operating range where distortion was present. So unintentionally, amp distortion was part of the sound to which we grew accustomed.

But distortion is also an interesting sound, more harmonics, a little bit sax-like, and players liked intentionally exploring it. (That, added to the fact that it was also a bit rebellious to be loud enough where the grown ups yelled at you to turn it down.) I've read stories of John Lennon, Eric Clapton, and Keith Richards fighting with the recording engineers to leave the distortion in the recording. The Beano album, with Clapton playing a Les Paul through a cranked Marshall is still today considered a hallmark of guitar tone, but it wouldn't have been had the "common sense" engineering of the time won out.

So the situation was one where distortion was present and being explored. Imagine though if more powerful amps were available during rock and roll's formative years. There would have been more clean headroom, less distortion, and distortion would have been harder to come by without being really loud. The sound of rock and roll would be quite different today. By the mid 60's, when 100 watt amps were finally readily available, it was too late for this effect to happen. Distortion had been dyed into the fabric of rock and roll, it was part of the tone. So in order to get the tone with the bigger amps, you had to turn up, and instead of becoming cleaner sounding like it would have in the 50's, in the 60's rock and roll got louder. The same bit of technology introduced at a different time had a different effect.

There was still some uncertainty about the role of distortion in the '60s. Around 1965 Leo Fender sold his company to CBS. CBS brought in engineers that tweaked the circuits with the intent of making them more hi-fi--they hadn't caught on to what was happening--and the CBS silverface amps got a bad reputation among musicians. Pre-CBS blackface amps were sought after then and still command a higher price than the silverface models, although enough time has passed where this is starting to fade. (A lot of silverface amps are modified to be more like the blackface circuitry, and used to be a bargain if you didn't care about the cosmetics.) Modeling amps still pay homage to the sound--nearly every digital modeling amp has a "blackface" or "California" sound on it.

In the '70s a watershed moment for distortion happened--it was accepted. Randall Smith was heavily modifying Fender Princeton amps to add more gain stages. In a December 2005 Guitar Player article, he said at the time he was doing this because the blues and rock players wanted more distortion at lower volumes. The cascaded tube stages he added produced the distortion, and master volume controls limited the volume going to the power amp. So the power amp was no longer distorting, since it was working less hard, while the preamp tubes were. But not all distortion is the same. When they distort, the small preamp tubes sound different than the larger power tubes. In essence, this is the sound that the Mesa Boogie Mark I amp brought to the table. and later Mark II amps made adjustable with the amp's knobs. Distortion tone had become more adjustable.

So the palette of distortion currently available in amps now involves several approaches. Bands with a vintage sound either play really loudly (AC/DC) to get the power tube crunch, or use power attenuators to dump some of the volume as heat. Metal bands rely more on cascaded tube stages to develop the sound (although they play loudly as well). Master volume controls give control over the character of the distortion. And all this is without considering the huge role played by stompboxes in front of the amp.

Cascaded gain stages had another effect on amps. The drawback of cascaded tube stages is you lose touch sensitivity; as you play lighter on the strings, or roll back your volume, the amp doesn't clean up the way it does with a vintage amp, the tones available from your fingers are reduced. I find this to be a limitation because it reduces dynamics and is more compressed, and a series of notes played on the guitar comes out all with the same tone. On a vintage amp, the dynamics of your playing influence the tone of the notes. But to each his/her own.

In order to get back the clean tones on a  cascaded amp you need to have different circuitry. This is done by having multiple channels. Most high-gain amps have more than one channel, usually footswitchable. The channels have increasing amounts of gain and have names like "clean," "crunch," "overdrive," etc. So when you want the clean sound that you can get with a lighter touch on a vintage amp, you step on a switch to change the channel. The advantage of this approach is the range of distortion sounds available is much greater than you can get with a vintage amp.

An electric guitar without its amp is only half the instrument. The foundation of your tone starts with your fingers, but it's shaped by your guitar and amp--and the settings you choose.

Thursday, August 9, 2012

Playing as a band

By Infrogmation of New Orleans,
via Wikimedia Commons
Some people listen too much to themselves when playing with others. You've worked on your part, you've practiced, and you want to play it right. The last step is asking yourself "does this fit?"

In a 9/05 Guitar Player magazine article, Mike Stern was talking about some guitarists getting all excited about playing with a horn player because they can haul out all their chord inversions. He basically takes a less-is-more stance:

"When I'm comping and I'm deciding which chords to play, a lot of times I'll play the least amount of notes possible…I'm often playing no more than two notes from each chord."

I've been in situations where:
  • in a 7 piece band, everyone was playing multi note triads--the guitarist was playing a 5 note triad, the keyboard added a 7 note triad, etc. There was no sense of anything but a close chord voicing because every note was played in all the octaves starting from the root.
  • the backing vocal harmonies were louder than the lead vocals, and the harmonists were not listening to the phrasing being used by the lead vocalist, a situation I call "lead harmony."
  • an instrument would play the melody along with the vocals, so like the lead harmony situation, there were two competing interpretations for the phrasing
  • people playing "their part" when there are substitute players who don't know about, and aren't playing, the counterpoint that makes "their part" fit

Some situations that I like being in are the opposite:
  • a 7 piece band playing 5 note chords, each person taking one note and 2 people playing rests
  • 2 people playing 4 and 5 note chords as stacked chords. For example, a C maj7 chord can be played as a C triad and an Emin chord. This idea can also be applied if you let the bass take the roots, and you play the upper parts of a rootless chord.
  • taking the above idea for creating solos in a band setting where the chords are triads and 7ths. With the backing tracks playing the chord, build a solo on arpeggios that add the upper end--the 7ths, 9ths, 11ths, 13ths.
  • people that aren't afraid to play rests.
As with many things, less is often more.

Thursday, July 19, 2012

More on using your ears

By Iain, via Wikimedia Commons
As a follow-up to my last blog about listening to your sound, I've seen people get caught by the mix of instruments in a band changing the way you hear your part. Typically this happens when the guitarist gets a new distortion pedal. You dial in what you think is a great sound (at home), go play with your band, and the mix is good when the pedal's off. Then your solo comes, you step on the distortion pedal and...disappear from the mix.

Here's a case where using your ears isn't enough by itself, the context also matters. When the disappearing-distortion-solo happens, it usually is because there is too much distortion dialed in. All the new harmonics generated by distortion change your place in the EQ spectrum of the mix, you find you're competing with the frequencies being generated by the other instruments, and there's no clarity. Reaching for the volume knob doesn't help, it just makes the mud louder.

When you can't hear yourself in a band, sometimes reaching for the tone knobs is more effective than reaching for the volume knob. Recording engineers know this. If you isolate instruments in a good mix, they may sound thin or strange, yet together the sound is working. For example, the bass and bass drum live in the 45Hz-250Hz area. The other instruments can stand to lose everything below 250Hz to stay out of their way. A heavy guitar player is not going to like the sound of this by itself, but allowing the low end of the guitar to overlap the bass will just generate mud and the mix will suffer.

Last year I got a 7 band EQ pedal that I have set for a slight mid boost. If I don't think my solo is standing out enough, I've been surprised at how well this makes it cut through when I step on it--same volume, more presence.

Playing around with home multi-track recording is a great way to see this in action, and gives you full control over all the variables.

Monday, July 2, 2012

On using your ears

I've been doing repairs for a while and have noticed that some musicians like to mark "their setting" on the gear. Sometimes there's tape with the setting numbers written on it, other times there are lines drawn on the faceplate and knob that are meant to match up. This hits me as strange, since your sound is not an absolute. There are so many variables that affect your sound, to list a few
  • the size of the room
  • is the room full of people or empty?
  • are you outdoors?
  • have the speaker cones been in a humid environment and absorbed some moisture?
  • is your amp coupled to the stage, sitting directly on it?
  • with some speaker cabinets, where are they pointing?
  • How old are your strings?
  • etc, etc
To assume that you can dial in your sound in your bedroom or rehearsal space, and then transplant it somewhere else is wishful thinking. At best it can be a starting point for dialing it in, but there's still work to do. The best advice I've heard is to adjust your amp settings like you are in a dark room--in other words, don't look at the numbers on the dial. Even better, get rid of the numbered knobs and face plate markings and just twist the knobs.

I got a callback on one repair that I did saying that the amp now had more treble. What had happened was I had taken the treble knob off the amp and put it back on in a slightly rotated position. This person was locked in to the notion that their treble setting was "7" and to their credit their ears were good enough to hear the difference. They could have adjusted it it by turning the treble down to 6.5, but it wasn't right for them until I pulled the knob off, unrotated it a click and put it back on. I guess there's nothing wrong with that, it just makes me say "hmmm..."

Wednesday, June 20, 2012

A bright idea

In the early days, it was a struggle for the guitarist as venues grew in size and volume levels went up. Amps grew in power and were EQed to cut through the mix with brightness and presence features.

Many amps at this time had a "bright" channel. The brightness is often achieved by routing the treble around the volume control so in effect, the high frequencies are always passed, and the volume control only affects the lower frequencies. In other words, the cap is a high pass filter.

A good example is the Marshall Super Lead. There are two high pass filters in the bright channel (see schematic), but the cap across the volume pot is the major brightness contributor. At low settings, the tone is very bright, but around 5 on the dial, the tone is much more in balance. However with a 100 watt Super Lead, you're also really loud!

So the amp designers set out to solve one problem with this cap, and inadvertently contributed to the volume at which rock was played. It's not the only or even the biggest factor in the volume climb over the years, but if you look at the amps being used at the time and realize they need to be turned up for tone, you may start to see a cause and effect situation.

The Super Lead is probably the most obvious use of a high-pass filter, but the Vox AC30 with a Top Boost preamp and most of the Fender amps also employed it. Many of the Fender amps made the high pass filter switchable. (The Deluxe Reverb is an exception where the cap is hardwired into the Vibrato channel.) Fender also used a more moderate value for the cap so the effect wasn't as great as it is on a Super Lead.

For many people today the bright channel on a Super Lead actually does its job too well which is why the normal and bright channels are often jumpered together and run in parallel. There is also a simple modification to clip one of the leads on the cap to remove it from the circuit. You still have the second high pass filter, but it's a more subtle effect.

Thursday, June 14, 2012

My plan...

I've got a web site that deals with the more technical/factual aspects of music gear (http://sites.google.com/site/yourtubeamp/), especially tube guitar amps, and for a while have had ideas and thoughts that are more opinion based that didn't seem to fit well there. So here they are.

It's a chicken-and-egg situation that I find interesting: the gear influences the music, and the music influences the gear.

See what you think.