Full Custom Music Repair

Barnacle Fuzz pedal compared to a Vintage Fuzz Face pedal.

2012-01-09T12:47:00.001-05:00

Here is a video showing the versatility of the Barnacle Fuzz and how a Vintage Fuzz Face like sound can be dialed in using the Barnacle Fuzz. We used a Vintage Dallas Arbiter Fuzz Face with Mullard OC71 Germanium Transistors for the Video.

Barnacle Demo

2012-01-02T14:58:00.002-05:00

Before the holidays we filmed a video demo for the Barnacle Fuzz. Please check it out and let us know what you think. If you have any questions feel free to drop us an e-mail or comment on this post. Thanks to Gabe Spangler and Jonathon Zeppa for helping us out.

Holiday Hours

2011-12-23T12:28:00.000-05:00

We will be taking some time off and closing the shop beginning Saturday, December 24th, and returning Monday, January 2nd, 2012.

Thank you for all your support in 2011! Have a happy and safe Holiday and a rockin' New Year!

UFO crash landing: Ace Frehley's UFO Guitar gets a new light show.

2011-11-09T12:42:00.000-05:00

Ace Frehley's UFO Guitar landed at the shop for some light modifications. Here is a short video of the finished mods that we did at the shop. We will be posting a detailed photo blog of the process in the very near future.

Rickenbacker 4001 Fretless

2011-11-08T13:51:00.002-05:00

You don't see too many Rickenbacker 4001 Fretless basses around so thought it would be nice to upload some pics of it. This Bass was just in for some minor work, clean electronics and usual maintenance. The customer has owned this instrument for many years but did not play it much due to the 'fret markers' on the side of the fingerboard. Rickenbacker had installed a side dot indicating every position of where a fret would have been. This is all well intentioned, some people probably really enjoy the thought, but it makes the side of the fingerboard very cluttered and hard to judge where you are playing on the fingerboard. (see below)

The quickest solution, one that still entailed the original concept of design, was to drill out select black side dots and replace them with white dots. This would not modify the Bass too much but still allow for a less cluttered look on the side of the fingerboard.

It was a fun job, the customer was happy and we got to jam on a fretless Ricky at the shop.

Supro Thunder Bolt Restore

2011-11-04T13:13:00.000-04:00

This great old Supro came into the shop in pretty good shape. The chassis was covered in duct-tape and there was only a loud hum on the output. First thing was to remove the duct-tape and clean up the chassis.

After the chassis clean up, we replaced the coupling caps and power cord. The original RCA tubes were still in great shape and did not need to be replaced.

Gotta love the grill cloth and covering. This amp sounds really sweet cranked full out and the 15" speaker makes for a huge sound.

Bass Fuzz Dot Com

2011-08-24T13:38:00.002-04:00

Bassfuzz.com is the authority when it comes web reviews on making your low-end fuzzy. So we contacted them to see if they would review the Barnacle Fuzz. We were very pleased to get the okay to send out a pedal. After a few weeks of patient waiting our pedal's review was finally posted. You can see it here. Make sure you check out some of the other parts of the site. There is a lot of info and it is fairly well organize.

Effectswire Reveiw

2011-08-23T16:24:00.002-04:00

We've sent out a few Barnacle Fuzz pedals to be reviewed. Mike at Effects Wire was the first to post a review. I really enjoyed reading the other reviews on his site. I'll certainly be stopping by often to keep up to date on the latest goings on of the world of fuzz.

Barnacle FAQ

2011-05-18T15:04:00.003-04:00

Barnacle FAQ

● Is the Barnacle a clone of a vintage pedal?

○ No, it is an original design and concept of Full Custom Music Repair. It is the replacement for the now discontinued Germanium Kraken. There were three vintage pedals that we looked at for inspiration, the Big-Muff, Dallas Arbiter Fuzz-Face and Colorsound Overdriver. Although no direct circuits are taken from these effects, the Barnacle is designed to produce the same type of harmonic distortion as the Germanium Fuzz-Face.

● Is the Barnacle True Bypass?

○ You can select between True Bypass or Buffered Bypass with the internal DIP switch

● Will the Barnacle work with a DC supply?

○ All our pedals are designed to work with the standard 2.1mm center pin negative supply. This was the number one most requested feature by customers who purchased the original Kraken Overdrive.

● Will the Barnacle work with my Wah pedal?

○ Yes, either before or after the Barnacle. The Barnacle should work with any other effects that you have. In fact, if you have a problem with another pedal in your chain you can use the Barnacle’s buffer to make it play nice with other pedals.

● Where should the Barnacle be in my effects chain?

○ Anywhere in your effects chain will work. Although, settings above unity gain may sound best with the Barnacle last. If the Barnacle is first a chain of multiple effects you can use the buffer to buffer your entire effects chain.

● Will the Barnacle affect the low end of my bass?

○ No, the Barnacle has a flat frequency response. We did everything possible to make sure that only the Bass and Treble controls affect your tone and that at their 12 o’clock settings they are effectively bypassed.

● When the bass control is turn up will it affect the highs?

○ No, rather than a passive tone control we have given you active Bass and Treble controls which were design to have no interaction with each other and limited interaction with the other features. This allows you to dial in tones that are dark, bright, mid-rangey, scooped or even very neutral.

● Will the Barnacle work with single coil pickups?

○ Yes, you can even use the EQ to make them sound mid-rangey and thick like a humbucker.

● Will the Barnacle be too muddy sounding with humbuckers?

○ No, you can even use the Treble control give a humbucker more edge without losing bass response.

● What battery life can I expect?

○ Current draw is less than 20mA. A Carbon-Zinc 9 Volt battery should last greater than 30 hours of use.

● Will the Barnacle work with an amp that is already overdriven?

○ Yes, very well as a lead boost or for just a thicker sound.

● Is it a Silicon or Germanium Fuzz?

○ Although the Barnacle Fuzz is the replacement for the Germanium Kraken it does not use Germanium transistors. Every Germanium transistor sounds a bit different and that sound varies with temperature. We did a lot of research to find out just why Germanium transistors are so cool in a Fuzz-Face. Then we used that information to design a fuzz with all modern parts that would sound great every time. Because of this every Barnacle sounds very much like the last.

Introducing the Barnacle Fuzz

2011-05-11T16:16:00.007-04:00

Now that we are making the first run of the Barnacle Fuzz. Here is a list of features and some example settings. If you'd like to try or buy the Barnacle Fuzz stop on by. If you are a music store and would like to be a dealer for the Barnacle Fuzz contact us for minimum order quantity and dealer pricing. Retail price is $149.

Barnacle Fuzz Overview

The Barnacle combines the features of several 1960’s and 1970’s era fuzz pedals into a single, modern and useful package.

Features

Fuzz-The Fuzz control adjusts the amount of vintage fuzz goodness, this control is designed to work like the gain control of an amplifier.

EQ-The active bass and treble controls offer much more flexibility than a single tone control. At their center positions the controls are effectively bypassed. At their extremes they provide +/- 15db of cut or boost. The center frequency is set at 800 Hz.

Volume-Adjusts the output signal level to your amp. The Barnacle can provide 6db of full range boost. With the volume control at its center position the boost will be about 3db, depending upon the settings of the other controls.

External Supply Jack-Standard 2.1mm center pin negative 9 Volts. Current required is less than 20mA. A higher voltage power supply will not change the sound of the Barnacle as the supply voltage inside the pedal is internally regulated; this helps to keep the Barnacle free of noise. If the wrong polarity supply or a supply with an excessively high voltage is used it may cause damage to the pedal.

Bypass Switch- The Barnacle Fuzz has two bypass modes selectable via internal dip switch. Trü Bypass (oo--) for boutique style True Bypass and Buffered Bypass (--oo) which uses a unity gain buffer that does not bypass with the effect. This setting works well for those times when true bypass does not work, as in connecting many devices inline, extreme mismatches of impedance or long cable runs.

Frequency Response- The Barnacle Fuzz is designed to maintain an accurate representation of your original signal within +/- 1.5db when the EQ Controls are set to their center position. This allows the Barnacle to be useful not only for electric guitar but also bass, keyboard, acoustic guitar or many other applications. In fact, if you find something the Barnacle does not work for let us know.

Example Settings
(Fuzz, Treble, Bass, Volume)

Treble Boost - 2, 7, 3, 6
NYC Fuzz - 10, 7, 7, 2
Face-it - 3, 5, 3, 4
War pigs - 5, 3, 0, 7
Buzz-Tone (I Can’t Git’no) - 7, 10, 0, 4

Settings numerated 1 through 10 with 5 being half way.

Warranty- All FCMI products are guaranteed for one year against manufactures defect, materials and workmanship; to the original purchaser only.

Poseidon Boost!

2011-03-23T12:56:00.000-04:00

While waiting on screen printing for the Barnacle Fuzz we have been working on the prototype for the Poseidon Boost. Here is some art drawn by Patrick Benner that will be on the finished product. The circuit design is finalized and will be released next after the Barnacle. The Poseidon Boost will have two controls, an active Midrange control and a Volume. Both will be near unity gain at their mid points, providing either boost or cut.

Holiday Hours

2010-12-23T12:59:00.002-05:00

Happy Holidays, everyone! We will be taking some time off and closing the shop beginning Friday, December 24th, and returning Monday, January 3rd, 2011.

Thank you for all your support in 2010! We have some great things in the works for the New Year!

Fuzz

2010-11-22T14:48:00.003-05:00

With the success of our Kraken Overdriver, we have decided to throw our hat in the Fuzz pedal ring.

Two titans in the world of fuzz reign with unreleasable grasp; the Dallas-Artbiter Fuzz Face and the Electro-Harmonix Big Muff-Pi. Both are in production today in close approximation to their original forms as well as many products that aim to emulate or improve upon their sound.

The Fuzz-Face and Big Muff-Pi were studied very closely while designing our fuzz pedal (which will be available soon). Close attention was paid to the attack, decay and clipping of the Fuzz-Face, as that is what I most most recognize as "fuzz". I see the fuzz sound as a cough like attack, messy decay and clipping with audible transistor saturation artifacts. But the pedal should still clean up with the guitar's volume control.

At the heart of our design is a circuit that produces very similar harmonic content to the Germanium Fuzz-Face. We wanted to get the Fuzz-Face tone and something more pushed into complete saturation like the Big Muff-Pi can do. But without the use of germanium transistors. I ruled out the use of germanium transistors even though we have a good sized stock pile for two reasons. 1) The midrange bump associated with the germanium transistor is caused by other factors not the transistor in itself. 2) I wanted a fuzz with a flat frequency response. The remaining portion of our fuzz pedal's circuit shares a bit with the Kraken II (which will also be available soon) mostly the active EQ, which has much better performance over the original Kraken Overdriver.

Check out the video's below for a preview of the first of three new pedals that will be available February 2011. We will be taking pre-orders as soon as artwork is finalized.

Kraken Demo Video

2010-08-13T10:29:00.000-04:00

Thanks to our good friends Eric Wirsing and Jonathan Zeppa we now have a demo video of our Kraken Overdriver. If you haven't hear the pedal that everyone in town is talking about please check out our video, where we pit the leviathan of the deep against the classic favorite from Ibanez.

Summer Deals

2010-06-17T16:49:00.010-04:00

Here is a list of items that we have for sale this month

Any unloaded speaker cabinet can be loaded as per customer spec.

Fender Twin Amp (not-reissue '65 twin but current model) Sold!

Slant 2x12 cab loaded with G12T-75 Qty 2 available (new, selling as used Brook Musser) Sold!

Front loaded 4x12 cab loaded with Jensen 12-Mod-50 Speakers 16 Ohm (new Brook Musser) Sold!

Premier Reverb Vintage all tube Sold!

Unloaded Tweed 1x12 (new Kirk)

Unloaded 1x15 Cab (new Kirk)

Zoom 507 Reverb (used)

Vintage MXR Distortion+ Sold!

Fender Princeton (Modded by Brook Musser) Sold!

ProCo Rat

Pair of NOS 6V6GT in 1980s Peavey Retail Packaging Sold!

Vintage Kustom 150 "Hustler" 4x10 combo Sold!

Black Hole of Tone

2010-05-12T10:46:00.005-04:00

Is your amp noisy? Does it cut out? Does it make an odd sound when pushed, or does it just run hot and no one can figure out why? If so, you may have a "Tone Black-Hole".

I first encountered this problem years ago, while working on a Fender Vibroverb. The amp sounded awful unless it was out of the speaker cabinet with the reverb unplugged, which would be a completely impractical way - at best - to play your amp. The problem that I found was in the reverb circuit, and the only way to see it was with my oscilloscope. There are no better ears than test equipment. If it looks like garbage on the oscilloscope, then it sounds like garbage, as well.

I've been seeing a good number of brand new mas-production amps with high frequency instability or - what we call - the Tone Black-Hole. The above picture is the output from just such an amp: A brand new Fender Blues Jr.

The worst offender I've seen so far has been the Peavey Valve King. Hartley, I'm calling you out! Your engineers have designed the only amplifier that I have ever seen that is more stable with the Negative Feedback disconnected. Part of the power amp circuit meant to improve its operation is actually harming its ability to produce a linear signal.

Luckily this is a simple problem to repair. A few small parts or a change in wire lead dress and it's gone. In most cases, it's very simple to test for; I may not even have to disassemble the amp.

KT77 Vs EL34

2010-04-27T09:57:00.005-04:00

Over the years there is one tube that I have had more trouble with than any other. Unfortunately, it is also one of my favorites: the EL34. I have tried every EL34/6CA7 out there, and I'm also constantly looking at what I take out of our customers' amps.

My all time favorite is still the Svetlanna (now winged C), specifically from the late 90's into about 2001. After that, there was a production change that made the tube less reliable. I stopped stocking the Svetlanna because they became very expensive and at one point were not available at all. The Svetlanna sounded great and when it failed it did so in a very graceful manner. Which is good for an EL34 because many times they fail in a take no prisoners manner.

As our regular customers know, we have been using the JJ Electronic E34L for quite some time. My main reason was it's reliability. But sadly, in 2009 I had a lot of trouble with the E34L. Switching to the EL34 had some success. What changed? I personally blame international politics. JJ Electronics is in the Slovak Republic, a small Eastern European country that would like to enter the EU. What exactly does that mean for you and your EL34 tubes? Well, for one thing they are now lead and mercury free. Unfortunately, their EL34s are now less reliable.

But in my experience, reliability has always been a problem for the EL34 in guitar amps. I almost hate to say it, but... could it be the amps? Let's think about this for a minute. Two things quickly come to mind: First, Most EL34 amps want to be a Marshall, even if they won't admit it. Second, the first Marshall amps were basically Fender Bassman copies with EL34s. So that means all of our favorite EL34 amps are based on a modified 6L6GC design.

If you enjoy the thrilling excitement of searching through manufacturer's data sheets as must as I do, you might make note of two things about the EL34/6CA7: It is not recommended to be used in a horizontal position, and the maximum screen voltage is 450 Volts, approximately 50% of the maximum plate voltage. These two attributes are not shared with the EL34's 6L6GC brethren. So any amplifier design based around the 6L6GC is going to have a screen supply that will run an EL34 to its absolute maximum.

If there is anything I have learned from movies and television of the 1980's, it's this: If you buy an exotic pet from an old man in a shop full of far east curiosities, do not feed it after midnight and do not get it wet. Ever since the first Marshall we have been breaking the rules, yet somehow we are always surprised when we find gremlins.

The wholly impractical option would be to redesign most EL34 based amplifiers made in the last fifty years, especially the high plate voltage monsters of the late seventies and early eighties. If only there was a tube with big fat EL34 mid-range that didn't mind a high potential screen supply. Well, there is, and it used to be a lot more expensive than an EL34. I wouldn't say the KT77 has come down in price as much, as the EL34 is now more expensive. For that reason I completely overlooked the KT77 until a customer inquired about installing them in his Carvin X100. I had not realized that it was a drop-in replacement for the EL34/6CA7 that will take up to 800 volts on the screen supply.

We are now stocking two options for EL34 based amps. The JJ Electronic KT77 and the Groove Tubes GT-EL34R. Lately they have been the best two tubes to replace EL34s that I have found.

Sold!

2010-03-09T20:32:00.003-05:00

Kraken Rev 1.1 pedals are sold out as of today. Don't worry, Rev 1.2 pedals are comin' off the line! Also a beta test of the all Germanium Kraken yielded some smooth results. Like a steel gauntlet covered by a velvet glove. The germanium transistors have a very smooth refined sound, not a hint of fuzz. We are using a transistor similar to the Mullard OC72. We have a few of the Mullard transistors but they do not meet our spec. We have found that some of the Japanese and American transistors that we have in stock exceed the specification on the manufacture's data sheet. Although it is unnecessary we are only using the germanium transistors that exceed the data sheet spec. I hand full of germanium Kraken pedals will be available on Monday.

Kraken Rev 1.1 almost sold out!

2010-03-06T13:12:00.003-05:00

The first release of our Kraken Overdriver is almost sold out. That can mean only one thing. It is time for the release of Kraken Rev 1.2. If you would like one of the first Kraken pedals build on the boards that were hand etched by Kev and I, your time is very limited. We will however have plenty of the Kraken Rev 1.2 pedals. The new boards arrived this past week ahead of schedule. I'd like to thank everyone who has bought one of our pedals so far. You have helped bring this beast of myth and lore to life. So far it looks like there is no stopping this leviathan from dominating the seas of tone.

Late next week we should have a hand full of the first all Germanium Kraken pedals. We will be building them in limited runs along side the other pedals. They will sell at a $50.00 premium above the price of the all Silicon Kraken. All of the germanium transistors will be hand selected for optimum performance. I can't wait to hear just want they sound like. Considering that the first Rev 1.1 Kraken vastly exceeded my expectations, I'm sure that I'll be pleased.

If you haven't stopped by to check out the Kraken yet. By all means stop on by. They sell almost as fast as we make them. I hope we don't run out!

Kraken Overdrivers are Comin' off the Line!

2010-02-18T09:40:00.005-05:00

Here it is! Full Custom Music Repair's first pedal. The "Kraken"! Guarantied the best overdrive pedal you have ever heard. Forget 11, our gain control goes from calm seas to the full fury of Poseidon. Whether you just need a clean boost, bluesy overdrive or something heavier, the Kraken has you covered. The Kraken has a very amp-like feel and will even clean up when you roll down your guitar volume. Thanks to the use of an all Class-A, Discrete Transistor design. Also the active bass and treble controls are much more flexible than just a tone control. But wait, there's more. We are offering two stylish finishes, Tuxedo and Hazard County.

Our goal with this pedal was to design a pedal with the boutique tone of some of our best custom built amps but with a price accessible to everyone. I believe we have met or exceeded that goal. We will continue to keep the price for the Kraken down while improving it's quality.

For a limited time only we are offering the "Kraken" direct to customers at wholesale price. We will be looking for music stores to set up as dealers for this an other future Full Custom Music products.

Unleash the Kraken!

2010-02-12T15:57:00.005-05:00

Coming soon to Full Custom Music Repair!

"The Kraken"

Art by Todd"Sharkbait"Williams

The Hagstom II: Swede or Super Swede

2009-04-18T10:14:00.002-04:00

Yeah, I know, cool looking Guitar right? That's what I said when I saw this red royale. Is it a Teisco? Or, maybe an Eko? Awe, yes, Hagstrom.

I'm a sucker for weird looking Guitars, especially ones from this time period, which is about 1965. Hagstrom, along with other European manufacturers were starting to pickup on the phenomenon that was rock-n-roll, and revamping their music manufacturing facilities to switch from producing accordions, the biggest market at the time, to producing Electric Guitars. In the changeover and retooling of production, the manufacturers combined some of the "aesthetics" of the accordion, sparkly covering, lots of switches on the control plate, polka-dots and blended them into their own unique designs. These funky European designs were a unique contrast from the U.S. style of the time, Fenders utilitarian Telecaster, the more advanced Stratocaster (which was by all means non-traditional), or Gibson's "old world" style arch top/solid body designs. At first glance the Hagstrom II looks like a mix between Fenders Jaguar Guitar body style, along with the Fender style headstock shape, but with a double cut away horn and body contours of a Gibson SG. Aside from other subtle design features, lets take a look at what really differentiates Hagstrom Guitars from the others and that is the neck.

One of the first things that you notice when picking up this Guitar to play, is that the neck is really, really thin. Hagstroms were marketed to have really fast playing/feeling necks compared to other instruments and they were able to achieve this through their design of the truss rod. The truss rod is a steel threaded rod that runs through the center of the neck and is used to make adjustments in neck relief, or how much bow occurs when string tension is applied. A Guitar tuned to pitch averages about 120lbs. of pressure to the neck, making the truss rod a key component in counteracting this pressure, not having the neck resemble something like a ski-jump and more like a flat playing surface.

While most manufacturers were content with using a single truss rod, Hagstrom had to come with a new design in order to keep their thinner necks more stable. What they came up with is the "H" bar design. This design takes the existing truss rod, wrap it in steel and shaped to resemble the letter "H" (check out the photo). Not only does the "H" bar take care of potential Neck bow, it inhibits the Neck from wanting to twist as well ( a potential problem, if the wood wants to revert back to it's pre-Guitar form). Necks with this style of truss-rod are very stable and what I think is a clever design solution. So, how does it sound?

This Guitar came in with the electronics not working properly. Once I got the minor bugs worked out and proper components replaced, I plugged it into my Blackface Fender Bassman amp on a clean setting. The Swede sounds very Fender Mustang/Teisco Del ray like. The pickups visually resemble a p-90 but sound very Fender style single coil, with very low output. The neck pickup I particularly enjoyed as it had a scooped mid range with a more rounded top end and in adding the bridge pickup brought on more defined sparkly highs. The bridge pickup by itself sounded more along the lines of an am radio, which is par for the course with this style of pickup. The controls consist of an overall on/off switch, neck pickup on/off , bridge pickup on/off, tone on/off (instead of the usual tone control knob), a mute switch (which acts more like a rhythm/lead switch) and a single Volume knob. I was able to get sounds ranging from low-fi garage rock to a grittier blues sounds and everything in between.

The Hagstrom II is just a fun Guitar to play, backed by some serious design consideration. I would recommend anyone to pick one up, if they get the chance.

Ibanez Tube Screamer and the Maxon OD-9

2009-04-05T11:13:00.008-04:00

I have never really cared for the Ibanez TS-9. I've just never understood what people liked about them. But be fair, my first encounter with the little green box of voodoo was quite a few year after its historical debut. Let us start our discussion with a excerpt from a great book that we have at the shop on vintage effects pedals, titled The Stompbox.

The Ibanez story dates back to 1908, when Matsujiro Hoshino opened a book and stationery store in Nagoya, Japan. By 1932 Hoshino was producing guitars under the Ibanez name, and 30 years later the Honshino Guitar Company purchased half interest in a small American guitar firm called Elger that had been importing guitars from Hoshino and other Japanese companies.

Marketing manager Roy Miahara describes Ibanez's early pedal efforts: "When Ibanez CEO Tom Tanaka saw MXR stuff. We began making copies of it. In those days the Yen was 260 or 270 to the dollar. You didn't have to worry about marketing anything, You could just bring it over here and make tons of money on it. Nisshin made all of Ibanez's pedals, and they also owned the name Maxon.

One of Ibanez's most famous effects was the TS-9 Tube Screamer, medium-gain overdrive unit designed to emulate the sound of a tube amp. Designed by Nisshin in the early '80's and made legendary by Stevie Ray Vaughan and Eric Johnson, the TS-9 was essentially a repacked version of an earlier Ibanez/Nisshin hit, the TS-808. The only difference between the them are the values of the two resistor in their output; a TS-808 has a 10kΩ resistor and a 100kΩ resitor, while the TS-9 uses 100kΩ and 470kΩ resistors. "I don't think I used the TS-9 the way they made it to be used," Stevie Ray told Guitar Player in 1983. "I have it set so it makes everything sound turned up."

Back to present day, we can find the Tube Scream of legend and myth in the Maxon OD-9 Made in Japan by Nisshin to the original spec complete with the JRC4558 IC chip. We ordered a few in at the shop to check them out. They are very well made and sound like the best examples of the vintage Tube Screamer that I have heard. But I still do not like the compressed high end and lack of clarity. The circuit itself is not a bad design, that I like. What I do not like is the JRC4558. Yes, I know that chip has more voodoo rubbed on it than a team of Haitian witch doctors could supply. But Nisshin didn't select that IC for any other reason than that it was inexpensive, stable and readily available. There were other ICs used in the TS-9 but the JRC4558 was the best IC chip that Nisshin used and is very appropriate for a reissue.

My taste is to upgrade this pedal to something a little more refined. We tried a modern IC chip by Burr Brown with a few other tweaks. The results were very pleasing. Opened up the high end, clearer mids, fatter lows, plus a touch more gain.

Our research has convinced me that the Maxon OD-9 deserves a home at Full Custom Music Repair both modded and stock. We also have a few other effects pedals in stock as well, some used and some new. We will be expanding our inventory of vintage, new and modded effects as per customer demand.

A Word About Biasing

2009-03-13T09:58:00.011-04:00

I'm asked about biasing tube amps quite frequently. And often my dilemma is how much information do I give and just how to package it? I have always like how Aspen Pittman, founder of Groove Tubes explains biasing. Here are a few excerpts from Groove Tubes Reference Guide, published circa 1983.

The bias control on an amp is much like the idle control on an engine. That is to say, there is an optimum point of bias for an amplifier that allows for good sound and maximum tube life. This optimum bias point will be different with a new set of tubes no matter which tubes you buy so the bias should always be checked when changing power tubes. (pre-amp tubes are self-biasing)

"Under Biased Amp"

Amp is "idling to high" so tubes are running too very hot causing them to burn out fast and possibly to short-out. The tubes plates (large gray metal housing) will glow red from heat and amp will lack punch and might hum. The orange GROOVE TUBES paint will turn brown rapidly if amp is under biased.

"Over Biased Amp"

Amp is "idling too low" so tubes are running cool. Amp will sound dirty at any level and will sound low on power. This type of distortion is called "cross-over" distortion. Cross-over distortion is a non-musical type of distortion and isn't as pleasing to hear as "harmonic distortion".

"Correctly Biased Amp"

Amp will sound clean and tight at low to medium levels. When pushed to to maximum , amp will produce an even harmonic distortion---musical distortion if you will.

Biasing an Amp W/Variable Bias Control

The proper method of biasing a tube amplifier requires a signal generator, an oscilloscope, a volt meter and preferably a dummy load resistor. First, remove power tubes and measure the bias voltage at the grid (usually pin 5). Adjust the voltage to the largest negative voltage and install power tubes, the tubes are now at the over-biased position and are running cool with lots of cross-over distortion. Now apply a 2000 cycle signal to the input of the amp and connect the proper impedance load to the output. Turn volume of the amp up to 70% output and get a picture of the signal on the scope, notice the notch indicating crossover distortion in the signal. Adjust the bias control gradually until this notch just disappears. The amp is now properly biased.

The method described above is called "Cross-over Notch biasing". It is my main method for biasing both vacuum tube and solid state amplifiers. Yes, that is correct your solid state amp has a bias too. The great thing about the cross-over notch method is, it works every time with anything. The drawl back is, you need knowledge and experience of what class amp you are working on (A, AB or B) and just how that amp should run.

Amongst the inexperienced the "Current Drawl" method, made popular by Gerald Weber of Kendrick amplifiers has become widely popular. There is nothing wrong with this method if you are using the same model amplifier and same exact tubes. Even different brand 6L6GC tubes will bias a bit, well different. The problem with the current drawl method is that it employs the use of an "arbitrary specification". Amplifier and tube designs very widely. I do some times use this method, but only because I have the knowledge and experience to devise my own arbitrary specifications for common amplifiers that are often seen in for repair.

I hope this answers some questions. With tone there is no Voodoo, only science.

For more on Gerald Weber, Groove tubes and some good reference material, check out A Desktop Reference of Hip Vintage Guitar Amps, by Gerald Weber.

*disclaimer*
DO NOT attempt to bias your amplifier unless you are qualified to work on electronic equipment. There are LETHAL voltages inside of your amp that can kill you, kill you dead!

National Reso-Phonic, I'm hooked on it.

2009-03-09T17:49:00.009-04:00

This piece of awesome came in a few days ago for a little tweaking and a general all around maintenance. It is a National Reso-Phonic but instead of the usual Dobro acoustic full-body style, it is more styled after a LP Jr. and the body is completely covered in "mother of toilet seat" style Cream pearloid. The Guitar has a short scale 22" neck, making use of heavy gauge strings a snap when playing in your favorite delta open tuning and still utilizes the National single-cone system.

The body is about the same thickness as a LP Jr, dialing in at just under 2 inches, making tight quarters for the cone system to fit into the body cavity and work properly. The lack of a proper pickup system, of which I will install at a later date, only enhances the challenge of getting the cone moving for good volume output. You gotta dig into it with all your soul, but you will be equally rewarded for your efforts.