"Serious Tone for the Serious Musician"

Killer Tone Underground Newsletter

     Things are hopping at Griblin Engineering! It seems that when you talk about ways to obtain killer tones that there are musicians that come out of the woodwork who are hungry for this kind of information. In fact, those of you who used to be able to talk to me at just about any time have found that that’s not the case anymore. I am involved in so many projects, both inside and outside the shop, that it has become necessary to set up some guidelines to help keep things running smoothly. First, if you know what you want to order, use the toll free number (1-800-605-2677). If you have any questions about the products you are ordering (or have ordered), I strongly recommend you e-mail us at Griblin@aol.com or fax us at (415) 456-3947. These are the fastest and most efficient ways to get the answers you need. If you need to reach me by phone, you will need to call the tech line at 415-456-2677. In general, I try to make myself available between 4:00 PM and 5:00 PM PST. If you can’t call at this time of day, leave a message at the tech number. Try to be specific with your questions so that If I call and you’re not home, I can leave a response for your question. I’ll try to get back to you within 48 hours. Note: we are not a free information service. If it’s not business related, you probably won’t get a response. Sorry, but there just isn’t enough time to solve everyone’s problems.

Silverface vs. Blackface

     Apparently there is still a little confusion about the differences between Silverface and Blackface Fender amplifiers. It seems most players know that the Blackface amps cost more and supposedly sound better, but don’t know much more. Here’s a little information to help you understand the difference.

     On January 1, 1965, Leo Fender handed the keys over to CBS, Inc. and in doing so created a distinction that is still noted today among guitar players, guitar and amp collectors and music historians. Technically speaking, all instruments sold from this date forward (until early 1985 when the company was sold again) were given the stigma of being CBS-era instruments, while instruments sold prior to this date were given the more preferred pre-CBS designation.

    So what does this CBS/pre-CBS distinction mean, and how does it tie in with Silverface and Blackface amps?

     In 1965 when Fender was sold, they were producing what are now referred to as the "Blackface" amps. These were and are great sounding amps that were given this nickname due to the black faceplate that was used during this time; the faceplate being the metal plate that the controls - volume, tone, effects - were mounted to. To many people the term Blackface is synonymous with being pre-CBS although this is technically not accurate as the Blackface amps continued until sometime in 1967, well after CBS took over. Around 1968, the first noticeable changes implemented to the tube amp line by CBS surfaced. This was the birth of the Silverface amps. Externally these changes consisted of the changeover from a black faceplate to a silver one with blue lettering and a newer blue, white, and silver grill cloth with an aluminum trim. But what about internally? Since the only important changes to an amplifier are the ones that affect the tone, what makes these amps different from their Blackface counterparts?

     The mystery behind these amps is the gradual changes that were made to them over the years, some good and some not so good, that ended up transforming them into a very different creature than they started out. These changes were not made universally to all the tube amps in the Fender line. Changes in a 1976 Twin Reverb, for instance, might not necessarily be applied to a Deluxe Reverb of the same year. With all the changes that were implemented through the Silverface years sometimes it’s hard to tell what kind of amp you have until you open it up and take a look inside to find what specific changes were made. The following are some of the more important changes:

     Capacitors - If you were going to reduce a tube amp down to it’s most basic components, these would be the transformers, tubes, wires, resistors and capacitors. Fender has used a number of different capacitors through the years. Generally speaking, if you have the blue colored caps, you have the good ones, although how well they are performing now may be questionable. If you have the brown caps, you have the lousy ones and are paying for it with substandard tone - poor frequency response, less definition, somewhat "lifeless" sounding. If you have these brown caps, do yourself a favor and book an appointment with your amp tech to have him change them. You’ll notice the difference.

     Driver/Phase Inverter - CBS, Inc. took the idea of building amplifiers a little too seriously at one point. They decided to implement some changes based on the idea that an amplifier should not distort or color the sound, just amplify whatever was plugged into it. This is fine for a hi-fi stereo amplifier, but not for a guitar amplifier. The result was a re-worked driver/phase inverter circuit that was padded down to reduce gain and distortion (two things that guitar players like) and in the process created a less dynamic amplifier. Fortunately, this is not something you have to live with. Once again, take it down to your tech and have him put in the older Blackface circuit.

     Transformers - This goes hand in hand with the circuit change mentioned above. In adopting the philosophy that amplifiers should be clean, and that distortion should be greatly reduced, CBS introduced some newer power and output transformers in the later 1970’s on certain models - the 135 watt Twin Reverb and Bassman 70 come to mind. The newer power transformer brought more voltage to the tubes creating more headroom, more top end, and reducing distortion. Additionally, the larger, more efficient output transformer made the amp louder, cleaner, and helped prevent the transformer from reaching a point of saturation. It should be noted that these transformers were technically more advanced than the previous ones used on Fender amps. Once again though, this did not necessarily make a better sounding guitar amp. If you have one of these amps and want it to sound like a Blackface, you will be somewhat prevented from doing so by these transformers. The circuit changes can be implemented and the amps can be made to sound much better, but these transformers will make for a cleaner amp. The transformers can be swapped out for something closer to the Blackface, but you’ll have to part with a larger chunk of cash.

     Wiring - The Blackface used the very cool-looking cloth covered wire, whereas the Silverface used plastic insulated wire. There actually in an advantage to using the plastic insulation as it is not prone to absorb moisture as can happen with the cloth wire. Additionally, some of the Silverface amps used shielded wire in place of some of the longer wires (the ones coming off the input jacks and volume controls) which helped in noise reduction. Now for the downside. Some Silverface had the wiring routed differently inside the amp chassis which could cause the amp to become unstable as it allowed a parasitic oscillation to occur. The quick fix was to add a small value cap from the grids on the power tubes to ground. This fixed the oscillation problem, but sucked up a healthy dose of the top end. Many times you can remove this cap or replace it with a smaller cap. Get rid of it if you can.

     Master Volume and Pull Boost - In the early 1970’s, Fender added a master volume to their more powerful amps, and eventually added this control to other models with lower power as well. Unfortunately, since the amp design had been changed to prevent distortion, the master volume didn’t do a whole lot except steal a little more tone away from the amp. Later, a master volume was added that was built on a push/pull pot that would kick on a gain boost when pulled out. Once again, it wasn’t a very usable feature as most people did not like the sound of this boost.

     Bias Adjustment to Bias Balance - Most Blackface amps had a bias adjustment pot to make the job of setting the bias a lot easier. The Silverface amps took a little different approach and rewired this control as a bias balance adjustment (and also padded down the circuit in the process). This would allow you to use unmatched tubes by allowing you to compensate for the differences of the tubes with the bias balance pot. However, this control doesn’t allow you to set the bias correctly, it just allows you to adjust both tubes so that each have the same bias voltage. The act of setting the bias correctly is a little more cumbersome since you will have to substitute resistors instead of adjusting it with a potentiometer. Since it is common to purchase tubes in matched duets and quartets there really is no need for this type of control and it is typically rewired to serve as a bias adjustment control.

     Hum Balance Control - The Blackface amps did not have an adjustment for this, although some models used a couple of 100 ohms resistors to do much the same thing. This gives you a potentiometer to keep the AC hum from the filaments at a minimum. It’s actually a pretty good idea, except that they sometimes burn out and create more hum.

     For those tone-conscious musicians out there who want to convert your boring Silverface amp into the much better sounding Blackface circuit, we’re about to release a kit for you. Called "The Definitive Blackface Kit" you will probably read about it in the upcoming Guitar World Buyer’s Guide. This easy to install kit will restore the gain, warmth, and harmonic content missing from most Silverface amps. It even has some improvements beyond the original circuit which means that this kit can improve your Blackface amp as well. Price for this kit is $24.95.

     How did it turn out? "This is one of the best amps I’ve ever heard, and I’ve probably heard them all. There’s nothing I can’t play with it. I can do blues, rock, country, jazz - all with one amp. The clean channel has a great vintage vibe to it and is really full sounding, but without the muddy bottom end that a lot of old amps have. And the overdrive is so good I can leave my distortion pedals at home. The overdrive has plenty of gain and warmth without any unnatural fuzziness. Lots of sustain, plenty of crunch and it responds according to how you play your guitar. Why don’t they build ‘em like this from the factory? From now on, you’re the only one who touches my equipment.............Stephen Christopher, Chuck Day Band

- Mark Williams, Philadelphia, PA

"I ordered, received, and installed my Custom Wiring Harness with Lindy Fralin pickups. I was initially hesitant about ordering this kit due to its high price and my unfamiliarity with your company. My concerns were immediately put to rest once I actually heard the guitar. I just wanted to send you a letter of praise, (something I never do). The wiring was immaculate, tonal control excellent, and the pickups.... What can I say? You said they are, "The best single coils on the planet." I agree. Rich, full, shimmering. Magical is a word that comes to mind. Installation was a snap, even without instructions. So, thanks for an excellent kit, keep up the good work".

W.L. Van Zandt Dies

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