Machine Gun Amps
Blackface amps vs.
Silverface amps

There is a lot of talk about modding a silverface amp to blackface specs. Click on the link to read more about it.

Fender made some "blackface" amps in the early 80's that aren't really "blackface". These amps have master volumes and sometimes channel switching which were NEVER features of vintage blackface amps. If you have one of these, then they are either the late silverface models with different cosmetics, or the hotrodded ones designed by Paul Rivera (ie the 1x12 or 2x10 Concert, Super Champ, etc). There are also some solid state amps that look "blackface". Beware of someone trying to sell these to you as a "blackface" amp. They are decent amps, but not really what is generally known as "blackface"!

My dates throughout will be a little vague, but are a good starting point. Fender started producing blackface AA763 amps in August '63 I believe. AA763 was the first circuit that Fender used and didn't last long. Soon after the circuit became the famous one, the AB763. The AB763 had some minor but important updates. Amps such as the Pro Reverb (AA or AB165, came out in late '64) and the Vibrolux Reverb (AA864, came out in late '64) are identical to AB763 circuits and are still considered the "good" ones. Blackface amps had a brighter, tighter, and more "scooped" sound than the brown amps that came before. Leo was trying to go for a cleaner and more "hi fi" sound. Hi fi may be misleading, because Leo still had his ear to the ground and did what musicians wanted for sound it seemed. Leo sold Fender in 1964, and the new company, Fender Musical Instruments (owned by CBS) took over on January 1, 1965. Amps made before this time all had "Fender Electric Instrument Co." (FEI) on the front panel, or some variation of that. Then the "Fender Musical Instruments" (FMI) panels started to get phased in. FEI panels can still be found as late as mid '65. But if your amp says FMI, it is a '65 or newer for sure, and was made by CBS. Quality in the blackface amps stayed consistent and good up till the end as far as I have seen. Silverface amps started coming out in mid '67 and lasted until about '81 when they switched back to "blackface" cosmetics for a very short period of time (these amps don't look or sound like the old ones). Silverface amps outlasted blackface amps by far, they were in production for more than twice the time blackface amps were. I also have a notion that silverface amps were produced in much greater quantities per year than blackface  up to the last few years of production of silverface amps.

There were some changes that the amps went through that were almost universally not well received. I'll outline some of them here.


Speakers: Blackface amps generally have better speakers than silverface. FMI blackface amps usually have a better chance of having a Jensen speaker(s) in them than the FEI's in my experience. Other speakers that came commonly in blackface amps were CTS's (most commonly in Super Reverbs, but my '63 Pro has one) and Oxfords, which came in just about everything else. But when the silverface years came around, Oxfords, Utahs, and later Rolas were the stock stuff usually. Fender offered JBL's as a factory upgrade. They are fairly rare in blackface amps. I believe that a lot of the Vibroverbs from '64 came with them. I think a few blackface Twin Reverbs came with them and maybe even a few Super Reverbs. I've heard of one Vibrolux Reverb that came with them. Sometimes you can find blackface and silverface amps with JBL's, but they are rare comparatively. Super Reverbs with JBL's are a rare treat. I'm not sure if I prefer their sound to Jensens (I had a SF SR with JBL's), but it's a cool sound. Silverface Twins came with them much more commonly. Speakers in silverface amps were pretty much all dismal sounding except for the JBL's. Any decent speaker you can put in a silverface amp will almost certainly sound better than what came stock. Blackface amps with Jensen speakers are my favorite sounding for sure. My favorite blackface amp of all time is a '64 Super Reverb that came stock with Jensen C10R's that belongs to a friend.

Lead dress: In the silverface years by about mid '69 to '70, Fender went completely to plastic sheathed wire. It kind of looks messy when compared to cloth covered wire. The way the wires were laid out (lead dress) was certainly messier than the older amps. When you start getting into the late '70's, it gets pretty ridiculous compared to blackface. Does this affect tone? It could. Putting a blackface chassis and a silverface chassis next to each other is striking. Blackface amps were wired with far more care and precision.

Circuits: Almost immediately after the amps went to silverface cosmetics, FMI started making changes to the circuits. These changes were not welcome at all. Some amps got big resistors on the cathodes. These amps were operating in cathode and fixed bias mode at the same time. They did not sound as good as the earlier amps. This configuration only lasted about 6 months to a year I think. Fender took the cathode resistors out, but still modified the phase inverter, bias supply (balance instead of level) and reverb circuit. They also went to 5U4GB rectifier tubes, which either sag more or sound mushy depending on the way you hear it. I'm not a fan of 5U4GB's. Most amps had caps on the grids of the power tubes. Usually a .002 or 1200pf going from pin 5 to pin 8 on the tube socket (grid to cathode-ground). These were installed to suppress oscillation at "higher" frequencies than what you need for guitar. This turned out to be not true. These caps rob the amp of some high end detail. One other change that I particularly don't like is the change to a .01 coupling cap to the phase inverter. The started doing this in the early '70's I believe. This makes the bass response flabby to my ear. A note on AB763 and silverface amps: If your tube chart says AB763 but you have a silverface amp, don't automatically assume it's the blackface circuit. There is a better chance than not that you have a silverface circuit in your amp. There is no way to tell if you have a blackface circuit by looking at the amp from the outside. The only way to tell is to open it up. However, if you own a silverface amp produced in '67 or early '68, then the chance of it being AB763 is very good. I still recommend opening the amp to find out though. I have heard of a way to tell cosmetically if you have an AB763 amp, but I've never witnessed this and I won't try to explain it until I see it with my own eyes.

Component quality: The general quality of components used in silverface amps seemed to go down. The coupling caps on the circuit board went from blue Mallorys to the chocolate drop looking ones. These caps are generally talked about with great disdain by techs and tone mongers. I've recently done an A/B test with the chocolate drop caps compared to Sprague Orange Drops. The Spragues are noticeably nicer. The only way I can describe the difference is that the amp seemed "numb" with the chocolate drops. Some blackface amps, such as the Champ, did use these brown caps sometimes. The rectifier tube went from a GZ34 to a 5U4GB. The 5U4 is a cheaper to produce tube than the GZ34 and it sags more. Some people like this. This is arguable, but transformer quality seemed to suffer as well. Cabinets went to particle board instead of pine (more on that below). I think the general image of the amps just went down in the silverface years. Everything just got progressively a little worse.

Cabinets: Sometime in the mid '70's, Fender went to particle board construction throughout the amp. The amps were solid pine with a particle board baffle up to that point. There is a lot of debate on what actually sounds better, but I'd have to believe that there is something to the pine cabinets. Curiously, Fender did use particle board for the speaker baffle from the beginning of blackface production. All brown amps that I know of do have plywood baffles, and then they suddenly switch to particle board in mid '63 for the blackface amps. It's curious that the baffle was the only place that they used the particle board. Maybe Leo tried a particle board cabinet but didn't like the sound? Fender went to a velcroed on baffle that held the grill cloth sometime in the mid '70's. This is actually a convenient way to do it, it makes it much easier to change speakers. But, these grill cloth baffles have some rattling problems in my experience.

Master volume/pull boost: Fender put master volumes on amps starting in 1972. I believe the 100 watt amps all got them this year. Then most of the rest of them got them by about 1975. The master volume is right before the phase inverter just like a Marshall. The pull boost feature came in about 1975 as well. This feature can be activated by pulling out on the master volume control. What it did was take some of the signal routed to the reverb circuit and route it around a series resistor to get more gain. The master volume and pull boost features are pretty useless in reality. It seems Fender was trying to make a nod to the popularity of Marshalls, but these features they added did absolutely nothing to make the amp sound like a Marshall, or even sound good! I haven't met anyone that uses the master volume and pull boost on a Fender to get distortion. Trying to get distortion this way sounds far worse than any pedal, $10 pawnshop ones included. The good news is that these features are easily defeated. The pull boost does nothing to the circuit when it's not engaged. The master volume can be easily bypassed by adding a jumper from the junction where it originates to the coupling cap to the phase inverter and then removing the wires that go to the pot. The effect of the master volume is like adding a 1 meg resistor to ground. Even when you have the master volume all the way up, some of the signal is being bled off to ground.

The late '70's early '80's changes: Amps larger than the Vibrolux Reverb built from about '77 to about '81 when the last of the "silverface" type amps existed had some major changes done to them. They got higher voltage and current power transformers, and ultralinear output sections. The power supply is also beefed up. These amps have no hope of ever sounding like their vintage brothers. The dead giveaway on these is the wattage printed under the speaker jacks. If it says 70 or 135 watts, then it's the later model. Amps that had the rectifier tube such as the Super Reverb and Pro Reverb no longer had it at this time. These amps are generally not very good sounding. I do like the 135 watt models for certain things though. For instance, since they are very clean sounding they do work good for country or steel playing. With some changes to the circuit, they can sound good, but still not like the old ones. Amps that are the 70 or 135 watt variety should be worth less, and is a bargaining point if you really want one. If you play bass, then the Bassman 135 is a bit of a better bass amp than the 100, but still grossly underpowered if you want to fill a big room. For a more intimate gig, it may be just the thing (after it's been gone over by a tech of course).

So, the final question: Are silverface amps all that bad? No. They are Fenders, so they are still better than most amps! I tend to hold them against some unfair competition, namely the blackface amps because blackface is my favorite of all time. Silverface amps were made by a company that didn't care as much about tone or quality, so they are going to suffer for sure. Still, as long as you don't have one of the later ultra linear models (70 or 135 watt), then your silverface amp can be made to sound very good, about 95% of the way to blackface. I'll go on record and say that the best Twin Reverb I ever heard was a '70 that I converted to blackface. I had my own Quad Reverb, a '64 Twin Reverb (blackface), '66 Twin Reverb (blackface) and the '70 (silverface) all side by side plugged into my Quad speakers (4 16ohm Jensen C12N's). The '70 was the best. Amazing, but true. Which is not to say that I think the '70 Twin Reverb is the best of them, but that particular '70 Twin Reverb was to my ears.

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Last updated 12/01/2001