# Blackface mod, is it necessary?



## fishin' musician (Jun 19, 2008)

Hi all, the latest issue of Guitar Player did an article on how to convert a Silverface Fender to pre-CBS Blackface specs. The mod seems simple enough but my question is this: What diffence will it make to the sound of my 1970 Bandmaster Reverb (or any Silverface Fender for that matter)? 
Anyone have thoughts on this subject?

Thanks, Dwayne


----------



## greco (Jul 15, 2007)

fishin' musician said:


> Hi all, the latest issue of Guitar Player did an article on how to convert a Silverface Fender to pre-CBS Blackface specs. The mod seems simple enough but my question is this: What diffence will it make to the sound of my 1970 Bandmaster Reverb (or any Silverface Fender for that matter)?
> Anyone have thoughts on this subject?
> 
> Thanks, Dwayne


Glad you aked this..I've always wondered the same thing myself.

Dave


----------



## Ripper (Jul 1, 2006)

It is dependant on the amp and the year. Some of the silverface amps were still blackface circuitry into the mid 70s. My buddies 73 Deluxe is still blackface on the inside and it's never been touched. My 69 Vibrolux Reverb was 90% blackface except for some minor changes in the phase invertor circuit and the bias control.

It's really a matter of personal preference, there are some really great sounding silverface amps that in my opinion don't need to be modded back to blackface specs. Where things get tougher is when you get into the later silverfaces that have the ultralinear output trannys and bigger higher voltage power trannys is where it gets tough to really blackface the amps.

There are some good mods for silverfaces out there too that can improve the sound of the amp if you feel you need it.


----------



## nonreverb (Sep 19, 2006)

Ahh...the perennial question: to blackface or not blackface. Well it really depends on the era of silverface. As stated already by Ripper, it's a personal thing. The one exception to that rule would be the late large silverface amps. They unfortunately cannot be "blackfaced" as the output stage used an ultralinear design. For some amps, there are some simple mods that can be done easily to get them closer to a blackface amp. First would be swapping out the 5U4 rectifier tube for a 5AR4 found in most mid-size amps. Another would be to remove the snubber caps found on the output tubes. This one I would suggest having a qualified person do...just in case. The other mods are a little more involved such as the phase inverter mod and, on later amps, the bias pot mod. 
Again, if you like the sound of your amp as it is now, don't worry about the blackface mod....you never know...it might not sound as good to you after it's modded


----------



## mhammer (Nov 30, 2007)

Keep in mind that a great many changes to Fender amps over the years were intended to "improve" the quality of the sound. Keep in mind as well that, 40-50 years ago, "improve" meant remaining as clean as possible even near the top of the available output range. Naturally, in a music culture that values easy breakup as much as the current one does, such "improvements" are not always welcome.


----------



## Ripper (Jul 1, 2006)

Over the years I've found there isn't as much to the 5U4 to GZ34 swap as some make out. When swapping out the rectifier tube you are going to increase your plate voltage sometimes by a lot which is more than some circuits are built for. Why the 5U4B to GZ34 swap seems to make a difference right off the bat is that most silverface with tube rectifiers were biased from the factory a little on the cool side and don't have a true adjustable bias supply. If you change it to a variable bias and warm the bias up a little you'll find that it raised the B+ some, which increases the idle current which in turns gives you that warmer fatter tubey sound we all love. It also allows you to keep using the much cheaper 5U4 rectifier tube. I've found alot of the new GZ34s are no where near as robust as the older tubes and tend to fail alot sooner. There are tons of NOS 5U4s that can be had for cheap. GZ34 means more clean headroom, 5U4 means a bit more sag, which alot of players love. Mission amps recommend staying with the 5U4 and warming the bias a bit in 40-50watt fender amps.

Now with your amp, it's interesting that if you look at the fender schematics, even the old tweed bandmasters used 5U4s. Then in the blonde/blackface era they went to a solid state rectifier and in 68 when the bandmaster reverb came out they went back to using the 5U4.


----------



## fishin' musician (Jun 19, 2008)

Well, seems I've opened a can of worms :sport-smiley-002which is okay since I love fishin' too).
There is alot of good advice so far. I think I'll blackface in stages, starting with the switch to a variable bias, staying with the 5U4 (thanks for the info Ripper).
In the end I'll probably source out a GZ34 and ultimately do the conversions to the phase inverter and remove the caps from the tube sockets. But I'll give the amp a good ear test after each step and decide what sounds best for the country/punk/jazz/ska/blues/metal style that I like to play.

Now, how about power tubes...errr, maybe that needs its own thread...

D


----------



## Ripper (Jul 1, 2006)

fishin' musician said:


> Well, seems I've opened a can of worms :sport-smiley-002which is okay since I love fishin' too).
> There is alot of good advice so far. I think I'll blackface in stages, starting with the switch to a variable bias, staying with the 5U4 (thanks for the info Ripper).
> In the end I'll probably source out a GZ34 and ultimately do the conversions to the phase inverter and remove the caps from the tube sockets. But I'll give the amp a good ear test after each step and decide what sounds best for the country/punk/jazz/ska/blues/metal style that I like to play.
> 
> ...


The Phase invertor changes (cathod and plate resistors and the coupling cap)you'll notice the become more lively with this change) and the Bias are the ones I'd start out with for sure. Get rid of the suppressor caps on the grids of the power tubes, it helps give back some nice sparkle. 
Depending on what caps are in the tone stacks etc you might want to change those out. If they are the dull browny-red looking ones change them out for some spragues, it helps, if they are still the blue ones, leave them.

One thing to remember though, is that blackfacing will take some of your clean headroom so if you are someone who wants allthe clean headroom it might not be for you. There are lots of silverface amps that sound damed good with just having them rebiased a little warmer.

Tubes, I run old RCA blackplates in mine, but I've had good luck with JJ's and SEd tubes in them as well.


----------



## fishin' musician (Jun 19, 2008)

Already swapped out the so-called "chocolate drop" caps (Mallory caps from Torres Engineering) and the filter caps. I won a Mercury Magnetics choke and OT that I'm excited to put in. 
The amp itself was stuffed into the speaker cabinet years ago, so if anyone knows where I can get my fingers on an empty Bandmaster Reverb head cabinet...
As for power tubes, I'm still running the original RCA's (grey plate). They may still be fine but I would like to try another set of tubes so I can AB them and see if the old RCA's are still up to scratch.


----------



## Ripper (Jul 1, 2006)

Before a/bing the tubes, do the phase invertor and bias mods, then rebias and try the RCAs and then try your new set.


----------



## nonreverb (Sep 19, 2006)

Another consideration regarding Silverface amps and tone is the speakers used. The one that comes to mind is the silver/orange Utahs used by Fender in the mid 1970's. Not a very good speaker IMO. If you're one who likes the way your amp sounds with the origional speakers then great! You're probably one who isn't interested in blackfacing then either. Changing the speaker/s is as important as blackfacing in some cases. The amp will have a different response and tone...more often than not, for the better.


----------



## Ripper (Jul 1, 2006)

nonreverb said:


> Another consideration regarding Silverface amps and tone is the speakers used. The one that comes to mind is the silver/orange Utahs used by Fender in the mid 1970's. Not a very good speaker IMO. If you're one who likes the way your amp sounds with the origional speakers then great! You're probably one who isn't interested in blackfacing then either. Changing the speaker/s is as important as blackfacing in some cases. The amp will have a different response and tone...more often than not, for the better.


+1 on that too, those utahs never sounded good to my ears. The mid/late 70s fender branded eminences weren't too bad.


----------



## fishin' musician (Jun 19, 2008)

nonreverb said:


> Another consideration regarding Silverface amps and tone is the speakers used. The one that comes to mind is the silver/orange Utahs used by Fender in the mid 1970's. Not a very good speaker IMO. If you're one who likes the way your amp sounds with the origional speakers then great! You're probably one who isn't interested in blackfacing then either. Changing the speaker/s is as important as blackfacing in some cases. The amp will have a different response and tone...more often than not, for the better.


I have to agree with you, the Utahs have an awfully flabby bottom end and will be replaced once I return the amp from its current combo form back to its head/cab configuration. I would like to find a nice set of vintage P12N's or C12N's (or maybe a combination of the two?). It all depends on what I find, mind you I have been seeing alot of positive comments about Eminence speakers...
Ahhh, the options...


----------



## Emohawk (Feb 3, 2006)

+1 on the newer Eminence speakers. I just built a Deluxe clone & dropped a Texas Heat into it. A little warmer sounding than a couple of other speakers I tried, but still nas a nice chime to it.


----------

