Written By: Jac Harrison
I have been told by more than one person that I am nuts, crazy even disturbed when it comes to my passion/OCD for tone. Some guys can go their entire life chasing a sound and never get it just right -- but I'm one of those lucky SOB's that knows the tone my soul desires, and more importantly -- how to achieve it. Growing up in a musical household I had a jump start on refining my palate by using and abusing my fathers guitars and amps for many years, on a side note... sorry dad. After destroying a few guitars by "trying something new" -- I had found that a (2) humbucker setup is what I'm all about, but when it came to my amps I had been all over the map until a few years ago. When I was younger (and knew everything) I was a full stack, dark el84 with many digital effects player -- but after countless shows and studio hours I found that a simple and clean foundation is what I needed to achieve my golden tone. I wanted an amp that was touch sensitive with a clean but warm high end that I was able to control the breakup/tube saturation by using my guitars volume knob and/or a class A boost opposed to an OD pedal. I spent the better part of a year playing every amp I could plug into and came up with my "formula". Turns out that I am either what I call a simple 6L6/6V6 (an amp with very little controls) or an el84 player if the amp has a presents knob/bright switch and mid shift. With my new found knowledge I went out and picked up a Fender Supersonic 22 and I enjoyed her until she picked up a really bad smoking habit, so we went our separate ways a little over a year ago. Heart broken, I went out and found an amp that I loved form day one -- a Bogner Alchemist 2x12. This amp had a lot going for it except one thing, Line 6 customer service. The Bogner was suppose to be the amp in this rebuild story and it was going to focus on how to get your amp studio ready, but when I called Bogner to get a schematic they told me to contact Line 6 -- and after two weeks of bullshit from Line 6 I decided to go in another direction with this rebuild.
Needing some direction, I contacted the man with the beard that lives in the woods that builds amps aka Jamie Simpson from Booya Amplifer Services in Lake Hopatcong NJ -- whom I have dubbed the "tone oracle". I explained to him what I was looking to do and he gave me a few ideas to work with. Now that I had a list of amps I could buy that Jamie could mod to give me my desired tone, I spent the next few days on the phone with every retailer in NJ tracking down a suitable amp for this project. I played a few different vintage amps until I found the one that I though had the best tone, a 1972 Fender Bassman 50. After a quick once over and some negotiating -- I was the proud owner of a brand new (to me), dusty and sticky 1972 Fender Bassman 50 head. Now that I had my newish amp I needed to do two things. First I needed to get this old girl some new parts including an extension cab with speakers, and she needed an appointment with Jamie from Booya Amplifier Services ASAP. So this feature story will be a step-by-step instruction manual on how I rebuilt my 1972 Fender Bassman 50, making her better than new.
Step one: Do Your Research.
Just because the person selling you an amp (or anything at that matter) tells you something, it does not automatically make it that. For example; I was told that this amp was a 1974-76, but when I called Fender and gave them the serial number I was told that it was built in February of 1972. Once I had the information I needed, I found the wiring schematic for this particular amp and made an appointment with Booya Amplifier Services.
Step two: Make Sure Your Amp is in Full Working Order Before You Do Any Modifications.
I can rebuild a guitar with my eyes closed, but when it comes to amplifiers I'm not the best. So besides the modifications, I had Jamie form Booya Amplifier Services give her a once over, and she passed her exam with flying colors.
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| Jamie Simpson from Booya Amps removing my "death switch" |
Step three: Mod the Crap Out of This Old Lady.
This amp was great, but there were a few thing I need taken care of right away. First, the "Death Switch" needed to be removed. This was not something that I was aware of until Jamie from Booya told me about it -- but basically to sum it up, old technology = very bad for a vocalist. I would have become the amp ground while playing guitar making me dead, and I can't play guitar if I'm dead so that would suck. This is something that I did not know about and would have not removed if I did not have a pro look at it.
My next mod was a master volume. This amp is effing loud, and did not have one. I guess it started many fights between band mates and/or sound guys in the 70's since Fender added one to the faceplate in 74ish'. I did not wat to "ugly" this amp up by driling holes in her faceplate, so Jamie used the stock hole in the rear panel from where he removed the "death switch" making this old lady retain her distinctive look of an early sliver face.
It was a great feeling knowing that I wasn't going to get electrocuted from a faulty vintage ground circuit, and that I had my much need master volume knob, but Jamie also had a trick up his sleeve to open her up a little more by removing what he called the "low end farts" (I believe that is a technical term). He replaced the first preamp stages cathode bypass caps with 10uF, down from the original 25uF, pre phase inverter master volume. Once he was all done with the mods we plugged her in, opened a few beers and made a video... it all gets fuzzy after that -- all I remember is the tone and it was wonderful.
In the words of the man behind the beard "everyone's voice is unique -- their gear should be too." - Jamie Simpson.
DO
NOT WORK ON YOUR AMP YOURSELF UNLESS YOU KNOW WHAT YOU ARE DOING. THE
CAPS CAN HOLD A CHARGE THAT CAN AND WILL KILL YOU IF YOU DO NOT
DISCHARGE THEM PROPERLY! SPEND THE MONEY TO USE A PRO!
Total mod investment:
In the words of the man behind the beard "everyone's voice is unique -- their gear should be too." - Jamie Simpson.
Total mod investment:
Death switch removal - $75 (not dying... priceless)
Master volume Knob - $75
All that other stuff - $ 175
Total: $325
Total: $325
Contact Booya Amplifier Services -HERE-
Step Four: Retubing.
Tubes are to an amp as pickups are to a guitar, but unlike pickups they need to be replaced as they age. Some
guys will tell you that you do not need to change the tubes unless one
pops. These are the same guys that only change their strings when they
break. A tube's lifespan for maximum tone is about (500) hours or (2)
years. They may still work -- but they will sound flat and your amp will
not perform the way it was intended to. This is why you will hear some
guys say that their amp just does not sound right or sound like it used to. Personally, I change my tubes every 18-24 months on my rehearsal and venue gear and before every studio session on my studio gear. I may be nuts, but my amps always sound amazing.
There are a few things I take into consideration when buying tubes for a vintage amp. The first is -- what did the amp come with originally and what is available now for this application. This amp was built at a time when the manufacturing process was different making some tubes more noisy than others resulting in the original manufacturer selecting a less powerful preamp tube than we would use today in the same amp. You also need to consider that this amp was built for a bass guitar so the tubes needed to be quiet with little tube saturation allowing for as much headroom as possible.
There are a few things I take into consideration when buying tubes for a vintage amp. The first is -- what did the amp come with originally and what is available now for this application. This amp was built at a time when the manufacturing process was different making some tubes more noisy than others resulting in the original manufacturer selecting a less powerful preamp tube than we would use today in the same amp. You also need to consider that this amp was built for a bass guitar so the tubes needed to be quiet with little tube saturation allowing for as much headroom as possible.
Stock she came with (2) 6L6GC (3) 7025 & (1) 12AT7. I wanted her to breakup with tube saturation quicker than she was with
this tube configuration, so I replaced the 7025's with 12ax7's. The 12ax7's are rated the same as the 7025's, but they break up earlier-- meaning she now starts
to break up on 4 apposed to 7 on the volume knob -- giving me my desired tone at a responsible stage volume.
Besides the type of tubes your amp needs, there are a few different manufactures that offer slight variances of the same tube making them sound slightly different -- kind of like guitar strings. Some people swear by one brand and write off the next, but it is all on personal preference. To me, consistency is the key element and you should always get a matching set of power tubes. My preference has been JJ's for my gigging gear since they are cheap and I use new old stock for my studio rig. For this rebuild Mojotone sent me Tube Amp Doctor (TAD) tubes, and so far I really like them. They are a few bucks more than the JJ's but far less than the new old stock and sound almost as warm. If they hold up (and I'm sure they will) I will have a new favorite gigging tube brand.
Total retubing investment:
Get Tubes from Mojotone -HERE-
Total retubing investment:
Tube Amp Doctor (TAD) 6L6GC-SVT vacuum tube matching pair - $141.92
TAD 12AT7 / ECC81 RT002 vacuum tube (1) $15.45
TAD 12AX7A-C vacuum tube (3) -$51.00
Total: $207.46 + tax and shipping
Total: $207.46 + tax and shipping
Get Tubes from Mojotone -HERE-
Step Five: New Transformers.
Changing your transformers is one of the quickest and easiest ways to round out and improve your tone. Most people get confused about what changing out the output transformer, power transformer, and/or a choke really does to the amp. Basically it makes the amp more efficient and less susceptible to power outlet inconsistencies while improving the dynamic response and tonal balance of the amp. On less expensive amps the factory transformers are typically unbalanced crap giving you too much bottom end soaking up your lead tone or boosting the high end frequency making your rhythm tone thin and undesirable -- forcing you to used effect pedals to compensate for your unbalanced tone.
With vintage amps such as this one -- you can get power surges, hum and/or other electrical problems causing your amp to be inconsistent from the years of use. Some guys will just deal with a faulty amp until the stock transformers completely goes do to one of qualities of a vintage amp, it's "mojo". This refers to the many years of use and what is know as a "broken in amp". Now I'm not going to dispute this at all, yes my stock transformers had some "mojo" to them and I heard a difference right away between my upgrades and the stock setup. What I thought I heard was a slight boost in her high end with less bottom and a mid scoop. After a few hours of dialing in my new tone I realized that the new transformers did not remove any of the old frequencies my amp had, but unlocked the ones she had lost many years ago. In addition to the initial tone -- just like speakers, transformers have a break in period and will slightly take on new color/tone over time, so you may need to make a few adjustments to your amp settings the first few times you use your newly modded amp. After twenty hours of use I can honestly say that her voice has warmed up and she sounds fuller -- she is also more consistent then she was before this upgrade insuring that I will not have to use my backup amp due to 60 cycle hum at a gig -- if she has hum the venue has problems, and any amp will pick it up.
So to sum up -- what transformers really do is makes all of the amps components work and sound the way that they were intended too by delivering a constant amount of voltage/current with balance -- making your amp come alive.
With vintage amps such as this one -- you can get power surges, hum and/or other electrical problems causing your amp to be inconsistent from the years of use. Some guys will just deal with a faulty amp until the stock transformers completely goes do to one of qualities of a vintage amp, it's "mojo". This refers to the many years of use and what is know as a "broken in amp". Now I'm not going to dispute this at all, yes my stock transformers had some "mojo" to them and I heard a difference right away between my upgrades and the stock setup. What I thought I heard was a slight boost in her high end with less bottom and a mid scoop. After a few hours of dialing in my new tone I realized that the new transformers did not remove any of the old frequencies my amp had, but unlocked the ones she had lost many years ago. In addition to the initial tone -- just like speakers, transformers have a break in period and will slightly take on new color/tone over time, so you may need to make a few adjustments to your amp settings the first few times you use your newly modded amp. After twenty hours of use I can honestly say that her voice has warmed up and she sounds fuller -- she is also more consistent then she was before this upgrade insuring that I will not have to use my backup amp due to 60 cycle hum at a gig -- if she has hum the venue has problems, and any amp will pick it up.
So to sum up -- what transformers really do is makes all of the amps components work and sound the way that they were intended too by delivering a constant amount of voltage/current with balance -- making your amp come alive.
For this rebuild Mercury Magnetics sent me an output transformer, power transformer, and choke with the ability of running at 4/8/16 ohms -- giving this old girl a new voice and some much needed versatility.
Total Transformer investment:
Output transformer - $185
Power transformer - $ 160
Choke - $45
Total: $390 + tax and shipping
Installation by Booya Amplifier Services - $375
Total with installation $765 + tax and shipping
Get Transformers from Mercury Magnetics -HERE-
Total: $390 + tax and shipping
Installation by Booya Amplifier Services - $375
Total with installation $765 + tax and shipping
Get Transformers from Mercury Magnetics -HERE-
Now that I had this amazing, better than new vintage amplifier -- I needed to pair her with a set of speakers that I thought would bring out her best characteristics for my tone. There is no right or wrong speaker selection when dealing with a reputable manufacturer -- it really is all preference. The manufacturers I like using are Jensen, Celestion and Eminence. For this rebuild I wanted to have the versatility of having two different cabs voice completely different, so I decided to go with a few different options from both Celestion and Eminence.
I wanted to one cab setup with that true vintage American silverface sound but with a fatter bottom end, and a second cab to capture an early 1960's British sound. The cabs I had for this build were the matching Fender silverface 2x12 and (4) Vox AC15 open backs. I wanted the original 2x12 to have that vintage American Fender sound with a fatter bottom end so she got (1) Eminence Cannabis Rex and (1) Eminence Swamp Thang. The following is what went into each AC15 open back cab. (1) Eminence Cannabis Rex (1) Eminence Private Jack (1) Celestion Vintage 30 and (1) of the brand new Celestion Creamback 75's. The tonal combination I was able achieve with these (4) speakers was just amazing and seemed endless. After a few hours with each cab my personal preference for a 1960's British sound was the Celestion Creamback 75 when paired with the Vintage 30 or the Vintage 30 as a 1x12 and the vintage American sound for a 1x12 was the Eminence Cannabis Rex. To my surprise the Eminence Private Jack had this in between tone that was great for a thick creamy distorted sound. It was like a Greenback and a Swamp Thang did the nasty and than 9 months later out came the Private Jack. But speaker selection is just your personal taste and you should experiment with different speaker combinations from different manufacturers until you find a sound is best for your tone.
Total Speaker investment:
Eminence Cannabis Rex - $95
Eminence Swamp Thang - $ 89
Eminence Private Jack - $95 Celestion Vintage 30 - $145
Celestion Creamback 75 - $170
Get Speakers from Eminence -HERE-
Get Speakers from Celestion -HERE-
Step Seven: Walk away from your computer -- pick up a guitar, plug it into your better than new vintage amp and play the crap out of it.
Follow Local Music Gear on facebook for story updates and the sound files from this rebuild -HERE-
Posted 10/2013
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