Fender Bassman 100, dating and stuff.

[sibo]

I recently picked up a Fender Bassman 100 and started googling for it. I found out that it probably (I'm not 100% sure) is a silverface model, please correct me if I'm wrong.

As the topic states I'd very much like to find out what year is was made and if possible what kind of schematic it may have. From what I've seen from just lurking around a lot of those bassman posts there seems to be a lot of modifications possible to these oldies.

Sound-wise its absolutely never distorting by itself. I play it through a pretty new Laney 4x10 8ohm cab. I can push it hard and for long, so far no problems and the sound is crystal clear. That's a pretty good feature for an amplifier I guess but I really like it when the sound is cracking up a little bit like this other old Fender combo I tried. Sounds as if its really getting pushed although is doesn't overdrive (I think), I'd say it's the sweet spot! Anyone got suggestions on how to reach that cracking up part?

I mainly use a Gibson SG with 59 Classics and a BYOC mouse, kind of like a rat distortion pedal.

So many questions! I guess this will have to be the beginning of the discussion.

Some pictures of it will follow!
All pictures can be found here:
Fender Bassman 100 - Imgur

[Jazz P Bass]

Bassman 100T Schematic

1972-1977.
Fender Bassman - Wikipedia, the free encyclopedia
The best thing that you could do for more grit is to stick a pedal in front of it.

[Chuck H]

Yes, it's a SF amp. It's not that collectible. It's a good, loud amp. If it's not distorting with the knobs cranked and the guitar volume up there is something wrong with it or your guitar. It should distort at least a little.

[Tom Phillips]

The Bassman 100 is much like a Showman model without the tremolo feature.

If you want to narrow down the year that your exact amp was made you can look for date codes on the pots and on the transformers. Google to learn how to interpret the codes or post them here and we will help.

There is one date code article at http://ampwares.com/faq/how-old-is-m...age-amplifier/

[sibo]

Thanks for answers guys!

1972-1977.
Fender Bassman - Wikipedia, the free encyclopedia
The best thing that you could do for more grit is to stick a pedal in front of it.

I tried some different pedals but can't really say that I got close to being satisfied. There is some element missing, wish I could be more precise but it doesn't feel vintage at all somehow. Makes any sense at all? I am looking for a rich full lead tone with some more presence and still not the take-over-metal-sound many people use. I'll try to find a reference.

Yes, it's a SF amp. It's not that collectible. It's a good, loud amp. If it's not distorting with the knobs cranked and the guitar volume up there is something wrong with it or your guitar. It should distort at least a little.

Well it distorted maybe a tiny tiny bit when volume pots were at 10 but it's so damn loud so that's no way to play. Not if I wanna hear drums anyway There has got to be a way to figure out what makes that sweet spot distortion and push it so it comes earlier in volume.

The Bassman 100 is much like a Showman model without the tremolo feature.

If you want to narrow down the year that your exact amp was made you can look for date codes on the pots and on the transformers. Google to learn how to interpret the codes or post them here and we will help.

There is one date code article at http://ampwares.com/faq/how-old-is-m...age-amplifier/

Thanks man. I might do this is I decide to modify the amp, opened the back board and figured I have to take it apart some more to find those components which I don't have time for right now. Is there any way to know what version of the schematic my amp is, without taking it apart? Can I figure it out from the tube chart for example?
The reason I want to know is I found some guide on "blackfacing" your silverface which is supposed to make the sound better somehow, not sure if I trust it but might be worth digging into if it's not too hard.

Also I read some phase inversion posts. Googled it, it didn't make much sense to me. In simple words - what is it and why do I need it?

[Jazz P Bass]

The schematic that I posted should be your amp.
The output load should be 4ohms, as stated on the schematic.
This amp puts out 100 watts, full tilt boogie.
You have not stated where you have the tone controls set.
The tone controls have a lot to do with the preamp amplitude.
Nor the master volume.
Cranking everything up & then slowly turning up the master will get it to break up somewhat.
Personally, I think you have the wrong amp.
It's too loud.
Blackfacing will not get what you want, either.

[Chuck H]

I agree. A different amp might be a better fit.

Sibo, that amp can be modified into a different circuit that will grind out moderate distortion at any volume. But that's only if want to work on the amp instead of play through it. Modding that amp EFFICIENTLY would best be done by someone with more knowledge of tone construction and circuits. Even if you follow a known mod instructions carefully the likelihood of some small mistake exists. And without experience it can take a very long time to find errors like that. We've seen it here many times. Further, there is no telling if a particular mod will give you what you want until you hear it. Some "dude" saying it's awesome is not a solid endorsement. You may have to change the circuit several times to dial it in. Again, this is best done by someone that knows what to change to achieve specific goals. We've "step by step'd novices here before. As often as not the thread eventually just peters out and we never hear from the OP again. Now, that said, if you DO want to learn circuits and amp modding you're in the exact right place. But it's a long term commitment. Not a quick solution to your tone dilemma.

If you just want to play your guitar and enjoy the tone, my advice is to get another amp that you already like. As in, don't spend your money until you try it and like it. Consider how much power you will need and at what volume you will need to get your preferred tone. Be certain the amp has the features you will use (example: if you NEED both bedroom practice AND band practice volume levels you may want to consider a master volume amp that makes good distortion with the preamp) (another example: even if you love the sound of some little 5W Fender when cranked up, but you play with a band, or intend to, it's still the wrong amp because it will never be loud enough)

The amp you have now is a nice example of a good amp. You can probably get enough dough for it to cover much of the expense of a different amp. Should you decide to go that way.

So the question is, do you want to learn circuits or do you just want a different tone?

[Tom Phillips]

+1 on the input from Jazz P Bass & Chuck H.
I'll add that the Bassman amps that you find so much discussion about blackfacing and how great they can be for guitar are the earlier versions. Those were 50 Watt amps which is still pretty loud but the circuits in those models was (or could be more easily modded to) the ones that give the sweet guitar sound you said you want. As you found in the Wikipedia link listed in post #2, Fender made many models of amps using the name Bassman. The Bassman 100 was meant to be loud and clean. The implementation of the master volume in that model does not work well to produce overdriven type guitar sounds because the preamp is low gain and not tailored for an overdrive sound. If you keep up the search you may still find a pedal that gives you the sound you like.

[sibo]

Thanks for all the replies, really appreciate it!

I don't want to take the shortcut here, I want to understand what it is I like in my own sound. Of course within reasonable limits (both funds and time, as I recently had my first kid).
The ideal setup for my amp would be to install different channels in it and perhaps even a boost-function to work with a foot switch. I've seen this before and I found it on my closest professional amp modifier (http://www.tommy-folkesson.nu/) but it was too costly. This, however, I guess is not gonna happen anytime soon - if at all. Gotta start with the "easy" stuff.

So! It seems you guys know your way around modifying amps, please point me in what direction to start and I'll read my way through as much as I can do myself. What mod/mods would you suggest me trying out?

I am working as electrician by the way so I do have some basic knowledge in how to wield that soldering iron and can read most circuit schematics without bigger problems.

On a side note, until this project is carefully planned to the point where I actually heat up the soldering iron and start modifying - any good ideas for pedals to try with my gear?
So far I've used Big muff PI (US version), Proco rat (the BYOC version, same thing), Behringer VT999, Bass Big muff and some crappy no-name pedals. They all sound fine, except for the Big muffs which to my ears don't work well with this amp - however it's not quite there yet. Tried it with mxr compressor and really didn't like how "perfect" and controlled it sounded.

Oh and by the way, if you're about to ask if I tried other guitars & cables - I did. Didn't try another cabinet yet though. Plan on changing the elements in my current one later on for 4 ohm ones. Unless there is a way changing the amplifier to be better suited for 8 ohm cabs that is?

[Jazz P Bass]

Multi speaker cabinets can be rewired, if you are trying to get to 4 ohms.

[Chuck H]

I don't know what Laney loads in their cabinets. I like 4x10's. But it's not a classic rock or hard rock sound. I don't know what sound your looking for. So all I can offer is that speakers make a mondo difference. If "I" were trying to get a Bassman 100 into a clearly guitar tonality I might choose a pair of 8 ohm Celestion 12's in a closed back cabinet. V30's or G12H30's depending on your tastes. I use one of each in my 2X12.

[Steve Conner]

Try a clean boost pedal. You should be able to overdrive the first few stages of the amp with it and then use the master volume to control the overall loudness.

I use an SPF Ego Booster, but only because I got it in a trade. There must be several others.

[Chuck H]

+1
Clean boost pedals are a whole different thing from distortion boxes. I use to use a BOSS GE-7 EQ with the mids bumped up and the top and bottom rolled off a little. I plugged that into a plexi that I installed a master volume on (first mod I ever did!). Great tone!

[sibo]

Again thanks for input <3

I will try it when I can borrow a boost pedal from a friend or if I by chance would find my crappy boss multi pedal and use that for the boost function.
However that seems like a quick fix that really doesn't solve my "problem". I don't mind pedals at all, but the less of them the happier I am.

Call me stupid but I'll ask rather than not know.
When you overdrive an amp by pushing the volume up, you do it in the pre amp - right? I mean that's gotta be the point of having a master volume, or at least a master volume mod.
Just theoretically and this is before I really started reading up on these kind of mods - but - shouldn't it be pretty easy to push the pre amp volume up by just changing the potentiometer on the volume knob to decrease the resistance through it? Or is a functioning potentiometer always starting at 0% and ending at 100% resistance?

Please share good working reliable tutorials or forum posts on this kind of mod (and/or others) if you got 'em

[Tom Phillips]

...When you overdrive an amp by pushing the volume up, you do it in the pre amp - right? I mean that's gotta be the point of having a master volume, or at least a master volume mod...

Mostly right but it does depend on the overall design of the amp. Most modern high gain amps do distort first in the preamp stage but some designs are setup to distort the power amp stage before the preamp starts to distort.

... shouldn't it be pretty easy to push the pre amp volume up by just changing the potentiometer on the volume knob to decrease the resistance through it? Or is a functioning potentiometer always starting at 0% and ending at 100% resistance?...

No. The gain is produced in the tube stage not the volume control potentiometer. The volume pot is there to throttle the full gain to a lower value when you turn it down. Think of it like the accelerator pedal in your car. The engine produces the power to make the car go. Not the pedal. The pedal is just how you control the engine. The volume control in a guitar amp is actually a variable attenuator. It does not "produce" any gain.

Also, good preamp distortion sounds are usually produced by adding extra gain stages that have attenuation and frequency response shaping circuitry between those gain stages.