hey all the bassman owners out there!

you'd be a big help if you posted which circuit is in your bassman (the letter/number combo on the tubechart, like AB165), which channel you're usually using for guitar, and if applicable, for bass, and what you do or don 't like about the sound: Im esp. interested in early v. late breakup, where the sweetspot is, treble repsonse and bass response.

All this to prepare some work on my bassman. So'd really appreciate any info.
(I decided Im going to get it to the specs I want after recovering from the shock and horror of goin' through my bassman last weekend with a multimeter. If you ever need a tech in the netherlands, drop me a mail and I 'll tell you which one NOT to go to. :twisted:)

WR

Rules to live by #314:
"When in Italy, if the menu says something's grilled, don't assume it is."

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My Bassman is a 1971 Sliverfaced growl-monster. It's the head - didn't come with a speaker cabinet. I keep waiting for one, but I don't want the big oversized cab that originally came with this amp. I've been down that road, already.

The chart erroneously claims the circuit to be an AB165 (they kept using the same tube charts even after the circuits changed).....BUT, it's really an AA371 which is not a lot different.

Unfortunately one major difference is in the bias section. Instead of a true bias adjusting trim-pot, it has a trim-pot wired to 'balance' the bias between two (presumably unmatched) tubes.

This was a little trick that CBS came up with so they wouldn't have to bother installing (or paying attention to..) matched tube sets.

Of course this means that to actually SET the bias (rather than merely rocking it back and forth between the power tubes), one has to laboriously go in, and swap out resistors with a soldering iron, until a good bias is found for the tubes being installed.

Fender also called the bias balance trim-pot a 'hum-balance'. The idea was to turn the pot slightly back or forward until the least amount of 'hum' was achieved.

I tried this, and it works. But so what? The amount of hum is negligible.
Besides, these days, everyone (oretty much) buys (or is sold) matched sets of power tubes.

So one popular mod to these amps is to either -

a. completely replace (or convert) the hum-balance system with a true 'level' adjusting bias control.

or

b. add a true 'level' adjusting bias control alongside the hum-balance system.

Both are easy to do if you have the right parts, skills and tools.
Most 'techs' recommend option b. so you can have the bst of both worlds.

That's what I did.

Now, getting back to my amp. I bought it used in 1981 for $75.00 and it had all new 'Fender' branded tubes installed the day I bought it.

I was told it had issues, and the store that sold it to me changed a cap or something.....It's been too long now...I fergit.

Anyway, the NORMAL channel totally kills! It has more gain than my BF Showman (of course it doesn't have half the tone of the Showman).
The BASS channel sucks. It's completely useless. No tone, no gain, no nuthin.

I use the amp when I need a screamin' crunch machine (rare) and as a backup, or re-inforcement at outdoor gigs. It's an old beast, but I love it.

Recently installed new filter-caps (SPRAGUE ATOMS) and I'm soon going to install new electrolytics in the signal path.

WR as I was telling Jake a few days ago I play fulltime through the bass instrument input 1 and I play lead guitar it's freakin sweet with not much break up but perfect, I have it turned up to 4 on the volume and treble @ 7 and bass @ 5 the deep switch is off but man @ volume 4 it's as loud as a twin rever or showman, If your going to upgrade anything think about changin the circuit to AA864 it's the best circuit for Bassman's it blows AA165, AB165 out of the water, AB165 sucks no offense to those AB165 owners out there but man AA864 has better voicing for guitar and bass 10 times over.

And here's proof of that killer tone I'm talking about pure AA864 tone
filmed @ KCR with Clint Beachwood last October of 06'
Safari Sam's Hollywood, Ca show with The Ghastly Ones October of 06'
HBISM Verbtones with Slacktone October of 06'
http://www.youtube.com/watch?v=qYP6iB5rXEU
http://www.youtube.com/watch?v=0QI0LynT724
http://www.youtube.com/watch?v=QmZ8Slx4zTg

AB165 was CBS's stupid change and the Bassman in 65' was the the first victim of the circuit change, that's why AB165 sucks it's not the greatest cicruit for guitar ask any other amp tech out there, besides the blonde era circuit that rocks but we are talking about a blackface circuit.

My Basman is a stock AA864 from 1964 no mods all stock and I play through a 2x12 cab, I rarely use the normal channel.

WR if you need help I repair and build Fender blackface rigs even tweed chassis

Ralf of The Kilaueas! played through my Bassman while they were down with us and told me it's the best blackface amp he's played on the west coast tour and the man back home plays a 63' blonde showman, and he coudln't get enough that he would plug in @ my place and just jam on it

-Kyle

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Last edited: Mar 14, 2007 11:23:49

My bassman uses the AA165 configuration with 2 6L6GCs. I don't play bass through it very often but I do play any one of a number of Jazzmasters through it with great results. Because it has such a good bass circuit, when I run my reverb tank with it the sound is fantastic.

Ron (ToneBoy)
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