Best Fender Bassman Preamp Circuit?

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Best Fender Bassman Preamp Circuit?

Postby dcgillespie » Sun Mar 08, 2009 8:52 pm

I have always been fond of the sound that the early blackface piggyback Bassman amps produced with a bass guitar playing through the bass channel -- live, or in the recording studio. Is there any consensus as to which version of Fender's bass channel preamp design for the Bassman best delivered this sound? I'm thinking this would be somewhere between the AA864 and AB165 designs. Any thoughts would be appreciated.

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Postby cw » Wed Dec 23, 2009 5:32 pm

that is pretty subjective depending on what you want to sound like or "tone" the holy grail sound.

i have not been posting here for awhile but i adhere to the don hubert theory of simplicity in practice. since i have last posted here, i have been playing a bassman 10 a 50 watt amp that is about as simple as amps get.

the 864 circuit is a nice circuit but i see more guitar players using it as bass players....via Brian May has had a lot of influence there.

my venues are small so i can get by with 50 watts and clean power in a small dose. for a larger venue i would mike it or rent power. if i needed big power more often then i would lean towards a DH Hammertone biggen or maybe a 300Pro Fender, Ampeg SVT. 200 watts or greater tube.
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Postby Geek » Wed Dec 23, 2009 8:48 pm

There's five items in a system that greatly affect the bass tone:

The guitar itself has three - body, strings and pups.

Then there's the amp and the speaker.

If we are talking "Chuck Berry" early, 4/5 times the bass was DI's to the mixer and the tone was all in the guitar and player.

Cheers!
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Postby dhuebert » Thu Dec 24, 2009 8:24 am

Thanks for the kind words there, CW!

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Postby wyatt » Mon Jan 04, 2010 2:26 am

Honestly, I've never seen a Bassman used as a bass amp. The Portaflex came out around 1960 or so, it's the first true modern bass amp design, and all those hybrid guitar/bass amp things went out of fashion for bass real fast.

I don't know when Leo decided the Bassman was really a guitar amp, may as far back as the Tweed days, but the first Bassman heads, the Blondes were built and toned for a guitarist, Dick Dale (a Blonde 6G6-B Bassman head bought by McCartney in 1965 was the most record guitar amp for the Beatles). I don't think Fender ever looked back. Blackface Bassman heads are famous for their aggressive overdrive and crunch, they retained more of the preamp hierarchy of the Tweed Fenders (and Marshalls) than the BF reverb combos.

But, as a result, I can't answer your question. I got a feeling the AB165 will have a little more headroom. Leo kept making his amps louder and cleaner as he went along. Still, I can't see a 45-watt head being enough for live band gigs for bass. I agree with the 200 watts or so, mentioned above, for live bass.
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Postby cw » Mon Jan 04, 2010 10:29 am

ok, i still believe the Fender bassman circuits are the best sounding (with notable exceptions). the 300Pro (actually a bit closer to a Dynaco mk34 preamp circuit) but still a viable choice. Fender just changed the name plate on the Sunn 300T and is marketing it (they bought the Sunn company) but the power is just what a guy needs with today's guitards going for power. the bass signals require a lot of power vs guitards signals or you get lost trying to keep up with them not to mention a hard hitting miked drummer can bury you also. you will need about 3 times the power of a guitard to stay with him (or her) due to low frequency/power need.

"I don't know when Leo decided the Bassman was really a guitar amp...Wyatt" ... they really didn't have "bass" toned speakers then much less tuned cabs and i think guitards really were the ones liking the early bassman tweed series then it caught on! prolly the same reason that latter bass players started liking the Showman's/Twins for bass. it worked with the higher power in sealed cabs. tweeds/tweed preamps/tweed amps in general suck for playing bass!

for classic rock, country just about anything at small/medium venues and providing your guitard isn't driving a lot of watts (30 or less) you can get by with 50 hard driving watts (miked sometimes) or 100 watts. i use an insanely old dual cell Fender Bassman speaker cab with two 12" G12t-75 Celestions in it, a Bassman 10-50 watts and am happy with the old 60's sounds i get but my Epiphone EBO bass is highly modified with a 60's Gibson "Mudbucker", Grover tuners and a Gibson Thunderbird tail piece to help with string harmonics transfering to the body all soon to be transfered to an all Mahogany bodied custom Les Paul Junior (think 59 Gibson EBO) build. (pardon my straight vs Gibson curved) Fender finger rest. it's simply more economical to chop a cheap Epi than it is to start off making changes on a vintage Gibby or having a custom build without any idea of what a player wants in tone.

as is:

Image

those are just my qualifications and i do play bass and this is just my opinion FWIW. however:

i am wanting a bigger amp for larger gigs because miking is not the same as stage presence. the present considerations are:

1) Don's BFA as in other blogs here at DIYTube http://www.diytube.com/phpBB2/viewtopic.php?t=2868
http://www.diytube.com/phpBB2/viewtopic.php?t=1436
2) Dan Torres 200 Bass power amp which is a kit and would need a separate preamp or one added
3) A Fender AB763 (Twin, Showman) tone circuit (essentially a bassman circuit on the normal side) on a 160-200 watt power circuit with an old NOS Fender OPT which i recently got and am planning on running with 4 or 6 tubes for more headroom so i can keep the tone clean (read POWER) for reasons mentioned above and the fact that i really like making double bass tones electrically (why i play flat wounds on that old Mudbucker and send Fender Precisions running back to momma and ask if they can come back as a banjo!!!...i do plan on making a Sadowsky Killer based on a Precision though!

think about what kind of music you play, if you want a clean sound or a guitar through a bassman circuit for an overdriven sound (vs finger technique tonal changes). if you are going to be miked or not.

i would lean towards the 864 or a Bassman 10 preamp circuit. no disrespect to Don but i like the "Fender" amp sound and a lot of it has to do with the preamp circuit.

speakers are a totally different subject!!!
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Best Fender Bass Amp

Postby Bassmasta69 » Tue Feb 16, 2010 6:42 pm

This is a no brainer. Get a BF Showman. That circuit is the basis for some of the absolute BEST bass amps, the Alembic, the Kern 777 and the Demeter amps are all basically showman preamps. The Showman is plenty load enough when paired with a good cab. I play with two guys blasting through double showman amps and I keep up just fine. Before you go modifying your gear try one these out.
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Bassman pre-amp

Postby RobbieNuke » Thu Mar 25, 2010 9:05 am

The Bass channel has a LF cut in them. The tone stack circuit design is unique to Bassman, Bantam Bass, Super Bassman, Bassman 10, Bassman 70, Bassman 100, and Bassman 135. I theorize this was done as a sort of speaker protection for when the bass player started cranking up the volume there would be less LF to the speaker (and therefore less chance of speaker damage). Remember, the standard Jensen speakers issued in the 60's could only take about 35-45 WRMS each. Playing the Bassman loud to keep up with loud drummers saturated the signal with potenially dangerous levels of harmonics as the amp is now putting out closer to 80-90 Watts, but with clipped signals. Not really bad for guitar tone, but desired bass tones in the early 60's were more conservative and clean. However the circuit design couldn't give the "DEEP" tone promised on the faceplate, so a lot of regular gigging bass players loyal to the Fender brand just used Showman amps.

The Normal channel has a much richer/fuller sound. This tone stack circuit design is basically the same as in all other Fender guitar amps (Normal and Vibrato channels). My Bantam Bass Normal channel outperforms the Bass Instrument channel in all aspects (i.e. tone flexibility, tonal range, even volume)... as far as bass guitar tone is concerned.

NOTE: Rickenbacker 4000 series bass guitars had an in-line HP capacitor that achieved essentially the same thing no matter what amp you used. Some Gibson basses mess with circuit designs that acomplish this effect also. Nobody (i.e. bass mfgs) does this anymore since the 70's when high powered bass speakers became readily available.

I do not use any Fender Bassman amp for getting Fender tone at live gigs. However, I frequently use a Studio Bass (head; chopped from the Studio Bass combo). Typical Fender tone stack (Treb/Mid/Bass) as well as a 6-band EQ (the Presence control is actually part of the EQ circuit, not a power amp feedback control). Six 6L6 tubes has tons of headroom and stays clean all the time (the same tone as a Bassman amp Normal channel offers at volumes 2-5).
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