Fender bassman amp question

thumper · Post by **thumper** » Thu Jun 28, 2007 1:56 pm

possibly trading for a late 70 model silver face fender bassman fifty amp. any user info? looking forward to hearing it with my 4003 and 4-10 (4 ohm)ampeg cabinet.

jps · Post by **jps** » Thu Jun 28, 2007 4:15 pm

Find out which circuit it is, you may want to have the amp rewired to BF specs so it will sound better.

thumper · Post by **thumper** » Thu Jun 28, 2007 4:42 pm

bf specs ? all i know it's all tube. i haven't used one since the late 70's

jps · Post by **jps** » Thu Jun 28, 2007 5:09 pm

Blackface as in AB763 circuit. Starting in the late '60s, CBS messed up the circuit design which caused something called parasitic oscillations that made the amps sound nasty.

wayang · Post by **wayang** » Fri Jun 29, 2007 4:19 am

You don't want parasites in your low end, that's for sure...

thumper · Post by **thumper** » Fri Jun 29, 2007 6:31 am

is this amp designed to handle a 4 ohm speaker system?

squirebass · Post by **squirebass** » Fri Jun 29, 2007 8:28 am

CBS did all they could to mess up these amps, as well as the Bassman 135, which is one amp that I own. But as long as you are not running them full out, I haven't had much problem with parasites or anything else with them. They are great as long as you don't dime them, and they produce a nice sparkly clean tone for guitar if you need that... And I've never had any problem running it to my Ampeg 4x10, although I have an Ampeg SVT III Pro that I use more often. You don't want to use them for distorted guitar either, unless you have a stompbox that you can use for the drive. I also use my Bassman to amplify my keyboards and it works nicely for that too...

elgranluis · Post by **elgranluis** » Fri Jun 29, 2007 9:12 pm

I've owned every bassman except for the ones you are asking about! I do currently own a bassman 100 with matching 4x12. It sounds great, except there's a weird little noise I haven't been able to track down/fix. I also found there's little difference between tweed, blonde, blackface, and silverface, speaking about bass. On the guitar there are some clear differences, but not on bass. Any tube bassman is damn great imho!

thumper · Post by **thumper** » Sat Jun 30, 2007 3:37 am

from what i can tell, this is a 73 model. i tried it out yesterday afternoon for a short time and was impressed. great tone with the ric. i'm playing tonight and will put the stress test to it.

doctorwho · Post by **doctorwho** » Sat Jun 30, 2007 8:33 am

According to The Fender Amp Field Guide, the Bassman never had an AB763 circuit:

http://www.ampwares.com/ffg/bassman_bf.html
(Blackface: AA864, AA165, AB165)

http://www.ampwares.com/ffg/bassman_sf.html
(Silverface: AB165, AA568, AA270, AA371)

It looks like AB165 would be the 'blackface equivalent' to the guitar amps' AB763. I recall reading somewhere about the difference among those circuits, but I don't remember where.

Of course, if the amp sounds good to you, that's what really counts.

jps · Post by **jps** » Sat Jun 30, 2007 1:11 pm

My Weber and Pittman books are packed away but I am pretty certain that there is an AB763 Bassman circuit as the earliest you mention is AA864 which dates from 1964; sointenly the Bassman goes further back than that date!

jps · Post by **jps** » Sat Jun 30, 2007 1:22 pm

I found a good resource for schematics. I think I was going by the power amp circuitry, so the AB763 would not, strictly speaking, be correct for the Bassman as it contains vibrato circuits that the Bassman does not contain.

www.schematicheaven.com/fender.htm

The power amp of that circuit does not have the caps from the 6L6 grids to ground unlike the AC568 circuit of the later SF Bassmans, one of the things CBS did to "improve" the amp!

jps · Post by **jps** » Sat Jun 30, 2007 2:05 pm

Now I got the timeline figured out for the early '60s Bassman. Throughout the white tolex era it goes through the different 6G6 iterations before being redesigned and given the AA864 designation.

So I do stand corected by you Gary!

pflash4001 · Post by **pflash4001** » Sun Jul 01, 2007 1:55 pm

So does anyone know the story behind this cab design? My brother just picked up one of these cabs at a local pawn shop. This photo is from a listing on ebay. I don't think I've ever seen 12's used for bass cabs, but I have never seen this type of cab before, either. Anyone have any info?

jps · Post by **jps** » Sun Jul 01, 2007 2:32 pm

That is/was the famous Bassman 4-12 cabinet that Fender made in the early '70s.

Here is one on the 'bay right now.