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Bassman Silverface/Blackface

jonmhenderson
October 6th, 2008, 05:22 PM
Can someone give me the skinny on the two eras and the differences in tone/ circuitry?

Bluesbob
October 7th, 2008, 01:14 AM
Blackface Bassman came in two circuits, the AA864 and the AB165. The former is considered to be the last real Bassman circuit, although it could be argued that the 6G6 (or 6G6A) actually was the last traditional Bassman. The AB165 is notable because of the equal number of gain stages, which enable the two channels to be linked ("jumped"), resulting in added gain and a different, and to some ears better, tone.
The AB165 circuit continued into the Silverface amps. This circuit also includes a "hum balance" pot instead of a bias adjustment, but it is extremely easy to change back to bias adjust.
The Silverface Bassman circuit changed to AA568, AA270 and AA371, according to the Fender Field Guide (http://www.thevintagesound.com/ffg/), but the two most popular circuits for BF and SF are the AA864 and AB165. Neither of them are (IMHO) very good for bass, but sound great for guitar.

The AB165 chassis is often used as the basis for a "Bassman combo" such as this 2X10. Notice the jumpered channels. It has one Jensen RI C10Q and one Celestion G-10 Vintage.
http://i53.photobucket.com/albums/g41/Bluesbob/2X10Bassmancombo3.jpg
This is a really nice sounding amp, with plenty of mids and a loud clean sound up until about 4 on the volume control and then a gradual onset of tube (and speaker) breakup, similar to many Fender amps. Hope this helps.

Wally
October 7th, 2008, 12:02 PM
What is a 'traditional' Bassman. IF that indicates the 5F6A tweed, the 6G6 Bassman amps might be more closely related to the BF amps than to the Tweed. The 6G6 amps have a much different preamp topography compared to the 5F6A....ONce again, the 6G6 more closely resembles the BF amps concerning gain stage relative to tone stack placement in the circuity.
Imho, BluesBob's little bassman combo there is one hot little amp the way he is using it. that linking allows for rich, complex tonality for hot country, blues and when pushed with a humbucker hot rock.

Bluesbob
October 8th, 2008, 10:55 AM
Hey thanks for the compliment.
Wally is absolutely correct about the tone -stack placement and other similarities. I tend to glaze over the details. But there is a sense of "tradition" in the pre-CBS circuits.

zero9
October 9th, 2008, 05:51 PM
You need to go back even further for the best Blackface circuit-the AB763. When people talk about blackfacing their amps this is the circuit that they are using. It's the original Blackface circuit and generally regarded as the best. It is actually possible to find Silverface amps that still used the AB763,
AA864 and the AB165 years later. If you are looking to buy one FAMILIARIZE YOURSELF WITH THE CIRCUITS. Fender used those circuit stickers in their amps until they were gone, regardless of what circuit was being built. I have a 68 Bandmaster that was all original and still had an AB763 circuit. Fenderholic and a few other sites have the circuit layouts and they are fairly easy to distinguish if you look closely enough. Start with the bias circuit as the previous poster mentioned. If they are the same check the main circuit board because that is where many of the "tweaks" were made. Just a note- it was with the AB165 circuit that musicians began to complain about the tone of the Silverface amps. It is very simple to turn these back into earlier circuits yourself and not too expensive to have it done by a pro. It'll be cheaper to find an AB165 or later and turn it into a 763 or 864. In the end it all depends on YOUR ears.

Wally
October 9th, 2008, 06:55 PM
You need to go back even further for the best Blackface circuit-the AB763. When people talk about blackfacing their amps this is the circuit that they are using. It's the original Blackface circuit and generally regarded as the best. It is actually possible to find Silverface amps that still used the AB763,
AA864 and the AB165 years later. If you are looking to buy one FAMILIARIZE YOURSELF WITH THE CIRCUITS. Fender used those circuit stickers in their amps until they were gone, regardless of what circuit was being built. I have a 68 Bandmaster that was all original and still had an AB763 circuit. Fenderholic and a few other sites have the circuit layouts and they are fairly easy to distinguish if you look closely enough. Start with the bias circuit as the previous poster mentioned. If they are the same check the main circuit board because that is where many of the "tweaks" were made. Just a note- it was with the AB165 circuit that musicians began to complain about the tone of the Silverface amps. It is very simple to turn these back into earlier circuits yourself and not too expensive to have it done by a pro. It'll be cheaper to find an AB165 or later and turn it into a 763 or 864. In the end it all depends on YOUR ears.



I would like to see a schematic of an AB763 Bassman. I have no source for that schematic. The first BF schematic for a Bassman that I have seen in any source is the AA864,...August of 1964. Other BF Fenders..DR,SR,TR, Bandmaster for example) were first drawn up in July of '63(AB763), but the BAssman lingered on using the 6G6B circuit through '63 and early '64, to the best of my knowledge and that of the resources that I have seen. Anything might be possible, though.
I would venture a guess that if a person had a documentable BF BAssman with a tube chart that read AB763 and it had a circuit different from the 6G6 or the AA864, one might have a very desirable one-off. ONe offs from FEnder are rare. I have a one-off '63 Pro, so I know that Fender did odd things and some of those examples escaped the factory somehow...but it is a rare thing.
I also understand that some folks hold the '65' circuits as bad things. REgarding the AB165 BAssman, after reverting to a true bias situation and yanking those two 220K resistors connected to the power tubes' plates, imho that amp is a rock monster....or hot country amp either. IT does some OD that no other BF/SF amp does. There is no reason to my ear to take one back to the AA864 circuit, which is the circuit that most point to as the best BF BAssman circuit. The AA864 is cleaner, but I like it hot; and those 3 gains of stage in each channel lead to a hot Norm ch and the ability to daisy chain the channels for thick power if you want it.

Ben Harmless
October 10th, 2008, 02:33 PM
This thread is making me salivate. I passed up a '65 Bassman in a 1x15 combo cab a couple of years ago, and I really shouldn't have. It was a sweet, sweet amp as is.

There really is something special about a Bassman. No other Fender amp sounds as sweet to my ear. Brighter, yes. Clearer, yes. Not as sweet.

Tim Swartz
October 10th, 2008, 03:20 PM
I would like to see a schematic of an AB763 Bassman. I have no source for that schematic.

Nor does anyone else.

Wally
October 10th, 2008, 03:35 PM
Nor does anyone else.

AS I thought. :twisted:

Hecks
October 10th, 2008, 03:38 PM
Would it be possible to take a 5F6-A circuit and modify the normal channel to 6G6-A normal channel specs? 5F6G6-A!

Wally
October 10th, 2008, 03:49 PM
Just build a 6G6 amp. The 5F6A is an icon in the amp world for a good reason. That said, I am sure that someone(?) somewhere(?) sometime(early '60's) has done something like that to a 5F6A. And....someone cried when they later bought and discovered a 5F6A butchered. Marshall dominated the rock world for a decade (or 5 and counting) just becasue Fender stopped building in 1960 what turned out to be just what rock guitarists wanted. Great country amp, too.

Bluesbob
October 11th, 2008, 09:05 AM
You gonna change to a SS diode rectifier? The 6G6-A was the first Bassman without tube rectification, marking a break in the traditional Fender Bassman line. You could say it all started to go wrong right then. (Well, maybe you couldn't say that, but I could.) :grin:
Stick to the 6G6. Or not - it's your amp.

Dezzy
September 1st, 2011, 07:52 PM
You gonna change to a SS diode rectifier? The 6G6-A was the first Bassman without tube rectification, marking a break in the traditional Fender Bassman line. You could say it all started to go wrong right then. (Well, maybe you couldn't say that, but I could.) :grin:
Stick to the 6G6. Or not - it's your amp.

U would be the only one to say it, all bassman kick ass, any amp that get's reissued kicks ass, that's why the demand is their for reissue, HRDX amps will not get reissued in 50 years me is thinking

jh45gun
September 2nd, 2011, 12:49 AM
I like SS rectification.

Justinvs
September 2nd, 2011, 01:35 AM
I played bass for several years through a borrowed SF Bassman head. I have no idea what the vintage of it was, but I loved the tone I got out of it. My only complaint is that it didn't have quite enough power to stay ahead of the drums or other instruments,

I never did get a chance to play a six-string through it. Wish I had.

Justin

backline
September 2nd, 2011, 04:57 AM
I thought this was the 100 post...... sorry

SamClemons
September 2nd, 2011, 05:22 AM
I am running a 68 Bassman AB165 stock through a 2-10 cabinet for both bass and guitar. I am real pleased. I usually run the normal channel for bass and guitar.

StoogeSurfer
September 2nd, 2011, 08:41 AM
This is a really nice sounding amp, with plenty of mids and a loud clean sound up until about 4 on the volume control and then a gradual onset of tube (and speaker) breakup, similar to many Fender amps. Hope this helps.

Is that cabinet off the shelf from somewhere? I have a '68 head myself, and I like that 2x10 idea ... what are the speakers?

milocj
September 2nd, 2011, 08:53 AM
Dezzy resurrected a three year old zombie thread to argue the merits of the Bassman models. Some of the new questions may not get answered.

SamClemons
September 2nd, 2011, 12:22 PM
I purchased a 68 drip edge PA cabinet that a guy had cut down to a 210 speaker cabinet, so it is an original 68 cabinet, but not like what was available back then.

For speakers, I have an Eden and a SWR bass speakers. They are heavy enough to stand any thing the bass throws at them, but sound good to me with guitar. If I were going strictly guitar, I would go with some lighter guitar speakers. Volume levels would also come into play with speaker selection. I think lighter speakers sound better...as long as you don't blow them all to pieces. here are some pictures.

You can buy an empty or loaded or vintage or other cabinet.

Dezzy
September 2nd, 2011, 03:13 PM
Dezzy resurrected a three year old zombie thread to argue the merits of the Bassman models. Some of the new questions may not get answered.

We talk amps in here man weather the thread is old or new, if I went and stuck today's date on the thread would that make U happy, on that note have a nice day

ASC67
September 2nd, 2011, 04:35 PM
We talk amps in here man weather the thread is old or new, if I went and stuck today's date on the thread would that make U happy, on that note have a nice day

Actually the mods would prefer you not dig up old threads but start a new one.

ojaverde
September 7th, 2011, 05:17 PM
REgarding the AB165 BAssman, after reverting to a true bias situation and yanking those two 220K resistors connected to the power tubes' plates, imho that amp is a rock monster


Wally, how hard is it to remove these two resistors? I have an 1967 AB165 Bassman and this seems like a easily reversable mod that I would like to try.