Bassman AA864 opinions?

[Taco John]

What do y'all think of the AA864 bassman vs the other versions?

 

[kavalero]

AA/AB165 & AA864 are very similar, not in the way the circuit is concerned (not an expert), but what I can hear as a player.
Over 10 Bassman Amps went thru my hands in the last 35yrs, including 2 x AA864.
I stopped at a '67 AB165, it makes me smile every time I play it.

 

[grolan1]

Which I could give you a detailed difference between the AA864 and the AB165 but I can't. What I can say is the AB165 I have currently in a custom 1x12 cabinet is my go to amp. Just a fantastic setup.

 

[Wally]

The AB 165 Bassman is different from the AA864 and AA165 Bassman circuits in more than one way, but the main difference is that both channels have three gain stages. This yields a very hot Normal channel for guitar work. From the AB165 through the Bassman 50 amps, this basic topography was maintained. The Bassman 10, 70, 100, and 135 amps have only two gain stages in each channel....that is why they are cleaner...as are the 864 and AA165 circuits.

 

[Lynxtrap]

AA864 may be the most "standard" Fender circuit of the different Bassman heads. The Normal channel is pretty much like the normal (dry) channel in any BF/SF amp.
The Bass channel has an extra gain stage, with some attenuation before it to tame the signal.
If I could choose any Bassman BF/SF head, this would probably be the one.

 

[Wally]

The Ab165 Normal channel is hotter than the first two BF Bassman circuits. (;^) just for grins, compare the AB165 Normal channel to the Trainwreck Express.....same basic topography. Interesting, new? I have to think that the similarity is not accidental.
The AB165 is unlike any other BF/SF amp when it comes to gain. Yes, the Fender Reverb amps have 3 gain stages in the reverb channel preamps, but the reverb and the vibrato effects drag the gain possibilities down. the AB165 Bassman is a hot guitar amp.

 

[grolan1]

I will have to say my AB165 is fairly hot with a thick warm middy type of sound. Nothing like my other BF Fender amps...

 

[Lynxtrap]

Might also be worth noting that you can't run the channels in parallell with the AA864, as they don't share the third gain stage. Of course, this is the case with all BF/SF amps with reverb, but it's a nice option with some of the other Bassmans.

As to how hot they are for guitar, there is plenty of heat to get from the AA864 Bass channel. The AB165 has a local feedback circuit around the third stage, the AA864 attenuates gain and high frequencies in a different way around the same stage.

Of course, is one is into modding, there are endless possibilities with these things.

 

[grolan1]

The AB165 has a local feedback circuit around the third stage, the AA864 attenuates gain and high frequencies in a different way around the same stage.

Of course, is one is into modding, there are endless possibilities with these things.

I actually used the 'un-used' ground switch to bypass the NFB - I run it without a feedback circuit most if not all the time. Way more crunch.

 

[kavalero]

I think the negative feedback loop allows Bassmans to have more headroom .. . by removing it, the amp distorts earlier?!!

 

[Wally]

Kavalero, that s why I install an adjustment on that NFB loop...to heat it up when wanted.

 

[kavalero]

Wally, is your adjustment installed as grolan1 mentioned above, on the ground switch?

 

[Wally]

You could use that hole. I usually use the ext spkr jack.

 

[Taco John]

Thanks for the input!

 

[King Fan]

Found this. I'm not smart enuf to evaluate it, but many here are. Interesting anyway.

http://acruhl.freeshell.org/mga/main/AA864_vs_AB165.html

 

[sliberty]

My favorite Bassman is the Blonde era 6G6B. The bass channel is totally brutal (in a good way). My second favorite is the AA864, which is the one I currently own (a clone actually). As others have said, the AB165 has an additional gain stage in the Normal channel which has pros and cons. On the positive side, you can jumper the channels. On the negative side, the Normal channel is pretty much just as hot as the bass channel, which means you've lost a tone variation that can be nice on the AA864.

I've added a few mods on my AA864. The big one is that I only built the bass channel. But then, I added a bright switch, a pre-phase inverter master volume, and I altered the way the deep switch works. The deep switch on mine switches the cathode capacitor on the first stage between 1uF and 25uF. The idea being that 1uF is more of a Marshall value (I didn't have a .68uF on hand), and the 25uF is the std Fender value. With the Marshall value, the amp is tighter, and accentuates the mids more, as you'd expect. This gives the amp 2 distinct voices.

 

[Paul G.]

For guitar, stock and modded, my favorite by far is the AB165. Add a real bias control (in addition to, or in place of the hum balance) and some quality tubes. Plug into either channel use the rule of 6 and you should be in a very good place.

P.

 

[tweedman2001]

For guitar, stock and modded, my favorite by far is the AB165. Add a real bias control (in addition to, or in place of the hum balance) and some quality tubes. Plug into either channel use the rule of 6 and you should be in a very good place.

P.

Rule of 6? Put every knob on 6? Inquiring minds need to know

 

[Paul G.]

Rule of 6? Put every knob on 6? Inquiring minds need to know

On a Fender with TMB controls it's 6Vol/6Treble/Mids3/Bass2 (mid x bass = 6).

On a Fender with Treble and Bass only the Mids are more or less set to where 4 would be on a pot

6 volume, 6 treble. Bass control starts at about 3 on a Bassman adjust to taste.

P.

 

[tweedman2001]

On a Fender with TMB controls it's 6Vol/6Treble/Mids3/Bass2 (mid x bass = 6).

On a Fender with Treble and Bass only the Mids are more or less set to where 4 would be on a pot

6 volume, 6 treble. Bass control starts at about 3 on a Bassman adjust to taste.

P.

Thanks