Combine AB165 normal channel with AA864 normal channel??

[sheeba]

I have an AB165 amp 1968. It's rebuilt stock. I tried the AA864 normal channel mod and liked it but I also like the AB165 normal channel. How can I combine these two amps? When I tried the AA864 normal on the otherwise stock Ab165 I got a lot of hiss whenever the volume was up on the bass channel. I switched back to stock and all is well. Does anyone have a schematic for something like that?

Thanks,
RK

[Stevem]

The normal channel on both of these amps are the same so I do not understand why you like one over the other?
The ab165 version of the Bassman head does use a 6th power supply node that the 5 node 1964 version does not, but both appear to use the same power transformer!
Also the Bass channel on both of these amps feeds a cathode follower stage before the phase inverter that the normal channel does not so if you do not mod the amp for that fact, then trying to make a Bass channel into a normal channel will never get you that same normal channel sound !

You can find both schematics on line, just type in Fender aa165 schematic .

[sheeba]

The normal channel on the AB165 has an extra gain stage that I want to retain. It's not the same as the other variants. It has a local feedback resistor etc. In addition I want the same layout without the final gain stage as in the AA864 or AA165 normal channel. My question is how would I properly combine these two channels. I tried a set or 220's before the 500pf cap and I got a lot of noise when the volume of the AB165 channel volume was up regardless if there was anything plugged in. I figured I just didn't combine the channel correctly. The phase inverter and the power section are wired AA864 BTW.

[Stevem]

Both normal channels are exactly the same.
Each normal channel ends at the junction of the 100k plate load resistor and the 220k mixer resistor .

[martin manning]

The normal channel on the AB165 has an extra gain stage that I want to retain. It's not the same as the other variants. It has a local feedback resistor etc. In addition I want the same layout without the final gain stage as in the AA864 or AA165 normal channel. My question is how would I properly combine these two channels.

Something like this?

[sheeba]

Both channels are exactly the same until the 220k resistor but there is more to the ab165 channel. I want the whole AB165 normal channel all the way to the phase inverter. This would include the "mixer stage" or 3rd gain stage which is not part of the other circuits normal channel. I'm talking about the AB165 normal channel and not the AA165. What I want is to leave the AB165 normal channel as is ,remove the AB165 bass channel and install an AA864 channel in it's place.

[sheeba]

The normal channel on the AB165 has an extra gain stage that I want to retain. It's not the same as the other variants. It has a local feedback resistor etc. In addition I want the same layout without the final gain stage as in the AA864 or AA165 normal channel. My question is how would I properly combine these two channels.

Something like this?

Yes Like that!!

I'll give it a try
Thank You!

[martin manning]

I'm interested to hear how it works out. You may need to tweak it some, and note that if you try to jumper the two channels it won't sound good- the signals are out of phase at the 220k mixing resistors.