Fender Bassman AA864 build - diyAudio
Go Back   Home > Forums > Live Sound > Instruments and Amps

Instruments and Amps Everything that makes music, Especially including instrument amps.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 21st November 2014, 06:11 PM   #1
diyAudio Member
 
Join Date: Oct 2004
Location: Texas
Default Fender Bassman AA864 build

Hello,

I have done a lot of research and hope to build an AA864 head. I re-drew the circuit (helped me to work through it) and have all the parts here or on the way to do everything on it. I tried to be complete; every wire/connection that I can think of is on there, it is what I would build from.

The only changes I made (that aren't accidental!) are using only the normal channel, tube rectification (5F6A style), adjusting the last dropping resistor for the lack of the other small signal tubes, and changing from a fixed mid-frequency resistor in the tone stack to a potentiometer.

I plan to start cutting holes this weekend. Do you see any mistakes?

Thank you for looking through it,

Bill
Attached Files
File Type: pdf AA864 normal channel.pdf (42.9 KB, 40 views)
File Type: pdf Bassman-AA864-schematic.pdf (561.3 KB, 43 views)
File Type: pdf Weber power.pdf (148.8 KB, 17 views)
File Type: pdf classictone output.pdf (26.6 KB, 17 views)
  Reply With Quote
Old 22nd November 2014, 03:58 AM   #2
Poacher is offline Poacher  Canada
diyAudio Member
 
Join Date: Mar 2014
Location: Uxbridge, Ontario
Looks good to me.
  Reply With Quote
Old 22nd November 2014, 04:12 AM   #3
diyAudio Member
 
Join Date: Oct 2004
Location: Texas
Thank you for looking through it!

Bill
  Reply With Quote
Old 22nd November 2014, 09:08 AM   #4
diyAudio Member
 
Join Date: May 2010
Location: Hawkes Bay
If you are only building the one channel you won't need the 220k mixing resistor between V1b and the 500pF coupling cap - not that it would hurt to leave it in.
  Reply With Quote
Old 22nd November 2014, 02:41 PM   #5
diyAudio Member
 
Join Date: Oct 2004
Location: Texas
Thank you, I was wondering about that resistor. I wondered about its voltage divider effect with the following 1M grid resistor (it is easier for me to see/understand this effect in the circuit than its blending function with the bass channel).

Bill
  Reply With Quote
Old 29th November 2014, 03:52 AM   #6
Trout is offline Trout  United States
diyAudio Member
 
Trout's Avatar
 
Join Date: Nov 2004
Location: Midwest Madman
The screen resistors?
Why the extra 220's? 470 + 220 on each 6L6GC?
  Reply With Quote
Old 29th November 2014, 04:12 PM   #7
diyAudio Member
 
Join Date: Oct 2004
Location: Texas
I know the schematic calls for the 470R's; as I read I wondered if I needed a little more voltage drop at the screens, or just a bit more protection from them being potentially at or above the anode voltage in overdrive conditions. Not sure if it is a good idea or not.

So it really is just one 690R, I just already have a set of 470's and was adding.
  Reply With Quote
Old 30th November 2014, 05:15 AM   #8
Poacher is offline Poacher  Canada
diyAudio Member
 
Join Date: Mar 2014
Location: Uxbridge, Ontario
You can use one 690R but I would recommend them to be 5 watt rating. However, if you got the 470R at 1 watt, then adding the 220R at 1 watt would give you 690R at 2 watts, that should be better than the 470R 1 watt resistors as per schematic.
  Reply With Quote
Old 1st December 2014, 01:39 AM   #9
Trout is offline Trout  United States
diyAudio Member
 
Trout's Avatar
 
Join Date: Nov 2004
Location: Midwest Madman
Quote:
Originally Posted by Poacher View Post
You can use one 690R but I would recommend them to be 5 watt rating. However, if you got the 470R at 1 watt, then adding the 220R at 1 watt would give you 690R at 2 watts, that should be better than the 470R 1 watt resistors as per schematic.
How would wattage double when in series?
  Reply With Quote
Old 1st December 2014, 02:43 AM   #10
JMFahey is offline JMFahey  Argentina
diyAudio Member
 
JMFahey's Avatar
 
Join Date: Mar 2009
Location: Buenos Aires - Argentina
It won't double because they are not equal.

That said, just use a 470r but, as recommended, 5W .

You did a right thing: never ever build the "Bass instrument channel" which is plain horrible.

Even for Bass.

You don't need the mixing 220k .
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
59 Fender Bassman tmblack Instruments and Amps 3 15th November 2011 08:11 PM
a Fender bassman amp question krayon Instruments and Amps 7 24th October 2011 02:59 PM
5F6A Amp build help (Fender Bassman) RichBolduc Tubes / Valves 10 14th March 2010 10:40 PM
Fender Bassman Ten Benny Bennett Instruments and Amps 2 2nd April 2009 02:01 PM
Modifing A Fender Bassman Scheme amirmk Tubes / Valves 5 16th September 2005 08:34 PM


New To Site? Need Help?

All times are GMT. The time now is 01:11 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2