Bassman Circuitry

wooza

Joined: Apr 24, 2006
Posts: 1618
Ithaca, NY
1 Download Pin

Posted on Nov 20 2007 10:23 AM

Anybody know what the sonic differences are between the AA864 and AB165 Bassman circuits? I'm looking for a bassman and, having heard good things about AA864's, I've been wondering if that would be something worth being extra patient for. Anybody able to compare the two?

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zak

Joined: Sep 24, 2007
Posts: 2728
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Posted on Nov 20 2007 11:06 AM

This post has been removed by the author.

Last edited: Sep 23, 2009 15:35:16

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diceophonic

Joined: May 20, 2006
Posts: 2169
PacNW (Vancouver, Wa U.S.A.)
United States

Posted on Nov 20 2007 11:17 AM

short and sweet AB165 was a CBS creation, CBS messed with the circuit, AA864 pre-CBS man this circuit is more guitar friendly then AB165 IMO, AA864 has more brilliant tone and presence that's why I went with a '64 Bassman that sold me! that's what I did before I got into a Bassman I compared both heads through the same 2x12 cab to hear the differences

Back in '06 The Kilaueas! from Germany came to the west coast on tour and they hit Portland and we hosted and we had them stay with us, When they came over to my place Ralf played through my '64 Bassman and he was sold, each city they played at they used a backline, he especialy requested to play my Bassman for thier Portland show he was very impressed and amazed at the circuit AA864 tone! and back home he plays through a '64 Showman

here's a few shots of them at my place trying out my Bassman

Here's Ralf at the show playing through my '64 Bassman

—

-Kyle

Beyond The Surf YouTube channel
Beyond The Surf Instagram
The Verbtones @ Instagram
The Verbtones @ Facebook
The Verbtones @ bandcamp

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diceophonic

Joined: May 20, 2006
Posts: 2169
PacNW (Vancouver, Wa U.S.A.)
United States

Posted on Nov 20 2007 11:25 AM

zak
I don't think you will hear any real "sonic differences" - the difference between the circuits lies in how the bias is adjusted.

Nah man the circuit is a big part of it, biasing, tubes, speakers are the last things especially the speakers will have the last say in tonal/sonic differences, you can have the hottest killer head around but the speakers are the last say in interpreting the circuit's sound.

—

-Kyle

Beyond The Surf YouTube channel
Beyond The Surf Instagram
The Verbtones @ Instagram
The Verbtones @ Facebook
The Verbtones @ bandcamp

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PhatTele

Joined: Jun 05, 2006
Posts: 445

Posted on Nov 20 2007 11:43 AM

It's hard to pin down what an AB165 really is unless you're looking right at the circuit board. A BF AB165 looks different than an early SF drip edge AB165. In fact, Fender changed something in the Bassman just about every year they were in production. I've been inside a couple of dozen of these amps and I can honestly say that no two have ever looked alike.

That being said, you need to look at the schematic/layout drawings of the AA864 and the AA165/AB165 to see where the major differences lie (and they're throughout the circuit....not just in the bias section). The differences are subtle but they do have a large effect in the overall tone of the amp. It's worth it, even with a BF AB165 to mod it back to the AA864 circuit. I have no qualms about doing this mod, since, in the end, it's a better amp.

BTW - My favorite Bassmans are the blonde era circuits.

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zak

Joined: Sep 24, 2007
Posts: 2728
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Posted on Nov 20 2007 11:53 AM

This post has been removed by the author.

Last edited: Sep 23, 2009 15:35:27

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WR

Joined: Feb 27, 2006
Posts: 3832
netherlands
2 Link Pins

Posted on Nov 20 2007 11:53 AM

I cant say for the ab165 and I dont have time to check the circuits, but I recently swapped the circuitboard of my aa371 (the one after ab165) for a aa864 board (well, normal channel only, as I was short of time, parts and mood ) and the differnece is pretty major. I dont buy the preCBS -price-s-through-the-roof mantra, there great post '65 stuff around, buut in this case.... pretty much the differnece between a great beer, and a great beer, but someone peed in it....

as said, conversions are really not that hard, and shouldnt run more than 200 bucks, less if you have friends. just something to think about.

look at the schematics to judge how ab165 compares to all of this, as I dont have time to check.

KYLE: ditto on the speakers, but wooza's asking which head ceteris paribus

—

Rules to live by #314:
"When in Italy, if the menu says something's grilled, don't assume it is."

https://www.facebook.com/The-Malbehavers-286429584796173/

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diceophonic

Joined: May 20, 2006
Posts: 2169
PacNW (Vancouver, Wa U.S.A.)
United States

Posted on Nov 20 2007 11:54 AM

Back dating a circuit is another excellent option and it's always reversible.

—

-Kyle

Beyond The Surf YouTube channel
Beyond The Surf Instagram
The Verbtones @ Instagram
The Verbtones @ Facebook
The Verbtones @ bandcamp

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diceophonic

Joined: May 20, 2006
Posts: 2169
PacNW (Vancouver, Wa U.S.A.)
United States

Posted on Nov 20 2007 12:04 PM

WR
KYLE: ditto on the speakers, but wooza's asking which head ceteris paribus

It was only more candy for the cake, I know he wasn't asking about speakers, I was just simply sharing the Bassman/Amp as a whole, the big picture in decision making and the comparisons if you have the luxury to but the heads to the test with the cab you already have or the shop has when I bought my 64' Bassman I took my 2x12 cab to make the comparison and that help out tons to make the call of AA864 or AB165
so the winner for me was AA864 just trying to help out mate

—

-Kyle

Beyond The Surf YouTube channel
Beyond The Surf Instagram
The Verbtones @ Instagram
The Verbtones @ Facebook
The Verbtones @ bandcamp

Top

WR

Joined: Feb 27, 2006
Posts: 3832
netherlands
2 Link Pins

Posted on Nov 21 2007 06:36 AM

diceophonic
It was only more candy for the cake

yummie, Kyle!

Wooza, I looked at the schematics quickly, main differnece is that from AB165 and onwards, the normal channel has the extra gainstage of the basschannel. My guess is this is what makes it sound muffled, with a bottomhavy sound and unfocussed lows. BUT, when I changed from aa731 to aa864, I put in a entire new board, so maybe all fresh caps helped too. I didnt use any boutique parts, caps were Webers, vishay and nobrands, no carbon comp reistors either. just fyi.

consider that with any old amp you buy, you most likly want a tune up anyway. If I were you Id get a quote froma local tech for a complete check-up AND a aa864-conversion of a SF or AB165. then make a lsit of what your options are, set a price for what you want to pay max for all types of bassman, and then start looking.

—

Rules to live by #314:
"When in Italy, if the menu says something's grilled, don't assume it is."

https://www.facebook.com/The-Malbehavers-286429584796173/

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wooza

Joined: Apr 24, 2006
Posts: 1618
Ithaca, NY
1 Download Pin

Posted on Nov 21 2007 02:05 PM

Good advice. Thanks Wannes.

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wooza Joined: Apr 24, 2006 Posts: 1618 Ithaca, NY	Posted on Nov 20 2007 10:23 AM Anybody know what the sonic differences are between the AA864 and AB165 Bassman circuits? I'm looking for a bassman and, having heard good things about AA864's, I've been wondering if that would be something worth being extra patient for. Anybody able to compare the two? Top
zak Joined: Sep 24, 2007 Posts: 2728	Posted on Nov 20 2007 11:06 AM This post has been removed by the author. Last edited: Sep 23, 2009 15:35:16 Top
diceophonic Joined: May 20, 2006 Posts: 2169 PacNW (Vancouver, Wa U.S.A.)	Posted on Nov 20 2007 11:17 AM short and sweet AB165 was a CBS creation, CBS messed with the circuit, AA864 pre-CBS man this circuit is more guitar friendly then AB165 IMO, AA864 has more brilliant tone and presence that's why I went with a '64 Bassman that sold me! that's what I did before I got into a Bassman I compared both heads through the same 2x12 cab to hear the differences Back in '06 The Kilaueas! from Germany came to the west coast on tour and they hit Portland and we hosted and we had them stay with us, When they came over to my place Ralf played through my '64 Bassman and he was sold, each city they played at they used a backline, he especialy requested to play my Bassman for thier Portland show he was very impressed and amazed at the circuit AA864 tone! and back home he plays through a '64 Showman here's a few shots of them at my place trying out my Bassman Here's Ralf at the show playing through my '64 Bassman — -Kyle Beyond The Surf YouTube channel Beyond The Surf Instagram The Verbtones @ Instagram The Verbtones @ Facebook The Verbtones @ bandcamp Top
diceophonic Joined: May 20, 2006 Posts: 2169 PacNW (Vancouver, Wa U.S.A.)	Posted on Nov 20 2007 11:25 AM zak I don't think you will hear any real "sonic differences" - the difference between the circuits lies in how the bias is adjusted. Nah man the circuit is a big part of it, biasing, tubes, speakers are the last things especially the speakers will have the last say in tonal/sonic differences, you can have the hottest killer head around but the speakers are the last say in interpreting the circuit's sound. — -Kyle Beyond The Surf YouTube channel Beyond The Surf Instagram The Verbtones @ Instagram The Verbtones @ Facebook The Verbtones @ bandcamp Top
PhatTele Joined: Jun 05, 2006 Posts: 445	Posted on Nov 20 2007 11:43 AM It's hard to pin down what an AB165 really is unless you're looking right at the circuit board. A BF AB165 looks different than an early SF drip edge AB165. In fact, Fender changed something in the Bassman just about every year they were in production. I've been inside a couple of dozen of these amps and I can honestly say that no two have ever looked alike. That being said, you need to look at the schematic/layout drawings of the AA864 and the AA165/AB165 to see where the major differences lie (and they're throughout the circuit....not just in the bias section). The differences are subtle but they do have a large effect in the overall tone of the amp. It's worth it, even with a BF AB165 to mod it back to the AA864 circuit. I have no qualms about doing this mod, since, in the end, it's a better amp. BTW - My favorite Bassmans are the blonde era circuits. Top
zak Joined: Sep 24, 2007 Posts: 2728	Posted on Nov 20 2007 11:53 AM This post has been removed by the author. Last edited: Sep 23, 2009 15:35:27 Top
WR Joined: Feb 27, 2006 Posts: 3832 netherlands	Posted on Nov 20 2007 11:53 AM I cant say for the ab165 and I dont have time to check the circuits, but I recently swapped the circuitboard of my aa371 (the one after ab165) for a aa864 board (well, normal channel only, as I was short of time, parts and mood ) and the differnece is pretty major. I dont buy the preCBS -price-s-through-the-roof mantra, there great post '65 stuff around, buut in this case.... pretty much the differnece between a great beer, and a great beer, but someone peed in it.... as said, conversions are really not that hard, and shouldnt run more than 200 bucks, less if you have friends. just something to think about. look at the schematics to judge how ab165 compares to all of this, as I dont have time to check. KYLE: ditto on the speakers, but wooza's asking which head ceteris paribus — Rules to live by #314: "When in Italy, if the menu says something's grilled, don't assume it is." https://www.facebook.com/The-Malbehavers-286429584796173/ Top
diceophonic Joined: May 20, 2006 Posts: 2169 PacNW (Vancouver, Wa U.S.A.)	Posted on Nov 20 2007 11:54 AM Back dating a circuit is another excellent option and it's always reversible. — -Kyle Beyond The Surf YouTube channel Beyond The Surf Instagram The Verbtones @ Instagram The Verbtones @ Facebook The Verbtones @ bandcamp Top
diceophonic Joined: May 20, 2006 Posts: 2169 PacNW (Vancouver, Wa U.S.A.)	Posted on Nov 20 2007 12:04 PM WR KYLE: ditto on the speakers, but wooza's asking which head ceteris paribus It was only more candy for the cake, I know he wasn't asking about speakers, I was just simply sharing the Bassman/Amp as a whole, the big picture in decision making and the comparisons if you have the luxury to but the heads to the test with the cab you already have or the shop has when I bought my 64' Bassman I took my 2x12 cab to make the comparison and that help out tons to make the call of AA864 or AB165 so the winner for me was AA864 just trying to help out mate — -Kyle Beyond The Surf YouTube channel Beyond The Surf Instagram The Verbtones @ Instagram The Verbtones @ Facebook The Verbtones @ bandcamp Top
WR Joined: Feb 27, 2006 Posts: 3832 netherlands	Posted on Nov 21 2007 06:36 AM diceophonic It was only more candy for the cake yummie, Kyle! Wooza, I looked at the schematics quickly, main differnece is that from AB165 and onwards, the normal channel has the extra gainstage of the basschannel. My guess is this is what makes it sound muffled, with a bottomhavy sound and unfocussed lows. BUT, when I changed from aa731 to aa864, I put in a entire new board, so maybe all fresh caps helped too. I didnt use any boutique parts, caps were Webers, vishay and nobrands, no carbon comp reistors either. just fyi. consider that with any old amp you buy, you most likly want a tune up anyway. If I were you Id get a quote froma local tech for a complete check-up AND a aa864-conversion of a SF or AB165. then make a lsit of what your options are, set a price for what you want to pay max for all types of bassman, and then start looking. — Rules to live by #314: "When in Italy, if the menu says something's grilled, don't assume it is." https://www.facebook.com/The-Malbehavers-286429584796173/ Top
wooza Joined: Apr 24, 2006 Posts: 1618 Ithaca, NY	Posted on Nov 21 2007 02:05 PM Good advice. Thanks Wannes. Top

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