Fender Bassman, Guitar Amp Information

Fender Bassman AB165 Mod – Switchable bass slope resistor part 1 – Remove death cap and bypass ground switch

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This mod is the preface to putting in a switchable slope resistor for the bass channel.  First, unless you want to drill a hole to mount a switch, you may as well use the unneeded ‘ground switch’.  Also, if your amp still has the death cap, it will have to go, as well.  😉 You will need two 8 inch lengths of cloth covered stranded wire, if you wish to stay ‘period specific’.  Otherwise, you can use regular stranded wire, if that doesn’t concern you.  (I would keep the wire that you remove in case you wish to revert….) THIS LINK, Angela, has everything you might need, from cloth covered wire, to caps, or whatever.  So, besides the two 8 inch lengths of wire, you will need basic soldering skills.

And MAKE SURE that you discharge the caps, and verify it (like the video below) and UNPLUG the amp, since you will be working on the AC mains.

DO NOT MODIFY A RARE LEO FENDER AA864 CIRCUIT!!  ALSO, DO NOT ATTEMPT TO WORK ON THESE AMPS UNLESS YOU KNOW WHAT YOU ARE DOING, AS THEY CONTAIN VOLTAGES THAT ARE LETHAL AND WILL KILL YOU!!!

That being said, here’s a great video showing you how absolutely easy it is to discharge the filter caps in a tube amp.  This is how I’ve done it my whole life.  Remember, when in doubt, measure the B+ with a DMM!

In the picture at the right, you will notice the area that we will be concerned with, 20160909_104348_001and should be fairly common across the different Bassman circuits:  AA864, AA165, AB165….  You will notice on the right, that this amp has had the power cord replaced, and connected the hot and neutral wires to the two wire socket.  These wires are daisy chained across the ground switch before reaching the power switch and fuse holder.

20160909_105639-modFirst, we will remove the two small lengths of cloth covered wire connecting the black wire to the ground switch and the fuse holder.  As you can see in the picture to the left, I have removed those two wires from the terminals marked by the red arrows.

Next,we will remove the two small lengths of cloth covered wire connecting 20160909_111324_001-modthe white wire to the ground switch as well as the main power switch.  As you can see in the picture at the right, the points that I removed those wires from marked by red arrows.  You will also notice that the ‘death cap’ has been removed, as marked by the two green arrows.  (I actually just snipped off the lead going through the hole.)

20160909_112615Next, in preparation for actually wiring things back up, I removed the black and white power wires from the two wire socket.  I also cleaned out all the terminals of excess solder as you can see in the picture at the left.  I used a solder removal tool, but a cheap alternative is to use a round toothpick while heating up the terminal. 😉

Finally, we get to start wiring things back up!!  In the picture at the right,20160909_113804-mod you will notice that I slightly changed the orientation a little bit.  Now, the cloth covered wire is attached from the same direction as the white power cord.  (It’s far easier to get both wires through the terminal in the same direction.  I also marked the connection points with arrows.

Last connection!  20160909_120152-modIn the picture at the left, you can see that I connected the black wire to the fuse holder.  Now, we have the ground switch bypassed, and it can either be used, or replaced.   I will be installing a switchable bass slope resistor in the next installment.  I will remind you that solder ‘flows’ toward heat.  😉

Last check!  20160909_123918If you haven’t a lot of experience in doing things like this, I will suggest that you use a DMM to check continuity of all the changes that you have made.  Since I have 40 years experience, I simply plugged it in, and turned it on.  You will notice the maintenance stand that I built in an earlier post.  It makes it a lot easier to work on (and then test) your Bassman amp after you make changes.  I suggest that you make one.  Keep tuned for part 2.  😉

 

Fender Bassman, Guitar Amp Information

Fender Bassman AB165 Mod – Bass Ch. Tone Mod Easy (Slope Resistor Cont.)

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This is the sixth installment on modifying a vintage Fender Bassman amp.  This will be a continuation of the last segment’s topic of altering the Bass Ch Slope Mod schematicvalue of the bass channel’s ‘slope’ resistor.  Last time, we took it from the stock 100K value down to 47K.  This time, we will push it even further down to 33K.  This should raise the gain a bit more and give the sound even more bite to it.  Once again, I am posting the schematic and layout Bass Ch Slope Mod layoutso that you can see exactly what we are talking about.  But, please remember to make absolutely SURE that the circuit is totally safe before touching anything.  This link to an earlier mod has a great  video that shows how easy it is to ensure that the filter caps are discharged in a tube amp.  Make SURE to watch the video!!

DO NOT MODIFY A RARE LEO FENDER AA864 CIRCUIT!!  ALSO, DO NOT ATTEMPT TO WORK ON THESE AMPS UNLESS YOU KNOW WHAT YOU ARE DOING, AS THEY CONTAIN VOLTAGES THAT ARE LETHAL AND WILL KILL YOU!!!

First, here’s a clip of the unmodified bass channel.  (100K slope resistor, and the hi-cut cap in the circuit.)

Bass Channel Unmodified

 

From the last segment, this is with the slope resistor changed to 47K, and the hi-cut cap removed from the circuit.

Bass and Guitar Channel 47K Ohm bass slope A/B

 

Finally, this is with the slope resistor changed to 33K and of course the hi-cut cap removed from the circuit.

Bass and Guitar Channel 33K Ohm bass slope A/B

 

Another possible value might be 68K for a reduction in the overall gain, (actually, a slight increase in gain from the stock 100K) and a more treble sound (a bit less treble than stock).  So, you get the picture.  Lowering the slope resistor value will raise the gain, and decrease the treble, and give it more bite.  At any rate, this gives you an idea of how changing that slope resistor will change the overall gain and voicing.  Remember, if you want to play a bass guitar through the bass channel, just flip the deep switch on, which will help to eliminate the higher frequencies.  😉

Fender Bassman, Guitar Amp Information

Fender Bassman AB165 Mod – Bass Ch. Tone Mod Easy (Slope Resistor)

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This blog post will show you how EASY it is to end up with a Fender Bassman Bass Channel that is ‘guitar-usable’.  This is done with only one simple  change to the tone stack, in addition to the capacitor mod that I’ve already gone over.  If you want an even MORE Marshall type tone, you can either make a few changes to the first gain stage’s cathode circuits and/or make some changes to the tone stack.  (One such tone stack mod that I recommend might be to simply change the value of the slope resistor, so that the midrange isn’t so attenuated.)  I will go over this tone stack EASY mod at this time.

DO NOT MODIFY A RARE LEO FENDER AA864 CIRCUIT!!  ALSO, DO NOT ATTEMPT TO WORK ON THESE AMPS UNLESS YOU KNOW WHAT YOU ARE DOING, AS THEY CONTAIN VOLTAGES THAT ARE LETHAL AND WILL KILL YOU!!!

Or, if you ARE going to modify an AA864 circuit, stick to the bass channel, and make SURE that they are easily reversible.  😉

This is the fifth installment on modifying an AB165 Fender Bassman amp, and Bassman Bass Ch Slope modthe second part to modifying the bass channel.  Since you will be changing the slope resistor and the tone, a test fixture like the one here will help you get the sound you want, but if you utilize this method with testing the mod, please make sure that the circuit is discharged by verifying with your DMM….  (If you look closely, you will still see the cap in the bass channel on the left lifted.) You will also notice the settings that I chose to use, as well as the A/B switch and Power Soak that I used.  😉  Now, let’sBass Ch Slope Mod schematic discuss a bit about what changing the slope resistor will do.  At 100K, it’s a bit of a ‘gain robber’ and gives you that nice treble ‘fender chime’.  Changing it’s value lower to either 68K or 47K moves the ‘midrange dip’ a bit and will get a little less treble and a bit more bass.  (My AA864 Bassman actually came with the slope resistor of the guitar channel set to 47K, Bass Ch Slope Mod layoutwhich I moved back to 100K, so that the guitar channel was totally stock.)  If I left the bass channel slope resistor at 100K, I would have two almost identical voiced channels, so I chose to give it a bit more ‘bite’ by lowering its slope resistor to 47K.  (You could even get into this type mod even further by changing the capacitor values in the tone stack.)  I may get into this later, but for now, I think I have my amp sounding the way I like it, simply by two easy mods.  Bassman Slope resistor modOn the left, is Jim’s AB165 amp.  You will notice that I circled in red the bass channel slope resistor, and for your reference, I circled in green, the guitar channel slope resistor (which is at the stock 100K value).  Now, let’s hear a short sound clip and A/B the guitar and bass channels.

Bass and Guitar Channel A/B

 

The above sound clip was recorded using NO pedals, except for the DOD A/B switch.  The amp settings were identical in each channel: Volume at 3.5, Bass and Treble at 5.  Amp output to the Power Soak dialed way down into a Sonic 2X15 Half Stack.  I was using a 2005 Gibson SG set to the treble position, and the volume and tone controls at max.  Your mileage may vary, unless you have removed the negative feedback as detailed in an earlier segment.  (My AA864 circuit has no such feedback, so my sound clip might have more ‘hair’ than yours.)  Hope this helps.  😉

As an afterthought, in case you need to be reminded of how the bass channel sounded before mod, listen to this sound clip.  😉

Bass Channel Unmodified

 

Music News

Massive Bootleg Upload

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Well, I finally got around to sending these bootlegs to the server.  The upload is about 33 GB, and contains mostly either soundboard,  FM broadcasts, and a few good or excellent sounding audience recordings.  This update contains (to name a couple high points), 10 King Crimson bootlegs, and every known Blind Faith bootleg.  This music is already in the playlist of CRAB for your enjoyment.  😉

The album list of this upload follows:

ACDC – 2015-04-10 – Live At Coachella Festival (HQ-AUD)
ACDC – 2015-06-07 – Stadion Letzigrund, Zurich (HQ-AUD)
Aerosmith – 1994-08-13 – Woodstock Saugarties, NY (SBD) – CD 1
Aerosmith – 1994-08-13 – Woodstock Saugarties, NY (SBD) – CD 2
Allman Brothers – 1994-08-14 – Woodstock Saugarties, NY (SBD) or (HQ-AUD)
Allman Brothers Band – 1970-05-09 – Georgia Tech (SBD)
Allmans – 1971-08-26 – A&R Studios, NY (SBD)
Badfinger – 1972-04-07 – Kansas City, MO (SBD)
Blind Faith – 1969 – Compensation For Betrayal, Six Show Boxset (AUD)
Blind Faith – 1969-06-07 – Hyde Park, London (SBD)
Blind Faith – 1969-06-07 – London (SBD)
Blind Faith – 1969-06-18 – Gothenburg (AUD)
Blind Faith – 1969-06-18 – Gothenburg The Undertaker (AUD)
Blind Faith – 1969-06-18 – Konserthuset, Stolkholm, Sweden (VG-AUD)
Blind Faith – 1969-07-26 – West Allis,Wisconsin (SBD)
Blind Faith – 1969-08-16 – Santa Barbara, CA (SBD)
Bob Dylan – 1994-14-08 – Woodstock Saugarties, NY (SBD)
Boston – 1977-03-19 – KBFH (FM)
BTO – 1984-07-01- Harpo’s, Detroit, MI (FM)
Canned Heat – 1972 – WBCN Studios Boston Disc 1 (FM)
Canned Heat – 1972 – WBCN Studios Boston Disc 2 (FM)
Charlie Daniels Band – 1979-02-02 – Passaic NJ (FM)
Cinderella – 2000-07-16 – Tampa (SBD)
Cream – 1967-10-15 – Dazed & Cream – Detroit
Crosby Stills & Nash – 1994-08-13 – Woodstock, NY (SBD)
Def Leppard.- 1988-02-12-13 – Denver, Live in Your Face (SBD)
Delaney & Bonnie – 1971-07-22 – A & R Studios, NY (FM)
Derek & The Dominoes with Duane Allman – 1970-12-01 – Tampa, FL (VG-AUD)
Derek and the Dominos – 1970-10-23 – Live at the Fillmore late show (HQ-AUD)
Dire Straits – 03-06-1979 – The Tower Theatre, Upper Darby (SBD)
Dire Straits – 1978-10-19 – Rotterdam, Holland (FM)
Dire Straits – 1985-08-16 – Majestic Theatre, San Antonio, TX (SBD)
Dire Straits – 1986-04-26 – Sydney, Australia (SBD)
Dixie Dregs – 1978-05-30 – Lee Furr’s Studio, Tucson, AZ (FM)
Eric Clapton – 1976-11-15 – Convention Center Dallas (FM)
Foghat – 1976 – King Biscuit Flower Hour (FM)
Frampton – 1975-03-24 – The Record Plant, Sausalito, CA (FM)
Gentle Giant – 1977-02-05 – Boston, MA Dan Lampinski (EX-AUD)
George Harrison – 1974-11-12 – Los Angeles, CA (SBD)
Golden Earring – 1975-04-25 – Live at Winterland (SBD)
Golden Earring – 1975-04-26 – Live at the Record Plant KSAN (FM)
Govt Mule – 1995-09-12 – Fayetteville, AR (SBD)
Govt Mule – 1995-09-23 – Macon, GA (SBD)
Govt Mule – 1996-12-29 – Philadelphia, PA (SBD)
Grand Funk Railroad – 1970-07-29 – Hampton Beach Casino
Grand Funk Railroad – 1971-07-18 – Live at Osaka Stadium, Osaka, Japan (VG-AUD)
Grand Funk Railroad – 1971-12-04 – Dusseldorf (AUD)
Grand Funk Railroad – 1972 – In Concert Madison Square Garden (23.12.1972) (SBD)
Grand Funk Railroad – 1974-06-02 – Live in L.A.Forum (1974.06.02) (SBD)
Grateful Dead – 1968-12-29 – Gulfstream, FL (SBD)
Grateful Dead – 1969-09-01 – Baton Rouge LA (SBD)
Grateful Dead – 1976-06-11 – Boston Music Hall, MA (SBD)
Grateful Dead – 1994-07-20 – Noblesville IN (SBD)
Greg Kihn Band – 1981-08-05 – West Orange, NJ (FM)
Greg Kihn Band – 1984-07-14 – Santa Cruz, CA (FM)
Guess Who – 1974-05-06 – KSHE (FM)
Guess Who – 1983-05-27 – Vancouver, Canada (SBD)
Guns N’ Roses – 1988-02-02 – Live At The Ritz, New York (SBD)
Guns N’ Roses – 1992 – PracticeForDestruction (SBD)
Guns N’ Roses – 2002.12.02 – Fleet Center, Boston, MA (SBD)
Hot Tuna – 1988-03-04 – Fillmore,SF (SBD)
Hot Tuna – 1992-01-25 – SEVA Benefit, Berkeley (SBD)
Jefferson Airplane – 1966-09-30 – San Francisco, CA (SBD)
Jefferson Airplane – 1966-11-26 – San Francisco, CA (SBD)
Jefferson Airplane – 1967-03-04 – Cafe A Go Go, NY (SBD)
Jefferson Airplane – 1967-08-05 – Toronto, Canada (SBD)
Jefferson Airplane – 1968-01-30 – Matrix, SF (SBD)
Jefferson Airplane – 1969-06-13 – Family Dog, SF (FM)
Jefferson Airplane – 1969-10-25 – Winterland, SF (SBD)
Jefferson Airplane – 1969-10-26 – Winterland, SF (SBD)
Jefferson Airplane – 1970-04-15 – Winterland, SF (SBD)
Jefferson Starship – 1975-05-12 – Central Park, NY (FM)
Jefferson Starship – 1976-07-14 – Hartford, CT (SBD)
Jimi Hendrix (Jimmy James) – 1965-12-26 – Hackensack, NJ (SBD)
Jimi Hendrix – 1965-12-26 Hackensack, NJ (SBD)
Jimi Hendrix – 1967-11-10 – Bussum, The Netherlands (FM)
Jimi Hendrix – 1968-03-19 – Ottawa, Canada (SBD)
Jimi Hendrix – 1970-01-22 – KPFA Tapes SF (SBD)
Jimi Hendrix – 1970-07-04 – Atlanta, Georgia (SBD)
Jimi Hendrix – 1970-07-04 – International Pop Festival, Atlanta, GA (SBD)
Jimi Hendrix – 1970-07-17 – Downing Stadium Randalls Island (SBD)
Jimi Hendrix – 1970-07-30 – Haleakala Maui (SBD)
Joe Bonamassa – 2009-03-08 – Turner Hall Ballroom, Milwaukee (SBD)
John Lennon – 1972-08-22 – SIR Studios, NY (SBD)
Judas Priest – 1986-05-23 – Saint Louis 86 (SBD)
King Crimson – 1969-07-05 – KCCC12 Live in Hyde Park (2002)
King Crimson – 1971-05-11 – KCCC14 Live at Plymouth Guildhall 1971 (2001)
King Crimson – 1972-03-12 – KCCC9 Live at Summit Studios Denver (2000)
King Crimson – 1973-1974 – CAT FOOD
King Crimson – 1974-07-01 – KCCC10 Live in Central Park NYC (2000)
King Crimson – 1981-04-30 – KCCC11 Live at Moles Club Bath (2000)
King Crimson – 1982 – KCCC4 Live at Cap DAdge (1999) mp3 only
King Crimson – 1982-08-13 – KCCC16 Live In Berkeley
King Crimson – 1997-05 – KCCC13 Nashville Rehearsals (2000)
King Crimson – 1998-07-01 – KCCC17 ProjeKct Two Live in Northampton 1998 (2001)
Led Zeppelin – 1969-10.10 – LOlympia, Paris (SBD)
Led Zeppelin – 1973-05-28 – Sports Arena, San Diego (SBD)
Led Zeppelin – 1975-02-13 – Nassau Colisseum, LI (SBD)
Led Zeppelin – 1977-05-26 – Capitol Center, Landover (SBD)
Lynyrd Skynyrd – 1976-02-15 – Hammersmith (FM)
Lynyrd Skynyrd – 1976-04-07 Boston, MA Dan Lampinski (EX-AUD)
Marshall Tucker Band – 1976-03-13 – Uniondale, NY (FM)
Metallica – 1991-09-28 – Monsters Of Moscow (SBD)
Metallica – 1996-12-11 – Prins van Oranje Hal, Utrecht, Holland (FM)
new4.txt
Paul McCartney & Ringo Starr – 2014-01-27 – Los Angeles CA (SBD)
Paul McCartney & Wings – 1976-06-23 Wings Over LA (SBD)
Peter Frampton – 1975-07-04 – Dallas, TX (FM)
Pink Floyd – 1970-04-20 – Interstellar Fillmore (SBD)
Pink Floyd – 1975 – Wish You Were Here (Extraction Version) (SBD)
Pink Floyd – 1994-09-13 – Torino, Italy A Passage Of Time (SBD)
Pink Floyd – 2005-07-02 – Live From Hyde Park (SBD)
Police – 1979-05-04 – Miami (SBD)
Renaissance – 1974-11-24 – Philadelphia, PA (SBD)
Ringo Starr – 1992-07-13 – Live at Montreux Switzerland (SBD)
Rossington Collins Band – 1980-12-31 – Atlanta, GA (FM)
Rush – 1996-12-05 – Bigger & Better In Texas, Houston, TX (SBD)
Santana – 1970-08-18 – Tanglewood, MA (SBD)
Santana – 1971-03-23 – The Forum, Los Angeles, CA (SBD)
Santana – 1978-03-18 – Cal Jam 2, Ontario, CA (SBD)
Scorpions – 1993-10-16 – Munich Broadcast Master (FM)
Steppenwolf – 1968-08-27 – Fillmore West, SF (SBD)
Steve Miller – 1975-04-12 – Beacon, NY (SBD)
Styx – 1977-11-04 – Boston, MA Dan Lampinski (EX-AUD)
Styx – 1977 – Mantra Recording Studios, Chicago (FM)
Ten Years After – 1973-05-08 – Sports Stadium, Orlando, FL (SBD)
The Beatles – 1964-06-28 – Indiana State Fair, Indianapolis, IN (SBD)
The Beatles – 1965-08-15 – Shea Stadium Flushing NY (SBD)
The Beatles – 1968-05-xx – Esher, UK Unplugged (SBD)
The Beatles – 1969-01-30 – Apple Rooftop Concert (SBD)
The Doors – 1968-09-20 – The Complete Stockholm 68 Tapes, Both Shows (SBD)
The Doors – 1970-08-29 – Isle Of Wight, UK (SBD)
The Georgia Satellites – 1988-10-07 – Town & Country, London (FM)
The Kinks – 1972-11-16.- Felt Forum, NY (SBD)
The Runaways – 1978-01-07 – The Palladium, NY (FM)
The Who – 1999-11-12 – House Of Blues, Chicago (HQ-AUD)
Tom Petty – 1978-12-31 – Santa Monica CA (SBD)
Tom Petty – 2003-04-19 – Vic Theater, Chicago, IL (FM)
Traffic – 1970-04-30 – London, England (FM)
Traffic – 1972-02-12 – Santa Monica California (SBD)
Traffic – 1973-01-26 – Winterland (SBD)
Traffic – 1994-08-13.14 – Woodstock Saugerties, NY (SBD)
Uriah Heep – 1971-05-07 – Volkshaus, Zurich (VG-AUD)
Uriah Heep – 1973-03-16 – Budokan, Tokyo, Japan (VG-AUD)
Uriah Heep – 1973-08-19 – Portland, Maine (VG-AUD)
Uriah Heep – 1973-08-25 – Buffalo, NY (VG-AUD)
Uriah Heep – 1974-02-08 – San Diego, CA (SBD)
Uriah Heep – 1976-05-06 – Boston Dan Lampinksi (EX-AUD)
Uriah Heep – 1976-05-06 – Boston, MA (EX-AUD) Dan Lampinski
UriahHeep – 1985-05-16 – Glasgow
US Festival – 1983 – Heavy Metal Day (SBD)
Van Halen – 1980-05-01 – Capitol Theater, Largo, MD (SBD)
West, Bruce & Laing – 1973-04-14 – Live in K-Town – Germany (SBD)
Wishbone Ash – 1974 – New Jersey (FM)
Wishbone Ash – 1977-10-30 – Rainbow Theatre (SBD)
Yes – 1971 – Perpetual Change (SBD)
Yes – 1971-07-24 – Yale Bowl, New Haven, CT (SBD)
Yes – 1978-10-28 – Wembley Arena 78 (SBD)
Yes – 1979-04-18 – Circus Of Heaven (SBD)
Yes – 1979-04-18 – Circus of Heaven RMST – Quebec (SBD)
Yes – 1991-06-03 – Le Palais de Omnisports de Paris, Bercy, France (SBD)
Yes – 1991-07-21 New York – Ultimate Reunion (EX-AUD)
Yes – 1994-08-11 – Orlando, FL (SBD)
Yes – 2004 – Estival Jazz Lugano (SBD)
Yes – 2013-08-10 – Soaring Eagle Casino & Resort, Mount Pleasant (EX-AUD)
Yes – Studio Outakes – Closer To The Edge (SBD)
Yes 1971-07-23 – NYC, NY No.3 – upgrade (VG-AUD)
Yes 1971-07-24 New Haven CT Yale Bowl TheTooleMan Mix (SBD)
Yes 1979-04-18 Circus of Heaven RMST – Quebec (SBD)
Yngwie J. Malmsteen – 1994 – Live At Budokan (SBD)
ZZ Top – 1980-04-15 Tres Hombres In Clarkston (SBD)

Enjoy!

 

Tech, music, and general ramblings…..