FENDER BASSMAN question

[Colas LeGrippa]

Hi everybody ! I am building a Fender Bassman amplifier for a friend, ( AA864 ) who doesn't want two channels only one ( to keep it simple and low priced ).  I see on the schems there's one more tube on the bass channel so, more gain. I 've nerver owned a Bassman amp, and don't know wether I should mod the bass channel for guitar, build the stock bass channel  or the stock normal channel, for max. tone. What do you guys think ?

Thanks !!!

Colas

[tubenit]

Colas,

Always great to see you posting here!  Bonjour!

That is sort of an odd Bassman selection to build? Typically, I think of Bassman scratch builds to be the 5F6A.

Not saying there is anything wrong with that amp but I can't say I remember anyone building that one from scratch?  In fact, I think that is one of the amps that the Dumblish clone guys tend to Dumblize, IIRC?  I'm not sure that design is highly regarded for guitar use?

IF you didn't Dumblize the amp design, then I would be inclined to make the Bass channel more like a AB763 preamp and then use the extra triodes to add reverb.  From the LTPI and on ........... you could leave it original.

With respect, Tubenit

[Colas LeGrippa]

Hola señor, happy to see you're still alive and well !
What makes you think the 5F6A is a better choice than the AA864 ? Personnal experience, popularity among amps builders or what ?

Hasta pronto !

Colas Coca

[sluckey]

I built the AA864 Bassman preamp into a dual purpose amp back in the '70s. That preamp sounds good for bass but not so good for guitar.

     http://home.comcast.net/~seluckey/amps/misc/76_Amp_Project.pdf

[Colas LeGrippa]

very nice, Sluckey !

After analyzing both circuits, AA864 and 5F6A,  one major difference I can see is that the 5F6A has a cathode follower driven tone stack  which is better in my opinion, ( having read about it )  though I've never built a plate driven tone stack. The other major  difference is the tube rectifier vs SS.   Can you imagine I've never had much interest in fender amps ? I owned a twin, a super, a princeton,  got rid of them all !!!!!!!!!  Now, I'd like to have them all back ......Now, looking at both schems, the 5F6A seems more interesting  IMHO according to simplicity, cathode follower and your own opinions ( I always listen to  professionnals hey hey though my gal isn't one...). I will swap the recto tube for a SS for more tightness and to get closer to the stock voltages shown on the schems. Since my power tranny yields 315-0-315,  a SS rectifier gives me 425V at the plates vs 430V with a higher HV tranny in conjunction with a GZ34, which is the same.

Muchas gracias ( my new girl friend is Cuban and she showed me spanish language , as well as other « muy intersantes cosas » .

Thank you guys.

Cheers !

Colas.

[tubenit]

The 5F6A is a very very popular clone and I think for good reason.

http://www.youtube.com/watch?v=Y0r1kVXSX3Q#ws

https://www.youtube.com/watch?v=5PaiDuiLzas

With respect, Tubenit

[Colas LeGrippa]

Jeff, if you tell me this amp is a stock Fender 5F6A, I'll pass the night woke up trying to finish it......sounds amazing |   Listen, is it your own amp ? If so, can you tell me what kind of speakers are in there ? If not, what speakers would you put in there? I personnally would put 4 X Eminence legend 10'' , but what'd be your choice ?

Thanks, you're my man.

Colas.

[tubenit]

Colas,

It's got a nice 3-D rich tone, doesn't it?  I remember hearing HotBluePlate's tweed 6L6 amp years ago and the thing sounded like it had reverb or something going on but it didn't.  Just a great sounding 3 dimensional sweet tone.  His might have been a 5E7 but I can't remember?

No, it's not mine.  I just like the way it sounded to me.  I think they came with P10R or P10Q Jensen speakers?  I'm not sure what I would be inclined to put in there?  Maybe some of the guys would have a suggestion.

I do like Emminence speakers and have used them quite a bit and have them in my current amps.  I don't know about the Legend 10.  I've used one of their 10" Ragin Cajun speakers and liked it quite a bit.

The 5F6-A is the only Fender "Bassman" that Doug carries a Hoffman style layout board for. 

Best regards, Jeff

[VMS]

Hi

ampbooks site has got a good analysis of the 5f6a circuit (actually a whole book):

http://ampbooks.com/mobile/classic-circuits/bassman-summary/

..and for blackface era bassman amps:

http://fenderguru.com/amps/bassman


-v

[Willabe]

Hey Alvin, you been out on the road?

The tweed Fender 5F6-A is the amp that Marshall copied to start with.


                      Brad     

[Colas LeGrippa]

yep Willabe, I've been out playing ''I'm goin' home'' with my Woodstock tribute band, without having any chance to get back home. to .............'' see''  my baby........!!!

I've heard the bassman sound demo posted by Tubenit ( thanks buddy )and must admit it sounds like a Marshall,,,,,,,,,,,,,,,,or rather the opposite ( Marshall sounding like Fender ). Anyway, at that time, Traynor, Fender, Marshall would probably drink beer together in a  bar somewhere , every now and then I guess....

Colas ''Fender'' LeGrippa

P.S.: what would you think guys of a new amplifier make ? I was thinkin' about an original name: Windshield ( nothing to do with Fender, I swear ).  Twin Windshield, Super Windshield, like it ?

[Willabe]

    'One of these days boy. Gonna see my baby, gonna see my ba-by, comin down the road.'


             Brad       

[Willabe]

The clean sound in the 1st/top video sounds unbelievably wonderful to me!!!!!!!!!     

Warm, full, round, 3D, top end chime, got every thing I like in a lectric' guitar sound.

When he turns the amp up it seems that the mic. is overloading?


                   Brad     

 

[Colas LeGrippa]

yeah, Brad,  seems like something is overloaded ( like me sometimes, but this is another story ).

I guess the tone has something to do with the guitar as well, a custom shop Tele. I 'll try it with my 335 CS Alvin Lee model first and see what the beast says to me..........

Colas

[tubenit]

Guys,   

Check this out.  It's one of my favorite amp tones and has some strong similarities to the 5F6-A Bassman.  Compare the two schematics.
The ManZamp seems to be sort of a Tweed Bassman / Dumble hybrid to my ears.

https://www.youtube.com/watch?v=jRGgZZ7jjkk

https://www.youtube.com/watch?v=FGUPyKYz3Xo

A guy on AmpGarage named "ic-racer" tried to reproduce a Dumble amp from a photo.  I think the tone of the amp is quite amazing to me.
He has a handful of videos on this amp on YouTube.

This clean tone is about as close to an ideal tone to me that I've heard.

I am convinced there is something about a 4X10 or 4X12 cab that adds a dimensional 3-D tone for some reason.

With respect, Tubenit

[Colas LeGrippa]

awesome !!!!!!!!!

The two circuits are almost identical. 
One question :  why there is no grid stoppers on the power tubes ? ( both circuits, while all the Marshall amps do have them ) )  Is the small 47p cap  accross the LTP plates replaces them ?

Colas

[Colas LeGrippa]

...........and have you noticed the choke in series with the capaciotor, at the preamp's tube cathode ? I wonder if it makes any change in tone

[tubenit]

Yeah, it is surprising that there are no grid stoppers.  Not sure why that is the case, and I would be inclined to put something there as a grid stopper?  Having said that, the amps sound great without them to my ears.

Yes,  that "choke" in conjunction with other components on the V1 cathode is reported to be a major player in the tone factor of the ManZamp per ic-racer on TAG.

IF someone would give me an amp that I had to keep & play (and could not sell to get the money out of it), ....... I probably would pick that ManZamp above a Dumble or anything else.  After listening to all the YouTube videos I could find of the ManZamp ......... I think it's a beautiful sounding amp and very transparent and articulate in tone.

http://www.youtube.com/watch?v=PbLJk2dhFPo#

With respect, Tubenit

[Colas LeGrippa]

You think grid stoppers would affect the tone ? I thought they had nothing to do with it and where in there only to stop oscillation. Maybe the 47p accrooss the PI plates do stop possible oscillation, and preferred to 2 grid stoppers because cheaper to install, what do you think ?

[tubenit]

I can't imagine something like a 1.5k to 5.6k grid stopper impacting the tone to any significant degree. I would think the good tone would still be there if using grid stoppers.

I am not a big fan of the 47p snubber cap across the plates.  When I've tried it (even with as low as 10p), it was a tone killer to me and made the amp sound like I put a thick sheet over the speaker cab. 

I think both grid stoppers and snubber caps help lessen oscillation.

With respect, Tubenit

[Ed_Chambley]

what speakers would you put in there? I personnally would put 4 X Eminence legend 10'' , but what'd be your choice ?

Thanks, you're my man.

Colas.

I use Weber 12A125, 20 watt with no dope if I want that 4 speaker 3D vintage tone as in the video if the original Bassman.  I really like them as they are light and 4 ceramic speakers get heavy fast.

I have a Tweed Bassman LTD that I replaced the board in with a handwired.  They sell for about $200 when the board goes south and they already have everything you need except a nice handwired board.

My bassman preference is the 6G6B, but I do like the tweed.

[Colas LeGrippa]

Just finished to build the BASSMAN .........sounds VERY good,  even with the SS rectifier. All voltages are pretty much identical to the Fender schems. Other difference: first tube,  having sold my last 12AY7, I put a 12ax7 instead.  I had a couple of MOJO TONE coupling caps that I used. The other ones are orange drops. I plugged in a pair of 5881 biased at 41mA, with plate voltage at 420. Probably my best amp  ! My friend is gonna like it a lot. THANK YOU GUYS, I LOVE YOU !!!!!!!!!!

Colas LeGrippa

[Willabe]

Wow, your a fast little bugger.     


                  Brad     

[Colas LeGrippa]

I know I am.    It took me 5 days, part time, but I used a chassis with all the tube sockets already fitted in. ( the head only, I did not build the cab with tolex and everything, c'mon ). The only bug I had is a very common one: the 2 plate wires inverted at the output tubes. That's it. No hum, no oscillation. I am an expert now. I wish I could post a sound clip here. I don't have the necessary equipment to record a good quality clip. I can really assemble an amplifier fast, here's how:  I do never use breadboard or other time consuming  ( and hum inducing ) devices. I keep it simple:  I solder all the component to the sockets and pots, using one or two terminal strips where needed. Less is more.

Colas

[sluckey]

We would love to see some pics of your build, especially since it's true point to point. We don't get to see much of that these days.

[tubenit]

Probably my best amp  ! My friend is gonna like it a lot

WOW!  About about that!  That's fantastic.  Amazing that you got it done so quickly. 

Would absolutely love to hear a sound clip of your playing thru that amp.  I am a HUGE fan of your guitar work.

Best regards and with respect, Tubenit

[labb]

Just to throw this in: I built a 5F6-A for my son with a few little mods.  Uses 6L6's instead of the 5881 for one thing. I built it as a head and then built a cab with a weber 15" speaker. Easier to move around as a head config.  I also built a 6G15 reverb unit to go with it..Patting my self on the back---this setup sounds really good.

[Colas LeGrippa]

thank you Jeff, you're a bro.


In fact, assembling a 50W head is fast depending on how clean you desire the layout to be. Using a breadboard and passing the HV and other leads under and through the holes , paying attention to do it correctly is time consuming. Soldering components right onto jacks, sockets and pots is way faster and more: it permits knowing instantly what is what. I must admit the look of such a circuit is not terrific, but we're talking here about a sound device, not a picture. It is very important though, just like in a breadboard design, to follow certain rules that will avoid more time consuming de-bugging problems, once come the time of switching the amp on. By example, it is extremely important to solder the coupling caps as close possible to their destination, not to the HV side ( e.g. right onto the power tubes, never on the PI ). Good lead dress is the secret, and if you can take time to run the wires neatly ( thing that I wish I'd  do ) , it is even better. I will take pics when I 'll re-open the amp, to swap the SS rectifier to a GZ34.


Cheers ! I love you all.


Colas