fender Bassman 50 to #102 Robben Ford Dumble amp

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Baddog01
Posts: 179
Joined: Sat Sep 21, 2013 8:04 pm

fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Baddog01 »

Hi Guys, Its been a while since ive posted here but im hoping you guys can help me along with my project when I need it. I got the schematic from this topic http://ampgarage.com/forum/viewtopic.php?t=12873 and it sounds pretty good. Here is what Ive done to the amp so far with the parts I had at hand. I added the O/D section and put the controls on the back. The trim pot at the input of the O/D section was replaced with resistors. Added the M/V and Presence control to the back panel. The normal channel is stock but the bass channel has been modded ( hot Rod mod )for a little more gain. I installed a Dumble style Deep switch with a double treble switch on the back panel. I'm thinking of changing the bass channel to the Robben Ford preamp setup. I'm not sure if I have enough room for all the switches.

I really like how I can get some cool tones out of the amp. Cleans are pretty good and the O/D is really adjustable and fun to tweak. I need to tighten up the bass a bit. I didn't have any 5uf electrolytics fro the cathode bypass caps so I used 25uf for now, I need to make a parts list for the preamp section I guess and see what I can find for switches.

Thanks
Keith
Last edited by Baddog01 on Sat Mar 28, 2015 7:46 pm, edited 3 times in total.
Teleguy61
Posts: 1000
Joined: Sun Mar 07, 2010 7:26 pm
Location: Eastern Mass USA

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Teleguy61 »

Welcome bd, glad you made it over here.
This is the place for d questions.
Baddog01
Posts: 179
Joined: Sat Sep 21, 2013 8:04 pm

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Baddog01 »

I finally have the confidence to dig into a dumble type mod. This is " the dumble " forum for sure. Glad to be here:)
Teleguy61
Posts: 1000
Joined: Sun Mar 07, 2010 7:26 pm
Location: Eastern Mass USA

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Teleguy61 »

Persistent and determined use of the search function can answer almost all questions I have found.
Good luck and enjoy!
Baddog01
Posts: 179
Joined: Sat Sep 21, 2013 8:04 pm

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Baddog01 »

I have noticed that too. I can spend lots of time just reading abou build and mods. Very cool stuff
Baddog01
Posts: 179
Joined: Sat Sep 21, 2013 8:04 pm

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Baddog01 »

Does robben ford use a 12at7 in the phase inverter?
Baddog01
Posts: 179
Joined: Sat Sep 21, 2013 8:04 pm

Dumble

Post by Baddog01 »

I finally got the bassman converted to a Robben Ford Dumble clone. Of course this is a 50watt head version and I didn't use the exact components as in the original. I don't have the money to go for an exact clone so this is going to have to do. I have a couple questions.

1. I noticed that the OD channel seems a little Buzzy. Would a treble bleed help in this section? What and where would I put it?

2. Is coupling cap direction a big thing and if so how do I determine the direction? How do I test the caps to find the correct direction.

Thanks
Keith
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drew
Posts: 720
Joined: Wed Jun 21, 2006 2:49 am

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by drew »

You can refer to this thread for an illustration of the "correct" directions: http://ampgarage.com/forum/viewtopic.php?t=24654
Baddog01
Posts: 179
Joined: Sat Sep 21, 2013 8:04 pm

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Baddog01 »

Perfect

Thanks
Keith
Baddog01
Posts: 179
Joined: Sat Sep 21, 2013 8:04 pm

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Baddog01 »

Drew,

I tested the caps and installed them according to the pic you sent me to. I did notice a difference in the noise level in the amp.
I also noticed that the Grid Stop resistors for the power tubes are 5.1k. This value seems more of a el34 type setup. Since I'm running 6l6's should I have 1.5k grid stop resistors instead of 5.1k?
Are all the smaller value caps in the RF amp silver mica or are some ceramic disc???

I know I'm just a hack compared to the guys here. I do appreciate any advice and help I can get and receive.

Thanks for the help
Keith
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drew
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Joined: Wed Jun 21, 2006 2:49 am

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by drew »

Keith - send Structo the moderator a PM and ask him to move this thread to the Dumble Discussion forum. It'll get more views that way.
Baddog01
Posts: 179
Joined: Sat Sep 21, 2013 8:04 pm

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Baddog01 »

Thanks
Baddog01
Posts: 179
Joined: Sat Sep 21, 2013 8:04 pm

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Baddog01 »

Removed the rock/jazz setup and used the switch as a treble cut for the OD section.
Baddog01
Posts: 179
Joined: Sat Sep 21, 2013 8:04 pm

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Baddog01 »

Played the amp some more last night and I'm really starting to dig the sound. Sounds good with the strat and tele but it shines with the Les Paul. Nice and punchy with nice highs and focused mid's. I need to do more time before I can let it sit. I have some Weber Neo 12's sitting here. They don't have the chrome dust covers so the highs don't get to ice picky. Do you guys think they would be a good fit with a dumble amp?

Thanks
Keith
Baddog01
Posts: 179
Joined: Sat Sep 21, 2013 8:04 pm

Re: fender Bassman 50 to #102 Robben Ford Dumble amp

Post by Baddog01 »

Teleguy61 wrote:Welcome bd, glad you made it over here.
This is the place for d questions.
Not a verry talkative group of people on this forum.hmm
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